The Cosmological Noocene

Here is a sketch of the future, without any specific dates assigned to its milestones. The molecular biochemistry of living beings is fully mapped and understood. The human mind is reverse engineered. It is run in software. A million variants and improvements are constructed. Molecular nanotechnology is established and becomes a mature industry, available to everyone. Anything and everything can be built efficiently and at next to zero cost given the raw materials and a specification. All disease is abolished, and aging is defeated: these are problems that boil down to control over molecules, just another form of maintaining a machine to remove wear. The future stretches out indefinitely for all living entities, whether biological or otherwise. Given that, is perhaps never too early for at least a little long-term thinking, even though we're still here in the present, working away at the very first rung of this tall ladder to the future.

From an economic perspective those who thrive in the era of molecular manufacturing and comprehension of mind are those who make the most efficient use of the matter that they own, and those who gain control over the most matter: quality versus quantity shift back and forth in the degree of advantage as the ability to accurately and rapidly manipulate large masses of matter at the atomic level and lower grows. Matter is most economically efficient when incorporated as the workings of an intelligent entity. The end state here is a continuum of thinking matter, and there are countless arrangements by which matter might be made aware. Our evolved biology is among the least intricate and least capable of these possibilities. At the most efficient we might envisage space- and matter-efficient computational processors plus the necessary workings for support: communication, energy, repair, and so forth. The higher the fraction of that mix that can be devoted to data processing and transfer, the more economically effective the entities who use that system as a substrate.

Evolved intelligences are not rational actors in search of growth above all other goals. We have parks and entertainment industries, for example. There is no reason why constructed or augmented intelligences should be any different, but equally they have one important quality: they can change themselves and their progeny in defined ways to achieve defined outcomes in mental state. The alterations and experiments that provide economic advantages will prosper. Entities who choose to incorporate an urge to growth will become the majority. At some point the value of an asteroid, a moon, a planetary crust, or a star in its natural state falls below the value of the same matter dismantled and used as raw materials for computational processing. After that it is just a matter of time before this solar system, a wilderness at present, and a collection of parks in ages ahead, is transitioned into a more efficient arrangement of matter in which near every portion of the whole is intelligent. This change will propagate outward to other stellar systems, without end, driven by simple economic considerations. A sea of cultures of a complexity and scope beyond our imaginings, and our world today the tiniest mote of a seed, that could be emulated by the smallest discrete material unit of computational processing in that future substrate.

So it is less a matter of manifest destiny that we will convert our entire future light cone into intelligence, and more a matter of economic inevitability, the destination at the end of the random walk of choice simply because some classes of choice will be made more frequently than others. The outcome of human action writ large, for a very expansive definition of the word human. All of this, however, indicates that there is something very important that we at present do not understand about the nature of reality. Nothing in our present situation as a species appears to be exceptional: stars are everywhere in vast numbers, planets also, and complex organic molecules are seen wherever we have the ability to observe them. Thus intelligence should arise elsewhere. The age of the universe is very long in comparison to the time taken for our spontaneous generation, yet we see no evidence that any other intelligence has come before us. This is often expressed as the Fermi Paradox, but is perhaps best thought of as the Wilderness Paradox, which is to ask why everything we observe, out to the very limits of the visible universe, is apparently natural and unaltered. Where are the signs of what we know is possible and inevitable for an intelligent evolved species, the conversion of matter to more efficient forms on a vast scale?

The only self-consistent solution to the Fermi Paradox that does not require some new and presently missing piece of scientific understanding is the Simulation Argument: that we are in a box and walled off from the real world, whatever that might be, created by some demiurge for purposes guessable but ultimately unknowable through any action on our part. Prosaically that demiurge might be a descendant of a past humanity similar to ours, an entity that is running one of countless ancestor simulations for scientific reasons. Far less prosaic options are also possible, in which the demiurge is simulating from first principles a radically different cosmology from its own and thus its nature and motivations are inscrutable. These possibilities of the Simulation Argument are dissatisfying to explore, however, for all the same reasons as the brain in a jar thought experiment is a dead end. Best to assume it is not true, as it if is there is nothing useful you can do about it, individually or collectively. It is Pascal's Wager turned inside-out.

It is more interesting to speculate on what it is that we don't understand at present about the nature of reality. There are numerous candidates, and most present thinking is directed towards those related to enforcing our rarity, often expressed as the Great Filter, one or more enormously unlikely steps that lie between the origin of a barren world scattered with a few organic compounds and the destination of an intelligent species engaged in repurposing of raw materials on a vast scale. All proposed Great Filters are very speculative; there is a great deal of room to argue about odds when you only have one example to work with, or events of the distant past must be reconstructed from theory, or future development of the species considered in detail rather than at a very high level, all which makes coming to any sort of rigorous conclusion next to impossible. All that is practical to achieve is to build the shape of the argument that would be sufficient if the actual numbers and proposed events in fact exist in reality. Given this uncertainty, any proposed Great Filter becomes an ever less satisfying answer the further we look outward and the more galaxies we see without any sign of massive engineering. It only serves to argue for our uniqueness, which is implausible given what we presently know and the isotropic nature of all other observed aspects of the natural universe across vast spans of distance and time.

Per our present understanding of physics and intelligent economic activity, we will turn every part of that great span, stars and all, into our descendants if not diverted or stopped by some outside influence. The cosmological noocene, an ocean of intelligence of breathtaking scope and grandeur. That the natural universe remains as it is to be used by us indicates that something is awry, however, that some vital and important understanding is missing. We as a species are still in the act of making the first fumbling explorations of the bounds of the possible with regards to what it is that we don't know.

Mitochondrial Oxidative Stress in Neurodegenerative Disease

Aging is characterized by increasing dysfunction in mitochondria, the power plants of the cell, responsible for packaging chemical energy store molecules, ATP, to power cellular operations. Mitochondrial decline in aging is most studied in energy hungry tissues such as the muscles and brain, and it is widely accepted that mitochondrial dysfunction is an important feature of neurodegenerative diseases. Mitochondrial dysfunction is likely caused by damage to mitochondrial DNA and loss of quality control mechanisms responsible for destroying malfunctioning mitochondria. It manifests as a reduced supply of ATP and increased generation of oxidative molecules.

Oxidative reactions that disrupt cellular machinery occur constantly even in youth, and cells possess many antioxidant and repair mechanisms to keep this damage under control. Oxidative damage is even used as necessary signaling in processes such as the beneficial response to exercise. Consistently raised amounts of oxidative molecules are harmful in many ways, however, not just damaging internal cellular operations, but also producing downstream issues such as altered forms of cholesterol that contribute to the progression of atherosclerosis.

Aging is the primary risk factor for a number of human diseases, as well as neurodegenerative disorders. A growing body of evidence highlights bioenergetic impairments as well as alterations in the reduction-oxidation (redox) homeostasis in the brain with the increasing of the age. The brain is composed by highly differentiated cells that populate different anatomical regions and requires about 20% of body basal oxygen for its functions. Thus, it is not surprising that alterations in brain energy metabolisms lead to neurodegeneration.

Cellular energy is mainly produced via oxidative phosphorylation taking place within mitochondria, which are crucial organelles for numerous cellular processes, such as energy metabolism, calcium homeostasis, lipid biosynthesis, and apoptosis. Glucose oxidation is the most relevant source of energy in the brain, because of its high rate of ATP generation needed to maintain neuronal energy demands. Thus, neurons rely almost exclusively on the mitochondria, which produce the energy required for most of the cellular processes, including synaptic plasticity and neurotransmitter synthesis.

Reactive oxygen species (ROS) are normally produced in the cell of living organisms as a result of normal cellular metabolism and are fundamental in the maintenance of cellular homeostasis. When an imbalance between ROS production and detoxification occurs, ROS production may overwhelm antioxidant defenses, leading to the generation of a noxious condition called oxidative stress and overall to the impairment of the cellular functions. This phenomenon is observed in many pathological cases involving mitochondrial dysfunction, as well as in aging. The brain is particularly vulnerable to oxidative stress and damage, because of its high oxygen consumption, low antioxidants defenses, and high content of polyunsaturated fats very prone to be oxidized.

Mitochondrial dysfunction is one of the main features of the aging process, particularly in organs requiring a high-energy source such as the heart, muscles, brain, or liver. Although a large amount of data support the role of mitochondrial ROS production in aging, it has also recently been demonstrated the involvement of the mitochondrial permeability transition in the mechanisms of aging. The age-associated decrease in mitochondrial membrane potential correlated with reduced ATP synthesis in tissues of old animals. The mitochondrial permeability transition is due to a nonspecific pore called the mitochondrial permeability transition pore (mPTP) occurring when mitochondria become overloaded with calcium. Indeed, it is well known that aging alters cytosolic calcium pick-up and the sensitivity of the mPTP to calcium enhanced under oxidative stress conditions.

Neurons are postmitotic highly differentiated cells with a lifespan similar to that of the whole organism. These excitable cells are more sensitive to the accumulation of oxidative damages compared to dividing cells and are more prone to accumulating defective mitochondria during aging. Thus, it is not surprising the importance of protecting systems, including antioxidant defenses, to maintain neuronal integrity and survival. All the neurodegenerative disorders share several common features, such as the accumulation of abnormally aggregated proteins and the involvement of oxidative damage and mitochondrial dysfunction. Many of the genes associated with Parkinson's disease or ALS are linked to mitochondria. In addition, all aggregated misfolded proteins (β-amyloid, tau, and α-synuclein) are known to inhibit mitochondrial function and induce oxidative stress. Therefore, the identification of common mechanisms underlying neurodegenerative diseases, including mitochondrial dysfunction, will increase our understanding of the essential requirements for neuronal survival that can inform future neuroprotective therapies.


Higher Protein Intake Correlates with Lower Risk of Frailty in Old Age

Physical weakness is a sizable component of age-related frailty. The loss of muscle mass and strength that accompanies aging, known as sarcopenia, has many potential contributing causes, with varying degrees of accompanying evidence. One of these is dietary, a lower protein intake in older individuals, and dysfunction in processing of amino acids such as leucine. That this correlates with frailty, as illustrated here, doesn't necessarily mean that it is an important cause, however. The alternative is that the factors that lead to reduced dietary intake in later life are distinct issues that arise from similar root causes to those of sarcopenia: consider something as simple as increased difficulty when swallowing, for example. When it comes to mechanisms, there is better evidence for chronic inflammation produced by cellular senescence or declining stem cell function to be primary causes in sarcopenia, and these are not particularly related to dietary protein intake.

Frailty can be defined as a state of augmented sensitivity and vulnerability to external stressors in old age. The Fried frailty phenotype classifies frailty as the presence of three or more of the following five components: weakness, slowness, low physical activity, exhaustion, and weight loss, and prefrailty as the presence of one or two of the Fried phenotype criteria. In a recent systematic review carried out in 61,500 individuals aged 65 and older, the overall prevalence of frailty was estimated to be 10.7%, and 41.6% were prefrail with one or two components of Fried frailty phenotype.

There is growing support for the concept that greater protein intake may preserve physical function in older adults. The anabolic response to amino acid intake may be blunted in older people, particularly if they have low intakes of protein. In addition, animal protein intake may be associated with muscle strength in older adults, which may be associated with a lower risk of frailty; whereas, plant-based protein sources may have limited potential to stimulate the skeletal muscle anabolic response. The exact reasons are not understood but it might be that plant proteins are considered to have a lower content of essential amino acids compared to animal protein sources. Nevertheless, knowledge regarding the association between adequate protein intakes, according to recommendations, and sources of protein intake with frailty are limited.

We hypothesized that the prevalence of frailty and prefrailty was lower among older women consuming ≥ 1.1 protein/kg body weight (BW) compared to those with lower intakes. Participants were 440 women aged 65─72 years enrolled in the Osteoporosis Risk Factor and Prevention-Fracture Prevention Study. Protein intake g/kg BW and g/d was calculated using a 3-day food record at baseline. At the 3-year follow-up, frailty phenotype was defined as the presence of three or more, and prefrailty as the presence of one or two, of the Fried criteria. At the 3-year follow-up, 36 women were frail and 206 women were prefrail. Higher protein intake ≥ 1.1 g/kg BW was associated with a lower likelihood of prefrailty (odds ratio = 0.45) and frailty (odds ratio = 0.09) when compared to protein intake of less than 1.1 g/kg BW at the 3-year follow-up. Women in the higher tertile of animal protein intake, but not plant protein, had a lower prevalence of frailty. Thus protein intake ≥ 1.1 g/kg BW and higher intake of animal protein may be beneficial to prevent the onset of frailty in older women.


Rejuvenation Biotechnology Companies Presenting at Biotech Investing in Longevity, in San Francisco May 2019

Aikora Health and Foresight Institute recently collaborated to host a gathering of investors, entrepreneurs, and supporters from the core rejuvenation biotechnology community. The event was held in San Francisco, and I attended to present a summary of ongoing work at Repair Biotechnologies. It was an interesting mix of local folk and visitors from across the US, a chance to catch up with fellow travelers from other companies and some of our investors. As you probably know, the SENS Research Foundation and a number of influential aging research institutions, such as the Buck Institute, are based in the Bay Area. It has long been the case that the venture and technology communities in California include many people sympathetic to the SENS goal of bringing aging under medical control - it isn't a coincidence that the SENS Research Foundation set up their research center in this part of the world.

The presentations were recorded, and in the video here see my outline in addition to those by principals at the Methuselah Fund, Leucadia Therapeutics, and As you might recall, Repair Biotechnologies is working on reversal of atherosclerotic lesions, aiming to prevent the contribution of this condition to late life mortality, and regrowth of the thymus, so as to restore the pace of creation of T cells, and improve immune function in later life. We recently raised our seed round, so we're hard at work in the lab at the moment.

The other two biotech companies are working on very interesting projects, and I've mentioned both in the past here at Fight Aging! In the case of Leucadia, you might look at the presentation given by Doug Ethell at Undoing Aging 2018 for a good overview of the company and its approach. It is exactly the sort of radically different, cost-effective approach to Alzheimer's disease that we'd like to see more of. is equally radical in the goal of a href="">transiently reprogramming cells in vivo, spurring them into the improvements observed in the reprogramming of somatic cells into induced pluripotent cells: repair of mitochondrial function, possibly repair of other molecular damage, and reversion of epigenetic markers of aging. There should be more of this sort of ambition in evidence in the biotechnology community.

Methuselah Fund, Leucadia Therapeutics, Turn Biotechnologies and Repair Biotechnologies

Four presentations at "Biotech Investing in Longevity" on 1st May 2019 in San Francisco: Sergio Ruiz - Methuselah Fund; Doug Ethell - Leucadia Therapeutics; Vittorio Sebastiano - Turn Bio; Reason - Repair Biotechnologies.

The Methuselah Fund is designed to accelerate results in the longevity field, extending the healthy human lifespan. They measure their success not just by financial return-on-investments but also by what they call return-on-mission. Their DNA stems from The Methuselah Foundation, which has been working hard during the last 18 years to make 90 the new 50 by 2030.

Leucadia Therapeutics is determined to end Alzheimer's disease with Arethusta, a first-in-class treatment for mild cognitive impairment associated with Alzheimer's disease. Cerebrospinal fluid (CSF) clears toxic metabolites from intercellular spaces in the brain, much as the lymphatic system does in the rest of the body. The first regions of the brain to be impacted by Alzheimer's disease are cleared by CSF that drains across a porous bone called the cribriform plate. Aging and life events can occlude the cribriform plate and reduce the CSF-mediated clearance of toxic metabolites from those regions of the brain, thereby causing plaques and tangles formation. Leucadia's patented Arethusta technology restores CSF flow across the cribriform plate, improving the clearance of toxic metabolites from the earliest regions of the brain to be affected by Alzheimer's disease. develops a transient reprogramming protocol that has demonstrated a youthful reversion of eight of the nine hallmarks of aging. Reversion of the ninth is being currently being developed. They technology has already been proven to rejuvenate five different tissue types of the human body with more being evaluated. Osteoarthritis, skin damage, and sarcopenia are all proven targets of the technology, with other indications soon to be tested.

Repair Biotechnologies is a longevity company with the mission to develop and bring to the clinic therapies that significantly improve human healthspan through targeting the causes of age-related diseases and aging itself. The company currently runs two preclinical development programs: the first for thymus regeneration and immune system restoration, and the second for reversal of atherosclerosis.

Aikora Health and Foresight Institute joined forces to organize a series of talks on biotech investment and longevity. They gathered a curated group of entrepreneurs, scientists, and investors to discuss exciting projects that seek to extend human healthspan, surveying a diversity of novel approaches, and discussing which ambitious goals are realistically within our reach.

Aikora Health connect investors with companies, founders and scientists in the health tech, genomics, and regenerative medicine sectors. Our key focus is on longevity tech with the potential to transform healthcare and human aging. We offer insight and information regarding the biotech and increasingly important longevity space, in addition to matching founders of biotech and longevity companies with funding and strategic partnerships.

Foresight Institute is a leading think tank and public interest organization focused on emerging world-shaping technologies. It was founded in 1986 on a vision of coming revolutions in technology that will bring extraordinary opportunities, as well as unprecedented challenges. Foresight's mission is to steer towards positive futures, futures of Existential Hope.

A Discussion of Mitochondrial DNA Damage and Aging

Every cell in the body contains a swarm of mitochondria, responsible for packaging the chemical energy store molecule ATP that is used to power cellular processes. Mitochondria are the distant descendants of symbiotic bacteria, and retain a remnant of the original DNA. This mitochondrial DNA is unfortunately less well protected and maintained than DNA in the cell nucleus. It is thought that a sizable fraction of the declines of aging are caused by accumulated damage to mitochondrial DNA, coupled with progressive failure of the quality control mechanisms responsible for recycling dysfunctional mitochondria. Reducing the functional capacity of cells via a reduction in available energy can produce all sorts of detrimental effects, and while much of the relevant research is focused on the energy hungry tissues of brain and muscle, this is a problem in all tissues.

The mitochondrial organelle, a double-membraned organelle with its evolutionary origins in the eubacterial kingdom, is the central factor in the energy metabolism of the eukaryotic cell. It is responsible for the vast majority of the ATP (adenosine triphosphate) produced in the cell (~90% under normal circumstances), which it produces through oxidative phosphorylation (OXPHOS) by way of a multi-subunit complex called the electron transport chain (ETC). The mitochondrion possesses its own small, circular genome (mtDNA) that encodes key RNA and proteins required for OXPHOS.

The mtDNA mutation rate depends on many factors, including the extent of oxidative stress and the fidelity of the mitochondrial DNA polymerase (POLG). The production of reactive oxygen species (ROS) is an inevitable outcome of the oxidative phosphorylation process that occurs within the mitochondrion, and these chemical byproducts are, by their nature, damaging to DNA. Thus, given its proximity to the source of ROS production, mtDNA experiences a high rate of ROS-induced mutation. ROS production is also increased by pre-existing mtDNA damage, excess calories, regional mtDNA genetic variations, and alterations in nuclear DNA expression of stress response genes, creating a vicious cycle where increased ROS production can encourage the occurrence of even more ROS production over time.

There is a well-established correlation between aging and a decline in mitochondrial function, which likely contributes to age-related senescence and geriatric disease. PolgD257A "mutator" mice - which exhibit increased mtDNA mutation rates - show an accelerated aging phenotype, suggesting that the accumulation of mtDNA mutations over time may be a crucial factor driving the aging of mammals. The age-related decline in mitochondrial function is likely caused, in large part, by the gradual accumulation of somatic mtDNA mutations due to ROS damage and DNA replication errors. This accumulation of mtDNA mutations promotes even more ROS production, establishing a vicious cycle and accelerating the aging process. Although a serious mtDNA mutation can be acquired early in life, for most people it will take several decades to acquire one or more disease-causing mutations and have them reach a sufficiently high level of heteroplasmy to cause serious health issues. This gradual accumulation of mutations and increase in heteroplasmy may help explain the time-dependent decline in function that occurs with age.

Somatically-acquired mtDNA mutations can occur anywhere in mtDNA and may even include large deletions or duplications. Loss of mtDNA integrity (by altered mtDNA copy number or increased mutations) has been implicated in cellular dysfunction with aging. Deletion mutations are an insidious risk because the reduced size of mtDNA molecules carrying large deletions (ΔmtDNAs) gives them a replicative advantage over normal mtDNA.

Any mtDNA molecules containing a deleterious mutation in a coding gene, combined with a D-loop mutation that creates a strong proliferative advantage, would have the potential to create severe issues in old age, particularly if they cause the cell to take on neoplastic properties. Furthermore, this ubiquitous and steadily accumulating mutational load in the mtDNA population will likely create general problems for the ETC function and mitochondrial health, thus contributing to age-related senescence. For these reasons, we believe there is great merit in the argument that mitochondrial defects play a significant role in the development of many common diseases of age. We hypothesize that the diversity of mutations in mtDNA could be decisive for the variability of clinical phenotypes, such as age of disease onset.


Temporary β-catenin Inhibition Attenuates Effects of Aging on Bone Regeneration

For all that it reports a success, the open access paper here is an excellent example of the prevalent, inferior approach to the development of therapies for age-related conditions. Instead of looking for causes of the problem in question, the slow and dysfunction regeneration of bone fractures in older individuals, the scientists find a way to tinker with the dysfunctional state of aged metabolism, overriding one of the detrimental regulatory changes to some degree. As a strategy this will always be far less effective than tackling the underlying root causes of age-related dysfunction: trying to tinker a damaged engine into continued operation without fixing the damage is always going to be a challenging task. Nonetheless, this strategy remains much more popular in the research community, more is the pity.

Almost a third of humans will fracture a bone, and most often these injuries go on to successfully heal. However, various environmental and biological factors can hinder this regenerative process. With age, the pace of fracture repair slows, and the risk of non-union increases. This slower pace of repair in older individuals is responsible for increased morbidity and even mortality.

While there are many factors that could impair fracture healing with aging, the pace of fracture repair can be rejuvenated by circulating factors present in young animals. Recent data suggests that factors produced by young macrophage cells pay a critical role in the rejuvenation process. While these factors regulate the pace of repair, their effects on mesenchymal cells differentiating to osteoblasts are mediated by signaling pathways such as β-catenin.

β-catenin signaling plays different roles in mesenchymal differentiation at different repair stages. In the initial phase of repair, the level of β-catenin needs to be precisely regulated as levels that are too high or too low will prevent undifferentiated mesenchymal cells from becoming osteochondral progenitors and will inhibit fracture healing. Once the cells differentiate to osteochondral progenitors, higher levels of β-catenin stimulate osteogenesis and enhance fracture repair.

Here we examined the ability of pharmacologic agents that target β-catenin to improve the quality of fracture repair in old mice. 20 month old mice were treated with Nefopam or the tankyrase inhibitor XAV939 after a tibia fracture. Fractures were examined 21 days later by micro-CT and histology, and 28 days later using mechanical testing. Daily treatment with Nefopam for three or seven days but not ten days improved the amount of bone present at the fracture site, inhibited β-catenin protein level, and increased colony forming units osteoblastic from bone marrow cells. This data supports the notion that high levels of β-catenin in the early phase of fracture healing in old animals slows osteogenesis, and suggests a pharmacologic approach that targets β-catenin to improve fracture repair in the elderly.


Evidence for Senescent Cells to Cause Aortic Aneurysms

Cells enter a senescent state in response to molecular damage, a toxic environment, reaching the Hayflick limit on replication, or to aid in wound healing, among other reasons. A senescent cell halts replication and begins to secrete a mix of inflammatory signals, growth factors, and other molecules that influence surrounding cells. This is useful and beneficial when it occurs in potentially cancerous, damaged cells, or as a part of the wound healing process. Normally these cells quickly self-destruct or are destroyed by the immune system. It is when senescent cells evade destruction and linger for the long term that the problems begin. The signals that are beneficial in the short term become destructive to tissue function and structure, additionally producing chronic inflammation and all of its accompanying problems.

In recent years, the research community has finally adopted the SENS Research Foundation view of aging in the matter of senescent cells - fifteen years late to the party, but better late than never. Meaningful progress requires more scientists and sources of funding to be involved than was the case a decade ago, so it is good that this is happening. Researchers have now demonstrated that growing numbers of senescent cells contribute to a wide range of age-related conditions, and are likely the primary cause for some of them, such as arthritis. In animal studies, selectively destroying a sizable fraction of senescent cells can extend healthy life spans, and reverse the progression of age-related diseases. Senescent cells are in effect actively maintaining a disrupted, dysfunctional state of tissue function and metabolism. Removing them turns back these consequences, producing a narrow form of rejuvenation. Aging is itself an accumulation of damage, and these senescent cells are a form of damage.

The evidence for cellular senescence to be a significant contributing cause of specific age-related conditions continues to accumulate, and ever faster as more funding pours into this part of the field. The research results noted here are an example of the type, new discoveries in the relevance of senescence to age-related disease that are announced every few months. The more that is discovered, the better for all of our futures, given that work continues on ever better ways to remove senescent cells from old tissues. That the catastrophic thinning and structural failure of aorta walls involves senescent cells is one more potential benefit to be realized by senolytic therapies capable of clearing senescent cells.

Scientists find potential way to defuse 'time bomb' of cardiology

Ascending aortic aneurysms grow for decades without any warning signs and can be fatal once they rupture. It is known that these aneurysms are caused by the thinning of the aortic wall which weakens it and makes it silently grow like a balloon over time without any symptoms. If caught early enough, they can be surgically repaired at low risk, but if they go undetected, which many do, they will eventually rupture or cause a tear in the wall of the aorta, called an aortic dissection. While the phenomenon is well documented, the medical community previously had little evidence to understand the mechanisms causing it to occur or how to prevent it.

Now, researchers have shown that a process that is recognized in cancer biology is causing the cells to become destructive and eat away at the surrounding muscle tissue, weakening the aortic wall. "We discovered that within the wall of the aorta, a small proportion of the muscle cells have entered into a state called senescence. Rather than die, these senescent cells become destructive, secreting enzymes that chew the area around them. There are select research groups around the world that are coming up with compounds that have shown promise in clearing out senescent cells. They are thinking about it for certain aging-related diseases, but it could be positioned for this important problem as well."

Seno-destructive smooth muscle cells in the ascending aorta of patients with bicuspid aortic valve disease

We undertook in situ analysis of ascending aortas from 68 patients, seeking potentially damaging cellular senescence cascades. Aortas were assessed for senescence-associated-ß-galactosidase activity, p16Ink4a, and p21 expression, and double-strand DNA breaks. The senescence-associated secretory phenotype (SASP) of cultured-aged bicuspid aortic valve (BAV) aortic smooth muscle cells (SMCs) was evaluated by transcript profiling and consequences probed by combined immunofluorescence and circular polarization microscopy. The contribution of p38 MAPK signaling was assessed by immunostaining and blocking strategies.

Herein, we report that senescent SMCs accumulate in aneurysmal ascending aortas associated with bicuspid and tricuspid aortic valves. Moreover, we identified a particular predisposition to SMC senescence in BAV aortopathy, indicated by the presence of senescent SMCs in non-aneurysmal BAV aortas, enrichment of cellular senescence at the aortic convexity, and multivariable analysis of potential aneurysm risk factors. We further show that senescent aortic SMCs have a pronounced collagenolytic SASP, a destructive profile that is controlled by p38 MAPK. The findings identify a cellular aging cascade in human BAV disease and a "seno-destructive" SMC phenotype that may underlie the aortic wall degeneration.

A Better Understanding of the Mechanisms Surrounding Thymic Involution

Researchers here report on their exploration of the protein interactions involved in the loss of active thymic tissue with age, a process called thymic involution. Since the thymus is where T cells mature, this loss contributes to the age-related decline of the adaptive immune system. Historically, this sort of investigation has focused on FOXN1 as the master regulator of thymic growth and activity. Upstream of FOXN1 is BMP4, however, and the paper here discusses the ways in which BMP4 is dysregulated with age. This discussion should probably be read in the context of other work that strongly suggests chronic inflammation is the driver of changes leading to thymic involution. Nothing happens in isolation in aging tissues, and there are usually deeper causes to be considered.

Thymic epithelial cells (TECs) are essential for the establishment of the specialized microenvironment that orchestrates the development of naive, self-tolerant T cells from hematopoietic precursors. They are supported by non-epithelial thymic stromal cells (TSCs), such as fibroblasts and endothelial cells, in an extracellular matrix-rich three-dimensional (3D) scaffold structure. TECs can be broadly divided into functionally and spatially distinct cortical (cTEC) and medullary (mTEC) subsets. Thymic epithelial progenitor cells (TEPC) support the development of both cTECs and mTECs during thymus organogenesis.

Deterioration of thymus function occurs naturally during aging and ultimately constrains the host immune repertoire. It is characterized by a reduction in total thymic cellularity and naive T cell production. Reduced TEC turnover and diminished levels of transcription factor forkhead-box N1 (FOXN1), a master regulator of TEC lineage specification, have been observed in the aged thymus. An increase in steroidal hormone production at puberty has also been implicated in age-related thymus involution, with androgen deprivation (AD) inducing the recovery of naive T cell production and bone marrow function in aged male mice and in humans. However, the mechanisms and signaling pathways causing the post-pubertal loss of specific TECs and underpinning AD-induced thymocyte regeneration remain unclear.

In this study, we examined numeric, phenotypic, and transcriptomic alterations in TEC and non-TEC (non-epithelial stromal cells, fibroblasts, and endothelial cells) stromal subsets during age-related thymic involution, and following transient thymic recovery via AD. We identify two major phases of thymic epithelial cell (TEC) loss during aging: a block in mature TEC differentiation from the pool of immature precursors, occurring at the onset of puberty, followed by impaired TEC progenitor differentiation and depletion of cTEC and mTEC lineage-specific precursors. We reveal that an increase in follistatin production by aging TECs contributes to their own demise. TEC loss occurs primarily through the antagonism of activin A signaling, which we show is required for TEC maturation and acts in dissonance to BMP4, which promotes the maintenance of TEC progenitors. These results support a model in which an imbalance of activin A and BMP4 signaling underpins the degeneration of postnatal TEC maintenance during aging, and its reversal enables the transient replenishment of mature TECs.


Suggesting that Cytomegalovirus Infection Contributes to Metabolic Syndrome

Metabolic syndrome is the precursor to type 2 diabetes, and is caused by the presence of excess visceral fat tissue. Age is a factor, however, in that people become more susceptible to the harmful consequences of being overweight in later life. Why is this the case? Recent evidence points towards the creation of additional lingering senescent cells as an important mechanism linking fat tissue to chronic inflammation and disruption of metabolism. Cellular senescence is an age-related mechanism.

The open access paper here proposes an intriguing additional process relating to persistent cytomegalovirus (CMV) infection. CMV is very prevalent, and the consensus on its effects is that its presence is an important contribution to the decline of the immune system with advancing age. Too many immune cells become specialized to tackling CMV, leaving too few for other tasks. In the context in which the supply of new immune cells is greatly diminished, due to loss of thymic tissue, and declining activity of hematopoietic stem cells, this is a big problem.

Cytomegalovirus (CMV) is a ubiquitous herpesvirus infecting most of the world's population. CMV has been rigorously investigated for its impact on lifelong immunity and potential complications arising from lifelong infection. A rigorous adaptive immune response mounts during progression of CMV infection from acute to latent states. CD8 T cells, in large part, drive this response and have very clearly been demonstrated to take up residence in the salivary gland and lungs of infected mice during latency. However, the role of tissue resident CD8 T cells as an ongoing defense mechanism against CMV has not been studied in other anatomical locations.

Therefore, we sought to identify additional locations of anti-CMV T cell residency and the physiological consequences of such a response. Through RT-qPCR we found that mouse CMV (mCMV) infected the visceral adipose tissue and that this resulted in an expansion of leukocytes in situ. We further found, through flow cytometry, that adipose tissue became enriched in cytotoxic CD8 T cells that are specific for mCMV antigens from day 7 post infection through the lifespan of an infected animal and that carry markers of tissue residence. Furthermore, we found that inflammatory cytokines are elevated alongside the expansion of CD8 T cells. Finally, we show a correlation between the inflammatory state of adipose tissue in response to mCMV infection and the development of hyperglycemia in mice.

Overall, this study identifies adipose tissue as a location of viral infection leading to a sustained and lifelong adaptive immune response mediated by CD8 T cells that correlates with hyperglycemia. This data potentially provides a mechanistic link between metabolic syndrome and chronic infection.


Mir-294 Awakens an Embryonic Proliferation Behavior in Heart Cells, Spurring Regeneration Following Heart Attack

That microRNA-294 (mir-294) beneficially affects heart regeneration was discovered via its presence in embryonic stem cell exosomes. Exosomes are extracellular vesicles, membrane-bound packages of molecules that cells pass between one another. They are interesting to the research community because it is in principle much easier to construct a therapy based on delivery of exosomes harvested from stem cells than it is to deliver those same stem cells. Thus most of the present generation of stem cell therapies may well be replaced in the near future by the delivery of extracellular vesicles, and many research groups are testing exosomes from stem cells to see how well they work to spur greater regeneration.

Most vesicles contain a wide variety of molecules, but in the case of embryonic stem cell exosomes and the injured heart, researchers found that near all of the therapeutic effect was mediated by mir-294. Thus they could go a step further and discard the exosomes as well as the cells. The results of that line of work are noted in today's publicity materials and paper. Applying mir-294 causes adult heart muscle cells to regress into a state more like that of embryonic cells, provoking greater replication and thus greater regeneration. This sort of in-situ reprogramming of cell behavior is growing in popularity in the research community, see the work of for example, though it remains to be seen whether or not it can be made safe enough to be the basis for a near future regenerative therapies.

Embryonic MicroRNA Fuels Heart Cell Regeneration, Temple Researchers Show

By adulthood, the heart is no longer able to replenish injured or diseased cells. As a result, heart disease or an event like a heart attack can be disastrous, leading to massive cell death and permanent declines in function. A new study is the first to show that a very small RNA molecule known as miR-294, when introduced into heart cells, can reactivate heart cell proliferation and improve heart function in mice that have suffered the equivalent of a heart attack in humans. "In previous work, we discovered that miR-294 actively regulates the cell cycle in the developing heart. But shortly after birth miR-294 is no longer expressed. The heart is very proliferative when miR-294 is expressed in early life. We wanted to see if reintroducing it into adult heart cells would turn them back to an embryonic-like state, allowing them to make new heart cells."

The researchers tested their idea in mice that had myocardial infarction (heart attack). Mice were treated with miR-294 continuously for two weeks after sustaining myocardial injury. Two months following treatment, the researchers observed noticeable improvements in heart function and a decrease in the area of damaged tissue. Examination of treated heart cells revealed evidence of cell cycle reentry, indicating that the cells had been reactivated, regaining the ability to produce new cells. "The miR-294 treatment reawakened an embryonic signaling program in the adult heart cells. Because of this, the old heart cells were no longer quite like adult cells, but neither were they fully embryonic. In this in-between state, however, they had the ability to make new cells."

Transient Introduction of miR-294 in the Heart Promotes Cardiomyocyte Cell Cycle Reentry After Injury

Embryonic heart is characterized of rapidly dividing cardiomyocytes required to build a working myocardium. Cardiomyocytes retain some proliferative capacity in the neonates but lose it in adulthood. Consequently, a number of signaling hubs including microRNAs are altered during cardiac development that adversely impacts regenerative potential of cardiac tissue. Embryonic stem cell cycle miRs are a class of microRNAs exclusively expressed during developmental stages; however, their effect on cardiomyocyte proliferation and heart function in adult myocardium has not been studied previously.

In this study, we determine whether transient reintroduction of embryonic stem cell cycle miR-294 promotes cardiomyocyte cell cycle reentry enhancing cardiac repair after myocardial injury. A doxycycline-inducible AAV9-miR-294 vector was delivered to mice for activating miR-294 in myocytes for 14 days continuously after myocardial infarction. miR-294-treated mice significantly improved left ventricular functions together with decreased infarct size and apoptosis 8 weeks after MI. Myocyte cell cycle reentry increased in miR-294 hearts parallel to increased small myocyte number in the heart. Isolated adult myocytes from miR-294 hearts showed upregulation of cell cycle markers and miR-294 targets 8 weeks after MI. Thus ectopic transient expression of miR-294 recapitulates developmental signaling and phenotype in cardiomyocytes promoting cell cycle reentry that leads to augmented cardiac function in mice after myocardial infarction.

Amyloid-β Causes Pericyte Dysfunction and Reduced Blood Flow in the Aging Brain

The brain is an energy-hungry organ, and the supply of oxygen and nutrients to brain tissue is vital to its function. This is one of the reasons why cardiovascular disease contributes to neurodegeneration. Researchers know that cells that wrap small blood vessels in the brain, called pericytes, tend to become dysfunctional or die in later life, another of the cellular casualties of the damage of aging. This causes greater constriction of the blood vessels, reducing the blood flow to tissues. Researchers here provide evidence for this to be a consequence of the aggregation of amyloid-β, characteristic of the early stages of Alzheimer's disease. This is an intriguing addition to what is known of the issues caused by protein aggregation in neurodegenerative conditions.

A new study looked at the role of pericytes, cells wrapped around capillaries that have the ability to contract and regulate blood flow. Researchers examined capillaries in Alzheimer's-affected human brain tissue and in mice bred to develop Alzheimer's pathology, and found that they were squeezed by pericytes. They also applied amyloid beta protein (which accumulates in the brains of people with Alzheimer's) to slices of healthy brain tissue, and found that the capillaries were squeezed as a result. They calculated that the constriction was severe enough to halve blood flow, which is comparable to the decrease in blood flow found in parts of the brain affected by Alzheimer's.

"Our study has, for the first time, identified the underlying mechanism behind the reduction of brain blood flow in Alzheimer's disease. Since reduced blood flow is the first clinically detectable sign of Alzheimer's, our research generates new leads for possible treatments in the early phase of the disease. Damage to synapses and neurons in Alzheimer's is usually attributed to the actions of amyloid and tau proteins accumulating in the brain. Our research raises the question of what fraction of the damage is a consequence of the decrease in energy supply that amyloid produces by constricting the brain's finer blood vessels. In clinical trials, drugs that clear amyloid beta from the brain have not succeeded in slowing mental decline at a relatively late phase of the disease. We now have a new avenue for therapies intervening at an earlier stage."


Efficiently Reprogramming Fibroblasts into Cardiomyocytes for Heart Regeneration

The heart regenerates only very poorly, and responds to injury by producing scar tissue, a process that involves fibroblast cells. Additionally, the age-related disruption of regenerative processes produced by senescent cells and chronic inflammation tends to empower fibroblasts to produce fibrosis in the heart even in the absence of injury. One potential approach to the challenge of poor heart regeneration and growing fibrosis is to reprogram the fibroblasts of scar tissue into functional heart muscle cells, cardiomyocytes. Given recent demonstrations of in situ cell reprogramming, it is plausible to think that this can be accomplished. The challenge is to do so without disrupting the vital structural and electrical properties of heart tissue.

A heart attack leaves damaged scar tissue on the heart and limits its ability to beat efficiently. But what if scientists could reprogram scar tissue cells called fibroblasts into healthy heart muscle cells called cardiomyocytes? Researchers have made great strides on this front with lab experiments and research in mice, but human cardiac reprogramming has remained a great challenge. Now, for the first time, researchers have developed a stable, reproducible, minimalistic platform to reprogram human fibroblast cells into cardiomyocytes.

The researchers introduced a cocktail of three genes - Mef2c, Gata4, and Tbx5 - to human cardiac fibroblast cells with a specific optimized dose. To increase efficiency, they performed a screen of supplementary factors and identified MIR-133, a small RNA molecule that when added to the three-gene cocktail - and with further in-culture modifications - reprogrammed human cardiac fibroblast cells into cardiomyocytes at an efficiency rate of 40 to 60 percent.

Analysis identified a critical point during the reprogramming process when a cell has to "decide" between progressing into a cardiomyocyte or regressing to their previous fibroblast cell fate. Once that process begins, a suite of signaling molecules and proteins launch the cells onto different molecular routes that dictate their cell type development. The researchers also created a unique cell fate index to quantitatively assess the progress of reprogramming. Using this index, they determined that human cardiac reprogramming progresses at a much slower pace than that of the previously well-described mouse reprogramming, revealing key differences across species and reprogramming conditions.


The Urge to Radical Life Extension

Those portions of the modern longevity community interested in bringing an end to aging and extending healthy human life span indefinitely tend to be the older portions, people who have been a part of the broader movement for quite some time. Newcomers tend to be more moderate, aiming at lesser goals. Perhaps this is a result of the successful projects, such as the SENS Research Foundation and Methuselah Foundation, tending to moderate their rhetoric as they attract a broader and larger base of support. I think that this road to moderation might be a problem, and that there is thus a continued role for those who loudly declaim that the goal is to control aging absolutely, via new medical technology, and that the natural consequence of that control is healthy, active, youthful life that extends for centuries or more.

If the goals that our movement works towards are broadly watered down from radical life extension of centuries to just adding a few more years, then marginal projects that can do no more than add a few more years will come to dominate the field to the exclusion of everything else. We are already more or less in this situation, in that that the vast majority of funding goes towards discovery and development of small molecules that tinker with the operation of an aged metabolism to make it a little more resilient to the underlying causes of aging. If that is all that is done, then we'll all age and die on basically the same schedule as our parents and grandparents. It will be a grand waste of opportunity, given that we have the knowledge and the means to do far better, such as by following the SENS agenda for rejuvenation biotechnologies based on repairing the root causes of aging.

This popular media article looks at a few of the people who do make no bones about aiming at radical life extension. It isn't terrible, thankfully, though it doesn't quite manage to escape the straitjacket of conformity, the author suggesting that it is somehow strange to want to live for a long time in good health, or strange to want to avoid a slow, crumbling, painful death. There is no present status quo so terrible that it will not have its defenders, and for whatever reason the status quo of aging and suffering and omnipresent death and loss are aggressively defended. But setting that aside, the article manages to capture the present state of development and the viewpoints of its subjects quite well, which is a change over past years of media attention.

How to live forever: meet the extreme life-extensionists

In 2016, an American real-estate investor named James Strole established the Coalition for Radical Life Extension, a nonprofit based in Arizona which aims to galvanise mainstream support for science that might one day significantly prolong human life. Standards in modern medicine are allowing us to live longer now than ever before. But that is not Strole's concern. What good are a few more measly years? He is interested in extending life not by days and weeks, but by decades and even centuries, to the degree that mortality becomes optional - an end to The End. He isn't alone. Life extensionists have become a fervent and increasingly vocal bunch. Famously, the community includes venture capitalists and Silicon Valley billionaires, non-gerontologists all, and nearly all men, who consider death undesirable.

The current life-extensionist strategy is twofold. First, achieve a "wellness foundation," Strole says. Second, stay alive until the coming gerontological breakthrough. All that is required is to "live long enough for the next innovation," and presuming you do, "You can buy another 20 years." Twenty years here, 20 years there, it all adds up, and suddenly you're 300. This is a common view. Last year the British billionaire Jim Mellon, who has written a book on longevity, titled Juvenescence, said: "If you can stay alive for another 10 to 20 years, if you aren't yet over 75 and if you remain in reasonable health for your age, you have an excellent chance of living to more than 110." To most, 110 seems a modest target. Why not forever? "It's not some big quantum leap," Strole says, by way of explanation. He invokes the analogy of a ladder: "step by step by step" to unlimited life. In 2009 the American futurist Ray Kurzweil coined a similar metaphor, referring instead to "bridges to immortality".

Aubrey de Grey, a serious scientist, considers life extension a health issue, which is perhaps the field's most convincing argument. Gerontologists are not hoping to end death, he says. Instead, "We're interested in people not getting sick when they get old." No matter how much society rails against the concept of immortality, nobody really wants to suffer through Alzheimer's, or suddenly fall foul of cardiovascular disease. Gerontology is the act of developing treatments for age-related diseases, de Grey argues - of reducing the causes of death, not death itself. "The benefits of living longer are not the point. The benefits are not having Alzheimer's disease." For de Grey, indefinite life is a by-product, not a goal.

Are we anywhere near to a breakthrough? So far, research has produced modest yields. Gerontologists speak prophetically of potential, but most warn a significant human development remains somewhere far off in the distance - almost in sight but not quite. Richard Hodes, the director of the National Institute of Aging, a US government agency, told me that, though research in animals has led to "dramatic increases in lifespan", some of them multi-fold, "There has been far less quantitative effect as those models have moved towards mammalian species." The biologist Laura Deming, who in 2011 established the Longevity Fund, a venture capital firm that supports "high-potential longevity companies", told me that startups continue to successfully root out biological markers of ageing - inefficient cells, mitochondrial decline - but that, in humans, "We really don't know right now what will work and what won't."

Much of gerontology focuses on identifying types of damage that accumulate with age and developing ways to halt or reverse that accumulation. It has been discovered, for example, that as we grow older, certain cells become senescent and harmful but nevertheless stick around, getting in the way like comatose guests at the end of a house party. Removing those cells have helped mice have longer, healthier lifespans. Similar forms of genetic engineering have been successful in other animal models. But to reach the mainstream, gerontologists must convince government agencies to support human adoption, a complicated and long-winded task, given the general view that death is a normal human process.

The Goal of Kidney Rejuvenation

The authors of this open access paper review the aging of the kidney and consider the prospects for using factors from young blood as a means of rejuvenation. This is a fairly narrow view, as there are many other approaches that should produce rejuvenation of the aged kidney, ranging from those close to realization, such as senolytic therapies to clear senescent cells, or various approaches to stem cell therapy, to those yet to be achieved, meaning much of the rest of the SENS agenda of rejuvenation biotechnologies to repair the damage that causes aging. Nonetheless, after so many years of trying to persuade the research community to open up on the topic of addressing the mechanisms of aging as a means of therapy, it is very pleasant to see so many publications in the literature doing just that. The present open discourse is a sea change in comparison to the silence of a decade or two ago, in which few researchers were willing to speak in public about treating aging. The science was always valid and promising, it is the culture that has changed for the better.

It is well established that aging is associated with structural and functional renal changes. With the possible exception of the lung, the changes in kidney function with normal aging are the most dramatic of any human organ or organ system. The normal kidney loses about 25% of its mass during aging, with the loss involving both cortical glomeruli and tubules. Functionally, the aging kidney has a parallel decline in both glomerular and tubular function. The Baltimore longitudinal study demonstrated an average of 0.75 mL/min/year decline in glomerular filtration rate (GFR) in 254 men without hypertension or kidney disease. The GFR loss rate is tripled in subjects over 40 as compared with those under 40.

Cellular senescence describes an everlasting growth arrest of still viable and metabolically active cells. The cell-cycle regulators and tumor suppressors p16Ink4a and p19ARF are involved in cellular senescence. The expression of p16 Ink4a in the kidney has been known to increase with age and could be found in a variety of renal cell types. Renal p16Ink4a expression has been suggested as an ideal marker for renal aging and shown to foresee transplant outcome. In normal human glomerular, p16Ink4a expression is increased with age and in all resident cell types. Studies in a transgenic mouse model confirmed that ablating p16Ink4a positive senescent cells not only prolongs the lifespan, but also attenuates glomerulosclerosis in aging kidney and decreasse blood urea nitrogen levels. Furthermore, depletion of p16Ink4a resulted in reduction of renal interstitial fibrosis and nephron atrophy in mice after ischemia-reperfusion injury, indicating inhibition of senescence provides a protective effect on the development of fibrosis.

Considering the increase of the aging population, it is extremely urgent to identify a way to retard the aging process or rejuvenate the community. To test the effects of young blood on aged organ, young blood infusion or parabiosis may be used. Parabiosis is an experimental model aiming to join the circulatory system of two animals. Heterochronic parabiosis is used to connect an aged partner to a young partner, and can be used to demonstrate the effects of young blood on aged organs, and vice versa. With this model, rejuvenation in the aged heterochronic parabiont has been shown in different organs such as muscle, liver, brain, and heart.

In aged kidneys, a recent study showed that young blood environment enhances the autophagy of aged kidney through down-regulation of aging-related protein p16Ink4a and SA-β-gal, up-regulation of autophagy factors Atg5 and LC3BII, and down-regulation of autophagic degradation protein p62. Moreover, recent studies provided evidence that young systemic milieu may alleviate renal ischemia-reperfusion injury in elderly mice probably through reduction of oxidative stress, inflammation, apoptosis, and enhancement of autophagy in the injured aged kidney. Although evidence showed that young blood can attenuate renal aging and injury induced by ischemia-reperfusion injury in elderly mice, it will be important to identify and study the effects of specific blood-borne rejuvenating factors in the young blood or aging factors in the old blood in addition to put efforts into delineate the mechanisms underlying the renal cell senescence. This information will provide novel ideas to turn back the clock of the aging kidneys.


Mesenchymal Stem Cells Improve Heart Regeneration via Macrophage Polarization

It is well known that the most commonly available forms of stem cell therapy produce benefits via signaling on the part of the transplanted cells, which soon die, rather than via any sort of integration of these cells into tissues. These treatments use varieties of what are called mesenchymal stem cells, which is actually a poorly defined, broad category. One clinic's mesenchymal stem cells are usually meaningfully different from those of the next. Nonetheless, these therapies fairly reliably reduce chronic inflammation. This can allow for improved regeneration in patients, but that outcome is much less reliable in practice.

The innate immune cells known as macrophages are important in the complex dance of tissue regeneration. In recent years researchers have become increasingly interested in deciphering and altering macrophage behavior, switching more of these cells from the aggressive and inflammatory M1 polarization, responsible for hunting pathogens, to the pro-regenerative M2 polarization. It is thought that aging is characterized by too much of a bias towards M1, and the balance might be forced back to M2 via the application of suitable therapies. It is perhaps not surprising that we should find that some existing therapies that can modulate inflammation and improve regeneration act through this mechanism.

Myocardial infarction (MI) is a major cause of coronary heart disease (CHD). More and more studies have shown that stem cells can play an important role in tissue repair and anti-inflammation. In particular, mesenchymal stem cells (MSCs) have shown anti-inflammatory and immunological functions. Indeed, MSCs have also been shown to have the potential to enhance the recovery and regeneration of the infarcted myocardium. The current belief on the role of MSCs in myocardial regeneration is their synthesis and secretion of cytokines and other trophic growth factors to signal to the injured myocardial cells, which may also involve anti-aging effects.

We have recently shown that the effects of transplantation of CD146+ MSCs on myocardial regeneration after MI exceeds the effects of transplantation of MSCs, likely resulting from reduction of aging-associated cellular reactive oxygen species in injured cardiac muscle cells (CMCs). Many effects of MSCs on tissue repair and cell regeneration are conducted through their crosstalk with macrophages. It is traditionally thought that macrophage are deemed to be white blood cells with a major functionality of swallowing and ingesting wastes, dying or dead cells, and impurities. Nevertheless, recently studies have shown that macrophages have much more functions other than phagocytosis. Therefore, a more complicated classification of macrophages has been applied, in which 2 subtypes of macrophages are distinguished by two phenotypes. One was named as "M1" macrophages, while the other alternatively polarized one was named as "M2" macrophages, which function in regulation of humoral immunity and promotion of tissue repair.

Since the role of macrophages in the MSC-mediated recovery of heart function after MI remains unclear, this question was thus addressed in the current study. We found that transplantation of MSCs did not alter the total number of the macrophages in the injured heart, but induced their polarization towards a M2-phenotype. Moreover, administration of TNFα into MSC-transplanted mice, which prevented M2-polarization of macrophages, abolished the effects of MSCs on recovery of heart function and on the reduction of infarcted cardiac tissue. Thus, our data suggest that MSCs may rejuvenate CMCs after ischemic injury at least partially through induction of M2-polarization of macrophages.


Reviewing the Role of Cellular Senescence in the Aging of the Heart

A slow accumulation of long-lived senescent cells takes place throughout the body over the years, and is involved in the age-related decline of all tissues. Cells become senescent constantly, in response to damage, a toxic environment, participation in the wound healing response, or simply reaching the Hayflick limit on replication. Near all newly senescent cells either quickly self-destruct or are soon hunted down by the immune system, but a tiny fraction survive to linger. Senescent cells do not replicate, but are very active, secreting a potent mix of inflammatory and other signals that disrupt cell behavior and tissue structure. A sizable fraction of the chronic inflammation of aging is produced by the activities of senescent cells, and this inflammation drives the progression of all of the common age-related diseases.

Fortunately, senescent cells can be reduced in number, a fraction selectively destroyed, via strategies ranging from small molecule senolytic drugs to suicide gene therapies. A fair number of startup biotech companies are moving towards human trials for their approaches to therapy, while at least some of the presently available prototype senolytic compounds appear likely to be effective enough and safe enough to consider using. Given the continued intermittent arrival of new evidence showing the sizable contribution of senescent cells to conditions from type 2 diabetes to Alzheimer's disease to lung disease to kidney disease and atherosclerosis, and that removing these cells reverses the progression of these age-related diseases, the future for this part of the field of rejuvenation biotechnology seems bright.

Cellular senescence in cardiac diseases

Aging and age-related disorders progress through an integration of complex biological processes, and do not allow a simple approach to understand the whole picture, however, evidence indicates the central roles of cellular senescence in the pathogenesis of these conditions. Prevalence of age-associated diseases, including atherosclerotic disorders or heart failure increases with chronological aging, and cells positive for senescent markers are now well recognized to have causal roles for the progression of pathologies in these age-related diseases. In vitro studies showed that exposure of young somatic cells to senescent cells promotes senescence of the young cells, and this is described as the "bystander effect". Pharmacological or genetic depletion of senescent cells contributed to reverse aging phenotype, and suppressed pathologies in chronological as well as age-related disease models.

Adult cardiomyocytes were long thought to be terminally differentiated post-mitotic cells, however, accumulating evidence indicates these cells retain proliferative capacity. It was previously reported that in humans, cardiomyocyte turnover was at a rate of less than 1% per year, and this was demonstrated to decline with aging both in humans and mice. The underlying machinery of diminished cardiomyocyte turnover with aging is yet to be defined, and whether this is attributable to cardiomyocyte senescence is not clear due to the lack of specific senescence markers. In mice, it was reported that chronological aging links with an increase in cardiomyocyte size, together with reactive oxygen species (ROS) production, telomere attrition, and high level of p53 or p16Ink4a expression. In this study, compared to young mice (4 months of age), aged mice (20-22 months of age) exhibited increased left ventricular weight and cardiomyocyte volume, and showed reduction in cardiomyocyte number, together with reduced ventricular function, indicating the pathological roles of cardiomyocyte senescence in the aged heart.

Heart failure can be characterized into two types depending on the level of systolic function. One is described as heart failure with reduced ejection fraction (HFrEF), another is classified as heart failure with preserved ejection fraction (HFpEF), and both types of heart failure are prevalent among elderly persons. In the failing heart, chronic sterile inflammation develops, and this is well recognized to promote cardiac remodeling. Inflammation in coronary microvasculature is now thought to have central roles in the pathogenesis of HFpEF, and it was recently indicated that cellular senescence in endothelial cells may also be involved. When senescence-accelerated mice were fed a high-fat high-salt diet, endothelial cell senescence developed in cardiac tissues, and this coincided with the typical hemodynamic and structural changes of HFpEF. Given that aged and/or obese population has higher prevalence for HFpEF, inhibition of endothelial cell senescence pathway may become a next generation therapy for this untreatable disorder.

Aerobic and Resistance Exercise Increases Muscle Tissue NAMPT in Older Individuals

Mitochondria provide chemical energy stores to power cellular operations, particularly vital in energy-hungry tissues such as brain and muscles. One portion of the decline in mitochondrial function in old age is characterized by loss of NAMPT and NAD+, though how exactly underlying damage that causes aging leads to this decline is unclear. It is known that a sizable fraction of the observed loss of muscle mass and strength with aging is avoidable, in the sense that it is possible to maintain strength and fitness until quite late in life, but most people choose not to put in the required effort. Losses can even be reversed when sedentary people take up exercise. Given this, it may not be surprising to find that exercise can restore NAMPT and NAD+ in older adults, which is something to bear in mind when considering the many groups selling supplements to enhance NAD+ levels.

Aging decreases skeletal muscle mass and strength, but aerobic and resistance exercise training maintains skeletal muscle function. NAD+ is a coenzyme for ATP production and a required substrate for enzymes regulating cellular homeostasis. In skeletal muscle, NAD+ is mainly generated by the NAD+ salvage pathway in which nicotinamide phosphoribosyltransferase (NAMPT) is rate-limiting. NAMPT decreases with age in human skeletal muscle, and aerobic exercise training increases NAMPT levels in young men. However, whether distinct modes of exercise training increase NAMPT levels in both young and old people is unknown.

We assessed the effects of 12 weeks of aerobic and resistance exercise training on skeletal muscle abundance of NAMPT, nicotinamide riboside kinase 2 (NRK2), and nicotinamide mononucleotide adenylyltransferase (NMNAT) 1 and 3 in young (≤35 years) and older (≥55 years) individuals. NAMPT in skeletal muscle correlated negatively with age, and VO2peak was the best predictor of NAMPT levels. Moreover, aerobic exercise training increased NAMPT abundance 12% and 28% in young and older individuals, respectively, whereas resistance exercise training increased NAMPT abundance 25% and 30% in young and in older individuals, respectively. None of the other proteins changed with exercise training. In a separate cohort of young and old people, levels of NAMPT, NRK1, and NMNAT1/2 in abdominal subcutaneous adipose tissue were not affected by either age or 6 weeks of high-intensity interval training.

Here we provide evidence that various exercise training modalities completely correct the age-dependent decline in skeletal muscle NAMPT abundance. Conversely, neither age nor exercise training affect levels of adipose tissue NAD+ salvage enzymes. Our findings underscore the importance of regular physical activity to restore skeletal muscle NAD+ salvage capacity with age and have general implications for treatment of metabolic disease.


eNAMPT as an Approach to Slowing Aging via Increased NAD+ Levels

Raising the amount of nicotinamide adenine dinucleotide (NAD+) present in cells improves mitochondrial function in old tissues in which naturally maintained NAD+ levels have declined with aging. Mitochondrial function is important in cellular health, but falters with age for reasons that are complex, multifaceted, and poorly understood. Declining quality control mechanisms may be a large part of it, but even that is a many-layered set of changes, a fair way removed from the root cause molecular damage of aging. The NAD+ enhancement strategy, while not fixing the underlying causes of the issue, appears capable of modestly slowing aging in animal studies. A number of approaches and supplements can allegedly achieve this goal; the data to hand suggests that they vary widely in effectiveness, but there is at least human trial data for nicotinamide riboside.

An enzyme called eNAMPT is known to orchestrate a key step in the process cells use to make energy. With age, the body's cells become less and less efficient at producing this fuel - called NAD - which is required to keep the body healthy. Researchers have shown that supplementing eNAMPT in older mice with that of younger mice appears to be one route to boosting NAD fuel production and keeping aging at bay. Unlike other studies focused on transfusing whole blood from young mice to old mice, the researchers increased levels of a single blood component, eNAMPT, and showed its far-reaching effects, including improved insulin production, sleep quality, function of photoreceptors in the eye, and cognitive function in performance on memory tests, as well as increased running on a wheel.

The researchers have also shown other ways to boost NAD levels in tissues throughout the body. Most notably, the researchers have studied the effects of giving oral doses of a molecule called NMN, the chemical eNAMPT produces. NMN is being tested in human clinical trials. "We think the body has so many redundant systems to maintain proper NAD levels because it is so important. Our work and others' suggest it governs how long we live and how healthy we remain as we age. Since we know that NAD inevitably declines with age, whether in worms, fruit flies, mice, or people, many researchers are interested in finding anti-aging interventions that might maintain NAD levels as we get older."

Research has shown that the hypothalamus is a major control center for aging throughout the body, and it is directed in large part by eNAMPT, which is released into the blood from fat tissue. The hypothalamus governs vital processes such as body temperature, thirst, sleep, circadian rhythms, and hormone levels. The researchers have shown that the hypothalamus manufactures NAD using eNAMPT that makes its way to the brain through the bloodstream after being released from fat tissue. They also showed that this eNAMPT is carried in small particles called extracellular vesicles. As levels of eNAMPT in the blood decline, the hypothalamus loses its ability to function properly, decreasing life span.

Levels of eNAMPT in the blood were highly correlated with the number of days the mice lived. More eNAMPT meant a longer life span, and less meant a shorter one. The researchers also showed increased life span with delivering eNAMPT to normal old mice. All mice that received saline solution as a control had died before day 881, about 2.4 years. Of the mice that received eNAMPT, one is still alive as of this writing, surpassing 1,029 days, or about 2.8 years. "We could predict, with surprising accuracy, how long mice would live based on their levels of circulating eNAMPT. We don't know yet if this association is present in people, but it does suggest that eNAMPT levels should be studied further to see if it could be used as a potential biomarker of aging."


Infection Induced Systemic Inflammation as a Contributing Cause of Alzheimer's Disease

The big question regarding Alzheimer's disease has always been why only some people suffer this form of dementia. While being overweight clearly increases the risk of dementia, and it is easy to argue that this is because of the chronic inflammation generated by visceral fat tissue, not every overweight individual progresses to the point of Alzheimer's disease. Some people who are not overweight suffer Alzheimer's disease. The condition starts with rising levels of amyloid-β aggregates forming in the brain, thought to be a progressive process occurring over a decade or more prior to any clinical symptoms, but why does this only happen to some people?

The attractive nature of the various infection hypotheses of Alzheimer's disease is that they can answer this question. Only some people with the relevant risk factors suffer Alzheimer's disease because exposure to infectious agents over a lifetime, particularly those that persist in the body, such as various herpesviruses, or lyme spirochetes, is a matter of chance, only loosely related to physical characteristics. In recent years, researchers have identified amyloid-β as an antimicrobial peptide, a part of the innate immune response to pathogens. In this context it makes sense for infection, particularly persistent infection, to be driving the raised levels of amyloid-β necessary to develop Alzheimer's disease.

In today's open access paper, the authors have a different emphasis on infection, suggesting that it is the raised inflammation resulting from infection that drives the progression of Alzheimer's disease. It is quite true that Alzheimer's has a strong inflammatory component. One interpretation of this is that high enough levels of amyloid-β cause dysfunction and cellular senescence in the immune cells of the brain, producing a state of chronic inflammation that in turn encourages the formation of damaging tau aggregates and the onset of the final, severe stage of the condition. But perhaps that inflammation is also a consequence of the infections that drive amyloid-β aggregation.

Infection-Induced Systemic Inflammation Is a Potential Driver of Alzheimer's Disease Progression

Among the different risk factors underlying Alzheimer's disease (AD), infection might play a role in late-onset AD. Over the past three decades, infectious agents such as bacteria, viruses, fungi, and protozoa have been reported to trigger the development of AD. The infection hypothesis is not a recent idea. In the 1990s, three laboratories from different countries associated the infection with the etiology of AD. Elderly patients infected with herpes simplex virus (HSV)-1 developed toxic accumulation of amyloid β (Aβ) and phosphorylated (p)-tau protein in the brain. In autopsy cases with histopathologically confirmed AD, spirochetes were found in blood, cerebrospinal fluid, and brain tissue. A national representative survey of US residents involving 1,194 patients with 1,520 hospitalizations for infection with severe sepsis revealed that sepsis survivors were independently associated with substantial and persistent new cognitive impairment and functional disability. All of these studies support the notion that infectious etiology might be a causative factor for the inflammatory pathway associated with AD progression.

The accumulation of misfolded amyloid-β (Aβ) in the brain has been proposed to be the critical triggering event in a complex pathophysiological cascade that leads to AD pathology. The additional physiological role of Aβ as an antimicrobial agent in in vitro and in vivo models has been shown. Studies suggested that Aβ oligomerization, which is considered a pathological development in the context of neurodegeneration, may be a necessary step to potentiate the antimicrobial activity of the peptide. These results raised some important questions about the association between AD and microbial infection. The authors also unveiled the mechanism by which Aβ elicits its antimicrobial property. Aβ binds to a microbe and entraps it by forming amyloid fibrils. The presence of microbes serves as an efficient surface for nucleation of amyloid aggregates, thereby raising the possibility of amyloid deposition.

Even so, the findings raise the question of how the protective function of Aβ fails. The possible answer is microglial dysfunction; accumulation of biologically active peptides following an infection might have not been effectively cleared by microglia in the brain of patients with AD. Additionally, Aβ accumulation in the brain may act as an early toxic event in the pathogenesis of AD. The Aβ monomers, soluble and probably nontoxic, would aggregate into different complex assemblies, including soluble oligomers and protofibrils, with various degrees of toxicity. That may spread throughout the brain, and eventually developed into insoluble amyloid fibrils further assembled into amyloid plaques, which are one of the characteristic histological lesions on AD brains.

Recently, the results from three different groups of investigators demonstrated that sepsis, a life-threatening acute organ dysfunction due to a dysregulated host immune response after infection, induces systemic inflammation that exacerbates the accumulation of Aβ and triggers AD progression. these reports suggest that inflammation is a cardinal component of the pathophysiology of sepsis. Thus, the role of inflammation might be associated with the long-term cognitive impairment observed in sepsis survivors.

Although the molecular cascade that links systemic inflammation and neuroinflammation is still enigmatic, the possible modules that occur after infection, which lead to long-term impairment and brain dysfunction that ultimately trigger AD pathology, may include the following: Invading microorganisms escalate the peripheral Aβ load, a necessary step to neutralize and eliminate the pathogen from the peripheral environment. The peripherally produced Aβ and cytokines enter the central nervous system as systemic inflammation is able to increase blood-brain barrier permeability. An increase in RAGE expression during systemic inflammation also facilitates the transport of Aβ to the central compartment. Finally, the entry of foreign substances triggers brain-immune system crosstalk, which in turn leads to activation of microglia / astrocytes and local production of inflammatory mediators and reactive species. Further comprehension of these mechanisms with newer insights is warranted to develop a strategy for the potential advancement of therapeutics for infection-induced AD progression.

How α-synuclein Spreads Between Cells in the Brain

Protein aggregates of varying sorts are a feature of neurodegenerative conditions. A very small number of the countless different proteins found in human biochemistry can become misfolded or otherwise altered in ways that cause them to both (a) precipitate into solid deposits and (b) draw in more of the same proteins to also aggregate. The aggregates further generate a halo of associated biochemistry that is toxic or disruptive to function in brain cells. Aggregates can also spread between cells, as illustrated here. A sizable fraction of the research community in this part of the field is interested in finding ways to interfere in this spreading process, as in principle that could be the basis for a means to prevent these conditions.

Neurodegenerative diseases, such as Alzheimer's, Parkinson's and Huntington's disease, affect different regions of the human brain. Despite these regional differences, research has shown that the processes inside cells affected by these diseases have a lot in common. One characteristic of these diseases is that specific proteins start to form aggregates, or deposits, that damage and eventually kill the cell. In Parkinson's disease, it is misfolded forms of a protein known as α-synuclein that are involved. These aggregates can recruit normal forms of α-synuclein, causing the formation of more protein aggregates.

It has long been known that cells that lie close to each other can create small channels (known as gap junction channels) between them. These small channels are built from members of a family of proteins known as connexins. Studies by other scientists have suggested that connexins play a role in other types of disease,. This led researchers to wonder whether connexins can play a similar role in the spread of Parkinson's disease in the brain.

The brain contains more than 10 connexins, but the study suggests that the protein deposits in Parkinson's disease interact with only one of them, Cx32. Details of the process by which the harmful proteins transfer from one cell to a neighbouring cell with the aid of the channel-forming protein remain unclear. The scientists do know that the channel created by connexin is too narrow for the protein aggregates to pass through. They have shown that the aggregates bind to the channel-forming protein Cx32 and sneak into the cell together with it. When the researchers inhibited the formation of channels in cells in culture, absorption of α-synuclein was prevented. In experiments using brain tissue from four deceased patients diagnosed with Parkinson's disease, the scientists observed a direct binding between synuclein and connexin in two of the cases, which suggests that they interact with each other also in the Parkinsonian brain but not in normal brains.


Enhancing Mitophagy to Improve Mitochondrial Function in Old Individuals

Mitochondria are the power plants of the cell, packaging chemical energy store molecules to power cellular operations. Mitochondrial function declines with aging, and as one might expect this drags down all aspects of cellular functioning with it. Evidence suggests that this form of degeneration is strongly connected to a failure of the quality control mechanism of mitophagy, which identifies and recycles damaged mitochondria. The proximate cause may be changes in mitochondrial dynamics, particular a diminished amount of fission, the splitting of larger mitochondrial into multiple smaller organelles, leaving too many large and broken mitochondria that cannot be effectively recycled. The connection between this and the known root causes of aging remain obscure.

It is plausible that mitochondrial function is so important to health that some benefit for older individuals can be obtained via forcing greater mitochondrial fission and mitophagy, via changing levels of regulatory proteins, even without addressing the underlying causes. The question at the end of the day is always the size of the effect, of course: even when significant gains are observed in short-lived species, it isn't necessarily the case that this will carry through into long-lived humans. Similarly, upregulating mitochondrial quality control might be far more useful for people with poor lifestyles than for those who have maintained their physical fitness. The research noted here is an example of the standard drug development process applied to the goal of upregulating mitophagy. A natural compound was discovered to boost mitophagy, and after further evaluation was taken into human clinical trials.

During aging, there is progressive decline in the cell's capacity to eliminate its dysfunctional elements by autophagy. Accumulating evidence has highlighted the decrease in the specific autophagy, or recycling, of dysfunctional mitochondria, known as mitophagy, in aging skeletal muscle. This can result in poor mitochondrial function in the skeletal muscle, and has been closely linked to slow walking speed and poor muscle strength in elderly individuals. Consequently, improving mitochondrial function in elderly people by restoring levels of mitophagy represents a promising approach to halt or delay the development of age-related decline in muscle health.

Urolithin A (UA) is a first-in-class natural food metabolite that stimulates mitophagy and prevents the accumulation of dysfunctional mitochondria with age, thereby maintaining mitochondrial biogenesis and respiratory capacity in cells, and, in the nematode Caenorhabditis elegans, improving mobility and extending lifespan. In rodents, UA improves endurance capacity in young rats and in old mice either fed a healthy diet or placed under conditions of metabolic challenge. Recently, UA was shown to have a favourable safety profile following a battery of standardized toxicological tests.

In this report, we detail the outcome of a first-in-human, randomized, double-blind, placebo-controlled clinical study with UA. We administered UA, either as a single dose or as multiple doses over a 4-week period, to healthy, sedentary elderly individuals. We show that UA has a favourable safety profile (primary outcome). UA was bioavailable in plasma at all doses tested, and 4 weeks of treatment with UA at doses of 500 mg and 1,000 mg modulated plasma acylcarnitines and skeletal muscle mitochondrial gene expression in elderly individuals (secondary outcomes). These observed effects on mitochondrial biomarkers show that UA induces a molecular signature of improved mitochondrial and cellular health following regular oral consumption in humans.

The present study reveals that UA induces a molecular signature response, in both the plasma and skeletal muscle of humans, resembling that observed as a consequence of a regular exercise regimen. It is important to highlight that our earlier work revealed that the stimulation of mitophagy by UA led to an induction of mitochondrial biogenesis and an enhancement of mitochondrial function, resulting in improved aerobic endurance and higher muscle strength in treated rodents. In humans, endurance exercise is well known to trigger mitochondrial biogenesis and fatty acid oxidation in the skeletal muscle to optimize efficient production of ATP by skeletal muscle cells under aerobic conditions. It has also been shown that exercise is a natural means of triggering mitophagy, making it particularly important to maintain an active lifestyle during aging, as it ultimately results in improved mitochondrial function in the muscle.


Take Optimal Care of Your Health and the Odds of Reaching Age 90 are Still Poor with Today's Medical Technology

It is important to take good care of your health. This means the simple, sensible lifestyle choices: stay fit, stay lean, don't smoke, and so on. If you don't do this, then you'll have a shorter and less pleasant life. You'll spend much more on medical expenses. It is worth the effort to evade those outcomes. But don't believe that you are going to beat the odds on longevity in any exceptional way just because you took good care of your health. You'll likely beat the odds in a minor way, but two thirds to three quarters of the healthiest people in the world die before reaching age 90. That fraction only increases for everyone else, as today's open access paper well illustrates.

The point to take away from this is not to fixate on the world of health and lifestyle. Just do the simple, sensible things, and don't make a big deal of it. Have a reasonable expectation of the outcome. If far greater healthy longevity is the goal, then the only way you, I, or anyone else can achieve it is through the development of rejuvenation therapies that can repair and reverse the causes of aging. Aging is a process of damage accumulation, followed by all of the harmful downstream consequences of that damage. Repairing that damage periodically is the only way that we will be able to reliably live much longer in good health. While the first, crude rejuvenation therapies exist, senolytic drugs that can destroy some of the senescent cells that harm tissue function in later life, they are only a first step on a long road. A lot of work lies ahead. Consider helping.

Survival to Age 90 in Men: The Tromsø Study 1974-2018

The 738 oldest men who participated in the first survey of the population-based Tromsø Study (Tromsø 1) in Norway in 1974 have now had the chance to reach the age of 90 years. The men were also invited to subsequent surveys (Tromsø 2-7, 1979-2016) and have been followed up for all-cause deaths. This study sought to investigate what could be learned from how these men have fared. The men were born in 1925-1928 and similar health-related data from questionnaires, physical examination, and blood samples are available for all surveys. Survival curves over various variable strata were applied to evaluate the impact of individual risk factors and combinations of risk factors on all-cause deaths. At the end of 2018, 118 (16.0%) of the men had reached 90 years of age.

Smoking in 1974 was the strongest single risk factor associated with survival, with observed percentages of men reaching 90 years being 26.3, 25.7, and 10.8 for never, former, and current smokers, respectively. Significant effects on survival were also found for physical inactivity, low income, being unmarried, high blood pressure, and high cholesterol. For men with 0-4 of these risk factors, the percentages reaching 90 years were 33.3, 24.9, 12.4, 14.4, and 1.5, respectively. Quitting smoking and increasing physical activity before 55 years of age improved survival significantly.

The main finding of this study is the huge reduction in observed life length for men with two or more of the risk factors identified in this study, i.e., current smoking, physical inactivity, low income, being unmarried, high blood pressure, or high total cholesterol. Reported in adult mid-life, these risk factors started to take their toll as early as approximately 55 years of age, and over time, more and more lives were lost. The large effect of lifestyle characteristics at adult middle-age was further underlined by the decreasing survival time and smaller number of men reaching 90 years of age that was observed with increasing number of risk factors. Although each of these risk factors alone was associated with premature death, their massive joint effect emphasizes the benefits of eradicating as many of them as possible.

Renormalized Basal Metabolic Rate as a Biomarker of Aging

The research community is very interested in producing biomarkers that can accurately measure the progression of aging, and the variance in the pace of aging from individual to individual. In a world in which therapies to slow or reverse aging are being developed and tested, progress will be slow until such time as there are easy, cost-effective ways to measure the state of aging before and after a treatment. It is an important area of research. While a universal biomarker of aging, one that works equally well to assess any class of therapy to treat aging, is probably too much to hope for, given that aging is caused by many distinct processes, the diversity of efforts to produce such a biomarker of aging should nonetheless lead to useful tools as the field advances.

Recent aging theories have proposed various causative biomarkers such as reactive oxygen species, calorie restriction, telomere length, insulin signaling, mitochondrial (mt) DNA mutations, fatty acid composition of membranes, and methylation. To date, the validity of these biomarkers has been examined mainly by investigating their age dependency. However, they are not satisfactory for an accurate description of the aging process, and they seem to interact with each other in a complex way. Thus, it is essential to explain how these biomarkers can show that the survival curve and mortality rate are directly related to longevity. Indeed, the probability of survival drops markedly in individuals over the age of 80, and the mortality rate increases exponentially up to the age of 100.

We here propose a new biomarker to describe the mortality rate and survival curve of the elderly. The basal metabolic rate (BMR) has long been known to decline with age, in line with the Harris-Benedict equation (HBE), which is useful for statistical analysis of a large amount of data. The mass-specific BMR (msBMR; BMR per unit mass) confers the standard normalization of BMR to decrease the variation based on the body weight of individual persons. However, the obtained msBMR still varies among them. We developed an approach in which a universal metabolic rate function of age was derived by renormalizing the msBMR. The first renormalization was attained by incorporating the body mass index (BMI) into the HBE. Interestingly, the variation of the msBMR was thus markedly decreased. We further performed a second renormalization to remove the remaining variation due to individual height by a little readjustment of the BMI. As a result, the renormalized msBMR (RmsBMR) revealed an exponential decline with only age.

The RmsBMR is likely proportional to cellular metabolism and then to the mitochondrial number (mt density) within the standard cell. The mt density was found to decrease very slowly with age. The exponential decay form of this density was shown to be a solution of the transport equation for the mitochondrial dynamical fusion/fission flow. This decay form was proven to be based on the Markov process, although the basic mechanism behind the occurrence of the mitochondrial dysfunction has remained unresolved.


Unity Biotechnology Announces Results from a Senolytics Trial for Osteoarthritis

Unity Biotechnology is the furthest ahead of the growing number of young biotech companies working on senolytic therapies that can selectively destroy harmful senescent cells in aged tissues. The company has already started human trials for osteoarthritis of the knee, using local rather than systemic administration of a small molecule senolytic drug. Other companies in the space, such as Oisin Biotechnologies, will be starting in on human trials for their approaches soon. As noted here, Unity Biotechnology recently announced results from their trial.

The accumulation of senescent cells throughout the body over the years is one of the causes of aging, and removing these cells reliably produces rejuvenation in mouse studies, meaning reversal of measures of aging, reversal of the progression of age-related diseases, and extended life spans. Senescent cells cause harm in a number of ways, one of which is the generation of chronic inflammation in surrounding tissues. Many age-related conditions with a strong inflammatory component appear to be caused in large part by senescent cells, and osteoarthritis is one of them.

The Phase 1 clinical trial of UBX0101 is a randomized, double-blind, placebo-controlled study evaluating the safety, tolerability and pharmacokinetics of a single intra-articular injection of UBX0101 in patients diagnosed with moderate to severe painful OA of the knee. UBX0101 is a p53/MDM2 interaction inhibitor that targets selective elimination of senescent cells.

In Part A, 48 patients were randomly assigned to receive one of six dose levels of UBX0101 (between 0.1 mg to 4 mg) or placebo in a 3:1 randomization. Primary endpoints were safety and tolerability. Secondary and exploratory endpoints included plasma pharmacokinetics, synovitis as measured by MRI, pain, and measurement of senescence-associated secretory phenotype (SASP) factors and disease-related biomarkers present in synovial fluid and plasma.

In Part B, 30 patients were randomized to receive UBX0101 (4 mg dose) or placebo in a 2:1 randomization. Primary endpoints were safety and tolerability. Secondary and exploratory endpoints included changes in the levels of SASP factors and disease-related biomarkers present in synovial fluid and plasma, and pain. Synovial fluid samples were obtained at baseline and four weeks post-treatment.

In Part A, UBX0101 was well tolerated up to the maximum administered dose of 4 mg. There were no serious adverse events and no patients discontinued because of an adverse event. There were no dose-dependent adverse events or relevant clinical laboratory findings. The majority (66%) of adverse events were mild. In Part B, UBX0101 was well tolerated at the 4 mg dose. There were no serious adverse events and no patients discontinued because of an adverse event. The majority (75%) of adverse events were mild and there were no relevant clinical laboratory findings.

The study demonstrated that UBX0101 was safe and well-tolerated. Improvement in several clinical measures, including pain, function, as well as modulation of certain SASP factors and disease-related biomarkers was observed after a single dose of UBX0101. In approximately half the biomarkers measured in synovial fluid (treatment versus placebo) modulation was observed consistent with elimination of senescent cells and potential improvement in the tissue environment. Changes were observed in MMPs, tissue remodeling factors, and inflammatory cytokines.


Progression of Atherosclerosis is Slowed in Mice via Targeting Senescent Cells

Atherosclerosis is the build up of plaques in blood vessel walls, composed of fats and the debris of dead cells. Blood vessels are narrowed and weakened, and eventually something important ruptures or blocks, producing a heart attack or stroke. Cholesterols circulate in the bloodstream, attached to low-density lipoprotein (LDL) particles. The immune cells known as monocytes are responsible for ensuring that excess cholesterols stuck in blood vessel walls are removed and returned to the liver to be excreted. They do this by entering blood vessel walls, transforming into macrophages, ingesting the cholesterols, and then handing them off to high-density lipoprotein (HDL) particles.

In older individuals, increased inflammation and oxidative stress causes macrophages to become dysfunctional. Macrophages can be overwhelmed by large amounts of cholesterol, but it takes comparatively little oxidized cholesterol to turn a macrophage into a dysfunctional, inflammatory foam cell, unable to carry out its assigned tasks. Much of an atherosclerotic plaque is made up of the debris of dead macrophages, rich in oxidized cholesterols. Surviving cells signal for aid, calling in more monocytes to destruction. Chronic inflammation in blood vessel tissues makes this feedback loop run that much faster.

A sizable fraction of the chronic inflammation of aging is caused by the presence of senescent cells. These cells are created day in and day out in large numbers, and this is an important part of the normal operation of cellular metabolism. They have important roles in wound healing and cancer suppression, for example. The vast majority of senescent cells either self-destruct or are destroyed by the immune system, but a tiny fraction linger. They secrete a potent mix of signals that disrupt tissue function and produce inflammation. Fortunately, eliminating senescent cells is a going concern, with numerous approaches in human trials or under clinical development. In today's open access paper, researchers demonstrate a novel approach to diminishing the impact of cellular senescence in blood vessel walls, thereby slowing the progression of atherosclerosis. This adds to the existing data that suggests senolytic therapies should produce benefits in this condition.

Knockdown of angiopoietin-like 2 induces clearance of vascular endothelial senescent cells by apoptosis, promotes endothelial repair and slows atherogenesis in mice

Senescent cells lose their proliferative potential in response to various stresses. They secrete a variety of pro-inflammatory mediators and proteases, gathered in the senescence-associated secretory phenotype (SASP) that engages the immune system to eliminate senescent cells. Senescent cells accumulate in aging organisms, chronic age-related diseases and benign tumors; conversely, elimination of senescent cells contributes to improve health. They also accumulate in tissues affected by atherosclerosis and their elimination strikingly reduces atherogenicity in animal models. Senescence is thus a link between molecular damage and the altered physiology of aging, and targeting SnC using senolytic drugs appears a promising strategy to reduce the burden of age-related chronic inflammatory diseases, including atherosclerosis.

Angiopoietin like-2 (angptl2) is a member of the SASP and is detectable in most organs of adult mice. Angptl2 is expressed by senescent vascular human endothelial cells (EC), but not quiescent or proliferative EC and is atherogenic when infused in young atherosclerotic (ATX) mouse models. We reported that plasma levels of angptl2 are elevated in patients with cardiovascular diseases (CVD), were associated with endothelial dysfunction, and were predictive of major cardiac adverse events and death. Recently, we reported a strong relationship between arterial expression of p21, a cell cycle inhibitor overexpressed in senescent cells and maintaining growth arrest, and circulating levels of angptl2 in atherosclerotic patients. Senescent EC are activated and promote aggregation of leukocytes, the initiating step of atherogenesis. We therefore hypothesized that down-regulation of vascular angptl2, preferentially in the endothelium of severely dyslipidemic ATX mice would promote endothelial repair and slow atherogenesis.

Here, we report that knockdown of vascular angptl2 by a shRNA (shAngptl2), delivered to the vascular cells via a single injection of an AAV1, slowed atheroma progression in ATX mice. Knockdown of angptl2 was associated with a rapid reduction in the expression of EC senescence-associated p21 accompanied by the increase in Bax/Bcl2 ratio as a marker of apoptosis; subsequently, this was associated with endothelial repair as evidenced by the incorporation of endothelial progenitor CD34+ cells. In addition to our pre-clinical results, we show that vascular ANGPTL2 gene expression is correlated with p21 expression and inflammatory cytokines in the internal mammary artery isolated from severely atherosclerotic patients undergoing a coronary artery bypass surgery. Altogether, our data suggest that targeting vascular angptl2 could be senolytic, delaying the progression of atherosclerosis.

Extracting Evidence for Causation from the Correlation Between Excess Fat Tissue and Risk of Cardiovascular Disease

Given a good enough data set, there are ways to produce evidence for causation in the observed relationships between patient characteristics and risk of age-related disease. While it is well accepted by now that being overweight does in fact cause a raised risk of all the common age-related diseases, a shorter life expectancy, and a raised lifetime medical expenditure, more data never hurts. Researchers have a good understanding of the mechanisms involved in these relationships. In particular, visceral fat tissue around the abdominal organs generates chronic inflammation, which acts to accelerate tissue decline and age-related dysfunction. This inflammation is perhaps largely produced through the creation of increased numbers of senescent cells, but there are numerous described mechanism with the same outcome.

Mendelian randomisation is a way of showing whether or not individual risk factors actually cause disease, rather than just being associated with it. It uses genetic variants that are already known to be associated with potential risk factors, such as body mass index (BMI) and body fat, as indirect indicators or "proxies" for these risk factors. This enables researchers to discover whether the risk factor is the cause of the disease (rather than the other way around), and reduces bias in results because genetic variants are determined at conception and cannot be affected by subsequent external or environmental factors, or by the development of disease.

Researchers studied 96 genetic variants associated with BMI and body fat mass to estimate their effect on 14 cardiovascular diseases in 367,703 participants of white-British descent in UK Biobank - a UK-based national and international resource containing data on 500,000 people, aged 40-69 years. Using Mendelian randomisation they found that higher BMI and fat mass are associated with an increased risk of aortic valve stenosis and most other cardiovascular diseases, suggesting that excess body fat is a cause of cardiovascular disease.

People who had genetic variants that predict higher BMI were at increased risk of aortic valve stenosis, heart failure, deep vein thrombosis, high blood pressure, peripheral artery disease, coronary artery disease, atrial fibrillation, and pulmonary embolism. For every genetically-predicted 1kg/m2 increase in BMI, the increased risk ranged from 6% for pulmonary embolism to 13% for aortic valve stenosis. (Above a BMI that is considered "healthy" (20-25 kg/m2) every 1 kg/m2 increase in BMI for someone who is 1.7 metres tall (5'7") corresponds to a weight gain of nearly 3 kg)


Activism for Longevity

The modern community of activists and patient advocates focused on the treatment of aging, carried out to significantly extend healthy longevity, has existed in some form since the 1970s. The early decades were largely a matter of supplements and hope, however, not a real prospect for slowing aging to any sizable degree. Only in the past twenty years has the community advanced to the point at which it became plausible to meaningfully tackle the causes of aging, and only in the past ten years has support and awareness increased to the point at which earnest progress could take place.

While the first, comparatively crude rejuvenation therapies already exist in the form of senolytic compounds capable of selectively destroying a fraction of the harmful senescent cells present in aged tissues, this is but a starting point. There is a lot of work left to accomplish in the years ahead. Many more classes of rejuvenation therapy will be needed to repair or clear out other forms of damage in aging tissues, and few are as actively developed as they might be. Even as funding for research and clinical development of rejuvenation therapies increases, there will continue to be an important role for advocacy and activism: almost no amount of funding is ever enough, and all too much of it will go to the wrong sorts of programs, if the controlling parties are left to their own devices.

There is now an emerging international social advocacy movement dedicated to promotion of biomedical research and development to alleviate aging-related morbidity, extend healthy period of life, and improve healthy longevity for the elderly population. It is commonly referred to by the activists as the "longevity movement" or "longevity research and advocacy movement," as well as "healthy life extension movement." It is a "hybrid" between the aged rights advocacy, patient advocacy, and science advocacy, as it emphasizes the need to implement preventive medicine to improve health care for the elderly around the world via enhanced medical scientific research with a special focus on the mechanisms of biological aging.

The goals of the movement, defined by the organizations, initiative groups, and individual activists representing it, are the following: (a) to increase public awareness of the plausibility and desirability to bring the processes of aging under medical control, thus extending healthy human life span, delaying the manifestation of age-related diseases, and improving health in the older age; (b) to foster the improvement of the local and global legislation concerning health across the life course, aging, health and well-being of the elderly, and medical research with a special focus on the mechanisms of aging; (c) to allocate more public funding to fundamental and translational research on the mechanisms of aging and age-related diseases; (d) to increase the interest of the investment industry in supporting biotechnology companies developing innovative drugs and therapies targeting the underlying mechanisms of aging and thus able to prevent, delay, or cure age-related diseases; (e) to promote clinical implementation of the evidence-based medical and lifestyle means to extend healthy human life span.

The movement embraces the recent advances of biomedical science proving the possibility to intervene into the degenerative processes of aging to slow down, delay, prevent, and reverse age-related damage accumulation and seeks to enhance and accelerate such advances. The movement is still young and emerging and is not yet strongly related to other forms of health-care advocacy. But a stronger relation is hoped for.


Discussing the DNA Damage Hallmark of Aging at Long Long Life

The Long Long Life team will be putting together a set of videos in the months ahead, one for each of the Hallmarks of Aging. The first to be published covers the hallmark of DNA damage, stochastic mutational change to nuclear DNA that is widely thought to make a meaningful contribution to the dysregulation of cell behavior in aging. This is evidently the case for cancer risk, as cancer is caused by mutations that enable rampant, unregulated growth, but may only be important otherwise when mutations occur in stem cells or progenitor cells that are able to propagate the mutations widely in tissues.

The Hallmarks of Aging is a list of common processes and outcomes found in aging, and considered by a sizable fraction of the research community to cause aging. While the hallmarks overlap with the list of forms of cell and tissue damage described in the earlier Strategies for Engineered Negligible Senescence (SENS), a view of aging as accumulated molecular damage, the two differ in that some of the hallmarks are clearly not fundamental causes of aging in the SENS view. They are some way downstream from the forms of molecular damage that would be considered true causes of aging. For example, the hallmarks include loss of proteostasis and dysregulation of nutrient sensing. Both of these are managed by collections of cell behaviors and states; we must ask what causes those behaviors and states to change, and the answer must be some form of underlying damage.

[Video] The 9 Hallmarks of Aging, episode 1, DNA damage

The first cause of aging that we will address are the damage to our DNA over time. DNA is the medium of information that makes us who we are, the manufacturing program of our body. This information is made up of genes and all genes are grouped together under the name "genome". All this information must be transmitted from one cell to another when they divide to generate daughter cells. And for that, it is necessary to replicate the DNA integrally at each cellular division.

Unfortunately, even this very powerful replication system is not without errors. It has been noted that DNA errors accumulate in life, as many factors influence the stability of the genome. These factors are varied and can be external, such as smoking, sunlight, food ... but also internal, such as replication errors: when your body has to copy the information contained in your DNA, it makes mistakes. These errors can either be repaired, cause cell death, or, and this is the problem, be transmitted to daughter cells.

Fortunately, we have repair systems. Some genes build proteins to repair replication errors, but sometimes the replication errors affect the genes that make these repair systems and, through a snowball effect, there is an exponential growth of problems within the cell. In mice and humans, it has been shown that there is a causal link between DNA damage accumulation and aging. In fact, when the cells in our body divide a large number of times and are carriers of genetic mutations, this causes a dysfunction of the cell that can cause problems at the level of the organ concerned.

Interestingly, it has been shown that during aging, repair systems (such as the PARP protein) become much more abundant in cells, suggesting that our body is aware of the deregulations that come with age and tries to take the necessary steps to fight them. The activity of these repair systems is however dependent on co-enzymes, small molecules that allow them to function. These are essential fuels for our cells whose concentration and recycling decreases with age. Among them, NAD+ is often mentioned, because it is essential to repair mechanisms, but also to mitochondrial health. When these molecules eventually run out, our repair systems no longer work well, leading to serious disruptions, not only in replication but also in other mechanisms, up to and including cell death.

Supplementing with NAD+ may be a good idea to boost our repair systems but it is also possible that cell suicide linked to NAD+ depletion is a protection of the body against cells that have become genetically diseased and that it would be preferable to eliminate. Researchers have used mice, which have been treated to keep a constant level of NAD+ throughout their lives. And not only the treated mice lived healthier lives but they also lived longer than the untreated mice. This shows that, in mice in any case, upregulating NAD+ seems to be a good idea to fight against aging. In humans, as usual, this remains to be proven.

Changing Macrophage Behavior to Improve Regeneration Following Heart Attack

The innate immune cells known as macrophages play an important role in the coordination of regeneration, in addition to their tasks related to defense against pathogens and clearance of debris and molecular waste. Macrophages adopt different polarizations, or collections of behaviors, under different circumstances. Researchers are very interested in finding ways to force macrophages to adopt a desired polarization, such as to switch inflammatory, aggressive macrophages into a kinder, gentler pro-regeneration state. The research noted here is an example of those efforts, in that the scientists involved are attempting to make macrophages participate more readily in the regrowth of blood vessels following damage to the heart, such as that produced by a heart attack.

Despite the advent of new therapeutic strategies to restore blood flow, we are not yet able to prevent the onset of heart failure following myocardial infarction (MI). Hence, it is a major challenge to identify innovative strategies to restore nutrient supply to the infarcted myocardium, ultimately aimed at regeneration of myocardial functionality. The cellular response following MI is characterized by a rapid recruitment of neutrophils. Their arrival is superseded by the infiltration of classical monocytes, which contribute to clearance of debris. However, this subset also drives robust inflammation, leading to pathological remodeling. In contrast, the appearance of nonclassical monocytes and reparative macrophages marks a turning point between inflammation and its resolution, as these cells govern repair and angiogenesis. At this point, knowledge about mechanisms regulating this cellular switch and about origin and identity of molecular cues involved is scarce.

Annexin A1 (AnxA1) is quickly released upon cellular stress; it acts through Formyl peptide receptor-2 to prevent chemokine-mediated integrin activation, and thus, turns off inflammatory recruitment of myeloid cells. AnxA1 also activates pro-repair mechanisms by activation of Rac1 and NOX1, resulting in enhanced epithelial cell migration after injury. Local intestinal delivery of an AnxA1 fragment encapsulated within polymeric nanoparticles accelerated recovery following experimentally induced colitis. With its central position during the switch from inflammation to resolution, we hypothesized that AnxA1 may be an important cue linking initial myeloid cell recruitment to myocardial repair.

AnxA1 knockout mice showed a reduced cardiac functionality and an expansion of proinflammatory macrophages in the ischemic area. Cardiac macrophages from AnxA1 knockout mice exhibited a dramatically reduced ability to release the proangiogenic mediator vascular endothelial growth factor (VEGF)-A. However, AnxA1 treatment enhanced VEGF-A release from cardiac macrophages, and its delivery in vivo markedly improved cardiac performance. AnxA1 has a direct action on cardiac macrophage polarization toward a pro-angiogenic, reparative phenotype. AnxA1 stimulated cardiac macrophages to release high amounts of VEGF-A, thus inducing neovascularization and cardiac repair.


Linking the DNA Damage Response and Calcification of Arteries

Researchers here provide evidence for a specific mechanism that can link the oxidative stress of aging with calcification of tissues such as arteries. Calcification reduces elasticity, which in the case of blood vessels contributes to hypertension, but it can also cause serious functional issues in other tissues. Oxidative molecules are generated in increasing numbers in aged tissues, and where their presence outweighs the existing antioxidant defenses over the long term, disruption results. The deeper causes of this oxidative stress include chronic inflammation, such as that produced by senescent cells, and mitochondrial dysfunction. As the example here shows, the consequent disruptions produced by oxidative stress include maladaptive responses in the regulation of cellular behavior.

Biomineralization is the deposition of mineral particles within a proteinaceous organic matrix. In bone, this is an essential physiological process, but extensive pathological calcification of soft tissues, in particular the vasculature, commonly occurs in association with disease. Determining how this complex chemical process is controlled is relevant to both bone development and the treatment of detrimental conditions such as "hardening of the arteries." Despite increased understanding of the cell biological processes involved in biomineralization, the chemical mechanism of mineral nucleation remains elusive.

Studies in vitro have shown that the formation of bone-like ordered mineral deposits around collagen fibrils requires other factors such as additional or substituting mineral ions or non-collagenous biomolecules. This implies that there is cellular control of extracellular matrix (ECM) calcification through the secretion of specific factors, but the identification of these factors remains elusive. In both bone and the vasculature, biomineralization is accompanied by osteogenic differentiation of resident osteoblasts and vascular smooth muscle cells (VSMCs), respectively. Osteogenic differentiation results in increased expression of multifunctional acidic proteins, including the small integrin-binding ligand, N-linked glycoprotein (SIBLING) proteins, and speculation has focused on these "osteogenic" proteins as specialist molecules that may selectively bind calcium ions and provide specificity of interaction with collagen fibrils, these proteins do not have the calcium concentration capacity to induce collagen calcification.

Previously we discovered that poly(ADP-ribose) (PAR) is abundant in the calcifying growth plate of developing fetal bone, which led us to hypothesize that PAR may play a role in biomineralization. PAR is a post-translational modification moiety composed of sugar phosphates that is produced by PAR polymerase (PARP) enzymes and adducted to numerous cellular proteins in a process known as PARylation. Several characteristics of PAR lend support to its possible extracellular role in biomineralization: first, the pyrophosphate groups of PAR are predicted to locally bind calcium ions, potentially to the levels needed for mineral nucleation. Second, PARP1 and PARP2, the dominant PAR-producing enzymes, are expressed in response to DNA damage and oxidative stress, both etiologies associated with vascular calcification. Third, emerging evidence suggests that osteogenic differentiation in calcifying osteoblasts is regulated by PARP activity induced by hydrogen peroxide release from cells. Therefore, we explored whether PAR could control the physicochemical process of mineral formation in the ECM and provide evidence that PAR biosynthesis, induced in part by the cellular DNA damage response (DDR), is a unifying factor in physiological bone and pathological artery calcification.


Cellular Senescence as a Program of the Innate Immune System

The authors of today's open access research offer an interesting viewpoint on cellular senescence in the context of cancer, presenting it as an aspect of the innate immune response to the signs of cancer-inducing mutational damage, or to the signs of cancer suppression programs operating in cells. The objective of the body's numerous, layered defenses against cancer is to destroy all cells that show the signs of becoming cancerous. The first line of defense is the state of cellular senescence, in which cells shut down their ability to replicate, prime themselves to self-destruct via the programmed cell death path of apoptosis, and alert the immune system via a mix of inflammatory secretions known as the senescence-associated secretory phenotype (SASP). These secretions also raise the odds of other surrounding cells becoming senescent, which in theory helps to stay ahead of the replication of an early cancer.

Cellular senescence in this context of cancer is likely an adaptation of an existing tool. Transient cellular senescence occurs during embryonic growth and wound healing, a way to help guide structure and regeneration. That it can also help to shut down early stage cancer has the look of a later development. Unfortunately cellular senescence is an imperfect tool: senescent cells are not reliably removed by the immune system, and they do not reliably self-destruct. Some tiny fraction linger, and their continued inflammatory secretions are an important contributing cause of aging and age-related disease.

In recent years, the research community has found ways to selectively destroy a fraction of the senescent cells present in old tissues. This approach to the treatment of aging reliably extends life span and reverses numerous age-related diseases in mice. Numerous companies are working on ways to destroy senescent cells, and the first therapies are entering human trials. Meanwhile, ever more funding is flowing towards fundamental research into the biochemistry of senescence, as there are likely many more potential approaches to the destruction or management of senescent cells yet to be discovered. This point is illustrated well in the open access paper here, as the authors propose a new point of intervention based on their research.

The innate immune sensor Toll-like receptor 2 controls the senescence-associated secretory phenotype

We describe here an essential innate immune signaling pathway in oncogene-induced senescence (OIS) established between TLR2 and acute-phase serum amyloid A1 and serum amyloid A2 (A-SAAs) that initiates the senescence-associated secretory phenotype (SASP) and reinforce cellular senescence in vitro and in vivo. We also identify new important SASP components, A-SAAs, which are the senescence-associated damage-associated molecular patterns (DAMPs) sensed by TLR2 after oncogenic stress. Therefore, we are reporting that innate immune sensing is critical in senescence. We propose that cellular senescence shares mechanistic features with the activation of innate immune cells and could be considered a program of the innate immune response by which somatic cells switch their regular role to acquire an immune function under certain conditions of stress and danger, for instance, upon oncogene activation.

Besides revealing a role for TLR2 in SASP induction and cell cycle regulation, we identified the DAMP that activates TLR2 in OIS. Acute-phase proteins SAA1 and SAA2 act to prime the TLR2-mediated inflammasome, and in turn, their full induction depends on TLR2 function. Hence, they establish a foundational feedback loop that controls the SASP. A-SAAs are systemically produced in the liver and released into the bloodstream during an acute inflammatory response. Our identification of these molecules as mediators of senescence suggests that systemic elevation of A-SAAs might have an impact on the accumulation of senescent cells and the activation of their proinflammatory program at the organismal level.

We found activation of TLR2 expression in parallel to A-SAAs in models of OIS in mice, in inflammation-induced senescence, in aging, and in different in vitro systems of senescence. Also, we have shown that TLR2 controls the activation of the SASP and OIS in vivo. Moreover, we have observed a dose-dependent effect for TLR2 in A-SAA sensing and a role for TLR2 in SASP activation during paracrine senescence. Together, these data suggest that systemic A-SAA elevation during acute inflammation could affect cells expressing TLR2, thereby promoting aging and other pathological roles of senescence. Further investigation may reveal additional physiological circumstances under which senescence is induced or reinforced by the interaction of TLR2 with A-SAAs or indeed with other endogenous DAMPs or exogenous pathogen-associated molecular patterns (PAMPs) from the microbiome. These circumstances could have implications for organismal well-being, in particular, the development of aging and cancer.

In recent years, several strategies have been implemented to eliminate senescent cells or to modulate the activation of the SASP in anti-aging and cancer therapies (senotherapies). For example, genetic targeting for the elimination of senescent cells can delay organismal aging and aging-associated disorders. Furthermore, the pharmacological suppression of the SASP has been shown to improve homeostasis in tissue damage and aging. However, most of these manipulations are directed to essential homeostatic regulators such as mTOR or crucial proinflammatory mediators such as IL-1 signaling. Here, we propose the alternative of manipulating A-SAA-TLR2 as a new rationale for senotherapies aiming to manipulate nonessential and senescence-specific signaling pathways.

Talking with Laura Deming: Aging is the World's Most Important Problem

Laura Deming is one of the people influential in the sweeping shift of the past few years in research and development of therapies to treat aging, in which rejuvenation biotechnologies such as senolytic therapies finally started the move from the laboratory into startup companies, on the way to the clinic. She founded the first venture fund to specialize in what people are now calling the longevity sector of the biotech industry, somewhat before that longevity sector actually existed in any meaningful way. Now, of course, funding is pouring into this area of development; the years ahead will be interesting. Now is very much the time for entrepreneurs to step up, find viable projects in aging and longevity, raise the funds, and carry them forward into clinical development.

At 25, Laura Deming has already achieved more in her chosen field - anti-ageing - than many people twice her age. At 12 she was researching the biology of ageing in the laboratory of one of the world's leading scientists; at 14 she went to study physics at MIT, only to drop out at 17 and start a venture capital fund under the guidance of Silicon Valley entrepreneur Peter Thiel. Aubrey de Grey, the English gerontologist who has suggested that humans might live to be 1,000, calls Deming an "utter genius" for her scientific and investment "brilliance".

There is a long history of charlatans selling the cure to getting old. However, Deming is no biohacker; she isn't fiddling with diet, exercise, or pills to add an extra year or two to her life. Her ambition is far greater: to accelerate anti-ageing science so that everyone can live healthier lives for longer. To that end, she founded the Longevity Fund in 2011, when she was still a teenager, to invest in biotech companies making treatments for age-related diseases.

When Deming decided to start raising money to get anti-ageing research out of the lab, she was still too young to sign the paperwork - her father had to do it on her behalf. She received some advice from Peter Thiel but confesses that she really did not know what she was doing. "You'd google 'How to start a venture capital fund' and there were just no articles," she says, amazed. For the first two years of the fund, Deming tried to sell investors on the "science and the humanitarian issues at stake". "Honestly, for two years I gave the same pitch of, here's a $20 billion market and here's all the people who are dying, can someone help them? And everyone was like, 'That's amazing, you're such a good person', and nobody invested," she laughs. She learned she needed to link her passion for the cause to a "very concrete business case".

The fund's first investment, in Unity Biotechnology, helped her to do that. Unity is developing a drug that targets senescent cells - decrepit cells that refuse to die. If it works, the drug could be used to treat age-related diseases such as osteoarthritis, eye diseases, and pulmonary diseases. Unity went public last year and now has a valuation of more than $350 million. "Having a concrete case to show potential investors ... that was what brought it together." Deming's biggest fear is the hype cycle: what if a few early anti-ageing trials flop, and the money goes away? "That gives me a lot of fear, because it's a field that is still very early. There's a lot of stuff that's still being figured out, and I think a lot of things will fail."


People Remain Hopeful that Something Useful can be Accomplished with Minoxidil

Minoxidil is, of course, the well known basis for certain popular hair growth products. That outcome was an accident, however, as the compound originally entered clinical trials - some 30 years ago - as a possible treatment for hypertension, or chronic raised blood pressure. The primary mechanism of interest is that minoxidil spurs greater deposition of elastin in blood vessel walls and other tissues, thereby reversing a fraction of the progressive loss of elastin that takes place over the course of aging.

Elastin, as one might guess from the name, is a component of the extracellular matrix responsible for the elasticity exhibited by tissues such as skin and blood vessels. Hypertension is caused by the age-related stiffening of blood vessels, which leads to a dysregulation of pressure control systems in our biochemistry. This then speeds up the progression of atherosclerosis and heart failure, and in addition produces an accelerated rate of capillary rupture and consequent damage in delicate tissues such as the brain and kidney. It is a very import aspect of age-related degeneration.

It is interesting to see researchers still working on minoxidil. The original clinical trials for hypertension, while leading to an approved drug, showed that minoxidil causes edema around the heart at useful doses for the elastin deposition effect, a potentially severe consequence. For me, that is more than enough to reconsider its use in this way. During the early studies and trials, hair growth in the patients was noted, and the rest of the development program thereafter is history. It is possible that now, with a far greater ability to take a small molecule as a starting point and build different versions with different characteristics, it is plausible to build a minoxidil analog that doesn't have the serious side-effects at usefully high doses, where that was simply not possible in earlier decades. We shall see.

Arterial wall elastic fibers, made of 90% elastin, are arranged into elastic lamellae which are responsible for the resilience and elastic properties of the large arteries (aorta and its proximal branches). Elastin is synthesized only in early life and adolescence mainly by the vascular smooth muscle cells (VSMC) through the cross-linking of its soluble precursor, tropoelastin. In normal aging, the elastic fibers become fragmented and the mechanical load is transferred to collagen fibers, which are 100-1000 times stiffer than elastic fibers.

Minoxidil, an ATP-dependent K+ channel opener, has been shown to stimulate elastin expression in vitro and in vivo in the aorta of young adult hypertensive rats. Here, we have studied the effect of a 3-month chronic oral treatment with minoxidil (120 mg/L in drinking water) on the abdominal aorta structure and function in adult (6-month-old) and aged (24-month-old) male and female mice. Our results show that minoxidil treatment preserves elastic lamellae integrity, which is accompanied by the formation of newly synthesized elastic fibers in aged mice. This led to a generally decreased pulse pressure and a significant improvement of the arterial biomechanical properties in female mice, which present an increased distensibility and a decreased rigidity of the aorta. Our studies show that minoxidil treatment reversed some of the major adverse effects of arterial aging in mice and could be an interesting anti-arterial aging agent, also potentially usable for young female-targeted therapies.


Declining Microcirculation as an Important Aspect of Aging

Tissues are supported by dense and intricate networks of capillaries, hundreds passing through any square millimeter cross-section. Many studies have shown that capillary density decreases with age, which is perhaps another of the many results of faltering tissue maintenance due to the decline in stem cell activity, or alternatively, a specific dysregulation of the processes of angiogenesis at the small scale, resulting from inappropriate cellular reactions to rising levels of damage and chronic inflammation. Fewer capillaries means a lesser delivery of nutrients and oxygen, and we might well wonder to what degree this contributes to atrophy and dysfunction in energy hungry tissues such as muscles and the brain.

In this context, consider of the loss of muscle mass and strength that occurs with aging, known as sarcopenia. While sarcopenia is associated with a long, long list of potential contributing mechanisms, arguably the best evidence suggests that this loss of muscle capacity is caused by the declining activity of muscle stem cell populations. This connects well with a decline in capillary density, in that we can theorize either side as cause or consequence of the other. Another possible contributing factor is age-related mitochondrial dysfunction. Given that mitochondria are the power plants of the cell, responsible for transforming energy from nutrients into a form that cells can use, here too the possible connections to declining capillary density are obvious.

The two different approaches to this challenge are quite different. On the one hand, the first and more mainstream approach would be to attempt to override changes in the regulation of angiogenesis, forcing different expression levels in various regulatory proteins in order to generate greater generation of blood vessels. This strategy can produce benefits, but because it fails to address the underlying causes, the benefits are necessarily limited. The damage of aging marches on, causing all of its other consequences. One might look at past efforts to control raised blood pressure or chronic inflammation to see the plausible beneficial outcomes that can emerge from tackling important facets of aging in ways that do not repair the causes. The second, and as yet less popular - but better! - approach is to repair the damage that causes aging, and thus remove the dysregulation in angiogenesis and tissue maintenance that way. Sadly, this path forward is nowhere near as popular and well funded as it should be.

A Microcirculatory Theory of Aging

The term "microcirculation" in contrast with macrocirculation (which is the flow of blood to and from organs), refers to a network of terminal vessels comprising arterioles, capillaries and venules that are less than 100 μm in diameter. In other words, the microcirculation is defined as the blood flow through the smallest vessels in the vasculature and are embedded within organs and tissues, which facilitate the exchange of biological material between the blood and tissue via its large surface area and low blood velocity in these regions. For organs to function well, there must be sufficient perfusion throughout the tissue in the form of intact and appropriate microcirculatory vascularization.

There is a substantial number of studies presenting strong evidence of decreased vessel density with age, indicating an age-associated failure of vascular recovery in organs such as the brain in animals and humans alike. In studies involving aged rodents: healthy senescent rats (29 months) experienced a loss of about 40% of arteriolar density on the cortical surface compared with young adult rats (13 months). In the hippocampus of aged rats, there was a 20% decrease in capillary number, 3% decrease in capillary length, and 24% increase in intercapillary distance. Comparable reductions could also be found in other brain regions including the brain stem, cortex, and white matter. In studies involving aged humans: Capillary density decreased by 16% in the calcarine cortex while vascular density decreased by 50% in the paraventricular nucleus, frontal cortex, and putamen. Importantly, angiogenesis has been found to be impaired in aged tissues, which could contribute to the significant decreases in vascular density and number that has been reported.

Factors of vascular aging are reported to be closely associated with chronological age. Indeed, alterations in vascular mechanics and structure are related with vascular aging, resulting in less elastic arteries and diminished arterial compliance. Furthermore, the increased diffusion distance for oxygen caused by reduced capillary numbers and density, gives rise to heterogeneous perfusion, where the close proximity of perfused capillaries and non-perfused capillaries triggers alterations to oxygen extraction even when blood flow to the tissue is conserved.

Under normal physiological conditions, the microcirculatory blood flow is adapted to the metabolic levels of human tissues and organs, so the physiological functions of various organs in the human body can function as they should. Once the microcirculation of the human body is impaired, cells would not be able to get enough nutrition and oxygen, and meanwhile, CO2 and metabolic products, including those that are toxic, cannot be removed and will accumulate. Consequently, deterioration of physiological functions of cells and then organs that are necessary for survival and reproduction will occur. Microcirculatory impairment arises in adulthood and becomes progressively impaired with aging; the corresponding tissue system or internal organs are affected and unable to function normally, which eventually lead to aging. Therefore, aging is the process of continuous impairment of microcirculation in the body.

The Contribution of Reactive Astrocytes to Neurodegeneration

Neurodegenerative diseases have a strong inflammatory component, the dysregulation of the immune system in the brain, with consequences to tissue function. In the process of astrogliosis, the supporting cells known as astrocytes react to damaging or inflammatory circumstances, and radically change their behavior. This can help in the short term for some forms of injury to the central nervous system, but is harmful when it continues for the long term. Like microglia, another supporting cell type, astrocytes can adopt different packages of behaviors, or phenotypes, and switch back and forth between them in response to circumstances. The primary distinction of interest in these is between (a) a supportive, regenerative phenotype, and (b) an aggressive, inflammatory phenotype. The latter tends to show up ever more often as aging progresses, and this imbalance is the cause of further harms.

Astrocytes are the most abundant cells with various structures and functions and are ubiquitous in all regions of the central nervous system (CNS). Astrocytes are associated with various aspects of physiological functions, including secretion of nutrients, maintenance of neuronal microenvironment, regulation of the permeability of the blood-brain barrier and the development of pathological processes in the brain. Studies on mouse models have shown that astrocytes play a complex role in the pathogenesis of neurodegenerative diseases, and the dysfunction of astrocytes may contribute to either neuronal death or the process of neural disturbances. It has been found that reactive astrocytes always lose their supportive role and gain toxic function in the progression of neurodegenerative diseases.

During brain insult or neurodegeneration process, astrocytes can respond to pathological changes by releasing extracellular molecules, such as neurotrophic factors (for example BDNF, VEGF, and bFGF), inflammatory factors (including IL-1β, TNF-α, and NO, etc.) and cytotoxins (such as Lcn2) through reactive astrogliosis. As a result, they play either a neuroprotective or neurotoxic role (such as provoking inflammation or increasing damages) in the CNS. It has been shown that the specific deletion of STAT3 in astrocytes can cause reactive gliosis, which leads to increased level of inflammation, tissue damage as well as compromised motor recovery after spinal cord injury. Interestingly, some studies have shown that the activation of NF-κB in astrocytes contributes to the pathogenesis of CNS, and inhibition of this signaling pathway can limit tissue damage.

These findings suggest that astrocytes may play a protective role through STAT3 signaling pathways in some neurodegenerative lesions, while NF-κB signals may mediate neurotoxicity. In analogy to the "M1" and "M2" phenotype categories for macrophages, recent studies have reported that neural inflammation and ischemia can induce two types of reactive astrocytes, termed "A1" and "A2", respectively. Gene transcriptome analysis of reactive astrocytes shows that A1 reactive astrocytes (A1s) can upregulate many classical complement cascade genes that are destructive to synapses, and secret neurotoxins that have not yet been well identified. In contrast, A2 reactive astrocytes (A2s) can upregulate many neurotrophic factors, which can promote either the survival and growth of neurons or the synaptic repair. Thus, A1s may have "harmful" features, while A2s may carry "useful" or repair functions. So far, it remains unclear what the possible signaling pathways have been involved in inducing the phenotypes of A1s and A2s in the process of different initiating CNS injuries.


Towards Bioprinted Corneas

While no tissues can be said to be simple, some are simpler than others. In the past decade, tissue engineers have made considerable progress towards the manufacture of these simpler tissues, from the starting point of cells and scaffold materials. Bioprinting, a form of rapid prototyping, has proven to be an important class of approach. The research noted here is a representative example of progress towards the production of corneas to replace those that are damaged by accident or age, and thus eliminate the need for donor tissue.

When a person has a severely damaged cornea, a corneal transplant is required. For this reason, many scientists have put their efforts in developing an artificial cornea. The existing artificial cornea uses recombinant collagen or is made of chemical substances such as synthetic polymer. Therefore, it does not incorporate well with the eye or is not transparent after the cornea implant. Now, researchers have 3D printed an artificial cornea using the bioink which is made of decellularized corneal stroma and stem cells. Because this cornea is made of corneal tissue-derived bioink, it is biocompatible, and 3D cell printing technology recapitulates the corneal microenvironment, therefore, its transparency is similar to the human cornea.

The human cornea is organized in a lattice pattern of collagen fibrils. The lattice pattern in the cornea is directly associated with the transparency of cornea, and many researches have tried to replicate the human cornea. However, there was a limitation in applying to corneal transplantation due to the use of cytotoxic substances in the body, their insufficient corneal features including low transparency, and so on. To solve this problem, the research team used shear stress generated in the 3D printing to manufacture the corneal lattice pattern and demonstrated that the cornea by using a corneal stroma-derived decellularized extracellular matrix bioink was biocompatible.

In the 3D printing process, when ink in the printer comes out through a nozzle and passes through the nozzle, frictional force produces shear stress. The research team successfully produced transparent artificial cornea with the lattice pattern of human cornea by regulating the shear stress to control the pattern of collagen fibrils. The research team also observed that the collagen fibrils remodeled along with the printing path create a lattice pattern similar to the structure of native human cornea after 4 weeks in vivo.


Understanding Why the Immune System Fails to Destroy Lingering Senescent Cells May Lead to New Senolytic Therapies

The accumulation of lingering senescent cells in all tissues is one of the causes of aging. Even in very late life, senescent cells are thought to account for only a few percent at most of all cells in any given tissue, but they cause great disruption to tissue structure and function: chronic inflammation, impaired regeneration, fibrosis, and other unpleasant outcomes. This is accomplished via an as yet incompletely cataloged mix of secreted molecules known as the senescence-associated secretory phenotype, or SASP. Acting via secretions allows a small number of cells to have large effects.

When present for a limited period of time, senescent cells are helpful, a necessary part of wound healing, embryonic development, and suppression of cancer. Cells become senescent in response to the circumstance, the SASP assists in calling in the immune system to help, or in spurring growth, or in instructing nearby cells to also become senescent. Then the senescent cells self-destruct or are destroyed by the immune system once their contribution to the task at hand is complete. It is only when senescent cells linger for the long term that the SASP becomes dangerous, corrosive to tissue function.

Why do some senescent cells fail to self-destruct? Further, while we know that the immune system declines with age, becoming less effective in all of its tasks, why specifically do immune cells fail to identify and destroy some senescent cells? Progress towards more complete and detailed answers these questions may open the door to new classes of senolytic therapy, capable of purging senescent cells from old tissues. While a variety of senolytic treatments are either available or under development, none are capable of destroying more than about half at best of these cells, and then only in some tissues. Combinations of different therapies, and more efficient therapies will be needed in the years ahead.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition

Cellular senescence is an evolutionarily conserved mechanism with beneficial effects on tumour suppression, wound healing and tissue regeneration. During ageing, however, senescent cells accumulate in tissues and manifest deleterious effects, as they secrete numerous pro-inflammatory mediators as part of a senescence-associated secretory phenotype (SASP). The elimination of senescent cells in mouse models was shown sufficient to delay the onset or severity of several age-related phenotypes. This has prompted the development of senolytic drugs that selectively target senescent cells. Despite successful reversal of age-related pathologies in animal models, the use of senolytic drugs in humans may be hampered by their lack of specificity for senescent cells, leading to the risk of toxicity. Therefore, alternative approaches that can be used in isolation or in combination with senolytic drugs to improve the elimination of senescent cells in humans should be explored.

Senescent cells can be recognised and eliminated by the immune system. Different immune cell types including macrophages, neutrophils, natural killer (NK) cells and CD4+ T cells have been implicated in the surveillance of senescent cells, depending on the pathophysiological contex. Senescent cells become immunogenic by expressing stimulatory ligands like MICA/MICB that bind to NKG2D and activate their killing by NK cells. Moreover, by secreting chemokines and cytokines, senescent cells can recruit immune cells into tissues that enable senescent cell clearance. However, this secretory process may perpetuate a low-level chronic inflammatory state that underlies many age-related diseases.

Despite the evidence for senescent cell clearance by the immune system, it is not yet clear why senescent cells accumulate during ageing and persist at sites of age-related pathologies. A decline in immune function may contribute to incomplete elimination of senescent cells with age. Ageing has a great impact in both innate and adaptive immune systems, a process known as immunosenescence. Alternatively, changes in major histocompatibility complex (MHC) expression can lead to escape from recognition by the immune system as previously described in cancer and virally infected cells in vivo. Nevertheless, the effects of senescence on MHC expression are not fully understood.

Here, we show that senescent primary human dermal fibroblasts express increased levels of the non-classical MHC-class Ib molecule HLA-E. HLA-E inhibits immune responses against senescent cells by interacting with the inhibitory receptor NKG2A expressed on NK and highly differentiated CD8+ T cells. Accordingly, we find an increased frequency of HLA-E expressing senescent cells in the skin of old compared with young subjects. HLA-E expression is induced by SASP-related pro-inflammatory cytokines, in particular IL-6 and regulated by p38 signalling in vitro. Lastly, we show that that blocking HLA-E/NKG2A interactions in cell culture enhances NK and CD8+ T cell-mediated cytotoxicity against senescent cells. Taken together, these findings suggest that HLA-E expression contributes to the persistence of senescent cells in tissues. HLA-E may therefore represent a novel target for the therapeutic elimination of senescent cells in age-related diseases.

Cellular Antioxidant Defenses Measured in Blood Samples Decline with Age

Cells are in a constant state of generating oxidative molecules, clearing those molecules via the use of antioxidant proteins, and repairing the damage caused by oxidative reactions. Researchers here show that aging is accompanied by declining amounts of the natural antioxidants involved in clearing oxidizing molecules from cells, preventing them from reacting with cellular machinery to cause damage. This is an unfortunate downstream consequence of the underlying causes of aging, one that will cause further dysfunction in cells. Exactly how and why this is a feature of aging, the exact chain of cause and effect that leads from the underlying damage to this result, remains to be determined. At the present time, the fastest approach to answering that sort of inquiry is likely to build rejuvenation biotechnologies that can repair specific forms of molecular damage thought to cause aging, and then see what happens when the therapies are applied in animal studies.

An integral part of aerobic metabolism is reactive oxygen species (ROS) generation which should be analyzed according to its two main functions. On the one hand, ROS plays an important role in biomodulating and regulating many cellular functions, such as defense against pathogens, signal transduction processes during transmission of intercellular information, and activation of specific transcription factors. On the other hand, an excessive quantity of ROS has a deleterious effect on cells, reacting with a variety of molecules and thereby interfering with cellular functions. To cope with the elevated generation of ROS, ROS-scavenging biochemical pathways have been developed in aerobic cells.

In recent years there have been a lot of studies supporting the role of ROS in molecular aging mechanisms. The confirmation of oxidative stress increase with age of diverse organisms, and the generation of transgenic invertebrates overexpressing the antioxidant enzymes with increased lifespan were among the most important results of these studies. Nevertheless, there were no alterations in the lifespan in most of the examined mouse models, which under- or overexpressed a wide variety of genes coding for antioxidant enzymes. Thus, the role of oxidative stress in aging mammals is not fully understood and still demands further inquiries.

In this study, analysis of antioxidant defense was performed on the blood samples from 184 "aged" individuals aged 65-90+ years, and compared to the blood samples of 37 individuals just about at the beginning of aging, aged 55-59 years. Statistically significant decreases of Zn,Cu-superoxide dismutase (SOD-1), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were observed in elderly people in comparison with the control group. Moreover, an inverse correlation between the activities of SOD-1, CAT, and GSH-Px and the age of the examined persons was found. No age-related changes in glutathione reductase activities and malondialdehyde concentrations were observed. These lower activities of fundamental antioxidant enzymes indicate the impairment of antioxidant defense in the erythrocytes of elderly people.


Extremely Long Lived Cells are Found in Many Tissues, Not Just the Brain

Researchers here report that the brain is not the only organ to exhibit cells that are as long-lived as the animal containing them. A number of other organs contain at least some long-lived cells, even for tissues thought to be highly regenerative and in which tissue turnover is comparatively rapid, such as the liver. It remains to be seen as to how this new information interacts with present thinking on the damage of aging, in which there is a central role for a reduction in stem cell activity and consequent loss of new cells generated to replace old tissue populations.

Scientists once thought that neurons, or possibly heart cells, were the oldest cells in the body. Now, researchers have discovered that the mouse brain, liver, and pancreas contain populations of cells and proteins with extremely long lifespans - some as old as neurons. "We were quite surprised to find cellular structures that are essentially as old as the organism they reside in. This suggests even greater cellular complexity than we previously imagined and has intriguing implications for how we think about the aging of organs, such as the brain, heart, and pancreas."

Since the researchers knew that most neurons are not replaced during the lifespan, they used them as an "age baseline" to compare other non-dividing cells. The team combined electron isotope labeling with a hybrid imaging method (MIMS-EM) to visualize and quantify cell and protein age and turnover in the brain, pancreas and liver in young and old rodent models. To validate their method, the scientists first determined the age of the neurons, and found that - as suspected - they were as old as the organism. Yet, surprisingly, the cells that line blood vessels, called endothelial cells, were also as old as neurons. This means that some non-neuronal cells do not replicate or replace themselves throughout the lifespan.

The pancreas, an organ responsible for maintaining blood sugar levels and secreting digestive enzymes, also showed cells of varying ages. A small portion of the pancreas, known as the islets of Langerhans, appeared to the researchers as a puzzle of interconnected young and old cells. Some beta cells, which release insulin, replicated throughout the lifetime and were relatively young, while some did not divide and were long-lived, similar to neurons. Yet another type of cell, called delta cells, did not divide at all. The pancreas was a striking example of age mosaicism, i.e., a population of identical cells that are distinguished by their lifespans.

Prior studies have suggested that the liver has the capacity to regenerate during adulthood, so the researchers selected this organ expecting to observe relatively young liver cells. To their surprise, the vast majority of liver cells in healthy adult mice were found to be as old as the animal, while cells that line blood vessels, and stellate-like cells, another liver cell type, were much shorter lived. Thus, unexpectedly, the liver also demonstrated age mosaicism.


Lymph Node Organoids Integrate into the Lymphatic System and Restore Function

The lymphatic system is vital to the correct operation of the immune response: lymph nodes are where immune cells communicate with one another in order to direct the response to invading pathogens and other threats. Unfortunately lymph nodes deteriorate with age, becoming inflammatory and fibrotic, no longer able to host the necessary passage and communication of immune cells. Researchers have demonstrated that, at least in late life, this can prevent improvements elsewhere in the aged immune system from producing the expected benefits in the immune response. What use extra immune cells or better immune cells if those cells cannot coordinate correctly? There are signs that lymph node degeneration may be due in part to the presence of senescent cells, in which case we might hope that senolytic therapies will help, but this has yet to be assessed by the research community.

What if new lymph nodes can be provided, however? Today's open access paper is a report on the generation and transplantation of organoids capable of functioning as lymph nodes. In mice, transplanted organoids can integrate with the lymphatic system and begin to perform the duties of lymph nodes. While these were not aged mice, and the transplanted organoids replaced lymph nodes that had been surgically removed, rather than augmenting those damaged by aging, this is still promising. This line of research could become one of the suite of approaches that will needed to restore the immune system of an older individual to full, youthful function.

The other necessary therapies for immune rejuvenation are: regrowth of the thymus, responsible for maturation of T cells of the adaptive immune system, and which atrophies with age; rejuvenation of the hematopoietic stem cell population in the bone marrow, source of all immune cells, and damaged and diminished in older individuals; and clearance of the senescent, exhausted, misconfigured, and otherwise broken or inappropriate immune cells that come to clutter up the immune system in late life. A few different approaches for each of these line items are at various stages of development. Given a the timescale of a decade or two we should be optimistic that the effects of aging on the immune system can be significantly reversed.

Therapeutic Regeneration of Lymphatic and Immune Cell Functions upon Lympho-organoid Transplantation

Lymph node (LN) development is a multistep process involving crosstalk of multiple cell types and culminating in integration of LNs into the lymphatic system. Non-hematopoietic stromal progenitors of lymphoid organs play critical roles in tissue development, organization, and function through the secretion of cytokines, chemokines, and the extracellular matrix (ECM), a tri-dimensional scaffold that provides structural support and anchorage for cells. Afferent-collecting lymphatics transport lymph and antigens to the LN where immune responses are generated. However, surgical resection of LNs, radiation therapy, or infections may damage the lymphatic vasculature and contribute to secondary lymphedema, a chronic disease characterized by excessive tissue swelling, fibrosis, and decreased immune responses.

Currently available lymphedema treatments are limited to manual lymph drainage and compression garments, and definitive therapeutic options are still lacking. Vascularized autologous lymph node transfer (ALNT), a surgical procedure in which a LN flap is harvested and transplanted at the site of resected LNs to improve lymphatic drainage, is emerging as a therapeutic option for the treatment of cancer-associated lymphedema. Although feasible, such an approach requires surgical intervention and can be associated with donor-site complications, which may limit its application.

To circumvent these problems, tissue engineering may provide strategies to develop artificial lymphoid tissues for applications in regenerative medicine. It has been demonstrated that transplantation under the kidney capsule of an engineered stromal cell line expressing lymphotoxin α in a biocompatible scaffold or the delivery of stromal-derived chemokines in hydrogel is sufficient to promote the organization of lymphoid-like structures with immunological function. Whether these approaches contribute to regenerate immune and lymphatic functions in preclinical models of LN resection remains unknown.

Here, we generated lympho-organoids (LOs) using LN stromal progenitors in an ECM-based scaffold and show that LO transplantation at the site of resected LN contributes to restoration of lymphatic and immune functions. Upon transplantation, LOs are integrated into the endogenous lymphatic vasculature and efficiently restore lymphatic drainage and perfusion. Notably, upon immunization, LOs support the activation of antigen-specific immune responses and acquire properties of native lymphoid tissues. These findings provide a robust preclinical approach for the development of synthetic LOs capable of regenerating lymphatic and immune functions.

A Natural Mechanism that Breaks Down α-Synuclein Aggregates

The brain exhibits a range of natural mechanisms for the clearance of various protein aggregates involved in neurodegenerative disease, both inside and outside the cells: clearance via immune cells; autophagy within cells; carried away via drainage of cerebrospinal fluid; and so forth. Clearly these mechanisms falter and become overwhelmed with advancing age, an outcome that results from a progressively increased burden of cell and tissue damage. Where a natural repair and maintenance mechanism exists, looking for ways to enhance that mechanism is one of the logical places to make a start on the development of viable therapies.

Aggregates of the protein alpha-synuclein in the nerve cells of the brain play a key role in Parkinson's and other neurodegenerative diseases. These protein clumps can travel from nerve cell to nerve cell, causing the disease to progress. Relevant for these diseases are long but yet microscopic fibres, or fibrils, to which large numbers of the alpha-synuclein molecules can aggregate. Individual, non-aggregated alpha-synuclein molecules, however, are key to the functioning of a healthy brain, as this protein plays a key role in the release of the neurotransmitter dopamine in nerve cell synapses.

When the protein aggregates into fibrils in a person's nerve cells - before which it must first change its three-dimensional shape - it can no longer carry out its normal function. The fibrils are also toxic to the nerve cells. In turn, dopamine-producing cells die, leaving the brain undersupplied with dopamine, which leads to typical Parkinson's clinical symptoms such as muscle tremors. "Once the fibrils enter a new cell, they 'recruit' other alpha-synuclein molecules there, which then change their shape and aggregate together. This is how the fibrils are thought to infect cells one by one and, over time, take over entire regions of the brain."

Researchers were able to decipher a cellular mechanism that breaks down alpha-synuclein fibrils naturally. A protein complex called SCF detects the alpha-synuclein fibrils specifically and targets them to a known cellular breakdown mechanism. In this way, the spread of fibrils is blocked, as the researchers demonstrated in tests on mice: when the researchers switched off SCF's function, the alpha-synuclein fibrils were no longer cleared up in the nerve cells. Instead, they accumulated in the cells and spread throughout the brain.

The more active the SCF complex, the more the alpha-synuclein fibrils are cleared, which could slow down or eventually stop the progression of such neurodegenerative diseases. The SCF complex is very short-lived, dissipating within minutes. Therapeutic approaches would focus on stabilising the complex and increasing its ability to interact with alpha-synuclein fibrils. For example, drugs could be developed for this purpose. "However, when it comes to potential therapies, we're still right at the beginning. whether effective therapies can be developed is still unclear."


Mast Cells in Age-Related Neurodegeneration and Neuroinflammation

Of late, it is becoming clear that the dysfunction of immune cells of the central nervous system, such as microglia, is an important part of neurodegeneration. Growing degrees of cellular senescence in these cell populations, leading to inflammatory signaling, appears to be significant in the progression of Alzheimer's disease, for example. There are many distinct types of supporting cell in the brain, however. This short open access review paper discusses the evidence for dysfunction of the immune cells known as mast cells to be relevant to the progression of chronic inflammation and neurodegeneration in the aging brain.

Mast cells are "first responders" that become activated with exposure to a diverse array of stimuli, from allergens and antigens to neuropeptides, trauma, and drugs. Activated mast cells are multifunctional effector cells that exert a variety of both immediate and delayed actions.

Neuroinflammation, which is now recognized as a primary pathological component of diseases such as multiple sclerosis, is gaining acceptance as an underlying component of most, if not all, neurodegenerative diseases. Whereas past focus has predominantly centered on glial cells of the central nervous system, recently mast cells have emerged as potential key players in both neuroinflammation and neurodegenerative diseases. Mast cells are well positioned for such a role owing to their ability to affect both their microenvironment and neighboring cells including T cells, astrocytes, microglia, and neurons. The secretory granules of mast cells contain an arsenal of preformed/stored immunomodulators, neuromodulators, proteases, amines, and growth factors that enable complex cross-communication, which can be both unidirectional and bidirectional. Mast cells can also affect disruption/permeabilization of the blood-brain barrier and this has the potential for dramatically altering the neuroinflammatory state.

With respect to Alzheimer's disease (AD), Parkinson's disease (PD), ALS, and Huntington's disease (HD), mast cell perturbation of the blood-brain barrier appears to share a commonality. Moreover, mast cells have been found to home to sites of amyloid deposition in AD; and, an inhibitor of mast cell function was shown to reduce cognitive decline in AD patients. Mast cell interactions with neurons and glial cells have also been implicated in PD pathogenesis. Emerging evidence suggests that mast cell autocrine signaling may contribute to ALS: The mast cell chemoattractant, IL-15, is elevated in the serum and cerebrospinal fluid of ALS patients; and, mast cells expressing IL-17 have been found in the spinal cord of ALS patients. Plasma levels of cytokines (IL-6, IL-8), known to affect mast cell activation, have been correlated with functional scores in HD patients suggesting the possible involvement of mast cells in the pathogenesis of HD.


Progerin Acts in Normal Aging as well as Progeria, but is it Important?

Hutchinson-Gilford Progeria Syndrome, or just progeria, results from the production of a broken protein progerin from the Lamin A gene. The functional form of Lamin A is vital to the structure of cells, and without it cellular damage and tissue dysfunction rapidly accrue. This results in a short lifespan with a superficial resemblance to accelerated aging. It is not accelerated aging, however: aging is a specific mix of forms of cell tissue damage and consequent dysfunction, and progeria is a radically different mix. Where there are similar outcomes, it is because some tissues will tend to fail in similar ways regardless of the specific cause of underlying cellular dysfunction.

While progeria results from the rare occurrence of mutation in the Lamin A gene, in recent years the presence of progerin at low levels has been observed in old individuals undergoing normal aging. This appears to be associated with cellular senescence, with progerin production being, for reasons yet to be fully understood, a feature of senescent cells. Even in very late life only a small fraction of cells in any given tissue are senescent, accounting for the overall low level of progerin, but senescent cells inflict an outsized level of harm on tissue function via a potent inflammatory mix of secreted proteins.

When we ask whether progerin is important in natural aging, this may just boil down to whether or not it is doing anything beyond participating in some way in the biochemistry of senescent cells. If it is just another portion of the internal mechanisms of cellular senescence, then it will not be necessary to tackle it as a distinct mechanism. The dominant approach to senescent cells in aged tissue is to selectively destroy them: no more senescent cells, no more progerin. Alternatively, are normal cells in aged tissues falling into a state in which they produce enough progerin in order to become senescent? Even in this case we may still be able to ignore this mechanism for practical purposes, given efficient enough senolytic treatments to clear out senescent cells every so often.

Are There Common Mechanisms Between the Hutchinson-Gilford Progeria Syndrome and Natural Aging?

The Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disease caused by mutations of the LMNA gene leading to increased production of a partially processed form of the protein lamin A - progerin. Progerin acts as a dominant factor that leads to multiple morphological anomalies of cell nuclei and disturbances in heterochromatin organization, mitosis, DNA replication and repair, and gene transcription.

Progerin-positive cells are present in primary fibroblast cultures obtained from the skin of normal donors at advanced ages. These cells display HGPS-like defects in nuclear morphology, decreased H3K9me3 and HP1, and increased histone H2AX phosphorylation marks of the DNA damage loci. Inhibition of progerin production in cells of aged non-HGPS donors in vivo increases the proliferative activity, H3K9me3, and HP1, and decreases the senescence markers p21, IGFBP3, and GADD45B to the levels of young donor cells. Thus, progerin-dependent mechanisms act in natural aging. Excessive activity of the same mechanisms may well be the cause of premature aging in HGPS.

Telomere attrition is widely regarded to be one of the primary hallmarks of aging. Progerin expression in normal human fibroblasts accelerates the loss of telomeres. Changes in lamina organization may directly affect telomere attrition resulting in accelerated replicative senescence and progeroid phenotypes. The chronological aging in normal individuals and the premature aging in HGPS patients are mediated by similar changes in the activity of signaling pathways, including downregulation of DNA repair and chromatin organization, and upregulation of ERK, mTOR, GH-IGF1, MAPK, TGFβ, and mitochondrial dysfunction. Multiple epigenetic changes are common to premature aging in HGPS and natural aging. Recent studies showed that epigenetic systems could play an active role as drivers of both forms of aging. It may be suggested that these systems translate the effects of various internal and external factors into universal molecular hallmarks, largely common between natural and accelerated forms of aging.

Drugs acting at both natural aging and HGPS are likely to exist. For example, vitamin D3 reduces the progerin production and alleviates most HGPS features, and also slows down epigenetic aging in overweight and obese non-HGPS individuals with suboptimal vitamin D status.

Reviewing the Biochemistry of Survival in Senescent Cells

Now that senescent cells are conclusively demonstrated to be highly influential in the progression of degenerative aging, and broad reversal of aspects of aging is regularly demonstrated in mice via the use of various senolytic therapies, there is considerably more interest and funding in the research community for investigations of the fundamental biochemistry of senescent cells. Senescent cells are generated constantly in all tissues, and are primed for self-destruction via apoptosis. The vast majority either self-destruct or are destroyed by the immune system, quite soon after their creation. Those that linger in tissues to cause aging and age-related disease are in some way resistant to apoptosis, and the mechanisms involved in that resistance are of great relevance to the development of future senolytic therapies, treatments capable of selectively destroying senescent cells.

Increasing evidence suggests that senescent cells are primed to apoptosis due to unresolved chronic stresses, and this might favor the efficacy of known senolytic drugs. In oncology, two-step therapeutic strategies aim to first induce cancer cells into senescence via cytotoxic drugs and then to exploit the vulnerability of senescent cancer cells to apoptosis by using senolytics. However, given the deleterious roles of senescent cells, and the negative systemic side effects associated to chemotherapy, these strategies should be best approached with caution. Recently, the use of genetic screens and compound libraries has yielded aurora kinase inhibitors as powerful inducers of senescence in cancer cells (independent of p53). Importantly, senescent cancer cells also acquired vulnerability to the anti-apoptotic Bcl-2 inhibitor ABT-263 regardless of how senescence was induced. Further research is needed to assess the effects of aurora kinase inhibition in normal cells, as opposed to chemotherapy, in combination with senolytic drugs.

Redundant mechanisms aid cell death prevention in both senescent and cancer cells, as observed with anti-apoptotic Bcl-2 family homologs. Nevertheless, as senescent cells may rely more on anti-apoptotic players compared to normal cells that are free of intracellular stressors, targeting anti-apoptotic players may still represent a viable therapeutic strategy. Moreover, different apoptotic mechanisms exist across different cell types and senescent programs, and these differences may be exploited to allow preferential elimination of a specific subtype of senescent cells. In this respect, targeting a defined senescent subtype that is relevant to a specific pathology may be more desirable and with less side effects than simultaneously targeting all types of senescent cells.

It is important to note that senescent cells rely on multiple levels of regulation in order to achieve apoptosis resistance. The concurrent targeting of multiple and indirectly related anti-apoptotic pathways (SCAPs) may therefore result in increased sensitivity of senescent cells without incurring in toxicities for normal proliferating or quiescent cells. A combinatorial approach to senescent cell clearance is exemplified by the concomitant treatment of dasatinib and quercetin. Targeting SCAP networks, as opposed to single targets, may enable lowering the therapeutic dosage of each drug, therefore decreasing off- and on-target side effects associated to single drugs.

Despite an increased resistance to certain apoptotic stimuli, senescent cells may be more susceptible to various forms of metabolic targeting. Senescent cell hypercatabolism can be pharmacologically exploited for the elimination of senescent cells by means of synthetic lethal approaches such as glycolysis inhibition, autophagy inhibition, and mitochondrial targeting. Synthetic lethal metabolic targeting could therefore be used alone or in combination with SCAP inhibitors for increased selectivity.

Finally, additional strategies alternative to apoptosis induction may be employed to alleviate the deleterious phenotypes associated to senescent cells. For instance, the use of SASP modulators may prevent the establishment of a chronic SASP and dampen the negative side-effects of senescent cell persistence without the need for their removal from tissues. Similarly, the use of selective inhibitors for specific SASP components, such as neutralizing antibodies, may allow a tailoring of the SASP by only targeting SASP components thought to play a negative role in the tissue micro-environment while preserving the beneficial ones. Lastly, enhancing the natural clearance of senescent cells by the immune system could be another way of overcoming apoptosis resistance. The use of immune modulators or artificially increasing the number of immune effector cells may effectively restore senescence surveillance, and decrease the senescent cell burden.


Blocking Translation of α-synuclein RNA to Treat Parkinson's Disease

Parkinson's disease is a synucleinopathy, meaning that its pathology, the damage done to the brain, is driven at least in part by the aggregation of α-synuclein. Effective means to clear out α-synuclein and other protein aggregates from the aging brain, such as those resulting from amyloid-β and tau, are likely to form the basis of the first truly effective treatments for a range of neurodegenerative conditions. Though, as the Alzheimer's research community has demonstrated over the past twenty years, this is easier said than done. Little more than vast expense and failed human trials have thus far resulted from the development of immunotherapies to target the removal of amyloid-β. Success is elusive in that part of the field. Now, however, the research community is diversifying its efforts, with many groups seeking radically different approaches to the challenge of protein aggregation. Some will eventually succeed.

The exact cause of Parkinson's disease (PD) is still a mystery, but researchers believe that both genetics and the environment are likely to play a part. Importantly though, all PD patients show a loss of dopaminergic neurons in the brain and increased levels of a protein called α-synuclein, which accumulates in Lewy bodies. Lewy bodies are a pathological feature of the disease, as well as some types of dementia.

In a study published this month, researchers focused on α-synuclein as a target for a novel PD treatment. "Although there are drugs that treat the symptoms associated with PD, there is no fundamental treatment to control the onset and progression of the disease. Therefore, we looked at ways to prevent the expression of α-synuclein and effectively eliminate the physiological cause of PD."

To do this, the researchers designed short fragments of DNA that are mirror images of sections of the α-synuclein gene product. The constructs were stabilized by the addition of amido-bridging. The resulting fragments, called amido-bridged nucleic acid-modified antisense oligonucleotides (ASOs), bind to their matching mRNA sequence, preventing it from being translated into protein. After screening 50 different ASOs, the researchers settled on a 15-nucleotide sequence that decreased α-synuclein mRNA levels by 81%. "When we tested the ASO in a mouse model of PD, we found that it was delivered to the brain without the need for chemical carriers. Further testing showed that the ASO effectively decreased α-synuclein production in the mice and significantly reduced the severity of disease symptoms within 27 days of administration."


Restoration of Impaired Cellular Housekeeping in Intestinal Stem Cells in Aging Flies Improves Function and Extends Life

In aging flies, we can consider degeneration of intestinal tissue and function as the primary cause of mortality, in much the same way as we can consider cardiovascular dysfunction as the primary cause of mortality in humans. It isn't the whole story, but it is a sizable portion of the story. Whenever reading research about intestinal function and life span in flies it is worth bearing this in mind: flies are not people, and while it is likely that similar processes operate in both species, their details and relative importance are likely different. Those preliminaries out of the way, today's open access paper is a recent example of extending life span in flies via improved intestinal stem cell function. The authors have discovered a faltering in cellular housekeeping that impairs stem cells in older flies, and which can be overridden via a suitable upregulation of the appropriate proteins.

Stem cell function in general declines with age, in all tissues. Stem cells and the cells of their supporting niche become damaged, their numbers diminished, and stem cells react in inappropriate ways to changes in the surrounding environment, such as by remaining quiescent rather than generating daughter cells to support the surrounding tissue. Numerous lines of work in regenerative medicine and the new longevity industry involve ways to put stem cells back to work, even damaged as they are. In animal studies this appears beneficial and less likely to induce cancer than was originally suspected. Present methods are not all that effective, however: we can hope that future therapies are more effective.

Of late, there has been a growing interest in the role of age-related changes in gut bacteria populations in disrupting tissue function in the intestine, generating chronic inflammation and other undesirable consequences. It is possible that gut bacteria have an influence on long-term health that is in the same ballpark as that of exercise. Thus it is perhaps interesting to compare work on this topic in flies with work on intestinal stem cells. There isn't all that much overlap at the present time, in terms of specific mechanisms examined, but little in any given tissue happens in isolation. There will be connections.

Loss of a proteostatic checkpoint in intestinal stem cells contributes to age-related epithelial dysfunction

Protein homeostasis (proteostasis) encompasses the balance between protein synthesis, folding, re-folding and degradation, and is essential for the long-term preservation of cell and tissue function. This balance is perturbed in aging systems, likely as a consequence of elevated oxidative and metabolic stress, changes in protein turnover rates, decline in the protein degradation machinery, and changes in proteostatic control mechanism. The resulting accumulation of misfolded and aggregated proteins is widely observed in aging tissues. The age-related decline in proteostasis is especially pertinent in long-lived differentiated cells, which have to balance the turnover and production of long-lived aggregation-prone proteins over a timespan of years or decades. But it also affects the biology of somatic stem cells (SCs), whose unique quality-control mechanisms to preserve proteostasis are important for stemness and pluripotency.

Common mechanisms to surveil, protect from, and respond to proteotoxic stress are the heat shock response (HSR) and the organelle-specific unfolded protein response (UPR). When activated, both stress pathways lead to the upregulation of molecular chaperones that are critical for the refolding of damaged proteins and for avoiding the accumulation of toxic aggregates. If changes to the proteome are irreversible, misfolded proteins are degraded by the proteasome or by autophagy. While all cells are capable of activating these stress response pathways, SCs deal with proteotoxic stress in a specific and state-dependent manner.

While these studies reveal unique proteostatic capacity and regulation in SCs, how the proteostatic machinery is linked to SC activity and regenerative capacity, and how specific proteostatic mechanisms in somatic SCs ensure that tissue homeostasis is preserved in the long term, remains to be established. Drosophila intestinal stem cells (ISCs) are an excellent model system to address these questions. ISCs constitute the vast majority of mitotically competent cells in the intestinal epithelium of the fly, regenerating all differentiated cell types in response to tissue damage. Advances made by numerous groups have uncovered many of the signaling pathways regulating ISC proliferation and self-renewal. In aging flies, the intestinal epithelium becomes dysfunctional, exhibiting hyperplasia and mis-differentiation of ISCs and daughter cells. This age-related loss of homeostasis is associated with inflammatory conditions that are characterized by commensal dysbiosis, chronic innate immune activation, and increased oxidative stress.

ISCs of old flies also exhibit chronic inactivation of the Nrf2 homologue CncC. CncC and Nrf2 are considered master regulators of the antioxidant response. In both flies and mice, this pathway controls SC proliferation and epithelial homeostasis. Whether and how Nrf2 also influences proteostatic gene expression in somatic SCs remains unclear. Here, we show that Drosophila CncC links cell cycle control with proteostatic responses in ISCs via the accumulation of dacapo, a p21 cell cycle inhibitor homologue, as well as the transcriptional activation of genes encoding proteases and proteasome subunits. We establish that this program constitutes a transient 'proteostatic checkpoint', which allows clearance of protein aggregates before cell cycle activity is resumed. In old flies, this checkpoint is impaired and can be reactivated with a CncC activator. This limits age-related intestinal barrier dysfunction and can result in lifespan extension.

Deterioration of Immune Responses in the Aged Gut in Mice is Reversed via Transplantation of Youthful Gut Microbes

Changes in the gut microbiome over the course of aging occur in parallel to a decline in immune function. The direction of causation is unclear, as both systems influence one another. Indeed, causation can exist in both directions simultaneously, as there are a great many distinct mechanisms involved in the interactions between gut microbes and the host immune system. The balance of evidence at the moment favors gut microbes as the cause and immune issues as the consequence. The results here add to those of other studies that suggest it is shifts in the gut microbe populations that drive significant dysfunction in the immune system, and that these shifts can be reversed (at least temporarily) via comparatively simple, brute-force strategies.

One of the organs that is significantly affected by age is the gastrointestinal tract and the gut-associated microbiome. These commensal microorganisms are essential for health, affecting the functions of multiple bodily systems, such as host metabolism, brain functions, and the immune response. Older individuals have age-related alterations in gut microbial composition, which have been associated with increased frailty, reduced cognitive performance, immune inflammaging and an increased susceptibility to intestinal disorders.

What drives these age-associated changes in the gut microbiota remains unknown. The microbiome is shaped by many factors including host genetics, early life events, diet, and the gut immune system. While some of these factors remain relatively constant throughout life, the function of the immune system is known to deteriorate with age. This prompts the hypothesis that dysbiosis of the intestinal microbiome in older individuals may be driven by altered cross-talk between the host immune system and the microbiota. The gut immune system can regulate the composition of the microbiome by the production of immunoglobulin A (IgA) antibodies that coat commensal bacteria. In the gastrointestinal tract, IgA antibodies are either produced by short-lived plasma cells in the lamina propria or from plasma cells that arise from germinal centre (GC) reactions in Peyer's patches (PPs).

Studies indicate clearly that the microbiome is causally influenced by the GC reaction. In the case of the gut-associated defects seen with advancing age in the GC reaction and gut microbiota, however, the direction of causation is unclear. Here, we report that the defective GC reaction in aged mice could be boosted by direct faecal transplantation from adult donors and by oral administration of cholera toxin. This demonstrates that the age-dependent defect in the gut GC reaction is not irreversible, but can be corrected by changing the microbiota or by delivery of a bacterial derived toxin.


Targeting GATA Transcription Factor to Upregulate Autophagy

Many approaches exist to boost the operation of the cellular housekeeping processes of autophagy in order to modestly slow the progression of aging. The improved health and longevity derived from the practice of calorie restriction largely occurs due to increased autophagy, for example. Disable autophagy, and studies have shown that the robust and reliable increase in life span in calorie restricted animals no longer occurs.

Cellular processes such as autophagy are regulated by a complex network of proteins, giving many possible points of intervention. Equally, it is a challenge to decipher such systems in order to find points of intervention that are not more trouble than they are worth. Present interventions to enhance autophagy that are making their way towards the clinic are calorie restriction mimetics, discovered compounds that recreate a little of a known good form of intervention. So far there has been little clinical progress in deliberate, targeted approaches to upregulating autophagy independently of the mechanisms of calorie restriction. Still, potential new targets in the regulation of autophagy, such as the example here, continue to appear year after year as research progresses.

A person born today will likely spend the last decade of her or his life suffering from age-associated conditions, like neurodegeneration, cardiovascular disease, diabetes, or cancer. Anti-aging strategies aim at closing this gap between life- and healthspan, either by behavioral - mostly dietary - interventions or by pharmacologically targeting cellular pathways that influence aging. Thus far, dozens of anti-aging compounds have been described, and most of them act via decreased nutrient signaling and/or reduced protein acetylation, which seems to be a common hallmark among pharmacological anti-aging interventions. Nevertheless, novel molecules, especially those acting via alternative pathways, are needed, since they might be used in new combinatory approaches.

In a recent study, we investigated different classes of flavonoids, a group of secondary metabolites from plants, for their ability to promote longevity. For that purpose, we conducted a high-throughput screen based on chronological aging of the yeast Saccharomyces cerevisiae, an established model for the aging of post-mitotic cells. The compound that most consistently improved the screened parameters was the chalcone 4,4'-dimethoxychalcone (DMC). Subsequent experiments unraveled that DMC administration prolonged lifespan in nematodes and fruit flies and decelerated cellular senescence in human cancer cells.

Many anti-aging compounds induce autophagy, an intracellular mechanism that recycles superfluous or damaged cellular material. DMC treatment led to elevated autophagy levels in all organisms tested, including yeast, nematodes, flies, mice and cultured human cells. Moreover - unlike many other anti-aging compounds - DMC treatment did not reduce mTOR signaling, and in yeast, the anti-aging effects depended neither on the mTOR component Tor1, nor on the sirtuin-1 homolog Sir2. Instead, a mechanistic screen in yeast revealed that DMC required the depletion of the GATA transcription factor (TF) Gln3 to exert its anti-aging effects.

GATA transcription factors (TFs) constitute a conserved family of zinc-finger TFs that fulfill diverse functions across eukaryotes. Accumulating evidence suggests that GATA TFs also play a role in lifespan regulation. This data places GATA TFs in the limelight as actionable targets for postponing age-associated disease.


Senolytic Therapies to Clear Senescent Cells Should Benefit Cancer Patients

It is well known that the present dominant approaches to cancer therapy - meaning toxic, damaging chemotherapy and radiotherapy, only slowly giving way to immunotherapy - produce a significant burden of senescent cells. Indeed, forcing active cancer cells into senescence is the explicit goal for many treatments, and remains an aspirational goal for a large fraction of ongoing cancer research. Most senescent cells self-destruct, or are destroyed by the immune system, but some always linger - and more so in older people, due to the progressive incapacity of the immune system. An immune system that becomes ineffective in suppressing cancer will be similarly ineffective when it comes to policing tissues for senescent cells.

An increased burden of lingering senescent cells is a good deal better than progressing to the final stages of metastatic cancer, that much is true, but those who undergo chemotherapy understand that it is the second worse option on the table. It has a significant cost, even when completely successful. Cancer survivors may lose as much as a decade of life expectancy, and have a higher risk of suffering most of the other chronic diseases of aging. These consequences are most likely due to the presence of additional senescent cells generated by the treatment, over and above those produced over the course of aging.

The open access paper here provides supporting evidence for (a) the presence of senescent cells following radiotherapy to be harmful to patients, and (b) the removal of those errant cells to be beneficial, reversing the harms done. Senescent cells are in many ways the ideal type of damage to occur during aging: their inflammatory secretions actively maintain a harmful state of cellular metabolism in the surrounding tissue, and that stops the moment they are destroyed. Destruction is far easier to achieve than repair of structures or delivery of replacement parts, and this is perhaps one of the reasons why senolytic therapies to remove senescent cells are the first form of rejuvenation therapy from the SENS portfolio to be developed in earnest.

Restored immune cell functions upon clearance of senescence in the irradiated splenic environment

Cellular senescence is a complex phenotype observed in diverse tissues at distinct developmental stages. In adults, senescence likely acts to irreversibly prevent proliferation of damaged cells. Senescent cells appear during chronological aging, aberrant oncogene expression, and exposure to DNA damaging agents. Expression of the tumor suppressor p16INK4a increases with age in numerous mouse and human tissues and, thus, considered a reliable marker. Exposure to ionizing radiation (IR) leads to delayed increase in p16INK4a expression in mice tissues and cancer-treated patients

Senescent cells accumulate in tissues and secrete a range of cytokines, chemokines, and proteases known as the senescence-associated secretory phenotype (SASP). Why senescent cells accumulate in vivo remains unclear. One theory suggests senescence accumulates with a decline in immune functions with age. While senescent cells support wound healing, accumulation of senescent cells also appears to contribute to tumor growth and development of age-associated diseases. Significantly, genetic or pharmacological elimination of senescent cells reverses the onset of aging and associated pathologies in mice. Removing senescent cells reduces some side effects of chemotherapy and mitigate IR-induced premature aging in murine hematopoietic stem cells.

We previously observed irradiated mice developed impaired lymphopoiesis in the bone marrow, an effect both cellular nonautonomous and dependent on p16INK4a. Our current study sought to investigate whether IR-induced p16INK4a expression interfered with immune cell function. We provide evidence that exposure of mice to ionizing radiation (IR) promotes the senescent-associated secretory phenotype (SASP) and expression of p16INK4a in splenic cell populations. We observe splenic T cells exhibit a reduced proliferative response when cultured with allogenic cells in vitro and following viral infection in vivo.

Using p16-3MR mice that allow elimination of p16INK4a-positive cells with exposure to ganciclovir, we show that impaired T-cell proliferation is partially reversed, mechanistically dependent on p16INK4a expression and the SASP. Moreover, we found macrophages isolated from irradiated spleens to have a reduced phagocytosis activity in vitro, a defect also restored by the elimination of p16INK4a expression. Our results provide molecular insight on how senescence-inducing IR promotes loss of immune cell fitness, which suggest senolytic drugs may improve immune cell function in aged and patients undergoing cancer treatment.

Towards Targeting the Toxins of Oral Bacteria in the Alzheimer's Brain

There is a clear association between poor dental hygiene and incidence of Alzheimer's disease, but is this a direct mechanism, or more a reflection of other health practices and lifestyle choices made by the sort of person who has poor dental hygiene? The direct mechanisms are thought to be (a) chronic inflammation, in the sense that gum disease allows bacteria and bacterial toxins access to the bloodstream, and this will rouse the immune system or (b) some other effect arising from the impact of bacterial toxins on critical cells in the brain.

That these direct mechanisms exist is clear: the evidence here adds to numerous past studies that show the gingipains secreted by Porphyromonas gingivalis, the most important bacterial species in gum disease, can be a real problem. But what is the size of the effect in practice, in humans rather than in animal models set up specifically to demonstrate the mechanisms in question? Recent epidemiological work suggests it is only a small contribution to the risk of dementia such as Alzheimer's disease. The best way forward is probably exactly that demonstrated here, which is to say find a way to fix the problem, then test that fix and observe the results.

Alzheimer's disease (AD) patients exhibit neuroinflammation consistent with infection. Infectious agents have been found in the brain and postulated to be involved with AD, but robust evidence of causation has not been established. The recent characterization of amyloid-β (Aβ) as an antimicrobial peptide has renewed interest in identifying a possible infectious cause of AD. Chronic periodontitis (CP) and infection with Porphyromonas gingivalis - a keystone pathogen in the development of CP - have been identified as significant risk factors for developing Aβ plaques, dementia, and AD.

A prospective observational study of AD patients with active CP reported a notable decline in cognition over a 6-month period compared to AD patients without active CP, raising questions about possible mechanisms underlying these findings. P. gingivalis lipopolysaccharide has been detected in human AD brains, promoting the hypothesis that P. gingivalis infection of the brain plays a role in AD pathogenesis.

P. gingivalis is an asaccharolytic Gram-negative anaerobic bacterium that produces major virulence factors known as gingipains. We hypothesized that P. gingivalis infection acts in AD pathogenesis through the secretion of gingipains to promote neuronal damage. We found that gingipain immunoreactivity in AD brains was significantly greater than in brains of non-AD control individuals. In addition, we identified P. gingivalis DNA in AD brains and the cerebrospinal fluid (CSF) of living subjects diagnosed with probable AD, suggesting that CSF P. gingivalis DNA may serve as a differential diagnostic marker. We developed and tested potent, selective, brain-penetrant, small-molecule gingipain inhibitors in vivo. Our results indicate that small-molecule inhibition of gingipains has the potential to be disease modifying in AD.


Exosomes in Harmful Senescent Cell Signaling

Extracellular vesicles such as exosomes are an important component of cell signaling, small membrane-bound packages of molecules that are passed around in large numbers by cell populations. The presence of lingering senescent cells is one of the root causes of aging. These errant cells never make up more than a small fraction of the overall cell population, even in very late life, but they cause considerable disruption and harm through the inflammatory signaling that they generate. Extracellular vesicles are here, as elsewhere, an important part of that signaling process.

Given that the most straightforward path towards therapy is the destruction of senescent cells, there probably isn't all that much that can be accomplished therapeutically more rapidly and effectively via a focus on exosomes. As authors of this open access paper point out, however, it is still a potentially useful area of research from the point of view of expanding knowledge of the fundamental biology of aging, how aging progresses in detail. Given that senescent cells accelerate dysfunction, and given that they do this via signaling, mapping that signaling in greater detail will probably teach us something.

Communication between cells is quintessential for biological function and cellular homeostasis. Membrane-bound extracellular vesicles known as exosomes play pivotal roles in mediating intercellular communication in tumor microenvironments. These vesicles and exosomes carry and transfer biomolecules such as proteins, lipids, and nucleic acids. Here we focus on exosomes secreted from senescent cells.

Cellular senescence can alter the microenvironment and influence neighbouring cells via the senescence-associated secretory phenotype (SASP), which consists of factors such as cytokines, chemokines, matrix proteases, and growth factors. This review focuses on exosomes as emerging SASP components that can confer pro-tumorigenic effects in pre-malignant recipient cells. This is in addition to their role in carrying SASP factors. Transfer of such exosomal components may potentially lead to cell proliferation, inflammation, and chromosomal instability, and consequently cancer initiation.

Senescent cells are known to gather in various tissues with age; eliminating senescent cells or blocking the detrimental effects of the SASP has been shown to alleviate multiple age-related phenotypes. Hence, we speculate that a better understanding of the role of exosomes released from senescent cells in the context of cancer biology may have implications for elucidating mechanisms by which aging promotes cancer and other age-related diseases, and how therapeutic resistance is exacerbated with age.


Progress Towards Blocking Alternative Lengthening of Telomeres in Cancer

Well, this is promising news. Researchers have found that inhibition of FANCM activity is a potential point of intervention to shut down alternative lengthening of telomeres (ALT) in cancer. This goal is one half of the ultimate cancer therapy, a form of treatment that is (a) capable of shutting down all forms of cancer, without exception, where (b) cancers cannot evolve resistance to its mechanisms, and (c) it requires little to no expensive, time-consuming adaptation for delivery to different cancer types. The other half is a method of blocking the ability of telomerase to lengthen telomeres, and several research groups have made inroads towards that goal. Both are needed in combination, since ALT cancers might evolve to become telomerase cancers, and vice versa.

Why would this work? All cancers absolutely require some method of lengthening telomeres in order to support their rampant growth, and - so far as we know - this means either telomerase or ALT. Telomeres are caps of repeated DNA sequences at the end of chromosomes, and a little of their length is lost with each cell division. They are a part of the counting mechanism that enables the Hayflick limit on cell division; when telomeres become short, a cell ceases to replicate and self-destructs. Only with continued lengthening of telomeres can a cell keep on dividing indefinitely. Without this, a cancer would wither away.

You might recall that the SENS Research Foundation team made an attempt to find ALT-blocking small molecules a couple of years ago as a part of the OncoSENS research program, supported by philanthropic crowdfunding. Unfortunately that failed, as small molecule screens sometimes do. It is a roll of the dice, consulting the vast compound databases in ways that are intended to maximize the odds. With the new results here, now perhaps work on the ALT side of the ultimate cancer therapy has a chance to forge ahead once more. A very positive development, for all of our personal futures.

New study reveals an unexpected survival mechanism of a subset of cancer cells

Embedded at the end of chromosomes are structures called "telomeres" that in normal cells become shorter as cells divide. As the shortening progresses it triggers cell proliferation arrest or death. Cancer cells adopt different strategies to overcome this control mechanism that keeps track of the number of times that a cell has divided. One of these strategies is the alternative lengthening of telomeres (ALT) pathway, which guarantees unlimited proliferation capability. Now, a research group has discovered that a human enzyme named FANCM (Fanconi anemia, complementation group M) is absolutely required for the survival of ALT tumor cells.

Previous studies have shown that a sustained physiological telomere damage must be maintained in these cells to promote telomere elongation. This scenario implies that telomeric damage levels be maintained within a specific threshold that is high enough to trigger telomere elongation, yet not too high to induce cell death. "What we have found is that ALT cells require the activity of the FANCM in order to prevent telomere instability and consequent cell death. When we remove FANCM from ALT tumor cells, telomeres become heavily damaged and cells stop dividing and die very quickly. This is not observed in tumor cells that express telomerase activity or in healthy cells, meaning that is a specific feature of ALT tumor cells."

FANCM limits ALT activity by restricting telomeric replication stress induced by deregulated BLM and R-loops

Telomerase negative immortal cancer cells elongate telomeres through the Alternative Lengthening of Telomeres (ALT) pathway. While sustained telomeric replicative stress is required to maintain ALT, it might also lead to cell death when excessive. Here, we show that the ATPase/translocase activity of FANCM keeps telomeric replicative stress in check specifically in ALT cells. When FANCM is depleted in ALT cells, telomeres become dysfunctional, and cells stop proliferating and die. FANCM depletion also increases ALT-associated marks and de novo synthesis of telomeric DNA. Depletion of the BLM helicase reduces the telomeric replication stress and cell proliferation defects induced by FANCM inactivation. Finally, FANCM unwinds telomeric R-loops in vitro and suppresses their accumulation in cells. Overexpression of RNaseH1 completely abolishes the replication stress remaining in cells codepleted for FANCM and BLM. Thus, FANCM allows controlled ALT activity and ALT cell proliferation by limiting the toxicity of uncontrolled BLM and telomeric R-loops.

MiR-135a-5p as a Target to Induce Greater Neurogenesis

Neurogenesis is the creation of new neurons in the brain, followed by their integration into neural circuits. It is generally agreed upon in the research community that increasing the degree of neurogenesis that takes place in the aging brain is a desirable therapeutic goal, particularly since this process appears to decline with age. Greater neurogenesis should increase both resilience to injury and cognitive function. A great deal of work takes place in this part of the field, though it is a complicated business and is not progressing towards practical therapies anywhere near as rapidly as desired. The research here is a representative example of the sort of work that has taken place over the past decade: numerous regulatory molecules have been identified, and proposed as a basis for intervention. Whether anything comes of this one remains to be seen.

In most mammalian species, the postnatal subgranular zone (SGZ) of the hippocampal dentate gyrus (DG) maintains a population of neural precursor cells (NPCs) retaining the lifelong capability to generate new neurons and astrocytes. However, this process inexorably declines with age, and this decline has been correlated with the loss of cognitive abilities and the occurrence of several brain pathologies. Currently, many translational concepts for preserving cognitive abilities in the aging brain thus aim at sustaining, or even increasing, the potential for cognitive plasticity and flexibility that is contributed by the adult-generated neurons.

Environmental enrichment and physical activity (e.g., voluntary running in a wheel) potentiate adult neurogenesis in rodents. The positive response of adult neurogenesis to these stimuli is maintained into old age and counteracts the age-associated cognitive decline in rodents and likely in humans. However, the cellular and molecular mechanisms underlying homeostasis of adult neurogenesis and its response to environmental stimuli remain elusive. We hypothesize that exploiting these mechanisms is relevant for preventing age-related cognitive decline in humans and that our animal models can contribute to providing evidence-based recommendations for an active lifestyle for successful aging.

MicroRNAs (miRNAs) are small noncoding RNAs which, by post-transcriptional repression of hundreds of target messenger RNAs (mRNAs) in parallel, tune the entire cell proteome. The functional synergism of few miRNAs achieves gene regulation essential for proliferation, cell fate determination, and survival. Interestingly, running stimulates hippocampal NPC proliferation and alters miRNA expression in rodents. Hence, we hypothesize that investigating miRNAs involved in running-induced neurogenesis would allow the identification of the most prominent pathways that constrain NPC proliferative potential in the adult mouse hippocampus.

Here, we show that exercise increases proliferation of neural precursor cells (NPCs) of the mouse dentate gyrus (DG) via downregulation of microRNA 135a-5p (miR-135a). MiR-135a inhibition stimulates NPC proliferation leading to increased neurogenesis, but not astrogliogenesis, in DG of resting mice, and intriguingly it re-activates NPC proliferation in aged mice. We identify 17 proteins (11 putative targets) modulated by miR-135 in NPCs. MiR-135 is the first noncoding RNA essential modulator of the brain's response to physical exercise. Prospectively, it might represent a novel target of therapeutic intervention to prevent pathological brain aging.


Impaired Mitophagy and Mitochondrial Function in Alzheimer's Disease

Alzheimer's disease starts with an accumulation of amyloid-β, which disrupts cellular metabolism sufficiently to lay the grounds for the chronic inflammation and aggregation of tau protein that characterize the later, severe stage of the condition. Here, researchers make the argument that a fair degree of this progression is mediated via dysfunction of mitochondria and the quality control mechanisms of mitophagy, normally responsible for removing damaged mitochondria, and that this dysfunction is caused by amyloid-β.

Mitochondria are the power plants of the cell, and a faltering of their activity has profoundly disruptive effects. Needless to say, mitochondrial dysfunction is a characteristic feature of aging. This leads to the point that aging is a complex enough phenomenon for it to be possible to argue that mitochondrial dysfunction contributes to amyloid-β and tau aggregation, not vice versa. Or that both directions of causation are real phenomena. These are not simple, easily modeled systems. The fastest way to a definitive answer is likely that of building rejuvenation therapies capable of restoring mitochondrial function to youthful levels, and observing the result.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss and multiple cognitive impairments. Several decades of intense research have revealed that multiple cellular changes are implicated in the development and progression of AD, including mitochondrial damage, synaptic dysfunction, amyloid beta (Aβ) formation and accumulation, hyperphosphorylated tau (P-Tau) formation and accumulation, deregulated microRNAs, synaptic damage, and neuronal loss in patients with AD. Among these, mitochondrial dysfunction and synaptic damage are early events in the disease process.

Recent research also revealed that Aβ and P-Tau-induced defective autophagy and mitophagy are prominent events in AD pathogenesis. Age-dependent increased levels of Aβ and P-Tau reduced levels of several autophagy and mitophagy proteins. In addition, abnormal interactions between (1) Aβ and mitochondrial fission protein Drp1; (2) P-Tau and Drp1; and (3) Aβ and PINK1/parkin lead to an inability to clear damaged mitochondria and other cellular debris from neurons. These events occur selectively in affected AD neurons.

In terms of rescuing and enhancing autophagy and mitophagy, reduced Drp1 and Aβ and P-tau levels and enhancing the levels of PINK1/parkin are proposed to rescue and/or maintain mitophagy and autophagy in affected AD neurons. The continuous clearance of cellular and mitochondrial debris is important for normal cellular function. We need more research on autophagy and mitophagy mechanisms and therapeutic aspects using cell cultures, animal models, and human AD clinical trials.


More Evidence for Cellular Senescence of β Cells to Drive Type 2 Diabetes

Recently, researchers have demonstrated that senescence of pancreatic β cells is important in both the autoimmunity of type 1 diabetes and the metabolic dysfunction of type 2 diabetes. This was very surprising in the first case, less so in the second, since type 2 diabetes emerges more readily in older individuals. The specific mechanisms by which increased cellular senescence arises in the pancreas is probably different in each case, but the use of senolytic treatments to clear senescent cells has produced significant benefits in animal models of both conditions. This adds to the many other conditions in which targeted removal of senescent cells is a viable therapy.

Here, researchers outline more evidence for an important role for cellular senescence in type 2 diabetes. It is compelling. It has to be said that s time moves on, senolytic therapies look ever more like a panacea of sorts, capable of improving near any condition where incidence is correlated with aging, and even a few where that is not the case. Given that the first senolytic drugs and supplements with well-explored pharmacological safety data, good results in mouse studies, and an emerging set of human trial results are both very cheap and readily available given a little investigation of the options, I fully expect that patients will start to take matter into their own hands long before companies can obtain regulatory approval for the first therapies in their senolytic pipelines.

Acceleration of β Cell Aging Determines Diabetes and Senolysis Improves Disease Outcomes

Type 2 diabetes (T2D) is an age-related disease characterized by a decrease of β cell mass and function, representing a failure to compensate for the high insulin demand of insulin-resistant states. Yet, the role of aging as it pertains to pancreatic β cells is poorly understood, and therapies that target the aging aspect of the disease are virtually non-existent. For many years, β cells can compensate for increased metabolic demands with increased insulin secretion, keeping hyperglycemia at bay. This compensation may be limited by the age-related decline in β cell proliferation seen in rodents. This deficiency in proliferative response to increased demand may arise partly from the accumulation of senescent β cells.

Cellular senescence is a state in which cells cease to divide but remain metabolically active with an altered phenotype. There are no universal markers of senescence, and the markers that exist are not consistent in every senescent tissue. p16Ink4a, a cyclin-dependent kinase inhibitor encoded by the Cdkn2a locus, has been identified as both marker and effector of β cell senescence. An increase in p21, another effector of cellular senescence, is thought to mark the entry into early senescence leading to increased p16Ink4a expression, which then maintains senescence, resulting in the expression of the senescence-associated secretory phenotype (SASP).

SASP profiles differ with tissue type and can include soluble and insoluble factors (chemokines, cytokines, and extracellular matrix affecting proteins) that affect surrounding cells and contribute to multiple pathologies. With age, accumulation of dysfunctional senescent β cells likely contributes to impaired glucose tolerance and diabetes. Yet, the specific contribution of β cell aging and senescence to diabetes has received little attention, and the specific SASP profile of β cells remains to be determined.

We generated a β cell senescence signature and found that insulin resistance accelerates β cell senescence leading to loss of function and cellular identity and worsening metabolic profile. Senolysis (removal of senescent cells), using either a transgenic INK-ATTAC model or oral ABT263, improved glucose metabolism and β cell function while decreasing expression of markers of aging, senescence, and SASP. Beneficial effects of senolysis were observed in an aging model as well as with insulin resistance induced both pharmacologically (S961) and physiologically (high-fat diet). Human senescent β cells also responded to senolysis, establishing the foundation for translation. These novel findings lay the framework to pursue senolysis of β cells as a preventive and alleviating strategy for T2D.

Enzymes of Xenobiotic Metabolism and Variation in Human Longevity

How much might varying competence in managing foreign compounds and biological substances, xenobiotics such as those resulting from infection or environmental toxins, determine the observed variations in human longevity? Researchers here look for variations in the genes encoding for xenobiotic metabolizing enzymes involved in dealing with these invading substances, and find a modest association with longevity in humans. While interesting, it is worth remembering that this sort of genetic study tends to fail in replication. It is rare for any association between genetic variants and longevity to reliably show up in more than one study population.

Aging is a complex phenotype responding to a plethora of drivers in which genetic, behavioral, and environmental factors interact with each other. This can be conceptualized in terms of exposome - that is, the totality of exposures to which an individual is subjected throughout a lifetime and how those exposures affect health. The exposome basically includes a wide variety of toxic or potentially harmful compounds of exogenous (environmental pollutants, dietary compounds, drugs) or endogenous (metabolic by-products such as those resulting from inflammation or lipid peroxidation, oxidative stress, infections, gut flora) origin and related biological responses during the life course.

The individual ability to properly cope with xenobiotic stress can influence susceptibility to diseases and, thus, the quality and the rate of aging, phenotypes that certainly result from the cumulative experiences over lifespan. Additionally, in all the different theories proposed to explain the aging process, a common denominator remains the progressive decline of the capacity to deal with environmental stressors to which the human body is constantly exposed.

In this scenario, a crucial role can be played by the coordinated activity of cellular mechanisms evolved for reducing the toxicity of endogenous and xenobiotic compounds to which humans are exposed. These mechanisms comprehend a broad range of reactions of detoxification that make harmful compounds less toxic, more hydrophilic, and easier to be excreted. The main effectors of these mechanisms are a large number of enzymes and transporters, collectively referred to as xenobiotic-metabolizing enzymes (XMEs) or drug metabolizing enzymes (DMEs).

With aging, there is a decline in the ability to mount a robust response to xenobiotic insults. This is somewhat attributed to the age-related reduction in liver mass, which can result in reduced metabolism rates and in the decreased kidney and liver blood flows, which can result in reduced excretion and elimination of xenobiotic and its metabolites. In addition, a reduction in the activity of XMEs and DMEs and the consequent fall in biotransformation capacity have been reported in both old animals and humans.

We reasoned that genetic variants of XME genes might affect the chance to live a long life. In order to test this hypothesis, we screened a set of 35 SNPs in 23 XME genes and their association with aging and survival in a cohort of 1112 individuals aged 20-108 years. Four variants in different genes differently impacted the longevity phenotype. In particular, the highest impact was observed in the age group 65-89 years, known to have the highest incidence of age-related diseases. In fact, genetic variability of these genes we found to account for 7.7% of the chance to survive beyond the age of 89 years. Results presented herein confirm that XME genes, by mediating the dynamic and the complex gene-environment interactions, can affect the possibility to reach advanced ages, pointing to them as novel genes for future studies on genetic determinants for age-related traits.


A Surprisingly Simple Stem Cell Therapy Restores Sense of Smell in Mice

The stem cell therapy noted here is close to the original, hoped-for vision for the field, in which transplanted cells survive and integrate with patient tissue in order to carry out useful work, restoring lost cells and tissue structure to improve function. That, as it turned out, is very hard to achieve. Typically, transplanted cells near all die, and the benefits produced by presently available stem cell therapies, such as reduced chronic inflammation, are instead mediated by signals secreted by the stem cells in the short time that they survive. Nonetheless, cell therapies in which large fractions of the transplanted cells survive to restore function remain an important goal in the field, and results such as those reported here help to keep that original vision alive.

In mice whose sense of smell has been disabled, a squirt of stem cells into the nose can restore olfaction, researchers report. The introduced globose basal cells, which are precursors to smell-sensing neurons, engrafted in the nose, matured into nerve cells, and sent axons to the mice's olfactory bulbs in the brain. "We were a bit surprised to find that cells could engraft fairly robustly with a simple nose drop delivery. To be potentially useful in humans, the main hurdle would be to identify a source of cells capable of engrafting, differentiating into olfactory neurons, and properly connecting to the olfactory bulbs of the brain. Further, one would need to define what clinical situations might be appropriate, rather than the animal model of acute olfactory injury."

Researchers have tried stem cell therapies to restore olfaction in animals previously, but it's been difficult to determine whether the regained function came from the transplant or from endogenous repair stimulated by the experimental injury to induce a loss of olfaction. So the team developed a mouse whose resident globose basal cells only made nonfunctional neurons, and any restoration of smell would be attributed to the introduced cells.

The team developed the stem cell transplant by engineering mice that produce easily traceable green fluorescent cells. The researchers then harvested glowing green globose basal cells (as identified by the presence of a receptor called c-kit) and delivered them into the noses of the genetically engineered, smell-impaired mice. Four weeks later, the team observed the green cells in the nasal epithelium, with axons working their way into the olfactory bulb. Behaviorally, the mice appeared to have a functioning sense of smell after the stem cell treatment. Unlike untreated animals, they avoided an area of an enclosure that had a bad smell to normal mice.


A Novel Approach to the Construction of Thymus Organoids

The thymus is a small but important organ; it is where thymocytes originally generated in the bone marrow mature to become T cells of the adaptive immune system. Unfortunately the active tissue of the thymus is slowly replaced by fat over the course of later life, and the supply of new T cells dwindles. This is a significant contributing cause of the age-related decline in immune function. Lacking reinforcements and replacements, the adaptive immune system becomes cluttered with senescent, exhausted, overspecialized, and just plain broken cells. It becomes overly active and inflammatory, but at the same time ineffective. It progressively becomes ever less competent when it comes to destroying cancerous and senescent cells, and defending against pathogens.

This is all well recognized, and over the years a range of efforts to regenerate the thymus have been undertaken. As of yet few have progressed much further than animal studies in mice. Recombinant KGF, which works quite well to enlarge the thymus in mice and non-human primates, failed utterly in a human trial, showing absolutely no effect. More recently, the staff at Intervene Immune have been combining some of the older and unreliable methods, such as use of growth hormone, into human tests of thymic regrowth. All of these approaches, and a few others, largely boil down to ways to upregulate FOXN1, the master controlling gene of thymic growth and T cell maturation activity. The most compelling studies in mice have been those in which FOXN1 expression was manipulated directly, and we might suspect that any therapy that grows a thymus, but fails to keep FOXN1 levels high going forward, will also fail to make a large and lasting impact on T cell generation. The thymus must be active, not just larger, and FOXN1 expression declines with age.

Tissue engineering offers an intriguing approach to the problem of the thymus, bypassing a lot of the hard work inherent in trying to manipulate expression of a given gene. (Of course replacing it with hard work of a different sort). Functional thymus tissue can be grown in small amounts, lacking a network of small-scale blood vessels, but able to be transplanted. Since thymocytes home to the thymus, thymic tissue located almost anywhere in the body will still be capable of doing its job, in principle. This has been demonstrated by implanting thymus organoids into lymph nodes, an approach being commercialized by Lygenesis. As the results here show, however, success still depends on building a suitably resilient tissue that will last for a long time following transplantation.

Gene Modification and Three-Dimensional Scaffolds as Novel Tools to Allow the Use of Postnatal Thymic Epithelial Cells for Thymus Regeneration Approaches

Many research groups have primarily focused on finding possible strategies to rejuvenate the thymus and have developed promising therapeutic approaches. However, few molecules and genes such as KGF, IL-22, IL-7, and Foxn1 have been identified as key players of the mechanistic pathway for endogenous thymic regeneration. Growth factors and hormone therapies were also explored in order to restore age-related or injury-related thymic degeneration, but, despite encouraging results, they have short-term effects and/or require a recurrent administration, which is complicated by their toxic effects on other tissues and organs.

Thymus transplantation represents another promising alternative to complement bone marrow transplantation or to treat congenital thymic anomalies, but T-cell reconstitution following thymus grafting is frequently incomplete and transient, complicated by a skewed T-cell receptor repertoire and an increased occurrence of autoimmunity.

The field of tissue engineering has put considerable efforts into the development of materials and techniques for the in vitro generation of tissues of clinical relevance. The major challenge for tissue engineering is to successfully recreate the complexity of the 3D structure of the thymic microenvironment and to fully rebuild the composition and organization of the thymic extracellular matrix (ECM). The use of thymic organoids formed by human thymic epithelial cells (TECs) and fibroblasts as well as seeding TECs into matrigel or other 3D biocompatible systems has been shown to promote a transient thymopoiesis in vivo. The use of de-cellularized thymic tissue has been suggested to overcome these limitations and has shown promising results in mouse models. However, the use of decellularized tissues, obtained from cadavers or patients undergoing cardiothoracic surgery, limits the applicability of such approaches to the availability of donors.

The use of postnatal TECs for thymic regeneration has revealed challenging because of the loss of thymopoietic function of TECs after in vitro culture. To avoid the use of embryonic TECs or induced pluripotent stem cell derived TECs, attempts have been made by combining mature TECs with different 3D systems for developing functional mini-thymus units. Several studies have been focused on the investigation of ideal biomaterials for human applicability, which need to be biocompatible, biodegradable, and easily detectable with imaging techniques regularly used in standard clinical practice. Collagen has been widely used in tissue engineering because it can be assembled in fibers closely reproducing the chemical and morphological characteristics of those present in soft tissues. Therefore, the production of collagen porous biomatrix could make this biomaterial suitable for the generation of thymic constructs.

Hence, we developed a potentially new therapeutic strategy that foresees transplantation of biomimetic scaffolds, mimicking the thymic ECM organization, obtained by seeding adult murine TECs and expanding them into 3D collagen type I scaffolds. In order to use postnatal TECs for the generation of transplantable thymic structure, we sought to induce a short-term expression of Oct4, a transcription factor involved in the maintenance or induction of pluripotency in embryonic cells, to obtain transient partial de-differentiation and promote their expansion. To create a physiologically relevant microenvironment to seed TECs, we tested 3D collagen type I scaffolds crosslinked with different amounts of 1,4-butanediol diglycidyl ether (BDDGE).

Here, we show that 3% BDDGE collagen-based scaffolds seeded with gene-modified TECs and transplanted subcutaneously in athymic nude mice were perfused and colonized by small new blood vessels and were able to sustain TEC survival in a 3D microenvironment. However, further improvement of the 3D scaffold composition is required to obtain long-term in vivo persistence of organoids that could allow the development of this approach for future clinical applications.

Telomerase Gene Therapy Treats Neurodegeneration in Mice

Researchers have been testing telomerase gene therapies in mice for more than a decade now, demonstrating extension of life, improved stem cell and tissue function, reduced cancer incidence, and so forth. The research results here, treating neurodegeneration in mice, are a representative example of the sort of work that has emerged in recent years. Telomerase primarily acts to lengthen telomeres, the repeated DNA sequences at the ends of chromosomes. Telomeres shorten with each cell division, a part of the mechanism determining the Hayflick limit to cell replication. Thus the general upregulation of telomerase should result in greater cell activity.

Telomerase upregulation was also widely expected to raise the risk of cancer, by putting damaged cells back to work, but so far that hasn't emerged in animal studies. If anything, the risk is reduced, perhaps due to increased activity in those parts of the immune system responsible for destroying cancerous and precancerous cells. One challenge in translating this work to human medicine is that telomere and telomerase dynamics are very different in mice and humans, and thus the balance of cancer risk versus improved regeneration may be quite different - though clearly clinical development is progressing, at Libella Gene Therapeutics and elsewhere.

Preventing accumulation of short telomeres may prevent or ameliorate brain aging by allowing stem cells to proliferate and regenerate damaged tissue. We have previously demonstrated that preventing accumulation of short telomeres through telomerase gene therapy can ameliorate the symptoms of cardiovascular disease, pulmonary fibrosis, aplastic anemia, and aging in general. Thus, to demonstrate that telomere shortening may be one of the causes of brain aging, here we studied the potential therapeutic effects of a telomerase gene therapy in ameliorating molecular signs of neurodegeneration associated with physiological mouse aging as well as in the context of the telomerase-deficient mouse model.

Our findings demonstrate that AAV9-Tert treatment can ameliorate signs of neurodegeneration with aging in wild-type mice as well as in the context of the telomerase-deficient mouse model with the presence of short telomeres. Our treatment was applied through an intravenous tail injection, and therefore, many other cell types throughout the body would be infected in addition to the cells in the brain. Improvements of health in other organs may have an impact on the brain and investigating the nature of this relationship could be interesting for future studies. Note also that we did not observe any increased incidence of cancer in the mice treated with AAV9-Tert, which matched our expectations since several other articles have demonstrated that telomerase reactivation alone does not lead to tumorigenesis in vivo.

Of note, the AAV9 serotype used here to express telomerase in the brain primarily transfects neurons and astrocytes but fails to transduce microglia. In our experimental setting, we found that less than 5% of the cells in the brain received the transgene using our vector and delivery method. Interestingly, in spite of the low transduction efficiency, we observed significant effects of AAV9-Tert gene therapy in decreasing DNA damage, increasing neurogenesis as indicated by increased doublecortin expression, as well as decreasing neuroinflammation (decreased GFAP expression). These findings suggest that even a small number of neurons transduced with Tert may increase the health of the environment and benefit cells that were not infected, for instance, through changing the secretory profile of cells. Even more benefits from telomerase gene therapy may be observed if higher transduction efficiencies are obtained.


Unity Biotechnology Broadens its Pipeline to Include Klotho

Unity Biotechnology is no longer just a senotherapeutics company, focused on tackling the contribution of senescent cells to degenerative aging. The principals have now branched out into the development of therapies based on increasing circulating levels of klotho, a protein found to affect, at the very least, both kidney function and cognitive function. It was discovered some time ago in mice that raised levels of klotho modestly slow aging, while lowered levels accelerate aging. Research into klotho is actually at a very interesting point right now, with researchers close to being able to determine whether the cognitive function effects are actually mediated outside the brain, such as in the aging kidney. Declining kidney function is well known to cause cognitive decline, among the many other harms it inflicts on the body.

Unity Biotechnologies has raised an enormous amount of funding, which gives them considerable leeway to adopt new programs that fit their overall vision of tackling aging. But near every company in the growing longevity industry, at every scale of funding, can do much the same. Indeed, I think that they should. There are many more projects worthy of development than there are entrepreneurs at this time, and this will continue to be the case for years yet. The research community is littered with very interesting, promising foundations for therapies to treat aging, at or close to the point at which they can be handed over to commercial development. Most were abandoned for no better reasons than grant awarding bodies are excessively conservative, funding is constrained, and the institutions of academia and industry are largely incapable of talking coherently to one another, let alone managing a complex marketplace of hand-offs from lab to startup company. We need to do better than this.

UNITY Biotechnology, Inc. ("UNITY"), a biotechnology company developing therapeutics to extend healthspan by slowing, halting or reversing diseases of aging, and UC San Francisco (UCSF) today announced that UNITY executed an exclusive, worldwide license to UCSF intellectual property relating to the alpha-Klotho protein, a circulating factor associated with improved cognitive performance.

The alpha-Klotho protein was initially identified in mice as an "aging-suppressor" that accelerates aging when the gene encoding it is disrupted, and slows aging when the alpha-Klotho protein is over-produced. In 2017 it was reported that when the alpha-Klotho protein was injected into mice it reversed the deleterious effects of aging and age-related disease on cognition.

"Circulating levels of alpha-Klotho protein gradually decline as we age. Yet, a small percentage of the population possesses naturally elevated alpha-Klotho levels that are associated with extended healthspan, enhanced cognition and less age-associated cognitive decline. We are exploring the utility of the alpha-Klotho protein in collaboration with world-renowned researchers from UCSF, with a goal to identify a potential drug candidate to treat particular diseases of aging, including cognitive decline."