Two Recent Review Papers on the Aging of Blood Vessels

Today I'll point out a couple of recently published open access papers that discuss aspects of arterial aging. The age-related decline of blood vessel structure and function is one of the more important aspects of aging, given that it is at present a largely one-way road to cardiovascular disease and death. Despite the efforts of the research community over past decades, which have included the noteworthy success story of statins, and an ongoing reduction in cardiovascular mortality rates, this remains the principal cause of age-related death in humans. To a first approximation, old humans die when the heart or blood vessels fail. The many other age-related causes of death taken together make up a minority of overall late-life mortality.

Perhaps the most important aspect of blood vessel aging is loss of elasticity. The stiffening of major blood vessels is enough on its own to break the feedback mechanisms that control blood pressure, causing progressively worsening hypertension. Increased blood pressure causes the heart to become larger and weaker, and also increases the rate at which pressure-related damage and blood vessel rupture occurs in more delicate tissues. Stiffening of blood vessels is probably primarily caused by cross-linking in the extracellular matrix, but evidence suggests that senescent cell accumulation and the inflammation generated by these cells also plays a role. These errant cells promote calcification in blood vessel walls, which can also contribute to loss of elasticity. There are also other mechanisms to consider, such as disruption of the normal processes by which blood vessel smooth muscle controls dilation and constriction of blood vessels - separately from stiffening, that can produce similar problems in regulation of blood pressure.

Rising blood pressure on its own is bad, and will ultimately cause death via heart failure. This is made much worse, however, by the progression of atherosclerosis. This is the generation of fatty deposits that narrow and weaken blood vessel walls: high blood pressure plus weakened blood vessels is a recipe for a fatal rupture. Even without that, the fat deposits become unstable and can break off inside the blood vessel to produce a fatal blockage, a process that again is accelerated by higher blood pressure. Atherosclerosis is the result of an unfortunate inflammatory feedback loop. Lipids become oxidatively damaged in ever greater amounts with advancing age, enter the bloodstream, and then irritate the blood vessel walls. Cells respond with an inflammatory response that draws in macrophages to clean up the unwanted lipids, but the macrophages can become overwhelmed and die. That in turn creates debris that calls in more macrophages, generates a larger inflammatory response, and makes the problem worse. The atherosclerotic plaques in aged blood vessels are inflamed graveyards of countless cells, surrounded by ever more cells in the process of adding their corpses to the mass.

In the SENS rejuvenation research viewpoint, all of these problems can be addressed with suitable forms of repair, granting natural repair processes enough breathing room to fix the remainder. Cross-links can be removed via suitable cross-link breakers, pharmaceuticals current in the early stages of development in programs such as that running at the Spiegel Lab at Yale. Senescent cells can be cleared out via senolytic therapies, presently under development by a number of companies. The various forms of damaged lipid, such as 7-ketocholesterol, can be identified and small molecule drugs developed to safely break them down. Many of the errant macrophages crowding around plaques can be targeted and removed to stop them making matters worse, as they have become senescent and can be targeted with senolytics. All of these are plausible near future treatments.

The Aging Risk and Atherosclerosis: A Fresh Look at Arterial Homeostasis

Atherosclerosis is the most significant human health problem globally. We know today that the disease does not follow a simple, unidirectional progression, and is determined by a myriad of pathways, control mechanisms, and repair processes; these encompass multiple inflammatory molecules, bone marrow (BM)-derived progenitor cells, a range of immune cells such as specific monocyte subpopulations, genetic mutations, and epigenetic modifications among numerous other participants both known and those yet to be discovered. Ultimately, however, the clinical result for an immensely large number of individuals is the formation and growth of vascular lesions with the potential to rupture, leading to life-threatening conditions. It is imperative to continue to evolve technological strategies to both predict and detect the formation, progression, and clinical status of these atherosclerotic plaques, while additional details are elucidated regarding the process of disease progression.

One example of important progress has been made in the control of inflammation when inflammation is no longer promoting repair, but instead has taken a damaging role for the artery. It was recently reported that a monoclonal antibody against IL1-beta, when injected systemically to patient with cardiovascular disease and high inflammatory index, is capable of reducing risk for coronary events, even with already reduced lipids and had no further effect on lipid levels. The role of inflammation is increasingly established in the progression of arterial lesions, and it is useful to consider inflammation in the context of arterial homeostasis.

Arterial repair is triggered and controlled by molecules that belong to inflammatory pathways. However, as was hypothesized and subsequently demonstrated in an animal model, the progression of atherosclerotic inflammation is modulated by the presence or the absence of an efficient repair process. In the presence of BM vascular progenitor cells capable of arterial repair, the artery heals and inflammatory signals subside and vanish. However, reductions in the availability of BM-derived vascular progenitor cells occurring as a consequence of aging or genetic susceptibility (exhaustion or dysfunction) result in a lack of arterial healing.

These reductions can occur either because repair-capable cells are no longer produced effectively by the BM, because the produced cells have become dysfunctional, or a combination thereof. Consequently, inflammatory signals do not subside and vanish, and indeed are heightened to the point where they attract and support monocytes/macrophages and other immune competent cells that further enhance arterial injury. Hence, the maintenance of arterial homeostasis is a complex process that must balance injuries to the arterial wall, inflammatory processes required for triggering and supporting arterial repair, and the renewal of BM-derived vascular progenitor cells that are necessary for such repair.

The Role of MicroRNAs in Arterial Stiffness and Arterial Calcification

Arterial stiffness is a characteristic feature of normal arterial aging, but is also associated with accelerated cardiovascular disorders. Another age-related process is arterial calcification, which in turn is a known risk predictor that increases morbidity and mortality in cardiovascular diseases. MicroRNAs (miRNAs) are small non-coding RNAs that downregulate their target gene expression post-transcriptionally. They are widely studied in recent years and their role in cardiovascular dysfunction is to some extent revealed. Identification of over- or underproduction of miRNAs could be therapeutic targets for prevention and treatment of vascular diseases.

Arterial stiffness results from complicated interactions between multiple components of the vessel wall, including extracellular matrix (ECM) composition, vascular smooth muscle cell (VSMC), and endothelial dysfunction. Collagen and elastin are the most important structural proteins of ECM and key regulators of arterial stiffness as they are responsible for blood vessels' strength and elasticity. Reconstruction of ECM, notably increased levels of aberrant types of collagen and reduction of elastin, appears to be the most important mechanism contributing to arterial stiffness. Matrix metalloproteases (MMPs) are endopeptidases which degrade all kinds of ECM proteins. Thus they play a significant role in arterial stiffness via regulating collagen and elastin levels in ECM.

Moreover, advanced glycation end products (AGEs) contribute to arterial stiffness through cross-linking with ECM proteins, including collagen, which reduces vessel's flexibility. Furthermore, many hormones and cytokines are involved in aortic stiffness, such as angiotensin II (Ang II) which promotes arterial stiffness through regulating signaling pathways that result in altered ECM accumulation and increased vascular tone. Apart from structural abnormalities, VSMC proliferation, migration and calcification, as well as impaired endothelium-dependent dilation through paracrine molecules such as nitric oxide (NO) and endothelin are, also, implicated in the development of arterial stiffness.

Extensive research during the last decade confirmed the association of miRNAs with cardiovascular diseases. MiRNAs seem to play a significant role in arterial stiffness and calcification through modulating critical pathways and molecules such as TGF-β and BMP signaling, Ang II, MMP activity, Runx, and phenotypic switch of VSMC. Thus, they may be used as therapeutic targets or diagnostic markers in the future to decrease arterial stiffness and prevent the development of cardiovascular diseases. However, it is more than obvious that the molecular biology and pathophysiology is very complex. Many miRNAs might have the same target gene (e.g., Runx2 is suppressed by miR-30b-c but enhanced by miR-32), while a single miRNA might exert multiple functions by targeting more than one genes and affecting different pathways with opposing results (e.g., miR-29, miR-19b and their role in fibrosis). Futhermore, miR-145, one of the most important miRNAs in cardiovascular pathophysiology, decreases arterial stiffness by inhibiting TGF-β signaling while, on the contrary, TGF-β activates miR-145 to promote the contractile phenotype of VSMCs and reduce arterial stiffness as well. Targeting TGF-b through miR-145 might have controversial results. To conclude, additional clinical and laboratory research should be continued for the establishment of miRNAs as treatment targets and biomarkers of cardiovascular diseases.

Yes, Of Course it is the Case that Life Expectancy at Birth Grew More Slowly in the Second Half of the 20th Century

To my eyes, the researchers here hold a few somewhat strange views of historical life expectancy data and its meaning, mixed in with the sensible thoughts, not least of which is their expectation of a ceiling or maximum to life span to exist. A great transition in trends for life expectancy at birth took place somewhere in the midst of the 20th century. In the early decades of the century, medical science made enormous inroads in the control of infectious disease, and then through to the middle of the century implementations of those advances fell in cost and spread out to less wealthy regions of the world. Infectious disease kills people of all ages, and thus large gains in life expectancy at birth can be achieved by cutting down mortality, especially in childhood. By the latter half of the century, the more tractable problems related to infectious disease were dealt with and solutions implemented to at least some degree for much of the world's population. Subsequent gains in life expectancy then had to emerge from tackling age-related diseases or the other, harder remainder of infectious disease.

To date, age-related disease has proven itself to be far less tractable a problem. As Aubrey de Grey puts it, the research community essentially took the same high level strategies that succeeded in achieving control over most infectious disease and tried to apply them to age-related disease. That simply won't work - these are two very different situations with very different causes, and which require very different solutions. The result has been marginal, expensive treatments that take a long time to produce, and thus progress towards increased life expectancy at birth has slowed. Firstly, the paradigm must change, towards something more like the SENS vision for rejuvenation through repair of the cell and tissue damage that causes aging. Secondly, life expectancy at birth is not a good metric for assessing progress towards the control of aging. Something more like remaining life expectancy at 60 is the number to pay attention to.

Increases in human life expectancy have slowed dramatically across the world since 1950, according to a new study. Although a "ceiling effect" is expected as average lifespan approaches its biological limit, the study found that the trend towards slower gains - and even declines - in lifespan is worst among low-lifespan countries. "This is not about us hitting the ceiling; the slowdown has been sharpest in countries that have the most life expectancy to gain. It's a rebuke to the idea that you can fix global health just by inventing more stuff. New health technology has been essential to making strides in life expectancy, of course, but our predecessors in the 1950s were making faster progress with the basics of soap, sanitation and public health."

Researchers examined life expectancy data for 139 countries and for each one calculated the "decadal" life expectancy gain - the gain from a given year to a decade later - during the period 1950-2009. The analysis revealed that for the total sample, the mean decadal gain started at an impressive 9.7 years during the 1950s but fell more or less steadily to just 1.9 years during the 2000s. The study did not break down data by country or region. The researchers stratified the countries in the sample by their life expectancies, and found that the highest lifespan countries, with life expectancies at birth of at least 71 years, declined from a mean decadal gain of 4.8 years in the 1950s to 2.4 years in 2000-2010. That result was unsurprising, given that life expectancies in these countries are approaching the maximum lifespan of 71-83 years.

However, the researchers found an even steeper decline in countries in the lowest stratum of lifespan, with life expectancies under 51 years. For countries in this category the mean decadal change in life expectancy dropped continuously from a promising gain of 7.4 years in the 1950s to a worrisome loss of 6.8 years in the 2000s. In other words, the low-lifespan countries on average went from experiencing big gains to sharp declines in life expectancy. The HIV/AIDS pandemic, which generally hit hardest in low-lifespan countries, is a factor in this trend but doesn't fully explain it. "The slowdown in life expectancy gains started before AIDS hit in the 1980s and 90s and occurred even in regions that did not have big problems with this disease." He suspects that an important driver of the overall trend is a widespread failure of governance. "Nowadays, the countries with persistently low life expectancy are countries that generally are fragile states."


Thoughts on Mechanisms Linking Body Temperature and Aging

A fair number of papers have been published on various aspects of the link between body temperature and pace of aging. Calorie restriction in mammals both slows aging and lowers body temperature, for example. Mice with lower body temperatures due to altered temperature regulation mechanisms in the hypothalamus live a little longer. Body temperature tends to fall with advancing age in mammals, and some unusually long-lived mammals stand out for having particularly low body temperatures. When it comes to looking at the mechanisms involved in these relationships, the cellular biochemistry is very complex, and most of the relevant research has been carried out in flies and nematode worms rather than in mammals - though noted here, researchers are working their way up to the identification of interesting mechanisms in mice.

In 1916, researchers demonstrated that lower temperatures could dramatically extend the lifespan of the fruit fly, Drosophila. Other poikilothermic animals, whose internal temperature varies considerably, including C. elegans, also present increased lifespan upon modest temperature reduction. Additionally, lowering the core body temperature of homeothermic animals, such as mice, also increases lifespan, highlighting a general role of temperature reduction in lifespan extension in both poikilotherms and homeotherms. Reduction in core body temperature has been proposed to mediate the longevity benefits of dietary restriction. Conversely, raising the culturing temperature (e.g., to 25°C) greatly shortens nematode lifespan.

How is the cold-dependent lifespan extension mediated? One prominent model assumes that lowering the body temperature would reduce the rate of chemical reactions, thereby leading to a slower pace of living. This model suggests that the extended lifespan observed at low temperatures is simply a passive thermodynamic process. However, a more attractive hypothesis suggests that specific genetic programs might be engaged to actively promote longevity at cold temperatures, as observed upon dietary restriction or other paradigms.

Researchers reasoned that a cold sensor of the TRP channel family might be recruited in this process. The best-known mammalian cold sensors are TRPA1 and TRPM8; however, TRPM8 does not have a C. elegans homolog, thus ruling this receptor out of the candidate-based approach. But, TRPA1 has one ortholog in C. elegans referred to as TRPA-1, which becomes active under 20°C and therefore constitutes an attractive candidate to mediate the longevity extension observed under cold temperature.

Three temperatures (15°C, 20°C, and 25°C) are common laboratory conditions for culturing worms. If TRPA-1 is involved in promoting longevity at low temperatures, one would expect that mutant worms lacking TRPA-1 should have a shorter lifespan at 15°C and 20°C than wild-type worms, but not at 25°C. This is because this cold-sensitive channel is expected to be functional at 15°C and 20°C but remains closed at 25°C. Consistent with this prediction, trpa-1 null mutant worms showed a significantly shorter lifespan than wild-type worms at 15°C and 20°C but not 25°C. Similarly, transgenic expression of TRPA-1 under its own promoter increased lifespan at 15°C and 20°C but not at 25°C.

The ability to affect aging by manipulation of TRP channels in invertebrate models such as C. elegans provides evidence for evolutionary conservation and argues for the investigation of homologous and analogous circuits in mammalian models. Recently, evidence of the conserved function of chemosensory neurons in the regulation of longevity has been provided through the study of the capsaicin receptor TRPV1.

Impairment of TRPV1 sensory receptors is sufficient to extend mouse lifespan and improve many aspects of health in aging mice. Under normal fed ad libitum conditions, the TRPV1 mutation is not sex specific in its effects: longevity in both genders was extended to a similar extent, with 11.9% increase in male TRPV1 mutants and 15.9% increase in median female lifespan compared to wild-type controls. The longevity increase observed in these animals is not due to previously established mouse longevity paradigms such as reduced growth hormone (GH) and/or insulin growth factor (IGF-1) signaling. TRPV1 mutants show no growth delay and do not differ in body composition compared to control animals. TRPV1 mutant mice also do not present core body temperature differences with controls, arguing that their long lifespan is not due to a dietary restriction mimetic mechanism. How can a mutation in a sensory TRPV result in increased lifespan? TRPV1 mutation results in enhanced insulin secretion with age and a youthful metabolic profile that leads to increased lifespan in mice.


Telomerase Gene Therapy Used to Cure Fibrosis in a Mouse Model

Maria Blasco's research group has been working on telomerase gene therapy to lengthen telomeres for some years now; they are quite enthusiastic about this approach as a means to treat aging. One can't argue with the data showing extension of mouse life span, nor the results announced today in which induced telomerase activity is shown to reverse fibrosis. We can argue about what is going on under the hood, and whether or not addressing telomere length is in fact tackling the root causes of aging. Perhaps the most important difference between the views of aging outlined in the SENS rejuvenation research proposals and the later Hallmarks of Aging is that the latter places telomere length front and center as being of importance. In the SENS view, telomere length is a secondary marker, a consequence of other forms of damage.

So how can a therapy that induces telomerase activity to lengthen telomeres, something that to my eyes doesn't address root causes of aging, produce significant impact on mouse longevity? Well, there are many proven ways to produce significant gains in mouse longevity that have nothing to do with repairing damage after the SENS model. Calorie restriction, for example, is exactly a slowing of aging, a slowdown of the accumulation of damage, and it produces a larger gain in life span than telomerase gene therapy in mice. It doesn't do that much for human life span, sadly, though it is certainly good for health.

As a general rule we should expect approaches based on manipulating the operation of metabolism to produce comparatively poor effects in humans. We should expect approaches based on repairing the root cause cell and tissue damage of aging to produce better results in humans. Judging from the data in mice obtained to date - let us say comparing senolytics to remove senescent cells, one of the root causes of aging, with telomerase gene therapy, and with calorie restriction - all of the methodologies produce results that are in the same broad ballpark in terms of life span gained, in the 20-60% range.

The next decade will settle the critical question of what a rejuvenation therapy can achieve for human life expectancy in older individuals. The data will primarily involve senolytic treatments, as those the only one ready to go into trials right now. We can then compare that data with what is known of calorie restriction in humans, which is to say little gain in life span, even while delivering measurable health benefits. But for now, the research community only has data for direct comparison in examples of what is thought to be the less effective way forward, slowing aging by the adjustment of metabolism. That data exists for calorie restriction and growth hormone receptor dysfunction only.

It is far from clear that one can lump telomase gene therapy into either the bucket holding calorie restriction (slowing aging) or the bucket holding senolytics (damage repair to reverse aging). It may need a bucket of its own, for approaches that force a reversal in a secondary or later issue in aging, while leaving the underlying damage to continue to fester. Naively, one might guess that this will be better than slowing aging, and worse than repairing root causes. But the data isn't there in humans, and the entire issue is enormously complicated by the fact that all of the methods examined to date are far less capable of extending life span for long-lived species such as our own - which may or may not be the case, or the case to the same degree, for repair-based approaches.

But let us consider what is going on in this study. The mice were given lung fibrosis via bleomycin treatment, a chemotherapeutic that causes lung inflammation. It is known that inflammation of lung tissue produces the disruption of regenerative processes that result in fibrosis, the inappropriate construction of scar-like connective tissue that degrades normal tissue function. Research of the past few years points squarely towards senescent cells and their inflammatory signaling as the primary cause of this issue. There is good evidence for the removal of senescent cells to turn back fibrosis. Toxic chemotherapeutics like bleomycin cause cells to become senescent, putting them under enough stress to trigger that irreversible state change.

In humans with lung fibrosis who exhibit shorter average telomere length, replicative senescence may be the more important source of lingering senescent cells. Senescence occurs in somatic cells when they reach the Hayflick limit, the end of a countdown in which each cell division results in shorter telomeres. Shorter average telomere length implies that stem cells are not keeping up with delivering fresh new cells with long telomeres, and this may produce all sorts of systematic changes in the function, inflammatory state, and signaling environment of a tissue.

So the question here is how telomerase induction helps this situation. The researchers believe their gene therapy vector preferentially targets lung cells, so we can probably put aside consideration of possible immune system effects, such as more energetic clearance of senescent cells. One possibility is that telomerase induction in senescent cells mutes the inflammatory, harmful signaling they produce, the senescence-associated secretory phenotype (SASP). Another possibility is that it pushes senescent cells into self-destruction, either directly, or perhaps indirectly through other changes to the overall signaling environment in the tissue, particularly the contributions made by stem cells. Past work has suggested that some of the benefits in mice given telomerase gene therapy are due to renewed, more youthful stem cell activity in tissue maintenance. Regardless, I think that, given other work on fibrosis and cellular senescence, one has to look at this with a focus on senescent cells.

Researchers cure lung fibrosis in mice with a gene therapy that lengthens telomeres

Idiopathic pulmonary fibrosis is a potentially lethal disease associated with the presence of critically short telomeres, currently lacking effective treatment. Researchers have succeeded in curing this disease in mice using a gene therapy that lengthens the telomeres. Telomeres are protein structures located at the ends of each chromosome; like caps, they protect the integrity of the chromosome when the cell divides. But telomeres only fulfill their protective function if they are long enough; when they shorten too much, the damaged cells cease to divide preventing tissue regeneration. Short telomeres are associated with ageing - as age increases, cells accumulate more divisions and more telomeric shortening - and also with several diseases. Pulmonary fibrosis is one of them.

In lung fibrosis, the lung tissue develops scars that cause a progressive loss of respiratory capacity. Environmental toxins play an important role in its origin, but it is known that there must also be telomeric damage for the disease to appear. Patients with pulmonary fibrosis have short telomeres whether the disease is hereditary - it runs into the family - or not. The most likely explanation is that when the telomeres become too short, the damaged cell activates a 'repair program' that induces scar formation that leads to fibrosis.

Researchers decided to address the problem about five years ago, starting with the development of an animal model that faithfully reproduces the human disease. The most widely used model until then was to apply bleomycin into the mouse lungs to induce damage, in an attempt to reproduce the environmental insult. However, in these animals the disease goes into remission in a few weeks and there is not telomere shortening. The researchers sought after a mouse model in which the environmental damage synergized to that produced by short telomeres, that is what happens in human pulmonary fibrosis. They succeeded in 2015.

The treatment consisted of introducing the telomerase gene into the lung cells using gene therapy. The researchers first modified a virus innocuous to humans (known as vectors) so that their genetic material incorporated the telomerase gene, and then injected those vectors into the animals. The basis of this work is the hypothesis that age-associated diseases can be treated by targeting the molecular and cellular processes of ageing, specifically telomere shortening. In 2012, the researchers generated mice that not only lived longer but also showed improved health by treating them with telomerase. Their work since then has aimed to develop this therapy to specifically treat age-associated diseases and telomere syndromes.

Therapeutic effects of telomerase in mice with pulmonary fibrosis induced by damage to the lungs and short telomeres

Pulmonary fibrosis is a fatal lung disease characterized by fibrotic foci and inflammatory infiltrates. Short telomeres can impair tissue regeneration and are found both in hereditary and sporadic cases. We show here that telomerase expression using AAV9 vectors shows therapeutic effects in a mouse model of pulmonary fibrosis owing to a low-dose bleomycin insult and short telomeres. AAV9 preferentially targets regenerative alveolar type II cells (ATII).

AAV9-Tert-treated mice show improved lung function and lower inflammation and fibrosis at 1-3 weeks after viral treatment, and improvement or disappearance of the fibrosis at 8 weeks after treatment. AAV9-Tert treatment leads to longer telomeres and increased proliferation of ATII cells, as well as lower DNA damage, apoptosis, and senescence. Transcriptome analysis of ATII cells confirms downregulation of fibrosis and inflammation pathways. We provide a proof-of-principle that telomerase activation may represent an effective treatment for pulmonary fibrosis provoked or associated with short telomeres.

Gbp1 Levels Fall with Age, Making Macrophages Less Helpful and More Harmful

Polarization is a categorization scheme for the cell state and behavior of the immune cells known as macrophages, which play a variety of roles in the body, ranging from the destruction of invaders and errant cells to assisting in regeneration. For the purposes of this discussion, the interesting states are M1, inflammatory and aggressive towards intruding pathogens, and M2, in which macrophages suppress inflammation and undertake other activities that aid in regeneration. Both have their roles to play, but many of the issues that arise in aged individuals are made worse by the increasing tendency of macrophages to exhibit the M1 polarization, even when it is unhelpful to do so.

While transient inflammation is a necessary part of the immune response, chronic inflammation (such as that produced by excess fat tissue or aging) is known to be disruptive to tissue maintenance and regeneration. This consideration of macrophages and inflammation is a thin slice of a much more complicated picture, but it is an important slice. While it is true that many other changes also take place in the aged immune system, here at least, researchers appear to have identified a regulatory protein that produces many of the problems exhibited by macrophages in older individuals. It will be interesting to see where the connections lead to from here, towards specific underlying forms of cell and tissue damage that cause aging. Note that the paper is as much focused on obesity as aging, but all of the relevant mechanisms examined appear in both circumstances.

Adipose tissue inflammation is a hallmark characteristic of obesity. Macrophages that infiltrate into adipose tissue and polarize to pro-inflammatory phenotype play a key role in obesity-associated adipose tissue inflammation and insulin resistance. Mechanistically, macrophages activated with the elevation of lipopolysaccharide (LPS) and IFNγ in obesity acquire an inflammatory M1 phenotype, characterized by increased production of pro-inflammatory cytokines and reactive oxygen species (ROS). These cytokines and ROS target adipocytes to further exacerbate adipose tissue inflammation and dysfunction.

Guanylate binding protein 1 (Gbp1) is a GTPase critical for innate immunity. This has been attributed to the role of Gbp1 in transporting autophagic machinery to the pathogen containing vacuoles (PCVs). Gbp1 expression can be largely induced by IFNγ in macrophages. Most previous studies primarily focused on the role of Gbp1 in regulating innate immunity of macrophages to defend against pathogen infections. Little is known about the involvement of Gbp1 in regulating polarization, metabolic programing, and cellular aging of macrophages.

In this study, we tested the hypothesis that Gbp1 plays a role in regulating immunometabolism and senescence of macrophages. We found that Gbp1 was mainly expressed in macrophages, but not adipocytes in response to IFNγ/LPS stimulation; Gbp1 expression was significantly decreased in inguinal white adipose tissue (iWAT) of high-fat diet (HFD)-fed and aged mice. We also observed that downregulation of Gbp1 in macrophages resulted in M1 polarization and impairment of mitochondrial respiratory function possibly via disrupting mitophagy activity. Moreover, macrophages with downregulated Gbp1 displayed dampened glycolysis and exhibited senescence-associated secretory phenotype (SASP). These observations suggest that Gbp1 may play an important role in protecting against mitochondrial dysfunction and preserving immune function of macrophages during aging.


Increased Sirt4 Modestly Increases Fly Lifespan

Researchers here show that increased levels of a mitochondrial sirtuin, sirt4, can modestly extend life in flies. Unfortunately, this sort of manipulation of metabolism - connected to nutrient sensing, mitochondrial activity, and calorie restriction - scales poorly as the life span of species increases. Short-lived species are comparatively sensitive to periodic lack of resources, and exhibit a sizable extension of life span in response to a lack of nutrients. This improves their prospects for current survival and then later reproduction when nutrients are once more available. Longer-lived species - such as our own - have for much of their evolutionary history enjoyed life spans far longer than any common period of famine, however. Thus we have a much smaller response to periods of reduced dietary nutrients, at least when considered in terms of additional healthy life, even though short-term measures of improved health are somewhat similar to those found in short-lived species.

"We show that Sirt4 is responsible for regulating both lifespan and metabolism in an organism, and specifically that it coordinates the metabolic response to fasting. We also demonstrate that overexpressing the gene for Sirt4 can extend lifespan of the fly." The results suggest that boosting Sirt4 activity may be an important avenue for treating age-related metabolic decline and disorders, such as diabetes and obesity, and promoting a healthy lifespan.

In the study, flies modified to produce extra Sirt4 saw their healthy lifespans extended by 20 percent. Removing the ability of flies to produce Sirt4 cut their healthy lives by 20 percent. Also, without Sirt4 in their cells, flies when removed from food died rapidly, even when nutrients and fats were still present in their bodies. Sirt4 belongs to a class of proteins, called sirtuins, known to regulate aspects of longevity, metabolism, genome stability, diabetes and neurodegeneration. Sirt4 is found in mitochondria, which are cellular structures where respiration and energy production take place.

Human cells contain seven different sirtuins, including three mitochondrial sirtuins, Sirt3, Sirt4 and Sirt5. Fruit fly cells contain just one mitochondrial sirtuin, Sirt 4. Increasing or decreasing expression of Sirt4 in living flies allowed the researchers to discover what function Sirt4 played in the insects - and possibly in humans. "We show for the first time that increasing the activity of a mitochondrial sirtuin can extend lifespan. No previous research has found that increasing the activity of a mitochondrial sirtuin such as Sirt4 extends the healthy lifespan of a living organism."

The study also shows Sirt4 may be a gene responsible for the metabolic action of fasting, particularly the gene vital to regulating when an organism switches from carbs to fat. A creature that lacks the gene starves to death much more rapidly than normal under poor nutritional conditions. Without Sirt4, the fly cannot access many of the nutrients and stored fats when fasting. Researchers know that temporary fasting in a living organism is valuable in resetting its metabolism. Such findings gave rise to what are called "near-starvation" diets to improve health and extend lifespan. But scientists don't know how that fasting-to-reverse-aging mechanism works. Sirtuins likely play a role. "We want to understand more about the role of sirtuins and their involvement in pathways of calorie restriction."


The Pineapple Fund Donates Millions to the Organ Preservation Alliance and Methuselah Foundation

The anonymous principal of the Pineapple Fund is a long-term holder of bitcoins, one of a number of people who have achieved considerable wealth in this way. Unlike most of the others, this individual holds the - eminently sensible - viewpoint that, after a certain point, the only real use for wealth is to craft a better world. Since the human condition, society included, is determined by technology, crafting a better world largely means supporting the development of new technologies that will allow us to overcome sources of suffering and limitation. In this context, by far the greatest cause of suffering and death in the world is aging.

One of the first donations made by the Pineapple Fund was a $1 million gift to the SENS Research Foundation, to accelerate ongoing work needed for the development of rejuvenation therapies based on periodic repair of the cell and tissue damage that causes aging. Another $1 million was added a little later. More recently, the Pineapple Fund has now given $2 million to the Organ Preservation Alliance and $1 million to the Methuselah Foundation, both deserving organizations in the same network, focused on advancing the state of medical research to help address the causes and consequences of aging.

The Methuselah Foundation should need little introduction for the audience here. It was the original home for the first SENS rejuvenation research projects, back when the budget was tiny and obtaining a five figure donation for the cause was a very big deal. The Methuselah Foundation has since generated the New Organ network of groups and researchers focused on tissue engineering, with the production of whole organs as a goal. Over the years, the foundation has invested in and incubated a number of startup companies such as Organovo (tissue printing), Oisin Biotechnologies (senescent cell clearance), and Leucadia Therapeutics (addressing protein aggregates in the brain). Those efforts have given rise to the Methuselah Fund, now that ever more venture funding is showing interest in the field. The Methuselah Foundation has less of a vocal public face than the SENS Research Foundation, but if you look at any of the activities and initiatives that take place in the broader rejuvenation research community, you'll usually find the Methuselah Foundation is connected in some way, behind the scenes. They play an important role.

The Organ Preservation Alliance is one of the more influential parts of the aforementioned network of groups focused on accelerating progress towards tissue engineered whole organs. Their specific area of interest is in the long-term preservation of large tissue sections. One of the important themes of recent years has been the meaningful signs of progress towards reversible cryopreservation, for example. If organs can be reliably vitrified and thawed with minimal damage, this will greatly simplify the logistics and reduce the costs inherent in both tissue engineering and the present organ donation industry. Being able to put an organ, donated or manufactured, into storage for the long term will change near everything about the way in which the field must presently operate. This isn't just important for the mainstream of medicine, however, as success in reversible cryopreservation will also provide considerable support for the cryonics industry, which is both vital and neglected.

The actions of the Pineapple Fund principal appear to be inspiring others in the cryptocurrency community to make donations of their own, and that, I think, is a useful outcome to see spreading through any community of high net worth individuals - or indeed, any community at all. The worst thing that one can do with wealth is nothing. There are any number of ways in which the world might be improved given a sensible approach to philanthropy, guided by personal principles of what is and is not important.

The Infectious Dose of Cytomegalovirus Determines the Degree of Resulting Age-Related Immune Dysfunction

Here researchers show that, in mice at least, a greater infectious dose of cytomegalovirus (CMV) causes a larger degree of age-related immune dysfunction. This is a useful paper that might go some way to answering one class of objection to the existing data on the contribution of CMV to immune system aging, in that not everyone who shows the markers of infection is impacted to the same degree. It seems that the level of exposure may be an important factor. The evidence for CMV to be a major issue for immune health is quite compelling: near everyone is infected by the time they are old; the immune system cannot effectively clear CMV; older people are characterized by a rapid increase in the proportion of immune cells uselessly specialized to CMV, and thus unable to contribute to any of the other responsibilities of the immune system.

The best way forward towards effective therapies is probably some form of targeted destruction of these cells, perhaps augmented by a cell therapy to deliver fresh immune cells to renew the defenses more rapidly than would otherwise be the case. There are groups working on vaccines or other medical approaches to clearing CMV, but my impression has been that this won't really help older people who are already greatly impacted: the degraded state of the immune system will remain, and must still be addressed separately. The researchers here think that clearing out the virus may be useful enough to try, however. The question is always the size of the resulting benefit, and it is unlikely that any method other than trying it out will give an acceptably robust answer in an acceptably short period of time.

The relationship between human cytomegalovirus (HCMV) infections and accelerated immune senescence is controversial. Whereas some studies reported a CMV-associated impaired capacity to control heterologous infections at old age, other studies could not confirm this. We hypothesized that these discrepancies might relate to the variability in the infectious dose of CMV occurring in real life. Here, we investigated the influence of persistent CMV infection on immune perturbations and specifically addressed the role of the infectious dose on the contribution of CMV to accelerated immune senescence.

We show in experimental mouse models that the degree of mouse CMV (MCMV)-specific memory CD8+ T cell accumulation and the phenotypic T cell profile are directly influenced by the infectious dose, and data on HCMV-specific T cells indicate a similar connection. Detailed cluster analysis of the memory CD8+ T cell development showed that high-dose infection causes a differentiation pathway that progresses faster throughout the life span of the host, suggesting a virus-host balance that is influenced by aging and infectious dose.

Importantly, short-term MCMV infection in adult mice is not disadvantageous for heterologous superinfection with lymphocytic choriomeningitis virus (LCMV). However, following long-term CMV infection the strength of the CD8+ T cell immunity to LCMV superinfection was affected by the initial CMV infectious dose, wherein a high infectious dose was found to be a prerequisite for impaired heterologous immunity. Altogether our results underscore the importance of stratification based on the size and differentiation of the CMV-specific memory T cell pools for the impact on immune senescence, and indicate that reduction of the latent/lytic viral load can be beneficial to diminish CMV-associated immune senescence.


Senescent Cells Contribute to Vascular Dysfunction and the Biochemistry of Alzheimer's Disease

Researchers here make an effort to link the age-related accumulation of senescent cells in vascular tissue with some of the better known biochemistry of Alzheimer's disease. Progressive vascular dysfunction is an important component of aging: loss of elasticity; failure to regulate blood pressure; failing constriction and dilation; the the corrosive growth of fatty atherosclerotic plaques that weaken and narrow blood vessels; increased amyloid deposition in blood vessel walls. In the brain particularly, failure to deliver sufficient oxygen and nutrients via the vascular system is a notable contributing factor in the onset of dementia, and a sizable fraction of Alzheimer's patients also exhibit full-blown vascular dementia.

Recent studies have suggested that senescent cells have a larger role in vascular aging than was previously assumed, contributing to most of the line items noted above, and this open access paper continues that theme. One of the more interesting points of focus here is the generation of amyloid-β, a protein that accumulates in Alzheimer's disease, in the vascular system, both inside and outside the brain. This appears to take place to a greater degree in senescent cells. It will be a most interesting new direction for Alzheimer's research should further investigations find that senescent cells are a significant source of amyloid. Given the low cost of senolytic drug candidates, someone should set up an exploratory trial.

Epidemiological, experimental, and clinical studies have suggested that age-related cerebrovascular dysfunction plays a critical role in the pathogenesis of dementia, including Alzheimer's disease (AD). Amyloid β (Aβ), the main constituent of amyloid plaques and a key pathogenic factor in AD, has detrimental effects on cerebral blood vessels resulting in disruption of homeostatic function of the cerebrovascular endothelial cells. The present study was designed to determine the effects of senescence and angiotensin II (Ang II) on expression and processing of amyloid precursor protein (APP) in human brain microvascular endothelial cells (BMECs).

Cellular senescence is an important contributor to aging and age-related diseases. Prior studies provided evidence that processing of endogenous APP is down-regulated in senescent human fibroblasts, but the effects of senescence on APP expression and processing in vascular endothelium have not been studied. APP is highly expressed in endothelium and can be processed by two major proteolytic pathways. In the non-amyloidogenic pathway, APP is cleaved by α-secretase thereby generating soluble APPα (sAPPα), a well-known anticoagulant, neurotrophic, and neuroprotective molecule. In contrast, amyloidogenic processing of APP sequentially driven by β-site APP cleaving enzyme (BACE1) and γ-secretase generates cytotoxic Aβ. Under pathological conditions, β-processing of APP is activated therefore increasing production of Aβ. Importantly, inhibition of BACE1 could prevent or reduce the accumulation of Aβ in the brain, thereby reducing AD-related pathology. Not surprisingly, inhibitors of BACE1 are currently being developed for the treatment of AD.

Taken together, the results of the present study suggest that reduced APP expression contributes to down-regulation of sAPPα in senescent brain microvascular endothelium. Increased BACE1 expression and Aβ production suggest that senescence promotes β-processing of APP. Treatment with a BACE1 inhibitor is beneficial for senescent human BMECs. This effect is mediated by shifting of APP processing towards non-amyloidogenic pathway. The present study also reports a novel observation regarding the detrimental effects of Ang II on α-processing of APP by activation of AT2R in senescent human BMECs. Given the fact that the cleavage products of APP play an important role in vascular homeostasis, we propose that increased Aβ production together with loss of sAPPα are previously unrecognized mechanisms of cerebral microvascular endothelial dysfunction induced by senescence and Ang II. Our findings support the concept that pathological expression and processing of APP in senescent cerebrovascular endothelium may play an important role in pathogenesis of cerebral amyloid angiopathy and AD.


Negligible Senescence and Exceptional Genome Maintenance in Naked Mole-Rats

Studies of the comparative biology of aging involve mapping the genetics and cellular biochemistry of exceptionally long-lived species in search of significant differences, when compared with both humans and shorter-lived species. The hope is that findings may inform human medical research, and at best could lead to new directions for the development of therapies to address aspects of aging. Species of interest include whales, for longevity and exceptional cancer resistance given their size, elephants, also for unusual cancer resistance, and naked mole-rats, which live far longer than similarly sized rodent species, and are near immune to cancer.

Today I'll point out a couple of recent papers from research groups investigating the naked mole-rat. It has for a while now been generally accepted that naked mole-rats are negligibly senescent. This is a blanket and in practice fairly loosely applied term indicating that members of a species show little signs of aging across most of a life span (for some definition of "little" and "most"), with a sudden and short decline at the end. This is very unlike the human life course, which takes the form of an exponential decline that starts comparatively early, in the middle of life.

Aging in this context has a precise definition: it is the rise in mortality rate over time due to intrinsic causes, the accumulation of cell and tissue damage resulting from the normal operation of cellular metabolism. If mortality rate remains roughly static over time in a population, then its individuals are not aging - which can in principle be the case at any mortality rate, high or low, but agelessness coupled with a high mortality rate seems more of a curiosity than a useful phenomenon, where it does occur. The naked mole-rats exhibit the low mortality option, of course. The first paper below provides evidence to back up the assertion that naked mole-rats don't just seem negligibly senescent, but actually are negligibly senescent.

The second paper looks at stochastic mutation rates across the life span, one of the many areas of biochemistry that researchers believe is important to aging. Mutation incidence is also a determinant of cancer risk - cancer is a numbers game, with every mutation that occurs having a tiny chance to be of a type that can give rise to an unrestrained, cancerous cell. Everything connected to aging looks better in a naked mole-rat, and that includes low mutation rates and highly effective DNA repair. Clearly some of those measures are secondary to the root cause reasons as to why the species ages so lightly until the very end of life - they can't all be root causes.

DNA maintenance may fall into either category, though the present consensus places it a meaningful contributor to the declines of aging. However, it remains the case that definitively determining the relative importance of specific contributions to the outcomes of aging is a challenge. These questions will probably remain open until biotechnology is applied to block or eliminate various likely mechanisms in naked mole-rats, or recreate those same mechanisms in mice, in order to observe the outcome. Theorizing and mapping can only take us so far at the present time.

Naked mole-rat mortality rates defy Gompertzian laws by not increasing with age

The naked mole-rat is a strictly subterranean, mouse-sized rodent and is one of only two known eusocial mammals. The longest-lived rodent, it is recognized as an animal model of biogerontological interest, with a maximal lifespan of more than 30 years in our captive care. This maximum lifespan is five-fold greater than predicted allometrically for a 40g rodent. Beyond lifespan, the physiological declines that accompany advancing age in most mammals fail to manifest in naked mole-rats. Breeding females show no menopause, retaining high fertility even at ages past 30 years. Neurogenesis is also prolonged and may continue for at least two decades, and over a similar time course, no significant changes in cardiac function, body composition, bone quality, and metabolism are evident. Age-associated chronic diseases such as cancer are also rare. Within the cell, proteasome function, as well as mitochondrial mass, gene expression, and protein expression are maintained with age.

The concepts of mortality and physiological decline associated with aging can be connected within the mathematical framework of the Gompertz-Makeham law of mortality. Mortality hazard increases exponentially with age, presumably due to intrinsic age-related physiological declines. While naked mole-rats are already noted as exceptionally long-lived, this status relies on small-sample-based estimates, leaving much uncertainty as to how exceptional their longevity may truly be and how they differ from other mammals with respect to the Gompertz-Makeham aging framework. Here, we compiled a large, historical dataset of naked mole-rat lifespans using records kept throughout the ~35 year maintenance of our collection. With over 3000 data points, we constructed survival curves and performed analyses of age-specific hazard. In these analyses, this mouse-sized rodent exhibited no increase in mortality hazard, that is, no Gompertzian aging, across its full, as-yet-observed, multi-decade lifespan. This life-history trend is unprecedented for mammals.

Genome Stability Maintenance in Naked Mole-Rat

DNA damage caused by environmental stress and normal metabolic processes occur daily at a frequency raging from 1,000 to 1 x 10^6 per living cell. As a result, only 0.00017% of the human genome consisting of 3 x 10^9 base pairs is damaged, but lesions in essential genes, such as the genes that code for tumor-suppressor proteins, can significantly disturb cellular function. The efficient DNA repair mechanisms that counteract DNA damage accumulation substantially contribute to genome stability maintenance, which is one of the crucial cellular functions. Accumulation of DNA lesions and mutations increases the risk of cancer and is related to aging.

Only a few experimental studies have focused on the search for a correlation between the activity of DNA repair systems and maximum lifespan. The complexity of these studies and their controversial findings may stem from both the imperfect methods used for activity assessment and improper selection of model systems. The naked mole-rat (NMR) is one of the most promising models used to study genome maintenance systems, including effective repair of DNA damage. The lifespan of the NMR can reach 32 years, ten times longer than that of the mouse. For most of its lifespan (at least 80%), this animal shows no signs of aging and retains the ability to reproduce. It possesses a very efficient mechanism of resistance to cancer, including cancer induced by different stressors.

The naked mole-rat draws the heightened attention of researchers who study the molecular basis of lengthy lifespan and cancer resistance. Despite the fact that the naked mole-rat lives under genotoxic stress conditions (oxidative, etc.), the main characteristics of its genome and proteome are a high stability and effective functioning. Replicative senescence in the somatic cells of naked mole-rats is missing, while an additional p53/pRb-dependent mechanism of early contact inhibition has been revealed in its fibroblasts, which controls cell proliferation and its mechanism of ARF-dependent aging. The unique traits of phenotypic and molecular adaptations found in the naked mole-rat speak to a high stability and effective functioning of the molecular machinery that counteract damage accumulation in its genome.

Fat Tissue Outside the Heart Plays a Role in the Progression of Heart Failure

Researchers here demonstrate the degree to which fat tissue is involved in the progression from hypertension to heart failure, achieving this result by finding a way to sabotage one of the linking mechanisms. Removing a specific gene, ATGL, greatly reduces heart failure in mouse models of the condition. ATGL appears to play an important mediating role in the way in which fat tissue produces altered lipid levels in an aged, dysfunctional heart, and those lipid changes in turn accelerate the decline into heart failure. The full paper is open access, and worth looking over if the topic interests you. It should go without saying that there is already a mountain of research to demonstrate that excess fat tissue is a bad thing: this adds one more item to that lengthy list.

Heart failure is a chronic disease that should not be underestimated. Between one and two thirds of patients with heart failure die of the disease within five years. While researching the molecular causes of heart failure and new ways to treat it, researchers found that changes in adipose (fat) tissue lipid metabolism affect disease development. "We were able to show that the lipid composition of the heart is altered by non-cardiac body fat, and that these changes are likely to affect heart function."

For some time, researchers have suspected that the impact of body fat on heart function also exists on a molecular level. One of the key processes involved is the release of fatty acids from adipose tissue. In order to gain a better understanding of this process, the researchers used an animal model, which allowed them to interfere with the lipid metabolism, and to knock out the gene responsible for the relevant enzyme, adipose triglyceride lipase (ATGL). This resulted in all treated mice developing near-complete protection against heart failure. As part of this study, the researchers also analyzed blood samples from patients with and without heart failure. Some aspects of the changes observed in the lipid composition of blood samples were comparable to those observed in the animal model.

The researchers are now planning to transfer these results into clinical practice. In doing so, they will be guided by one central question: how might a drug-based treatment target the gene responsible for the release of fatty acids and the enzyme ATGL, and how might it do so exclusively in adipose tissue? The researchers are also planning to conduct further analyses of patient samples to confirm their results, and are working to determine the role of adipose tissue in patients with heart failure within the clinical setting. "For patients, this means that we should be starting to pay greater attention to adipose tissue when making diagnostic and treatment decisions, even when our primary aim is to treat heart disease."


Stroke Risk Nearly Halved by Some Combinations of Medications to Lower Blood Pressure and Cholesterol

The data here gives a fairly good idea of the bounds of the possible and plausible when lowering blood pressure and blood cholesterol, putting some numbers to the degree to which stroke risk can be reduced. Strokes occur due to breakage or blockage of blood vessels, and the roots of that lie in (a) the stiffening of blood vessels that breaks the feedback mechanisms determining blood pressure, and (b) the processes of atherosclerosis that produce fatty plaques in blood vessel walls, narrowing and weakening them.

Blood pressure medications don't address the roots of the problem, but force a lower blood pressure, which reduces the risk of rupture in weakened vessels. Lowered blood cholesterol, such as via statins, or more modern and effective approaches such as PCSK9 inhibition, reduces the pace at which atherosclerosis progresses over time by reducing the amount of damaged cholesterol in the blood stream. Again, it achieves this result not by addressing the root causes of that damage, but through a blanket lowering that happens to include the problem cholesterol molecules that feed the growth of atherosclerotic plaques. Fortunately it appears that we humans don't need anywhere as much cholesterol as we have; it is interesting to speculate on why we seem to have at least ten times as much in our bloodstreams as we need to get by.

Combining medication that lowers blood pressure with medication that lowers cholesterol reduced first-time strokes by 44 percent. Seventy-five percent of strokes are first-time strokes. High blood pressure and high cholesterol both increase the risk for stroke, the fifth leading cause of death in America. Yet it's not known whether combining drugs that lower blood pressure and cholesterol levels can protect individuals from stroke. Now, a study involving 12,705 participants from 21 countries shows that individually, drugs that lower blood pressure or cholesterol do indeed reduce stroke risk, but when combined, they offer even greater protection.

Taking daily doses of two blood pressure drugs (fixed dose candesartan and hydrochlorothiazide) along with a cholesterol-lowering drug (low-dose rosuvastatin), proved to be the most effective, cutting first-time strokes by 44 percent among patients at intermediate risk for heart disease. For those with very high blood pressure - readings 143.5 mm Hg or higher - taking 16 milligrams of candesartan plus 12.5 milligrams of hydrochlorothiazide every day reduced stroke by 42 percent. Compared with a placebo, stroke was reduced by 30 percent among participants taking daily doses of 10 milligrams of rosuvastatin.

The findings come from the Heart Outcomes Prevention Evaluation Study, a large, international study focused on heart disease and stroke prevention. The average age of the participants was 66 years; 46 percent were women, and 166 strokes occurred during an average follow-up of 5.6 years. At the start of the study, the average blood pressure was 138/82 mm Hg. A normal blood pressure reading is around 120/80 mm Hg. Based on these findings, researchers are now looking at developing a single pill that produces the same effects as taking multiple pills that lower both blood pressure and cholesterol.


Delivery of Extracellular Vesicles as a Potential Basis for Therapies

Here I'll point out a readable open access review paper on the potential use of extracellular vesicles as a basis for therapy: harvested from, say, some form of stem cell, and then delivered to a patient. One of the ways in which stem cell therapies might branch and evolve in the near future is to discard the cells themselves in favor of the signals produced by those cells. The evidence to date strongly suggests that many of the current forms of cell therapy produce their beneficial effects, such as a reduction in inflammation, via signaling. The cells themselves do not survive for long enough in large enough numbers to be making a difference through other activities.

This is not to say that all cell therapies should be replaced by signals - in most of the cases relevant to human rejuvenation, it is vital to deliver cells that stick around, integrate with tissues, and perform all of the necessary tasks required of them. To augment a failing organ such as the heart that is not naturally regenerative to a great degree, for example, or replace age-related losses in a small but necessary cell population, such as the dopamine generating neurons lost in Parkinson's disease. The present state of biotechnology isn't all that good at achieving this goal of cell survival, unfortunately, but that will improve. So there may be two fields in the future where there is one today, the first focused on delivering cells, the second on delivering cell signals absent the cells. Both can be useful, though only the replacement of lost cells directly addresses a root cause of aging. If we are prepared to accept stem cell therapies as a worthwhile endeavor even if they only work through signaling and fail to address root causes of aging, then we should be as accepting of the delivery of signals alone.

What are extracellular vesicles? These are numerous different forms of membrane-wrapped package that are constructed and released by cells, containing all sorts of proteins and other molecules. Other cells take them up and their behavior adjusts based on the way in which the contents interact with internal cellular machinery. A rough taxonomy of vesicles exist, based on their size - exosomes versus microvesicles, for example. This will no doubt give way to a better taxonomy based on function, given further research. Currently, only a comparatively crude understanding exists of the specific functions that vesicles accomplish, and how that differs between types. So while it is possible to say that stem cells produce beneficial effects via vesicles, and senescent cells produce harmful effects via vesicles, it isn't yet possible to break down that flow of vesicles into its component parts and talk in detail about each part in isolation.

Extracellular vesicles and aging

It is estimated that in the next 20 years, the number of individuals in the United States over the age of 65 will double, numbering more than 70 million individuals. Unfortunately, as we age there is an unavoidable and progressive loss of the ability to maintain tissue homeostasis under stress and an attrition of functional reserve. Over 90% of individuals older than 65 years of age have at least one chronic disease, while more than 70% have at least two. These chronic diseases account for 75% of our healthcare costs, amounting to approximately $3 trillion in costs last year alone. Thus, there is a significant need to understand mechanisms driving aging and to develop novel therapeutics.

There is compelling evidence to support the hypothesis that the underlying cause of aging is the cell autonomous, time-dependent accumulation of stochastic damage to cells, organelles, and macromolecules. However, it is also clear from heterochronic parabiosis and serum transfer studies that cell non-autonomous mechanisms play important roles in suppressing or driving degenerative changes that arise as the consequence of spontaneous, stochastic damage. For example, using heterochronic parabiosis, it was demonstrated that factors in young blood rejuvenate certain cell types and tissues in old mice.

Conversely, factors in old blood can drive aging of certain cell types and tissues in young mice. These blood-borne pro-geronic factors include the chemokine CCL-11 and β-2 microglobulin. In addition to these identified geronic factors, it is likely there are other circulating factors that also play key, cell non-autonomous roles in aging. Indeed, it is likely a combination of loss of anti-geronic factors and an increase in pro-geronic factors that drives aging. Given that almost all cell types release extracellular vesicles (EVs), including stem/progenitor cells and senescent cells, it is likely that subsets of blood-borne EVs play key roles as both anti- and pro-geronic factors.

EVs are comprised of both microvesicles, released from the plasma membrane by shedding, and nanovesicles or exosomes, generated by reverse budding of multivesicular bodies (MVBs). Although their contents likely differ, both small and large EVs are enriched for a subset of diverse proteins, lipids, messenger RNAs (mRNAs), and non-coding RNAs (ncRNAs), such as miRNAs, which are derived from the parental cells. EVs have a variety of reported functions and some of their better-documented activities are associated with some form of immune regulation. EVs derived from stem cells also have significant ability to repair damaged tissue.

Consistent with the regenerative capacities of stem cell EVs, a recent study demonstrated that implantation of healthy hypothalamic stem/progenitor cells into the hypothalamus leads to the slowing of ageing. Moreover, it was demonstrated that the functional hypothalamic stem/progenitor cells release exosomes into the cerebral spinal fluid that likely contribute to slowing aging through transfer of miRNAs. Conversely, it has been demonstrated that senescent cells release more EVs and with a different composition, likely contributing to the senescence-associated secretory phenotype (SASP). These results suggest that functional stem/progenitor cell-derived EVs are able to extend healthspan and lifespan whereas senescent cell-derived EVs could function as pro-geronic factors. Taken together, there is substantial circumstantial evidence that EVs play key roles in aging and that regenerative EVs could be used to extend healthy aging. Finally, given the likely role of EVs in aging, components of EVs could be developed as biomarkers of unhealthy aging.

Considering Various Strategies to Treat the Issue of Mutated Mitochondrial DNA

Mitochondria, the power plants of the cell, are the evolved descendants of symbiotic bacteria. They still carry a remnant of the original bacterial DNA, encoding a few vital genes. That mitochondrial DNA becomes damaged in aging, and based on the various direct and indirect evidence for the size of the influence of mitochondria on life span, this mutational damage and its consequences are a big deal. Some way to revert mitochondrial DNA damage is high on the list of rejuvenation therapies that we would like to see developed in the years ahead.

The open access paper here is largely focused on the treatment of inherited mitochondrial conditions, in which a sizable fraction of mitochondrial DNA in every cell throughout the body is affected by the same specific harmful mutation. It is nonetheless is a useful tour of some of the available tools that researchers might consider adapting in order to attempt to reverse the mitochondrial damage that occurs in aging. It mentions allotopic expression (copying mitochondrial DNA into the cell nucleus as a backup) only briefly, but that is fine: the audience here is no doubt familiar with this favored strategy of the SENS research program, but possibly less familiar with the other options on the table that involve mitochondrial DNA.

Most of those options boil down to either (a) delivering or creating larger amounts of correct mitochondrial DNA or (b) destroying as much broken mitochondrial DNA as possible. Both are viable approaches for inherited mitochondrial disease, but the dynamics are different in the case of aging. The real challenge posed by the most harmful age-related mitochondrial DNA mutations is that they result in mitochondria that are both broken and able to replicate more effectively than their peers. So even a single copy can quickly replicate to take over a cell, and that places tough constraints on the ability to produce benefits through treatments that work through the methods noted above. Adding correct mitochondrial DNA seems non-viable in principle on its own, while methods of destroying broken mitochondrial DNA would have to be exceedingly efficient to make any lasting progress. Still, the latter may be worth testing in order to certain, given that the technology exists to make the attempt.

The human mitochondrial DNA (mtDNA) is a small double stranded circular genome which is maternally inherited. Each mammalian cell contains in average one thousand copies of mtDNA and each molecule contains 37 genes. Defects in the mtDNA, both point mutations and large scale rearrangements, have been associated with severe mitochondrial syndromes. When pathogenic mutations occur in the mtDNA most often both mutant and wild-type copies co-exist within the same cell, a phenomenon known as heteroplasmy, and, in general, only when the mutation load is higher than approximately 80% symptoms manifest.

Currently, there are no effective strategies to cure mitochondrial disease and, in spite of the advances in genetics and biotechnology, there are still some gaps in the understanding of mitochondrial genetics. For instance, we do not know what controls mtDNA copy number, and mechanisms of mtDNA replication are still controversial. During the past 16 years our lab and others have been focusing in the use of endonucleases to target mitochondria and induce double strand breaks (DSB) in the mtDNA. Taking advantage of the fact that mitochondria lack an established DSB repair mechanism, it has been shown that mtDNA is quickly degraded after a DSB. Therefore, heteroplasmy can be manipulated and the mutant genomes can be efficiently eliminated through cleavage of mutant mtDNA and repopulation of the cells with wild-type mtDNA. Recently, a new door has been open regarding translation of these techniques into the clinics by the development of precise DNA editing tools, which can be targeted to mitochondria to promote DSB in the mtDNA.

Because of the high rate of mutations in the mtDNA, new pathogenic mutations are recurrently introduced into the human population. Recently, next-generation sequencing technology has been used to identify and quantify mtDNA mutations. However, these techniques have a high intrinsic error rate when applied to detection of low-level heteroplasmy. Despite all the technological difficulties, it is believed that mtDNA heteroplasmy exists in almost every healthy individual studied, even though at very low levels. These heteroplasmic variants can also be passed down the maternal lineage, raising the possibility that some presumably somatic mutations measured late in life are actually low-level heteroplasmies that have been inherited and somehow clonally expanded.

In contrast to point mutations, primary mitochondrial rearrangements of mtDNA are not inheritable, they are sporadic. Large-scale deletions are typically heteroplasmic and result in disease. To date, roughly 120 different mtDNA deletions have been found in patients with mitochondrial disease. In this case, the heteroplasmic threshold is reported to be lower than the one for point mutations, the patients manifest the disease symptoms with as low as 50-60% heteroplasmic mtDNA levels. Two different models arise to explain deletions in the mtDNA, while one points to replication errors, the other one points to poor and inefficient mtDNA repair mechanisms.

The concept of shifting the balance between healthy and mutated mtDNA as a treatment for heteroplasmic mtDNA disease has been under investigation over the past 20 years. Many publications demonstrated that it is possible to manipulate the mtDNA and shift heteroplasmy, either in vitro or in vivo. By simply reducing the levels of the mutant allele below a certain threshold, an improvement in pathology is achieved. There are currently at least two strategies for applying gene therapy to patients with mtDNA diseases: 1) Allotopic expression of mitochondrial genes; 2) Manipulation of mtDNA heteroplasmy. Allotopic expression of mitochondrial genes which consists in the synthesis of a wild-type version of the mutated protein in the nuclear-cytosolic compartment followed by its import into mitochondria has been a controversial approach because of the high hydrophobicity of mtDNA-encoded proteins and the competition with endogenous counterparts. Nonetheless, clinical trials for Leber's optic neuropathy are currently ongoing. The use of mitochondrial endonucleases is still in its infancy, but hopefully will move into the clinics in the next few years.

To conclude, the manipulation of mtDNA heteroplasmy either by using mito restriction endonucleases, mito zinc-fingers or mitoTALENs could facilitate delivery and increase specificity of mtDNA editing, having the potential to eliminate mutant mitochondrial genomes from germline treated affected patients.


A Novel View of How Frail Bones Break

The common wisdom regarding the fractures and breaks that are sadly common in very old individuals is that they result from hard knocks against - and heavy loads placed on - bones that are made fragile by osteoporosis. A younger person would shrug off a fall or a load that will cause catastrophic structural failure in the bones of an individual in the advanced stages of osteoporosis. The research here suggests that this view is subtly wrong in several important details, and that the progressive harm caused by osteoporosis is in fact much worse than thought. It is an interesting and plausible viewpoint, though one that needs corroborating physiological data.

Either way, what can be done about osteoporosis? The proximate cause is an imbalance between the activities of cells that deposit bone, osteoblasts, and cells that break down bone, osteoclasts. Both are constantly active, but the various forms of change and damage that accompany aging cause the activity of osteoblasts to decline relative to the activity of osteoclasts, and thus bone becomes ever weaker. Senescent cell accumulation and chronic inflammation are in the list of deeper causes for osteoporosis, as is true of many other age-related conditions, but they are not alone. There numerous possible avenues by which this balance can be adjusted, and research groups are at various stages in these lines of work. If the balance is turned back, then the age-related weakness and damage of bone should start to reverse.

To better understand why many elderly people are prone to break a bone in a fall (known as bone fragility fractures), perhaps doctors and researchers should look at the human skeleton in much the same way civil engineers analyze buildings and bridges. A team of researchers believes the bones of an older person, say above the age of 50, become more susceptible to a break due to repeated stress from everyday activities such as walking, creating microdamage that affects the quality of the bone. That is in contrast to the common-held belief that bone breaks in the elderly are largely due to one massive impact or force on the bone, such as a fall.

"It really starts with a small microcrack that grows over time under repeated loading. You need to be doing something like just walking or moving, and the crack is slowly propagating. At some point, the remaining cross-section of the bone that is still connected is too small and will break suddenly." In that case, such fractures in the elderly would be the cause of a fall rather than the result of a fall. The theory that "cyclic loading" (repeated and fluctuating loads) might be a bigger contributor to bone breaks is similar to the study of structures and engineered materials. This type of stress in structures and materials resulted in a rise of catastrophic accidents near the turn of the 20th Century and has led to the development of "fracture mechanics."

"In engineered materials and structures, cyclic fatigue is the most ubiquitous mode of failure. Cyclic fatigue accounts for more than 80 percent of all failures, leading to catastrophic and sudden accidents such as the failure of railway axles, the collapse of metallic bridges, the failure of ships and the cracking of aircraft airframes and engines." The research is based on examining not just the bone's mineral density (bone mass) but its quality, specifically how well the collagen that provides the ductility of the bone deforms to resist fractures. And as one gets older, the more microdamage that person accumulates over time and the weaker the bones get.


TIGIT as a Therapeutic Target and Marker of T Cell Senescence and Exhaustion

In the open access paper here, researchers propose TIGIT as a marker of T cell senescence and exhaustion, also known as anergy, in the aged immune system. Further, this is not just a marker, but also a potential therapeutic target, as an initial test of lowered levels of TIGIT resulted in restoration of some measures of lost function in T cell populations with large degrees of senescence and exhaustion. These two forms of T cell dysfunction are not the same thing, but they do have overlapping features, and seem to be connected in a number of ways. In general, such cells perform poorly and behave badly. They show up to increasing degrees in the aged immune system, and play their part in its inflammatory, weakened state.

Much of the research into immune system aging leads to the conclusion that selectively destroying immune cells is helpful. An old immune system is a zoo of breakage and malfunction: too many senescent and exhausted cells; too many cells uselessly specialized to persistent viruses, particularly cytomegalovirus; autoimmunities of many varieties, outright or subtle, some poorly understood or yet to be recognized; and so forth. These problems are to a very large extent within the immune cells themselves. Thus a clean sweep to start over is not a bad idea, or at the very least removal of the known worst classes of malfunctioning immune cell, but these approaches currently lack an implementation safe enough to be used in older people. The only way of doing this at present is high dose treatments with immunosuppressive drugs, optionally followed by cell therapy to rebuild the immune system more rapidly than would other wise happen. This has been shown to cure the autoimmune condition multiple sclerosis, but bears a significant mortality risk, judging from the studies to date.

Distinctly from considerations of the immune system, the discovery of novel markers of cellular senescence is an interesting topic these days. Senescent cells are firmly identified as a cause of aging, producing general effects such as an increase in chronic inflammation, but also tissue- and type-specific effects that are largely detrimental. Senescent cells do assist in wound healing and cancer suppression, but these are transient duties, and the cells that linger afterwards quickly become a liability. Given a novel marker for cellular senescence, or cellular senescence in a specific cell type, it is a fairly slow and expensive process to figure out a pharmaceutical strategy to target it. But one of the companies in the space, Oisin Biotechnologies, has a programmable gene therapy that can in principle be triggered by high levels of any protein of interest inside a cell. Given this sort of capability, the path towards a successful attack on any new and interesting target can be much shorter than it used to be.

T-cell Immunoglobulin and ITIM Domain Contributes to CD8+ T-cell Immunosenescence

Immunosenescence is the age-associated dysregulation of the immune system, of high clinical relevance, as it contributes to multiple age-related comorbidities, including malignancies, infectious diseases, autoimmune diseases, and degenerative diseases. T cells are important components of the immune system. Age-associated T-cell dysfunction is important for the development of immunosenescence.

T-cell senescence is different from T-cell exhaustion, a hyporesponsiveness associated with chronic infections and cancer. Exhausted T cells are derived from activated T cells that progressively lose function because of persistent antigen stimulation, whereas senescence is cell cycle arrest due to aging. However, emerging evidence indicates that T-cell senescence shares several key features with exhaustion. The upregulation of multiple co-inhibitory receptors is not only a hallmark, but also an important mechanism involved in the development of T-cell exhaustion. Consistently, certain co-inhibitory receptors such as programmed cell death protein 1 (PD-1), T-cell immunoglobulin domain and mucin domain 3 (TIM-3), lymphocyte activation gene 3 (LAG-3), and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) are upregulated on T cells from aged mice, and blockade of PD-1 partially restores the functional defect of T cells derived from these mice. This finding indicates a pivotal role of T-cell inhibitory receptors in immunosenescence.

T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT) is a recently identified co-inhibitory receptor that is expressed on activated T cells, regulatory T cells, and natural killer cells. Similar to CTLA-4 and CD28, TIGIT competes with its costimulatory counterpart CD226 for the same ligands (CD155 and CD112) and mediates immune suppression in tumors and chronic infections. Here, we investigated the role of TIGIT in human immunosenescence using blood samples from healthy adults.

As senescent and exhausted T cells exhibit similar features of immune dysfunction, it has been speculated that these two processes share common mechanisms. Studies show that a number of co-inhibitory receptors, including PD-1, TIM-3, LAG-3, and CTLA-4, are associated with impaired T-cell function in aged mice. However, we did not observe a correlation between these co-inhibitory receptors and aging in humans. The discrepancy highlights the limitations associated with the use of animal models in studies of immune senescence. Instead, we found a significant upregulation of TIGIT expression on T cells from elderly healthy donors compared with that from young individuals. The difference was more prominent in CD8+ T cells. TIGIT+ CD8+ T cells expressed high levels of other inhibitory receptors and displayed multiple functional defects, including reduced cytokine production and susceptibility to apoptosis. These data suggest that TIGIT is a biomarker and elucidate a potential mechanism of T-cell senescence. To the best of our knowledge, this is the first evidence linking TIGIT to immunosenescence.

The upregulation of TIGIT in the cohort started early and became worse with age, which indicated that T-cell senescence exists not only in the elderly but also in young individuals. Although senescence is thought to be associated with the physiological aging process, chronic activation, stimulation, or damage may accelerate T-cell senescence. A high percentage of senescent T cells is observed in young patients with chronic viral infections and autoimmune diseases. It remains unclear whether the age-dependent upregulation of TIGIT is associated with a physiological process or pathogenic stimulation. It is possible that TIGIT-associated T-cell senescence is a consequence of physiological stimulation. Moreover, despite TIGIT expression in the young and middle-aged, TIGIT+CD8+ T cells in the elderly were more dysfunctional than the population from the young and middle-aged groups, especially regarding defective cytokine production.

To study a direct effect of TIGIT in T-cell dysfunction, we performed a TIGIT knockdown experiment using siRNA and evaluated the T-cell functions upon TIGIT knockdown. We found a significant increased cytokine release and less apoptosis in CD8+ T cells from elderly subjects upon TIGIT knockdown. This important data demonstrate the suppressive effect of TIGIT in T-cell function in the elderly.

Recent studies demonstrated that TIGIT suppresses antiviral and antitumor CD8 T-cell immunity. Our novel observation that TIGIT is highly expressed on senescent T cells led us to speculate that TIGIT contributes to the functional defect of these T cells and subsequently increases the susceptibility to infection or cancer. In conclusion, the present study demonstrated that TIGIT is a prominent negative immune regulator involved in immunosenescence. This novel finding is highly significant, as targeting TIGIT might be an effective strategy to improve the immune response and decrease age-related comorbidities.

Amyloid-β May Cause Mitochondrial Dysfunction in Alzheimer's Disease

Researchers recently reported evidence for some of the complex, toxic halo of biochemistry that surrounds amyloid-β to be capable of causing mitochondrial dysfunction. It is the certainly the case that there is plenty of evidence for mitochondrial dysfunction to be very relevant to age-related neurodegenerative conditions such as Alzheimer's disease. The hundreds of mitochondria found in every cell act as power plants, and the brain is an energy-hungry organ. In most research, however, the direction of causation is that declining and disrupted mitochondrial function causes amyloid-β accumulation and the other manifestations of Alzheimer's disease. Causation can be a two-way street, however. That aging and age-related diseases accelerate as they progress indicates the presence of feedback loops, in which dysfunction A causes dysfunction B, while dysfunction B makes dysfunction A worse. It isn't unreasonable to expect that sort of connection between many of the mechanisms of neurodegeneration, especially in the later stages.

Two pathological hallmarks are observed in Alzheimer's disease (AD) brains at autopsy: intracellular neurofibrillary tangles and extracellular senile plaques, which tend to occur in the neocortex, hippocampus, and other subcortical regions crucial for cognitive function. These observations have led to a dominant theory of Alzheimer's causality, known as the amyloid hypothesis. The theory points to accumulations of the sticky protein substance amyloid-β as the critical factor initiating the chain of events leading to development of Alzheimer's disease. While the amyloid hypothesis continues to exert a considerable hold on the field, an increasing consensus among researchers is moving away from the idea of amyloid-β accumulation as the primary event that sets the disease in motion.

In a new study, researchers examined the effects of the disease on the functioning of mitochondria - structures performing a variety of essential tasks, including supplying cells with energy. The new research reveals that a highly toxic form of amyloid-β protein - known as oligomeric amyloid-β (OAβ) - disrupts the normal functioning of mitochondria. The result is a fateful cascade of events that appears early in the development of AD - decades before the onset of clinical symptoms.

The most promising finding in the new study is that human neuronal cells can be protected from OAβ-induced deterioration of their mitochondria when they are pre-treated with a custom-designed compound, suggesting an exciting avenue for future drug targeting. "Mitochondria are the major source of energy in brain cells and deficiencies in energy metabolism have been shown to be one of the earliest events in Alzheimer's disease pathobiology. This study reinforces the toxicity of oligomeric amyloid-β on neuronal mitochondria and stresses the importance for protective compounds to protect the mitochondria from oligomeric amyloid-β toxicity."

In the new study, cells known as pyramidal neurons, extracted from the hippocampus of patients who died of Alzheimer's, display a marked reduction in the expression of a suite of mitochondrial genes, pointing to their degradation by OAβ. The reduction of mitochondrial gene expression was also seen when cells belonging to a human neuroblastoma cell line were exposed to OAβ. The authors stress that not all types of nervous system cells are implicated in the mitochondrial dysfunction brought on by exposure to OAβ. Hippocampal astrocyte and microglia cells taken from the same AD-afflicted brains did not display reduced mitochondrial function.

One problem with the amyloid theory of Alzheimer's disease is its inconsistency. Researchers have reported that some elderly patients, bearing heavy burdens of amyloid plaque in their brains, lack any measurable cognitive deficit, while other patients showing little to no amyloid buildup nevertheless display severe Alzheimer's-like dementia. These facts have led researchers to seek other processes occurring at the earliest stages, which may kick the disease into gear. One of the most promising avenues of new research is the mitochondrial cascade hypothesis, which places these energy-delivering powerhouses of the cell at the center of the action. The hypothesis suggests that mitochondrial function, which declines as a natural feature of aging, may be further impaired in the presence of amyloid-β, in particular, OAβ. The fact that severe metabolic deficit appears as a prominent feature of AD further implicates energy-delivering mitochondria as likely culprits in the early disease process.


Evidence for Clearance of Senescent Glial Cells to Slow Parkinson's Disease

Senescent cells accumulate with age and are one of the root causes of degenerative aging. Since senescent cells generate chronic inflammation, removing the accumulation of such cells in old tissues should improve matters for all age-related conditions with an inflammatory component. Of course that will vary greatly from condition to condition and between tissue types - there are other contributing causes for the chronic inflammation that characterizes old age, and in any specific case senescent cells may or may not be the most important cause.

Here researchers look at senescent astrocytes in the brain in the context of Parkinson's disease, finding that removing them in a mouse model of astrocyte senescence is beneficial. This line of research has been underway for a few years now, ever since the start of increased interest in cellular senescence in aging. The Alzheimer's research community is paying attention as well. The animal model used here is fairly artificial, disconnected from the real state of affairs in the aging brain, but the evidence gathered at least makes the point that senescent astrocytes are harmful, and that harm can be reversed by destroying them.

One concerning item in all of this research is that the signs of senescence, in terms of the usual marker proteins expressed, such as p16 and SA-β-gal, appear in a sizable fraction of astrocytes in old people. This may or may not reflect actual senescence, but it is a much higher proportion of cells in comparison to other aged tissues examined to date - sufficiently high to raise doubt over whether this is in fact the same phenomenon observed in better characterized types of senescent cells. It may be just as well that early senolytic therapies do not pass through the blood-brain barrier, as if all of those astrocytes are indeed senescent then removing a quarter to a half of them all at once would likely be dangerous at the very least, and possibly fatal.

In work that could open a new front in the war on Parkinson's disease, scientists have shown that they can stave off some of the effects of the neurodegenerative disease by flushing "zombie cells" from the brain. The approach may have benefits far beyond Parkinson's, with other neurodegenerative diseases - and the ageing process more broadly - all being linked to the ill effects of these "senescent" cells, which linger in tissues. "It's a completely new way of looking at neurodegenerative disease and finding potential drugs. For most of these conditions, we don't have any way to counteract them."

Parkinson's disease usually takes hold when certain types of neurons in the brain become impaired or die off completely. The neurons in question produce a substance called dopamine. Scientists suspected that other cells in the brain - the astrocytes which support the dopamine-generating neurons - may be involved in Parkinson's disease. Specifically, they thought astrocytes might cause problems when they became senescent, a state where cells stop dividing but release chemicals that drive up inflammation. This local inflammation could be harming nearby neurons.

Scientists described how brain tissue taken from dead Parkinson's patients had more senescent astrocytes than healthy brain tissue. They also found that exposing human astrocytes to the herbicide paraquat flipped the cells from a healthy state into senescence. The transformation into the zombie-like state forms part of the body's natural defences against cancer: when cells are in danger of uncontrolled growth, the switch to senescence keeps them in check.

To test whether senescent astrocytes might have a downside - and play a role in Parkinson's disease - the scientists exposed six-month-old mice to paraquat, a weedkiller that has been linked to Parkinson's disease in humans. The herbicide produced senescent astrocytes in the animals' brains and tests showed they had physical difficulties moving around. The scientists next looked at what happened when mice exposed to paraquat were injected with a drug that destroys senescent cells. The drug appeared to protect the mice and kept their movement problems at bay. "They are able to move around their cages well. They are almost indistinguishable from the healthy mice."


An Alternative Approach to Myostatin Inhibition to Increase Muscle Growth

Today, I'll point out a group that is working on a novel approach to myostatin inhibition in humans. Myostatin is a part of the regulatory system for muscle growth. Its role is to suppresses muscle growth, and thus lowered levels of myostatin result in less fat and more muscle in a variety of mammalian species, including our own. Complete removal of myostatin via genetic engineering or breakage through rare natural mutation has resulted in very heavily muscled mice, dogs, cows, and even a few people. The technical name for the outcome is myostatin-related muscle hypertrophy. There are no obvious downsides - which doesn't mean they there are absolutely no issues, but if they do exist, then they are largely subtle and long-term problems.

Given this, there is considerable interest in building therapies based on myostatin inhibition. Quite aside from the potential market for human enhancement, satisfying the desire for muscles without the need to work for those muscles, therapies of this type should help to compensate somewhat for sarcopenia, the characteristic age-related loss of muscle mass and muscle function. Not all of that loss relates to a simple lack of muscle tissue, but where it does, adjusting the regulator of muscle growth could be useful. To date, researchers have trialed the use of antibodies to reduce the amount of myostatin in circulation. This appears successful, though to a much lesser degree than genetic loss of myostatin. This is to be expected, and is usually the case when comparing genetic alterations to inhibition of proteins produced from the genetic blueprint - the inhibition only removes or suppresses a portion of the protein.

Other groups are looking ahead to human gene therapies to either disable myostatin or increase levels of follistatin, the natural inhibitor of myostatin. Follistatin gene therapy in mice produces a similar level of muscle growth as myostatin knockout, and was the approach pursued by BioViva Sciences when Elizabeth Parrish underwent gene therapy as a proof of concept and wake up call for the world. I think in general that the current delivery systems for gene therapy are not yet good enough or cheap enough to merit widespread use: they don't edit the genome in enough cells, and especially in the stem cell populations that would be needed to produce a life-long effect. That will likely change soon enough, however, as many researchers are working on the problem.

The notes below cover an alternative and more sophisticated inhibitory approach for myostatin that is presently under development at Scholar Rock - that this material is out there now has a lot to do with there being a company involved, and one that has just raised a sizable amount of funding. That tends to be how things work in the attention economy: always consider cui bono, though the useful result of a spread of knowledge also occurs as a side-effect. Instead of destroying, binding, or otherwise globally interfering with myostatin molecules, here the researchers involved suppress the activation of those molecules. A better understanding of how myostatin functions as a regulator shows that it spends much of its time inactive, and that the system of activation can be constructively interfered with in a number of ways. While this approach should be more selective, time - and forthcoming human trials - will tell as to whether it is better or worse than the more standard approaches to inhibition of a specific protein when it comes to producing additional muscle.

Scientists elucidate molecular basis of myostatin activation, key process in muscle health

Myostatin (also known as GDF8) is a key signaling protein that contributes to the regulation of muscle mass and function. Initially produced by muscle in a latent inactive form, myostatin can be activated under certain conditions by sequential enzymatic steps. For the first time, the new study provides an understanding at the molecular level of the structural changes that take place in the protein during this activation process, and the central role of the tolloid enzyme in generating active myostatin. Insight into the activation mechanism of myostatin and other related proteins is central to the drug discovery platform established at Scholar Rock for the development of novel therapies for the treatment of many severe diseases.

"Deploying deep structural understanding of growth factors and their activation is opening a profound new way to intervene in human disease. SRK-015, our clinical candidate for the treatment of muscle atrophy and wasting disorders, exemplifies the strong potential of targeting specific structural states of myostatin with the objective of providing superior therapeutic outcomes."

The proprietary therapeutic antibody, SRK-015, was discovered and designed to selectively and locally target the latent form of myostatin with the ability to specifically block its intramuscular activation. In a variety of preclinical models of muscle atrophy, SRK-015 has demonstrated improvement in muscle function. SRK-015 is initially being developed for the improvement of muscle strength and function in patients with Spinal Muscular Atrophy (SMA) with the treatment of additional neuromuscular diseases to follow.

SRK-015 for Spinal Muscular Atrophy (SMA)

SRK-015 uniquely targets the latent form of myostatin, specifically blocking its activation in muscle. Inhibiting the supracellular activation of myostatin, rather than the traditional approach of blocking already activated, mature myostatin or the myostatin receptor, avoids blocking the activity of other closely-related members of the TGFβ superfamily that may lead to undesirable side effects. Scholar Rock is actively working to advance SRK-015 into clinical trials, which are anticipated to commence in mid-2018. We intend to develop SRK-015 in combination with therapies aimed at correcting the underlying genetic defect in SMA and as monotherapy in patients with certain subtypes of SMA.

Tolloid cleavage activates latent GDF8 by priming the pro-complex for dissociation

Growth differentiation factor 8 (GDF8)/Myostatin is a latent TGF-β family member that potently inhibits skeletal muscle growth. Here, we compared the conformation and dynamics of precursor, latent, and Tolloid-cleaved GDF8 pro-complexes to understand structural mechanisms underlying latency and activation of GDF8. Why some TGF-β family members are active and others are latent as procomplexes is incompletely understood. Here, we ask why GDF8 is latent, and what changes when it becomes activated.

GDF8 and its close relative GDF11 are activated by BMP1/Tolloid (TLD) metalloprotease-mediated cleavage of the prodomain between the straitjacket elements and the arm domain. Tolloid-like protein 2 (TLL2), used in this paper, is among the most active on GDF8 of the four TLD proteases found in mammals, and is the only TLD protease expressed in muscle. While TLD cleavage clearly activates signaling by GDF8, whether the two prodomain fragments rapidly dissociate from GDF8 after cleavage, or remain associated with GDF8 in a "primed" state, is not known. Here, we compare pro-GDF8, the state prior to PC cleavage; latent GDF8, the state after PC cleavage; and primed GDF8, a state after TLD cleavage in which we found the persistence of substantial prodomain-GDF8 association.

A Desire for Improved Vaccine Effectiveness as the Spur to Invest in Potential Methods of Immune System Rejuvenation

In the same way that the regenerative medicine field cannot evade addressing the aging of stem cells, the vaccination research community cannot evade addressing the aging of the immune system. The reasons are much the same in both case: all too many of the patients are elderly, and due to the processes of aging, treatments do not work anywhere near as well in older people. Thus effective clinical applications of research will eventually require the relevant effects of aging to be in some way addressed: mitigated or reversed. This is widely understood in the research community. At the present time this understanding largely manifests as efforts to better understand the mechanisms involved. These research communities are large, however, and that means that there are at least a few groups at any point in time whose members are somewhere in the process of moving potential approaches to stem cell or immune system rejuvenation closer towards the clinic.

Vaccines represent one of the most powerful medical interventions against infectious diseases. Effective adult vaccination programs targeting all age groups, including older adults are now more urgent than ever. Changing demographics and the vast increase of aged individuals, necessitates development of efficacious and safe vaccines, suitable for adults and in particular for older adults. While vaccines targeting older populations exist, their performance is often sub-optimal and/or they are under-used. At present, major gaps exist in our knowledge of the mechanisms behind the reduced ability of the aging immune system to respond appropriately to both infections and vaccinations. This hinders our ability to design interventions capable of improving the immune response in older adults and to tailor vaccines better suited for this group.

Aging is characterized by multifaceted changes in the immune system which lead to a progressive reduction of the ability to mount effective antibody and cellular responses against infections and to vaccinations. This phenomenon, referred to as immunosenescence, is multifactorial: it affects both arms of the immune system and can be influenced by genetic factors and extrinsic factors, such as nutrition, physical exercise, co-morbidities, physical and mental stress, previous exposure to microorganisms, toxins, and pharmacological treatments. Consequently, the presenting forms of immunosenescence are protean, varying at population and individual levels.

Therefore the concept of "Bioage" is arising to describe the concept that the real age is not the chronological, but the biological one. The concept of "bio-age" is in line with the observation of the wide variability of immune responses observed in the elderly after vaccination. In addition, it is in line with the increasing evidence that the immunological experience that individuals have during their lives can shape their ability to respond to external stimuli, such as infections or vaccinations. The pro-inflammatory environment of the aging body is a common denominator of aging which is referred to as "inflammaging". Extensive scientific literature has been published on this area and among the many hypothetical potential causes, the most popular is infection with cytomegalovirus (CMV). Indeed, strong CMV seropositivity has been associated with lower antibody and cellular responses to a variety of vaccines. The long-term maintenance of vaccine-specific antibodies seems to be hampered by CMV.

Considering the pleiotropic nature of immunosenescence and its variable expression among older individuals, it is not surprising that, despite the "physiological" decay of the immune responsiveness with age, vaccination remains a vital intervention in the older adults. Several pharmacoeconomic studies have underlined the benefit of influenza vaccines in terms of lives saved and reduced direct and societal costs linked to reducing influenza-related morbidity and mortality. Moreover, failure to vaccinate is associated with excess mortality due to infection and its complications. However, some vaccines have been shown to exhibit sub-optimal efficacy in recipients of advanced age or significant frailty. Differences in bio-age, immunobiography, and trained immunity can reconcile the apparent discrepancy between the reduced response of the elderly to some existing vaccines, and the evident successes that have been obtained recently. There is reason to believe that we can improve on the former by deciphering the mechanisms underlying the latter.


Wnt Signaling and p53 in the Progression of Heart Failure

If at the bottom of aging are root causes, and at the top of aging are end results, meaning organ and tissue failure and age-related disease, then the majority of aging research is focused on the middle layer of the problem in between. This middle layer is made up of the exceptionally complex changes in cellular biochemistry that take place over the course of aging, a snake-pit of long chains of cause and effect, with many feedback loops and interactions. All of this is incompletely investigated, and the links to top and bottom tiers of aging are in many places only tenuously understood or proven. Making progress towards a grand map of cellular metabolism and aging is very slow and very expensive.

The research here is an example of this type of work, illustrating that even the better-studied portions of the cellular biochemistry of aging include collections of contradictory observations and clashing evidence, yet to be explained, and that there is all too little consideration given as to why the observed changes take place. Until more attention to root causes appears on a regular basis in everyday papers such as this one, then the research community will continue to give little attention to those root causes. As a consequence little progress will be made in the matter of preventing and reversing aging. Researchers will remain in the wilderness of the middle layer, eternally cataloging, and never intervening in any effective way.

Heart failure, which is a complex pathophysiological syndrome, is one of the leading causes of mortality in the world. In the cardiovascular area, there is an age-dependent increase in the prevalence of left ventricular hypertrophy, diastolic dysfunction, and atrial fibrillation, which are not necessarily associated with classical risk factors for cardiovascular diseases. There is also an aging-related increase in vascular intimal thickening and vessel stiffness. In addition, maladaptation and/or abnormal response to stress (e,g,. pathological hypertrophy, apoptosis, replacement fibrosis, progression to heart failure) can be aging-related.

Here, we will review the contribution of Wnt/β-catenin signaling and p53 pathway, both of which play an important role in aging, to the progression of cardiac remodeling and dysfunction in the failing heart. Wnt/β-catenin signaling plays critical roles in stem cell self-renewal, development as well as adult homeostasis, and augmented Wnt/β-catenin signaling is also implicated in aging, aging-related phenotypes, and various diseases. Wnt/β-catenin signaling is activated in the failing heart. Circulating C1q was identified as a potent activator of Wnt/β-catenin signaling, promoting systemic aging-related phenotypes including sarcopenia and heart failure.

In a previous report, cardiac-specific overexpression of a positive regulator of Wnt/β-catenin signaling was found to cause extensive hypertrophy, heart failure, and premature death in mice. On the other hand, it was reported that stabilization of β-catenin attenuates adaptive cardiac hypertrophy and leads to impaired cardiac function under angiotensin II treatment. The Wnt1/β-catenin injury response activated cardiac fibroblasts to promote cardiac repair after acute ischemic cardiac injury, preserving cardiac function. In other reports, blocking of Wnt/β-catenin signaling was shown to avert adverse remodeling or improve cardiac function in animal models of myocardial infarction. In spite of such a context-dependency, Wnt/β-catenin signaling is thought to play a pivotal role in the progression of cardiac dysfunction/heart failure.

The p53 pathway also plays an important role in the pathophysiology of heart failure through the induction of aging-related phenotypes. Replicative senescence induced by telomere dysfunction and stress-induced premature senescence are mediated by p53. p53 activates a cellular response to stress signals (e,g,. DNA damage) that leads to a halt in proliferation via apoptosis or senescence. Such a depletion of cells could compromise the structure and function of tissues, which are the processes towards aging-related phenotypes and tumor suppression. In particular, because cardiomyocytes do not proliferate after birth, p53 exerts a pathogenic effect on cardiomyocytes through the induction of apoptosis.

Further investigations with multidisciplinary approaches will be required to fully clarify the molecular mechanisms underlying heart failure.


The Old-Fashioned Approach to Delivery and Targeting of Gene Therapy for Arthritis

Sometimes the old-fashioned, simple solution is more than sufficient for the task at hand. In today's open access review paper, researchers discuss the delivery and targeting of gene therapies to arthritic joint tissue via the simple expedient of injecting the therapeutic into the joint - the most modern of medical treatments married to a 150-year-old technology. And why not? The alternatives for targeting a therapy to a specific tissue are numerous, but all quite complicated and expensive: magnetic fields to guide metallic nanoparticles attached to the therapeutic; using seeker proteins that preferentially match the surface structure of a given cell type; DNA machinery that checks the internal state of a cell and only triggers the therapeutic if the local environment appears correct; and so forth.

First generation gene therapies are appearing in clinical trials in ever larger numbers, hundreds in recent years, though the term covers a wide range of what are arguably quite distinct approaches and endpoints. Very few of these use CRISPR today; most are older delivery technologies working their way through the last portions of a years-long development pipeline. That story will likely be very different a couple of years from now, given the enthusiasm with which the research community has embraced CRISPR. Today's candidate gene therapies largely have effects that are temporary, as the delivery mechanisms don't successfully transfer their cargo into a large number of cells. Of those that are affected, near all will be somatic cells, limited in their ability to replicate, and thus altered cell lineages in a tissue will die out in a matter of months at most.

Putting aside the more advanced, machine-like, and programmable gene therapy platforms, such as that pioneered by Oisin Biotechnologies, most present day gene therapies in trials are essentially a way to make some cells produce more of a specific protein for some period of time. Each is an indirect two-stage protein delivery system, in effect, using cells as a local manufactory. All cellular machinery is controlled by levels of specific proteins - the amount of a specific protein in circulation in the local environment is a switch, or a dial. The cell is a fantastically complicated collection of these switches and dials, most of which can affect numerous others, forming feedback loops and chains of cause and consequence. Directly altering the amount of a specific protein is better than the use of pharmaceuticals to achieve the same aim, given that even the best drugs have all sorts of side-effects, but it is still a crude approach to obtaining the desired end results. Changing the amount of a protein will have all sorts of downstream effects that may or may not be helpful, in addition to the desired outcome. Future medical technologies will likely become more sophisticated in their control over cellular operations.

Though, ironically, these anti-arthritis gene therapies are conceptually quite crude. They target controlling mechanisms of inflammation in a fairly heavy handed way - following the well-established pharmaceutical industry path for inflammatory conditions, which is to suppress inflammation and the immune response rather than go further in search of the causes of the problem. Yes, there is inflammation, but why is there inflammation? Why not find and target that root cause? The arthritis research community will likely undergo a considerable rearrangement of priorities and leaders in the years ahead, if the results obtained in mice for arthritis and clearance of senescent cells translate into human patients. Senescent cells are one of the root causes of aging, and it appears that their accumulation, and their pro-inflammatory signaling, is a significant cause of at least some types of arthritis.

Gene Delivery to Joints by Intra-Articular Injection

With the exception of rheumatoid arthritis (RA) and related autoimmune conditions, disorders of joints tend to be local and usually affect a small number of joints - often only one. Such circumstances favor intra-articular therapies, where the therapeutic agent is delivered directly to the affected joint. Compared to systemic delivery, this reduces the likelihood of adverse events in non-target organs, maximizes the concentration of the therapeutic at the site of disease, and, by treating a joint instead of the whole body, lowers cost. Joints are discrete, enclosed cavities, and most are readily accessible to intra-articular injection, which is the delivery method of choice.

Although it is a straightforward matter to inject therapeutics into joints, the effectiveness of intra-articular therapy is greatly compromised by the rapidity and efficiency with which material leaves the synovial space. Small molecules diffuse out through the sub-synovial capillaries, while macromolecules and particles leave through the lymphatics. It is thus very difficult to achieve sustained, therapeutic concentrations of drugs in joints. The idea to use gene therapy for joint disorders arose in response to this problem. The original concept was to target gene delivery to the synovium for treating arthritis. This would lead to the sustained synovial synthesis of therapeutic gene products locally within joints. Such a strategy also obviates another problem for treating joints with biologics, namely the restricted access of proteins and other large molecules to the interior of the joint from the circulation.

Intra-articular injection of suspensions of genetically modified cells is unlikely to achieve long-term transgene expression because injected cells are cleared from joints within days to weeks. Persistent intra-articular expression following in vivo gene delivery was only achieved when the importance of the immune system in curtailing transgene expression was fully appreciated. This followed experiments in which vectors were injected into the knee joints of athymic rats. Under these conditions, transduction of the synovium was initially high, but transgene expression then fell as a result of synovial cell turnover, persisting at about 25% of the early level for the rest of the animals' life-span. Similarly extended periods of transgene expression are achieved when immunologically silent vectors are used to deliver autologous gene products in wild-type animals.

Proof of concept has now been achieved for both in vivo and ex vivo gene delivery using a variety of vectors, genes, and cells in several different animal models. There have been a small number of clinical trials for rheumatoid arthritis (RA) and osteoarthritis (OA) using retrovirus vectors for ex vivo gene delivery and adeno-associated virus (AAV) for in vivo delivery. AAV is of particular interest because, unlike other viral vectors, it is able to penetrate deep within articular cartilage and transduce chondrocytes in situ.

Although gene therapy for arthritis and related conditions has been discussed for more than 25 years, progress toward clinical application has been slow. Nevertheless, there have been several clinical trials, and the first product, Invossa, has just received marketing approval in Korea. Phase III human clinical trials of Invossa are projected to begin shortly in the United States. Its approval should stimulate interest in the entire field leading to more rapid development of genetic drugs for conditions that affect joints. Invossa targets OA by the injection of allogeneic chondrocytes that have been transduced with a retrovirus carrying transforming growth factor-β1 cDNA. Meanwhile, two additional Phase I trials are listed, both using AAV. One targets RA by transferring interferon-β, and the other targets OA by transferring interleukin-1 receptor antagonist. The field is thus gaining momentum and promises to improve the treatment of these common and debilitating diseases.

Evidence for Human Species Longevity to be a Matter of Many Small Adaptations

Why do humans live so much longer than other, short lived species? The researchers here provide evidence to suggest that it is a matter of many small changes, with the specific area of investigation being the the cellular repair mechanisms of autophagy. A world in which differences in longevity between species are the summed contributions from countless small effects is one in which we should discount the possibility that comparative genetic studies - between long-lived and short-lived humans, or between humans and other species - can yield silver bullets, findings that can on their own offer the potential to dramatically improve health and longevity. That expectation, and the sizable mountain of other evidence for the "many tiny contributions" model can be weighed against the recent reports of human PAI-1 mutants with a seven year greater life expectancy than their peers. I wouldn't have wagered on the discovery of such a thing, given what is otherwise known of the genetics of longevity.

Research into the importance of protein called p62 shows that a collection of small adaptations in stress activated proteins, accumulated over millennia of human history, could help to explain our increased natural defences and longer lifespan. Many cells in our body, such as those which make up our brain need to last us a lifetime. To do this our cells have developed ways of protecting themselves. One way is through a process called autophagy, which literally means self-eating, where damaged components are collected together and removed from the cell. "As we age, we accumulate damage in our cells and so it is thought that activating autophagy could help us treat older people suffering from dementia. In order to be able to do this we need to understand how we can induce this cell cleaning."

In the study the authors were able to identify how a protein called p62 is activated to induce autophagy. They found that p62 can be activated by reactive oxygen species (ROS). ROS are by-products of our metabolism that can cause damage in the cell. This ability of p62 to sense ROS allows the cell to remove the damage and to survive this stress. In lower organisms, such as fruit flies, p62 is not able to do this. The team identified the part of the human p62 protein which allows it to sense ROS and created genetically modified fruit flies with 'humanised' p62. These 'humanised' flies survived longer in conditions of stress. "This tells us that abilities like sensing stress and activating protective processes like autophagy may have evolved to allow better stress resistance and a longer lifespan."

Indeed, in the study, the authors found that specific mutations in human p62, which cause a neurodegenerative disease called amyotrophic lateral sclerosis (ALS), can prevent activation of p62 by ROS. These cells are then unable to induce protective autophagy, and this could underlie the premature death of neurons in patients with this devastating age-related disease. The research demonstrates that a collection of small adaptations like that of human p62 could have accumulated over time and these adaptations could underlie our increased natural defences and longer lifespans.


Even Modest Changes in Calorie Intake and Weight can Ruin any Study of Health

Calorie restriction has a large beneficial effect on health and longevity in mice, and as a result any number of studies carried out over the past century were ruined - usually without the researchers noticing - because no attempt was made to control for calorie intake and weight. Any treatment that causes nausea in mice, and thus a lower calorie intake, may have mistakenly reported benefits. Any treatment that resulted in mice eating more may have mistakenly missed benefits or reported harms.

The same general principle applies for people running their own self-experiments of treatments that might slow or turn back aging to some degree - something that will become ever more common as the world wakes up to the potential of low-cost senolytic treatments that can remove senescent cells, one of the root causes of aging. As the article here makes clear, all it takes is a short period of changed calorie intake and weight to throw off most of the indirect metrics one might use to assess the results of an early, comparatively crude senolytic treatment. For individuals in the earlier stages of aging, benefits are likely to be subtle and more easily obscured. It is something to think about: consistency in lifestyle, particularly diet, is very important when trying to measure effects.

Gaining and losing weight causes extensive changes in the gut microbiota and in biomarkers related to inflammation and heart disease, researchers report. The researchers monitored subjects' omics profiles as they added extra snacks and beverages to their regular diets. "We were fortunate we got 23 people who would eat extra calories - typically 1,000 if you're male, 750 if you're female - every day for 30 days. They're just a very interested bunch of folks. They have to be to show this kind of dedication to giving samples." The team collected samples before and after the 30 days of eating extra calories, as well as after participants returned to their starting weight, about 60 days after dropping the extra calories, and then three months after that. Of the 23 participants, 13 were insulin resistant and 10 were insulin sensitive at the beginning of the study. Comparisons of baseline profiles showed differences in metabolism, transcript and protein levels, and the microbiota of insulin resistant and insulin sensitive people.

Although subjects only gained an average of about six pounds, the researchers detected considerable changes in molecules related to fat metabolism, inflammation, and dilated cardiomyopathy, a condition where the heart is less able to pump blood, which can lead to heart failure. The team also found differences in the gut microbiota after weight gain. Many of the shifts the scientists observed were less pronounced in the insulin-resistant individuals. For instance, one bacterial species - Akkermansia muciniphila, which is thought to help protect against the development of insulin resistance after weight gain - only appeared in the insulin-sensitive participants. "There is a molecular difference in the way [insulin] resistant and sensitive folks react to gaining weight, and we think it reflects differences in their underlying biochemistry."

Most of the changes went back to baseline after weight loss, but a few - such as molecules associated with folate metabolism - stayed elevated. And while the researchers saw some common responses to weight gain and loss across the group, "you still look more like you than somebody else. That means that our inherent biochemical profiles are pretty stable, at least through weight gain and weight loss."


Senescent Cells are Large, which Suggests a Few Simpler Paths to Assays for Senescence Level in Human Subjects

The rise in number of senescent cells with age is one of the root causes of degenerative aging. Somatic cells become senescent when they reach the Hayflick limit on replication, or become damaged, or encounter a toxic environment. They cease replication, and either self-destruct or are destroyed by the immune system. Some small fraction of the countless cells that become senescent each and every day manage to evade destruction, however. They linger, in ever greater numbers with each passing year, and the potent mix of signal molecules they secrete contributes to many forms of tissue dysfunction and organ failure, ranging from fibrosis and loss of regenerative capacity to increased inflammation and loss of tissue elasticity.

Fortunately, we stand just a few years removed from of the clinical availability of therapies that can destroy some fraction of these cells. A few startup companies are working on senolytic treatments ranging from repurposed chemotherapeutic drugs to gene therapies to antibody therapies. Senolytic treatments that work in humans will literally produce rejuvenation to some degree, turning back one of the causes of aging. They don't even have to be expensive in the case of repurposed drug candidates, though these are unlikely to be as effective as the final results of further development efforts. Indeed, the adventurous can order and use some of these drug candidates even now, and experiment upon themselves, with very little outlay of funds. Caution is always recommended, of course.

Perhaps the most important objection to self-experimentation in the matter of the first legitimate rejuvenation therapies is that there is no readily available measure that will determine just how many senescent cells have been destroyed by a treatment. This is a challenge for formal human pilot trials as well. It means that secondary measures or expensive laboratory work are required, and in a basically healthy individual in middle age, it may well be the case that it is hard to separate out the effects of a crude but legitimate rejuvenation therapy from the noise. Aging has numerous distinct contributing causes, forms of cell and tissue damage that mingle to produce the initially slow decline. It is reasonable to expect it to be hard to see the short-term effect of removing 25% of senescent cells in, say, a 50-something individual who has yet to develop a severe manifestation of any of the age-related conditions most strongly linked to cellular senescence. On the other hand, maybe it will produce meaningful impact in cardiovascular measures such as blood pressure and pulse wave velocity. Without referencing a body of data that doesn't yet exist, it is hard to say which of these is the case.

Measures of senescent cell counts in a living individual would be inarguable, however, assuming they could be carried out without generating injury in the process of obtaining that information, as senescent cells are generated temporarily as a part of the response to wounding. Given such a metric, assessed before and after a treatment, one could definitively say whether or not the treatment achieved the intended result - and then all the uncertainty in secondary benefits achieved at any given age and health status will become more a matter of interesting further research than an outright roadblock. Unfortunately, we don't yet have a useful and broadly available tool to achieve this result. Possibilities include, say, some form of blood sample analysis that looks for the distinctive pattern of signal molecules produced by senescent cells. That is a reasonable research and development project for any group capable of proteomics-based analysis of blood, and perhaps there are people out there working away on it, quietly.

The authors of the open access paper below present an intriguing alternative, and one that might be more easily established and deployed. It is based on the observation that senescent cells are large, some twice as large as normal cells, or even larger. Thus these cells could be filtered from blood via the use of suitably sized fluid channel devices and then counted via flow cytometry, a task that is well-established and business as usual in the microfluidic device industry. Is it reasonable to expect that a higher burden of senescence throughout the body would be more or less accurately reflected by a larger number of senescent cells in the bloodstream? Possibly, but again, the work to prove and quantify all of that has yet to be accomplished. Still, the microfluidics approach to a senescence assay seems a very promising direction for further development.

Senescence chips for ultrahigh-throughput isolation and removal of senescent cells

Cellular senescence is a state of permanent cell cycle arrest due to genotoxic stresses and has been shown to be involved in organismal aging and tumorigenesis. Therefore, cellular senescence is an important biomarker for aging as well as genotoxic stresses such as ionizing radiation. However, the small number of senescent cells in biofluids such as whole blood limits their quick and sensitive detection. An effective isolation approach is highly desired for senescent-cell-based point-of-care diagnostics such as radiation biodosimetry. Moreover, recent animal studies have demonstrated the potential of therapeutic targeting of senescent cells for anti-aging and age-related diseases. Because pathways up- or downregulated in senescent cells, such as those involving p16, p21, and p53, also function at various degrees in their healthy counterparts throughout the tissues and organs, conventional methods by targeting these pathways with small molecules and protein drugs could result in side effects in humans. Alternatively, physical means by taking advantage of the cell size increase during cellular senescence provides an attractive novel approach to selectively remove senescent cells from their nonsenescent counterparts and other background cells.

Different microfluidic techniques have been developed for cell separation based on their physical properties. Among those techniques, filtration is the most promising approach to process undiluted whole blood for rare cell separation, and easily scaled up for high throughput. However, several challenges need to be overcome before this technique could be widely used. In dead-end flow filtration which has the flow direction perpendicular to the filter surface, a common issue is the clogging and saturation of the filter, resulting in low separation efficiency, sample purity, and device robustness. In some studies, a periodic reversed flow or fluidic oscillation was adopted to address clogging. To avoid cell damage and clogging issue, cross-flow filtration in microfluidics was developed with a flow direction parallel to the filter surface. Therefore, a shear force was generated to bring the bigger particles to the downstream instead of entering the filtration pores. However, to ensure effective cell separation in a parallel-flow configuration, the cross-flow filtration typically has a much longer channel with a throughput usually lower than 1 ml/hr. Despite the inherent low throughput for microfluidic devices, a higher throughput (e.g., more than 1 ml/min) is highly desired to process a large volume of whole blood samples. High throughput is particularly challenging for a continuous flow because of the difficulties in system integration and fluidic control for multiplexing on a microfluidic chip.

To overcome the clogging and cell damage issue while still achieve a high throughput and recovery rate, we developed a microdevice (senescence chip) for three-dimensional size sieving by taking advantages of both dead-end flow and cross-flow filtrations. A slanted micropillar array was fabricated with an inclination angle relative to the fluidic flow (between 0° to 90°). Therefore, the particles could not only be sieved efficiently but also experience a fluidic shear force to reduce clogging and preserve cell integrity. Moreover, the micropillars worked as cantilevers, which had only one end fixed. Their flexibility allowed small deformation when experiencing a fluidic pressure, creating hundreds of shutters in the vertical direction responsive to the flow rate. These shutters helped to release backpressure, reduce clogging, and dramatically improve separation throughput.

We utilized our senescence chip to isolate and analyze senescent cells in undiluted whole blood and mouse bone marrow. We chose mesenchymal stem cells (MSCs) because we have previously characterized their ionizing radiation-induced senescence progression. In this study, we utilized H2O2- and X-ray-induced senescent human MSCs spiked in whole blood, as a model biological system, to demonstrate the rapid separation and analysis of senescent cells using our senescence chip. The optimized device was then used for an animal study to isolate senescent cells from the bone marrow of mice undergone total body irradiation (TBI) of X-ray. To achieve ultrahigh-throughput removal of senescent cells for blood purification, we enlarged the chip dimensions and stacked multiple chips to build a multiplexed system. We demonstrated that our scaled-up senescent chip could achieve a parallel processing with a throughput up to 300 ml/hr.

The Prospect of Filtering Harmful Factors from Old Blood

The Life Extension Advocacy Foundation volunteers here interview Irina and Michael Conboy, two of the more influential scientists involved in parabiosis research. When the circulatory systems of an old mouse and a young mouse are connected, the older partner shows some reversal of measures of degenerative aging, while the younger partner shows some acceleration of similar measures of degenerative aging. The Conboys have of late produced evidence to show that this is based on the presence of harmful factors in old blood, where parabiosis dilutes harmful factors in the old mouse but also passes them over to the young mouse. There is similar evidence for beneficial factors in young blood passing in the opposite direction, however.

All of this data raises the possibility of somehow filtering out the harmful factors if they can be reliably identified. While numerous forms of blood filtration equipment exist today, it seems unlikely to me that being hooked up to a suitably adapted variant for a short time would provide lasting benefits - though it could certainly be used in studies to settle debates over the degree to which specific factors are involved or important. Harmful factors are, after all, generated on an ongoing basis by cells that are damaged or are reacting to the damage of aging. To produce useful results, filtering would have to be permanently in place, such as via an implant of some sort, or enhancement to the kidneys, or pharmaceuticals that inhibit harmful factors, and none of these options seem likely to appear immediately - all would require significant development. Even with that development, such an approach is not actually addressing the causes of the issue, but rather tries to patch over just a thin portion of it.

For the sake of those new to the topic, what is it in young blood and aged blood that affects aging?

Numerous changes in the levels of proteins that together regulate cell and tissue metabolism throughout the body. We wondered why almost every tissue and organ in the body age together and at a similar rate, and from the parabiosis and blood exchange work now think that young blood has several positive factors, and old blood accumulates several negative, "pro-aging" factors. We have published on improved liver regeneration, reduced fibrosis and adiposity by transfusion of old mice with young blood, but these are genetically matched animals, and in people, we do not have our own identical but much younger twins.

How do you propose to balance the cocktail of factors in aged blood to promote a youthful tissue environment?

We are working on the NextGen blood apheresis devices to accomplish this. We are collaborating with Dr. Dobri Kiprov, who is a practicing blood apheresis physician with 35 years of experience, and he is interested in repositioning this treatment for alleviating age-related illnesses.

Do you think a small molecule approach is a viable and, more importantly, a logistically practical approach to calibrate all these factors compared to filtering aged blood?

Yes, it is a very feasible alternative to the NextGen apheresis that we are working and publishing on.

Even if we can "scrub" aged blood clean, is it likely to have a long-lasting effect, or would the factors reach pro-aging levels fairly quickly?

That needs to be established experimentally, but due to the many feedback loops at the levels of proteins, genes and epigenetics, the acquired youthful state might persist.

Ultimately, could a wearable or an implanted device that constantly filters the blood be the solution to these quickly accumulating factors?

Maybe, but the first step of a day at a NextGen apheresis clinic once every few months might be more realistic.

What do you think it will take for the government to fully support the push to develop rejuvenation biotechnology?

Clear understanding of the current progress and separating the real science from snake oil is very important for guiding funding toward realistic clinical translation and away from the myth and hype.


Suggesting that Only Minimal Loss of Synapses Occurs in Alzheimer's Disease

There are signs from past years to suggest that Alzheimer's disease is a reversible condition, at least in its earlier stages. In other words, that there is little loss of the structures holding the data of the mind, and the condition degrades the operation of the mind, not its underpinnings. The consensus, however, is that this stops being the case further into the progression of the disease, and significant losses do in fact occur. The researchers here disagree with that consensus, providing data to suggest that even in later stages the condition is not destroying significant numbers of synapses. This will definitely require further supporting evidence before it can be taken at face value, particularly since it is really only assessing the presence of key synaptic proteins in tissue samples, rather than any more in-depth analysis of structure and function.

Frequently encountered in the elderly, Alzheimer's is considered a neurodegenerative disease, which means that it is accompanied by a significant, progressive loss of neurons and their nerve endings, or synapses. A new study now challenges this view. Conducted among more than 170 subjects at various stages of Alzheimer's disease, the study has shown instead that the disease is accompanied by a minor decline in neuronal and synaptic markers. "Much to our surprise, in studying the fate of eight neuronal and synaptic markers in our subjects' prefrontal cortices, we only observed very minor neuronal and synaptic losses. Our study therefore suggests that, contrary to what was believed, neuronal and synaptic loss is relatively limited in Alzheimer's disease. This is a radical change in thinking."

The scientists also attempted to correlate all these minor synaptic losses with the subjects' level of dementia. Their results show that the declines in synaptic biomarkers had little impact on the participants' cognitive skills. The study implicitly suggests that dementia is associated with a synaptic dysfunction rather than the disappearance of synapses from the patient's cortex. Identifying this dysfunction could lead to the development of effective treatments for this disease. "Until now, therapeutic interventions have been aimed at slowing synaptic destruction. Based on our study, we are going to have to change our therapeutic approach."


Aubrey de Grey on Ending Aging and the Relative Merits of Various Approaches

Here is the transcript of an interview, published last week, with Aubrey de Grey, advocate and coordinator of rejuvenation research, originator of the Strategies for Negligible Senescence (SENS) scientific programs, and cofounder of the Methuselah Foundation and SENS Research Foundation. Over the past fifteen years, de Grey and his growing network of allies within and outside the scientific community have had an outsized influence on the culture of aging research, on public perception of the treatment of aging as a medical condition, and on meaningful progress towards therapies capable of rejuvenation. All of this has been achieved the old-fashioned way, ignored by mainstream funding institutions, and proceeding on the basis of a great deal of hard work and the pledges and philanthropic donations provided by a small, enthusiastic, and visionary community of supporters.

At the turn of the century, the field of gerontology was run by senior researchers who actively suppressed public discussion and funding aimed at lengthening life or addressing the causes of aging. That was the product of decades of setting themselves up in opposition to the fraudulent "anti-aging" marketplace of pills and potions, but it was still the wrong thing to do - and it held back progress. At that time, despite the wealth of evidence to point the way to the molecular damage that causes aging, anyone talking seriously about treating aging was mocked. That was the environment facing the first members of the modern rejuvenation research community of patient advocates and a few brave researchers willing to risk their careers.

In the years since then, we have collectively brought about a sea change, a great transformation in both research community and culture. Now, members of the scientific community enthusiastically discuss the treatment of aging, how to intervene in its progression, without fear of repercussion. A hundred times or more the investment in viable rejuvenation research programs is taking place, and venture investment in companies working on ways to address the medical condition of aging is well underway. The first rejuvenation therapies, those based on clearance of senescent cells, are under development in startup biotech companies, on their way to the clinic. None of this would have happened anywhere near as rapidly without the actions of those first individuals brave enough to champion an unpopular cause, to provide the first philanthropic funding for advocacy and research, to step up and make a difference, to swim against the current of the times.

Ending Aging, with Aubrey de Grey

Mark Sackler: You wrote the book Ending Aging in 2008. You identified seven areas of cellular and intracellular damage that you think need to be reversed as the best process for reversing aging. In the nine years since you wrote that book, what has changed? Are we where you thought we'd be by now? Have there been any breakthroughs?

Aubrey de Grey: People often ask me, "When are you going to write a new book - when are you going to update Ending Aging?" It's not a priority right now. It could easily be presumed to be saying that it's not my priority simply because I haven't made much progress and there's not much to say. But it's just the opposite of that - there's been massive progress, but it's been pretty much exactly the progress that we were predicting in the book. So essentially the plan is the same 7 points. There's no problem number 8 or 9 that came along and had to be added. And furthermore, the solutions that we discussed in the book are still the same solutions. There's nothing that has come along that has made us have to revisit it and say, well, OK, the approach that we thought was going to be the right way to go is actually much harder than we had expected and therefore we need something else­­ - none of that has happened. There have been some surprises, but they have all been good surprises in the form of innovative technologies­ - new discoveries that have allowed us to pursue the same approaches but more effectively and more rapidly than we otherwise thought.

Now there is one downside, though, which is, back then I started making predictions about the time frames of how long this will all take. And of course, I was always making a lot of caveats emphasizing that a prediction of time frames was very speculative for any pioneer in technology. However, the fact is we haven't hit the time frames I was saying that we would. But what's gone wrong is not the science, but something else. The answer is the money. The fact is that my predictions were always very strongly conditional on the ability to bring in funding that was sufficient so that the rate of progress would only be limited by the sheer difficulty of the technology, the actual science and practice. I believe we've been going along three times more slowly than that initial prediction simply because it's been so much more difficult than I had expected to attract sufficient funding.

Mark Sackler: What about using pharmaceuticals or supplements to slow the aging process - to buy more time before we reach SENS 1.0? There are several agents out there now. Metformin is about to go into human clinical trials, Rapamycin is in trials with dogs, and NAD+ supplements are all the rage right now. What's your take on all of this?

Aubrey de Grey: So I'm all for this work. I think that it's very valuable in helping people to stay healthy longer. However, there is a very important feature of all of these supplements which is very often swept under the carpet by the researchers and companies that are working on them. They're all hypothesized to work by calorie restriction memetics. In other words, drugs that trick the body into thinking it's not getting as many calories as it would like, even though it is getting them. So that's wonderful. Except that there's a huge catch, and it has been a totally incontrovertible message in the animal data for decades. It is a fairly scandalous thing that has been swept under the carpet. The problem is that different species respond by different degrees to this kind of restriction. Specifically, long-lived species respond less than a short-lived species. The world record for how much you can extend the life of a nematode worm that normally lives about three weeks is by a factor of five. But then if you go up and look at organisms that live a couple of years, like mice, you can only get a factor of one and a half. That's still very impressive but it's definitely not five. But unfortunately, this trend persists as you go higher up the chain.

For example, about 20 years ago you're in a very thorough and rigorous trial made with Labrador dogs, which normally live about 11 years, and on the whole, it resulted in only about a 10% increase in lifespan. And over the past 20 odd years, two groups in the US have performed extraordinarily expensive and time-consuming experiments of calorie restriction on monkeys, and depending on how you interpret that, it yielded maybe a couple of percent increase. So, the prognosis for humans is not terribly good. Now again I want to emphasize I'm fine with the fact that people are excited by these drugs, because they do seem to keep people healthy; they are protective, but it is critical not to make the extrapolation that they are the foundation to extending life - because in no way has that happened.

Mark Sackler: One of the hottest biotech topics lately has been genetic editing, and there have been at least two individuals who recently had genetic editing therapy performed on themselves. I wonder what you make of those efforts.

Aubrey de Grey: Well, first let me talk about gene targeting in general. CRISPR is a fantastic breakthrough. When I was talking at the beginning about the surprises that we'd had, that's probably the single biggest one - because the fact is that before it came along, there was very little that we could do to change genes. We had methods for gene targeting, for modifying the genome, but they were very laborious and expensive. Now as for self-experimentation one can look at it in a whole bunch of ways. First, one can be curmudgeonly about it and say, well okay, this is very unsafe. God knows what's going to happen if bad things happen if these people die as a result of that therapy; it is going to set back the whole field to a large degree. That's all true up to a point. But at the same time, we have to remember that self-experimentation is not new. It has a long and very distinguished history in biology. JBS Haldane, the distinguished and respected British biologist from the 1930s, was rather famous for doing things to himself that I certainly wouldn't dare to. Certainly, the scientific information that will come from this sort of experimentation effort is probably very limited, simply by the fact that it is a sample size of 1. But on the other hand, the high-profile news that arises and the fact that people are talking about what is happening and a discussion is actually occurring, has its own value. If people are not interested in something, it's very hard to get them to think about it, whereas if they are interested, even for an unusual and rather tangential reason, you can educate them.

Mark Sackler: Earlier this year I interviewed David Wood on his book The Abolition of Aging. In it he forecast that by 2040 there is a 50-50 chance of there being widely available affordable rejuvenation therapy. How do you feel about that forecast right now? Is it overly optimistic? Is it well within reach if there's enough money, or is it totally uncertain?

Aubrey de Grey: It's pretty much exactly the same as my prediction. That may not be a coincidence.

Evidence for mTOR to be Involved in Vascular Aging and thus Vascular Dementia

Research into mTOR and aging is becoming quite diverse. Researchers here present evidence for mTOR to be involved in the aging of the vasculature, and thus also in the development of vascular dementia. One of the noteworthy aspects of aging is the declining ability of the vascular system to deliver sufficient nutrients and oxygen to cells, and this is considered important in the decline of both brain and muscles, two of the more energy-hungry tissue types.

The research here is a good example of the way in which most researchers restrict their scope to relationships between areas of protein machinery that are very close to the disease state, without looking back down the chain of cause and consequence towards any sort of root cause. Detailed changes in proteins and their interactions are cataloged, but there is next to no consideration of why these changes in levels and interactions of proteins take place in aging. Instead of working further backwards - or better, starting with the known root causes of aging and working forwards - the impetus is to intervene in order to adjust the protein interactions of the disease state in some way.

At the SENS Research Foundation, the home of interventions that target root causes in aging, this tendency in the scientific community is known as "messing with metabolism." It fails as a strategy precisely because it doesn't look to the root causes, but instead becomes distracted into mapping and tinkering with the details of the immensely complicated dysfunctional state of cellular biochemistry exhibited in age-related conditions. If root causes are left alone to fester and continue to produce any number of downstream issues, then there is very little that can be usefully done to cure such a condition - no amount of tinkering will help greatly.

Brain vascular dysfunction is involved in the etiology of dementias. Cerebrovascular dysfunction is one of the earliest events in these dementias, best exemplified by diminished cerebral blood flow (CBF). A recent study suggested that vascular dysfunction indicated by decreased CBF may be the first abnormal biomarker in Alzheimer's disease (AD) progression, as well as the one that shows the largest magnitude of change. A significant barrier to effective treatments for AD, which are currently unavailable, is that we still do not sufficiently understand the mechanisms that drive its onset and progression. While the neuronal contributions to AD pathogenesis have been extensively studied, cerebrovascular mechanisms of AD, which show substantial overlap with those of vascular cognitive impairment and dementia (VCID), are only partially understood.

The mechanistic/mammalian target of rapamycin (mTOR) may be a critical effector of cerebrovascular dysfunction in AD and potentially other dementias. mTOR is a major signaling hub that integrates nutrient/growth factor availability with cellular metabolism. mTOR also regulates the rate of aging across phyla, including invertebrates and mammals. Rapamycin, an mTOR inhibitor, is the first drug that has been experimentally proven to slow down the rate of aging in mice. Work from our lab and others has identified mTOR as a major regulator of cerebrovascular damage and dysfunction in AD. While mTOR has a critical role in the regulation of cellular metabolism through actions at multiple signaling pathways, some mTOR-dependent mechanisms are uniquely specific to the regulation of cerebrovascular function.

Underlying the CBF reductions observed in AD are decreases in regional and global vascular density. mTOR drives cerebromicrovascular density loss, leading to profound CBF deficits, by decreasing microvascular nitric oxide (NO) bioavailability in brains of mice modeling AD through inhibition of NO synthase (NOS) activity. Therefore, mTOR attenuation with rapamycin induces endothelium-dependent cortical vasodilation via NO release. In agreement with this notion, prior in vitro studies showed that mTOR inhibits endothelial NOS (eNOS) phosphorylation and activation and NO-dependent arterial vasodilation.

, causally implicated in AD, is generated in the brain by cleavage of the amyloid precursor protein (APP) in association with neuronal activation. Aβ is released at synaptic sites into the interstitial fluid. Several physiological mechanisms act to prevent Aβ accumulation, but the largest contributor is transvascular Aβ clearance, as over 85% of Aβ is continuously cleared out of the brain through the blood-brain barrier (BBB). Consistent with a critical role of microvascular integrity and function in Aβ removal from the brain, systemic mTOR inhibition reduces Aβ levels in the brain and improves cognitive function in mouse models of AD. In these AD models, mTOR promotes the accumulation of Aβ in the brain by inhibiting autophagy and by decreasing Aβ clearance as a result of decreased vascular density and reduced CBF.

The BBB is formed by a monolayer of vascular endothelial cells that line the brain microvasculature and dynamically regulate the exchange of molecules. Studies indicate that BBB breakdown is one of the earliest events in the pathogenesis of AD. It was found that mTOR attenuation reduces or prevents BBB breakdown in several models of age-associated neurological disorders, suggesting a broad role of mTOR in BBB dysfunction in age-related brain disease states. The exact mechanisms by which mTOR promotes BBB breakdown, however, have not yet been sufficiently studied.

Rapid increases in blood flow to areas of the brain with high neuronal activity are required to maintain cellular homeostasis and function. This is accomplished through neurovascular coupling, a homeostatic response mediated by complex intercellular signaling events. Significant neurovascular coupling deficits are observed in patients with AD. NO production via activation of the neuronal form of NOS (nNOS) contributes significantly to the neurovascular coupling response by inducing local vasodilation in response to neuronal activation. Dysfunctional neurovascular coupling in mouse models has been reported to occur both from reduced neuronal NO production as well as from a diminished CBF response to otherwise unimpaired NO signaling. Since mTOR is a key driver of cerebrovascular damage and disintegration in several mouse models of AD, it is reasonable to hypothesize that mTOR contributes, at least indirectly, to neurovascular coupling deficits in these models. Very little is known at present, however, about the role of mTOR in the regulation of neurovascular coupling.


Torin1 as an Example of the Search for Better Rapalogs, with a Focus on Autophagy

A sizable portion of the research community interested in intervening in the aging process searches for ways to mimic naturally occurring stress responses, those linked to a slowing of aging in animals. Much of this research in some way involves TOR, the target of rapamycin, and attempts to improve upon rapamycin as a drug candidate to inhibit TOR. TOR is connected to the regulation of autophagy, a cellular housekeeping process known to influence the pace of aging, but also to many other areas of cellular biochemistry relevant to aging. The relevant mechanisms and networks of protein interactions are only partially mapped, and are very complex - progress on that front is slow and expensive.

I point out the open access paper here as an illustrative example, representative of the work of many other scientific groups whose members aim to find and evaluate TOR inhibitors, also known as rapalogs, in search of drug candidates that are better than rapamyin. Better or not, however, it is still the case that this sort of thing is marginal in the grand scheme of what is possible - look at the survival curves in the paper to see how small the effect is in flies, and bear in mind that the effect size for stress response mechanisms diminishes greatly as species life span increases, where the data exists to compare directly. When it comes to what can be gained in terms of increased human life span, modestly slowing aging by activating cellular stress responses compares very unfavorably with rejuvenation strategies based on periodic repair of the molecular damage that causes aging.

Down regulation of the protein kinase TOR is reported to increase lifespan. TOR is highly conserved across eukaryotes and controls several fundamental cellular functions including autophagy - an important and highly conserved cellular repair mechanism. TOR is a major regulator of cellular growth and proliferation and is comprised of two differentially regulated protein complexes TOR complex 1 (TORC1) and TOR complex 2 (TORC2). TORC1 and 2 have distinct substrate specificities and are differentially sensitive to the TOR inhibitor rapamycin. TORC1 promotes anabolism and inhibits catabolism by blocking autophagy. TORC2 is known to be insensitive to rapamycin. Its role in protein synthesis isn't yet clear, though it plays roles in many cellular processes via the AGC kinases and is implicated in keratinocyte survival and cancer development.

The effects of TOR on autophagy are of interest in the context of ageing. It is known for example, that autophagy is naturally down-regulated as a result of normal ageing. The function of autophagy is to repair cellular damage, leading to the suggestion that manipulations that activate autophagy might increase lifespan by maintaining damage surveillance and increasing cellular repair. Consistent with this, over-expression of specific autophagy genes has been shown to extend lifespan in yeast, flies, and human cells. In general, manipulations involving changes to autophagy or autophagy genes are increasingly being reported to be associated with lifespan. Linking the two processes, it has been shown that the specific inhibition of TOR, which in turn activates autophagy, results in extension of lifespan in various species.

The TOR pathway can be inhibited, and hence autophagy activated, by inactivating TORC1 through treatment of cells with rapamycin or via nitrogen starvation. This increase in lifespan due to inhibition of TOR could potentially be via TOR's effects on protein synthesis. However, research on C. elegans suggests a more direct role of autophagy in the modulation of longevity, because inactivating autophagy genes specifically prevents the inhibition of TOR activity from extending lifespan. This finding suggests that the TOR pathway and autophagy act via the same signalling pathway to influence lifespan. However, it should also be noted that inhibition of TOR leads to decreased translation as well as increased autophagy, hence it can be important to distinguish whether either or both pathways are most associated with lifespan effects.

Torin1 is a well-established activator of autophagy via inhibition of the TOR pathway, which inhibits TOR with a higher degree of selectivity than other previously used pharmacological activators, e.g. rapamycin. Part of the mechanism of action of Torin1 is reported to be to suppress the rapamycin-resistant functions of TORC1 that are necessary to reduce autophagy. In addition, unlike rapamycin, Torin1 is reported to inhibit kinase function in both TORC1 and TORC2 complexes potentially giving it greater effectiveness. Torin1 inhibits cell growth and proliferation to a much greater degree than rapamycin and may represent a more effective and specific inhibitor.

In this study we initiated an investigation into the effects on lifespan and reproductive success of Torin1 supplied via the diet, in once-mated and continually mated D. melanogaster females, and on the lifespan of once-mated males. The main finding was that the addition of Torin1 to the diet activated autophagy and led to significant lifespan extension in both sexes. Elevated egg production was observed in females fed Torin1, but overall this did not result in higher overall fertility, owing to higher egg infertility in these females. Hence, there was no evidence for a trade-off between longevity and total fecundity, or between longevity and fertility. Elevated reproduction can lead to damage, which may result in reduced lifespan. Our hypothesis is that the activation of autophagy by dietary administration of Torin1 repairs damage caused by elevated reproduction, potentially minimising trade-offs between lifespan and reproductive rate.


SENS Research Foundation Raises $5 Million, Largely in Cryptocurrency Donations

I'm pleased to note that the 2017 year end SENS Research Foundation fundraiser raised far more than anyone thought was likely - more than $5 million, in fact. This was due to the generosity of a number of high net worth individuals who committed sizable philanthropic donations from their cryptocurrency holdings. These are exciting times for the treatment of aging as a medical condition! Many thanks are due to those people, and to everyone else who supported the continued work of the SENS Research Foundation staff and associated scientific groups to reverse aging through damage repair. We stand upon the verge of a truly massive revolution in medicine, and it is the philanthropists who will get us there.

SENS Research Foundation 2017 Year End Fundraiser Achieves Over $5 Million in Donations

SENS Research Foundation (SRF), a leading Silicon Valley nonprofit focused on diseases of aging, announced today that it received over $5 Million in donations during its year end fundraising campaign. These donations included $1 Million in Bitcoin from the Pineapple Fund; $1 Million in Bitcoin from an anonymous donor; and $2.4 Million in Ethereum from Vitalik Buterin, the cofounder of Ethereum and Bitcoin Magazine.

"SENS Research Foundation is pleased by the strong support we have received from members of the tech community who are innovative leaders in utilizing cryptocurrency. We appreciate their support and look forward to partnering with them going forward. We are very grateful to all of our donors for their incredible support of our Year End Campaign. Our initial campaign goal was $250,000. We were thrilled to receive over 1400 donations totaling over $5 million in just ten weeks. Achieving this level of donation in such a short period of time shows that the momentum SENS Research Foundation has achieved is continuing to accelerate. We are looking forward to engaging even more of the tech community in our work and to continue to accelerate our progress through the expansion of our research programs. Their support makes this growth possible."

On this topic, I have a pet theory regarding wealth and its use to change the world. Historically, people who became extraordinarily wealthy have done so only after many years of work on projects that they were deeply invested in for the sake of the work, not for the sake of financial reward. Consequently they had no real idea regarding what to do with that wealth, other than to keep on moving forward in the shape that they had carved out for their lives prior to that enrichment. They became one with the process that brought them to where they were. Further, these were usually older people by that point, come to terms with the human condition, more comfortable with the world as it is, not as a younger and more fiery individual would have it be. Not everyone is worn down to acceptance - look at the large-scale, results-oriented philanthropy of Bill Gates, for example - but I think it is definitely the case that vision is often one of the early casualties of aging, and the advent of personal wealth doesn't change that situation for any given individual. For every Bill Gates there are another twenty billionaires who fail to change the world in any significant way beyond the ventures that earned them their fortunes.

Cryptocurrencies, the first application of blockchain technologies, have resulted in a sizable number of people who have become enormously wealthy in a much shorter period of time, and at younger ages, than has typically been the case in the past. Even the dotcom bubble era and its immediate sequels didn't reach these levels of youthful enrichment, and that produced a fair number of people young enough and wealthy enough to set forth to remake sections of the world in the service of loftier agendas. They escaped being shaped by the processes of their enrichment to a great enough degree to retain fire and vision. Consider the willingness to put capital towards world-changing futurist ideals exhibited by Elon Musk, Peter Thiel, Mark Zuckerberg, and Sean Parker, to pick a few. But while that generation of high net worth individuals have certainly supported the life sciences, and in Peter Thiel's case SENS rejuvenation research, they largely haven't followed Thiel's support for the goal of treating aging as a medical condition, and Thiel himself has certain not gone all-in. He hasn't followed the logic further towards its end, in that the only rational use for excess capital in this age is to develop viable treatments to reverse aging. When you can buy time with money, and not just for yourself, but for everyone, then that is the rational thing to do.

The wealthy of the blockchain community may well proceed differently. The times are different, for one, as rejuvenation research after the SENS model of damage repair is more broadly known and accepted nowadays. The technology industry of the Bay Area, still in many ways the spiritual center of modern software engineering and invention, includes a great many supporters of SENS, the Methuselah Foundation, and the SENS Research Foundation, and that number has grown considerably over the past fifteen years. Aging is an engineering problem, SENS is a set of repairs and a set of outlines for repair technologies, and engineers grasp that readily. It isn't a coincidence that there are so many engineers, software and otherwise, to be found participating in the past fifteen years of philanthropy to support progress in rejuvenation research, work based on periodic repair of the cell and tissue damage that causes aging. Now it is the case that many of those engineers in the cryptocurrency space are both young and suddenly wealthy, people who have not been worn down to an acceptance of the world as it is, have not become one with their process of enrichment. They are still willing to consider radical change to the status quo, full of the fire of success, and equipped with sufficient resources to push forward the research and development that they would like to see happen. Exciting times, as I said.

Delivering Microglia-Like Cells to the Brain to Break Down Amyloid-β

The future of cell therapies might prove to be one in which transplants are largely done away with. Cell engineers will instead issue a carefully controlled set of signals that cause the body to generate the desired additional population of cells, move those cells to where they are needed, and then put them to work in a specific way. We stand a long way removed from the full realization of this sort of treatment, not least because the signaling environment of most tissues is still largely terra incognita when it comes to the fine details, but the research noted here is certainly a start along that road.

For brain microglia struggling to keep amyloid plaques under control, help could be on the way. Researchers have identified an antibody that triggers mouse bone marrow myeloid progenitors to become phagocytic microglia-like cells, which then make their way to the brain. In a mouse model of Alzheimer's disease (AD), the cells clustered around amyloid deposits and reduced plaque load.

The findings grew out of a problem seen with stem-cell therapies - it's not enough to generate the desired type of cell; the cells also must be directed to where they are needed. "After embryogenesis, the 'go there' part is shut down. Controlling migration is the other half of stem-cell therapy." To address that, researchers devised a screen for antibodies that induce stem cells to not only differentiate but also migrate to different tissues. After expressing antibodies on bone-marrow stem cells, researchers put those cells in mice and looked for the ones that gained the ability to migrate to the brain or other tissues. "In a normal selection, you look at a cell population and find something that's different. In this migration-based selection, the cells self-purify because they run away from the bone marrow, and take up residence in other tissues."

Researchers started with a lentivirus expression library comprising 100 million different single-chain antibody genes. They infected freshly isolated mouse bone-marrow cells with the library, then transplanted the entire batch of infected cells into mice whose own bone marrow had been destroyed by whole-body irradiation. After a week, they used PCR to detect traces of the antibody genes in different tissues. Of 60 different genes detected, they found one, dubbed B1, six times in brain tissue from different mice, and never in spleen, liver, or heart.

To ask if the microglia-like cells attack amyloid in vivo, the researchers repeated their transplantation experiments using APP/PS1 mice. They infused B1-transduced bone marrow cells into irradiated eight-week-old animals, and then waited. After six months, the B1 mice harbored approximately 60 percent less amyloid in their brains than animals transplanted with control bone marrow. The animals also had more microglia and fewer astrocytes than irradiated controls. Does B1 treatment induce bona fide microglia and if so, what type? This is difficult to evaluate. "I don't think these cells are the real deal, but I don't care. If, as claimed in the study, this antibody induces a type of cell that can migrate to plaque in non-irradiated mice, that's important. If this is associated with plaque removal, that's huge. Whether the cells become microglia is not as important."


An Example of the Need for Research and Development Investment in Cryonics

Cryonics is a field that requires commercial success of some form for further expansion, such as in the reversible vitrification of organs, not least because either that or wealthier patrons than presently exist will be needed as a source of significant funding to improve current methodologies of preservation. The recent report from Alcor noted here illustrates the well-understood need for this sort of technical improvement. Alcor presents comparatively unfiltered reports on cryopreservations, where patients agree to it, and the staff and patients should be commended for this. Such reports are important to the quality of an industry, and open organizations are certainly better than closed ones.

It is arguably the case that the biggest hurdle today when it comes to obtaining an optimal cryopreservation is the illegality of assisted euthanasia, a state of affairs that forces the industry into the form of a standby and emergency response service. That makes it both expensive and challenging to achieve a high-quality cryopreservation immediately after clinical death, as a sizable fraction of deaths in late life are unexpected in their timing. When euthanasia becomes more broadly legal and accepted, however, it will then be the case that technical limitations such as access to blood vessels in stroke victims will become the biggest immediate hurdle. It is easy to envisage ways around that problem, and the more sophisticated apparatus, the better tools to get at the blood vessels of the brain at multiple points so as to introduce cryoprotectant in a controlled way during cooling. While cryonics remains a non-profit and comparatively resource poor industry, this sort of technology remains out of reach - which is why some form of commercial success is needed, to enable bootstrapping to the next level of operation.

As the example here illustrates, even when the patient's terminal decline is slow enough to organize a preservation immediately following clinical death, there are forms of death, such as those resulting from stroke, in which modern methods of vitrification cannot be used because the state of the art in the industry isn't yet advanced enough to work around significant blood vessel blockage in the brain in a cost-effective way. Vitrification requires introduction of cryoprotectant into the vascular system of the brain, and that cannot be done haphazardly. So by commonplace bad luck, the patient obtains a preservation that will introduce significant ice crystal formation and consequent tissue damage, rather than the vitrification intended to minimize that issue. That adds to the bad luck of having suffered earlier damage to the brain due to stroke and its consequences. These are all challenges that could be addressed giving meaningful investment into cryonics.

Alex Arevalo, a public, neuro member, was pronounced on October 20, 2017 in Tucson, Arizona and became Alcor's 153rd patient the same day. Alcor received an emergency text on October 20th just before 10:00 (all times are Mountain Time in 24-hour format). We were alerted that Alex Arevalo was suffering from a stroke. He had a previous stroke in January of 2017. Contact was made with Peggy, his wife. She stated he was unable to speak or to move his right hand, and suffered from right-sided facial droop. They were currently located in Las Cruces, NM and he was being transported to the closest stroke center in Tucson, AZ.

Josh Lado, Director of Medical Response, was traveling to Tucson that morning on personal business. He traveled to the hospital to which Alex had been flown and made contact with the attending physician in the Emergency Department. She stated that they had performed a CT scan and she didn't believe that the patient's brain was receiving any significant blood flow. The patient had suffered a hemorrhagic stroke at the brain stem. Josh called Alcor's Chief Medical Advisor, Dr. Harris to inform him and determine the best course of action.

Dr. Harris and Josh agreed that the patient should be taken off ventilation immediately to allow legal death by cardiopulmonary criteria to occur. He was extubated at 13:50. Josh called Dr. Harris and the decision was made not to perform any cryoprotectant perfusion once the patient was at Alcor and to perform a straight freeze. This decision was made because of the inability to perfuse the brain due to the hemorrhagic stroke and associated warm ischemia that had already occurred, and the chance that added pressure would cause more damage inside the patient's brain. Alex's vital signs significantly changed at 18:57 as his heart rate decreased, rhythm changes occurred, blood pressure spiked, and oxygen levels dropped significantly. Legal death was declared at 19:18. Alex had ice placed around the head and neck and preparations began for transport. Once paperwork was finished, hospital staff helped move the patient to the transport vehicle and assisted in moving him into the Ziegler case.

Four bags of ice were placed in the case to precool the metal box. 35 pounds of ice was added around his entire body. This was to ensure the ice wouldn't melt by the first stop just outside of Tucson. The patient left the hospital at 20:11 to head back to Alcor. The first stop to check for ice was at 20:36, and five pounds of ice was added. The second stop was at 21:33 and 5 more pounds were added. The reason for making two stops for ice was the limited space around the head for ice, between the wadded body bag corners and the case having 45 degree corners at head and foot. There was plenty of ice but Josh wanted to ensure continued cooling. The patient arrived at Alcor just after 22:30. Surgery was performed for neuro separation and cool down began right away.


Recent Papers on the Mitochondrial Contribution to Aging

Mitochondria are the power plants of the cell, a herd of self-replicating structures evolved from ancient symbiotic bacteria, now fully integrated into the cell. Their primary task is the production of chemical energy stores, an energetic process that produces damaging reactive molecules as a side-effect. Much of the original bacterial DNA of the distant ancestors of today's mitochondia has migrated to the cell nucleus, leaving only a tiny remnant genome in the mitochondria themselves. When looking across species with widely divergent life spans, researchers have found good correlations between species life span and some combination of mitochondrial activity (metabolic rate) and mitochondrial composition (how resilient mitochondria are to oxidative damage). This strongly suggests, independently of the copious other evidence, that mitochondria are important determinants of aging and longevity.

There are numerous ways to look at the complexities of the mitochondrial contribution to aging, and until specific repair technologies successfully reverse that contribution, the degree to which different age-related changes in mitochondria are more or less relevant to aging will continue to be a topic of active debate and exploration. In the SENS viewpoint, damage to mitochondrial DNA is most important as a primary cause of aging. It occurs either during replication or as a result of damage from reactive molecules, and can produce mitochondria that are both faulty and able to replicate more readily than their peers. Cells become taken over by broken mitochondria, and become broken themselves, producing a flood of damaged and damaging molecules that contribute to age-related conditions. On the other hand, the more mainstream research community focuses on the general malaise that affects mitochondria in old tissues, characterized by reduced energy store creation, altered dynamics of fusion and fission, and other structural changes. In the SENS view, this is probably a secondary or later consequence of other forms of cell and tissue damage.

Of the two open access papers here, the first is a general, high-level review of mitochondria in aging that paints a picture of a field in flux, moving away from established theories of past decades now proven unhelpful, but not yet entirely sure of the direction for the future. The second examines the topic of how mitochondrial DNA damage originates. There is considerable debate over whether the primary cause is DNA replication errors or the activities of reactive molecules - such as those generated in large amounts by the mitochondria themselves. This paper argues for replication errors to be the important cause, and particularly important in stem cell populations, there contributing to the age-related decline in stem cell activity. The cause of errors, while certainly interesting, is actually not all that relevant to any of the near-term potential methods of repairing or working around the problem. If there is a way to reliably fix mitochondrial DNA in near all cells, or replace it, or provide backup copies of the proteins produced from that DNA blueprint, then it doesn't matter how the damage happened.

The Aging Mitochondria

On average, a healthy person lives 80 years and one of the highest risk factors known for most human diseases and mortality is aging. Many evolutionary and mechanistic theories have been elaborated on, trying to explain why and how living organisms age. However, from a mechanistic point of view, among all the theories, those that see mitochondria as main actors occupy a particular place. Indeed, mitochondria have been at the center of one leading hypothesis for 50 years: the free radical theory. Even though the scientific community has shifted to a more complex view to explain aging, embracing a network of events, mitochondria remain of high importance because of their central position in cell homeostasis of almost every tissue. Thus, as far as the description of molecular and cellular mechanisms are concerned, mitochondria have been shown to participate in every main aspect of aging: decline of stem cell functions, cellular senescence, "inflammaging," and many others.

Mitochondrial alterations have been extensively described in aging tissues of many organs for a long time. It has been particularly studied in muscle and heart, and sarcopenia and heart failure are two main causes of physical decline in the elderly. In particular, in these two tissues, but also in others like liver, brain and adipose tissue, mitochondrial alterations during aging are multiple. In particular, the number and density of mitochondria, as well as mitogenesis, have been showed to be reduced, whereas for mitochondrial dynamics and content contradictory inconclusive results have been reported. Importantly, mitochondrial function has been regularly reported to be impaired in different aging tissues, in terms of ATP production and respiratory chain (RC) capacity/activity.

A key reported feature of aging mitochondria was the increase in somatic point mutations and large deletions in the mitochondrial DNA (mtDNA). Interestingly, these mtDNA mutations have been shown to be responsible for mitochondrial dysfunction. Since mtDNA is located very close to the major source of reactive oxygen species (ROS), oxidative damage has been considered the main cause of mutations in mtDNA. Indeed, the Mitochondrial Free Radical Theory of Aging (MFRTA) considers the oxidative damage of mtDNA as the primary event affecting RC proteins, inducing its dysfunction and increasing ROS production in a vicious cycle. Yet, this theory has been strongly challenged and the scientific community has had to adjust working hypotheses to fit with a more complex mitochondria-centered network of aging mechanisms.

Proliferation Cycle Causes Age Dependent Mitochondrial Deficiencies and Contributes to the Aging of Stem Cells

Besides the nuclear genome, a typical animal cell also has from 100 to 1000 copies of mitochondrial DNA (mtDNA) that encode core subunits of electron transport chain complexes. While converting energy to ATP and carrying out biosynthesis, mitochondria also generate free radicals that can damage DNA, proteins, and lipids nearby. The mitochondrial genome has no histone protection and lacks efficient repair mechanisms. As a result, mtDNA is particularly prone to accumulating mutations. To make matter worse, inefficient electron transport chain (ETC) complexes produced by mtDNA mutations generate more free radicals and exacerbate the mitochondrial damage in a feed-forward cycle.

Accumulation of mtDNA mutations during lifetime has been postulated to cause age-related decline of energy metabolism and impairment of tissue homeostasis. Mitochondrial "mutator" mice with an elevated rate of mtDNA mutagenesis display premature aging, which, in principle, substantiates the correlation between mtDNA mutations and aging. However, mtDNA mutations from various tissues of normally aged human or experimental animals are found to be too low to possibly elicit any pathological consequences, which argues against a causative role of mtDNA mutations in physiological aging, particularly in post mitotic tissues.

DNA replication is a source of mutations. In adulthood, most tissues consist of post mitotic cells that have a slow turnover rate of mitochondria and mtDNA, which might explain the low mtDNA mutation frequency in post mitotic tissues. Therefore, the quest for connection between mtDNA mutations and aging might have focused on the wrong target from the very beginning. On the other hand, one would expect that mtDNA mutations in actively dividing cells, such as cancer cells and stem cells, could reach a high level during the aging process. In fact, there is increasing evidence demonstrating the accumulation of mtDNA mutations in aged stem cells. Stem cells are essential for tissue homeostasis and wound repair. Age dependent deterioration of stem cells contributes to several hallmarks of aging such as impaired capability of tissue repair and increased susceptibility to cancers and infectious diseases, and thereby has been proposed to play an important role in the natural aging process.

In current study, we utilized a physiological approach to manipulate the germline stem cell (GSC) division cycle independently of chronological age in flies, and examine its impact on GSC aging and female reproductive physiology. We demonstrated that the accumulation of division cycles played a major role in maternal age dependent decline of eggs' fitness and contributed to the age dependent decline of female fecundity. Additionally, we detected increased mutations on mtDNA and observed impaired mtDNA replication in aged ovaries. The strong correlation between the decline of stem cell activity and mitochondrial dysfunction in aged ovaries suggests that mtDNA mutations caused by proliferative cycles may contribute to stem cell aging.

Quercetin is Probably Not a Useful Senolytic

Senolytic compounds are those that preferentially destroy senescent cells. Since these cells are one of the root causes of aging, there is considerable interest in finding and then quantifying the effectiveness of senolytic compounds. The known and alleged senolytics vary widely in effectiveness and quality of evidence, and quercetin is one of the more dubious examples. I don't think that anyone expects quercetin, on its own, to have a useful level of impact on senescent cells and their contribution to degenerative aging. The study here comes to the plausible conclusion that quercetin really can't achieve that goal. Yes, it is true that the 2015 mouse study of the chemotherapeutic dasatinib and quercetin demonstrated that the two together cleared more senescent cells than dasatinib alone, but synergy with other compounds is a very different story from unilateral effects. Quercetin is a widely used and extensively tested supplement compound. Any significant effect on health resulting from quercetin alone would likely have been discovered many years ago.

Previously, quercetin was reported to be a senolytic in irradiation-induced senescent human umbilical vein endothelial cells (HUVECs). HUVECs are derived from the umbilical cord of newborn babies, and for a long time were the only model of primary human endothelial cells (EC); however, these cells are not the best model of diseases associated with human arterial aging. HUVECs have been shown to differ substantially from primary endothelial cells derived from adult human vasculature. In the current study, we investigated whether quercetin is a senolytic in adult EC, and evaluated whether quercetin 3-D-galactoside (Q3G; hyperoside) would be a more selective senolytic.

Quercetin's low therapeutic/toxic ratio in the HUVEC study raised the possibility that quercetin could significantly injure non-senescent cells. It was unclear whether the proliferation of non-senescent cells could be compensating for some of the quercetin-mediated cell death, thus masking its toxicity to the young cells at the lower concentrations found to be selectively cytotoxic to senescent cells. We used adult human coronary artery endothelial cells (HCAEC), which are microvascular cells, as a relevant model, and generated two groups of cells from them to better understand the effect of quercetin: EP (early passage; young) and SEN (senescent), as a model of an aging tissue.

Our key findings are that quercetin at a concentration that reduced SEN EC also caused significant EP EC cell death, and that there was no evidence of senescent cell-specific cell death mediated by quercetin. Thus, quercetin is not a selective senolytic in adult human arterial endothelial cells, where both EP and SEN cells responded similarly to quercetin's toxicity.

To circumvent quercetin's toxicity on healthy, non-senescent cells, we investigated Q3G, a derivative of quercetin with limited toxicity to endothelial cells, which is processed by senescence-associated beta-galactosidase (SABG) enriched in senescent cells to release quercetin in situ. Q3G could act as a selective prodrug in senescent cells. However, Q3G had no significant toxicity to either EP or SEN EC. The lack of Q3G's toxicity in the current study may be due to Q3G being unable to enter the beta-galactosidase-rich lysosomes, or alternatively, Q3G being able to translocate to the lysosomes to release quercetin, which is further processed into an inert compound.


An Attempt at Using Protein Levels Rather than Epigenetic Patterns to Build a Biomarker of Aging

The current best candidates for a sufficiently robust biomarker of aging are based on patterns of DNA methylation, epigenetic markers that control the pace at which specific proteins are produced, and which are constantly shifting in response to circumstances. The best of these epigenetic clocks have degrees of error in assessed age that are five years or less, depending on implementation. The researchers here have chosen to investigate patterns of protein levels in blood rather than epigenetic markers, in part driven by economic considerations, as the needed tools of biotechnology are more mature and less expensive. They use modern computational techniques to try to build useful biomarker algorithms through an analysis of raw data obtained from large numbers of people at various ages. Their efforts result in a degree of error of around six years, which might be taken as encouraging; it may well be possible to do better via this method.

To perform this study, we trained a series of deep neural networks on anonymized blood tests for patients from three distinct ethnic populations: Korean, Canadian, and Eastern European. We compared the predictive accuracy of our deep learning models first when trained using population-specific data, and then when using a combined and ethnically-diverse dataset that includes patients from all three patient populations. We used the same feature space of 20 blood biochemistry markers, cell counts, and sex to train three separate deep networks on three specific ethnic populations.

We present several novel hematological aging clocks. The best-performing predictor achieved a mean absolute error (MAE) of 5.94 years having greater predictive accuracy than the best-performing predictor of our previously-reported aging clock (which achieved an MAE of 6.07 years), despite being trained on a narrower feature space (21 compared to 41 features). These results are in line with the hypothesis that ethnically-diverse aging clocks have the potential to predict chronological age and quantify biological age with greater accuracy than generic aging clocks. Furthermore, they have a greater capacity to account for the confounding effect of ethnic, geographic, behavioral and environmental factors upon the prediction of chronological age and the measurement of biological age.

Albumin, glucose, urea, and hemoglobin were among the most important blood biochemistry parameters for all three population-specific predictors. Albumin is the most prevalent protein in blood and its primary function is the regulation of oncotic pressure, which is critical for transcapillary fluid dynamics, and hypoalbuminemia is often associated with malnutrition, liver disease, injury, chronic inflammation and the aging process. Blood glucose levels, on the contrary, tend to increase with age, and glucose is able to modify proteins via irreversible glycosylation, a feature that is directly associated with the aging process. Levels of serum urea also increase with age, which is associated with age-related decrease in muscle mass. Age-related decreases in hemoglobin is common in the elderly, a condition that increases the risk of cardiovascular disease, cognitive decline and an overall decline in quality of life.

Our hematological clock is consistent with what is already known about the biology and pathophysiology of aging. While the blood parameters are not accurate biomarkers of aging by themselves, when analyzed in combination they can be used to reasonably accurately predict chronological and biological age. Deep learning based hematological aging clocks, even when trained on a limited feature space, demonstrate reasonably high accuracy in predicting chronological age.


Heart Muscle Patches as a Vehicle to Improve Cell Engraftment and Survival

Heart muscle patches are thin engineered sections of tissue, lacking blood vessels because construction of microvasculature is still an unsolved challenge, and small because without blood vessels there is a size limit on engineered tissue. The study here suggests that we should be thinking of a present-day heart muscle patch, and most of its structure and cells, as a disposable vehicle to deliver only a fraction of its cells, keeping them alive long enough to engraft alongside native cells. The rest of the cells in the patch last only long enough to temporarily change the balance of signaling in an aged or injured heart. That signaling ensures that native cells alter their behavior, and it may be those cells, rather than the surviving new arrivals, that perform most of the work needed to produce some form of regeneration or lasting benefit.

It is the case that most types of modern stem cell therapy work via the beneficial signals produced by the transplanted cells in the short time before they die. Comparatively few classes of cell therapy deliver cells that stick around to some degree, engrafting and prospering in the patient, and these are largely the older, more established transplant therapies. Obviously there is a continuum between all of the transplanted cells dying rapidly and most cells engrafting to become productive members of the local population, and the research community is working its way along that line, tissue by tissue. The technology demonstration here is an improvement over past work on heart tissue, but at 10% engraftment there is clearly a way to go yet when it comes to building better approaches. Cells are fragile.

In the near future, the development of regenerative medicine for each tissue type is likely to split into two quite different approaches, a first that gives up on cells and just delivers the signals, assuming progress in the mapping and categorization of those signals, and a second that works towards more reliably replacing worn and malfunctioning native cells with new cells that survive the transfer process in large numbers. The former will most likely happen first, given that numerous research groups have been working on it for some years now, but the latter is far more relevant to human rejuvenation. The research community will need to be able to reliably replace cells of many types in order to achieve the SENS vision of repair of cell loss and atrophy. Simply adjusting the signaling to try to override the age-related reaction to cell and tissue damage is limited in the benefits it can achieve, even while those benefits can look impressive in comparison to past medical capabilities.

Heart-muscle patches created from human cells improve recovery from heart attacks

Large, human cardiac-muscle patches created in the lab have been tested, for the first time, on large animals in a heart attack model. Each patch is 1.57 by 0.79 inches in size and nearly as thick as a dime. Researchers found that transplanting two of these patches onto the infarcted area of a pig heart significantly improved function of the heart's left ventricle, the major pumping chamber. The patches also significantly reduced infarct size, which is the area of dead muscle; heart-muscle wall stress and heart-muscle enlargement; as well as significantly reducing apoptosis, or programmed cell death, in the scar border area around the dead heart muscle. Furthermore, the patches did not induce arrhythmia in the hearts, a serious complication observed in some past biomedical engineering approaches to treat heart attacks.

Each patch is a mixture of three cell types - 4 million cardiomyocytes, or heart-muscle cells; 2 million endothelial cells, which are well-known to help cardiomyocytes survive and function in a micro-environment; and 2 million smooth muscle cells, which line blood vessels. The three cell types were differentiated from cardiac-lineage, human induced pluripotent stem cells, or hiPSCs, rather than using hiPSCs created from skin cells or other cell types. Each patch was grown in a three-dimensional fibrin matrix that was rocked back and forth for a week. The cells begin to beat synchronously after one day.

Past attempts to use hiPSCs to treat animal models of heart attacks - using an injection of cells or cells grown as a very thin film - have shown very low rates of survival, or engraftment, by the hiPSCs. The present study had a relatively high rate of engraftment, 10.9 percent, four weeks after transplantation, and the transplantation led to improved heart recovery. Part of the beneficial effects of the patches may occur through the release of tiny blebs called exosomes from cells in the patches. These exosomes, which carry proteins and RNA from one cell to another, are a common cell-to-cell signaling method that is incompletely understood. In tissue culture experiments, the researchers found that exosomes released from the large heart-muscle patches appeared to protect the survival of heart-muscle cells.

Large Cardiac-Muscle Patches Engineered from Human Induced-Pluripotent Stem-Cell-Derived Cardiac Cells Improve Recovery from Myocardial Infarction in Swine

Here, we generated human cardiac muscle patches (hCMPs) of clinically relevant dimensions (4 cm × 2 cm × 1.25 mm). The hCMP matures in vitro during 7 days of dynamic culture. The hCMPs began to beat synchronously within 1 day of fabrication, and after 7 days of dynamic culture stimulation, in vitro assessments indicated the mechanisms related to the improvements in electronic mechanical coupling, calcium-handling, and force-generation suggesting a maturation process during the dynamic culture.

In vivo assessments were conducted in a porcine model of myocardial infarction (MI). The engraftment rate was 10.9±1.8% at 4 weeks after the transplantation. The hCMP transplantation was associated with significant improvements in left ventricular (LV) function, infarct size, myocardial wall stress, myocardial hypertrophy, and reduced apoptosis in the peri-scar border zone myocardium. hCMP transplantation also reversed some MI-associated changes in sarcomeric regulatory protein phosphorylation. The exosomes released from the hCMP appeared to have cytoprotective properties that improved cardiomyocyte survival. The hCMP treatment is not associated with significant changes in arrhythmogenicity.

ZIPAR Staff Consider the Consequences of Engineering an End to Aging

The folk at ZIPAR, the Zurich Institute of Public Affairs Research, have academic futurist interests somewhat analogous to those of the Future of Humanity Institute (FHI) in the UK, though with more of a short-term horizon and consequent consideration of what some might consider fiddly, unimportant policy details. If the true legacy of the FHI and its network is to give rise to many peer organizations, where an increasing number of people put time into thinking seriously about the future of technological progress and radical enhancement of the human body and mind ... well, there are certainly worse legacies than that. It might be regarded as one facet of the later stages of the quiet, sweeping victory of the past generation of futurist and transhumanist thought, in which it becomes a field of policy academia, at the same time as the first transformative technologies are implemented in order to remove limits on the human condition.

Technology is intertwined with epistemic progress: technology is the practical application of knowledge and skills obtained through rational inquiry, and in turn, technology allows us to further our rational understanding of the world. However, technology is more than just the product of and the means to a more accurate and a more complete understanding of the world. Technology allows us to do things that are beyond the natural limits of our biology. For the most part, we do not think much about this property of technology. When we ride a bicycle, for example, we are using a piece of technology that allows us to go from A to B in a much more efficient way than by going on foot.

Sometimes, however, transcending the limits of human biology via technology does not only raise eyebrows, but widespread concerns. Most people intuitively accept most ways in which technology changes or completely removes biological limits. Some biological limits, however, seem to be off-limits, so to speak. One such limit is the finite natural lifespan of humans: death is a natural part of life, and trying to end natural death might seem outlandish. Our visceral response to the idea of ending death, of course, is little more than status quo bias coupled with a variant of the is-ought-fallacy. Whether something is morally desirable is not determined by whether it is the status quo.

Ending natural biological death has a number of benefits that go beyond the intuitive idea that not existing feels weird. We humans are systematically irrational in many domains, due to our cognitive biases. One such domain is the assessment of risks. One source of our biased risk perception is our natural life cycle. Things that will happen some time in the future matter less to us than things that will happen immediately, simply because there is uncertainty about the future. If we end natural biological death, then we are radically changing our future prospect. We are not trying to imagine a world in which we do not exist anymore, but we are instead thinking about a future world that is some time off, but that we will be part of nonetheless. Such a radical shift in perspective might help alleviate some problems of the present bias.

Our biased time-preferences are not only present in the domain of risk perception, but also in the ostensibly simple domain of planning ahead. Ending natural biological death through rejuvenation could have a positive impact on our long-term planning capabilities. From an individual, micro-level perspective, knowing that the long-term future (in terms of traditional human lifespan) is not some uncertain world that one might not even live to see, but instead a state of the world that will come about in due time, might nudge individuals towards automatically correcting some of their planning biases. After all, if I know that 50 years into the future, I will still be physically the same as I am now, thanks to rejuvenation, then I might think more carefully about the decisions I make today that might affect me in the future.

Humans are capable of remarkable rationality, both in the sense of epistemic as well as instrumental rationality. Unfortunately, all sorts of "afflictions" prevent us from realizing our rational potential to the fullest. There are two ways in which an end to natural death could cumulatively increase individual rationality levels. First, active epistemic engagement by individuals would have a positive effect. Increasing human lifespan (potentially practically indefinitely) would mean that humans would experience changes in the world of the kind that was previously observable only on an intergenerational level. The second way in which the end of natural death might result in cumulatively higher rationality is accidental experience. The longer a person lives, the more probable it is that some strongly held belief will be accidentally challenged. Accidental contact with members of the outgroup can challenge our beliefs and reduce intergroup bias.

Most people fear death, or at least feel uneasy about death. Fear of death is a unique feeling that is, at once, both perfectly understandable and irrational. Ending natural biological death would mean removing death dread, either completely or to a large degree. Fear of death is probably one of the most unpleasant negative feelings because, contrary to almost all other causes of negative feelings, we cannot do anything about death (yet). Death dread is an unnecessary, cruel burden of nature; humankind loses nothing by getting rid of it.

But our lives do not consist only of the search for ways of higher-order progress. In our lives, there are many things that we simply enjoy. Enjoying things means that, every day and mostly without being fully aware of it, we experience some form or another of pleasure. Experiencing pleasure is something we value on an individual level, but it is also a general moral goal. Ending natural biological death could increase the amount of pleasure people experience. One reason why is obvious: The longer a person lives, the more pleasureable experiences can she or he have. But there is also a second reason why doing away with natural death would have a positive impact on pleasure: Technological and social progress. One of the most notable effects of technological and social progress is that it makes human life more pleasurable, in all kinds of ways.

Creating as much pleasure for as many people is a classical utilitarian goal, but pleasure is only one side of the utilitarian medal. The other, and perhaps more important moral aspect of existence is suffering. All things being equal, we should reduce suffering for as many people as much as possible. Ending natural death would reduce would almost certainly have a great positive impact on reducing suffering. Human morbidity is compressed towards later stages in life. Ending natural death through rejuvenation would mean avoiding the stage of compressed morbidity altogether, and with it, avoiding a lot of suffering associated with afflictions that are likely in later life stages. If we assume diagnostic and therapeutic medical treatments to advance in the future, then the overall suffering caused by disease will gradually approach zero. This means that people who live beyond their natural biological age limit will experience less and less disease-induced suffering the longer they live.

In conclusion, death is a natural part of human existence, but human progress is essentially a story of overcoming undesirable natural limits. In the near future, technological progress might make it possible to stop natural biological death. Should humankind embrace such technology? Yes: Even though such technology would not be without risks, the risks are almost certainly manageable. The benefits of ending natural death, on the other hand, are immense. Death is an obstacle that is slowing down human progress. If we remove that obstacle, humankind could increase the speed of both its moral and its epistemic progress.


BMP4-Generating Endothelial Cells Spur Regeneration of the Thymus

The research community is interested in regeneration and tissue engineering of the thymus, as this could in principle resolve one of the causes of age-related decline in immune system function. It is worth keeping an eye on present efforts, such as the one noted here, at an early stage of exploration. The thymus is where cells of the adaptive immune system mature, and is thus one of two important gating factors determining the pace at which new immune cells enter the body, ready for action. The other is the quality and activity of the hematopoietic stem cell population in the bone marrow, where immune cells are created.

The thymus is very active in childhood, but in early adulthood much of the specialized tissue - that hosts immune cells as they mature - atrophies to be replaced by fat. The remaining portion of that tissue fades away more slowly over a lifetime, and the pace at which new immune cells arrive fades with it. A sizable part of the failure of the immune system in later life derives from the ever slower pace at which immune cells are introduced. Malfunctioning, exhausted, and senescent immune cells accumulate. The immune system is eventually overwhelmed by the wear and tear of its duties, its component parts not replaced often enough. Restoring the active portions of the thymus to a youthful size has been shown to help in mice, and the hope is that it will do the same in humans.

The thymus, an organ in the lymphatic system, plays a critical role in immune function, producing the T cells essential to the immune response. The thymus, which gets smaller as we age, is highly sensitive to damage from stress and infection. And while it can recover from such insults - the process is known as endogenous thymic regeneration - more serious injury, for example, from chemotherapy or radiation, can extend recovery time considerably. That can result in an increased susceptibility to infections and even cancer relapse in patients while their T-cell count is low. "We don't really understand why the thymus shrinks as we get older, or how to make it bigger in patients where it would likely be helpful to have T cells be made."

That the thymus can regenerate itself has been known for nearly a century, but the mechanisms that control this process have not been widely studied. So researchers performed a transcriptome analysis of a section of the mouse thymus following damage from total body irradiation (TBI). They found a suite of genes that were significantly upregulated, including several already known to be involved in thymic function, as well as Bmp4. "We're really interested in understanding these processes of endogenous regeneration so that we may exploit them into clinically relevant and innovative strategies to boost thymic function."

The researchers treated mice with a BMP inhibitor starting one day before TBI to determine whether BMP signaling is necessary for endogenous regeneration. The treated mice had significantly worse recovery than controls, indicating BMP's importance in the process. In a related experiment, the researchers then injected endothelial cells into the bloodstreams of mice 72 hours after TBI, and found that doing so increased the number of thymic cells compared to controls. When they injected the cells directly into the thymus, 100-fold fewer endothelial cells were required to result in the same capacity for endogenous regeneration than when they injected them intravenously. This suggests that some endothelial cells from the bloodstream do make it to the thymus, they wrote in their report.

Therapies based on the research would be more likely to use isolated BMP4 than an endothelial cell line. Another future interesting direction would be whether this same pathway could be used in the aging thymus. In this scenario, or in damage associated with chronic conditions, perhaps boosting BMP4 activity would also drive thymic regeneration.


How to Plan and Carry Out a Simple Self-Experiment, a Single Person Trial of Chemotherapeutic Senolytic Drug Candidates

This lengthy post walks through the process of setting up and running a self-experiment - a trial of one - of candidate senolytic drugs capable of removing some portion of the senescent cells that accumulate with age to cause aging and age-related disease. Metrics are assessed beforehand and afterwards in order to shed some light on whether or not it worked, in the sense of producing some degree of rejuvenation, turning back specific measures of age-related decline.

The outline here is optimized for simplicity, cost, and ability to conduct the experiment without much outside assistance, rather than for maximal effectiveness. There are better candidate pharmaceuticals and better metrics that those settled on here, at least from the point of view of likely effectiveness, fewer side-effects, and relevance to the task at hand, but they require more work, more funds, more complicated logistics, and the assistance of laboratories and physicians. Given these self-imposed constraints, this does mean that the outline here ends up focused on repurposed chemotherapeutics, which make up the majority of the current senolytic drug candidates. That in turn means that side-effects and related risks to health are an important consideration.

The purpose in publishing this outline is not to encourage people to immediately set forth to follow it. If you come away thinking that you should do exactly that, and as soon as possible, then you have failed at reading comprehension. This post is intended to illustrate how to think about self-experimentation in this field: set your constraints; identify likely approaches; do the research to fill in the necessary details; establish a plan of action; perhaps try out some parts of it in advance, such as the measurement portions, as they never quite work as expected; and most importantly identify whether or not the whole plan is worth actually trying, given all that is known of the risks involved. Ultimately that must be a personal choice.


Why Self-Experiment with Senolytics?

Senolytic therapies are those that selectively destroy senescent cells. The build up of senescent cells is one of the causes of aging. So obviously, one hope is to benefit personally from such a therapy sooner than would otherwise be the case, balancing that against incurring some unknown degree of risk of failure or harm. The first human trials, those that establish numbers for that risk, will take another few years to wind through to robust conclusions, and further years beyond that will be required for the medical community to become willing to prescribe senolytics generally. Further, those trials will almost all test only a single candidate therapy, and the evidence to date in mice suggests that different senolytics with different mechanisms are tissue-specific in their effects on senescent cells. Multiple different compounds may be more effective than one - but that won't be discovered in the formal trial process. Lastly, well run self-experimentation carried out by a number of people, where the results are published, can help to guide the direction of later, formal studies.

All of these reasons must be balanced against a sober assessment of the risks involved in obtaining and using pharmaceutical compounds, and an acceptance of personal responsibility for consequences should one choose to run those risks.

Caveats in More Detail

There are two areas of personal responsibility to consider here. Firstly, this involves taking chemotherapeutic pharmaceuticals with known side-effects. One should read the relevant papers on their effects, side-effects, and dosages, and make an individual decision on risk and comfort level based on that information. This is true of any pharmaceutical, whether or not approved for use. Do not trust other opinions you might read online: go to the primary sources, the scientific papers, and read those. Understand that where the primary data is sparse, it may well be wrong or incomplete in ways that will prove harmful. Also understand that older physiologies can be frail and vulnerable to the side-effects of specific chemotherapeutic pharmaceuticals in ways that do not occur in younger people and that are not well covered by the studies; pharmacokinetic studies necessary to establish side-effects and tolerances don't tend to be carried out in very old humans, and most cancer trials have participants that almost entirely fall into the 50-80 age range.

Secondly, obtaining and using pharmaceuticals in the manner described here is illegal: choosing to do so would be a matter of civil disobedience, as is the case for anyone obtaining medicines outside the established national system of prescription and regulation. People are rarely prosected for doing so for personal use in the US - consider the legions of those who obtain medicines overseas for reasons of cost, despite the fact that doing so is illegal - but "rarely" is not "never." If you believe that the law is unjust, then by all means stand up against it, but accept that doing so carries the obvious risks of arrest, conviction, loss of livelihood, and all the other ways in which the cogs of modern society crush those who disagree with the powers that be.

Lastly, senolytics is a fast-moving field. This post will become outdated quite rapidly in its specifics regarding candidate pharmaceuticals, as new knowledge and new candidate therapies arrive on the scene. Nonetheless, the general outline should still be a useful basis for designing new self-experiments involving later and hopefully better compounds, as well as tests involving more logistical effort.

Choosing Senolytic Drug Candidates

The criteria for choosing senolytic drug candidates for the purposes of this outline are: (a) it must be taken by mouth, rather than through injection, as the logistics for assembling materials and carrying out injections are considerably more complicated; (b) it must have shown senolytic effects in animal studies, not just in cell studies, as there are all too many failures to make the leap from cell to mouse in pharmaceutical development; (c) there must be enough human data to determine the effects and side-effects of doses used. The more human data, the better, in fact. Finding a list of senolytics and assessing them against these criteria involves research: dig through PubMed in search of senolytic studies and review articles, and then follow chains of references to find other papers. Carefully check the magnitude and other details of the results claimed in animal studies: some senolytics are better than others. Armed with the names of drug candidates, then look up studies of dosage and effects for cancer and other trials in both mice and humans. Not all papers are open access. Where they are not, taking advantage of the efforts of the copyright heretics of Sci-Hub is the best approach to obtain a copy.

At the present time, the criteria above narrow the field to a few repurposed chemotherapeutics, one of which was shown to synergize with the flavonoid quercetin. These are: (a) dasatinib in combination with quercetin, while noting that the data shows it isn't worth trying either one on its own, (b) navitoclax / ABT-263, and (c) alvespimycin / 17-DMAG. Navitoclax, however, has side-effects that are common enough and severe enough to want to avoid it; it causes a loss of platelets in the blood to the point of producing noticable medical consequences, and did so in about half of cancer trial participants.

There is also venetoclax / ABT-199 to consider, however, a modified form of navitoclax intended (and shown) to reduce the worst of its platelet-destroying side-effects, but lacking animal data for senolytic effects. Navitoclax and venetoclax are both BCL-2 family inhibitors, operating on roughly the same mechanism, and another member of this family of pharmaceuticals, ABT-737, has been shown to have senolytic effects. So while venetoclax lacks mouse data for senolytic effects, at first glance it makes some sense to include it in a test: the trade-off is a matter of losing some of the unpleasant side-effects and gaining uncertainty in whether or not the senolytic effects will carry over. There is a very helpful paper from a few years back that covers the relationships between these BCL-2 family inhibitors, and that does a good job of explaining why venetoclax is a favored alternative to navitoclax, at least for the cancer research community.

Of the other compounds we might consider, A1331852, A1155463, piperlongumine, and fisetin are ruled out for lacking published animal data on senolytic effects. FOXO4-DRI is ruled out for being injected and for lacking any human data on dosage or side-effects - though in principle, it should be the best of all the drug-like options so far discovered, if the animal data carries over into human tests. ABT-737 is ruled out for being injected - unlike other BCL-2 family inhibitors it doesn't really interact usefully with mammalian biochemistry if ingested.

Establishing Dosages

The only definitive way to establish a dosage for a pharmaceutical in order to achieve a given effect is to run a lot of tests in humans. Testing in mice can only pin down a likely starting point for experiments to determine a human dose, but the way in which you calculate that starting point is fairly well established for most cases. That established algorithm is essentially the same for most ingested and intravenously (or intraperitoneally in small animals) injected medicines, but doesn't necessarily apply to other injection routes. The relationship between different forms of injection, dosage, and effects is actually a complicated and surprisingly poorly mapped topic, and we'll set that to one side here. Some compounds - as always - are exceptions to the rule, and the only way that scientists discover that any specific compound is an exception is through testing at various doses in various species.

Given that, the discussion here should be taken to apply only to orally administered drugs, as that is the deliberately restricted scope of this post. Further, when considering pharmaceutical dosage, it is important to emphasise that more is not better; this cannot be approached in the way people tend to naively approach the (over)use of dietary supplements. The primary goal, if self-experimenting, is to take as little as necessary of any chemotherapeutic, senolytic compound, as they are all toxic in any meaningful dose. I enourage a careful reading of the papers in which the side-effects in patients at chemotherapeutic doses and treatment durations are described, as well as the studies showing aggressive chemotherapy to produce a higher, rather than lower load of senescent cells. That the dose makes the poison is an ancient adage, but no less true today.

The steps to figure out a suitable starting point for a human test of an orally administered senolytic pharmaceutical are as follows: firstly read the mouse studies for the senolytic compound in question, in order to find out how much was given to the mice and for how long. Doses for most ingested pharmaceuticals of interest will usually be expressed in mg/kg. Secondly apply a standard multiplier to scale this up to human doses, which you can find in the open access paper "A simple practice guide for dose conversion between animals and human". Do not just multiply by the weight of the human in kilograms - that is not how this works. The relative surface area of the two species is the more relevant scaling parameter. Read the paper and its references in order to understand why this is the case. Again, note that the result is only a ballpark guess at a starting point in size of dose. The duration of treatment translates fairly directly, however. For the period of treatment, start with the same number of doses, spacing of doses, and duration as takes place in senolytic studies in mice.

If there isn't enough data to do more than guess at a dose, then that is a good indication to write off that particular compound. Wait for more data, or look for different compounds with better existing data.

Dasatinib and Quercetin

In the case of the dastinib and quercetin combination, the mouse study of senolytic effects used a single dose of 5 mg/kg dasatinib plus 50 mg/kg quercetin. For a 60kg human this scales up to a little less than 25mg dasatinib and 250mg quercetin. For comparison, mouse studies of dasatinib as a chemotherapeutic can be found that use 50 mg/kg per day for multiple days to evaluate its ability to kill cancer cells. A very useful study on dose effects and duration for dasatinib in humans used a dose of 100mg in volunteers, and you can find other trials of dasatinib as a cancer treatment at that dose. Quercetin is an established and widely sold supplement, and it would be a real challenge to consume enough of it to cause any ill effects, never mind significant ones, judging by the toxicology data.

Another way of thinking about dosage is to aim at producing the same concentration of the pharmaceutical in blood that was used in cell culture studies, or observed in mouse studies. To do this you will need existing human data on how a dose maps to concentration in blood or tissues. The senolytic mouse study noted above and the useful human study provide sufficient numbers to make an estimate at this. In the cell culture section of the mouse study, 100-200 nM/L (nanoMoles per liter) is the effective concentration - more than that adds no greater benefit. Given the molecular weight of dasatinib, one can convert the observed blood concentration of 104.5 ng/ml (nanograms per milliliter) in the human study for a 100mg dose to get something in the ballpark of 200 nM/L. Why doesn't everyone use the same units? Well, we wouldn't want to make this too easy. The human study also provides results for a 180mg dose if you want to try scaling up or down to estimate the dose needed to hit different concentrations.

So via one method, the single dose for a 60kg human is 25mg dasatinib and 250mg quercetin. Via the other method the single dose is in the vicinity of 75-100mg dasatinib and 750-1000mg quercetin, assuming that we scale up the quercetin to match the dasatinib, and depending on where we are aiming for in the 100-200 nM/L concentration. The second dose is at chemotherapy trial levels, but is a single dose rather than taken daily over weeks or months, so the impact will accordingly be more limited. You can look at the single dose study for a summary of side-effects at this dosage level. Remember that there is no evidence to suggest that dosing with a senolytic treatment like the dasatinib and quercetin combination frequently will achieve any better result than dosing once every few years: the treatment kills the senescent cells it is capable of killing, and until more of those cells are created in significant numbers, then more of the treatment will most likely do nothing helpful. There are apparently senolytic self-experimenters out there taking dasatinib regularly; I think this shows a poor understanding of the situation, and is probably harmful.


Because there are no published senolytic studies using venetoclax, coming to some kind of ballpark human dose for that purpose involves analogy and educated guesswork. The approach is to compare cancer studies of navitoclax and venetoclax, of which there are many, and then scale the venetoclax cancer study dose down in accordance with the difference between the cancer and senolytic study doses of navitoclax. This is far from ideal, but I'm including this discussion here to point out exactly why one should only choose pharmaceuticals with animal and human senolytic data; as soon as any of that data is absent, there is all too much trial and error and guesswork involved. It is far better to wait rather then venture into the complete unknown, given that more data and better alternative senolytics will emerge in the years ahead.

Firstly, the senolytic dosage for navitoclax in mice from the 2015 study is 50 mg/kg daily for two periods of 7 days spaced 14 days apart - one thing you'll notice fairly quickly in all of this data is that BCL-2 family inhibitors compare unfavorably to dasatinib in terms of the amount needed and duration of treatment. That translates to a 60kg human dose of around 250mg.

A good place to start researching comparative dosages for venetoclax and navitoclax is the 2015 summary paper "ABT-199 (venetoclax) and BCL-2 inhibitors in clinical development". From there, and the references, the chemotherapeutic human dose of navitoclax was settling to somewhere in the 200-300 mg per day range for 14 to 21 days before it was discarded in favor of other tools, with the upper end of that dose range producing the aforemention ugly side-effects related to platelet loss. Dosage for human cancer trials of venetoclax is, on the other hand, all over the map: doses range from 200mg to 1200mg daily carried out over a period of a few weeks to a month, with the dose given cycling in sometimes complex ways. To keep things simple, one point of comparison is to look at the trials versus chronic lymphocytic leukemia for navitoclax and for venetoclax, as they are quite similar. For navitoclax the tested doses ranged from 100mg to 300mg - essentially the same as the senolytic dosage. For venetoclax, the tested doses were 200mg to 1200mg. In both cases, these were daily doses taken for a period of a week or more.

So if one were forced to put a pin into the map based on these numbers, the senolytic human dosage of venetoclax would probably be in the 400-600 mg/day range, every day for a week. Note that this is firmly in chemotherapy with side-effects territory, and there is no direct supporting evidence for effectiveness in mammals whatsoever. All said and done, the rough back of the envelope estimation comes to a result that looks very unattractive, given that we expect better options in the future.


Alvespimycin is an HSP90 inhibitor, and this class of pharmaceutical may produce senolytic effects through less direct BCL-2 family inhibition. Certainly the effects and side-effects look broadly similar to those of navitoclax and venetoclax. One thing to note when researching this compound is that it is used in both injected and oral forms, so one has to be careful to work with only the papers that cover the oral delivery mode, at least in the present context. The senolytic study in mice used an oral dose of 10 mg/kg provided 3 times every other day. This scales up to something like 50mg with the same dosage schedule for a 60kg human.

For comparison, looking at a mouse cancer study, the researchers there used dosages in the 5-15 mg/kg, with a variety of daily and intermittent schedules. A human cancer study also used a wide range of doses, and is a good resource if you are interested in reading up on the potential side-effects. Based on their data, the authors recommended either 40mg every other day or 20mg daily for a period of four weeks of every six weeks for the follow on study.

From these numbers, a human senolytic treatment of three 50mg doses on alternate days once again sounds like something that veers into full blown chemotherapy territory, just not to the same degree as venetoclax above. Anyone considering this would have to make their own decision about risk, as there just isn't enough information out there to talk sensibly about risk and side-effects resulting from a much shorter exposure than was carried out in the human cancer studies.

Use Small Test Doses Prior to Any Study

Near all studies of chemotherapeutics start with low doses, a tenth of the expected study dose. Near all studies report a couple of patients who experience enough of a reaction to the chemotherapeutic at those low doses to drop out or require adjustment of the protocol. If risking chemotherapeutics yourself for senolytic purposes, even single doses or doses for a short time only, it is still important to first test a low dose at a tenth of the desired level of so, to help ensure that there is no adverse reaction. As is true for all of the rest of the considerations here, if you try this, it is entirely your own responsibility to identify, understand, and manage the risks involved.

Verify All of the Above

Assume that anything written anywhere other than the primary materials might be incorrect or misleading. Do not take my word for any of the above information; chase down the primary sources, run the numbers, and make the judgement calls yourself. Is it foolish to self-experiment with chemotherapeutics rather than waiting for better information from human trials or some better form of treatment to emerge? Only you can answer that question, and only you are responsible for any consequences resulting from the answer.

Obtaining Senolytic Pharmaceuticals

For individuals without suitable connections, the easiest way to obtain pharmaceuticals is to order them from manufacturers in China or other overseas locations. As noted at the outset of this post, this is illegal - it would be an act of civil disobedience carried out because the laws regarding these matters are unjust, albeit very unevenly enforced. Many people regularly order pharmaceuticals from overseas, with and without prescriptions, for a variety of economic and medical reasons, and all of this is illegal. The usual worst outcome for individual users is intermittent confiscation of goods by customs, though in the US, the FDA is actually responsible for this enforcement rather than the customs authorities. Worse things can and have happened to individuals, however, even though enforcement is usually targeted at bigger fish, those who want to resell sizable amounts of medication on the gray market, or who are trafficking in controlled substances. There is a fair amount written on this topic online, and I encourage reading around the subject.

Open a Business Mailbox

A mailbox capable of receiving signature-required packages from internal shipping concerns such as DHL and Fedex will be needed. Having a business name and address is a good idea. Do not use a residential address.

Use Alibaba to Find Manufacturers

Alibaba is the primary means for non-Chinese-language purchasers to connect to Chinese manufacturers. The company has done a lot of work to incorporate automatic translation, to reduce risk, to garden a competitive bazaar, and to make the reputation of companies visible, but it is by now quite a complicated site to use. It is a culture in and of itself, with its own terms and shorthand. There are a lot of guides to Alibaba out there that certainly help, even if primarily aimed at retailers in search of a manufacturer, but many of the specific details become obsolete quickly. The Alibaba international payment systems in particular are a moving target at all times: this year's names, user interfaces, and restrictions will not be the same as next year's names, user interfaces, and restrictions.

Start by searching Alibaba for suppliers of the senolytic pharmaceuticals of interest. There are scores of resellers and manufacturing biotech companies in China for any even somewhat characterized pharmaceutical or candidate pharmaceutical. Filter the list for small companies, as larger companies will tend to (a) ignore individual purchasers in search of small amounts of a compound, for all the obvious economic reasons, and (b) in any case require proof of all of the necessary importation licenses and paperwork. Shop around for prices - they may vary by an order of magnitude, and it isn't necessarily the case that very low prices indicate a scam of some sort. Some items are genuinely very cheap to obtain via some Chinese sources.

Many manufacturers will state that they require a large (often ridiculously large) minimum order; that can be ignored. Only communicate with gold badge, trade assurance suppliers with several years or more of reputation and a decent response rate. Make sure the companies exist outside Alibaba, though for many entirely reliable Chinese businesses there are often sizable differences between storefronts on Alibaba, real world presence, and the names of owners and bank accounts. Use your best judgement; it will become easier with practice.

Arrange Purchase and Shipping via Alibaba

Given the names of a few suppliers, reach out via the Alibaba messaging system and ask for a quote for a given amount of the senolytic pharmaceutical in question. Buy twice what you'll think you need, as some of it will be used to validate the identity and quality of the compound batch, and buy that much from at least two different suppliers present in widely separated regions. Payment will most likely have to be carried out via a wire transfer, which in Alibaba is called telegraphic transfer (TT). Alibaba offers a series of quite slick internal payment options that can be hooked up to a credit card or bank account, but it is hit and miss whether or not those methods will be permitted for any given transaction. Asking the seller for a pro-forma invoice (PI), then heading to the bank to send a wire, and trusting to their honesty is good enough for low cost transactions. It should work just fine when dealing with companies that have a long-standing gold badge.

To enable shipping with tracking via carriers such as DHL, the preferred method of delivery for Chinese suppliers shipping to the US or Europe, you will need to provide a shipping address, email address, and phone number. Those details will find their way into spam databases if you are dealing with more than a few companies, and will be, of course, sold on by Alibaba itself as well. Expect to see an uptick of spam after dealing with suppliers via Alibaba, so consider using throwaway credentials where possible.

Chinese manufacturers active on Alibaba are familiar with international shipping practices, and smaller companies will, on their own initiative, apply whatever description to packages will most likely get it past customs. Since declared pharmaceuticals may well be taken aside and confiscated, the description will therefore not involve pharmaceuticals. This is as much motivated by dealing with customs at the Chinese end as pushing things past the US authorities; it is again a form of widespread civil disobedience that reflects a popular disdain for petty laws and regulators where they act as impediments to useful activity.

Quercetin is a Supplement, Buy it at the Store

Any specialist vitamin store will sell quercetin, or at worst it can be ordered online from any reputable retailer.

Storage of Senolytics

Dasatinib, venetoclax, and similar compounds are manufactured as fairly resilient powders and then formed into pills where sold as medications. In powder or pill form, put them in airtight containers in a fridge, and they have a shelf-life of a few years; the specific storage recommendations are easy enough to find online. The same is true of quercetin. This is one of the big advantages of most ingested pharmaceuticals versus injected pharmaceuticals; they are comparatively low-maintenance, stable, and long-lasting. That in turn means less logistical planning and effort.

Validating the Purchased Senolytics

A senolytic compound may have been ordered, but that doesn't mean that what turns up at the door is either the right nondescript powder or free from impurities or otherwise of good quality. Even when not ordering from distant, infrequent suppliers, regular testing of batches is good practice in any industry. How to determine whether a compound is what it says it is? Run the compound through a process of liquid chromatography and mass spectrometry, and compare the results against the standard data for a high purity sample of that compound. Or rather pay a small lab company to do that.

Obtain the Necessary Equipment

Since this process will involve weighing, dividing up, and shipping powders in milligram amounts, a few items will be necessary: spatulas or scoops for small amounts of a substance; a reliable jeweler's scale such as the Gemini-20; sealable vials; small ziplock bags; labels; and shipping and packing materials. All of these are easily purchased online. The recommended shipping protocol is to triple wrap: a labelled vial, secured within a ziplock bag and tape, and then enclosed within a padded envelope.

Use Science Exchange to Find Lab Companies

Science Exchange is a fairly robust way to identify providers of specific lab services, request quotes, and make payments. Here again, pick a small lab company to work with after searching for LC-MS (liquid chromatography and mass spectrometry) services. Large companies will want all of the boilerplate registrations and legalities dotted and crossed, and are generally a pain to deal with in most other ways as well. Companies registered with Science Exchange largely don't provide their rates without some discussion, but a little over $100 per sample is a fair price for LC-MS to check the identity and purity of the compound.

Work with the Company to Arrange the Service

The process of request, bid, acceptance, and payment is managed through the Science Exchange website, with questions and answers posted to a discussion board for the task. Certainly ask if you have questions; most providers are happy to answer questions for someone less familiar with the technologies used. Service providers will typically want a description of the compounds to be tested and their standard data sheets, as a matter of best practice and safety. It is good enough to provide the name for established pharmaceuticals, as the data sheets, mass spectrometry profiles, and other detailed information are freely available online from databases such as DrugBank.

Ship the Samples

Measure out 5mg or so from each separate order as a distinct sample, label it carefully, make sure you have a record linking the sample label to the specific supplier, and package it up. More in the sample is better than less, as several attempts might be needed to get a good result out of the machines used, but each attempt really only needs a very tiny amount of the compound. Ship the sample via a carrier service such as DHL, UPS, or FedEx. Some LC-MS service companies may provide shipping instructions or recommendations. These are usually some variety of common sense: add a description and invoice to the package; reference the order ID, sender, and receiver; clearly label sample containers; and package defensively with three layers of packing; and so forth.

Examine the Results

Once the LC-MS process runs, the lab company should provide a short summary regarding whether or not the compound is in fact the correct one and numbers for the estimated purity. Also provided are the mass spectra, which can be compared with the standard spectra for the compound, which can be found at DrugBank or other sources online.

Ingestion Logistics for Powders

To match to the way in which ingested compounds are taken in most studies, in pill form, it is probably best to make up pill capsules rather than just, for example, taking a measure of the powder in water or wrapped in bread. This is fairly easy to manage, given the tools already obtained for measuring out small powder samples. Specialist vitamin stores, and a range of other vendors, sell empty gelatin pill capsules for supplement enthusiasts, and they will do just fine here. Putting powder into capsules is a fiddly business that only becomes more frustrating with age; I'd suggest trying it out with flour if you haven't done this before. It is a lot harder than one might think. Fortunately, there are a variety of simple, inexpensive tools to help with that; references and video guides are easy to find by searching online. At the very least, unless you happen to have three hands, a capsule holding tray is essential, and I'd recommend some form of small powder funnel.

Establishing Tests and Measures

Unfortunately there is no established, proven, useful test that can directly assess senescent cell level in humans or human biopsies. It is possible to use immunohistochemistry to assess cellular senesence in tissue samples, which is a standard approach in animal studies, but no-one appears to have yet validated that in humans, given biopsies taken from a living individual. Since senescent cells are generated temporarily by wounding, it is quite possible that anything that starts with a biopsy will prove to be unhelpful as a before and after comparison measure for senolytic trials - the levels measured may not bear any resemblance to the normal levels absent a wound.

Without a direct measure, we must fall back on indirect assessments of the detrimental effects of senescent cells. The objective here is a set of tests that anyone can run without the need to involve a physician, as that always adds significant time and expense. Since we are really only interested in the identification of large and reliable effects as the result of an intervention, we can plausibly expect a collection of cheaper and easier measures known to correlate with age to be useful. Once that hill has been climbed, then decide whether or not to go further - don't bite off more than is easy to chew for a first outing.

From an earlier exploration of likely tests, I picked the following items on the basis of a likely connection to the actions of senescent cells, reasonable cost and effort, and ability to carry out the test without a physician's office being involved. Note that this does rule out, to pick one example, the interesting and relevant examination of kidney and liver function, as it would have to be carried out via the radioactive tracer methods of nuclear medicine to obtain decent results. That leaves the tests below quite focused on (a) the cardiovascular system, particularly measures influenced by vascular stiffness, and (b) inflammatory and other markers in the bloodstream:

The cardiovascular health measures in that list are those that are impacted by changes in the elasticity or functional capacity of blood vessels, such as would be expected to occur to some degree following any rejuvenation therapy that addresses senescent cells, chronic inflammation, or other factors that stiffen blood vessels, such as calcification or cross-linking. Positive change of the average values in most of these metrics are achievable with significant time and effort spent in physical training, so movement in the numbers in a short period of time as the result of a treatment should be an interesting data point.


There exist online services such as WellnessFX where one can order up a blood test and then head off the next day to have it carried out by one of the widely available clinical service companies. Of the set of test packages offered by WellnessFX, the Baseline is probably all that is needed for present purposes. But shop around; this isn't the only provider.

Resting Heart Rate and Blood Pressure

A simple but reliable tool such as the Omron 10 is all you need to measure heart rate and blood pressure. It is worth noting here a couple of general principles for cardiovascular measures. Firstly, the further away from the center of the body that the measurement is taken, the less reliable it is - the more influenced by any number of circumstances, such as position, mood, stress, time of day, and so forth. Fingertip devices are convenient, but nowhere near as useful as something like the Omron 10 that uses pressure on the upper arm. Secondly, all of the above-mentioned line items also influence every cardiovascular measure, so when you are creating a baseline or measuring changes against that baseline, carry out each measure in the same position, at the same time of day, and make multiple measurements over a week to gain a more accurate view of the state of your physiology. The Omron 10 is solid: it just works, and seems quite reliable.

Heart Rate Variability

Surprisingly few of the numerous consumer tools for measuring heart rate variability actually deliver the underlying values used in research papers rather than some form of aggregate rating derived by the vendor; the former is required for any serious testing, and the latter is useless. Caveat emptor, and read the reviews carefully. As an alternative to consumer products, some of the regulated medical devices are quite easy to manage, but good luck in navigating the system to obtain one. The easiest way is to buy second hand medical devices via one of the major marketplaces open to resellers, but that requires a fair-sized investment in time and effort - which comes back to the rule about keeping things simple at the outset.

After some reading around the subject, I settled on the combination of the Polar H10 device coupled with the SelfLoops HRV Android application. I also gave the EliteHRV application a try. Despite the many recommendations for Polar equipment, I could not convince either setup to produce sensible numbers for heart rate variability data: all I obtained during increasingly careful and controlled testing was a very noisy set of clearly unrealistic results, nowhere near the values reported in papers on the subject. However, plenty of people in the quantified self community claim that these systems work reasonably well, so perhaps others will have better luck than I. Take my experience as a caution, and compare data against that reported in the literature before investing a lot of time in measurement.

Pulse Wave Velocity

For pulse wave velocity, choice in consumer tools is considerably more limited. Again, carefully note whether or not a device and matching application will deliver the actual underlying data used in research papers rather than a made-up vendor aggregate rating. I was reduced to trying a fingertip device, the iHeart, picked as being more reliable and easier to use than the line of scales that measure pulse wave velocity. Numerous sources suggest that decently reliable pulse wave velocity data from non-invasive devices is only going to be obtained by measures at the aorta and other core locations, or when using more complicated regulated medical devices that use cuffs and sensors at several places on the body.

Still, less reliable data can be smoothed out to some degree by taking the average of measures over time, and being consistent about position, finger used for a fingertip device, time of day, and so forth when the measurement is taken. It is fairly easy to demonstrate the degree to which these items can vary the output - just use the fingertip device on different fingers in succession and observe the result. All of this is a trade-off. A good approach is to take two measures at one time, using the same finger of left and right hand, as a way to demonstrate consistency. While testing an iHeart device in this way, I did indeed manage to obtain consistent and sensible data, though there is a large variation from day to day even when striving to keep as many of the variables as consistent as possible. That large variation means that only sizable effects could be detected.

DNA Methylation

DNA methylation tests can be ordered from either Osiris Green or Epimorphy / Zymo Research - note that it takes a fair few weeks for delivery in the latter case. From talking to people at the two companis, the normal level of variability for repeat tests from the same sample is something like 1.7 years for the Zymo Research test and 4.8 years for the Osiris Green tests. The level of day to day or intraday variation between different samples from the same individual remains more of a question mark at this point in time, though I am told they are very consistent over measures separated by months. Nonetheless, as for the cardiovascular measures, it is wise to try to make everything as similar as possible when taking the test before and after a treatment: time of day, recency of eating or exercise, recent diet, and so forth.

An Example Set of Daily Measures

An example of one approach to the daily cardiovascular measures is as follows, adding extra measures as a way to demonstrate the level of consistency in the tools:

  • Put on the Polar H10; this is involved enough to increase heart rate a little for a short period of time, so get it out of the way first.
  • Sit down in a comfortable position and relax for a few minutes.
  • Measure blood pressure and pulse on the left arm using the Omron 10.
  • Measure blood pressure and pulse on the right arm using the Omron 10.
  • Measure pulse wave velocity on the left index fingertip over a 30 second period using the iHeart system.
  • Measure pulse wave velocity on the right index fingertip over a 30 second period using the iHeart system.
  • Measure heart rate variability for a ten minute period using the Polar 10 and Selfloops.

Consistency is Very Important

Over the course of an experiment, from first measurement to last measurement, it is important to maintain a consistent weight, diet, and level of exercise. Sizable changes in lifestyle can produce results that may well prevent the detection of any outcome resulting from a first generation senolytic pharamaceutical using the simple tests outlined here. Further, when taking any measurement, be consistent in time of day, distance in time from last exercise or meal, and position of the body. Experimentation with measurement devices will quickly demonstrate just how great an impact these line items can have.

Guesstimated Costs

The costs given here are rounded up for the sake of convenience, and in some cases are blurred median values standing in for the range of observed prices in the wild.

  • Business mailbox, such as from UPS: $250 / year
  • Baseline tests from WellnessFX: $220 / test
  • MyDNAage kits: $310 / kit
  • Osiris Green sample kits: $70 / kit
  • Omron 10 blood pressure monitor: $80
  • Polar H10 heart monitor: $100
  • iHeart monitor: $210
  • American Weigh Gemini-20 microscale: $90
  • Miscellenous equipment: spatulas, labels, vials, pill capsules, etc: $60
  • 2 x 2g orders of dasatinib via Alibaba: $300
  • 2 x 5g orders of venetoclax via Alibaba: $1300
  • 2 x 2g orders of alvespimycin via Alibaba: $400
  • Store-purchased quercetin capsules: $10
  • Shipping and LC-MS analysis of samples: $120 / sample

Schedule for the Self-Experiment

One might expect the process of discovery, reading around the topic, ordering materials, and validating the pharmaceuticals to take a couple of months. Once all of the decisions are made and the materials are in hand, pick a start date. The schedule for the self-experiment is as follows:

  • Day 1-10: Once or twice a day, take measures for blood pressure, pulse wave velocity, and heart rate variability.
  • Day 10: Bloodwork and DNA methylation test.
  • Day 11-15: Test a 1/10 dose of the senolytic compounds used, one by one, and abandon the effort if issues are experienced.
  • Day 16: Start to carry out the program of treatment.
  • Day 31-40: Repeat the blood pressure, pulse wave velocity, and heart rate variability measures.
  • Day 40: Repeat the bloodwork and DNA methylation test.

The exact timing is not really important, but it is a good idea to allow enough time following the end of the dosage for things to settle down. In animal studies, senolytic effects occurred fairly rapidly, as did the benefits, but allowing a few weeks of time in a human self-experiment still sounds like a good idea. Certainly it costs nothing to take that step.

Where to Publish?

If you run a self-experiment and keep the results to yourself, then you helped only yourself. The true benefit of rational, considered self-experimentation only begins to emerge when many members of community share their data, to an extent that can help to inform formal trials and direction of research and development. There are numerous communities of people whose members self-experiment with various compounds and interventions, with varying degrees of rigor. One can be found at the LongeCity forums, for example, and that is a fair place to post the details and results of a personal trial with senolytics. Equally if you run your own website or blog, why not there?

When publishing, include all of the measured data, the compounds and doses taken, duration of treatment, and age, weight, and gender. Fuzzing age to a less distinct five year range (e.g. late 40s, early 50s) is fine. If you wish to publish anonymously, it should be fairly safe to do so, as none of that data can be traced back to you without access to the bloodwork provider. None of the usual suspects will be interested in going that far. Negative results are just as important as positive results. For example, given the measures proposed in this post it is entirely plausible that positive changes as a result of present senolytic treatments in a basically healthy late 40s or early 50s individual will be too small to identify - they will be within the same range as random noise and measurement error. Data that confirms this expectation is still important and useful for the community, as it will help to steer future, better efforts.

Final Thoughts: Why Not Wait?

Given all of the cautions above, why not wait? Waiting can be a very sensible strategy. The state of senolytic therapies is progressing rapidly. New and less chemotherapeutic senolytics are emerging, such as FOXO4-DRI. At some point in the next few years, reliable direct tests for senescence will arrive on the scene, allowing a much better view of whether or not these treatments are actually achieving the claimed results. That said, it doesn't hurt to plan, and it doesn't hurt to tinker with some of the component parts of a plan. That is how we can determine whether or not it is worthwhile to experiment now versus waiting to experiment later with better tools.

An Approach to Starving Cancer Cells that is Applicable to Many Cancers

Cancer research will proceed by leaps and bounds just as soon as a larger fraction of the research community aims at the production of therapies that are applicable to all cancers, or at least large categories of cancers. One of the reasons why progress has been slow in the past is that all too many groups work hard to produce therapies that are very narrowly specific to a single type of cancer. There are only so many researchers in the world, only so much funding for cancer research, and a very large number of types of cancer.

So when we watch the work of the cancer research community, we should be looking for research of the sort noted here, something that might be applicable to all cancers or a large majority of cancers, and for preference targets a fundamental mechanism that even rapidly evolving cancerous cells would struggle to bypass. As an added bonus, the strategy outlined here could in principle be applied generally to a patient, not needing to be targeted specifically to cancer cells, as it doesn't seem to have much of an effect on normal cells.

The circadian cycle, the intrinsic clock that exists in all living things, is known to help control when individual cells produce and use nutrients, among many other functions. Scientists previously discovered that proteins known as REV-ERBα and REV-ERBβ are responsible for turning on and off cells' ability to synthesize fats, as well as their ability to recycle materials - a process called autophagy - throughout the day. In healthy cells, fat synthesis and autophagy are allowed to occur for about 12 hours a day when REV-ERB protein levels remain low. The rest of the time, higher levels of the REV-ERB proteins block the processes so that the cells are not flooded with excessive fat synthesis and recycled nutrients. In the past, researchers developed compounds to activate REV-ERBs in the hopes of stopping fat synthesis to treat certain metabolic diseases.

Researchers wondered whether activating REV-ERBs would slow cancer growth, since cancer cells heavily rely on the products of both fat synthesis and autophagy to grow. "Given the importance of the circadian clock in the regulation of many cellular and physiological processes we hypothesize that targeting the circadian clock with drugs may open the way to novel anticancer strategies. This study is very exciting because it sheds light on a new uncharacterized way to treat cancer with very limited toxicity."

Although cancer cells contain REV-ERB proteins, somehow they remain inactive. The researchers used two REV-ERB activators that had already been developed - SR9009 and SR9011 - in studies on a variety of cancer cells, including those from T cell leukemia, breast cancer, colorectal cancer, melanoma, and glioblastoma. In each cell line, treatment with the REV-ERB activators was enough to kill the cells. The same treatment on healthy cells had no effect. "When we block access to these resources, cancer cells starve to death but normal cells are already used to this constraint so they're not affected." The researchers then went on to test the drugs on a new mouse model of glioblastoma. Once again, the REV-ERB activators were successful at killing cancer cells and stopping tumor growth but seemed not to affect the rest of the mice's cells.


Y Combinator Shows an Interest in Investing in the Treatment of Aging

The Y Combinator community is one of the more influential parts of the Bay Area, California technology-focused venture industry. Many of the long-term supporters of SENS rejuvenation research can be found in that part of the world and in related professions - it isn't a coincidence that the SENS Research Foundation is based in the Bay Area. There is a big difference between quiet private support and loud public support for a cause, however. It is thus interesting to see that the Y Combinator principals are now, better late than never, putting their best foot forward to declare interest in the development of therapies to extend human health span and life span.

When established mainstream entities start to throw their support into the ring, it is a sign that the tipping point has arrived and passed. The underlying psychology is that the people involved now see little in the way of any threat to their reputations in supporting efforts to treat aging as a medical condition, which tends to be a self-fulfilling prophecy when the majority goes along with it. No-one ever wants to be the first to commit, of course. Now it seems that the long years of bootstrapping the foundations for a rejuvenation research community in the face of a hostile research community and an uncaring public are just about over. This is all to the good, and everyone who helped to support the SENS community since the turn of the century should be feeling justifiably pleased with the way things have gone over the past few years. Y Combinator now joins the Longevity Fund, Kizoo Technology Ventures, Methuselah Fund, Apollo Ventures, Jim Mellon's Juvenescence venture, and others in a focus on turning back the impact of aging on human health and life span.

I'm excited to announce a new experiment we're going to try: YC Bio. YC Bio is a new way for us to fund early-stage life science companies that are still in the lab phase. Because biology is such a large field, we're going to try concentrating on one sub-area at a time (we've found the companies working in similar areas get a lot of value from being around each other). The first area we're going to focus on is healthspan and age-related disease - we think there's an enormous opportunity to help people live healthier for longer, and that it could be one of the best ways to address our healthcare crisis.

We've been funding bio companies for a little while now, and we've learned a bit about what works and doesn't. We will try to design the program in light of what we've learned, and almost certainly we'll make a lot of changes as we go along. This will be a special track - the companies will go through the regular YC batch, but there will be a few differences. Instead of the standard deal for YC companies (which is $120,000 invested for 7% ownership) we'll offer these companies any amount between $500k and $1 million for 10-20% ownership, scaling linearly.

We'll also offer the companies free lab space (we're still looking for one lab space partner, and we'd love for interested partners to get in touch). In addition, we'll have a number of other special deals for YC bio companies, and access to a wide range of experts. There will be a specific Request for Startup in our application system for companies to indicate they're interested in this system. Other bio companies are of course welcome to apply for the standard YC program.


Sarcopenia as an Inflammatory Condition, Driven in Part by Cellular Senescence

Sarcopenia is the name given to the characteristic loss of muscle mass and strength that occurs with age, though insofar as the slow progress towards an official clinical definition is concerned, this only counts in the more advanced stages. We could do with less of that sort of thinking in medicine and research, as all age-related declines are a problem, and the earlier they can be addressed, the better. If a therapy addresses the root causes of an age-related condition, then it should be just as usefully applied every so often starting at 40, as a preventative treatment, as it would be starting at 70, in order to turn back much larger amounts of damage.

Sarcopenia is a great example of the way in which many areas of research into aging resemble the parable of the blind men and the elephant; every specialized research group looking at just one layer in a complex, interacting set of mechanisms and outcomes, and claiming their layer to be the most important. When reading the literature on sarcopenia, there are many theories and causes, most of which are backed by good evidence. Think of disruption of regenerative processes via chronic inflammation and stem cell decline, the role of cellular senescence in achieving that disruption, or, separately, neurological decline in the links between muscle and nervous system, reduced protein intake and lack of exercise in older individuals, and an age-related failure to process dietary amino acids.

As things stand, I think the stem cell researchers have a compelling last word with regard to the size of the contribution of declining stem cell activity on muscle atrophy in aging versus other possible causes. We then have to ask, however, why does muscle stem cell activity falter with age? What are the mechanisms driving that change? Research in recent years points to inflammatory signals as one of the ways in which regeneration and tissue maintenance are disrupted, and some portion of that inflammation arises from the signaling generated by growing numbers of senescent cells. Still, each of these named items is just one layer in a complex system - a system that is too complex to model well today. There are plenty of other causes of stem cell decline with evidence to support them. The true size of any specific contribution, the importance of any specific connection, will only be determined in the near future through some form of therapy that removes it. The best and fastest way to understand aging in detail is to fix the known forms of damage, one by one, and observe the results.

The paper here considers inflammation in sarcopenia, but not from the perspective of stem cell tissue maintenance. Rather, the authors focus on the way in which age-related increases in chronic inflammation might interfere with the protein synthesis needed to build muscle - which comes back around to the various studies suggesting that disruption in the processing of nutrients is a contributing cause of sarcopenia. Eventually everything is connected to everything else in aging and cellular biochemistry, given enough time to find the links. Advances in senolytic therapies to clear senescent cells and their inflammatory signaling, coupled with ways to reverse the age-related dysfunction of the immune system should in years ahead help to determine the degree to which sarcopenia is caused by inflammation.

The Role of Inflammation in Age-Related Sarcopenia

One of the major problems in the aging population is a progressive loss in skeletal muscle mass, muscle strength, and/or functionality, described as age-related sarcopenia. Several strategies to attenuate the loss of muscle mass and other muscle impairments that comes with aging have been developed. However, none of these have been proven successful to fully reverse the muscle wasting condition. Given the high prevalence of sarcopenia in the aging population and the associated high health care costs, it is of importance to reveal and elucidate the working mechanisms which underlie muscle protein metabolism in the elderly, in order to optimize the classic interventions and/or to develop new ones.

Muscle protein metabolism is carefully regulated by counterbalanced fluctuations in muscle protein breakdown (MPB) and muscle protein synthesis (MPS). In the elderly, the balance between MPB and MPS seems to be disturbed, which progressively increases the loss of skeletal muscle mass. Many underlying factors such as hormonal changes, decreased activity, diminished nutrient intake, and neuronal changes were reported in the literature, but lately, the role of inflammation on the regulation of muscle protein metabolism has gained more and more interest among gerontologists.

Generally, aging is associated with a chronic state of slightly increased plasma levels of pro-inflammatory mediators, such as tumor necrosis factor α (TNFα), interleukin 6 (IL-6) and C-reactive protein (CRP). This state is often referred to as a low-grade inflammation (LGI) and is, at least partly, the manifestation of increased numbers of cells leaving the cell cycle and entering the state of cellular senescence. Indeed, senescent cells acquire a Senescence-Associated Secretory Phenotype, which induces the production of pro-inflammatory cytokines (TNFα, IL-6 and an overactivation of NF-κB). Moreover, there is a growing interest in the association between the telomere/telomerase system and LGI, as cellular senescence can be triggered by critically short telomeres, representing irreparable DNA damage. Also, there are indications that LGI can directly cause telomere/telomerase dysfunction, enforcing the vicious LGI circle and stimulating an accelerated aging phenotype.

Although it has been suggested that inflammatory mediators affect muscle protein metabolism, it is not fully understood to what extent and through which signaling pathways they induce muscle wasting. Population-based data suggest that circulating concentrations of IL-6 and TNFα are significantly elevated in sarcopenic elderly and it was reported that higher IL-6 and CRP levels increase the risk of muscle strength loss. In a 10-year longitudinal study in community-dwelling elderly, plasma concentrations of TNFα, IL-6, and IL-1 were shown to be strong predictors of morbidity and mortality in older subjects. Furthermore, systemic inflammation was also reported as one of the primary mediators of skeletal muscle wasting and it was shown to accelerate aging in general. Without pronouncing on causality, these findings suggest that there is a link between inflammatory mediators and muscle mass and function.

A number of mechanisms have been shown to contribute to the etiology and/or progression of muscle wasting with advancing age. Somehow, many of these mechanisms interfere with inflammatory mediators. However, further research is required to determine through which mechanisms inflammation directly or indirectly affects MPB and MPS with aging. Classic interventions such as protein supplementation and resistance exercise are generally accepted to be the most appropriate to positively affect muscle protein metabolism in elderly. However, not all studies univocally support the effectiveness of these strategies for long-term treatment of age-related muscle wasting. Elderly, and very old or frail seniors in particular, might benefit from a strategy primarily focused on alleviating their muscle insensitivity to anabolic stimuli. In this regard, the treatment of LGI in these elderly might play an important role.

Bioethicists Consider the Search for a Treatment for Aging

This press release from a UK bioethics organization announces a recently published and comparatively innocuous short PDF primer for policy makers on the present state of research into the treatment of aging as a medical condition. Innocuous or not, it still contains a fair dose of utter nonsense mixed in with its view of the field, as is fairly standard for this sort of thing. Professional bioethics, it has to be said, has done little to make itself useful in the past generation in my view, and in fact has used regulation to slow progress in those areas where bioethicists have attracted the most attention. It is a corruption of the older, actually useful field of medical ethics, which had the merits of being simple, valuable, and requiring little upkeep. Bioethics, on the other hand, has become a cancerous political institution, ever growing, and its practitioners ever incentivized to justify their budgets by making up obstacles where none actually exist.

Geroscience, also called biogerontology, is a field of research that is exploring the biological processes that underlie ageing. Researchers working in this field believe that intervening in these processes could be a more efficient way of increasing health span - the number of years we are healthy - than tackling each condition individually. Recent advances in the tools of research are likely to accelerate our understanding of ageing processes in the near future.

Compressing the period of poor health experienced by many in old age could have a transformative effect on the lives of older people and is widely considered to be the primary goal of geroscience research. Biomedical interventions, along with environmental, social and lifestyle modifications, have already contributed to the extension of human lifespan. Depending on other factors that could affect lifespan, ageing interventions could lead to a further delaying of death. Some suggest that a realistic target of geroscience research is to delay all ageing-related disorders by about seven years. Other commentators believe that scientific advances will lead to much more radical effects on ageing and human lifespan in the near future.

There are differences of opinion about the value and morality of extending lifespan, even moderately. Some philosophers believe that we think of our lives as having a certain shape, which underpins how long we think people should work and how long it is appropriate to be old. Increased longevity therefore might threaten the shape we envisage for our lives and our sense of personal identity. The benefits of experiencing the pleasures of life over a longer time period are used by some to justify life extension; others argue it is quality not quantity of years that matters. Some equate extending life with saving lives, and suggest there is a strong moral imperative to pursue treatment for disease, even if the side effect is an increase in lifespan.

A common concern of lifespan extension is that it would accelerate population growth, and that this would have a range of adverse consequences, particularly for the environment. However, one study suggests that population changes would be surprisingly slow in response to even a dramatic extension of lifespan and would not necessarily lead to overpopulation. It has also been argued that using finite resources in a nonsustainable manner is a problem that needs to be solved independently of how long people live.

Estimations of the impact of increasing health span on the economy are generally positive. For example, one analysis suggests increasing human health span would reduce healthcare spending and lead to significant economic savings. Another suggests that delayed ageing could mean increases in social benefit and public healthcare costs, but that these would be far outweighed by economic gains as a result of a healthier workforce who remain employed for longer and are given more time to save for retirement. These effects would depend on the relative increases in health span and lifespan that could be achieved by ageing interventions, which currently are highly uncertain.

Ageing interventions are likely to be available only through the private sector initially. As with any paid for therapy, it is probable that access to ageing interventions will be unequal, leading to an exacerbation of existing health inequalities according to income, socioeconomic status, and geography. In addition, personal choices about uptake of ageing interventions could have implications for entitlement to state care and health insurance. There are calls for government policies to ensure unequal access to ageing interventions is avoided. Global health inequalities present particular challenges in this context, given that the citizens of some countries still have low life expectancies owing to poor sanitation, nutrition, and healthcare provision. The duties of developed countries to put efforts into addressing these problems, in relation to the efforts put into research on ageing interventions, require consideration.

Some argue that the focus on finding medical treatments for ageing is unhelpful, in that it suggests ageing is a problem that requires fixing and reinforces negative views of ageing. There are parallels with how the medical community view frailty. Frailty is commonly regarded as a state of overall poor health, weakness and vulnerability, but diagnosing people with frailty may serve to marginalise them from society and unfairly label people as being destined to decline. There is also concern that other important elements of successful ageing, such as personal relationships, social position, physical environment and independence, are side-lined by geroscientists.

An important question for geroscience research is whether potential interventions should be tested in younger people, before biological ageing has started, or in older adults already experiencing symptoms of ageing. In the past, involving older adults in research was thought to be difficult and of no benefit to them. This view has broadly changed. The challenges of research have been found to be much the same whatever the age of the participant, and medical interventions in people aged over 80 can have beneficial effects on their health. In addition, 'older adults' are a diverse group and generalisations about people's ability and willingness to take part in research should be avoided.


Stem Cells Enhanced with Platelet-Derived Coatings are More Effective at Cardiac Tissue Repair

The broad and well-funded field of regenerative medicine is giving rise many new and varied areas of development, one of which is the engineering of stem cells to make them perform more effectively following transplantation. This includes a range of additions that do not occur in nature. For example, in past years, researchers have enhanced stem cells with add-ons such as timed release packages of supportive molecules to steer their behavior and sustain their activities for longer in the patient. In the research presented here, scientists instead coat stem cells with particles based on the exterior of platelets, causing the cells to adhere to tissues in areas of damage, where they can do the most good via signaling and other mechanisms. In effect, it is a way to improve the localization of delivery and activity of stem cells, even when lacking information on the exact location of damage in the patient. As might be expected, that turns out to improve the end result in terms of regeneration and restoration of tissue function.

Although cardiac stem cell therapy is a promising treatment for heart attack patients, directing the cells to the site of an injury - and getting them to stay there - remains challenging. In a new pilot study using an animal model, researchers show that "decorating" cardiac stem cells with platelet nanovesicles can increase the stem cells' ability to find and remain at the site of heart attack injury and enhance their effectiveness in treatment. "Platelets can home in on an injury site and stay there, and even in some cases recruit a body's own naturally occurring stem cells to the site, but they are a double-edged sword. That's because once the platelets arrive at the site of injury, they trigger the coagulation processes that cause clotting. In a heart-attack injury, blood clots are the last thing that you want."

The researchers wondered if it would be possible to co-opt a platelet's ability to locate and stick to an injury site without inducing clotting. They found that adhesion molecules (a group of glycoproteins) located on the platelet's surface were responsible for its ability to find and bind to an injury. So the team created platelet nanovesicles from these molecules, and then decorated the surface of cardiac stem cells with the nanovesicles, "The nanovesicle is like the platelet's coat. There isn't any internal cellular machinery that could activate clotting. When you place the nanovesicle on the stem cell, it's like giving the stem cell a tiny GPS that helps it locate the injury so it can do its repair work without any of the side effects associated with live platelets."

In a proof-of-concept study involving a rat model of myocardial infarction, twice as many platelet nanovesicle (PNV) decorated cardiac stem cells (CSCs) were retained in the heart than non-decorated cardiac stem cells. The rodents were monitored for four weeks. Overall, the rats in the PNV-CSC group showed nearly 20 percent or higher cardiac function than the control CSC group. A small pilot study in a pig model also demonstrated higher rates of stem cell retention with PNV-CSCs, though the team did not perform functional studies. A future follow-up study is planned.


Two Examples of Recent Work on Novel Drug Candidates to Treat Alzheimer's Disease

Absent any greater context on Alzheimer's disease research, one might look back at the past twenty years of clinical trials and consider this medical condition to be an insurmountable obstacle at our present stage of progress in biotechnology. The history is an unremitting series of abject and expensive failures. The underlying context is more promising, however - Alzheimer's research is the sharp, applied end of two massive, distributed research projects that are still somewhere in their middle stages. The first of these is the effort to map and understand the biochemistry and cellular function of the brain in detail. The second is the effort to produce functional, safe, reliable immunotherapies, which in turn requires researchers to map and understand the biochemistry and cellular function of the immune system in detail. At some point, immunotherapies to remove the protein aggregates associated with Alzheimer's will start to work, as tremendous progress has been made in the underlying understanding of the brain and the immune system over the past decade or two. Early signs of that stage of progress emerged last year, but they are still only early signs.

Failure has consequences, however. As the primary focus of amyloid clearance continues to fail to produce results, it is the case that ever more effort and funding flows in other directions. Some of these are quite promising and genuinely new approaches that have yet to be fully explored, such as restoration of lost drainage of cerebrospinal fluid. Others seem more like the business as usual approach of the pharmaceutical research community, which is to say (a) tinkering with ways to compensate for the disease state rather than addressing something closer to a root cause, and (b) screening and repurposing existing drugs that are already approved for use in humans, even if the effects are only marginal, because that is cheaper than looking for new approaches. That sometimes this tinkering turns up items that might be worth developing as stop-gap therapies is either a blessing or a curse: a blessing because some benefits are better than no benefits, and a curse because it distracts significant effort from addressing the causes of the condition. It is hard to say which is more the case, especially in the scenario in which a direct assault on root causes is proving to be much, much harder than expected.

The two separate lines of drug development noted below are examples of largely compensatory approaches, even though they touch on aspects of the cellular biochemistry of the brain known to change with age. They do not address the underlying causes of the dysfunctions they ameliorate, but rather try to force the behavior of brain cells and their component parts into a more youthful configuration - overriding the evolved reactions to the damage of aging. One of these approaches focuses on growth factors that govern many fundamental aspects of cellular behavior, such as replication, while the other touches on mitochondrial function. Mitochondria, the power plants of the cell, are known to suffer a general malaise of reduced function and altered dynamics in aging, and since the brain is an energy-hungry organ, it is perhaps the most profoundly affected by this form of decline.

Diabetes drug "significantly reverses memory loss" in mice with Alzheimer's

A drug developed for diabetes could be used to treat Alzheimer's after scientists found it "significantly reversed memory loss" in mice through a triple method of action. "With no new treatments in nearly 15 years, we need to find new ways of tackling Alzheimer's. It's imperative that we explore whether drugs developed to treat other conditions can benefit people with Alzheimer's and other forms of dementia. This approach to research could make it much quicker to get promising new drugs to the people who need them."

This is the first time that a triple receptor drug has been used which acts in multiple ways to protect the brain from degeneration. It combines GLP-1, GIP, and Glucagon which are all growth factors. Problems with growth factor signalling have been shown to be impaired in the brains of Alzheimer's patients. The study used APP/PS1 mice, which are transgenic mice that express human mutated genes that cause Alzheimer's. Those genes have been found in people who have a form of Alzheimer's that can be inherited. Aged transgenic mice in the advanced stages of neurodegeneration were treated. In a maze test, learning and memory formation were much improved by the drug which also: enhanced levels of a brain growth factor which protects nerve cell functioning; reduced the amount of amyloid plaques in the brain linked with Alzheimer's; reduced both chronic inflammation and oxidative stress; slowed down the rate of nerve cell loss.

Alzheimer's drug turns back clock in powerhouse of cell

The experimental drug J147 is something of a modern elixir of life; it's been shown to treat Alzheimer's disease and reverse some measures of aging in mice and is almost ready for clinical trials in humans. Now, scientists have solved the puzzle of what, exactly, J147 does. They report that the drug binds to a protein found in mitochondria, the energy-generating powerhouses of cells. In turn, they showed, it makes aging cells, mice and flies appear more youthful.

Researchers developed J147 in 2011, after screening for compounds from plants with an ability to reverse the cellular and molecular signs of aging in the brain. J147 is a modified version of a molecule (curcumin) found in the curry spice turmeric. In the years since, the researchers have shown that the compound reverses memory deficits, potentiates the production of new brain cells, and slows or reverses Alzheimer's progression in mice. However, they didn't know how J147 worked at the molecular level.

In the new work, the team used several approaches to home in on what J147 is doing. They identified the molecular target of J147 as a mitochondrial protein called ATP synthase that helps generate ATP - the cell's energy currency - within mitochondria. They showed that by manipulating its activity, they could protect neuronal cells from multiple toxicities associated with the aging brain. Moreover, ATP synthase has already been shown to control aging in C. elegans worms and flies. Further experiments revealed that modulating activity of ATP synthase with J147 changes the levels of a number of other molecules - including levels of ATP itself - and leads to healthier, more stable mitochondria throughout aging and in disease. The team is already performing additional studies on the molecules that are altered by J147's effect on the mitochondrial ATP synthase-which could themselves be new drug targets. J147 has completed the FDA-required toxicology testing in animals, and funds are being sought to initiate phase 1 clinical trials in humans.

Functional Muscle Tissue Grown from Induced Pluripotent Stem Cells

Progress in tissue engineering consists of many small technology demonstrations similar to the one noted here. Researchers establish that a specific source of cells can be used with a specific recipe for culture and growth in order to generate organoids of a specific tissue type. Given success there as a starting point, further progress becomes possible towards a better quality of structured tissue, and all of the other line items needed on the way to the mass production of patient-matched tissues for use in clinical medicine.

Biomedical engineers have grown the first functioning human skeletal muscle from induced pluripotent stem cells. The advance builds on work published in 2015 when researchers grew the first functioning human muscle tissue from cells obtained from muscle biopsies. The ability to start from cellular scratch using non-muscle tissue will allow scientists to grow far more muscle cells, provide an easier path to genome editing and cellular therapies, and develop individually tailored models of rare muscle diseases for drug discovery and basic biology studies.

"Starting with pluripotent stem cells that are not muscle cells, but can become all existing cells in our body, allows us to grow an unlimited number of myogenic progenitor cells. These progenitor cells resemble adult muscle stem cells called 'satellite cells' that can theoretically grow an entire muscle starting from a single cell." Induced pluripotent stem cells are cells taken from adult non-muscle tissues, such as skin or blood, and reprogrammed to revert to a primordial state. The pluripotent stem cells are then grown while being flooded with a molecule called Pax7 - which signals the cells to start becoming muscle. As the cells proliferated they became very similar to - but not quite as robust as - adult muscle stem cells. While previous studies had accomplished this feat, nobody has been able to then grow these intermediate cells into functioning skeletal muscle.

"It's taken years of trial and error, making educated guesses and taking baby steps to finally produce functioning human muscle from pluripotent stem cells. What made the difference are our unique cell culture conditions and 3-D matrix, which allowed cells to grow and develop much faster and longer than the 2-D culture approaches that are more typically used." Once the cells were well on their way to becoming muscle, the researchers stopped providing the Pax7 signaling molecule and started giving the cells the support and nourishment they needed to fully mature. After two to four weeks of 3-D culture, the resulting muscle cells form muscle fibers that contract and react to external stimuli such as electrical pulses and biochemical signals mimicking neuronal inputs just like native muscle tissue.

The researchers also implanted the newly grown muscle fibers into adult mice and showed that they survive and function for at least three weeks while progressively integrating into the native tissue through vascularization. The resulting muscle, however, is not as strong as native muscle tissue, and also falls short of the muscle grown in the previous study that started from muscle biopsies. Despite this caveat, the researchers say this muscle still holds potential. The pluripotent stem cell-derived muscle fibers develop reservoirs of "satellite-like cells" that are necessary for normal adult muscles to repair damage, while the muscle from the 2015 study had much fewer of these cells. The stem cell method is also capable of growing many more cells from a smaller starting batch than the earlier biopsy method.


Those Who Reject Rejuvenation Research and Longer Lives Do Little More than Repeat Old, Worn Objections

As Aubrey de Grey notes in this policy-focused interview, advocates for the significant extension of healthy human life spans through rejuvenation research after the SENS model are not exactly faced with high-quality opposition. Much of the time, we might as well be talking to a recording, one that continually repeats the same tired, well-refuted objections. The opposition doesn't engage with any of our arguments, its members just say the same things over and again. In some ways that makes this easy. In others ways that makes this hard: a very large number of people are out there repeating variants on the few broken record objections to living longer in youthful health and vigor. That crowd seems to soak up any amount of rational argument in favor of an end to aging with little apparent change in the short term. Nonetheless, our community of researchers, advocates, and investors has clearly made considerable progress over the past twenty years. Attitudes are changing, alongside progress towards the clinic for the first rejuvenation therapies. It is still a battle at every step of the way, but one that we are slowly winning.

Erich: I'll ask you a question here,s inspired by a piece authored by political scientists Francis Fukuyama, a member of George W. Bush's Council on Bioethics between 2001 and 2004. He's getting at this idea that in his mind and maybe in the minds of some other people, if life extension technologies are limited: A. Who gets them? B. Is it possible that, in a world where some people have access to these technologies and others do not, there might become a two-tier hierarchy between the haves and have nots?

Aubrey: Yeah this is one of the standard objections or concerns that are raised about these things, and they've been raised since the dawn of time. I've been answering them since the dawn of time. To be honest, I'm getting frustrated that people - and I'm not talking about people like you, I know you have to ask these questions - but that people like Fukuyama continue to insist on repeating these concerns despite the fact that they have never actually provided any kind of rebuttal to the rebuttals that I provide.

They never say, "Oh no, this answer to my concern is actually not going to work." They just repeat the concern, which of course is intellectually dishonest. The actual answer is very simple. There is no chance whatsoever that we will actually have this divide. The reason there is no chance is because in contrast to medicine that we have today, high-tech medicine for the elderly, that costs a lot and really is limited by ability to pay - in contrast to that medicine, the medicine we're talking about will actually work. In other words, it will genuinely keep people truly youthful and able-bodied for as long as they live, and that will be a lot longer.

And that means that those medicines, unlike today's medicines, will pay for themselves. This is because they will allow the people who get the medicines to continue to contribute wealth to society. Now that, of course, is over and above all the other savings we will have. For example, kids will be more productive since they will no longer have to look after their sick parents, and so on. But the fact is that any way you do the arithmetic, even if you make pessimistic presumptions as to what the therapies will actually cost to deliver, and of course, those numbers will inevitably come down over time anyway, it is still perfectly clear that it will be economically suicidal for any country not to make these therapies available to everybody who is old enough to need them.

Erich: For our last question, what are some of the general shifts you'd like to see politically in order to make the national climate more receptive to technologies such as the ones you're pioneering?

Aubrey: I honestly don't think that that's quite the right question. I don't think that we need changes to government and so on with regard to new technologies. I think what we need is a little bit of long-term anticipation because the fact is that we're going to get these technologies one way or another. It's just a question of how soon. But the second question is how ready we will be to implement them and to disseminate them and generally to introduce them in a smooth manner. We all know that the industrial revolution was a bit turbulent, and that was kind of like it was bound to be that way. We suddenly had these new machines, and we suddenly had a lot of people without jobs. Nobody really saw it coming; they couldn't have seen it coming.

But this we can see coming because we've got all this work going on at the laboratory, and it's publicized, a lot. That means, that there will come a point when we get these therapies, and people will have seen them coming. In particular, it means that it will come at a point much sooner, maybe even five years from now, as little as that. Then, results in the laboratory, just on life, are sufficiently impressive that the general public begins to believe that, yes, this whole "rejuvenation thing," this whole "longevity escape velocity" thing really is probably going to happen soon.

Now, at that point, it doesn't really matter who's right and who's wrong and who's optimistic and who's pessimistic. What matters is: it's going to be complete pandemonium. Everyone's going to change how they make their life choices, how they spend their money and so on because of the change that will have occurred in how long they expect to live. And it's governments that have been putting their heads in the sand right up until that point, not listening to people like me who are telling them it's coming. It's going to be much more chaotic and turbulent than it will be if governments starting today start to pay attention to the wave that is coming and to how it's going to roll out.


Fight Aging! Newsletters Translated into French at Long Long Life

The team behind the Long Long Life site has been translating recent Fight Aging! newsletters into French, using a mix of automated translation systems and professional editing. I'm all in favor of more of this: language barriers are a terrible impediment for an initially sparse movement, made up of people scattered around the world. As we've seen over the past decade in the increasing cooperation between longevity science communities in different countries, even crude translation automation makes a huge difference to the degree to which groups can become aware of one another and help out. The reason why Fight Aging! is published under a Creative Commons license is to encourage people to do exactly this sort of thing without having to ask. The flattery along the way doesn't hurt, of course:

I represent the Long Long Life website, and I'm writing to inform you that we have been translating excerpts from the Fight Aging! newsletter into French for a couple of weeks using DeepL and professional post-editing. The pace looks sustainable for now so it's looking like we will be doing this regularly. If you know of any French-speaking enthusiasts who would like to benefit from your news and incredible work, some of it is now available on our site. Thank you so much for the amazing work you are putting in!

As for DeepL, my professional opinion is that it is a great tool for communication, especially in science since there are less subtleties in the discourse. I find it a promising tool with great potential. It demands however to be carefully post-edited by professionals, or the translation memory it relies on risks being polluted by the many unreliable entries that the general public is okay with. The grammar is still somewhat feeble when it comes to abstract thinking and opinion pieces, which is why we are focusing on hard science for now when we translate FA! content. We are working to increase the exposure of our website so that more people have access to the scientific content we want to share.

I point this out today to note that automated translation, particularly the DeepL system used here, has advanced to the point at which it is cost-effective for small volunteer and other low-expense groups to translate heavily scientific content on a regular basis. In the past the challenge for translating resources such as Fight Aging! has always been that the life sciences speak a language all of their own. It happens to bear some resemblance to English, but diverges fairly heavily into an extended vocabulary of trade words, neologisms, and situational redefinitions that are anything but intuitive. Plus many papers are written by people for whom English is a second language, and who have a tendency to omit many of the useful little words that make sentences hang together, such as indefinite articles.

The current advocacy groups whose local audiences speak a language other than English could benefit from following the Long Long Life example here, and looking into DeepL and similar tools. There is a great deal of very useful English-language work produced over the past decade of advocacy and science for rejuvenation that has yet to be translated. The non-English speaking populations of Europe, Africa, and Asia are large, and most of them have yet to be introduced in any serious way to SENS rejuvenation research or the advocacy movements that have grown in the English-language and Russian-language worlds. Similarly, we in the English-language world see only a fraction of the efforts and advocacy that take place in those other communities. The cost of translation has fallen to be low enough that we as a community can now start to do better than this, I think.

Specific Risk Factors can Appear to Decline in Importance in Later Life, as the High-Risk Individuals are Already Dead

As this 40-year longitudinal study illustrates, when measuring the correlation between specific risk factors on specific forms of mortality, their influence can appear to decline in later life. That is to say that mortality rates keep rising with advancing age, but they are less obviously influenced by any one cause for a given cohort of individuals. This effect occurs because the fatal consequences of a particular form of age-related dysfunction will tend to occur earlier in old age for individuals with the highest risk. With each passing year, a given age group is ever more made up of resilient survivors, people who - for whatever reason - do not have an overall mortality risk that is strongly determined by the specific dysfunction examined in the study. If they did, they would be dead already.

The age range over which this effect occurs is different depending on the risk factor in question and how it is linked to forms of harm. The cardiovascular risk factors examined here are more important or less important in a quite different set of ages in later life than, say, the advanced transthyretin amyloidosis that seems to be a majority cause of death for supercentenarians. The end of life is a set of overlapping curves of risk and influence for many different mechanisms, rising and falling out of lockstep due to the continued loss of those individuals most at risk, even as overall mortality rate rises inexorably.

Despite efforts during recent years to identify new risk factors or biomarkers that can predict cardiovascular diseases, no major breakthrough has been made in the clinical setting to beat the traditional risk factors that have been known for decades: blood pressure, diabetes mellitus, low-density lipoprotein (LDL)- and HDL, high-density lipoprotein (HDL)-cholesterol, smoking, and obesity. These traditional risk factors thus appear robust, and a deeper understanding of their usefulness is therefore desirable.

It is likely that the impact of a risk factor would decline by aging, given that there is a survival bias in the elderly: Many of those with high levels of risk factors at midlife would have experienced an event or died before being included in an investigation of risk factors in the elderly. And, indeed, the impact of a risk factor is usually lower than expected from studies in middle-aged samples when elderly populations are investigated. However, using this approach, it is hard to compare the strength of a risk factor in younger versus elderly subjects.

In order to study the impact of aging on the strengths of risk factors in a longitudinal fashion, we have, in the present study, used a sample of men all aged 50 years at a baseline examination in the early 1970s who has, so far, been followed for 4 decades. We tested the interactions between age and the traditional risk factors regarding incident cases of 3 major cardiovascular diseases: myocardial infarction, ischemic stroke, and heart failure, with the hypothesis that the strength of most, but not all, traditional risk factors would decline by aging. The major question to be answered was which of the risk factors that still retained an important impact in the elderly.

The present study showed, as expected, that most risk factors measured at middle age lost in power during the aging process regarding associations with incident cardiovascular disease. However, some exceptions from this general rule were noted: LDL-cholesterol was significantly related to incident myocardial infarction, whereas body mass index and fasting glucose were related to incident heart failure also in the elderly. The main reason for the general decline in the power of the risk factors over time is likely to be attributed to the fact that individuals with the highest values of the risk factors at midlife will experience an event at an early age, and therefore mainly low-risk individuals will remain at risk as the cohort becomes older. Thus, every cohort will consist of "survivors" when the follow-up increases, and in this group of survivors the impact of risk factors will be diminished.


Simple Assessments of Resilience as Potential Biomarkers of Aging

The search for low-cost, reliable measures of biological age continues apace in the research community. The more the better. Even if an individual measure is only loosely correlated, or produces fairly fuzzy, variable data, it may be still be possible to build an algorithm that combines many such different measures into a more accurate overall biomarker of aging. Given such a biomarker, the research community could more rapidly explore and assess potential rejuvenation therapies, and progress in the field of longevity science would accelerate as a result.

Physical resilience is the ability of an organism to respond to physical stress, specifically, stress that acutely disrupts normal physiological homeostasis. It is the ability to quickly resolve these unexpected or unusual environmental, medical or clinical challenges that should be relevant to a better understanding of the underlying health status of the animal. By definition, resilience would be expected to decrease with increasing age, while frailty, defined as a decline in tissue function and measured by parameters such as walking speed, gait, and grip strength, increases with increasing age. The loss of resilience occurs earlier in life and so may be a causative factor in the development of frailty. Therefore, assessment of resilience could be a highly informative early paradigm to predict absence of biological dysfunction, i.e. healthy aging, compared to frailty, which only measures late life dysfunction.

Unfortunately, parameters for resilience in the mouse are not well defined, and no single standardized stress test exists. Because aging is a multifactorial process, integrative responses involving multiple tissues, organs, and activities need to be measured to reveal the overall resilience status. Therefore, a panel of stress tests, rather than a single all-encompassing one, might be more informative. An ideal battery should have enough dynamic range in the response to allow characterization of an individual in easily distinguishable groups as being resilient or non-resilient. Each test should also be simple, reliable, and inexpensive so the panel can easily be duplicated by many different groups. As a panel, three stressors, cold, sleep deprivation (SD), and the chemotherapeutic drug cyclophosphamide (CYP), fit these criteria. The mechanisms of response to cold are multifactorial. SD is a risk factor for insulin resistance and diabetes, memory loss, heart disease, and cancer. CYP targets several different systems but most specifically cells of lymphoid and neutrophilic lineage.

These stressors are also relevant to human medicine and aging. For example, humans can develop intolerance to cold environmental temperatures with increased sensitivity to hypothermia with increasing age. SD is a major health concern in developed countries and is associated with increasing age. Normal aging produces sleep disturbances including sleep fragmentation and sleep loss in humans. CYP is a representative chemotherapeutic agent used extensively in patients for a variety of conditions including cancer and rheumatoid arthritis. Short-term side effects are more severe with increasing age, and intermediate and long-term effects are associated with a general accelerated aging-like state.

The resilience stressor panel described in this report represents a multisystem approach for preclinical testing of anti-aging therapeutics that could be utilized at an earlier age and more accurately than frailty assessment in the mouse. The panel is ideal because the individual stressors have a combined dynamic range in the response to allow characterization into easily distinguishable levels of resilience. Each test is simple, reliable, and inexpensive so the panel can easily be duplicated by many different groups. The stressors are also relevant to human medicine and aging. The panel therefore has the potential of being an attractive translational perturbation for resilience testing in mice to measure the effectiveness of interventions that target basic aging processes. These stressor tests, either singly or as a panel, could be adapted to humans in the clinic or in the laboratory on primary cells such as myeloid cells or fibroblasts, to approximate resilience to declining dysfunction associated with increasing age.


Exercise Can Reverse Cardiac Secondary Aging Resulting from a Sedentary Lifestyle

It is never too late to exercise in order to obtain benefits to health - there are any number of studies showing beneficial outcomes to result from structured exercise, especially resistance exercise, even for people in very late life. That said, the study of exercise noted here suggests that at some point in middle age it does become too late to reverse consequences of secondary cardiac aging such as hypertrophy, stiffening of heart muscle leading to diastolic heart failure, and the like. Up until that point, however, even the earnestly idle among us can choose to undo some of the portion of overall loss of function that results from a sedentary lifestyle.

What is secondary aging? There is no bright dividing line between primary aging and secondary aging, but one possible definition is that primary aging results from the normal operation of cellular metabolism in a healthy individual in an optimal environment, while secondary aging results from detrimental environmental factors: long-term exposure to toxins or pathogens, lingering latent viral infections, poor diet leading to excess fat tissue, a smoking habit, lack of exercise, and so forth. The reason I say that there is no bright dividing line is that if you look under the hood at the types of damage and molecular mechanisms involved, there is considerable overlap between primary and secondary aging. Chronic inflammation and common ways in which cells can malfunction feature prominently on both sides, for example. Aging is damage, and for many forms of that damage it is a matter of origin and semantics as to whether we consider it a part of aging, the pathology of a disease, a self-inflicted injury, or something else.

Exercise can only take you so far. Given that it is essentially free, and reliably produces benefits, of course everyone should exercise if capable of doing so. But three quarters of the fittest, most diligent people nonetheless die from age-related disease, largely cardiovascular disease, before reaching 90 years of age, and those still alive at 90 are pale shadows of their former, youthful selves. The gains of exercise are small when considered against the bigger picture of what will become possible though near future medical technology. So exercise by all means, but also put some thought towards supporting the development of rejuvenation therapies capable of repairing and reversing the various forms of cell and tissue damage that cause aging. Success in that line of work is the only way forward to live in good health, and with a youthful physiology, for far longer than is presently possible.

Middle-aged couch potatoes may reverse heart effects of a sedentary life with exercise training

The researchers analyzed the hearts of 53 adults ages 45-64 who were healthy but sedentary at the start of the study - meaning they tended to sit most of the time. Study participants received either two years of training, including high- and moderate-intensity aerobic exercise four or more days a week (exercise group), or they were assigned to a control group, which engaged in regular yoga, balance training, and weight training three times a week for two years.

The exercise group committed to a progressive exercise program which monitored participants' recorded heart rates. People in this group worked up to doing exercises, such as four-by-fours - foue sets of four minutes of exercise at 95 percent of their maximum heart rate, followed by three minutes of active recovery at 60 percent to 75 percent peak heart rate. In this study, maximum heart rate was defined as the hardest a person could exercise and still complete the four-minute interval. Active recovery heart rate is the speed at which the heart beats after exercise.

They found that, overall, the committed exercise intervention made people fitter, increasing VO2max, the maximum amount of energy used during exercise, by 18 percent. There was no improvement in oxygen uptake in the control group. The committed exercise program also notably decreased cardiac stiffness. There was no change in cardiac stiffness among the controls. Sedentary behaviors - such as sitting or reclining for long periods of time - increase the risk of the heart muscle shrinking and stiffening in late-middle age and increases heart failure risk.

Previous studies have shown that elite athletes, who spent a lifetime doing high-intensity exercise, had significantly fewer effects of aging on the heart and blood vessels. However, the six to seven days a week of intense exercise training that many elite athletes perform throughout their life isn't a reality for many middle-aged adults, which led researchers to study different exercise doses, including casual exercise at two to three days a week and "committed exercise" at four to five days a week. "We found that exercising only two or three times a week didn't do much to protect the heart against aging. But committed exercise four to five times a week was almost as effective at preventing sedentary heart aging as the more extreme exercise of elite athletes. We've also found that the 'sweet spot' in life to get off the couch and start exercising is in late-middle age, when the heart still has plasticity."

Reversing the Cardiac Effects of Sedentary Aging in Middle Age - A Randomized Controlled Trial: Implications For Heart Failure Prevention

Sedentary aging is strongly associated with deleterious changes in cardiovascular function, including an increase in left ventricular (LV) stiffness. Sedentary seniors have small stiff LVs, which are comparable to patients with heart failure with a preserved ejection fraction (HFpEF). In contrast, competitive athletes have large, compliant LVs equivalent to much younger individuals, suggesting that exercise training, performed at a very high level over a lifetime, may counteract the detrimental effects of aging and inactivity on the LV.

Although competitive athletes are a useful model for characterizing the upper limits of cardiovascular protection from prolonged exercise training, the volume of training performed by these individuals (≥6 days/wk plus competitions) is not feasible for the general population. Although it appears that 4 to 5 days of committed exercise training over decades is adequate to achieve most of this benefit, it is unclear whether exercise training can restore or improve LV compliance in previously sedentary individuals, and if so, when is the optimal stage of life to intervene.

Epidemiological studies show that a measurement of fitness in middle age is the strongest predictor of future heart failure. Moreover, in observational studies, the dose of exercise associated with reduced heart failure incidence is much higher than that associated with reduced mortality. However, if exercise is started too late in life (i.e. after 65 years) in sedentary individuals, there is little effect on LV stiffness. Thus, a lifetime of sedentary aging is associated with a reduction of cardiac plasticity, which cannot be overcome with a year of moderate-intensity exercise training. We recently documented that this LV stiffening begins to be identifiable during middle age with a leftward shift in the LV end-diastolic pressure volume curve. We hypothesize that middle-aged hearts retain some degree of cardiac plasticity and may represent a more optimal time to intervene with aggressive lifestyle modification aimed at improving cardiac stiffness.

This study is the longest, prospective randomized controlled trial that has documented the physiological effects of supervised, structured exercise training in a group of sedentary but healthy middle-aged adults. The key finding is that 2 years of exercise training performed for at least 30 minutes, 4 to 5 days per week, and including at least 1 high-intensity interval session per week results in a significant reduction in LV chamber and myocardial stiffness. The use of high-resolution, invasively measured LV pressure-volume curves and comparison with an attention control group enhances the confidence in this conclusion. This study also demonstrated that exercise training can be adhered to by middle-aged adults over a prolonged period, suggesting that this may be an effective strategy to mitigate the deleterious effects of sedentary aging on the heart and forestall the development of HFpEF.

A Role for Alpha-2-Macroglobulin in the Cancer Immunity of Naked Mole-Rats

Naked mole-rats are near immune to cancer, in addition to living far longer and with far less of a functional decline over the course of a lifetime than is the case for other, similarly sized rodent species. Research into this cancer resistance has so far led to evidence for greater efficiency in cancer suppression genes, particularly with regard to being triggered by cell crowding of the sort that takes place in tumors, and higher prevalence of high molecular weight hyaluronan in naked mole-rat tissues. These are unlikely to be the only factors involved.

Here researchers outline a role for alpha-2-macroglobulin (A2M) in cancer suppression; it appears to inhibit tumor growth in multiple mammalian species through a variety of mechanisms that are as yet not all that well characterized. Naked mole-rats are found to have a very high level of A2M in their tissues, which may be an important component of their resilience to cancer. Older humans exhibit lower levels of A2M than their younger counterparts, which may be one of the numerous contributions to age-related vulnerability to cancer. Unfortunately, A2M interacts with a sizable number of other proteins, which will no doubt ensure that confirmation of its mode of action will require significant further time and investment. Even absent that confirmation, however, there is now evidence of significant tumor suppression in mice through delivery of A2M. That seems quite promising.

The naked mole-rat (NMR), a subterranean rodent, tolerates hypoxia, hypercapnia, avoids many physiological characteristics associated with aging and, most importantly, exhibits pronounced resistance to cancer. Transcriptome analysis of NMR liver compared to wild-derived mice revealed very high expression of cell adhesion molecules involved in tumour development as well as the pan-proteinase inhibitor alpha2-macroglobulin (A2M).

Earlier, we have shown that the level of A2M in human blood decreases with age and exposition of tumour cells with activated A2M (A2M*) inhibited many malignancy-associated properties of tumour cells in vitro by inhibition of members of the WNT/ß-catenin pathway. Therefore, we hypothesized that the reduction of A2M in aged humans may facilitate tumour development. A2M is capable of binding to most proteinases and many growth factors, hormones, and cytokines. Binding to its receptor, the low density lipoprotein receptor-related protein 1 (LRP1, also known as CD91), mediates fast clearance of tethered peptides and proteins. A specific role of A2M in cancer cell metabolism and development has not been elaborated in detail yet.

Here we show that A2M* modulates tumour cell adhesion, migration, and growth by inhibition of central signalling pathways such as phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), and SMAD. A2M* up-regulates the tumour suppressor PTEN, CD29, and CD44 but does not evoke epithelial-mesenchymal-transition (EMT). Furthermore, A2M* was found to down-regulate microRNA-21 (miR-21), which is a dominant inhibitor of PTEN expression.

Notably, A2M* inhibits growth of tumours in nude mice independent of their origin, and induces tumour necrosis in tumour tissue and tumour slices cultures. Transcriptome analysis displayed fundamental and unexpected insights in regulatory power of this ancient and highly conserved human plasma protein. The unique features of using A2M* as a novel anti-tumorigenic therapeutic in cancer patients prompted us to perform this study: increasing the fraction of activated A2M* in humans might represent a novel approach for cancer prophylaxis and treatment.


Clonal Expansion of Stochastic Nuclear DNA Damage as a Contributing Cause of Aging

Damage to the nuclear DNA in our cells is constant and ongoing, either due to reactive molecules, or errors during replication of DNA. Near all of this damage is rapidly and successfully repaired by a panoply of highly efficient maintenance processes. Nonetheless, damage slips through to accumulate over a lifetime, particularly in long-lived cell populations. The most obvious consequence of this damage is cancer, resulting when the blueprint driving cellular operations changes in ways that allow unfettered and uncontrolled replication. Other than cancer, however, does this random damage to cells in fact contribute meaningfully to aging, through disarray in normal cellular metabolism? The consensus is that it does, but there are dissenters from that view, as well as evidence to cast doubt on a necessary causal connection between high levels of stochastic DNA damage and age-related disease and mortality.

The authors of the open access paper noted here consider that the more important aspect of stochastic DNA damage is not its occurrence, but the degree to which it is then replicated: that some DNA damage does result in significant replication of cells containing that damage, even in the absence of cancer. This is a somewhat more plausible argument for a connection to tissue dysfunction than is stochastic DNA damage on its own. It would require far fewer persistent mutations in individual cells in order to produce resulting changes in tissue or organ function, and it dovetails fairly well with what is observed in the DNA of old tissues with more modern genetic technologies.

DNA encodes the basic instructions to construct an organism during its development, and its stability is essential to life. However, DNA mutations are also necessary for evolution because they provide the requisite genetic variation for natural selection. Thus, opposing forces act on DNA maintenance: stability to preserve the quality of the genetic information within individuals and instability to warrant intergenerational genetic diversity.

For new genetic information to have its phenotypic effect, the zygote must divide and clonally expand during embryonic development. While the cells that make up the resulting organism may differ in morphology and physiology, their underlying genetic code should be, in principle, identical. However, much like how genetic variation drives selection within organismal populations, genetic variation arising within a single individual enables selection for or against somatic cells. The stochastic nature of mutagenesis, the sparse gene content of the human genome, and the limited degeneracy of the genetic code imply that most mutations have neutral or deleterious consequences. Occasionally, however, mutations provide a selective advantage that leads to the expansion of the mutant cell into a clone. This process can be influenced by the timing of mutations during an organism's lifecycle, their frequency, and their functional consequence to a cell's physiology. The result is genetically distinct populations of cells within an individual, a phenomenon known as somatic mosaicism.

The existence of somatic mosaicism is well documented. However, the occurrence of somatic mosaicism is not limited to development and has been recognized as an aging phenotype for decades. An increase of somatic mutations with age has been reported for a variety of target genes. Similarly, age-associated accumulation of chromosomal alterations has been documented. These early findings appear to be only the tip of an iceberg in terms of somatic mutations in normal tissue. The advent of Next Generation Sequencing (NGS) technologies has led to the striking revelation that older individuals not only accumulate chromosomal alterations but also abundant mutations in cancer driver genes. As error-correction NGS (ecNGS) technologies have improved the limit for mutation detection, the prevalence of cancer-associated mutations in adults now appears close to 100%.

Furthermore, recent single-cell studies point to the possibility that essentially all cells have unshared mutations in their genomes. In view of this extensive genetic diversity, it is perhaps not surprising that mutations that confer a proliferative advantage are readily detected as clonal populations of increasing abundance and size in the elderly. These clonal populations might lead to loss of organismal health through the functional decline of tissue and/or the promotion of disease processes, such as cancer. In this review, we summarize recent research that supports the notion that aberrant clonal expansion (ACE) resulting from cancer-associated mutations are common in noncancerous tissue and accumulate with age. We propose ACE to be a previously underappreciated aging phenotype that is universal in most organisms, affects multiple tissues, and likely helps explain why aging is the biggest risk factor for cancer.


Aubrey de Grey on Rejuvenation Research: How Big and How Near are the Benefits?

Aubrey de Grey of the SENS Research Foundation was back again to present to rank and file Google employees recently as a part of the Talks at Google series. The SENS perspective on aging is easy to summarize at the high level: aging is caused by accumulated molecular damage in cells and tissues; here is the evidence-supported list of types of damage; here are a set of ways to repair that damage, all of which could be constructed in a decade or two given the funding. It is an engineer's view of aging as a harmful phenomenon that should be fixed, with the high priority given to that fix derived from the fact that aging causes more suffering and death, by far, than any other part of the human condition. That SENS is as much straightforward, logical engineering as scientific research probably explains why members of the software engineering community have, right from the start, made up a sizable fraction of those who helped to fund SENS research. It resonates: break down the problem to its roots, assemble the facts, assess them, act on them.

Aubrey de Grey, PhD: "The Science of Curing Aging" | Talks at Google

Aubrey de Grey, Chief Science Officer, presents the SENS Research Foundation's current research into therapies that may add decades of healthy life for people who are adults today, as well as work that the Foundation has already spun out into successful startups. Dr. de Grey also explains how SRF's work fits within the context of the global anti-aging research effort and why it has gained broad expert support.

As de Grey points out in the talk here, if this is so straightforward, why does he have to tour the world canvassing support for the cause of rejuvenation research? There are two categories of challenge here. The first is that the bulk of the scientific community will not on their own initiative raise funds to work on most lines of rejuvenation research, at least not until it is obvious beyond refutation that a particular approach will work - which means animal studies showing significant, reliable life extension at a minimum. It is an exceeding conservative, risk-averse community. Look at senescent cell research before and after the 2011 demonstration of extended life in progeroid animals through destruction of senescent cells, for example. Before that point, there was next to no funding, and very few researchers made any effort to look into this area, despite the fact that decades of evidence strongly supported a role for cellular senescence as a cause of aging. The study itself was funded via philanthropy, rejected by the established funding institutions. In the few years afterwards, an avalanche of interest and funding arrived, leading to senolytic drug candidates and the present brace of startups bringing rejuvenation through senescent cell clearance to the clinic.

But that still leaves numerous lines of rejuvenation research that are just as promising, just as likely to produce sizable effects on health and reversal of aging, and yet the research community largely ignores them. Glucosepane cross-link breaking to reverse loss of tissue elasticity, for example. The philanthropy of the SENS Research Foundation and related groups is the only reason there is any significant progress in these areas - yet as soon as the first studies are in hand to show significant results on animal aging, exactly the same will occur there as did for senescent cell clearance. All it takes is sufficient funding to build the first technology demonstrations.

The second form of challenge is that the public at large is not engaged in any way with their future decline via aging. People react poorly to being directly challenged on aging as a source of pain, misery, and death. They deploy environmentalist and class envy arguments against deploying medicine to help turn back aging and lengthen life, while at the same time supporting causes such as cancer research or Alzheimer's research. Which is exactly the same thing under the hood! Few individuals argue for a halt to cancer research because too few people are dying and too many people are living longer, or because some people will get the treatments before others, and yet the average fellow in the street might well respond with concern on the topic of treating aging as a medical condition, exactly because there would be less suffering, less death, or because the third world will not immediately benefit.

All told, strange confusions and misapprehensions regarding aging and the potential to reverse aging are widespread out there. People mistakenly believe that therapies will be so expensive as to be restricted to the elite. Or that therapies will maintain people in a state of increasing decrepitude rather than making patients younger and healthier for longer. Or that resources will run out if people live even a little longer. This manifests in practice as a lack of readily available philanthropic funding at larger scales, needed to solve the first challenge noted above, the production of technology demonstrations to persuade the scientific community. We all have to work a lot harder than is the case for other, related causes in medicine to fund the early stage rejuvenation research needed to turn back the causes of aging. This is why we must conduct advocacy for the cause.

MCP-1 as a Potential Biomarker of Biological Age

Researchers here add one more correlation between blood biochemistry and aging to the growing list. The greater the number of simple measures that can be associated with age-related decline, the more likely it is that researchers can find an algorithmic combination of those measures that quite accurately reflects biological age. At the moment epigenetic clocks based on assessment of DNA methylation patterns are leading the pack of potential biomarkers of aging because they are in effect a combined set of smaller measures, those being made by the cells themselves. Many specific DNA methylation changes are reactions to the cellular damage and dysfunction of aging. However, other approaches to combining measures of aging and cellular reactions may turn out to be better in the end. We shall see in the years ahead.

Generally agreed upon, robust, cheap, and reliable biomarkers of aging are important because they will greatly accelerate the pace of development in aging research. Currently the field lacks a good, rapid way to assess the outcome of a potential intervention to slow or reverse the aging process. The only widely accepted approach is to carry out life span studies, and that means that any sort of debate over viability or quality or strategy will drag on for years, and cost millions that might have been invested elsewhere. Mouse life span studies are not cheap. If the field is instead equipped with an assessment of biological age that can run immediately before and immediately after a treatment, then exploration and validation in aging research will become far more rapid and far less costly. The best approaches, most likely something along the lines of the SENS damage repair strategy, will win out more rapidly.

Aging is the major risk factor for numerous chronic diseases and is responsible for the bulk of healthcare costs. To address this healthcare crisis, there is a growing interest in identifying ways to therapeutically target aging in order to prevent, delay, or attenuate multiple age-related diseases simultaneously. A number of therapeutic strategies have emerged. However, a major barrier to clinical trials targeting aging is the prolonged time between intervention and clinical outcomes. For these studies, surrogate endpoints will dramatically improve the economy and timescale in which we can measure the effects of interventions on biological age.

Biological age is defined by the health or fitness of an individual, and lack of age-related diseases, irrespective of their chronological age. Biological age can be quite distinct from chronological age. For example, cancer survivors are biologically older than their chronological age due to exposure to genotoxic agents, while centenarians are frequently biologically younger than their chronological age. A biomarker of biological age in accessible bodily fluids or tissues would be extremely valuable for clinical trials testing antigeronic factors, but also potentially for triaging patients facing onerous therapeutic procedures. Hundreds of studies have aimed to discover age-related changes in circulating factors including metabolites, advanced glycation end-products, exosome content, miRNA, and inflammatory molecules, with varying success.

Here, we identified MCP-1/CCL2, a chemokine responsible for recruiting monocytes, as a potential biomarker of biological age. Circulating MCP-1 levels increased in an age-dependent manner in wild-type (WT) mice. That age-dependent increase was accelerated in Ercc1-/Δ and Bubr1H/H mouse models of progeria. Genetic and pharmacologic interventions that slow aging of Ercc1-/Δ and WT mice lowered serum MCP-1 levels significantly. Finally, in elderly humans with aortic stenosis, MCP-1 levels were significantly higher in frail individuals compared to nonfrail. These data support the conclusion that MCP-1 can be used as a measure of mammalian biological age that is responsive to interventions that extend healthy aging.


Links Between Induced Pluripotency and Cellular Senescence

Cellular senescence is one of the causes of aging. Lingering senescent cells produce the senescence-associated secretory phenotype, a damaging mix of secreted molecules that generate inflammation and tissue dysfunction. However, senescence is also an early defense against cancerous cells, especially those that gain the embryonic-like ability to replicate without limit and spawn many different cell types. Such cells are near all shut down and destroyed by the senescence process, at least in the earlier stages of life. Further, cellular senescence is also involved in tissue repair in a different, transient way. Wounds spur the temporary creation of senescent cells, which appear important in the coordination of healing.

Reprogramming normal cells into induced pluripotent stem cells is an important part of modern stem cell research, a basis for future regenerative therapies, and a potential way to produce arbitrary patient matched cell types to order. Yet it is in essence quite similar to the damage and mutation that produces rampaging cancer cells, freed from their restrictions. It also has more than a passing relation to the activities that take place during regeneration. Given this, we might not be too surprised to find links between cellular senescence and induced pluripotency. The paper here outlines some of these connections, and they are most interesting. This will probably have implications for a range of future efforts to control cellular activity in the body. For instance, inducing pluripotency in living animals has been tried, and at least in the short term shown to be beneficial - the contents of this paper put a novel spin on the sort of cautions that line of research might inspire.

Senescence is a cellular response to damage characterized by a stable cell cycle arrest and by the secretion of cytokines and other soluble factors with pleiotropic functions, collectively known as senescence-associated secretory phenotype or SASP. The primary role of senescence is thought to be the orchestration of tissue remodeling and repair. This has been demonstrated in a variety of settings, including tissue repair in the skin and liver. In general, senescent cells are efficiently cleared as part of a successful tissue repair process. However, upon severe or chronic damage, senescence-orchestrated tissue repair may fail and senescent cells may accumulate, contributing to disease and aging.

The power of cellular senescence in inducing tissue remodelling has been further extended to processes of cellular reprogramming in vivo. The transgenic expression of the four transcription factors abbreviated as OSKM (Oct4, Sox2, Klf4, and c-Myc) in adult mice induces dedifferentiation and cellular reprogramming within multiple tissues. However, in addition to reprogramming, the activation of OSKM also results in cellular damage and senescence. Therefore, OSKM induces two opposite cellular fates, namely senescence and reprogramming, that coexist in vivo in separate, but proximal, subsets of cells. Importantly, it has been demonstrated that senescence plays an active role in facilitating in vivo reprogramming through the paracrine action of the SASP, with interleukin-6 (IL6) as a critical mediator. Of note, IL6 plays an important role also during in vitro reprogramming. Moreover, the concept that senescence promotes cellular plasticity has been further extended to the activation of somatic stem/progenitor cells. In particular, the SASP can confer somatic stem/progenitor features onto proximal epithelial cells in several tissues.

The tumor suppressor genes p53, p21, Ink4a, and Arf act as cell-autonomous barriers for cellular reprogramming. These barriers are conceivably activated by cellular damages associated to reprogramming, most notably replication stress, which result in proliferation arrest and, consequently, inhibit reprogramming. At the same time, p53 and the genetic locus Ink4a/Arf also affect reprogramming, although in opposite directions, through cell extrinsic mechanisms. In the absence of p53, the induction of OSKM leads to exacerbated damage and senescence in tissues, which results in high levels of IL6 that further enhance reprogramming. The Ink4a/Arf locus plays a complex role in reprogramming: it promotes reprogramming through the paracrine influence of senescence, and, at the same time, it is a cell-autonomous barrier for reprogramming. In vivo, the absence of Ink4a/Arf severely impairs OSKM-senescence, IL6 levels are modestly increased, and reprogramming is very inefficient. Therefore, the positive cell-autonomous impact of Ink4a/Arf deficiency is completely obscured in vivo by the absence of senescence and IL6 secretion. The emerging picture is that tissue damage and senescence provide a tissue microenvironment that is critical for OSKM reprogramming in vivo.


Commercial Success Would Solve Most of the Challenges of the Cryonics Community

Cryonics refers to the long-term storage of people at liquid nitrogen temperatures, starting as close to clinical death as possible, and involving cryoprotectant-induced vitrification of tissues rather than freezing. The goal is preservation of the fine structure of the brain, as that is where the data of the mind is encoded. Given a good enough preservation, a sufficient storage of the mind, then the possibility of later restoration exists, based on the advances in biotechnology and molecular nanotechnology foreseen for the coming century. Cryonics is thus an important service, albeit one that receives little attention and funding. Despite that thin profile, cryonics providers have nonetheless survived and evolved over more than four decades. Several hundred people are now preserved for the long term, and this option remains the only alternative to the grave for the countless others who will age to death prior to the advent of comprehensive rejuvenation therapies.

The primary challenges faced by the cryonics industry all relate to the small size of the community. It is largely non-profit, with only a few distinct organizations - the long-established non-profits Alcor and Cryonics Institute, and relative newcomers KrioRus, CryoSuisse, and some smaller groups in other countries that have yet to build a viable provider organization. Everyone knows everyone else. The resources available for operations, research, and expansion are small in scope. The number of people joining the community each year to contribute meaningfully in some way is similarly small. There have been instances in past years of the sort of cabin fever and clashes of personality that tend to occur in small, largely volunteer and non-profit communities. Anyone who has spent time in passionate movements knows how this goes when growth to the next stage doesn't materialize. People are people.

Cryonics is a long-term project, much more so than rejuvenation research. The framework of a rejuvenation toolkit should be largely sketched out, with first and second generation clinical applications available in all of its categories, twenty years from now, adding a significant number of years to health and life expectancy at 60 or 80. After that, it is a matter of filling in the spaces and incremental improvement, following the usual cycle of growth for a broad area of technology. For cryonics, on the other hand, one has to delve deeply into speculation on technological progress to, say, make the argument that it will be a plausible goal to reverse the cryopreservation of an individual in 2050 who was preserved using the methods of 2050. Maybe that could be achieved, maybe not. Repairing people preserved in the 20th century with no vitrification or partial vitrification and a fair load of ice crystals and fracture damage is a whole other story, however, something that will require mature molecular nanotechnology of the sort that may not emerge until much later in the century. But everything much past 2040 is very challenging to predict.

That cryonics is a long-term project puts a great deal of pressure on the community to engage younger members. There are enough of the prime of life folk at present to take over from the second generation leadership as needed in the years immediately ahead - the first generation who led in the 1970s and 1980s being retired, cryopreserved already, or more permanently dead and gone. But what comes afterwards? The longest standing cryonics organizations are 40 years old, give or take, and they may well have to continue for another century. There are many organizations, companies even, considerably older than that span of time. But how did they survive over generations? They did so through the size of their extended communities: workers, supporters, customers, patrons. Continuity of culture and commitment requires community, and when that community is small there is the very real risk of it sputtering out, as small communities have done since time immemorial.

The solution to all of this is growth. But how? The cryonics community has for four decades sought growth primarily through membership, through individuals signing up for the service of cryopreservation. This has been a very slow bootstrapping process. There are thousands of us, but not very many thousands, and most are entirely silent partners in this endeavor. That process will continue grinding away, but I don't think anyone should count on a sudden explosion of interest in the membership model of cryopreservation any time soon. If that was going to happen, it has had many opportunities to do so.

I would say that for growth in the community over the next twenty years, we should be looking more to customers than to supporters of other sorts. That growth could arrive from the array of technological spin-offs that can be produced from the methodologies of cryonics and related cryobiology. In particular indefinite tissue preservation via vitrification, something that is beginning to look plausible for whole organs. Reversible vitrification of large tissues such as whole organs is on the near horizon, a capability that would revolutionize the organ donation and transplantation industry. Members of the cryonics community are well aware of this, and efforts to find commercial growth have in fact been underway for years. This includes companies founded by community members, such as 21st Century Medicine and Arigos Biomedical. This, also, has proven to be a tough road - but I think it one with a better chance of opening up the cryonics industry to greater investment and attention than other approaches.

In a better world than ours, cryonics as an industry was implemented and sizable by the mid-20th century, soon after low enough temperatures could be reliably maintained indefinitely, and sufficient knowledge of cryoprotectants was established. It spread, replacing the funerary industry as the primary end of life choice. Instead of billions of graves and markers of individual extinction, billions of stored brains would be awaiting the chance to live again in a better, brighter future of limitless resources and expansion of humanity to the stars. This is still a goal that could be achieved in the years ahead, a way to dramatically reduce the number of people permanently lost to oblivion. First, however, the small, essential, and largely overlooked cryonics community needs to find its path to growth.

A Call to Test Combinations of Drugs Shown to Slow Aging in Animal Studies

I expect that little progress towards sizable human life extension will be achieved in the next few decades via pharmaceuticals that slow aging through triggering various stress response mechanisms. This includes calorie restriction mimetics, autophagy enhancers, exercise mimetics, and the like. It may well be the case that researchers come up with a few drugs that, if taken regularly for decades, reliably add a few years to life expectancy and improve health in old age to a degree that is in the same ballpark as the present results of exercise or eating a better diet. Is that worth billions in funding and decades of dedicated time from much of the research community, however? I think not, not when exercise and calorie restriction are free, and there is the much more promising field of rejuvenation research to focus on. Why tinker with slightly slowing the damage that causes aging when it is possible to work towards repair of that damage and thus reverse aging?

Still, the institutions focused on pharmaceutical recapture of stress responses are deeply entrenched, currently commandeering the majority of funding and attention. Even in failure, the work will continue out of sheer inertia. One would imagine that, in years ahead, researchers will start to try combinations of drugs that slow aging in mice and did not work out so well in humans, looking for synergies or additive effects. One would hope that at least some instead give up the strategy as a bad deal and turn their attention to rejuvenation research, but I expect that to be a slow and grudging process for much of the research community. The more support that we can give to organizations pushing the rejuvenation research agenda into clinical trials and proof of effectiveness, the better.

Aging is a complex multifactorial process, meaning that multiple pathways need to be targeted to effectively prevent or slow aging. A number of molecular pathways are well known for influencing aging, but only a few have been successfully targeted with individual drugs, and these drugs do not individually target all aging pathways. However, combinations of these drugs might have the potential of effectively broadening the scope of aging targets. There are a number of drug combinations that could be combined based on different but overlapping pharmacological activities. Since the number one criterion for selecting drugs should be based on known anti-aging effects, for example, in preclinical mouse studies, the number of drugs available to consider is markedly reduced. Three drugs with well-validated anti-aging effects in laboratory animals, rapamycin, acarbose, and SS31, are well suited to therapeutic multiplexing as a way to enhance healthy aging and stop the development of lesions associated with aging and physiological dysfunction based on interactive cellular mechanisms of each drug.

The concept of drug multiplexing to slow aging looks good on paper, but drug combinations have yet to be tested in any meaningful way. Historically, testing single drugs in mouse lifespan studies has provided useful information, but it is costly and time consuming. More importantly, lifespan studies are difficult to recapitulate in humans, making translation of the preclinical information challenging. And especially relevant is the fact that lifespan studies in mice are not well-suited to testing drug combinations that could more effectively target multiple factors involved in aging. Thus, new paradigms for testing therapeutics aimed at slowing aging are needed.

While the future for expanded use of drug combinations in treating various diseases and conditions, including aging, is highly promising the path toward eventual regulatory approval can be challenging and should be considered in any preclinical studies undertaken. The potential beneficial functional synergy gained from the logical and judicious use of rational drug combinations, such as rapamycin, acarbose, and SS31, is obviously complicated by the fact that different drugs with different metabolic, pharmacokinetic, and toxicity profiles are being superimposed on top of one another. Focusing not just on the benefits of combination products but also the potential liabilities early on can speed the development process.

In summary, the concept of drug multiplexing as a powerful platform to slow aging is promising but has not yet entered the mainstream of aging research. The combination of rapamycin, acarbose, and SS31, three drugs with individually documented anti-aging effects, is a logical approach designed to complement mechanisms of action of their molecular targets and robustly enhance a delay of aging and age-related disease not seen with mono-therapeutic approaches. Support for the preclinical investigation of this drug combination as well as other drug combinations is urgently needed to determine dosages, frequency of administration, and criteria for when to start administering the drugs, i.e. focus on treatment at older ages, or prevention at younger ages.


Viruses and Checkpoint Inhibitors Combine to Form an Effective Cancer Treatment

Researchers here demonstrate a combination therapy that is far more effective in destroying a target cancer than either of its components alone. Effective synergies between therapies are discovered at a fairly low rate by the scientific community, which is in part a reflection of their rarity, but also a reflection of the fact that the regulatory system is not set up to encourage the commercial development of combination therapies. The number of trials for such efforts is small in comparison to single therapy tests. There isn't a good response to this observation beyond the usual calls for more freedom and more funding.

Immunotherapy, which helps the body's immune system attack cancer, has revolutionized treatment for cancers such as melanoma and leukemia. However, many other kinds of cancer remain resistant. A new study suggests that a combination of two immunotherapies (oncolytic viruses and checkpoint inhibitors) could be much more successful in treating breast cancer and possibly other cancers. "It was absolutely amazing to see that we could cure cancer in most of our mice, even in models that are normally very resistant to immunotherapy. We believe that the same mechanisms are at work in human cancers, but further research is needed to test this kind of therapy in humans."

The researchers studied three mouse models of triple negative breast cancer, and found that all were resistant to a checkpoint inhibitor which is commonly used to treat other kinds of cancer. They also found that while an oncolytic virus called Maraba could replicate inside these cancers and help the mouse's immune system recognize and attack the cancer, the virus alone had minimal impact on overall survival.

The researchers then tested the virus and checkpoint inhibitor together in models that mimic the metastatic spread of breast cancer after surgery, which is very common in patients. They found that this combination cured 60 to 90 percent of the mice, compared to zero for the checkpoint inhibitor alone and 20 to 30 percent for the virus alone. In these models, the virus was given before the surgery and the checkpoint inhibitor was given after. "When you infect a cancer cell with a virus, it raises a big red flag, which helps the immune system recognize and attack the cancer. But in some kinds of cancer this still isn't enough. We found that when you add a checkpoint inhibitor after the virus, this releases all the alarms and the immune system sends in the full army against the cancer." Ongoing clinical trials are testing oncolytic viruses (including Maraba) in combination with checkpoint inhibitors in people with cancer.


Vesicles from Young Cells Reverse Measures of Aging in Old Stem Cells

Much of the constant signaling that takes place between cells is carried via microvesicles and exosomes, membrane-bound packages of molecules. Researchers are finding that the contents of vesicles change in characteristic ways with advancing age, one of the many cellular reactions to rising levels of molecular damage and environmental stress. Some of these changes might be useful as a marker of cellular senescence, one of the more important changes in cell state associated with age. It should also be possible to use suitably formed vesicles to adjust cell behavior in situ, such as to spur greater regeneration. Perhaps these vesicles are harvested from young cells, or perhaps they might be manufactured directly. Many of the current class of widely used cell therapies might in theory be replaced by delivery of vesicles, as the cell therapies achieve their beneficial results via signaling, not other cell activities.

Another of the more important changes in cell state that occurs with age is the decline in stem cell activity. Stem cells are responsible for providing a supply of somatic cells for tissue maintenance and regeneration, and the progressive loss of that supply contributes to the gradual failure of tissue and organ function in later life. There is ample evidence to suggest that, at least in the stem cell populations most studied to date, such as those supporting skeletal muscle tissue, this is at least as much a problem of signaling as it is a problem of damage to the cells themselves. The stem cells react to the state of damage and behavior of other cells in the niche that supports them, as reflected in the signal molecules they receive. The current consensus in the scientific community is that this response to the damage of aging evolved to reduce cancer risk, one part of the current human life span as a balance between death by cancer versus death by slowly declining tissue function.

As research community interest in vesicle signaling picks up, we should expect to see more in the way of research results such as the one below, in which scientists find that delivery of vesicles from young niche cells can restore more youthful function to aged hematopoietic stem cells, the population resident in bone marrow and responsible for generating blood and immune cells. It seems plausible that we stand at the verge of an important shift in focus for the field of regenerative medicine, a change based on an improved understanding of how cells influence one another via signaling processes, and the identification of which of these signals are important determinants of the changes in regeneration and stem cell activity that occur over the course of aging.

Intercellular Transfer of Microvesicles from Young Mesenchymal Stromal Cells Rejuvenates Aged Murine Hematopoietic Stem Cells

Donor age is one of the major concerns in Bone Marrow Transplantation (BMT). Studies on murine system have demonstrated that aged marrow harbors increased pool of hematopoietic stem cells (HSCs) exhibiting myeloid bias and having compromised competitive repopulating ability. Aged HSCs also exhibit multiple epigenome and transcriptome changes. DNA damage, replication stress, and ribosomal stress have been shown to cause aging of HSCs. Age-associated changes in human HSCs were similar to those observed in mouse HSCs, suggesting that hematopoietic aging is an evolutionarily conserved process. A retrospective study done in BMT patients showed age as the only donor trait associated with their overall and disease-free survival.

Since donor age is such an important concern in BMT, it might be argued that the upper limit of donor age may be lowered. However, patients having an older individual as the sole matched donor could be denied access to this potentially life-saving treatment. To overcome this impediment, efforts are being made to rejuvenate aged HSCs to improve their performance. Here we report a novel finding that a brief exposure of aged HSCs to young mesenchymal stromal cells (MSCs) rejuvenates them via intercellular transfer of microvesicles (MVs) containing "youth signals". We also demonstrate that intercellular transfer of aged exosomes carrying negative regulators of autophagy causes aging of HSCs. Our data are relevant in both allogenic as well as autologous transplantations involving older individuals as donors and recipients, respectively.

Rejuvenation of aged HSCs prior to transplantation could expand the donor cohort and also help older individuals undergoing autologous stem cell therapy. Application of the MSCs as well as MVs in clinical BMT/SCT might be logistically straightforward, since they can be cryopreserved as "ready-to-use" reagents. Use of pharmacological compounds to rejuvenate aged stem cells in general, and aged HSCs in particular, is being pursued to gain clinical advantage. However, most pharmacological compounds could show off-target effects and they also regulate diverse processes and pathways. Therefore, use of clinical grade "cellular products" in manipulating HSCs, albeit expensive, would be a safer approach than the direct application of pharmacological tools on them.

Reduced autophagy is associated with aging, whereas stimulation of autophagy is speculated to have anti-aging effects. Aged HSCs having high autophagy levels are known to preserve their regenerative capacity. Here we provide a direct evidence for this hypothesis. We demonstrate that young MSCs transfer autophagy initiating mRNAs to the aged HSCs via intercellular transfer of MVs, leading to their rejuvenation. ATG-7 is a critical component of the autophagy pathway and has been shown to be essential for the maintenance of human CD34+ HSCs. Here we show that young MSCs and their MVs transfer Atg7 to aged HSCs.

FOXO3a has been linked to longevity in multiple population studies. FOXO3a is known to stimulate autophagy in primary mouse renal cells. Similarly, FOXO3a inhibition or depletion prevents autophagy induction by starvation in vivo in mouse muscle, confirming a strong link between transcription factors of the FOXO family and autophagy. We found that aged HSCs treated with young MVs show high levels of FOXO3. In the light of these reports, our data clearly demonstrate that direct transfer of MVs containing autophagy-inducing mRNAs seems to be one of the important mechanisms involved in rejuvenation of aged HSCs by young MSCs.

Myeloid bias of HSCs has been considered as a hallmark of their aging. This has been attributed to an accumulation of myeloid-biased HSCs in the aged marrow. In transplantation between old and young individuals, microenvironment-mediated myeloid skewing has been demonstrated. Here, we report a novel finding that myeloid bias of aged HSCs could also be a non-cell-autonomous process involving intercellular communication mechanisms. We demonstrate that aged MVs contain higher levels of Itga2b, which is a myeloid commitment marker, whereas young MVs contain higher levels of IL7r, which is a lymphoid commitment marker. Importantly, we show that partitioning of these mRNAs depends upon the levels of activated AKT in the stromal cells.

Thus, a continuous transfer of aged MVs containing Itga2b to the HSCs could impose a myeloid bias in them, and this coupled with their low levels of apoptosis, could lead to the accumulation of aged HSCs in the marrow. Our data strongly suggest that the lineage bias of HSCs could be dictated by the mRNA profile of the MVs transferred to them, which in turn depends on the signaling mechanisms prevailing in the stromal cells. This aspect needs further investigation. Nonetheless, our findings have certainly added a new dimension to the existing academic debate.

More on Efforts to Tissue Engineer Skin with Hair Follicles

Skin is one of the obvious initial targets for tissue engineering, as it is possible to grow in thin sheets without the need to solve the challenge of generating vascular networks to support larger, thicker tissue structures. Researchers have been making progress towards more complete, complex engineered skin, such as through the inclusion of functional hair follicles or sweat gland structures. The research noted here is an example of the type, though one should always be wary of publicity materials that claim researchers to be first to a specific goal in tissue engineering. It is more often the case that several different groups are in progress at at a similar stage for any given advance in this field. It is a very well funded and diverse area of research; few groups are the only ones working on their specific tissue type and methodological focus.

Researchers have cultured the first lab-grown skin tissue complete with hair follicles. This skin model, developed using stem cells from mice, more closely resembles natural hair than existing models. Although various methods of generating skin tissue in the lab have already been developed, their ability to imitate real skin falls short. While real skin consists of 20 or more cell types, these models only contain about five or six. Most notably, none of these existing skin tissues is capable of hair growth.

Researchers originally began using pluripotent stem cells from mice, which can develop into any type of cells in the body, to create organoids that model the inner ear. But the team discovered they were generating skin cells in addition to inner ear tissue, and their research shifted towards coaxing the cells into sprouting hair follicles. The team's recent research demonstrates that a single skin organoid unit developed in culture can give rise to both the epidermis (upper) and dermis (lower) layers of skin, which grow together in a process that allows hair follicles to form the same way as they would in a mouse's body.

While the researchers were unable to identify exactly which types of hairs developed on the surface of the organoid, they believe the skin grew a variety of hair follicle types similar to those present naturally on the coat of a mouse. The skin organoid itself consisted of three or four different types of dermal cells and four types of epidermal cells - a diverse combination that more closely mimics mouse skin than previously developed skin tissues. By observing the development of this more lifelike skin organoid, the researchers learned that the two layers of skin cells must grow together in a specific way in order for hair follicles to develop. As the epidermis grew in the culture medium, it began to take the rounded shape of a cyst. The dermal cells then wrapped themselves around these cysts. When this process was disrupted, hair follicles never appeared.

After discovering this recipe for lab-grown hair follicles, the researchers must now work to overcome a new roadblock in the study of in vitro hair development - physical limitations that prevent the hairs from shedding and regenerating. The shape of the tissue in culture causes the hair follicles to grow into the dermal cysts, leaving them with nowhere to shed. Nonetheless, the team thinks the mouse skin organoid technique could be used as a blueprint to generate human skin organoids.


Laura Deming's Introductory Overview of Aging Research

Laura Deming runs the Longevity Fund, and has a research background in the study of aging. It seems likely that the fund will do well on the basis of having invested in Unity Biotechnology alone, even putting aside any other successes. The article here is a useful overview, with copious references, of the type of work presently taking place in the aging research community. It well illustrates that, aside from senescent cell clearance, nearly everything that counts as a major interest by funding and number of scientists involved is a form of tinkering with stress response biochemistry to modestly slow aging - not addressing root cause molecular damage by repairing it, but rather messing with metabolism to slow damage accumulation. Nowhere near as helpful.

Given what we know, where the data exists to compare outcomes between short-lived and long-lived species, the approach of altering metabolic processes to enhance beneficial stress response mechanisms is not going to move the needle all that far in humans. The results should be exercise-like and calorie-restriction-like in that they have worthwhile effects on long-term health, assuming that the cost of development and treatment is low, but they won't add much more to life expectancy than those two items are capable of achieving - which means perhaps the low end of five to ten years at best in our species, assuming life-long commitment to the intervention. Given that senescent cell clearance is a going concern, and other damage repair approaches such as cross-link breaking should follow in the years ahead, we can hope that the focus of the research community will shift as other approaches prove themselves much more cost-effective and successful.

As you get older, the chance that you will die goes up. As you get older, the chance that you will die from certain diseases also goes up. Why does this happen? A simple explanation would be that, like an old car, you accumulate damage in a random fashion. However, there are many simple things that we can do to make animals live longer. Why? We don't really know. Eating less makes mice live longer. Some genes, when mutated, make mice live longer. A few drugs, approved for human use, also make mice live longer. So what is the study of aging? I sum it up as the following: trying to figure out what kinds of damage accumulate with age, how to reverse that accumulation, and the search for switches that we could flip in human biology to increase lifespan.

In the 1930s, investigators wanted to do an experiment to see if stunted growth rates during the Great Depression might impact lifespan. They tested this in rats by feeding them less food than they would normally eat. To their surprise, this actually made the rats live longer! This was a seminal discovery. For the first time, we changed the environment of an animal to make it live longer than it normally would. Since then, investigators have tried to uncover how this works. While long-term human studies are sparse, investigators have run two caloric restriction experiments in monkeys, one of which showed promising results for an increase in survival.

In papers published in 1983-1993, investigators introduced the concept that a gene could control lifespan. Previously we'd known that caloric restriction could make animals live longer, but scientists found mutant genes that could make worms live longer. The first gene found encoded a protein that is similar to insulin-like growth factor and insulin receptors in humans. In mice, mutating members of both of those pathways can increase lifespan. One of the longest-lived mouse mutants we have today is a dwarf mouse. In one study, people with similar dwarf mutations seemed to suffer less age-related disease than their non-mutated relatives.

A paper published in the 70's showed that linking old and young female mice so that they share a bloodstream increased lifespan. Then, in 2011, a succession of papers came out showing that this procedure and others like it made mice better at remembering things, and improved heart and muscle function with age. These discoveries increased excitement and interest in the field, and lead to a wave of startups. Investigators in the field have proposed many possible causes for this phenomenon. Proteins, small vesicles, or cells in the young mouse cleaning the blood of the old mouse might all be part of the effect. Many companies are trying to figure out whether there is a special protein or molecule involved.

As you get old, so do your cells. But some of your cells get old in a way that is much worse than the others. If the cell refuses to die even when it stops working, and starts secreting signals to the immune system, we call that a 'senescent cell'. What happens when you get rid of these cells? Investigators found that getting rid of senescent cells in normal mice made them live a longer healthy lifespan. Knocking out senescent cells is tricky, because they don't have many unique identifiers. Companies are working to either find things empirically that kill senescent cells, or figure out specific mechanisms by which to try to destroy them.

Your body makes a lot of junk, on the molecular level, and cells need to clean this up. Just increasing the expression of one protein that helps to clean up this junk was enough to make mice live ~17% longer. Cells recycle old proteins and other molecules into a big vesicle, called a lysosome. It contains many proteins, and their job is to chop up old cell parts that it engulfs. Genes for proteins that do work in the lysosome are mutated in diseases such as Parkinson's. So improving this process has immediate relevance to neurodegenerative disease. As the lysosome gets older, more junk builds up in it that it cannot degrade. Finding ways to make more lysosomes, or help lysosomes degrade junk, may be interesting therapeutic avenues to pursue.

You may have heard mitochondria referred to as the 'powerhouses' of the cell. One concept that comes up when people talk about mitochondria is 'oxidative stress' - the idea that if molecules are very reactive, they are likely to interfere with a lot of other molecules in the cell that should be left to their own devices. Weirdly, the story has turned on its head over time. It's true that it is bad to pump an animal full of reactive oxygen species, and that you can make a mouse live longer by increasing the level of proteins that are supposed to clean up mitochondria. But you can also mutate things that should be helping the mitochondria, and end up increasing lifespan! It's counterintuitive, and one hypothesis is that a little bit of stress is good because it forces your cells to put up their defenses and ramp up production of molecules that neuter the reactive oxygen species. But we don't really know.


Aging Research Half a Lifetime Ago: the Lost Decades of the 20th Century

We roughly know the recent history of longevity science, starting in the 1990s in a period in which the small scientific community interested in aging was defensive and self-policing, uninterested in any talk of treating aging as a medical condition. Young researchers were discouraged from thinking about intervention in the mechanisms of aging, or any hope of lengthening healthy human life span. Pushing that sort of viewpoint openly was career suicide. Established researchers in the field saw themselves as under siege by a tidal wave of pervasive and damaging nonsense generated by the anti-aging community of pills, potions, and outright lies, harming the prospects for building publicly funded research institutions to tackle specific age-related conditions, such as Alzheimer's disease.

Then came the work showing that single gene mutations could lengthen life in short-lived species. A rediscovery of the plasticity of longevity in response to environmental stress in worms, flies, and mice progressed from there onward. In particular there was ever greater interest and funding for calorie restriction research, mining the biochemistry of the mammalian response to low calorie intake, a part of the field put away and largely lost since the 1930s. Then the SENS rejuvenation research movement emerged just after 2000, and the thaw of a frozen research community started in earnest. Nothing proceeds rapidly in the sciences, even cultural change, and it was the late 2000s by the time that younger researchers could comfortably talk in public and publish papers about treating aging as a medical condition without career consequences. Nonetheless, that came to pass, and matters sped forward from there. Today, senolytic therapies capable of clearing senescent cells, one of the causes of aging, are under commercial development, and there is considerable excitement in the research community for this mode of intervention in the aging process. The thaw has completed, and the research community now confidently holds its own, unafraid of the anti-aging marketplace - which is just as full of nonsense and lies as it was thirty years ago.

What happened between the 1930s and the 1990s, however? Why was calorie restriction research abandoned? How did the understanding of aging progress over the 20th century? Looking back at history, we see so much of the past interest in aging and longevity as brief flashes, a few individuals undertaking it as a part of their broader research interests. Little in the way of a coherent whole emerges until our time; it is a collection of individuals, not a community. It is hard to understand the culture of the time from these few points of reference, the degree to which intervention in aging was or was not on the table as a point of interest for any particular group. Even the science fiction of the mid-20th century, usually illuminating as to the edges of scientific consideration, is unhelpful on this topic. The only assembled historical resource that I know of is Ilia Stambler's "A History of Life-Extensionism In The Twentieth Century", which actually provides much more information on a number of individuals who were at their peak of interest on the topic of aging in the late 1800s, versus what was going on between 1930 and 1950.

We can look back at a series of individual inquiries into aging across the span of very rapid technological progress in the decades to either side of 1900, leading up to, for example, the studies showing calorie restriction to slow aging and prolong healthy life in rats carried out in the 1930s. It all seems a logical progression of understanding and growth, leading somewhere. Yet after this, within the scientific community, it appears that the study of aging became ever more disconnected from practical thoughts of extending life. The closer researchers came to understanding the causes of aging, the more distanced they were from considering intervention in any organized way - the field turned to the treatment of age-related conditions, drawing an entirely artificial dividing line between aging and disease. I have no grasp on why this came to pass, at least in the first decades following the 1930s; after that, however, it is possible to draw connections and conclusions.

With the exception of the early establishment of amyloid aggregation by Alois Alzheimer, the causes of aging outlined in the SENS rejuvenation research proposals were all discovered, and those discoveries refined, in the thirty years between 1955 and 1985. The period between the 1960s and 1990s also encompasses the growth and success of the anti-aging marketplace outside the scientific community, probably spurred by the early scientific discoveries, but taking on a life of its own as people realized just how much profit could be made in this modern and more sophisticated incarnation of the old hoaxes regarding elixirs of life. For every group that approached anti-aging seriously, another ten were cheerfully selling nostrums and misrepresenting scientific discoveries - a trend that continues today.

Life extension was one of the tenets of the 1960s and 1970s culture propagated by people such as Timothy Leary, who wrote optimistically about scientific methods to dramatically extend human life span. There are probably people in the audience old enough and Californian enough to recall SMI2LE - Space Migration, Intelligence Increase, and Life Extension. The Age of Aquarius had its technological counterpart - now an overly optimistic retrofuture, only portions of which were attainable in the time span envisaged. But this movement was in no way a part of the small scientific community that studied aging, and the members of that research community rejected all of it, baby along with bathwater.

Thus to a very crude approximation, aging research in the latter half of the 20th century looks to have been steered by competing dynamics of commercially co-opted popular enthusiasm versus ivory tower rejection of that enthusiasm as a threat. There were never large numbers of thought leaders involved on either side, and the sums of money involved were never truly enormous, but this all happened in a period of growth and foundation and potential on either side of the fence. Could it have been different, and come to a better outcome for longevity science? Were those decades lost in terms of progress that could have occurred towards working healthy life extension technologies?

Everything boils down to economics in the end. It is reasonable to consider that progress only picked up in the frozen scientific community of the early 1990s because biotechnology had improved rapidly following the start of the computing revolution. Falling costs and greater capacity to generate results per unit expenditure mean fewer people must be asked for permission to perform any particular study. More exploration takes place by those with heretical views and useful curiosity. Nonetheless, we can imagine a very different world, one in which the institutional space race of the 1950s and on was instead a focus on biotechnology and aging. How much further might we be today, given massive investment on that front? It is hard to say. Could something like the Human Genome Project, for example, have been conducted at any price in the 1970s? Or any analogous feat of understanding? Drug discovery and cellular assessment were painfully slow and expensive processes back then; would it have been possible to uncover senolytic pharmaceuticals with any reliability?

But that is the root of any answer to the question of the degree to which the latter half of the 20th century was a series of lost decades in the matter of aging. We know that the scientific community retreated from engagement with the goal of extending human life, leaving that to the anti-aging marketplace, a community that did little of any great use for human longevity considering all of the effort expended, and generated much in the way of fraud, lies, and mistaken expectations along the way. A generation passed before the opportunity arose to change that state of affairs, but it is quite possible that the practical outcome might not have been all that different had it happened otherwise.

Excess Fat Tissue Leaves Lasting Damage to Stem Cells, Even if Lost

There is a fair amount of evidence from epidemiological studies to suggest that carrying excess visceral fat tissue will cause lasting damage to bodily systems even after that fat is lost. The longer it is there, and the more it there was, the worse off you are. You might recall a study that found lifetime maximum weight to be a better predictor of later age-related mortality than other measures, for example, implying that some forms of consequence linger even if the weight is lost. The study here identifies one possible mechanism to explain this sort of outcome; the authors find a lasting impact on the stem cell populations responsible for generating the cells of the immune system and other parts of the blood supply.

Obesity continues to weigh on the blood-forming stem cell compartment, altering the balance of the cell types produced there, even after the body sheds excess weight. Under the stress of obesity, hematopoietic stem cells (HSCs) begin to overexpress a regulatory gene that tilts blood production toward myeloid cells, and may even promote preleukemic fates. This shift in gene expression, which worsens over time, results in lasting dysregulation, even if HSCs are transplanted into a normal environment.

Although these findings come from a study that relied on a mouse model of obesity, they raise questions about the use of HSCs isolated from obese people in therapeutic transplant procedures. "Little is known about how obesity in marrow donors could affect the quality of the hematopoietic stem cell compartment. We want to better understand the molecular alterations in obesity to predict potential risks associated with the therapeutic use of stem cells isolated from obese donors."

The research team traced the dysregulation of the HSC compartment to altered expression of Gfi1, a transcription factor. "Mechanistically, we establish that the oxidative stress induced by obesity dysregulates the expression of the transcription factor Gfi1 and that increased Gfi1 expression is required for the abnormal HSC function induced by obesity. These results demonstrate that obesity produces durable changes in HSC function and phenotype and that elevation of Gfi1 expression in response to the oxidative environment is a key driver of the altered HSC properties observed in obesity."

Although the effects of chronic organismal stresses are still poorly understood, research is showing that age and environmental stresses can lessen the healthy diversity of cells in our blood-making machinery. "There is now an understanding that the blood stem cell compartment is made up of numerous cell subsets, Keeping this compartment healthy is essential to human health. This includes maintaining the diverse pool of blood-making stem cells needed to produce blood cells the body needs to function properly."


ALZFORUM Looks Back at 2017 in Alzheimer's Research

ALZFORUM should be on your reading list if you have more than a passing interest in research into neurodegenerative conditions. It is a great example of what can be achieved in educational advocacy if any earnest institutional funding is devoted to the task. That investment in advocacy exists today because Alzheimer's disease research is by far the largest portion of the broader aging research community, measured by funding and volume of projects, and has been for some time. The situation is quite different for our area of interest, rejuvenation research to repair the causes of aging. Here, the scientific programs of our community are still bootstrapping towards success in the absence of any larger-scale institutional funding, powered almost entirely by philanthropy. There really is no comparison when it comes to funding infrastructure. Still, ALZFORUM turns out a quality of online advocacy and education that we can aspire to - and given the continued unremitting failure in clinical trials of potential Alzheimer's therapies, it has to be said that just having funding doesn't automatically make advocacy an easy goal.

Confronting failure in trying to stem symptomatic Alzheimer's disease (AD), the field's main thrust has turned toward retooling its drug trials for ever-earlier disease stages. To sustain enthusiasm among participants and sites, scientists were advised to focus on learning from failure rather than conveying a sense of nihilism, both in internal discussions and in speaking with reporters.

They got to practice a positive attitude when another setback hit home. Merck announced an end to the EPOCH mild to moderate AD trial of the BACE inhibitor verubecestat for lack of efficacy, and data released later indicated that the drug had nudged down amyloid plaques without a hint of benefit, even in the more mildly symptomatic participants. Even so, BACE inhibitors are very much alive and being evaluated to a collective tune of billions of dollars. Researchers believe EPOCH treated people too late, when they'd had brain amyloid for years and neuron loss was well underway. The hope now rests on Phase 3 trials in people with mild AD. In trials of anti-amyloid antibodies, the place to go in 2017 was up. The A4 trial joined the trend in Alzheimer's immunotherapy when it quadrupled the solanezumab dose and extended treatment time to five years. Solanezumab had shown hints of efficacy in its negative Phase 3 trial, suggesting a higher dose might work.

Two different α-synuclein antibodies advanced to Phase 2. Researchers desperately want biomarkers for the next round of α-synuclein trials, and the race is on for PET tracers that will detect it. This work currently plays out on the Parkinson's disease (PD) front, but tracers and therapeutics for this protein will come in handy in Alzheimer's and dementia with Lewy bodies as well, as they will help scientists dissect the significant overlap of pathology and symptoms across the AD-PD spectrum.

Biomarkers will continue to be a research priority until they are solidly in place as routine features of AD diagnoses and trials, and 2017 saw strides toward that end. Researchers improved the standardization of cerebrospinal fluid (CSF) amyloid and tau measurement with automated CSF assays that vary less between runs and can predict clinical progression in cognitively normal people. Ultimately, clinicians prefer to use blood over CSF, and this year saw the first signs that this may be possible. Trialists all over the world seek a blood-based indicator of brain amyloid deposition to help them cut down on the number of expensive amyloid PET scans currently needed to recruit for secondary prevention trials.

Whatever doubt might have lingered out there about microglia's role in Alzheimer's was put to rest when scientists fingered a protective polymorphism near the gene for a major microglial transcription factor. Called PU.1, it controls myriad responses, including expression of known AD genes. This protective variant reduces PU.1 expression, lowers amyloidosis, and delays onset of AD. In a bizarre twist, 2017 ended on news that microglia not only help clear amyloid plaques, they may also help seed them. Some activated microglia spew protein bundles that power inflammatory cascades and also latch onto amyloid, driving plaque assembly.

The gradual sickening and eventual death of neurons defines neurodegenerative disease, but how exactly do disease-related proteins do this to neurons? A single theme did not emerge from this line of research in 2017; rather, it seems toxic proteins have an arsenal of weapons at their disposal. Tau appears to mess with all manner of cellular functions. Researchers implicated toxic tau variants in mitochondrial dysfunction, bungling synaptic vesicle release, disrupting the nucleus, compromising the epigenome. No one mechanism rose to the fore, however.

Vascular dementia research used to be a slow backwater relative to the flow of data every year on AD, but 2017 was different. Researchers made inroads into the physiology underlying this disease, for example by toppling a long-held dogma with their demonstration that the human brain does have a lymph system. The finding comes two years after a dural lymph system was discovered in mice. Continuing this year, the rodent studies reported that the dural lymph vessels drain cerebrospinal fluid from the brain into the blood stream. Besides the excitement about lymphatics, there was buzz about the regulation of blood flow in the brain. Researchers found that microinfarcts shut down local clearance of amyloid from the brain, at least in mice. These tiny, "silent" strokes are known to occur in people with AD, and the findings suggest they could hasten amyloid buildup by blocking clearance.


The Potential Influence of Gut Microbes on the Progression of Sarcopenia

Sarcopenia is the name given to the characteristic age-related loss of muscle mass and strength that affects every older adult, and eventually significantly contributes to outright frailty. For the past decade or more US researchers have been agitating to have sarcopenia officially defined as a medical condition, with no success yet. Indeed, this is a poster child for one of the ways in which the stifling effect of heavy regulation emerges in practice. For so long as the FDA doesn't consider sarcopenia a disease, then it becomes that much more challenging to raise funding for research and development of potential therapies; large commercial ventures won't consider it seriously, and in turn that lack of interest spreads back into earlier stages of research funding, for-profit and non-profit. The whole field slows down because someone's arbitrary boxes are not being checked.

There are many potential contributing causes to sarcopenia, all of which sound at least somewhat plausible and arrive accompanied by a fair amount of supporting evidence. Lower protein intake in older adults; defective processing of the amino acid leucine; sedentary behavior; chronic inflammation that disrupts the signaling and cell behavior needed for normal tissue maintenance; age-related decline in stem cell activity; infiltration of muscles by fat tissue; changes in mitochondrial dynamics that reduce energy output; blood vessel decline that reduces oxygenation; and loss of function neuromuscular junctions, to pick a few examples. The latest animal studies point firmly to stem cell decline as the primary cause, but there is a still quite a weight of research, collectively, for all of the other potential mechanisms. As in so many other areas of aging, the fastest path to assigning relative importance is probably to start fixing causes one by one and see what happens as a result.

In the paper noted here, researchers consider age-related changes in the gut microbiome as a way to make more sense of what has been reported of nutritional contributions to sarcopenia. In recent years the work of an increasing number of research groups has suggested that the bacteria of the gut are influential on natural variations in the pace of aging, perhaps to a degree that is in the same ballpark as exercise. Further, gut bacteria account for one portion of the many and varied mechanisms by which lowered calorie intake slows aging. The more compelling demonstrations are those in which transfer of gut bacteria from young to old animals extends life. Whether anything of significance to medicine arises from this is another matter entirely, however: consider how much time and effort has been spent on trying to reverse engineer exercise and calorie restriction, with little to show for it to date. The gut microbiome and its interaction with our biology is at least as complex, and possibly more so. The size of the potential benefits are just not that large in the grand scheme of things - perhaps a few additional years of life. There are better opportunities to chase with that same effort and funding, such as any of those in the SENS rejuvenation research portfolio.

Aging Gut Microbiota at the Cross-Road between Nutrition, Physical Frailty, and Sarcopenia: Is There a Gut-Muscle Axis?

Sarcopenia is a geriatric syndrome with a high prevalence in older individuals; its presence is estimated in up to 35% of hospital wards. Elderly individuals generally experience a decline of nutrient and energy intake with increasing age. This phenomenon is generally due to age-related loss of appetite, the so-called "anorexia of aging", whose physiopathology is only partly understood. It may also depend on increased energy requirements due to acute or chronic inflammation, leading to "disease-related malnutrition". Malnutrition and sarcopenia often overlap in older patients, so that one of the mainstays of sarcopenia prevention and treatment is promoting adequate nutrition. The prescription of adequate intakes of proteins, vitamin D, antioxidant nutrients, and long-chain polyunsaturated fatty acids has been particularly emphasized in this field, since these nutrients are able to counteract anabolic resistance, promote protein synthesis, and modulate inflammation, thereby preventing its detrimental consequences on muscle cells.

The human gut microbiota is composed of as much as 1014 bacteria, viruses, fungi, protozoa, and Archaea, with a gene pool 150 times larger than that of the host. It establishes a symbiotic relationship with the host, whereby individual environmental and genetic factors can shape its composition, while the host physiology is influenced and gets adapted to its presence. In healthy individuals, the gut microbiome generally includes between 1100 and 2000 bacterial taxa, most of which cannot be cultivated with traditional microbiological techniques.

Geographical location and diet are the major environmental factors explaining the interindividual differences in healthy gut microbiota composition. After the age of 65, gut microbiota resilience is generally reduced, so that its overall composition is more vulnerable to lifestyle changes, drug treatments such as antibiotics, and disease. As a result, species richness (i.e., the number of taxa that metagenomic analyses are able to identify) is reduced, and interindividual variability is enhanced. A lower number of species, decrease in the representation of taxa with purported health-promoting activity, and expansion of Anaerotruncus, Desulfovibrio, Coprobacillus and Gram-negative opportunistic pathogens are the most important changes that have been demonstrated in different clinical settings. These distinctive features of older persons' gut microbiome allow hypothesizing its involvement in the aging process with multiple mechanisms.

In a pioneering study on the ELDERMET cohort, it was demonstrated that the species richness of the fecal microbiota of older subjects is inversely related to physical performance. A secondary analysis of the same cohort has recently revealed that, in community dwellers, the presence of frailty, as measured through the Barthel Index (BI), is associated with a gut microbiome profile similar to that typical of nursing-home residents, with an increased representation of Anaerotruncus, Desulfovibrio, and Coprobacillus. These results are not merely speculative; they have important clinical correlates. For example, gut microbiota dysbiosis can be associated with a reduced survival in older individuals with frailty or disability. Moreover, the over-representation of opportunistic pathogens in the gut microbiota of frail multimorbid older patients may also increase the risk of developing infections.

However, these studies do not establish any cause-effect relationship between gut microbiota dysbiosis and physical frailty, due to their cross-sectional design. Several compounds produced or modified by the gut microbiota can enter systemic circulation and ultimately influence skeletal muscle cells. For example, a healthy gut microbiota is able to produce significant amounts of folate and vitamin B12, which may improve muscle anabolism. The most studied putative mediators of the effect of gut microbiota on skeletal muscle function are short chain fatty acids (SFCAs). These substances are generally derived from the bacterial metabolism of nutrients, such as proteins, which are introduced with diet. Their main host targets are skeletal muscle mitochondria.

The only intervention study carried out on older patients and targeted at exploring the effects of gut microbiota modifications on skeletal muscle outcomes involved the administration of prebiotics, i.e., substances promoting the overexpression of beneficial bacteria. In a randomized controlled trial, researchers enrolled 60 older patients who received treatment with a prebiotic formulation including fructooligosaccharides and inulin versus placebo for 13 weeks. Surprisingly, the treatment group experienced improvement in two outcomes of muscle function: exhaustion and handgrip strength. Thus, these data support the hypothesis of a modulation of muscle function by gut microbiota. Unfortunately, no other studies have explored this field to date.

The current state-of-the-art literature supports the hypothesis that gut microbiota may be involved in the onset and clinical course of sarcopenia. Since nutrition is one of the main determinants of gut microbiota composition, and is also involved in the pathogenesis of sarcopenia, the gut microbiota may be at the physiopathological cross-road between these two elements. Some key microbial taxa may have a relevant role in determining muscle structure and function by producing metabolic mediators that influence the host physiology after intestinal mucosa absorption. Glycine betaine, tryptophan, biliary acids, and SCFA, namely butyrate, are the most promising of these putative mediators.

Evolution Discards the Old

One way of looking at evolution is to see yourself, the individual, as little more than a disposable short-term delivery system. The focus of evolution is propagation of the germline, and aging exists in its present unpleasant form because in 99.9% of all complex species there is no selection benefit in avoiding it. On the one hand, nature is red in tooth and claw, and the only system that survives in the wild is one that gets the job of replication done before a violent or diseased death. On the other hand, systems optimized for early life tend to fall apart and consume themselves in later life. The mammalian adaptive immune system is a good example, a limited capacity system that will eventually malfunction due to encountering and attempting to remember too many different pathogens regardless of all of the other issues of aging. Evolution led to that system because it works well enough to get by in early life, and because there is little selection pressure to avoid the inevitable crash later in life, when the chances of reproductive success are low.

Lastly, there appears to be a race to the bottom between long-lived and short-lived species. The reason why we see so few species succeeding in their own niche via a long-lived strategy of agelessness and continual replication, as is the case for some species of hydra, may be that aging species can adapt more rapidly to changing environments. Thus highly regenerative, ageless species of various sorts may arise over and again in larger numbers during long periods of environmental stability - it is hard to say from the fossil record whether or not this is the case - but are out-competed and swept away by aging species when the climate or ecology shifts rapidly enough over evolutionary time.

Many people would tell you that death - or rather, aging - wasn't around until we started reproducing sexually. There's no reason sexual recombination in itself would demand our death, however. In fact it clearly doesn't: we know of two species of worm which reproduce by splitting themselves lengthwise and fusing together, who are nonetheless no likelier to die in old age than in youth. The famously immortal Hydra is also capable of reproducing sexually (although it usually chooses budding instead). On the flip side, there are multiple organisms who produce eggs asexually, but aren't any safer from senescence than we are.

The rather disturbing truth about life and death is that our bodies are just disposable vessels for the replicators cushioned safe and snug within our germ cells. While a few organisms like the Hydra kept things simple by remaining as one with their germline, others built free-standing bodies of somatic cells with ever more complex machinery to house and propagate a germline that was reincarnated each generation inside a new (and hopefully improved) body. The resulting collections of meat and bone eventually became complex enough to totally obscure the germline itself, and conducted lives with apparent independence - humans in particular enjoyed millennia of ignorance about our fundamental irrelevance. But despite its obscurity, the consequences of its influence could hardly escape notice, for one simple reason: once the germline had abandoned the body, we were all condemned to death.

Key to this fate was the fact that you would, at some point, probably die anyway. Maybe you'd starve in a famine, or be eaten by the resident apex predator, or just freeze to death. But whatever the cause, you were always less likely to live two years than to live one. In this way, each individual's reproductive potential was concentrated at the beginning of his life, and declined at some rate after sexual maturity. The most crucial task was getting you to reproductive age at all, and consequently a lot of selection power had to be spent on birth and development. By contrast, ages that organisms were rarely capable of reaching would experience extraordinarily little selective pressure, the bottom of a genetic slump that began very soon after reproductive maturity. The problem wasn't just that beneficial alleles in old age weren't selected for; it was that alleles with damaging effects later in life could curry favor by increasing fitness at the ages of highest reproductive potential - an effect known as "antagonistic pleiotropy".

Exactly how bad a deal you, the body, get is dependent on your niche. How dangerous is it? How long are you likely to survive? If you're a wild mouse, your chances are around 10% in the first year. There's no sense in spending a long time on growth and development, and you'd better have lots and lots of children, because most of them will die. On the opposite end of the spectrum are organisms that live in relative safety. They may live on an island with no predators, such as a particular strain of opossum with unusually long life, or have an unusually reliable food source. Humans, for our part, didn't come out as bad as we could have. We're among the longer-lived species, and there's a good chance that apparently unrelated medical advances in the last century have been pushing us in the direction of a slower intrinsic aging rate.


Mitochondrial Transfer Partially Reverses Some Consequences of Oocyte Aging

This is a most interesting technology demonstration for anyone interested in the various aspects of mitochondrial contributions to aging: transferring mitochondria from fat-derived cells into germline cells in an older mouse can reverse some of the consequences of aging in the germline, specifically loss of fertility in females. Mitochondria are the power plants of the cell, primarily responsible for generating chemical energy store molecules, though they have many other roles in fundamental cellular activities as well. There are a couple of different aspects to mitochondrial dysfunction in aging, and the research here is probably relevant to the one unconnected to SENS rejuvenation research: the general malaise that affects mitochondria throughout the body, probably a reaction to rising levels of other molecular damage, that changes mitochondrial dynamics and reduces available energy for cellular operations. The research results noted here raise many questions regarding the mechanisms involved in different rates of decline of mitochondrial function throughout the body.

The fertility of women decreases with maternal aging, resulting from various kinds of reasons including decreased follicle number, altered reproductive endocrinology, increased reproductive tract defects, decreased embryo quality, and impaired oocyte quality. Among the possibilities, decreased oocyte quality with maternal aging is the main reason because oocyte donation from young women could rescue the low live birth rate in elder women. With maternal aging, both the nuclear maturation and cytoplasmic quality are affected, and oocyte aneuploidy arising from chromosome segregation error increases dramatically. The obvious change in ooplasm with maternal aging is mitochondrial dysfunction.

It is well known that mitochondria function in energy production and apoptosis in cells. As the most prominent cell organelles in oocytes, mitochondria play pivotal functions and determine the developmental competence of oocytes. With advanced maternal age in women, the most common aberrations in mitochondrial structure are mitochondrial swelling and cristae disruption. Mitochondria are the main source of ATP through oxidative phosphorylation in mammalian oocytes. It is reported that reduced ATP content and metabolic level could be detected in aged oocytes, which would affect oocyte quality and embyogenesis. Mitochondrial malfunction is highly related with defects in spindle organization, cell cycle progress and chromosome segregation in oocytes of aged women and mice. Mitochondrial dysfunction is a major contributing factor for negative outcomes in IVF in general, especially in women of advanced maternal age. The findings reminded the researchers that mitochondria supplement or replacement in oocytes might be a possible strategy for infertility treatment in elder women.

The mitochondria replacement by transfer of heterologous ooplasm, germinal vesicle, spindle, polar body, or pronuclei has been tested in animals and humans to improve developmental potential of aged defective oocytes or to prevent trans-generational mitochondrial disease transmission, but clinical translation of these techniques requires further validation for their efficacy and safety. Especially, the compatibility between donor and recipient mitochondrial DNA and mitochondrial heteroplasmy are still a concern. Transfer of autologous mitochondria from cumulus and granulosa cells were tested for oocyte quality rescue, but it is worth noting that cumulus and granulosa cells age similarly to oocytes. We supposed that autologous adipose tissue-derived stem cell (ADSCs) might be an ideal mitochondrial source for rescuing oocyte quality and fertility. In our study, we found that supplement of autologous ADSC mitochondria could improve oocyte quality, embryogenesis, and fertility in aged mice. We propose that autologous ADSC mitochondria supplement may be a promising strategy for fertility retrieval in women with advanced reproductive age.