Cellular Senescence as a Failed Anti-Cancer Strategy

The evolution of multi-cellular life is in essence the story of a tooth and nail struggle with cancer, one that continues even now. Complex structure, regeneration, and growth are all required in higher forms of life, but that combination means that any sort of sustained breakdown in control over cell proliferation tends to be fatal because it disrupts necessary structures. Multiple layered systems, within cells and outside them, have evolved to try to block damaged cells from uncontrolled proliferation, ranging from tumor suppressor genes to the surveillance of the immune system and its destruction of potentially cancerous cells. Cellular senescence is one of these strategies, and like all of them, it is only somewhat successful. With only a few rare exceptions, evolution has curbed cancer risk to the minimum degree needed for a species to survive, no more than that.

Cellular senescence is, of course, one of the causes of aging. Cells become senescence in response to damage, a toxic environment, or at the end of their replicative life span, and near all destroy themselves or are destroyed by the immune system. Enough linger to cause problems, however, producing the senescence-associated secretory phenotype (SASP) that disrupts tissue structure and function. Cellular senescence is an anti-cancer strategy because senescence locks down a cell to prevent replication - so it should function to remove the most at-risk cells before they can run off the rails. Indeed, this works in the early stages of life. But with enough senescent cells lurking in a tissue, the SASP changes the environment to make it much more amenable to cancer: inflammatory, pro-growth, with increased levels of cell damage. Ultimately, cellular senescence becomes an enabler of cancer.

Cellular senescence describes an irreversible growth arrest characterized by distinct morphology, gene expression pattern, and secretory phenotype. The final or intermediate stages of senescence can be reached by different genetic mechanisms and in answer to different external and internal stresses. It has been maintained in the literature but never proven by clearcut experiments that the induction of senescence serves the evolutionary purpose of protecting the individual from development and growth of cancers. This hypothesis was recently scrutinized by new experiments and found to be partly true, but part of the gene activities now known to happen in senescence are also needed for cancer growth, leading to the view that senescence is a double-edged sword in cancer development.

In current cancer therapy, cellular senescence is, on the one hand, induced deliberately in tumor cells, as thereby the therapeutic outcome is improved, but might, on the other hand, also be induced unintentionally in non-tumor cells, causing inflammation, secondary tumors, and cancer relapse. Importantly, aging leads to accumulation of senescent cells in tissues and organs of aged individuals. Senescent cells can occur transiently, e.g., during embryogenesis or during wound healing, with beneficial effects on tissue homeostasis and regeneration or accumulate chronically in tissues, which detrimentally affects the microenvironment by dedifferentiation or transdifferentiation of senescent cells and their neighboring stromal cells, loss of tissue specific functionality, and induction of the senescence-associated secretory phenotype, an increased secretory profile consisting of pro-inflammatory and tissue remodeling factors.

These factors shape their surroundings toward a pro-carcinogenic microenvironment, which fuels the development of aging-associated cancers together with the accumulation of mutations over time. Among well-documented stress situations and signals which induce senescence, oncogene-induced senescence and stress-induced premature senescence are prominent. New findings about the role of senescence in tumor biology suggest that cancer therapy should leverage genetic and pharmacological methods to prevent senescence or to selectively kill senescent cells in tumors.

Link: https://doi.org/10.3389/fonc.2017.00278

A Discussion of Cellular Senescence in Age-Related Macular Degeneration

Cellular senescence is one of the root causes of aging. A small fraction of the large number of cells that become senescent every day fail to self-destruct, and instead linger in tissues to secrete a mix of inflammatory and other harmful signals. This behavior is known as the senescence-associated secretory phenotype, or SASP. The sizable numbers of senescent cells in old tissues have been implicated as a contributing cause of numerous age-related conditions, from lung disease to cardiovascular issues to forms of arthritis. More causal links will be discovered: this is a newly energetic field of research.

As an example of the sort of thinking presently taking place, researchers here discuss a potential role for cellular senescence in macular degeneration, a progressive blindness caused by destruction of retinal tissue. While it seems fairly likely that senescent cells are involved, the question is always whether or not they are involved to a sufficient degree to be an important cause. That seems plausible based on what is known, but it isn't an open and shut case. There is considerable uncertainty, based on the existing evidence. Fortunately, now that senolytic therapies to clear senescent cells are a going concern, there is a fairly rapid way forward to learning more: remove senescent cells in aged animal models of macular degeneration, and see what happens. Someone will get around to that in the next few years, I'd imagine.

Age-related macular degeneration (AMD) is the main reason of blindness in developed countries. Aging is the main AMD risk factor, but it is a complex disease in which both genetic and environmental factors play a role. The exact mechanism of its pathogenesis is unknown. Oxidative stress, protein aggregation, and inflammation play a central role in AMD development. Early dry AMD is hardly detectable and usually asymptomatic. Its advanced form, called geographic atrophy (GA), is associated with a massive loss of photoreceptors that evokes central visual loss. A clinical hallmark of wet AMD is the presence of neovascular vessels sprouting from the choriocapillaris into the retina.

It has been proposed that cellular senescence of RPE cells plays a role in the etiology of AMD. It seems that many studies on the role of cell senescence in organismal aging and age-related pathologies support this idea. The exposure of cells to recurrent or chronic nonlethal stress might contribute to an increase in the accumulation of stress-induced senescent cells, thereby accelerating tissue aging. A growing body of evidence proves that persistent DNA damage, especially double-strand breaks (DSBs) and DNA damage response (DDR), are closely associated with cell senescence. Evidence also links DNA damage with inflammation and disease, particularly age-dependent diseases. This is sort of a vicious cycle as DNA damage-dependent senescence can lead to secretion of molecules, which can reinforce senescence and can induce DNA damage and DNA damage-dependent bystander senescence.

Retinal pigment epithelial (RPE) cells in the central retina are quiescent, and when damaged, they can be replaced by their proliferating counterparts at the RPE periphery. Oxidative stress can induce senescence in RPE cells and result in inability of peripheral RPE cells to rescue their central RPE counterparts, which can lead to a massive loss of RPE cells observed in clinically detected AMD. If most of macular peripheral RPE cells are affected by senescence, this mechanism can fail leading to AMD. Senescent RPE will be the source of pathology and have a detrimental impact on surrounding tissue through the senescence-associated secretory phenotype (SASP).

We believe that senescence associates with autophagy and DDR. All these three effects, senescence, autophagy, and DDR, can be provoked by oxidative stress, which is a major factor in AMD pathogenesis. Moreover, aging is the main risk factor of pathogenesis of AMD and can be related to oxidative stress. Inflammation associates with oxidative stress, aging (inflammaging), and AMD. Therefore, it is logical and justified to hypothesize that senescence can play a role in AMD and this process can be influenced or regulated by autophagy and DDR. Consequently, GATA4, as an identified factor to be involved in cell senescence, autophagy, DDR, and inflammation, seems to be a natural candidate to play a major role in the proposed mechanism of AMD pathogenesis. However, this is only a hypothesis, which should be verified, but we tried to show some arguments that this subject is worth further study and development.

Link: https://doi.org/10.1155/2017/5293258

An Interview with Doug Ethell of Leucadia Therapeutics

Leucadia Therapeutics is a startup company focused on Alzheimer's disease, noteworthy for being one of the few ventures to depart from the orthodoxy of immunotherapy to clear amyloid and tau protein aggregates. The Leucadia staff are working on the establishment of a faster and cheaper path to an effective therapy for Alzheimer's that nonetheless still addresses the deeper causes of the condition.

Leaving the mainstream is perhaps more of a challenge in the Alzheimer's research community than elsewhere; the US National Institute on Aging has for years been primarily an Alzheimer's concern, and the biggest of Big Pharma entities have made equally large investments in the field over that same period of time. As a result there is a great deal of institutional inertia to continue to push forward with large and costly amyloid clearance strategies that are only incremental improvements on those that have failed by the dozen in the past. Publicly advocating any other path can have a negative impact on career prospects when embedded in such a large and structured system. However, going on for two decades in to these efforts, and with no practical therapy yet to show for the billions spent, the Alzheimer's heretics are starting to become more organized and influential.

It is undeniably the case that protein aggregates of amyloid and tau are important in Alzheimer's, and if they were removed safely and efficiently, patients would benefit. But these forms of metabolic waste are not the whole story; how is it that their presence only grows in the aging brain? Is some combination of declining immune function and persistent microbial infection a significant source of protein aggregates, for example? The evidence for that hypothesis is quite compelling. And in the case of Leucadia's work, are protein aggregates observed in the aged brain there due to a failure of drainage systems? The cerebrospinal fluid is thought to carry these aggregates away for disposal elsewhere in the body, but the pathways used fail with age. Thus the slow buildup of amyloid and tau with age might be thought of as a progressive failure of clearance of these waste products, a structural and fluid flow problem, rather than a cellular problem of greater production.

This is an attractive hypothesis, not least because testing it should be a comparatively low-cost, rapid effort - very far removed from the vast expense of current amyloid clearance approaches. Leucadia is the company formed to carry this initiative forward, now that the research and evidence gathered to date has reached the point of making that leap. The Methuselah Fund and a number of other angels and organizations have invested in Leucadia Therapeutics to date, Fight Aging! among them. Since the latest round of funding is now complete, I recently had the chance to talk to founder Doug Ethell and ask some questions about the company and the approach to Alzheimer's disease.

How did Leucadia come about? What led you down this interesting path of research and development?

I'd been undertaking Alzheimer's disease research as a medical school professor for well over a decade and I gave a talk at the Rejuvenation Biotechnology Conference in 2015. David Gobel, director of the Methuselah Foundation, was in the crowd and we got to talking at a poster session later that day. Dave said the foundation would like to fund some of my Alzheimer's research, if I wanted to start a company with that money. I founded Leucadias Therapeutics a few months later and the Methuselah Foundation made an equity investment.

If you could provide an overview for the audience here of the Leucadia approach to Alzheimer's disease and the underlying rationale?

Our approach to Alzheimer's disease has been to take a step back from molecular interactions and see where we are in the forest. The 'Peculiar disease of the cerebral cortex,' that Alois Alzheimer described over a hundred years ago is notable because a significant part of the pathology forms between cells in what is called interstitial spaces. In the brain, those spaces are filled with cerebrospinal fluid, or CSF, that clears away metabolites and debris that won't go blood vessel walls. We are interested in how CSF clears away regions of the brain where Alzheimer's disease starts first, with the idea that those routes are breaking down.

Think of it a small creek in the forest. Oak trees overhand the creek and occasionally a leaf falls in and gets carried away. In late summer, before the leaves change, the creek starts to dry up and leaves are carried away slower and slower, until a threshold is reached where they form a mat and then none of them are carried away. The plaques in Alzheimer's disease are mats of amyloid-beta. As it turns out, Alzheimer's disease pathology appears first in older parts of the cerebral cortex, called allocortex, where CSF is handled very differently than in the neocortex. The allocortex is intimately connected to the olfactory system and CSF that clears interstitial spaces in the allocortex drain from the brain to the nasal cavity thorough a porous bone called the cribriform plate.

With age apertures in the cribriform plate become occluded, and that can be accelerated by life events such as head injuries and broken noses. The net effect of those occlusions is an age-dependent slowing of CSF outflow, resulting is less efficient CSF-mediated clearance of the allocortex. Those leaves (the amyloid) start to accumulate and gum up the works, leading to in the accumulation of factors that cause Alzheimer's disease pathology. At Leucadia Therapeutics, we're developing a way to restore the clearance of CSF from those areas, with a product we call Arethusta. The name is derived from Greek mythology; the water nymph Arethusa was being pursued by the river god, Alpheus. Artemis let her her escape by helping her turn into a hidden underground creek. Arethusta creates a hidden stream so people can escape Alzheimer's disease.

You just raised your first round; what will be achieved with the funding now in hand?

This raise provides a tremendous boost as it allows us to hire more people, expand on our intellectual property, resolve engineering and manufacturing issues, and refine our regulatory strategy. Our goal is to start clinical trials in 2019 so there is plenty to do. The raise adds quite a bit of momentum.

In recent years I recall some independent research from other groups to support drainage issues as a significant cause of protein aggregation in the brain. Which of these results do you think add the most weight to your work?

That work involves CSF uptake from surface of the neocortex by structures that have been called glymphatics. Very interesting stuff, but a bit different than that allocortex and cribriform plate system we focus on. I published a hypothesis paper about the CSF clearance and Alzheimer's disease connection in a 2014 paper in the Journal of Alzheimer's Disease, after 2 years of editorial review. I first reasoned this mechanism in 2010. In comparison, the first glymphatic paper appeared in 2013.

A lot of alternative theorizing on the causes and progression Alzheimer's is taking place these days, people challenging the primacy of the amyloid hypothesis. Have any of these caught your eye as compelling?

Amyloid deposits (plaques) are a definitive feature of Azheimer's disease pathology, so it is certainly involved. The question is, are those deposits cause or effect? The amyloid hypothesis states that amyloid accumulations cause Alzheimer's disease, but my perspective is that plaques are simply effects, manifestations if you will, of an underlying condition that allows them to form. Ten billion has been spent on many failed clinical trials that centered on the amyloid hypothesis, and some are still ongoing, but none of them addressed the underlying cause of amyloid accumulation. Even if they were successful in clearing some plaques, they'll come right back. Leucadia's approach is to treat the underlying cause and let the brain take care of amyloid clearance by itself.

I feel that the long absence of tangible process towards therapies for Alzheimer's disease has led people to fixate on tiny gains rather than the goal of a cure. But what does realistic success look like in the fight against Alzheimer's over the next decade or so?

I spent over a decade looking at amyloid effects on neuronal death and neuroimmune interactions. Over that period, it got to be more and more depressing to watch an unbroken string of failed clinical trials up-close, played out in slow motion. The ball was pushed down the field a few yards at a time. It didn't go anywhere ... not for 25 years. There was a concerted effort by funding agencies to keep everyone viewing Alzheimer's disease research the same way. Neitzsche had it right when he wrote that the prevailing interpretation is a question of power and not truth.

What the Alzheimer's field desperately needed, and still needs, is dissenting voices that say, "There's something we're missing here. Something big." I'm one of those voices and let me tell you, when you rock the boat by challenging dogma, well-connected people whose livelihoods are built on that dogma take great offense, even if they've been proven wrong time and again. As for progress over the next decade, advances won't come in dribs and drabs but in bursts of activity. At Leucadia, we're developing a very significant advance that takes the field in an entirely different direction.

If this all works out well, and the Leucadia therapy does produce the desired outcome in patients, where next?

We are absolutely focused on slowing the relentless progression of Alzheimer's disease pathology. That's a pretty tall order, and once we get there, then we'll see about setting some new goals.

Death Receptors as Biomarkers for Cardiovascular Mortality

Researchers here present evidence for the appropriately named death receptors to be biomarkers for cardiovascular disease risk, an indirect measure of the damage accumulating in the vascular system over the course of aging, and its effects on cellular biochemistry. The research community is very interested in establishing reliable, easily measured biomarkers that relate to age-related disease, mortality, and known mechanisms of aging. The more that exist, the more likely it is that these biomarkers can be combined in some algorithmic way to generate a more precise overall biomarker of biological age - something that can be used to rapidly assess the performance of the first rejuvenation therapies, as they arrive, and to steer their development.

Death receptors are activated, for example, in the case of infections when white blood cells that have combatted a virus are to be removed. It was previously known that death receptors in the blood can be measured, but not whether an elevated level was linked to increased cell death in type 2 diabetes and arteriosclerosis. The aim of the study was therefore to investigate whether "death receptors" could be used as a marker that could be linked to ongoing tissue damage and if this could be used to predict the risk of developing diseases. The results show that increased cell death can be linked to increased levels in the blood of three different members of the same "death receptor family" (TNFR-1, TRAILR-2 and Fas). Increased cell death is seen in type 2 diabetes as well as arteriosclerosis.

High blood sugar and blood fats (low levels of HDL, "the good cholesterol") subject the body's blood vessels and insulin-producing beta cells to stress. Long-term stress damages the cells and can cause the death receptors on the surface of the cell to trigger a cell suicide program within the cell. "When the beta cells are damaged, the production of insulin decreases, which increases the risk of diabetes. The damage activates repair processes in the blood vessels. If these are not properly resolved, this usually leads to the development of plaque in the blood vessels (arteriosclerosis). The formation of cracks in this plaque is the primary cause of myocardial infarction and stroke."

The study also looked at the connections between different risk factors - age, BMI, blood fats, blood sugar and blood pressure - and the death receptors TNFR-1, TRAILR-2 and Fas in blood samples from 4,742 people who are part of the population study Malmö Diet Cancer. Samples from the 1990s were compared with the risk of suffering from diabetes, heart attack, and stroke in the coming 20 years. The results show clear links between the level of death receptors in the blood and the different risk factors. High levels of death receptors were common in diabetics which indicates increased cell stress and risk of damage to different organs. Among non-diabetics, high levels of death receptors were linked with an increased risk of developing diabetes and cardiovascular diseases. This indicates that the level of death receptors in the blood reflects the damage that the risk factors cause in different organs.

Link: https://www.lunduniversity.lu.se/article/death-receptors-new-markers-for-type-2-diabetes-and-cardiovascular-disease

Yet More Evidence for Impaired Drainage of Cerebrospinal Fluid in Aging

Leucadia Therapeutics is one of the young companies shepherded by the Methuselah Fund, in this case working on an Alzheimer's treatment predicated on a theory of the disease that views impaired drainage of cerebrospinal fluid as an important cause. Alzheimer's disease is a condition characterized by a build up of protein aggregates, and one of the ways in which the brain normally removes these aggregates is through drainage of cerebrospinal fluid out into the body. The passages for that drainage, like most other bodily systems, fail over time. An increasing amount of supporting evidence for this to contribute to age-related disease has emerged in recent years.

In the example here, researchers arrive at the consideration of failing cerebrospinal fluid drainage from a quite different position, the study of hydrocephalus, or excess accumulation of cerebrospinal fluid in the brain. This is not uncommon in older individuals, and there is a noted overlap with Alzheimer's disease - it is not hard to join the dots between these two areas of research. Evidence for one tends to support the other, and the various research groups exploring the physiology of drainage in the brain may well wind up converging on the same destination.

Syndromes of progressive neurological disturbances in the setting of normal cerebrospinal fluid (CSF) pressure have been termed as "normal pressure hydrocephalus" (NPH). Patients without known precipitating factors are diagnosed with idiopathic NPH (iNPH), the mechanism of which remains largely unknown. However, the steep increase in the incidence of iNPH in individuals who are 60 years of age or older suggests an association with aging. Some recent studies have emphasized on the primary role of abnormal water/blood drainage or viscoelasticity changes in the brain parenchyma as the likely mechanisms underlying age-related development of the disease.

Nevertheless, since the initial reports, the immediate improvement in symptoms following removal of CSF through a lumbar tap has not only been useful for clinical purposes, but has also suggested abnormal perfusion as the direct cause of clinical manifestations. Despite the body of evidence demonstrating changes in blood flow following the "tap test" (TT), there are no established diagnostic criteria based on blood flow imaging. It is critical that iNPH be diagnosed sufficiently early to enable CSF diversion using a shunt where appropriate to prevent irreversible damage. Thus, there is a need for novel, non-invasive techniques to assess this condition in the elderly population.

Recently, mapping the low-frequency phase in a blood oxygenation level-dependent (BOLD) signal time-series has been proposed as a clinically useful biomarker in cerebrovascular diseases. In the present study, we acquired resting-state BOLD magnetic resonance imaging (MRI) scans before and after a spinal TT, and compared the BOLD lag maps to evaluate the effect of treatment on brain perfusion in subjects with iNPH.

We observed an abnormal phase in the periventricular region where the deep veins converge. Under healthy conditions, the phase or relative drainage time in this region consistently exhibited a late venous phase. This abnormally long drainage or "wash-out" time in iNPH was normalized by TT, while the global mean of the phase remained stable. Collectively, these results permit an interpretation that a part of the deep venous system is drained by collaterals in iNPH instead of the normal route via the internal cerebral veins. The broad change after TT may reflect the normalization of this state, involving a change in the drainage pattern. Altered venous drainage has been observed in chronic NPH and the periventricular area may be one of the commonly affected sites of this venous inefficiency.

The fact that both normal aging and abnormalities in iNPH (which is corrected by TT) involve deep venous insufficiency may have etiological implications, as this suggests altered venous drainage in the absence of pathological ventricular dilation. Accordingly, for example, a causal relationship between hydrocephalus and periventricular edema may be questioned. It can also imply an initiating role of venous congestion in brain compliance reduction which develops during both pathological and aging processes. Although the concept of venous inefficiency as the cause of hydrocephalus is not new, it has not been linked to aging. Although the role of CSF in the mechanism cannot be inferred from the present data, it is interesting that affected areas encompass regions related to CSF turnover.

Link: https://doi.org/10.3389/fnagi.2017.00387

Asking the Right Question: Do You Want to Live Longer, if Good Health is Guaranteed?

Historically, the public at large has shown themselves to be quite disinterested in living longer. Over the years I've been aware of the longevity science movement, it has always been a challenge to expand the community towards greater acceptance, support, and funding. As an example of attitudes we observe, you might look at the Pew survey of attitudes to life extension from a few years back, in which the people surveyed generally agreed that they wanted to live a few years longer than their peers - in the same sort of way as a house should be just a little bit larger than those of the neighbors, to make the point, but not so much so as to be gauche. Humanity is ever petty in the details when conducting any of its grand madnesses; we can see that in even a cursory glance across a lengthy history of what is, by modern standards, a series of sweeping, cruel insanities. Yet we will be judged just as harshly by those yet to come.

Are we asking the right questions? It has long been thought in our community, though gathering supporting evidence for this hypothesis is ever a difficult proposition, that people are on the whole unenthused by the prospect of longevity because they instinctively feel that a longer life would mean becoming ever more decrepit and sick. They think that superlongevity would mean a collapse into an exaggerated caricature of a wizened elder, unable to do anything other than suffer ever more bitterly. This hypothesis for the public rejection of longevity science for so many years was outlined more than a decade ago, and brought up again at the time of the aforementioned Pew study.

Yet "older for longer" is not the outcome that rejuvenation therapies will achieve. It was never the plan, and no researcher has ever claimed to be working towards that end. Functional, working rejuvenation biotechnologies based on periodic repair of the cell and tissue damage that causes aging will instead postpone aging in the young, and restore health and youthful ability to the old. They will turn back age-related disease. The future is not being older for longer, but rather being younger for longer. This has proven to be a very difficult message to deliver; it has been repeated over and again, and never seems to stick.

Yet in the past few years, a few small surveys have shown that if you ask the right questions in the right context, then ordinary, everyday people will say that they want greater longevity. The right question is whether or not one would want to live longer if health is guaranteed for those additional years. Focus on the health, and people inch towards wanting more time. We have yet to collectively figure out how this should translate into our advocacy for rejuvenation research - it isn't quite as straightforward as one would hope. After all, the message we have delivered for years is exactly that we want to extend health as well as overall life span, and that in fact the only practical way to achieve longevity is to provide greater and longer-lasting health.

People say they want to live longer - if in good health

Longevity is a such a pervasive goal in public health policy and even popular media, but individually most people only want to live long lives if they will be healthy, according to a new study. "People in three cultures from around the world are reluctant to specify their desired longevity. To me this is interesting because longevity is such a valued public health objective, but at the individual level, longer lives are a goal 'only if' I remain healthy."

The results of these interviews reinforce previous findings from this research group that revealed many older adults - in various cultures - think of life as not a smooth continuum of time but segmented into different states. The researchers refer to four "ages" or stages of life, including the third age, which is an active retirement where people leave traditional work and family roles, followed by the fourth age. "People seem to view one part of the future as wanted and another as not wanted, typically the 'fourth age' which is basically the period when one might experience a disability or a potential health decline."

For this study, the researchers interviewed 30 people in each country, and they recruited the sample with sex and age quotas to reflect a range of experience with retirement. About one-third of respondents did not express aspirations for a longer life. "Some felt their lives had already reached a stage of completion, and others as a form of fate acceptance." A larger number of respondents did mention they wanted to extend their lives. Yet less than half of that group noted a specific amount of time they desired to live. The strongest opinion among that group was the desire to live longer only if they maintained their current or what they deemed to be acceptable levels of health.

Is longevity a value for older adults?

The human desire to prolong life and postpone death has a long history. In modern times, population longevity, as measured by the statistical estimate of life expectancy, is taken as a measure of nations' progress and development. The promotion of longer lives, principally through reduced mortality at younger ages, is a prominent goal of public health policy and research. Academic units concerned with gerontology have been adding the term longevity to their titles - a center for longevity, a longevity institute. Presumably, this skirts the negative connotation of aging and aligns the organization with a desirable end. Longevity can be an organizational mission in a way that aging cannot.

At the same time, longevity is not without shadows because modern medical care can maintain lives that are felt to be too long. At the population level, rising numbers of long-lived persons can pose societal challenges. Sheer longevity is also qualified by the age from which it is projected, for the hope of a long, full life is one thing at age 10 or age 20, but another in the seventh, eighth, and further decades of life. This latter stretch is the concern of our paper.

Longevity counts time from some point forward but it is also an individual perception about time left before the ultimate deadline of death. Deadlines are motivators and none more so than death. The question about future time left and one's goals can be reshuffled to ask another question: whether time left is itself a goal. Do older people value longevity for themselves? That is the focus of our analysis, based on conversational interviews with older adults in three cultures. The study of "desired longevity" (vs. expected longevity) has been quite limited, which is particularly puzzling given such theoretical interest in the end of life and gerontology's tacit assumption that most people want to live a long life. On the one hand, the modern promise of increasing health and vitality predicts an embrace of longevity. On the other hand, worries about late-life frailty and illness may make people hesitate to welcome extended lives.

Survey techniques have been used to ask adults about desired longevity, this in order to examine the distribution of replies (always contingent on respondents' ages) as well as associated factors that may explain the replies. One feature of these findings is a curious amount of non-response (refused to answer, don't know) to questions about desired longevity. Distributions of numerical answers about desired longevity also display another pattern: the "age heaping" of replies at five-year intervals, such as 80, 85, 90, etc. Taken together, approximate-age replies along with nontrivial amounts of response refusal suggest that older adults' longevity goals may not be sufficiently measurable by survey techniques.

In this study, we asked people in an open-ended way about their desire for longer life: Would you like to have more time? What age would you like to become? This was something more specific than asking about a preference for survival without reference to any length of time; about one's plans for the future; or whether people see the future as open or limited, as in studies of future time perspective. Our attempt was to discover whether there were preferred temporal spans with which older adults framed their futures and plans.

The two-question series about extra years and desired age ("How old would you like to become?") was designed to generate talk about extended life. Free to answer the questions in their own way, participants could say any number of things about longer life during the interviews. Amid these responses, our analysis capitalized on a pattern that was strongly apparent. When it came to desired longevity, most people did in fact want to live longer, but few supplied a numerical answer that was not also conditional on the maintenance of continued good health. The majority preference was for longer life but "only if."

The health stipulation was cited by three-quarters of the 57 cases who desired longer lives. This stance was a prominent pattern, and in the replies to our questions there were certain similarities: the conditional expressions (if, as long as, it depends), the anecdotes about others in poor health, and the reference to medical discourse about quality of life. The bundling of longevity desires with a health stipulation was common to all three research sites. Such similarities suggest to us that longevity expectations, while personal expressions, are also generated from social discourse of a kind that exists in the three cultures and that yields shared styles of talk about extended life. We posed questions to individuals and each replied in his or her own way, yet there was a consistent, cultural convention favoring health-qualified longevity.

Young Plasma Improves Liver Function in Old Rats by Boosting Autophagy

In the research here, injections of blood plasma from young rats are shown to improve autophagy and liver function in old rats. This is interesting given the so far mixed evidence for young to old plasma transfer to be beneficial. There is, however, a history of research to show that increased levels of the cellular maintenance processes of autophagy can improve liver function in old rodents. Autophagy normally declines with age, and this appears to contribute to a variety of issues, such as loss of stem cell activity. You might recall that increasing the number of receptors on lysosomes in old rats can improve liver function; lysosomes are the portion of the autophagic infrastructure that break down damaged proteins and structures, and they function more effectively when equipped with more receptors.

The young to old plasma transfusion strategy is an outgrowth of parabiosis research in which the circulatory systems of a young and old individual are linked. This worsens measures of aging in the younger individual and improves them in the older individual. Current opinion in the research community is divided between the hypothesis that factors in young blood improve cell and tissue function, or that factors in old blood harm cell and tissue function. There is evidence for both sides, and the balance has swung back and forth over the past few years.

The study here adds something new, meaning the evidence for beneficial effects of plasma transfer to be primarily mediated by increased autophagy, at least in the liver. This has been demonstrated for calorie restriction and a number of related methods of modestly slowing the aging process in laboratory species - autophagy is clearly important in the hierarchy of biological systems that determine the relationship between environmental circumstances and natural variations in the pace of aging. Given that those approaches fail to extend life in humans and other long-lived species to anywhere near the same degree as occurs in short-lived species, one might speculate that the same unfortunate relationship will apply here. Parabiosis might turn out to be just another way of manipulating some of the beneficial cellular reactions to calorie restriction, achieving the same poor results on life span in humans, but possibly still a useful degree of other benefits to health.

Recent studies showing the therapeutic effect of young blood on aging-associated deterioration of organs point to young blood as the solution for clinical problems related to old age. Given that defective autophagy has been implicated in aging and aging-associated organ injuries, this study was designed to determine the effect of young blood on aging-induced alterations in hepatic function and underlying mechanisms, with a focus on autophagy.

Aged rats (22 months) were treated with pooled plasma (1 ml, intravenously) collected from young (3 months) or aged rats three times per week for 4 weeks, and 3-methyladenine or wortmannin was used to inhibit young blood-induced autophagy. Aging was associated with elevated levels of alanine transaminase and aspartate aminotransferase, lipofuscin accumulation, steatosis, fibrosis, and defective liver regeneration after partial hepatectomy, which were significantly attenuated by young plasma injections.

Young plasma could also restore aging-impaired autophagy activity, while inhibition of the young plasma-restored autophagic activity abrogated the beneficial effect of young plasma against hepatic injury with aging. In vitro, young serum could protect old hepatocytes from senescence, and the antisenescence effect of young serum was abrogated by 3-methyladenine, wortmannin, or small interfering RNA to autophagy-related protein 7. Collectively, our data indicate that young plasma could ameliorate age-dependent alterations in hepatic function partially via the restoration of autophagy.

Link: https://doi.org/10.1111/acel.12708

Mutational Damage in Long-Lived Brain Cells Correlates with Age

Is random mutational damage to nuclear DNA a sizable cause of aging? The consensus in the scientific community on that question is that it is an important cause, with the theory being that this results in sufficient change in protein production and cellular behavior to produce degraded function. That consensus is challenged, however, and at present there is a distinct lack of supporting evidence for either position, even given a few intriguing studies from recent years. It is well known that mutation level correlates with age, and methods of slowing aging also slow the increase of mutational damage. So every aspect of aging does in fact tend to correlate with mutation load, but that doesn't necessarily tell us anything about cause and effect - and that is the case here.

Aging in humans brings increased incidence of nearly all diseases, including neurodegenerative diseases. It has long been hypothesized that aging and neurodegeneration are associated with somatic mutation in neurons; however, methodological hurdles have prevented testing this hypothesis directly. Markers of DNA damage increase in the brain with age, and genetic progeroid diseases caused by defects in DNA damage repair (DDR) are associated with neurodegeneration and premature aging. While analysis of human bulk brain DNA, comprised of multiple proliferative and non-proliferative cell types, revealed an accumulation of mutations during aging in the human brain, it is not known whether permanent somatic mutations accumulate with age in mature neurons of the human brain. Here, we quantitatively examined whether aging or disorders of defective DDR results in more somatic mutations in single postmitotic human neurons.

Somatic mutations that occur in postmitotic neurons are unique to each cell, and thus can only be comprehensively assayed by comparing the genomes of single cells. Therefore, we analyzed human neurons by single-cell whole-genome sequencing (WGS). Since alterations of the prefrontal cortex (PFC) have been linked to age-related cognitive decline and neurodegenerative disease, we analyzed 93 neurons from PFC of 15 neurologically normal individuals from ages 4 months to 82 years. We further examined 26 neurons from the hippocampal dentate gyrus (DG) of 6 of these individuals because the DG is a focal point for other age-related degenerative conditions such as Alzheimer's disease. Finally, to test whether defective DDR in early-onset neurodegenerative diseases is associated with increased somatic mutations, we analyzed 42 PFC neurons from 9 individuals diagnosed with the progeroid diseases Cockayne syndrome (CS) and Xeroderma pigmentosum (XP).

Our analysis revealed that somatic single-nucleotide variant (sSNVs) accumulated slowly but inexorably with age in the normal human brain, a phenomenon we term genosenium, and more rapidly still in progeroid neurodegeneration. Within one year of birth, postmitotic neurons already have ~300-900 sSNVs. Three signatures were associated with mutational processes in human neurons: a postmitotic, clock-like signature of aging, a possibly developmental signature that varied across brain regions, and a disease- and age-specific signature of oxidation and defective DNA damage repair. The increase of oxidative mutations in aging and in disease presents a potential target for therapeutic intervention. Further, elucidating the mechanistic basis of the clock-like accumulation of mutations across brain regions and other tissues would increase our knowledge of age-related disease and cognitive decline. CS and XP cause neurodegeneration associated with higher rates of sSNVs, and it will be important to define how other, more common causes of neurodegeneration may influence genosenium as well.

Link: https://doi.org/10.1101/221960

Highlights from Yesterday's /r/futurology AMA with Aubrey de Grey

Aubrey de Grey of the SENS Research Foundation took a few hours from his packed schedule yesterday to answer questions from the community at /r/futurology. It is a pity that we can't get a full day of his time at some point - clearly there are way too many interested folk with questions and not enough hours to answer more than half of them. It is a sign of progress, I hope, that ever more people recognize that the SENS approach to the development of rejuvenation therapies is promising, and understand enough of the science to ask intelligent questions about the details.

SENS is simple enough to explain at the high level: identify the cell and tissue damage that (a) appears in old tissues but not in young tissues, and (b) is caused by the normal operation of metabolism, not by some other form of damage. The resulting short list includes the causes of aging. It may include some other things as well, that in the end turn out not to need fixing, but why take the chance? In modern biotechnology and life science research, it is faster and cheaper to develop a repair therapy and see what happens than it is to painstakingly figure out how everything fits together.

When de Grey first evaluated the field of aging research, back before the turn of the century, he found that the causes of aging by the above definition were largely known, with a good deal of evidence in support of each one. Yet next to no-one was working on fixing them. Since then, he has campaigned tirelessly to build organisations, assemble allies, raise funding, and persuade researchers, and all of that to ensure that the scientific and biotechnology communities do in fact move ahead with a repair-based approach to building functional rejuvenation therapies. It has been surprisingly hard work, given a research community that was hostile towards the idea of treating aging as a medical condition versus merely observing it, and a public at large who seem disinterested in living longer in good health. Nonetheless, here we are today, on the verge of the first rejuvenation therapies making it into the clinic, and with a growing number of research, investment, and business interests showing great interest in treating aging.

Aubrey de Grey, AMA, December 7th at /r/futurology

I've noticed in the last year you seem a lot more optimistic about the timeline.

I wouldn't say a LOT, but yeah, it's been a good year. Basically just the cumulative progress, both on the science and on the public attitude and funding stream. I'm still cautious, because for sure we are still really struggling for funds, but I'm hopeful.

If you were to find all the funding you'd ever need, how long until you make major breakthroughs in all 7 areas and essentially completely remove aging?

50% chance: 20 years.

What do you think were the biggest wins of the last couple of years in SENS-relevant advocacy, research, and development? What has moved the needle?

There have been lots. On the research I would highlight our paper in Science two years ago showing how to synthesize glucosepane and our paper in Nucleic Acids Research one year ago showing simultaneous allotopic expression of two of the 13 mitochondrial genes. Both those projects have greatly accelerated in the meantime as a result of those key enabling breakthroughs; watch this space. On advocacy I think the main win has been the arrival of private capital; I would especially highlight Jim Mellon and his Juvenescence initiative, because he is not only a successful and energetic and visionary investor, he is also a highly vocal giver of investment advice.

Can give your thoughts on Mark Zuckerberg's plan to "cure all diseases" within his child's lifetime? I suspect there's a lot you could talk about regarding that.

Mark is (as far as I can tell) not well-informed about this area. Unlike Page and Brin, who were quite assiduous more than a decade ago in educating themselves on matters technovisionary including medical (I first met them both in that era), Zuckerberg seems to be reluctant to reach out to those who actually know stuff. Anyone who can get me an hour of his time, you could save a lot of lives.

Is there anything new you are able to say about the breaking of cross-links in the extracellular matrix?

Absolutely. Short story, we now have a bunch of glucosepane-breaking enzymes, and we are within a few months of spinning the work out into a startup.

The SENS strategy to migrate mitochondrial DNA (mtDNA) into the nucleus seems to be preventive engineering approach rather than a maintenance approach. In light of new techniques like killing senescent cells, why wouldn't killing off cells that have given in to mutant mitochondria make more sense?

Great question - see my early papers on the subject. Basically the issue is that the majority of mutant mtDNA in an aged body is in muscle fibres, which do not get completely taken over, only segments a millimeter or so long, so we would do much more harm than good if we zapped the whole fibre.

RepleniSENS describes the thymus rejuvenation project. How does this approach compare to directly injecting stem cells into the recipient's thymus?

Actually we have discontinued that work, mostly because we were basically overtaken. A raft of approaches seem to be working: our approach of building a new one, or growth factors to regrow the old one, or even tricks to repopulate the T cell pool by proliferation in the periphery (i.e. without a thymus).

Some researchers attempt to eliminate mutated mitochondrial genomes from the cell. Would you reckon these approaches have a chance of success?

The work you referenced is terrific, but it is intrinsically limited to mitochondriopathies that are caused by inherited, single mutations, whereas in aging we have different ones in different cells. There are some ideas out there for tipping (reversing) the selective advantage enjoyed by mutant mtDNA without being sequence-specific, but they are not all that promising yet.

Once we have an efficient senolytic drug and we can get rid of a significant number of senescent cells in the body, do we also have to clear the senescence associated secretory phenotype (SASP) that has been secreted over the years or is it something that the metabolism can naturally get rid of?

The latter. The SASP molecules have a short half-life.

Aside from funding, what do you consider to be a burden or delay for your type of research?

Nothing. Seriously, nothing at all. We have the plan and we have the people. It's all about enabling those people, giving them the resources to get on with the job.

How come the epigenetic changes and changes to our microbiome that accumulate with age are not a part of the categories of damage? When do you predict that rejuvenation approach as a solution to the problem of aging will become accepted by clear majority of scientists?

The microbiome is basically a highly dynamic population of cells, hence it is virtually certain to become right on its own when we fix everything else (even assuming that there is anything suboptimal about it in old age in the first place). For epigenetic changes, this is also the case if you mean coordinated ones that happen across all cells of a given type. If you mean drift, i.e. epimutations, my explanation for that is protagonistic pleiotropy (see my 2007 paper with that title). Rejuvenation is already accepted as a solution by most scientists, and it is being reinvented by other people. See for example the 2013 "Hallmarks of aging" paper.

How confident are you still in your previous prediction that humans will be able to control aging by 2029?

I think we've slipped a few years, entirely because of lack of funding. The tipping point will be when results in mice convince a critical mass of my curmudgeonly, reputation-protecting expert colleagues that rejuvenation will eventually work, such that they start to feel able to say so publicly. I think that's on the order of five years away.

Given current funding, how far away from robust mouse rejuvenation do you think you are?

My estimate is 5-7 years, but that's not quite "given current funding". My overoptimism in saying "10 years" 13 years ago consisted entirely of overoptimism about funding - the science itself has not thrown up any nasty surprises whatsoever - but nonetheless I am quite optimistic as of now about funding, simply because the progress we have made has led to a whole new world of startups (including spinouts from the SENS Research Foundation) and investors, so it's not only philanthropy any more. Plus, the increase in overall credibility of the approach is also helping to nurture the philanthropic side. We are still struggling, that's for sure, but I'm feeling a lot surer that the funding drought's days are numbered than I felt even two or three years ago.

It was some time ago that you guys published your paper on inserting the enzyme into white blood cells to help them break down 7-ketocholesterol, I know a company was spun out not to long after that. Are they making good progress?

Actually, of all our (so far five) spinouts, that's the one that has rather lost its way. We are working to reboot that work and get it moving more promisingly. A lot of the problem was that it was bankrolled by one wealthy person, so that (rather like Calico) it had no incentive to let the world (or even me) know what it was doing.

When would you guess that we will have the first, direct evidence of human rejuvenation through removal of senescent cells (also considering self-experimenting individuals, which could get there first)?

To start at the end: if it works, the first evidence will indeed quite probably be from self-experimentation. Of course it will be n=1 so it will be very provisional evidence, but you knew that. So, when? - that mostly depend on the extent to which humans reproduce what has been seen in rodents, where the benefits of removing senescent cells were a lot broader than I (or anyone, I think) would have anticipated. We just don't know.

You have recently accepted a position as Vice-President of New Technology Discovery at BioTime Subsidiary AgeX Therapeutics. Can you give an overview of why you accepted this position and how it affects your current work at SENS?

I'm still defining my role there, but it is a big deal. I am there 30% so my primary affiliation remains SENS Research Foundation. But the emergence of the private-sector component of the rejuvenation biotech effort is a hugely important recent advance, and for me to have an official foot in both camps makes a strong statement. Also, it is a huge thing for me to be finally working closely with Mike West, who has been a hero of mine for 20 years. The two roles will certainly dovetail a lot: at AgeX my basic task is to come up with new therapeutic ideas, and naturally that will feed off what we are doing and have done at SRF.

Given that cells can reverse their age through induced pluripotency, do you see this as a viable strategy for reversing aging in humans, or is it too difficult and dangerous to do in vivo?

As of now it's definitely dangerous in terms of its carcinogenicity. However, we may be able to reduce that soon. I am particularly excited by the recent work of the awesome researcher Vera Gorbunova on the difficulty of dedifferentiating cells from naked mole rats; I suspect that that work may uncover ways to be more selective and controlled with in vivo dedifferentiation.

Has your position on the relative importance of the stem cell side of aging changed over the years? I know that in earlier years I was somewhat convinced that stem cell decline was fairly secondary to other parts of SENS.

It very much remains to be seen. In some tissues, like the substantia nigra where cell loss causes Parkinson's disease, I'm pretty sure we will indeed need stem cell therapy. In other places, the failure of stem cells to maintain their numbers and/or their proliferative vigour seems to be quite largely determined by the systemic environment, i.e. by what is and is not present in the circulation, and there I agree that recovery is quite likely to be largely spontaneous once we fix other stuff.

It seems likely that artificial intelligence will be a necessary tool in order to reach longevity escape velocity. I was wondering how much of a role does artificial intelligence play in your research? Is this something you devote many resources to?

We don't, but that is because other major players in this field (and good friends of mine), such as Alex Zhavoronkov and Kristen Fortney, are doing it so well already (with Insilico Medicine and BioAge respectively). They are both awesome and massively committed crusaders for this mission. Check out the BioData West conference that will occur in San Francisco a couple of days before our Undoing Aging conference in Berlin; I will be chairing a session on this.

With the recent departure of Calico's Head of R&D for GSK, do you think that there is a chance that Calico might now redirect its efforts in a more productive direction?

No. A good approximation to how Calico operates is as two entities: one that is essentially Genentech 2.0, setting itself up to make massive money from big deals with other traditional pharma, and one that is to pursue its actual remit, namely to defeat aging. Barron was squarely on the former side. The latter side is led by David Botstein, who is as pure a basic scientist as they come and has no time whatsoever for "dreamers" who think we might actually know enough already to be able to develop therapies. His philosophy is unfortunately permanent: no amount of progress will make him become translational and cease to be 100% discovery-focused. I don't remotely blame him - he is who he is. I only slightly blame Levinson: there was nothing wrong with hiring a chief science officer to do discovery, the only thing he got wrong was not also to hire a chief technology officer (me, obviously) alongside him. The people who have all the blame are Larry and Sergey, for allowing their billions to be wasted like this and not having the guts to step in and impose a change of direction.

Given that it's such an emotionally charged field how do you personally, and SENS in general, remain objective and keep hope from interfering with your work?

That's not so hard as you might think. Ultimately, we are driven by the desire to increase the chance of success, or equivalently to reduce the likely time until success - but from what to what is secondary. If we hasten the defeat of aging by a year, who cares whether it's from 2050 to 2049 or from 2030 to 2029? - it's still 40 million lives.

You have been wrong in the past with your expectation of peoples willingness to get onto this idea. Thus I can easily see a path where this technology is proven enough to be clearly happening but most people just don't care and the funding is still very hard to come by. Have you given much thought to this potential scenario?

You're right that I was overoptimistic in the past about the willingness of other high net worth individuals to follow in the wake of Peter Thiel, who started funding us in 2006. However, when it comes to support from scientists, I have never made such a mistake - I always knew it would take robust mouse rejuvenation. I have the advantage in that regard that the community in question is just the most credentialed, authoritative biogerontologists - no one else. Thus, they are (a) really few in number (truly, we are talking about something like a dozen people), (b) scientists (hence I know how they think, unlike billionaires) and (c) people I know well, personally. So I have very strong confidence regarding what determines what they say publicly.

Many wealthy celebrities and smart individuals can easily afford to invest into SENS. How come they are not?

Everyone has rationalisations. The key thing to remember is that humanity has been hoping against hope for a cure for aging since the dawn of civilisation, and it has been suckered time and time again into believing we had one, so there is a rather strong incentive not to get hopes up. And if something is impossible, its desirability is irrelevant: there is still no basis for funding it. So it falls to the small minority of wealthy people who are also truly independent-minded to support this work. Yes, people like Elon Musk may well feel rather ashamed a decade or two from now that they didn't do more earlier. But we're working on it.

How do you feel about the impact of groups like LEAF advocating and reporting on rejuvenation biotech? Has the advocacy and reporting of these groups made your life any easier?

Massively! A huge thing that I say all the time is that advocacy is one thing that absolutely relies upon diversity of messenger. Different people listen to different forms of words, different styles of messaging, etc. The more the better.

Increased Autophagy Improves Stem Cell Activity and Restores Bone Loss in Mice

Researchers here provide evidence for increased autophagy, achieved via targeting mTOR to mimic some of the response to calorie restriction, to improve stem cell function in old mice. As a result some of the loss of bone mass and strength that occurs with age was reversed. Autophagy is the collection of maintenance processes responsible for clearing out broken proteins and structures in the cell, but like most of our biochemistry it declines in effectiveness with age. Increased levels of autophagy have been shown to be necessary for the gains in health and longevity provided by calorie restriction in short-lived species, and mTOR is one of the regulatory genes through which the calorie restriction response works. It is not surprising to find that inhibiting mTOR improves autophagy, and thus also improves the function of many systems in the body that benefit from having less garbage and breakage in their cells.

The overall slowing of aging produced by calorie restriction touches on all aspects and measures of aging, and that includes a reduction in the usual rate of decline in stem cell activity in old age. So the study here illustrates that calorie restriction, stem cell activity, autophagy, and mTOR all link together nicely. Unfortunately, we should not expect the same size of effect in humans as is observed in mice: calorie restriction is very good for health, but it certainly doesn't extend human life span by 40%, as is the case in mouse studies. This is generally the case for all longer-lived species, as the size of the life span increase produced by calorie restriction and its mechanisms under the hood scales down as life span scales up.

Mesenchymal stem cells (MSCs) are pluripotent cells that play crucial roles in tissue maintenance, repair, and regeneration. However, data suggest that beneficial functions of MSCs may become compromised with age; this is closely associated with age-related loss of repair and regenerative capacity of different tissues. Bone marrow-derived mesenchymal stem cells (BMMSCs) decline in number with aging and show degenerative properties including reduced osteogenic differentiation capacity, increased adipogenic differentiation capacity and reduced proliferative ability; these are partially caused by bone aging.

Autophagy is a process in which cellular components such as proteins and damaged mitochondria are engulfed by autophagosomes and delivered to lysosomes to be degraded and recycled in order to maintain cellular homeostasis. Autophagy has been widely studied as a mechanism for anti-aging effects and in alleviating age-related diseases. Recent studies have indicated that autophagy is required for maintaining the stemness and differentiation capacity of stem cells. It has been reported that autophagy is a crucial mechanism in the maintenance of the young state of satellite cells, and failure of autophagy causes declines in the number and function of satellite cells. Autophagy can protect BMMSCs from oxidative stress, which indicates that autophagy plays a protective role in cell aging. Conversely, autophagy also has been proven to be a requirement for maintenance of replicative senescence of MSCs. Therefore, whether and how autophagy regulates MSC aging remains unclear.

Bone marrow-derived mesenchymal stem cells have been regarded as the main source of osteoblasts for skeletal repair. It has been reported that degenerative changes of BMMSCs in humans and rodents during aging are associated with bone aging. Bone marrow-derived mesenchymal stem cells tend to partially lose their self-renewal capacity and differentiate into adipocytes instead of osteocytes with aging, which causes bone loss and fat accumulation. Our findings showed that aged BMMSCs had decreased osteogenesis, elevated adipogenesis and decreased proliferation compared with young BMMSCs; these results are in line with the previous findings.

We speculate that decreased autophagy in aged BMMSCs might be one of the causes of degenerative changes of aged BMMSCs, and bone loss by decreased autophagy could be a potential new mechanism of bone aging. The results of the manipulation of autophagy in both young BMMSCs and aged BMMSCs confirmed our speculations. As an autophagy inhibitor, 3-MA was used on young BMMSCs; the results showed that inhibition of autophagy not only reduced osteogenesis and promoted adipogenesis but also inhibited proliferation of young BMMSCs, which indicated that decreased autophagy could turn young cells into an aged state with degenerative properties. Meanwhile, the autophagy inducer rapamycin could partially convert aged BMMSCs to a young state by increasing osteogenesis, reducing adipogenesis and promoting proliferation. In summary, we conclude that activation of autophagy can restore degenerative properties of aged BMMSCs via regulating oxidative stress and p53 expression.

Link: https://doi.org/10.1111/acel.12709

Covalent Bioscience is One of the Current Crop of SENS Rejuvenation Biotechnology Startup Companies

Covalent Bioscience is the company formed to carry forward work on catalytic antibodies capable of clearing aggregated proteins found in old tissues, such as transthyretin amyloid. This type of amyloid, a misfolded protein that disrupts normal tissue function when present in large enough amounts, is associated with cardiovascular mortality and osteoarthritis, and is thought to be a prevalent cause of death in supercentenarians. The advantage of catalytic antibodies over normal antibodies is that they bind to the target site on a protein, then destroy that site, then move on. One antibody can attack thousands of targets, making low doses potentially highly effective.

Covalent Bioscience is one of a handful of startups and young companies working on science funded in part by the SENS Research Foundation, the foundation for rejuvenation therapies based on repairing and reversing the fundamental cell and tissue damage that causes aging, such as the presence of amyloid. There are a now a number of serious investors and venture firms interested specifically in SENS strategies to treat aging, including figures such as Jim Mellon, Peter Thiel, Michael Greve, James Peyer, and so forth - far more than was the case just a few years ago. This is the time for SENS startup companies to flourish, and gain the funding needed to bring the first batch of rejuvenation therapies to the clinic.

We are a development stage company with intellectual property rights to novel therapeutic antibodies and chemically activated vaccines in all major markets. These rights have been developed from discoveries indicating the power of the immune system to use covalent bonding as the basis for synthesizing antibodies that neutralize and remove target antigens with efficacy and safety superior to conventional antibodies.

The two classes of therapeutic monoclonal antibodies (MAbs) being developed by Covalent, Inc are: (a) irreversible MAbs (iMAbs), which bind and neutralize the target antigen with virtually infinite affinity, (b) catalytic MAbs (cMAbs), which hydrolyze and destroy the target antigen in an enzyme-like manner. Covalent, Inc has proof-of-principle for superior efficacy and diminished side effects of the cMAbs/iMAbs compared to conventional MAbs that bind the target antigen reversibly. Covalent's cMAbs/iMAbs are isolated from the innate immune repertoire that has developed by Darwinian evolution, and immunization with Covalent's electrophilic antigen analogs induces the synthesis of the cMAbs/iMabs adaptively.

Covalent is in a position to generate cMAbs/iMAbs to diverse antigen targets for development as immunotherapies. In addition, Covalent is developing the electrophilic antigen analogs as therapeutic and prophylactic vaccine for unmet medical needs. Covalent has in hand: (a) candidate immunotherapeutic cMAbs to amyloid proteins for treating central nervous system and systemic amyloidosis, and (b) a candidate electrophilic vaccine for treating and preventing HIV infection.

Link: http://www.covalentbioscience.com/

mTOR and the Age-Related Decline in Stem Cell Activity

As a companion piece to an earlier post on the relationship between the mechanistic target of rapamycin (mTOR) gene and cellular senescence in aging, you might take a look at the research here that investigates the relationship between mTOR and the characteristic decline in stem cell activity that occurs with advancing age. In addition to the large body of research focused on insulin and growth hormone metabolism, work on mTOR is among the most active areas of study resulting from investigations of calorie restriction. The practice of calorie restriction has been shown to slow aging in near all species and lineages studied to date, so insofar as the response to calorie restriction is partially mediated through mTOR, we should expect mTOR to have some connection to most of the causes of aging.

Unfortunately, calorie restriction has only a small effect on life span in our species. The research community doesn't yet know exactly how small, but it would be very surprising for it to be greater than five years or so. It would be hard for an effect much larger than that to remain hidden over the length of human history. The health effects are worth it in all other respects; calorie restriction greatly reduces the risk of age-related disease in our species, just as in others. Why are the effects on longevity so much less in humans than in mice? The response to calorie restriction most likely evolved because it grants a greater chance of survival through seasonal famine. The famine is the same length regardless of species, and thus short-lived species evolve under selection pressure to develop a proportionally greater extension of life span, while longer-lived species do not. The result is mice that live 40% longer if they eat less, and humans that do not.

Stem cells of many varied types are responsible for maintaining our tissues in good condition. Their activity declines with age, however, due to some combination of (a) intrinsic damage of the sort listed in the SENS view of aging, and (b) reactions to rising levels of damage elsewhere. It is thought that stem cells become less active with age because this acts to reduce the risk of cancer; the more cells that replicate, the greater the risk that one of those cells acquires mutations that lead to a tumor. That risk rises as the damage of aging grows, as the environment becomes more inflamed and dysfunctional, and the immune system, responsible for destroying potentially cancerous cells, falters. Our life span, longer than that of other primates, came to its present position by balancing the slow decline due to failing tissue maintenance against the fast end due to cancerous growth.

In calorie restricted individuals, the decline in stem cell activity tends to be a little bit slower. So if this effect is in part mediated by mTOR, what exactly is going on under the hood? It is a complex business, trying to reverse engineer the operation of metabolism. Even when it is possible to identify lynchpin genes, such as mTOR, it usually turns out that they are influential in dozens of important low-level cellular operations that can in turn slightly speed or slow the aging process in any number of ways. That just means it is challenging work, however. I think my greater objection to putting such a large focus on this way forward towards potential therapies to treat aging is that, based on what is known of calorie restriction, we shouldn't expect the results in mice to in any way translate to similarly sized results in humans. The effects should be analogous to one another, but in humans the size of those effects will be small.

Inhibiting TOR boosts regenerative potential of adult tissues

In most of our tissues, adult stem cells hang out in a quiet state - ready to be activated in case of infection or injury. In response to such injury, however, stem cells have to be able to rapidly divide, to generate daughter cells that differentiate into cells that repair the tissue. Previous research showed that TOR needs to be maintained at a low level in order to preserve stem cells in a quiet state and prevent their differentiation. But in this study, researchers discovered that TOR signaling becomes activated in many stem cell types when they are engaged in a regenerative response.

This activation is important for rapid tissue repair, but at the same time it also increases the probability that stem cells will differentiate, thus losing their stem cell status. This loss - in this case in the fly intestine, mouse muscle and mouse trachea - is particularly prevalent when the tissue is under heavy or chronic pressure to regenerate, which occurs in response to infections or other trauma to the tissue. During aging, repeated or chronic activation of TOR signaling contributes to the gradual loss of stem cells. Accordingly, by performing genetic or pharmacological interventions to limit TOR activity chronically, the researchers were able to prevent or reverse stem cell loss in tracheae and muscle of aging mice.

Mice were put on differing regimens of the mTOR inhibitor rapamycin starting at different stages of life. Rapamycin was able to rescue stem cells even when given to mice starting at 15 months of age - the human equivalent of 50 years of age. "In every case we saw a decline in the number of stem cells, and rapamycin would bring it back." Whether this recovery of tissue stem cell numbers is due to a replenishment of the stem cell pool from more differentiated cells, or due to an increase in "asymmetric" stem cell divisions that allow one stem cell to generate two new ones, remains to be answered.

mTORC1 Activation during Repeated Regeneration Impairs Somatic Stem Cell Maintenance

The balance between self-renewal and differentiation ensures long-term maintenance of stem cell (SC) pools in regenerating epithelial tissues. This balance is challenged during periods of high regenerative pressure and is often compromised in aged animals. Here, we show that target of rapamycin (TOR) signaling is a key regulator of SC loss during repeated regenerative episodes. In response to regenerative stimuli, SCs in the intestinal epithelium of the fly and in the tracheal epithelium of mice exhibit transient activation of TOR signaling.

Although this activation is required for SCs to rapidly proliferate in response to damage, repeated rounds of damage lead to SC loss. Consistently, age-related SC loss in the mouse trachea and in muscle can be prevented by pharmacologic or genetic inhibition, respectively, of mammalian target of rapamycin complex 1 (mTORC1) signaling. These findings highlight an evolutionarily conserved role of TOR signaling in SC function and identify repeated rounds of mTORC1 activation as a driver of age-related SC decline.

mTOR and Cellular Senescence

Now that the research community has finally woken up to the significance of cellular senescence in aging, a point long advocated for by the SENS Research Foundation and Methuselah Foundation, scientists are busily patching it in to their existing understanding and models of aging. This is just as true for studies of mechanistic target of rapamycin (mTOR) as elsewhere. This is one of the more popular areas of research to emerge from the study of calorie restriction, an intervention that slows aging in near all species tested to date. There is a sizable contingent of researchers interested in finding ways to mimic some fraction of the benefits of calorie restriction through therapies that target mTOR.

Since calorie restriction slows aging, albeit to a much larger degree in short-lived animals than in humans, it is generally agreed that it also slows the accumulation of senescent cells, one of the causes of aging. Thus to the degree that mTOR is involved in the calorie restriction response, we should also expect mTOR to be relevant in some ways to the harms done by cellular senescence: either reducing the number of cells that become senescent, or reducing the harm done by cells once they are senescent. Since we know that calorie restriction doesn't greatly extend life in humans (though it is very good for long term health), we should not expect these effects to be large. Certainly, senolytic therapies that clear out senescent cells should have a much greater positive impact on health and longevity.

The mechanistic target of rapamycin (mTOR) is an evolutionary conserved serine-threonine kinase that senses and integrates a diverse set of environmental and intracellular signals, such as growth factors and nutrients to direct cellular and organismal responses. The name TOR (target of rapamycin) is derived from its inhibitor rapamycin. We now know that the role of mTOR goes far beyond proliferation and coordinates a cell-tailored metabolic program to control cell growth and many biological processes including aging, cellular senescence, and lifespan.

Rapamycin is currently the only known pharmacological substance to prolong lifespan in all studied model organisms and the only one in mammals. Rapamycin was shown to extend the lifespan of genetically heterogeneous mice at three independent test locations by about 10-18% depending on sex. Interestingly, treatment was only started late when the mice were 600 days of age equivalent to roughly 60 years of age in a human person. This proposes that inhibition of mTOR in the elderly might be enough to prolong life. The findings were confirmed and extended in mice, in which rapamycin treatment started earlier. However, they failed to substantially observe larger effects on longevity.

It is now accepted that mTOR inhibition increases lifespan; yet, the mechanism through which this occurs is still uncertain. mTORC1 inhibition may not delay aging itself, but may delay age-related diseases. However, many researchers directly link the longevity effects of mTOR inhibitors to a decrease in aging. Conserved hallmarks of aging have recently been proposed and include telomere attrition, epigenetic alterations, genomic instability, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. The mTOR network is known to regulate some of these aging hallmarks. Ultimately, the prominence of mTORC1 signaling in aging likely reflects its exceptional capacity to regulate such a wide variety of key cellular functions.

Cellular senescence has been suggested to function as a tumor suppressor mechanism and promotor of tissue remodeling after wounding. However, senescent cells may also directly contribute to aging. Senescent cells show marked changes in morphology including an enlarged size, irregular cell shape, prominent and sometimes multiple nuclei, accumulation of mitochondrial and lysosomal mass, increased granularity and highly prominent stress fibers that are accompanied by shifts in metabolism and a failure of autophagy. Interestingly, many of these phenotypes are regulated by mTORC1 in various cell types. The secretion of proinflammatory mediators by senescent cells contributes to aging and has been termed senescence-associated secretory phenotype (SASP). Recent data identified a main role of mTORC1 to promote the SASP. Rapamycin blunts the proinflammatory phenotype of senescent cells by specifically suppressing translation of IL1A.

Despite maintaining a nondividing state, senescent cells display a high metabolic rate. Metabolic changes characteristic of replicative senescence often show a shift to glycolytic metabolism away from oxidative phosphorylation (which is also observed in proliferative cells), despite a marked increase in mitochondrial mass and markers of mitochondrial activity. This might stem from a rise in lysosomal pH as a consequence of proton pump failure, which leads to an inability to get rid of damaged organelles such as mitochondria caused by a failure of autophagy. Dysfunctional mitochondria not cleared by autophagy in senescent cells produce reactive oxygen species, which cause cellular damage including DNA damage. mTORC1 has been postulated as main driver of these metabolic changes. Hence, rapamycin treatment prevents metabolic stress and delays cellular senescence.

Link: https://doi.org/10.1159/000484629

Boosting Mitochondrial Function Reduces Plaque and Improves Cognitive Function in a Mouse Model of Alzheimer's Disease

Mitochondria, the power plants of the cell, suffer a general malaise in older individuals. Their dynamics change and their production of energy store molecules declines. This is distinct and separate from the damage to mitochondrial DNA outlined in the SENS vision for rejuvenation therapies, in that it occurs across all cells rather than in a small but significant number of cells. It is probably a secondary or later consequence of other forms of cell and tissue damage, an inappropriate reaction that makes things worse. This decline in mitochondrial function is implicated in neurodegenerative diseases; the brain requires a great deal of energy to function, and some portion of the changes and symptoms of cognitive decline are due to insufficient energy store production.

Researchers here make some inroads to putting numbers to that portion, at least in mice, but the challenge inherent in the use of animal models of Alzheimer's disease is that they are very artificial. Mice don't normally suffer from Alzheimer's, and their neural biochemistry must be altered significantly in order to produce any of the protein aggregates seen in Alzheimer's disease. The current models only recapture a slice of the full human condition, focusing on amyloid aggregation rather than the full biochemistry of the Alzheimer's. Thus there is always the question for any specific finding as to whether it will also apply to humans, or whether it is a quirk of the model, no matter how plausible the assumptions.

Alzheimer's disease is the most common form of dementia and neurodegeneration worldwide. A major hallmark of the disease is the accumulation of toxic plaques in the brain, formed by the abnormal aggregation of a protein called beta-amyloid inside neurons. Most treatments focus on reducing the formation of amyloid plaques, but these approaches have been inconclusive. As a result, scientists are now searching for alternative treatment strategies, one of which is to consider Alzheimer's as a metabolic disease.

Researchers looked at mitochondria, which are the energy-producing powerhouses of cells, and thus central in metabolism. Using worms and mice as models, they discovered that boosting mitochondria defenses against a particular form of protein stress, enables them to not only protect themselves, but to also reduce the formation of amyloid plaques. During normal aging and age-associated diseases such as Alzheimer's, cells face increasing damage and struggle to protect and replace dysfunctional mitochondria. Since mitochondria provide energy to brain cells, leaving them unprotected in Alzheimer's disease favors brain damage, giving rise to symptoms like memory loss over the years.

The scientists identified two mechanisms that control the quality of mitochondria: First, the "mitochondrial unfolded protein response" (UPRmt), which protects mitochondria from stress stimuli. Second, mitophagy, a process that recycles defective mitochondria. Both these mechanisms are the key to delaying or preventing excessive mitochondrial damage during disease. "These defense and recycle pathways of the mitochondria are essential in organisms, from the worm C. elegans all the way to humans. So we decided to pharmacologically activate them." The team started by testing well-established compounds that can turn on the UPRmt and mitophagy defense systems in a worm model (C. elegans) of Alzheimer's disease. The health, performance and lifespan of worms exposed to the drugs increased remarkably compared with untreated worms. Plaque formation was also significantly reduced in the treated animals.

Most significantly, the scientists observed similar improvements when they turned on the same mitochondrial defense pathways in cultured human neuronal cells, using the same drugs. The encouraging results led the researchers to test in a mouse model of Alzheimer's disease. Just like C. elegans, the mice saw a significant improvement of mitochondrial function and a reduction in the number of amyloid plaques. But most importantly, the scientists observed a striking normalization of the cognitive function in the mice.

Link: https://actu.epfl.ch/news/healthy-mitochondria-could-stop-alzheimer-s/

Does Blood Pressure Decrease in Late Life, and Why Would this Happen?

Blood pressure tends to increase with age, ultimately producing clinical hypertension in a sizable fraction of the population. This is driven by the progressive stiffening of blood vessels, which breaks the finely tuned feedback system that reacts to and controls blood pressure. Stiffening of blood vessels is in turn caused by factors such as calcification and inflammation resulting from cellular senescence, as well as cross-linking in the extracellular matrix that degrades tissue elasticity, and dysfunction of the muscle tissue that controls contraction and dilation of blood vessels. Control of blood pressure is considered highly important in modern medicine, and raised blood pressure is one of the most important factors determining risk of cardiovascular disease and mortality.

Given the justifiable focus on high blood pressure and its consequences, it is interesting to note that there is evidence for blood pressure in the population at large to peak and then drop in later life. As the paper here notes, the simple hypotheses for this phenomenon, such as that people with high blood pressure tend to die at a greater rate before reaching older ages, don't in fact explain enough of the phenomenon. My first guess at a mechanism was weight loss in later life due to frailty and pre-clinical levels of age-related disease, but that also doesn't seem to be enough to explain all of the effect.

A second guess might involve the effects of age-related muscle loss, sarcopenia, on the strength of the heart. This is something that doesn't appear to be all that well studied in older individuals without heart disease, and isn't commented on in the paper here. Unfortunately it isn't a straightforward relationship, given all of the ongoing changes in the cardiovascular system; older patients with either healthy hearts or hearts weakened by heart failure can exhibit higher blood pressure, lower blood pressure, or anything in between depending on their specific circumstances.

Blood Pressure Begins to Decline 14 Years Before Death, Study Says

Researchers looked at the electronic medical records of 46,634 British citizens who had died at age 60 or older. The large sample size included people who were healthy as well as those who had conditions such as heart disease or dementia. They found blood pressure declines were steepest in patients with dementia, heart failure, late-in-life weight loss, and those who had high blood pressure to begin with. But long-term declines also occurred without the presence of any of these diagnoses.

Doctors have long known that in the average person, blood pressure rises from childhood to middle age. But normal blood pressure in the elderly has been less certain. Some studies have indicated that blood pressure might drop in older patients and treatment for hypertension has been hypothesized as explaining late-life lower blood pressures. But this study found blood pressure declines were also present in those without hypertension diagnoses or anti-hypertension medication prescriptions. Further, the evidence was clear that the declines were not due simply to the early deaths of people with high blood pressure.

Blood Pressure Trajectories in the 20 Years Before Death

Both systolic blood pressure (SBP) and diastolic blood pressure (DBP) follow progressive upward trajectories from childhood to middle age, but blood pressure (BP) trends at older ages are unclear. Several studies reported flattening of the upward trend or a decrease in BP at advanced ages, although a few have reported continued BP increases. Blood pressure decreases in older age have been associated with poorer health, onset of dementia, and excess mortality. Hypothesized explanations for BP decreases in later life include (1) advancing age; (2) increasing end-of-life disease, especially heart failure, suggesting a link to the years before death rather than to age; (3) more intensive use of antihypertensive medications; or (4) that excess mortality of hypertensive individuals leaves healthy survivors with lower BP. Data to test these hypotheses are currently limited.

Observing individuals with multiple repeated BP measures over time could help clarify the causes underlying trends. If increasing end-of-life disease explains BP changes, then similar downward BP trajectories should not be observed in age- and sex-matched controls who die much later. In this study, we used the Clinical Practice Research Datalink (CPRD) to estimate clinically measured SBP and DBP trajectories for 20 years prior to death, for individuals dying at 60 years and older. Second, we compared the linear SBP trends for years 10 to 3 years before death in patients who died and age- and sex-matched controls who survived at least 9 years. These approaches aimed to separate age from end-of-life associations, and avoid healthy survivor biases.

Twenty years before death, estimated mean SBPs increased with increasing age at death (60-69 years, 139.5 mm Hg; ≥90 years, 150.0 mm Hg). All age-at-death groups initially experienced increasing SBP, reaching peak values and then declining with proximity to death. Peak SBPs occurred 14 years before death in those dying aged 60 to 69 years (mean peak SBP, 146.3 mm Hg) to 18 years before death for those dying aged at least 90 years (mean peak SBP, 150.8 mm Hg). Overall, 64.0% of individuals experienced SBP decrease of more than 10 mm Hg following the peak.

Antihypertensive medication was prescribed to 85.1% of patients for at least 1 year during the analysis period: mean SBP changed by -20.8 mm Hg from peak to year of death in those treated vs -11.2 mm Hg in those not treated. Peak SBP occurred at a mean of 15 years before death in the treated vs 14 years in those not treated. Adjustment for antihypertensive treatment made little difference to the main model results. Smoking status, alcohol consumption, and levels of physical activity measured in the 20 years prior to death had little association with SBP decreases. Weight loss (the difference between the maximum weight during the first 10 years of follow-up and weight in the final year) findings showed that patients losing at least 20 kg experienced a bigger absolute SBP decrease (mean, -24.87 mm Hg) compared with those who did not lose weight.

More work is needed to elucidate the specific mechanisms involved in late-life BP dynamics. Such studies may also be useful in addressing ways of optimizing the clinical care of older patients who experience decreasing BP. Also, downward BP trajectories before death have the potential to introduce reverse causation or "reverse epidemiology" effects in risk analyses, yielding misleading associations between BP and outcomes in older patients.