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- A Concise Overview of Amyloid-β in Alzheimer's Disease
- Protein Aggregates of Alzheimer's Disease Observed in Aged Dolphins
- A Growing Interest in the Contents of Exosomes in Aging
- The Links Between Mitochondrial Dynamics and Progression of Aging are Complex
- An Interview with Yuri Deigin of Youthereum Genetics: the Merging of an Initial Coin Offering and Pluripotency Factors
- Longevity Industry Whitepapers from the Aging Analytics Agency
- Young Endothelial Cells can be Used to Restore Some Degree of Youthful Behavior in Aged Hematopoietic Stem Cells
- People Underestimate the Burden of Age-Related Frailty and Disease
- Tinkering with Nematode Lifespan Proceeds Apace
- Patterns of MicroRNA Expression as a Biomarker of Aging
- Implicating Wnt/β-catenin Signaling in Age-Related Hair Graying
- The Prospects for Rejuvenation through Targeted Destruction of Senescent Cells
- Towards the Transformation of Scar Tissue to Muscle in the Aged Heart
- Immune Cells Clear Damage to Assist in Nerve Repair
- The Mitochondrial Contribution to Alzheimer's Disease
A Concise Overview of Amyloid-β in Alzheimer's Disease
The open access paper noted here is a fairly concise tour through current thinking on the role of amyloid-β in Alzheimer's disease. Amyloids are solid deposits that appear in aged tissues, a few specific proteins that can misfold or become altered in ways that cause them to clump together and precipitate from solution into fibrils and other structures. Either the amyloid itself or, as in the case of amyloid-β, the surrounding biochemistry prompted by its existence causes harm to cells. Since amyloids are created as a side-effect of the normal operation of cellular metabolism, and since they do in fact cause harm, they can be considered one of the root causes of aging. Why they are found in old tissues rather than young tissues is may be primarily a consequences of failing maintenance systems: problems in the drainage or filtration of cerebrospinal fluid; the progressive dysfunction of immune cells responsible for clearing out unwanted metabolic waste; the progressive failure of recycling mechanisms in long-lived cells.
Given this, it is interesting to consider that the high-profile efforts to reduce levels of amyloid-β in Alzheimer's patients, largely through immunotherapies, were one of the earliest forms of significant work on rejuvenation - though not carried out with that intent. It continues to be the most aggressively funded of all such research, and still not with the intent of rejuvenation, though any sufficiently safe and comprehensive treatment could be repurposed for that use. Unfortunately it has proven very challenging to safely remove amyloid-β through the methodologies chosen to date: despite dozens of clinical trials since the turn of the century, only last year was real progress made with aducanumab. Lack of progress breeds a diversity of other approaches, and so despite the central position of amyloid-β in the consensus on how Alzheimer's progresses and causes harm, many competing views of the condition have come into being over the past decade. Some researchers now focus on inflammation, immune dysfunction, and microbial infections. Others focus on tau protein and neurofibrillary tangles, raising the profile of Alzheimer's as a tauopathy. Still more investigate age-related declines in the drainage of cerebrospinal fluid.
Clearance of amyloid-β remains the primary strategy and where most of the funding goes. It does seem fairly clear that Alzheimer's, like most of aging, has multiple contributing causes. Numerous theories of causation other than amyloid-β have a good deal of solid evidence backing them, particularly tau and microbial infection. Given the challenges inherent in analyzing the complexities of the disease, however, it will require success in removing at least one of the causes to make any serious headway in discussions of either (a) the relative size of various contributions, or (b) which are primary causes versus secondary consequences that cause their own problems.
β-Amyloid and the Pathomechanisms of Alzheimer's Disease: A Comprehensive View
Nascent protein chains, emerging from the ribosomes, need to fold properly into unique 3D structures, eventually translocate and then assemble into stable, functionally flexible complexes. In the crowded cellular environment, newly synthesized polypeptide chains are at risk of misfolding, forming stable, toxic aggregates. These species may accumulate in aged animal cells, especially in neurons and can cause cellular damage inducing cell death. Aggregation of specific proteins into protein inclusions and plaques is characteristic for many neurodegenerative diseases (NDDs), including Alzheimer's disease (AD). Molecular pathological classification of neurodegenerative diseases is based on the presence of these pathologically altered, misfolded proteins in the brain as deposits. The combination of proteinopathies is also frequent.
What is the mechanism of formation of toxic protein aggregates in a living cell? Proteins are structurally dynamic and thus constant surveillance of the proteome by integrated networks of chaperones and protein degradation machineries (including several forms of autophagy) are required to maintain protein homeostasis (proteostasis). NDDs are considered mostly as pathologies of disturbed protein homeostasis. The proteostasis network declines during aging, triggering neurodegeneration and other chronic diseases associated with toxic protein aggregation. In both aging and AD there is a general decrease in the capacity of the body to eliminate toxic compounds. In AD, toxic β-amyloid (Aβ) and hyperphosphorylated Tau (pTau) aggregates may interact with subcellular organelles of the neurons, trigger neuronal dysfunction and apoptosis that lead to memory decline and dementia.
Aging per se is the most important factor of AD and several other neurodegenerative diseases, "the neurobiology of aging and AD is walking down the same road". AD could be seen as a "maladaptive interaction between human brain evolution and senescence". Other authors hypothesized that formation of aggregated proteins might be a protective strategy of the aging neurons. There are numerous hypotheses for understanding the pathogenesis of AD, owing to the multifactorial character of the disease. Some of them (disturbance of the cholinergic system; hypoperfusion, hypoxia in the brain; Ca2+-signalization problems; neuroinflammation; mitochondrial dysfunction; chronic endplasmic reticulum stress and protein misfolding; decreased Aβ-clearance, etc.) are not controversial and could be unified into a general broad hypothesis. The common nominator of these hypotheses is the important role of Aβ in the pathogenesis of AD.
The conventional view of AD is that much of the AD-pathology is driven by an increased load of Aβ in the brain of patients ("amyloid hypothesis"). During the last 15 years many therapeutic strategies were based on lowering Aβ in the brain. Up to now, most of the strategies have failed in clinical trials and the relevance of the amyloid hypothesis has often been questioned. Very recent results show that pathophysiological changes begin many years before clinical manifestation of AD and the disease is a multifaceted process. The core of the amyloid hypothesis stays on and novel clinical trial strategies may hold promise.
In the present review article, we summarize the physiological functions of amyloid precursor protein (APP) and the role of amyloid fragments in adult brain. Then we give a short summary on the genetic background of AD, the interaction of Aβ peptides with subcellular organelles, the pathways of Aβ clearance from the brain, the role of neuroinflammation, brain circulation and the blood-brain-barrier (BBB) in the AD pathogenesis. Finally, we discuss very shortly the major trends in drug discovery and the possibilities for prevention and treatment of AD.
Protein Aggregates of Alzheimer's Disease Observed in Aged Dolphins
What can we learn from the observation that very few other mammalian species exhibit the protein aggregates associated with Alzheimer's disease, the characteristic amyloid-β plaques and tau neurofibrillary tangles? There is debated evidence of amyloid in some primate species other than our own, and a study published earlier this year was the first to claim both amyloid and tau in old chimpanzee brains. Primates do not seem to suffer the widespread death of brain cells that occurs in humans, however, amyloid or no amyloid. In short-lived mammals such as rodents there is little sign of this sort of protein aggregation at all. When researchers are said to study Alzheimer's disease in mice, they are in fact studying one of a number of very artificial biochemistries, genetically engineering lineages given conditions that resemble Alzheimer's in some ways - but these conditions are not actually Alzheimer's. Alongside the enormous complexity of the biochemistry involved, with mapping of the brain and the cell taking place alongside investigation into its failure with age, this artificiality of the mouse models, the fact they are so very different from human Alzheimer's, is one of the reasons why there is a high rate of failure in moving from animal research to human medicine in neurodegenerative research.
In the research noted here, the authors show evidence for dolphins to exhibit both amyloid and tau, making them only the second mammalian species for which this the case. The publicity materials claim it to be the only species, but this is fair enough given that it is only a couple of months since the chimpanzee research was published - that sort of outdated claim is fairly commonplace given that papers can take a year to get through peer review, and months in the final passage to publication. Why humans, dolphins, and chimpanzees, however? Why not mice and horses? This probably ties back in to the question of why longer-lived mammals are longer-lived - what exactly are the biochemical switches and dials involved in this difference? It is of particular interest for our understanding of human evolution because our longevity is comparatively recent, a point of branching from our near primate cousins that may be connected with selection pressures associated with our greater intelligence. Intelligence allows for culture, collaboration, and the Grandmother effect, in which older individuals can help to ensure that their descendants prosper, and thus a longer life is selected for. Should we expect this in dolphins? Data supports the presence of the Grandmother effect in killer whale communities, so it doesn't seem far-fetched.
In the research materials here, it is speculated that some large fraction of the metabolic reactions to calorie restriction, that extend life by up to 40% in mice, have evolved to be switched on all the time in humans and other longer-lived mammals. If the case, this would explain why calorie restriction has only a modest effect on life span in humans - some currently unknown size of benefit that cannot be much larger than a few years, or it would have been noted, measured, and recorded long ago. One counter-argument is that the short term response to calorie restriction in humans is beneficial and looks very similar to that of mice - humans clearly can obtain health benefits through the practice of calorie restriction, and thus perhaps we need to look elsewhere in our biochemistry for an explanation of the sizable difference in outcomes for longevity.
Dolphin brains show signs of Alzheimer's Disease
"It is very rare to find signs of full-blown Alzheimer's Disease in non-human brains. This is the first time anyone has found such clear evidence of the protein plaques and tangles associated with Alzheimer's Disease in the brain of a wild animal." Humans are also almost unique in living long after they are capable of having children; fertility in both men and women declines sharply around the age of 40, but people can go on to live as long as 110 years. Other animals tend to die shortly after the end of their fertile years. Researchers tested the idea that living long after the end of fertility might be linked to Alzheimer's Disease, by studying the brains of another species which can live long after having offspring: dolphins. They found signs of Alzheimer's Disease in the brains of dolphins which had died after washing up ashore on the Spanish coast.
The team analysed 'plaques' of a protein called beta amyloid in the brains of dolphins, as well as tangles of another protein called tau: these plaques and tangles are signatures of Alzheimer's Disease. The team think that humans and dolphins are near-uniquely susceptible to Alzheimer's Disease because of alterations in how the hormone insulin works in these species. Insulin regulates the levels of sugar in the blood, and sets off a complex chemical cascade known as insulin signalling. While alterations in insulin signalling can cause diabetes in people and other mammals, previous scientific work also found that extreme calorie restriction in some animals (e.g. mice and fruit flies) altered insulin signalling - and extended the animals' lifespan by up to three times.
"We think that in humans, the insulin signalling has evolved to work in a way similar to that artificially produced by giving a mouse very few calories. That has the effect of prolonging lifespan beyond the fertile years, but it also leaves us open to diabetes and Alzheimer's Disease. Previous work shows that insulin resistance predicts the development of Alzheimer's Disease in people, and people with diabetes are more likely to develop Alzheimer's. But our study suggests that dolphins and orcas (who also have a long post fertility life span) are similar to humans in many ways; they have an insulin signalling system that makes them an interesting model of diabetes, and now we have shown that dolphin brains show signs of Alzheimer's identical to those seen in people."
Alzheimer's disease in humans and other animals: A consequence of postreproductive life span and longevity rather than aging
Alzheimer's disease and diabetes mellitus are linked by epidemiology, genetics, and molecular pathogenesis. They may also be linked by the remarkable observation that insulin signaling sets the limits on longevity. In worms, flies, and mice, disrupting insulin signaling increases life span leading to speculation that caloric restriction might extend life span in man. It is our contention that man is already a long-lived organism, specifically with a remarkably high postfertility life span, and that it is this that results in the prevalence of Alzheimer's disease and diabetes. We present novel evidence that Dolphin, like man, an animal with exceptional longevity, might be one of the very few natural models of Alzheimer's disease.
A Growing Interest in the Contents of Exosomes in Aging
Exosomes, or extracellular vesicles, are one of the modes by which cells communicate. They are tiny membrane-wrapped packages of signal molecules, constantly secreted and ingested by any population of cells - though note that exosomes are, confusingly, not the same as the larger microvesicles, also membrane-wrapped particles that can carry molecules between cells. Nothing to do with cells is simple or straightforward. In recent years, the falling cost of core biotechnologies has enabled an increasing number of researchers to investigate the contents of exosomes and relate them to specific changes in cellular behavior.
To pick a few examples, exosome signaling is important in the way in which excess fat tissue produces inflammation and metabolic disruption. Researchers are also digging through exosome contents in search of the signals that allow stem cell transplants to produce beneficial effects - it will probably be much more efficient just to deliver the signals themselves. Some groups are adopting an intermediary approach of harvesting and delivering exosomes rather than cells. The specific contents of exosomes definitely change with age, though the details differ for every cell population and process of interest. Senescent cells are one of the root causes of aging, and they produce harmful effects in surrounding cells and tissue structures through inflammatory and other signaling processes - the senescence-associated secretory phenotype. Their exosomes are quite different from those of normal cells, which we might expect to be the case.
The two open access papers I'll point out today touch on the contents of exosomes in a different context, that of neurodegenerative conditions and the age-related decline in cognitive function. These progressive failure modes are all very complex in their biochemistry, largely because the brain is very complex. Simple root causes give rise to end results that are as complex as the surrounding system. Most neurodegenerative conditions have numerous contributing causes and later consequences, tangled up into an unclear mix of layers of only partially understood cause and effect. Changes in cell signaling are certain in there somewhere, along with inflammation, failure of cell maintenance processes, immune system disarray, and growing deposits of uncleared metabolic waste.
Perspective Insights of Exosomes in Neurodegenerative Diseases: A Critical Appraisal
Exosome discovery has exhibited enormous growth over the past three decades. Once known primarily for their role in eliminating excessive cellular proteins and undesirable molecules, exosomes are now known to be required for many physiological processes, such as, the maintenance of normal physiological functions and cell-to-cell communication, and to play important roles in the progression of diseases, such as, cancer and neurodegenerative diseases. Their involvement in neurodegenerative disease progression are attributed to their abilities to transfer biomolecules and pathogenic entities across biological barriers. Furthermore, their abilities to transport proteins and nucleic acids (siRNA, miRNA) have been exploited for the delivery of drugs and other encapsidated biomolecules.
Exosome secretion has been reported for a number of cells in the nervous system. Exosomes have a great effect on cell-to-cell communication, due to: (1) interactions between topical proteins and receptors on target cells; and (2) proteolysis of their cargoes and internalizations of their contents via endocytosis. Furthermore, they allow intercellular communications, via the transport of protein and nucleic acid entities under both normal and diseased states, which suggests exosomes participate in development, cellular function and associated pathologies.
Aggregation of proteins is a hallmark of neurodegenerative diseases, and their accumulations in the central nervous system hinder mitochondrial and proteosomal functions, axonal transport and synaptic transmission and enhance endoplasmic reticulum stress. The ability of exosomes to carry misfolded or aggregated proteins enhances the progression of neurodegenerative diseases. In line with the prion-like spreading hypothesis, their implications in the transmission of infectious particles - prions, amyloid precursor protein, α-synuclein, and superoxide dismutase 1 - between cells in the nervous system are currently being explored.
miRNA in Circulating Microvesicles as Biomarkers for Age-Related Cognitive Decline
Neuroimaging, genetics, and circulating biomarkers are being developed to differentiate normal aging from diseases that affect cognition. While genetic markers may suggest susceptibility to disease, these gene markers are not diagnostic. Similarly, more accurate techniques for identifying pathology, such as positron emission computed tomography, are expensive and may miss early diagnosis, which is critical for treatment. Due to the relative ease of collecting blood, blood based biomarkers could provide a simple and relatively inexpensive means for tracking the progression of cognitive decline and effectiveness of treatments, as well as providing information on mechanism for cognitive impairment. Recent research suggests that non-coding RNAs found in the circulation can act as biomarkers for diseases of aging including cancer, cardiovascular and neurodegenerative disease.
Within the circulation, microRNAs (miRNAs) can be found attached to proteins or in extracellular vesicles, small (50 nm to 1 μm) vesicles of endocytic origin that are released from cells into the extracellular environment. Some (e.g., exosomes) are able to cross membranes (e.g., blood-brain barrier) and can be detected in bodily fluids including serum, urine, and saliva. In this way, microvesicles can provide intercellular and inter-organ communication by delivery of miRNAs to influence transcription and altering genetic processes. Indeed, studies suggest that circulating levels of miRNAs in plasma or in exosomes may be able to identify Alzheimer's disease.
In the current study, we describe miRNAs associated with extracellular microvesicles from plasma as possible biomarkers of cognitive decline during aging. Community dwelling older individuals from the North Florida region were examined for health status and a comprehensive neuropsychological battery, including the Montreal Cognitive Assessment (MoCA), was performed on each participant. A subpopulation (58 females and 39 males) met the criteria for age (60-89) and no evidence of mild cognitive impairment. Despite the stringent criteria for participation, MoCA scores were negatively correlated within the limited age range.
A decrease in MoCA score was associated with increased expression of several miRNAs. The rise in expression of brain selective miRNA could signify conditions in the brain, such as aberrant neural activity, damage, or disease, that result in increased synthesis or release from the brain and a decline in function. In addition, it is possible that highly expressed miRNA are delivered to the brain from the circulation, to influence brain function. The miRNA biomarkers from plasma microvesicle exhibited an expression profile, which was different from that previously described for Alzheimer's disease, suggesting that these biomarkers may be specific to cognitive decline in normal aging.
The Links Between Mitochondrial Dynamics and Progression of Aging are Complex
Every cell contains hundreds of mitochondria, a highly dynamic population of bacteria-like structures responsible for generating the energy store molecule ATP, used to power cellular processes, and that take part in the operation of many of those cellular processes in other ways as well. They are bacteria-like because they evolved from symbiotic bacteria, and still have a remnant of their original DNA. Mitochondria constantly divide, fuse together, are culled by cellular quality control mechanisms, and promiscuously swap their DNA and component parts with one another. Cells even exchange mitochondria. All of this makes mitochondria very challenging to study: they don't stand still to be counted and assessed. Any yet the changes that take place in mitochondria over the course of a lifetime appear very important as a determinant of aging and age-related disease. So difficult or no, the research community must better understand how mitochondria contribute to aging and how that contribution can be turned back.
There are at least two quite distinct classes of process taking place in mitochondria. Firstly there is the damage to mitochondrial DNA that produces dysfunctional mitochondria that can take over cells and make them dysfunctional as well. This involves large deletion mutations, happens as a result of the normal operation of cellular metabolism, and produces a small population of problem cells that pollute the surrounding tissue with oxidized, damaged molecules. This is familiar to those who follow SENS rejuvenation research, as it is here that the recommended intervention takes place: copying mitochondrial DNA into the cell nucleus to provide a backup source of protein machinery to keep the mitochondria from malfunctioning the the harmful way that contributes to the aging process.
The second class of process is much more complex, and involves changes in mitochondrial dynamics of fusion and fission, population size, shape of mitochondria, and energy production. From a SENS point of view, these are secondary and later effects that take place as a consequence of other primary forms of damage and change in aging: cells and their components react, and often in ways that make things worse. All of these mitochondrial changes are comparatively poorly understood as a holistic process, though there are a great many papers that look at thin slices of the issue. Many age-related conditions, particularly neurogenerative conditions as brain cells require a large supply of energy to function correctly, are associated with failing mitochondrial function as a whole: less energy, disrupted participation in cellular activities, and the character of mitochondrial activity changes in numerous other ways.
Some researchers have attempted to classify some of the zoo of possible states of mitochondrial activity in aged tissues by the degree of fusion and fission taking place, by whether mitochondria are becoming fused and large, or staying small in greater numbers. They are also in search of ways to adjust mitochondrial dynamics by dialing up or down the level of fusion or fission. As the research here makes clear that is a very crude starting point when it comes to understanding a complex situation - whether or not changes to fusion and fission map to better or worse outcomes is dependent on other details. I see this as yet more efforts to tinker with the disease state rather than buckling down to strike at the roots of the problem. To make significant progress, tackle the less complex, better understood roots of aging rather than trying to force a partially understood end state into a slightly less worse configuration. This choice of strategy, and the fact that most research groups take the worse approach, is just as apparent in mitochondrial research as it is elsewhere in the field.
Manipulating mitochondrial networks could promote healthy aging
Manipulating mitochondrial networks inside cells - either by dietary restriction or by genetic manipulation that mimics it - may increase lifespan and promote health, according to new research. The study sheds light on the basic biology involved in cells' declining ability to process energy over time, which leads to aging and age-related disease, and how interventions such as periods of fasting might promote healthy aging. Mitochondria - the energy-producing structures in cells - exist in networks that dynamically change shape according to energy demand. Their capacity to do so declines with age, but the impact this has on metabolism and cellular function was previously unclear. In this study, the researchers showed a causal link between dynamic changes in the shapes of mitochondrial networks and longevity.
The scientists used C. elegans (nematode worms), which live just two weeks and thus enable the study of aging in real time in the lab. Mitochondrial networks inside cells typically toggle between fused and fragmented states. The researchers found that restricting the worms' diet, or mimicking dietary restriction through genetic manipulation of an energy-sensing protein called AMP-activated protein kinase (AMPK), maintained the mitochondrial networks in a fused or "youthful" state. In addition, they found that these youthful networks increase lifespan by communicating with organelles called peroxisomes to modulate fat metabolism.
"Low-energy conditions such as dietary restriction and intermittent fasting have previously been shown to promote healthy aging. Understanding why this is the case is a crucial step towards being able to harness the benefits therapeutically. Our work shows how crucial the plasticity of mitochondria networks is for the benefits of fasting. If we lock mitochondria in one state, we completely block the effects of fasting or dietary restriction on longevity."
Dietary Restriction and AMPK Increase Lifespan via Mitochondrial Network and Peroxisome Remodeling
Mitochondrial network remodeling between fused and fragmented states facilitates mitophagy, interaction with other organelles, and metabolic flexibility. Aging is associated with a loss of mitochondrial network homeostasis, but cellular processes causally linking these changes to organismal senescence remain unclear. Here, we show that AMP-activated protein kinase (AMPK) and dietary restriction (DR) promote longevity in C. elegans via maintaining mitochondrial network homeostasis and functional coordination with peroxisomes to increase fatty acid oxidation (FAO).
Inhibiting fusion or fission specifically blocks AMPK- and DR-mediated longevity. Strikingly, however, preserving mitochondrial network homeostasis during aging by co-inhibition of fusion and fission is sufficient itself to increase lifespan, while dynamic network remodeling is required for intermittent fasting-mediated longevity. Finally, we show that increasing lifespan via maintaining mitochondrial network homeostasis requires FAO and peroxisomal function. Together, these data demonstrate that mechanisms that promote mitochondrial homeostasis and plasticity can be targeted to promote healthy aging.
An Interview with Yuri Deigin of Youthereum Genetics: the Merging of an Initial Coin Offering and Pluripotency Factors
Initial coin offerings (ICOs) are driving most of the light and heat in the blockchain world these days. People are raising enormous sums in cryptocurrencies for ventures with somewhere between little plausibility and ordinary levels of startup plausibility. In many ways it looks a lot like the last years of the internet bubble way back when; there are a lot of parallels. The flows of funding may be driven by some combination of people bypassing Chinese currency controls, early holders of Bitcoins and Ether diversifying their holdings within the blockchain ecosystem, and various large investment concerns whose owners have found they can make a quick buck by flipping blockchain tokens, all of which adds fuel to the fire. As I asked earlier this year, if fairly dubious ventures can pull in tens of millions of dollars doing this, why can't we use this to fund thoughtful, legitimate initiatives in rejuvenation research? The challenge here lies in finding a meaningful use for blockchains and network effects in our world of research and development.
Some groups are forging ahead with that effort. I've mentioned Open Longevity's ICO, in which they seek to fund collaborative human trials of various potential pharmaceutical means to slow aging, but for today the focus is on Youthereum Genetics, a newer venture that also seeks to use an ICO as a mechanism to fund research and development. The Youthereum principals are initially intending to work on a means to deliver pluripotency factors involved in the creation of induced pluripotent stem cells to spur regeneration. A demonstration of this was conducted by a research group and published earlier this year, resulting in health benefits for the progeroid mice often used in early stage aging research. This was somewhat surprising as an outcome: haphazardly inducing cells to become pluripotent in a living organism sounds like a rapid short-cut to cancer.
The next steps will be to try this in normal mice, quantify the most useful dose and delivery method, and continue to watch carefully for evidence of cancer as a side-effect. In the best case this may be a road to a regenerative therapy analogous to stem cell transplants, but that remains to be seen. As in so many areas of research where interesting results may or may not lie ahead, the first question is where the funding for that work will be found. The Youthereum team hope that tapping into the blockchain market is the way to go.
I recently had the chance to chat with Yuri Deigin of Youthereum Genetics, and to ask some questions about his aims. As you can tell he is proceeding from a programmed aging point of view - something that I tend to present as standing in diametric opposition to the more mainstream view of aging as accumulated damage. Possibly oversimplifying, this is the question of whether in aging epigenetic change (a program) causes damage, or whether damage causes epigenetic change (a reaction). A programmed aging point of view leads one to intervene in processes that are, to the accumulated damage point of view, secondary consequences only, and attacking secondary consequences just won't be very effective. We are close to the years in which one side or the other will be definitively proven correct, due to the implementation of specific approaches to the treatment of aging as a medical condition.
Nothing is completely black and white, however, and it is interesting to see the development of areas where theorists from either side of this divide will meet in the middle at approaches to therapies that both will consider potentially useful enough to try, but for different reasons. Some classes of stem cell therapies and efforts to achieve similar effects through changes in signaling or reprogramming cells in situ rather than through delivery of cells are a good example of the type. From a programmed aging point of view, these are levers with which to change epigenetic signaling to more youthful levels, while from an accumulated damage point of view, they could be essentially compensatory in nature, like stem cell therapies, but picking the slack to some degree for native regenerative processes that are hampered by damage.
Why Youthereum Genetics, and why now? Who are you, and how did this organization come to be?
I am a Russian-Canadian transhumanist longevity activist, amateur theoretical biologist, and a biotech entrepreneur. Previously, those areas of my life did not intersect, but in the past few months the stars have aligned to prompt me to finally combine my passion and expertise, and channel them into an undertaking I consider the most important in my life: curing aging. Or - getting off the high horse - at least developing some significant life extension therapies for humans, because at the moment there are none. By "significant" I mean something that can prolong our lives by at least 30%. No therapy outside of caloric restriction has been able to achieve this milestone even in mice - not rapamycin (26%), not metformin (14%), not telomerase (24%), not senolytics (26%) or any other 'geroprotector'. And caloric restriction which holds the record for non-genetic lifespan extension (up to 50% in various rodents) failed to produce anywhere near as spectacular a result in primates. In the two macaque studies conducted on CR, at most a 10% median lifespan increase was observed in females and in some groups CR actually shortened lifespan.
Personally, I believe that the reason behind this inability to put a significant dent in aging in the past 50+ years lies in its programmed nature. Over the years, I have seen plenty of evidence in support of this hypothesis with the most convincing being results from parabiosis and young plasma experiments. I think that aging is ultimately controlled by the hypothalamus, just like all other aspects of ontogenesis. This concept dates back to the 1950s and is described in detail in the works of Dilman, Frolkis and Everitt's. Recent research by Dongsheng Cai and his colleagues provides further evidence for the hypothalamic hypothesis. On the cellular level, aging is most likely both tracked by and executed via epigenetic regulation of gene expression. Several years ago it was first observed that a person's age is highly correlated to his/her epigenetic profile. Later it was recognized that these 'epigenetic clocks' are effective life expectancy predictors, which confirmed that epigenetics is a key component of the aging process. Many organisms were found to have such 'epigenetic clocks' that are highly correlated with both their age and probability of death.
Moreover, Nature knows how to roll back or even completely reset the epigenetic clock. This is done for every new embryo and is most likely the reason why every new animal is born young despite having started as an oocyte cell of the same age as its mother (as mother's oocytes were formed while she herself was still in utero). Finally, experiments with epigenetic rejuvenation which demonstrated that rolling back epigenetics rejuvenates not just individual cells but entire organisms (and prolongs their lifespan) have confirmed that epigenetics is not just a consequence but an important driver or aging. This is where Youthereum Genetics comes in. Based on the recent work of Juan Carlos Izpisua Belmonte's group at Salk, who have shown that periodic induction of OSKM transcription factors can prolong lifespans of progeric mice by up to 50%, we hypothesize that aging can be rolled back by periodic epigenetic rollbacks. Our strategy is aimed at translating this hypothesis into a safe therapy that produces sizable, noticeable rejuvenation in humans.
Why us and why now? In a nutshell, because I grew too tired of waiting for someone else to do it and not seeing anyone step up to the plate. So I put together a team that is capable of designing and overseeing experiments for all the steps involved in first verifying the science behind our hypothesis and then translating it into a therapy should science hold up. The only thing left to do now is a small matter of raising the necessary funding. I am being sarcastic, of course. It is a huge challenge, especially given the amounts required and the associated scientific risks involved. But I am willing to try, even in the face of high odds against.
What is your model for what is going on under the hood in animals transfected with pluripotency factors? Why does it produce benefits?
As I mentioned, I am of the Programmed Aging Witnesses cult. At least that's what some opponents of programmed aging call us. I believe that most if not all forms of various intra- and intercellular damage that we see the body accumulate with age do so because our cells gradually tone down the volume of various damage repair mechanisms. Our cells do so via epigenetic regulation of various genes upon receipt of endocrine signals that originate in the hypothalamus based on circadian rhythms and some sort of an internal clock. We know there is a clock because we can see how finely tuned the timings of various developmental and cyclical processes are - from embryogenesis to puberty to menstrual cycles.
So my belief is that the body has enough capacity for self-repair to function at the level of a 25-year-old for hundreds if not thousands of years, or maybe even longer. If the germ line can do so for billions of years, periodically generating a new organism from scratch, it seems logical to me that just a fraction of those remarkable bodybuilding abilities should be enough to sustain our bodies for much, much longer periods than we see today. So if we find a way to trick our cells into thinking that we are 25, they will function (and get replenished) at the level of a 25 year old regardless of our chronological age. To do so, they would need to have gene expression profiles (epigenetic profiles) typical of 25-year-old humans. And we know from the work of Hannum and Horvath that the epigenetic profiles of 25-year-olds are quite different from profiles of 45- and 65-year-olds.
So when we induce OSKM factors in cells, what I think happens is epigenetic rewinding that is associated with upregulation of various repair mechanisms. It is an empirical fact that induced pluripotent stem cells experience significant rejuvenation that ameliorates virtually all the famous Hallmarks of Aging: telomeres elongate, laminar defects get fixed, mitochondrial function gets restored and so on. There is a great article about this by Vittorio Sebastiano and Tapash Jay Sarkar of Stanford with plenty of details.
That said, one doesn't have to believe in programmed aging to see the potential of epigenetic rejuvenation for life extension purposes. In fact, Aubrey de Grey, who is one of our advisors, despite being a staunch opponent of the programmed hypothesis, also believes epigenetic rollback holds therapeutic promise. In his view, the ability to rejuvenate the aged body by reactivating early-life pathways does not in any way conflict with the idea that aging is unprogrammed and results from the gaps in our anti-aging machinery rather than the presence of actively pro-aging machinery. I would be more than happy to be proven wrong on the underlying mechanisms of epigenetic rejuvenation as long as it provides us with a lifespan extension comparable to that seen in Belmonte's work.
Conversely, why won't this treatment produce an unacceptable level of cancer risk? That is always a concern in this sort of thing.
Absolutely, teratomas are probably the biggest concern of this approach. In fact, before Belmonte showed that there is a Goldilocks zone of OSKM induction that extends lifespan without producing teratomas, cancer risk of this approach was thought to be prohibitive for its translation. Apparently, it isn't. The trick is to roll the cells back ever so slightly to prevent them from de-differentiation, but to do so often enough to prevent (or at least slow down) the accumulation of age-related damage that results from the relentless downregulation of damage repair mechanisms with age.
How does this fit together into your view of aging? What do you expect from this and other efforts in the years ahead? Where would you expect the biggest wins to emerge?
This fits my view of aging like a glove. In fact, the reason I got so excited about Belmonte's results back in February was because before I learned about them, I hypothesized that if we ever learn to roll back epigenetic changes, doing so periodically can provide us with a good enough "hack" to significantly delay aging until we completely decipher its mechanisms and learn to stop them for good. So epigenetic rejuvenation is precisely where I think the biggest gains in life extension could emerge. One other important area that we also plan to explore at Youthereum, albeit in a separate research track, is trying to decode hypothalamic exosome secretions. We think that Dongsheng Cai's latest paper, which showed that 16-months old mice exhibit signs of rejuvenation after a one-time injection with hypothalamic exosomes isolated from cultured hypothalamic neuronal stem cells, is really onto something.
Tell us about your take on how to merge the flow of funds in the blockchain market with the goal of doing something useful in longevity science. So much of what is going on in the ICO space seems a very clumsy effort to bolt one thing, the blockchain, onto another completely unrelated thing that has no logical connection to the blockchain. How are you different?
We are not trying to pretend that we will contribute something to the blockchain infrastructure. We won't, we are a decentralized biotech crowdfunding project that is raising money first and foremost for scientific research. In other words, we are users of the blockchain technology, not its developers. We plan to use it to eliminate any middlemen between us and our funding contributors, and to ensure that all our backers' rights to the therapies we plan to develop are not affected by various governmental red tape - current or future. Those are the two main benefits of decentralization, in our opinion. So we view ICOs as just a more efficient crowdfunding mechanism, even if that makes some blockchain purists cringe. I am not sure why they would cringe, though - by embracing the blockchain paradigm and bringing real-world projects into their realm we are actually validating their technology and greatly expanding its potential user base.
How does Youthereum Genetics differ from Open Longevity, who are trying their own hand at an ICO?
While Mikhail Batin of Open Longevity and I agree that we need more people to do everything possible to develop radical life extension therapies ASAP, we differ on what kinds of interventions could actually produce such life extension. I believe that no therapy that exists today, including any clinically approved drugs, can prolong our lifespans by more than 10%, let alone 30%. So in my view, conducting clinical trials for the Fasting-Mimicking Diet (FMD) or use of statins to see if they have the potential to prolong lifespan is not very useful. Epigenetic rejuvenation, on the other hand, does, in my view, have the potential to prolong our lifespans by over 30% or even much, much greater. That is why I am betting so much of my time and money on it.
If this all goes swimmingly well, and you are buried in funds, with decent animal data on the use of pluripotency factors as a therapy, what next?
Let me try answering this by first describing our research plan. We intend to subdivide it into 3 parallel research tracks: (1) development of an optimal dosing regimen using OSKM factors; (2) search for safer factors of epigenetic rollback that do not lead to complete de-differentiation; (3) creation of the best means of gene delivery, preferably patentable. So our key hypothesis is as follows: in order to reliably rejuvenate the entire body, we need to periodically roll back the epigenetic clock of most cells in the body, if not all cells. Thanks to the work of Belmonte's group, we know that this is possible by delivering OSKM factors (or other transcription factors) into the cell. However, this is a tricky endeavor: roll back too little and you get no sizable effect; roll back too much and you might get cancer, as cells would lose their identity and become pluripotent again. After all, their ability to turn cells back into pluripotent state was the main selection criterion for picking the 4 OSKM factors from the original 24 candidates. So, while OSKM factors are effective and represent a "bird in hand", they are far from ideal for our purposes.
We should strive to find better, safer epigenetic rollback factors; we plan to start by revisiting the remaining 20 factors of Yamanaka's original 24, and also try to use the Oct4 factor alone, since there is evidence that it alone is able to roll back epigenetics and is generally the main "guardian of the epigenetic gates." However, narrowing down the factors is only half of the challenge. Delivering them safely and, ideally, cheaply is the other half. The epigenetic aging program is quite robust even in the face of weekly rollbacks, as demonstrated by Belmonte et al., therefore, obtaining meaningful rejuvenation in humans would most likely require monthly or even weekly induction of epigenetic rollback factors (whether OSKM or otherwise). The most cost-effective way of achieving this would be to integrate a special, normally silent polycistronic cassette containing the genes for the rollback factors into virtually each cell of a patient. Such a cassette would be activated by a unique and normally inert custom agent that would need to be developed separately, and would enable this approach to be patentable. Today such cassettes are activated by, for example, tetracycline or doxycycline. With this approach, the marginal cost of a weekly induction of rejuvenating factors would only be the cost of the induction agent (presumably, a small molecule or a peptide) - comparatively cheap.
In summary, we see the most optimal research plan as a step-by-step, iterative improvement of the already proven approach, the induction of OSKM factors with doxycycline; such a cassette with OSKM factors can be delivered to the body using a lentiviral carrier available on the market today. This will proceed in parallel with the development of an ideal therapy: maximally safe and effective factors activated by a unique, inert, patentable agent. Patentability is crucial for being able to interest Big Pharma in in licensing this therapy upon reaching the IND stage. If the project successfully reaches the IND stage, we believe Big Pharma companies will then be sure to license this therapy to begin clinical studies, first for prevention of atherosclerosis, Alzheimer's disease, diabetes or other age-related indications that anti-aging drugs are using today for regulatory purposes, as aging itself is not yet classified as an indication by the WHO. In a nutshell, that is our plan - get the therapy to the IND stage and then let Big Pharma do what it does best: validate it clinically. We estimate that to get to the IND stage it would take 5-6 years if all goes well.
Longevity Industry Whitepapers from the Aging Analytics Agency
The Longevity International project of the Aging Analytics Agency arises from the Biogerontology Research Foundation / Deep Knowledge Ventures portion of our growing community. The various companies and non-profit initiatives associated with this part of the community - such as In Silico Medicine and the International Aging Research Portfolio - share a focus on data. Those involved are now possessed of quite a lot of information about funding, technologies, and just who is doing what in the research community and market of young biotechnology companies. Thus the Aging Analytics Agency is a consultancy that aims to put to use this domain knowledge of the current field. The intended audience is venture firms and large companies with a newfound interest in medicine to treat aging, currently drawn in to the field by the present flurry of development in senolytics and other areas of rejuvenation biotechnology.
For today, I wanted to point out the Longevity Industry Landscape Overview for 2017, though there are other interesting materials to look through. The perspective of the authors is that of the Hallmarks of Aging rather than the SENS view of the causes of aging, but we can appreciate the points of overlap - the acknowledgement that aging has root cause forms of cell and tissue damage, and that the way forward is to address that damage. If the battle to make progress moves on to a hard-fought, evidence-based argument over which forms of damage are legitimate root causes and how best to tackle them, then that is a big improvement over the present state of affairs, in which the primary issue is the need to convince many more people that aging is a viable target for medicine at all, and that human rejuvenation is a plausible near future goal if we just put more funding into the right sort of existing lines of research.
The term "geroscience" was coined by the US National Institute on Aging, to mean "the field of biological sciences that seeks to understand the role of aging in disease." Of the total $1.6B annual NIA budget, only $183.1M goes to fundamental "Aging Biology", with the majority going to Alzheimer's and particular age-related diseases. The application of fundamental knowledge generated by geroscientists is enabling the development of therapies that prevent and/or reverse the molecular and cellular damage caused by aging. By slowing or reversing the aging process, all age-related diseases can be addressed, leading to a healthy lifespan ("healthspan") extension.
Rejuvenation biotechnology is the translational, clinical, and applied relative of geroscience. This discipline aims to prevent and repair the fundamental damage that causes aging. This damage can include: somatic DNA damage, telomere attrition, transposon-related genomic instability, reduced autophagy and protein turnover, epigenetic drift, stem cell exhaustion, advanced glycation endproducts, and more.
The global population is aging due to longer life (albeit in poor health) and the decision among Westerners to have fewer children. This is a major problem for government healthcare and pension systems. Economists refer to this profound, historically-unprecedented population shift as "The Silver Tsunami." The best way to prevent such a catastrophe for these systems is by slowing or reversing aging itself. Doing so extends the expected healthy lifespan and reduces the number of years each person spends in a socially costly state of chronic ill health and frailty.
The traditional medical model has worked very well for particular acute conditions such as infection and traumatic injury. We are no longer dying from infection, as was the leading cause of death a century ago. Chronic lifestyle and age-related diseases such as cardiovascular disease, cancer, diabetes, stroke, and dementia have become the leading killers in the West. Modern medicine has struggled to address these multifactorial diseases. Given that biological age is the primary risk factor, it makes sense to target the damage that causes aging rather than downstream symptoms.
There are two kinds of drugs: type A, innovative blockbuster, first-in-class, broad market drugs such as statins, antidepressants, and lifestyle drugs; type B, incremental best-in-class or "me too" drugs that offer superior safety or efficacy over existing molecules but do not target a novel biochemical mechanism. Rejuvenation therapy will be of type A. Because everyone ages, anti-aging drugs will have the widest market of any other drug. The disruptive element of rejuvenation biotechnology is that it will displace therapies targeting age-related diseases. Suppose a gene therapy (such as APOE4 or FOXO3A) reverses cardiovascular aging and atherosclerosis. Few will need statin drugs (including atorvastatin, the best selling pharmaceutical in history, generating $125B over 14.5 years for Pfizer). Similarly, why try to selectively kill cancer cells when medicine can repair the DNA damage, quell chronic inflammation ("inflammageing"), and reverse the immune senescence that causes cancer rates to rise so dramatically with age?
Biotechnology and geroscience in particular are on the verge of a Cambrian explosion of breakthrough science that will transform healthcare into an information science capable of improving the human condition more profoundly than even the advent of antibiotics, modern molecular pharmacology, and the Green agricultural revolution. The time-course of this major evolutionary transition and whether we and our loved ones live long enough to benefit from these breakthroughs is dependent upon the choices of the scientific and investment community today.
Young Endothelial Cells can be Used to Restore Some Degree of Youthful Behavior in Aged Hematopoietic Stem Cells
Stem cells reside in a niche composed of other cell types that provide necessary support. Age-related changes in that niche, the accumulation of damage and reactions to that damage, contribute to stem cell decline in later life. Stem cells become less active, and this and other alterations in behavior produce downstream consequences of various sorts. An example is the tendency of old hematopoietic stem cells, responsible for generating blood and immune cells, to create more myeloid and fewer lymphoid daughter cells. This leads to subtle imbalance and dysfunction in the immune system, an additional burden atop the problems caused by the declining rate at which new immune cells are created.
Finding ways to restore the youthful behavior of hematopoietic stem cells is thus an area of interest for the research community. Scientists here show that engineering a less damaged stem cell niche for these hematopoietic stem cells can reverse declining activity, but not the myleoid bias, suggesting that signals of age-related change arriving from beyond the niche are also influential. Other lines of research suggest that chronic inflammation is an important part of the problem, for example, and inflammatory signals can spread widely through the bloodstream. Nonetheless, the results here suggest that delivery of young niche cells as a therapy could restore some degree of lost immune cell production in aged individuals, strengthening the immune system.
Aging of the hematopoietic system is associated with a decline in adaptive immunity, an increased incidence of anemia, and a predisposition to myeloid neoplasms. Hematopoietic stem cells (HSCs) show an increase in immunophenotypically defined cells with age, a decrease in their long-term reconstitution abilities, and a significant increase in myeloid-biased cell output at the expense of lymphopoiesis. These studies clearly describe the cell-intrinsic HSC alterations that lead to aging-related hematopoietic deficiencies. While the cell-autonomous changes in the HSC that promote aging-related changes in hematopoiesis are more well defined, the contribution of the aged bone marrow (BM) microenvironment in promoting aged hematopoietic phenotypes is poorly understood.
The adult BM microenvironment is a highly specialized cellular niche composed of vascular endothelial cells (ECs) and perivascular stromal constituents that support HSC maintenance and hematopoietic homeostasis. Within the BM hematopoietic microenvironment, the vascular endothelium is indispensable for supporting HSC quiescence, self-renewal, and differentiation into lineage-committed progeny. The aged BM microenvironment has also been shown to influence hematopoietic aging in young HSCs. While ECs are a critical component of the HSC niche, the individual role of aged ECs in the process of hematopoietic aging has not been examined. Here, we explore the idea that aged ECs are sufficient to promote aging of young HSCs and that the infusion of young ECs can be exploited to improve age-related hematopoietic deficiencies.
In this study, we used cultured BM-derived endothelium from young and aged mice to evaluate whether an age-dependent dysregulation of the BM endothelial niche is sufficient to disrupt the homeostatic HSC-supportive microenvironment and drive aging-associated hematopoietic phenotypes. Using an established ex vivo cell culture system, we demonstrated that culturing of young hematopoietic stem and progenitor cells (HSPCs) on aged endothelium inhibited long-term HSC repopulating activity in a competitive transplantation setting and promoted a myeloid bias at the expense of B cell and T cell lymphopoiesis. Moreover, aged HSPCs cultured on young endothelium showed a marked increase in hematopoietic reconstitution.
These results extended to endothelial infusions in young and aged mice, in which aged BM-derived ECs failed to support endogenous hematopoietic recovery following myelosuppressive irradiation and imparted a myeloid bias in young mice; conversely, infusions of young ECs enhanced HSC activity and increased B and T cell output in young and aged animals. Moreover, young EC infusions enhanced aged HSC transplantation (HSCT) and overall survival through protection of the endogenous BM vascular niche. This lays the groundwork for the development of cellular therapies that can serve to enhance hematopoietic recovery in the elderly population following myelosuppressive treatments to ultimately protect patients from severe morbidities and mortality associated with the treatment of hematological disorders.
People Underestimate the Burden of Age-Related Frailty and Disease
It could be argued that one of the reasons why people are willing to put aside consideration of rejuvenation research, and the related prospects for therapies to turn back aging, is that most underestimate the burdens of age. They are young enough to not be personally impacted today, and the older people they know don't tend to be all that open about the challenges, the pain, the suffering. No-one wants to be the walking medical catalog in the conversation, but everyone gets to be just that at some point, when it can't be hidden away any more. From a stoic perspective, if being old isn't that bad, and then you die peacefully, then that isn't such a terrible situation to be in. I think many people have exactly this errant view - that being old isn't that bad from a physical and mental perspective. Yet it is, it is. It is just that older people tend to be reserved about their suffering, popular entertainment features fit and happy older folk, and most younger individuals only have to go through the process of brutal disillusionment once, with the decline of their parents. That still leaves much of a life span in which those illusions can be maintained.
The ill health of old age is a formidable sword of Damocles looming over us all, and when it falls down, it typically does not hit just us; the elderly are certainly the primary victims, but their family are collateral casualties. When people lose their health and independence to aging, their families have to go through the pain of seeing their loved ones becoming more and more fragile, sick, dependent, perhaps even demented. Adding insult to injury, the troubles caused by aging don't stop here, because a sick and dependent person needs looking after. Thus, the family of an elderly person needs to step in themselves to take care of their relative; if this is not possible, a nursing home is likely going to be the only option left.
Personally taking care of a sick elder is no joke. It requires patience, effort, and most of all, time. It's a real challenge, especially so for people who have young kids of their own to look after. Let's also not forget that it is emotionally very taxing. The nursing home option may partly solve the problem, because there, somebody else does the caring for you, but telling your elders that you can't take care of them any more isn't the best feeling in the world, for you or for them. This can be a rather costly solution, too and as much as every last penny spent to take care of a loved one is well spent, a typical family only has so many pennies, and just because they need them for grandpa, it doesn't mean they can conjure money out of thin air.
As things stand, when we're going to be old, our dear ones will be faced with the issues above; however, if a decent rejuvenation platform was in place by then, none of these issues would materialize, because we'd be healthy and independent in spite of our age. We would never be a burden on our dear ones, and the time we'd spend together would be quality time for us and for them. Luckily for me, I'm still very far from that stage of life when all your friends of a lifetime keep dying. I like to think that there would be more than one person grieving for my loss, and I believe that would actually be the case for most of us. If we exclude few, rare scenarios, your friends, and family would probably rather have you alive and well than inside a coffin. Thanks to rejuvenation, your spouse, your children, your grandchildren, and your friends may benefit from your presence, life experience, and persona for a much longer time. This would be a benefit for you as well, because you could live through your 80s, 90s, and who knows how much longer, without having to bury a dear friend a few times a year.
Tinkering with Nematode Lifespan Proceeds Apace
There are too many methods of extending life in the nematode worm species Caenorhabditis elegans to mention them all, and too many related research papers arrive each year to note every one. To date all of these approaches involve changing the operation of metabolism in order to slow aging. The paper here is unusual for employing a combination of multiple genetic manipulations, rather than focusing on just one, but is otherwise representative of ongoing efforts to investigate aging by slowing it down in short-lived laboratory species. This sort of work will, I think, have little impact on the development of rejuvenation therapies for human use: those will arise from repairing the forms of molecular damage that causes aging, such as by selectively destroying senescent cells, rather than through alterations in metabolism that gently slow the accumulation of that damage.
Aging is a complex phenomenon influenced by multiple genetic pathways. Aging has been particularly well-studied in C. elegans, where more than 100 genes have been identified that can extend lifespan. Examples of pathways that influence C. elegans lifespan are: 1) control of cellular damage and redox state by mitochondrial activity, 2) protection from bacterial pathogenicity, 3) resistance to cellular stress, 4) caloric restriction and 5) aberrant expression of developmental control genes in old age.
Previous studies have focused on genes and pathways one at a time in order to examine the underlying mechanisms for lifespan extension. Recently, we have investigated the effects of manipulating many of these pathways simultaneously by expressing four transgenes with longevity functions in a transgenic strain. The first longevity transgene was zebrafish ucp2, which has mitochondrial uncoupling activity, a function that is absent from C. elegans. Expression of zebrafish ucp2 extended lifespan by 40% compared to a transgenic control strain. Uncoupling allows protons to leak into mitochondria without producing ATP, thus reducing inner membrane potential. A lower potential attenuates mitochondrial production of free radicals, which reduces free radicals damage accumulation during aging.
The second longevity gene was zebrafish lysozyme, lyz, which has an anti-bacterial function that is not found in C. elegans lysozymes. A strain expressing zebrafish lyz had a lifespan 30% longer than the transgenic control. Worm lifespan is limited by mild pathogenic effects from E. coli, which is used as a food source. Lysozymes degrade the bacterial cell wall and thus are key players against bacterial pathogens. Hence, introduction of a vertebrate lysozyme could extend lifespan by improving innate immunity via reduction of pathogenicity from E. coli.
The third longevity gene was hsf-1, which encodes heat shock transcription factor that induces expression of many stress-resistance genes. Overexpression of hsf-1 extended lifespan 35% compared to the transgenic control. The fourth longevity gene was aakg-2(sta2), which encodes the gamma subunit of AMP activated protein kinase. This is a regulatory signaling molecule that responds to low ATP/AMP ratios and plays a key role in stress response. The sta2 mutation in aakg-2 is a gain-of-function mutation that causes the enzyme to be constitutively active. C. elegans strains expressing aakg-2(sta2) had lifespans that were 45% longer than transgenic controls.
A transgenic strain was generated that expressed all four longevity genes: ucp-2, lyz, hsf-1 and aakg-2(sta2). This strain had a lifespan that was 130% longer than the transgenic control, which is roughly the sum of the effects from each longevity transgene expressed alone. Here, we extend our previous work by manipulating a developmental factor as a fifth component, namely knocking down the HOX co-factor unc-62 (Homothorax) in a strain expressing four longevity genes. RNAi against unc-62 in a wild-type worm has previously been shown to significantly extend lifespan (45%). The mechanism of lifespan extension via unc-62(RNAi) involves reprogramming several developmental pathways. First, unc-62(RNAi) decreases the expression of yolk proteins (vitellogenins) that aggregate in the body cavity in old age, thus reducing protein aggregation in old worms. Second, unc-62(RNAi) results in a broad increase in expression of intestinal genes that typically decrease expression with age, presumably allowing prolonged function in old age.
The quintuply-modified strain has a lifespan that is 160% longer than the transgenic control strain. Additionally, the quintuply-modified strain maintains several physiological markers of aging for a longer time than the transgenic control. Our results support a modular approach as a general scheme to study how multiple pathways interact to achieve extreme longevity.
Patterns of MicroRNA Expression as a Biomarker of Aging
As a complement to the DNA methylation based biomarkers of aging, researchers are also finding that patterns of microRNA levels can serve a similar purpose. These tools offer the potential for a rapid assessment of candidate rejuvenation therapies rather than having to run lengthy life span studies, something that is prohibitively expensive for most research groups even in mice, and entirely out of the question in humans. It is hoped that a generally agreed upon biomarker of aging, a low-cost test that fairly accurately reflects biological age, defined as the burden of cell and tissue damage that causes dysfunction and death, will speed up progress towards the development of rejuvenation treatments. The advent of senescent cell clearance as a viable rejuvenation therapy should greatly help the development and validation of such biomarkers: the two lines of development will support one another.
Human aging is a complex process that has been linked to dysregulation of numerous cellular and molecular processes. Recent studies have revealed that human aging can be characterized by changing patterns of DNA methylation and expression of protein-coding genes. A growing body of research suggests that aging is associated with changes in DNA methylation both genome-wide and at specific C-G dinucleotide (CpG) loci. At the messenger RNA (mRNA) level, a recent meta-analysis of whole-blood gene expression in ~15,000 individuals identified 1497 mRNAs that are differentially expressed in relation to age. An age predictor based on mRNA expression (i.e., mRNA age) highlighted genes involved in mitochondrial, metabolic, and immune function-related pathways as key components of aging processes. The difference between mRNA age and chronological age correlated with many metabolic risk factors including blood pressure, total cholesterol levels, fasting glucose, and body mass index (BMI).
MicroRNAs (miRNAs) are a class of small noncoding RNAs that downregulate protein-coding genes by either cleaving target mRNAs or suppressing translation of mRNAs into proteins. Research in a Caenorhabditis elegans model system revealed changes in miRNA expression in relation to lifespan and longevity. In humans, highly specific miRNA expression patterns are correlated with many age-related diseases including cardiovascular disease and cancer. Recent studies have examined differentially expressed miRNAs in relation to age in whole blood, peripheral blood mononuclear cells (PBMC), and serum. These studies, however, were based on small sample sizes, limiting the power to investigate age-related changes in miRNA expression. We hypothesized, a priori, that it would be possible to create a miRNA signature of age that is predictive of chronological age and that age prediction based on miRNA expression is biologically meaningful and can be used as a biomarker of risk for age-related outcomes including all-cause mortality.
In a previous study, we measured miRNA expression in whole blood from more than 5,000 Framingham Heart Study (FHS) participants. We investigated the heritability of miRNA expression and performed a genome-wide association study (GWAS) of miRNA expression. Our results showed that miRNAs are under strong genetic control. In the present study, we further investigated whole-blood miRNA expression in relation to chronological age in FHS participants. We identified 127 miRNAs that were differentially expressed in relation to chronological age, and performed internal validation by splitting the samples 1:1 into two independent sample sets. An integrative miRNA-mRNA coexpression analysis and miRNA target prediction revealed many age-related pathways underlying age-associated molecular changes. We also defined and evaluated an age predictor based on miRNA expression levels (i.e., miRNA age). Our results indicate that the difference between miRNA age and chronological age is associated with multiple age-related clinical traits including all-cause mortality, coronary heart disease (CHD), hypertension, blood pressure, and glucose levels.
Implicating Wnt/β-catenin Signaling in Age-Related Hair Graying
Researchers here report their evidence for increased Wnt signaling in hair follicles and skin in older mice to be implicated in the age-related graying of hair. They demonstrate accelerated hair graying through gene therapy to increase Wnt signaling in these cell populations, considering that it produces exhaustion in the cell populations responsible for hair pigmentation. It remains to be seen as to whether the reverse effect can be produced via suppression of this pathway in older animals.
Aging is a physiological process associated with progressive structural and functional declines of tissues and organs. The hair follicle is a mini-organ that undergoes repetitive cyclic regeneration, thus supplying an excellent model for aging-associated disorders. Typical hair follicle aging phenotypes can be observed but not limited to several signs, such as irreversible hair loss, hair thinning and graying.
Regenerative hair cycling process in a single hair follicle consists of three consecutive phases including growth phase (anagen), regression phase (catagen) and resting phase (telogen). Hair stem cell activation during telogen to anagen transition is mainly controlled by two reciprocal out of phases mechanisms. These include Wnt/β-catenin signaling pathway, which shows crucially roles in hair regeneration. The other one is Bmp signaling pathway, which is decreased in competent telogen phase compared to the refractory telogen phase, leading to hair regeneration. Melanocyte stem cells share the same niche with hair follicle stem cells. Progress has been made in unveiling regenerative behaviors and differentiation of melanocytes. Melanocyte stem cells are activated coordinately with hair follicle stem cells during hair regeneration. They migrate out from the bulge niche to the hair matrix region, and differentiate into melanocytes which generate melanin to pigment hairs.
There is increasing evidence showing that many morphogenetic pathways play key roles in regulating melanocytes behaviors. Of these, Wnt signaling functions as an important pathway controlling the patterning of melanocytes and influencing the decisions of melanocyte stem cells differentiation to pigment the hairs. Wnt3a induces melanocyte stem cell differentiation in vivo and in vitro. Exogenous Wnt recruits β-catenin and Lef1 to bind the promoter of microphthalmia-associated transcription factor (MITF), which functions as a key gene that governs fates of melanocyte lineage cells. Previous study shows that one of the visible signs of hair follicle aging is hair loss. However, the mechanism of hair graying as the other obvious sign of hair follicle aging remains further investigation. Whether Wnt signaling acts as a positive or negative regulator in hair follicle aging is unclear.
Therefore, in this study, we first compared the hair graying phenotype in young and adult mice. Since the important role of Wnt signaling in aging of other tissues, we examined periodic expression of β-catenin which is the effector of Wnt signaling pathway, in melanocyte lineage cells during hair cycling. We found that β-catenin expression was significantly increased both at 34 month telogen phase skin and 34 month anagen phase skin in aged mice, when compared to young mice. We observed that β-catenin expression is not only increased in the hair follicles of aged mice, but also increased at the dermal microenvironment. To explore the function of Wnt signaling on melanocyte differentiation, we over expressed Wnt10b through adenovirus-mediated expression in vivo or in vitro, through intracutaneous injection of adenovirus into the young adult skin, or by adding them into melanocyte stem cells, respectively. Our results indicate that Wnt signaling promotes differentiation of melanocyte stem cell, exhaustion of which leads to hair graying during aging.
The Prospects for Rejuvenation through Targeted Destruction of Senescent Cells
This popular science article covers some of the high points of current work on methods of clearing senescent cells from old tissues, with a focus on the better funded groups - Unity Biotechnology and the research groups involved in that company. So it omits mention of the long years of advocacy prior to 2011, in which the Methuselah Foundation, SENS Research Foundation, and allies called for work on destroying senescent cells based on the compelling evidence for their role in aging that has existed for decades, and were rebuffed. It also omits mention of the other research groups and companies working in the field. This tends to be the way things go, of course - those who are first to raise significant funding tend to be those guiding the presentation of history.
Regardless, this is an enormously promising area of development, and the first rejuvenation therapies to arrive in the clinic in the years ahead will involve some form of senescent cell clearance. Indeed, adventurous individuals could self-experiment with any of the candidate senolytic drugs today, though I think it wiser to wait a few years for the first human trials to report their results. The article plays up indications of variation and typing in senescent cells - that there are tissue-specific differences that will require different approaches for destruction - but I think the concerns here are overblown. Significant health benefits are being achieved in mouse studies even with only partial clearance via one given method, and the variance is nowhere near as large as is the case in cancerous cells.
Although many cells do die on their own, all somatic cells (those other than reproductive ones) that divide have the ability to undergo senescence. But, for a long time, these twilight cells were simply a curiosity. "We were not sure if they were doing something important." Despite self-disabling the ability to replicate, senescent cells stay metabolically active, often continuing to perform basic cellular functions. By the mid-2000s, senescence was chiefly understood as a way of arresting the growth of damaged cells to suppress tumours. Today, researchers continue to study how senescence arises in development and disease. They know that when a cell becomes mutated or injured, it often stops dividing - to avoid passing that damage to daughter cells. Senescent cells have also been identified in the placenta and embryo, where they seem to guide the formation of temporary structures before being cleared out by other cells.
But it wasn't long before researchers discovered the dark side of senescence. In 2008, three research groups revealed that senescent cells excrete a glut of molecules - including cytokines, growth factors and proteases - that affect the function of nearby cells and incite local inflammation. They described this activity as the cell's senescence-associated secretory phenotype, or SASP: hundreds of proteins involved in SASPs. In young, healthy tissue these secretions are probably part of a restorative process, by which damaged cells stimulate repair in nearby tissues and emit a distress signal prompting the immune system to eliminate them. Yet at some point, senescent cells begin to accumulate - a process linked to problems such as osteoarthritis, a chronic inflammation of the joints, and atherosclerosis, a hardening of the arteries. No one is quite sure when or why that happens. It has been suggested that, over time, the immune system stops responding to the cells.
Surprisingly, senescent cells turn out to be slightly different in each tissue. They secrete different cytokines, express different extracellular proteins and use different tactics to avoid death. That incredible variety has made it a challenge for labs to detect and visualize senescent cells. "There is nothing definitive about a senescent cell. Nothing. Period." The lack of universal features makes it hard to take inventory of senescent cells. Researchers have to use a large panel of markers to search for them in tissue, making the work laborious and expensive. A universal marker for senescence would make the job much easier - but researchers know of no specific protein to label, or process to identify. "My money would be on us never finding a senescent-specific marker. I would bet a good bottle of wine on that."
But there's a silver lining to these elusive twilight cells: they might be hard to find, but they're easy to kill. Senescent cells depend on protective mechanisms to survive in their 'undead' state, so researcher began seeking out those mechanisms. They identified six signalling pathways that prevent cell death, which senescent cells activate to survive. Then it was just a matter of finding compounds that would disrupt those pathways. In early 2015, researchers identified the first senolytics: an FDA-approved chemotherapy drug, dasatinib, which eliminates human fat-cell progenitors that have turned senescent; and a plant-derived health-food supplement, quercetin, which targets senescent human endothelial cells, among other cell types. The combination of the two - which work better together than apart - alleviates a range of age-related disorders in mice.
By now, 14 senolytics have been described in the literature, including small molecules, antibodies and a peptide that activates a cell-death pathway and can restore lustrous hair and physical fitness to ageing mice. So far, each senolytic kills a particular flavour of senescent cell. Targeting the different diseases of ageing, therefore, will require multiple types of senolytics. "That's what's going to make this difficult: each senescent cell might have a different way to protect itself, so we'll have to find combinations of drugs to wipe them all out." For all the challenges, senolytic drugs have several attractive qualities. Senescent cells will probably need to be cleared only periodically - say, once a year - to prevent or delay disease. So the drug is around for only a short time. This type of 'hit and run' delivery could reduce the chance of side effects, and people could take the drugs during periods of good health.
Towards the Transformation of Scar Tissue to Muscle in the Aged Heart
The ability to transform one cell type directly into another has been demonstrated for many combinations of types in the laboratory, at least in principle, if not with the reliability needed to move on to the development of clinical therapies. The types of interest here are the fibroblasts that form scar tissue and the cardiomyocytes of heart muscle. Heart tissue is not very regenerative, and scarring and reduced function follows injury of any sort, especially those arising from the structural failures of age: heart attacks and other forms of cardiovascular disease that can deprive the heart of oxygen and nutrients. With the growing damage of aging it is also the case that regeneration runs awry. The presence of senescent cells and chronic inflammation results in fibrosis, the generation of scar-like collagen structures and raised numbers of fibroblasts rather than the correct maintenance of healthy muscle tissue. What if those fibroblasts could be converted in situ into cardiomyocytes, however?
Reversing scar tissue after a heart attack to create healthy heart muscle: this would be a game-changer in the field of cardiology and regenerative medicine. In the lab, scientists have shown it's possible to change fibroblasts (scar tissue cells) into cardiomyocytes (heart muscle cells), but sorting out the details of how this happens hasn't been easy, and using this kind of approach in clinics or even other basic research projects has proven elusive. Now, researchers have used single cell RNA sequencing technology in combination with mathematical modeling and genetic and chemical approaches to delineate the step-by-step molecular changes that occur during cell fate conversion from fibroblast to cardiomyocyte. The scientists not only successfully reconstructed the routes a single cell could take in this process but also identified underlying molecular pathways and key regulators important for the transformation from one cell type to another.
"We used direct cardiac reprogramming as an example in this study. But the pipelines and methods we've established here can be used in any other reprogramming process, and potentially other unsynchronized and heterogeneous biological processes." When we are babies, embryonic stem cells throughout our bodies gradually change into a variety of highly specialized cell types, such as neurons, blood cells, and heart muscle cells. For a long time, scientists thought these specific cell types were terminal; they could not change again or be reverted back to a state between embryonic and their final differentiated stage. Recent discoveries, though, show it's possible to revert terminally differentiated somatic cells to a pluripotent state - a kind of "master" cell that can self-produce and potentially turn into any kind of cell in the body. Scientists have also figured out how to convert one kind of differentiated somatic cell type into another without detouring through the pluripotent stage or the original progenitor stage.
Direct cardiac reprogramming, a promising approach for cardiac regeneration and disease modeling, involves direct conversion of cardiac non-myocytes into induced cardiomyocytes (iCMs) that closely resemble endogenous CMs. Like any reprogramming process, the many cells that are being reprogrammed don't do so at the same time. "So, at any stage, the cell population always contains unconverted, partially reprogrammed, and fully reprogrammed cells, which makes it difficult to study using traditional approaches. Some of what we found is clinically important. For example, we know that after a heart attack, cardiac fibroblasts around the injured area are immediately activated and become highly proliferative but this proliferative capacity decreases over time. A way to take advantage of the varied cell cycle status of fibroblasts over the progression of a heart attack and its aftermath would certainly broaden the application of cellular reprogramming for patients and optimize outcomes."
The team continued with detailed functional analysis of the top candidate - the splicing factor called Ptbp1. Evidence suggests it as a critical barrier to the acquisition of cardiomyocyte-specific splicing patterns in fibroblasts. The study showed that Ptbp1 depletion promoted the formation of more iCMs. "The new knowledge learned from our mechanistic studies of how a single splicing factor regulates the fate conversion from fibroblast to cardiomyocyte is really a bonus to us. Without the unbiased nature of this approach, we would not gain such fresh, valuable information about the reprogramming process. And that's the beauty of our platform."
Immune Cells Clear Damage to Assist in Nerve Repair
Immune cells are important in regeneration, carrying out numerous tasks and issuing signals in a complex interaction with other cell types to produce coordinated reconstruction after damage. Researchers here find that neutrophils assist in the task of clearing out debris after injury to the nervous system, in addition to the macrophages already known to carry out this task. This may change the focus of a number of efforts to spur greater regeneration by manipulating the behavior of immune cells.
Immune cells are normally associated with fighting infection but in a new study, scientists have discovered how they also help the nervous system clear debris, clearing the way for nerve regeneration after injury. Researchers have now shown that certain immune cells - neutrophils - can clean up nerve debris, while previous models have attributed nerve cell damage control to other cells entirely. "This finding is quite surprising and raises an important question: do neutrophils play a significant role in nerve disorders?" Neutrophils are one of the most common types of immune cells and known to engulf microorganisms, but they are not normally associated with peripheral nerve damage.
Researchers found damaged nerve cells produce a stream of molecular lures that specifically attract neutrophils to injury sites in mice. Damaged mouse sciatic nerves produced hundreds of times the normal amount of two "chemoattractant" molecules, Cxcl1 and Cxcl2, which attach to the surfaces of neutrophils and draw the immune cells into injured tissue. Once at the injury site, the neutrophils engulf cellular debris caused by the nerve damage, tidying up the area so the cells can repair themselves. Without the cellular clearance mechanism, nerves can't properly regenerate after injury.
Previous studies have pointed to immune cells called macrophages as the primary immune cell responsible for engulfing and breaking down nerve debris. The team was studying mice genetically modified to lack a receptor on the surface of macrophages - CCR2 - that helps macrophages hone in on injury sites. "We expected that the clearance would be dramatically inhibited without the receptor. To our amazement, the clearance was unchanged from that in normal mice. The mystery we to solve was how nerve cell debris is cleared in these mutant animals." The experiments included sorting immune cells found at injury sites by molecules on their cellular surfaces, and many hours looking at mouse cells through the microscope. "Though it turns out that several different cells pick up the slack in the absence of macrophages, it was the neutrophil that emerged as a major contributor to debris removal. We also discovered that when we depleted neutrophils, nerve debris clearance was significantly halted in both normal mice and mice lacking a major population of macrophages." Without neutrophils, nerve cells could not properly clear debris.
The findings could open the door for new therapeutics designed to help repair nerve cells damaged by neurodegenerative disease. Results from the new study suggest immunostimulant molecules that target neutrophils at nerve injury sites might enhance clean-up and promote nerve cell repair. Immunostimulant molecules are often used to treat chronic infections and immunodeficiencies, but additional studies will be needed to determine their specificity and effectiveness in the context of neuropathies.
The Mitochondrial Contribution to Alzheimer's Disease
Like many neurodegenerative conditions, Alzheimer's disease is associated with a general reduction in the function of mitochondria. Since these cellular components are responsible for generating energy store molecules to power cellular processes, and since brain cells require a lot of energy to function, it makes sense to find that declines in mitochondrial function are associated with disorders of the brain. Where does this fit into the chains of cause and consequence in aging, however? What causes global mitochondrial failure throughout cell populations?
Evidence suggests that these general mitochondrial declines are due to failing autophagy, the cellular processes responsible for removing damaged and dysfunctional mitochondria. Equally, it is the case that changes in mitochondrial dynamics, occurring for poorly understood reasons as reaction to other changes and damage in aging cells, appear to hinder autophagy. This is all quite distinct from the consensus on aggregation of damaged and misfolded proteins, amyloid-β and tau, as the primary cause of Alzheimer's disease. Until there are reliable methods to remove and repair one or more of these contributions to the condition, it is hard to do more than theorize on their relative importance.
For three decades, it has been thought that the accumulation of small toxic molecules in the brain, called amyloid beta, or in short, Aβ, is central to the development of Alzheimer's disease (AD). Strong evidence came from studying familial or early-onset forms of AD (EOAD) that affect about five percent of AD patients and have associations with mutations leading to abnormally high levels or abnormal processing of Aβ in the brain. However, the "Aβ hypothesis" has been insufficient to explain the pathological changes in the more common late-onset Alzheimer's disease (LOAD).
"Because late-onset Alzheimer's is a disease of age, many physiologic changes with age may contribute to risk for the disease, including changes in bioenergetics and metabolism. Bioenergetics is the production, usage, and exchange of energy within and between cells or organs, and the environment. It has long been known that bioenergetic changes occur with aging and affect the whole body, but more so the brain, with its high need for energy." It has been less clear what changes in bioenergetics are underlying and which are a consequence of aging and illness.
Researchers analyzed the bioenergetic profiles of skin fibroblasts from LOAD patients and healthy controls, as a function of age and disease. The scientists looked at the two main components that produce energy in cells: glycolysis, which is the mechanism to convert glucose into fuel molecules for consumption by mitochondria, and burning of these fuels in the mitochondria, which use oxygen in a process called oxidative phosphorylation or mitochondrial respiration. The investigators found that LOAD cells exhibited impaired mitochondrial metabolism, with a reduction in molecules that are important in energy production, including nicotinamide adenine dinucleotide (NAD). LOAD fibroblasts also demonstrated a shift in energy production to glycolysis, despite an inability to increase glucose uptake in response to the insulin analog IGF-1.
Both the abnormal mitochondrial metabolism and the increase of glycolysis in LOAD cells were disease- and not age-specific, while diminished glucose uptake and the inability to respond to IGF-1 was a feature of both age and disease. "The observation that LOAD fibroblasts had a deficiency in the mitochondrial metabolic potential and an increase in the glycolytic activity to maintain energy supply is indicative of failing mitochondria and fits with current knowledge that aging cells increasingly suffer from oxidative stress that impairs their mitochondrial energy production." Because the brain's nerve cells rely almost entirely on mitochondria-derived energy, failure of mitochondrial function, while seen throughout the body, might be particularly detrimental in the brain.