Progress in SENS Rejuvenation Research Over the Past 15 Years

Reforming and rebuilding an entire field of medical research and development isn't an easy task, and sadly nor is it something that can be achieved overnight. A comprehensive reformation of the aging research community is nonetheless the goal of the SENS initiative, the Strategies for Engineered Negligible Senescence - a way to build rejuvenation therapies that work by repairing forms of cell and tissue damage that cause aging. SENS came into being precisely because aging research was not heading in the right direction: researchers were not attempting to treat aging as a medical condition, influential figures were in fact actively suppressing any sort of impetus in that direction, and where there were glimmerings of hope in the form of a few scientists interested in intervening in the aging process, these individuals were focused on strategies that could not possibly do more than slightly slow down age-related degeneration.

Over the past fifteen years SENS has progressed from a position statement and a vision for the end of aging, a set of ideas and supporting evidence only, to a modestly sized set of research programs that are now producing results, several non-profit foundations, a web of relationships with a outsized influence on the research community, and the clinical development of the first rejuvenation therapies. SENS has come a long way from the first meetings of a few like-minded researchers and advocates, just after the turn of the century. Now many researchers are openly talking about the causes of aging and the construction of therapies to meaningfully treat aging. The old suppression of this topic has crumbled entirely. It remains the case that most researchers are still stubbornly pursuing approaches that cannot have a large effect on human health and life span, but the initial battle to change the direction of the research community has been fought and won. Now it is just an increasingly vocal and public debate over how best to proceed, and here SENS will win in time as therapies that repair age-related molecular damage are proven to be far cheaper, more effective, and more reliable than other efforts.

We have come a long way, but one of the necessary parts of advocacy that I think that our community does poorly is the presentation of this growth and success of past years. There is so much we can point to, and show where and how we came together to make a difference, to change the course of research, to fund and build new advances, to change minds and gather allies. We don't do a good job when it comes to clearly showing the progression from (1) initial idea to (2) non-profit scientific foundations to (3) philanthropic support of research to (4) broader research community participation to (5) proof of concept technology demonstrations to (6) founding of biotechnology companies to (7) venture fundraising to (8) clinical trials of rejuvenation therapies. That long chain now exists nearly end to end for senescent cell clearance as a rejuvenation treatment, and all of the other potential branches of SENS research are underway in some form.

So with that in mind, the following timeline references some of the important developments and advances in rejuvenation biotechnology since the origin of the SENS program, from the slow and incremental start to the present more rapid pace. It is by design a high-level and sparse overview, as I wanted to capture the bigger picture without getting dragged down into the details. Watching early stage progress in research from year to year can be a frustrating process, but as senescent cell clearance demonstrates, once a field reaches the tipping point of viability and support, things then move very rapidly. Further, given that this all started with a few ideas and a little persuasion, it is certainly the case that mountains have been moved over the years, even if it feels all too slow on a day to day basis. There is much more to be done ahead, but all who have participated in the past should feel rightfully proud of what has been accomplished, and what continues to be accomplished today.



  • The Methuselah Foundation is created, and the founders launch the Mprize for longevity science, a research prize aiming to spur greater interest in extending healthy life spans.
  • The first SENS-focused academic conference is held in the UK under the auspices of the International Association of Biomedical Gerontology.


  • The Methuselah Foundation begins to assemble the 300, a core group of donors who go on to be influential in the course of advocacy and development of rejuvenation biotechnology. Their funds power the early work of the foundation, and some start their own initiatives in later years.




  • The Methuselah Foundation expands allotopic expression funding to support a French research group that will go on to establish Gensight Biologics on the strength of this work. The foundation also announces the commencement of research initiatives for most of the other SENS programs: clearing senescent cells, removing metabolic waste such as amyloid and cross-links, and investigation of alternative lengthening of telomeres (ALT) in the context of cancer.
  • The first US SENS conference is held at UCLA.


  • The SENS Research Foundation spins off from the Methuselah Foundation to focus entirely on SENS rejuvenation research.
  • GSK and Pentraxin Therapeutics begin a collaboration to develop a therapy capable of clearing transthyretin amyloid.
  • The Methuselah Foundation makes its first outside investment in the Organovo tissue printing startup.


  • The SENS Research Foundation's yearly budget reaches $1 million. The foundation sets up a laboratory facility in Mountain View, California for ongoing intramural research projects.
  • Jason Hope pledges $500,000 to the SENS Research Foundation to start a research program aimed at developing a viable cross-link breaker for glucosepane in humans.
  • Researchers find that transplanting a young thymus into an old mouse restores immune function and extends life.


  • Aubrey de Grey devotes the majority of his $16.5M net worth to funding SENS research.
  • The SENS Research Foundation is funding either in-house or external research projects in all of the seven strands of SENS rejuvenation research. Some are very early stage, focused on building tools or discovery, while others are building the basis for therapies.
  • The first demonstration of targeted senescent cell clearance is carried out by an independent research group, producing benefits in mice with an accelerated aging condition.
  • The Methuselah Foundation launches the New Organ tissue engineering initiative.


  • Gensight Biologics is founded to commercialize allotopic expression of mitochondrial gene ND4, based on the research program supported initially by the Methuselah Foundation, and later the SENS Research Foundation.
  • The SENS Research Foundation demonstrates bacterial enzymes that can break down 7-ketocholesterol in cell culture.
  • Methuselah Foundation supported tissue printing company Organovo becomes publicly traded on NASDAQ.
  • Covalent Bioscience is founded to advance work on catalytic antibodies (or catabodies) to clear the amyloid associated with Alzheimer's disease.


  • Gensight Biologics raises a $32M series A round.
  • The Methuselah Foundation announces a $1 million research prize for liver tissue engineering as a part of the New Organ initiative. This year the foundation also sponsors organ banking initiatives at the Organ Preservation Alliance.
  • The important Hallmarks of Aging position paper is published, the authors taking a cue from the SENS rejuvenation research proposals, but carving out their own view on damage and repair.
  • Google Ventures launches Calico, adding a great deal of support to aging research with the size and publicity of the investment. Unfortunately Calico goes on to focus on areas of aging research unrelated to rejuvenation.
  • Cenexys is founded to work on the creation of means to selectively destroy senescent cells in aged tissues.


  • The Methuselah Foundation and SENS Research Foundation provide seed funding to launch Oisin Biotechnologies, to develop a method of targeted clearance of senescent cells.
  • The SENS Research Foundation begins the Rejuvenation Biotechnology conference series, bringing together industry and academia to smooth the path for development of rejuvenation therapies.
  • Following the Hallmarks of Aging, leading researchers publish their Seven Pillars of Aging position, again echoing the long-standing SENS view of aging and its treatment.
  • The SENS Research Foundation funds development of catabodies to break down transthyretin amyloid, and the work shows considerable promise.
  • Human Rejuvenation Technologies is founded to commercialize a treatment for atherosclerosis based on SENS Research Foundation LysoSENS program approaches to clearing metabolic waste compounds.


  • The SENS Research Foundation's yearly budget reaches $5 million.
  • The Spiegel Lab at Yale announces a method of creating glucosepane, a vital and to this point missing tool needed to develop glucosepane cross-link breaker drugs. This work was funded by the SENS Research Foundation.
  • A research team demonstrates the first senolytic drug candidates capable of selectively destroying senescent cells. The number of candidate drugs increases quite quickly after this point.
  • Pentraxin Therapeutics announces positive results in a trial of targeted clearance of transthyretin amyloid. Meanwhile, evidence continues to emerge from other groups for transthyretin amyloid to have more of an impact in age-related disease that previously thought.
  • SENS Research Foundation work on sabotaging ALT to suppress cancer receives more attention. Meanwhile progress is reported on the other half of telomere extension blockade, interfering in the operation of telomerase, an area in which a number of groups are participating.
  • The Methuselah Foundation makes a founding investment in Leucadia Therapeutics in order to pursue a novel approach to the effective treatment of Alzheimer's disease.
  • The research program producing catabodies capable of breaking down transthyretin amyloid is transferred to Covalent Bioscience for clinical development.


2017, so far...

Methuselah Fund Launches New Website

The Methuselah Fund is the evolution of the Methuselah Foundation's long-standing activities as an incubator of startups, such as Organovo, Oisin Biotechnologies, and Leucadia Therapeutics. In this initiative, the foundation has built a novel fund structure that is as much focused on acceleration of the non-profit mission to bring aging under medical control as it is on for-profit returns. In recent months long-standing members of our community of philanthropic supporters have been invited to invest to help make this a success. Of note for today is that the fund has just launched its website:

The Methuselah Fund (M Fund) is designed to accelerate results in the longevity field, extending the healthy human lifespan. Our success is measured by financial return on investments and furthering the mission, with the mission being the priority. Our DNA stems from The Methuselah Foundation, which has been working hard during the last 16 years to extend the healthy human lifespan. Our access to the key players in this space is significant and our ability to help our companies thrive is proven.

Our strategies are meant to be accessible to everyone since elegantly simple ideas can move masses. Our portfolio companies are achieving one or more of the our anti-aging strategies. New parts for people: technologies that will create new organs, bones, vasculature (with the probable near-term exception of the brain). Get the crud out: Safely remove senescent and other destructive biological structures, intercellular damage or waste (i.e. amyloid), etc. Restore the rivers: restore the circulatory system to full competence. Debug the code: restore informational integrity and viability of cells. Restock the shelves: replenish building blocks such as stem cells and immune system antibodies. Lust for life: restore the capacity for joy. For instance, rejuvenated senses and athletic competence.

Our portfolio companies include Leucadia Therapeutics and Oisin Biotechnologies. Leucadia Therapeutics has a unique and compelling approach on how to potentially predict, halt and cure early stage Alzheimer's Disease. 25 years of research have focused on plaques and tangles as the cause of Alzheimer's. At Leucadia, it is known that those are pathological effects of a more serious underlying condition. The science allows for the creation of a sophisticated surgical procedure bypassing the small molecule approach that has shown no progress until now. Oisin Biotechnologies' ground-breaking research and technology is demonstrating that one of the solutions to mitigating the effects of age-related diseases is to address the damage resulting from the aging process itself. Oisin is developing a highly precise, DNA-targeting platform to clear senescent cells. Oisin's platform has shown as much as an 80% reduction in senescent cells in cell culture and significant reductions of senescent cell burden in naturally aged mice.


Loss of TDP-43 Points to Microglia as a Cause of Lost Synapses in Alzheimer's Disease

The protein TDP-43 acts as a regulator of autophagy, among other things: more of it means less autophagy. The presence of increased amounts of TDP-43 has been investigated in the context of ALS and frontotemporal dementia, where it appears to cause more dysfunction than would be expected just from a loss of the cellular maintenance processes of autophagy. In this recent research, the focus is instead on Alzheimer's disease, where researchers discovered that reducing TDP-43 levels makes the immune cells called microglia more efficiently clear out the β-amyloid associated with this condition. Unfortunately, microglia are also involved in generation and maintenance of synapses, and loss of TDP-43 turns out to ensure that synapses are removed as well as the amyloid. Overall it seems that the amount of TDP-43 in circulation has a narrow safe range; therapies targeting it would have to be more sophisticated than just a blanket reduction or increase via pharmaceuticals. On the plus side, this research adds to the evidence for changes in microglia behavior to be important in neurodegenerative diseases, and there are many other options when it comes to adjusting the activities of these cells.

For the first time, researchers demonstrate a surprising effect of microglia, the scavenger cells of the brain: If these cells lack the TDP-43 protein, they not only remove Alzheimer's plaques, but also synapses. This removal of synapses by these cells presumably leads to neurodegeneration observed in Alzheimer's and other neurodegenerative diseases. Alzheimer's is a disease in which the cognitive abilities of afflicted persons continuously worsen. The reason is the increasing loss of synapses, the contact points of the neurons, in the brain. In the case of Alzheimer's, certain protein fragments, the β-amyloid peptides, are suspected of causing the death of neurons. These protein fragments clump together and form the disease's characteristic plaques.

In an initial step, the researchers looked at the effect that certain risk genes for Alzheimer's have on the production of the β-amyloid peptide. They found no effect in neurons. This led the researchers then to examine the function of these risk genes in microglia cells - and made a discovery: If they turned off the gene for the TDP-43 protein in these scavenger cells, these cells remove β-amyloid very efficiently. This is due to the fact that the lack of TDP-43 protein in microglia led to an increased scavenging activity, called phagocytosis.

In the next step, researchers used mice, which acted as a disease model for Alzheimer's. In this case, as well, they switched off TDP-43 in microglia and observed once more that the cells efficiently eliminated the β-amyloid. Surprisingly, the increased scavenging activity of microglia in mice led also to a significant loss of synapses at the same time. This synapse loss occurred even in mice that do not produce human amyloid. This finding that increased phagocytosis of microglia can induce synapse loss led researchers to hypothesize that perhaps, during aging, dysfunctional microglia could display aberrant phagocytic activity. The results show that the role of microglia cells in neurodegenerative diseases like Alzheimer's has been underestimated. It is not limited to influencing the course of the disease through inflammatory reactions and the release of neurotoxic molecules as previously assumed. Instead, this study shows that they can actively induce neurodegeneration.


A Review of the Intersection Between Aging Research and Calorie Restriction Research

Below, find linked a very readable review of the intersection between aging research and calorie restriction research. While less so now than a decade ago, it nonetheless remains the case that much of the ongoing research into aging is in fact not concerned with treating aging as a medical condition. It is observational only, an field of programs of investigation and mapping that are quite disconnected from any impetus to improve medical technology. In the other portion of the aging research community, however, the part of more interest to us, in which scientists are aiming at interventions that target the causes of aging, a sizable proportion of funding and initiatives can be traced back to roots in calorie restriction research. This is why this topic shows up so often here and elsewhere.

Interestingly, while interest in calorie restriction research is but a slice of the broader field of aging research, aging has always been a principle focus of calorie restriction research. This came to be an area of interest precisely because calorie restricted laboratory animals reliably live longer, a result first formally published by researchers some eighty years ago. That data languished until the era of genetics and molecular biochemistry arrived, at which point calorie restriction became a tool used to investigate the complexity of cellular metabolism: given two reliably produced states of metabolic operation, a great deal can be learned by looking into the details of the differences. In fact, judging by the behavior of the research community, we should probably consider aging to be viewed as a tool used to investigate the complexity of cellular metabolism. A great deal of the otherwise puzzling reluctance to engage with rejuvenation research, an engineering approach in which comparative ignorance of the progression of aging can be bypassed in order to apply what is already known of the molecular damage that causes aging, might be explained by presuming that most researchers are primarily motivated to produce a comprehensive map of our biochemistry, rather than to produce more effective therapies.

So, given the starting point of calorie restriction, researchers move along chains of cause and effect in cells, mapping proteins and their relationships, comparing old and young, calorie restricted and well fed states. Technologies are spun off as they can be from these investigations, because every research institution is these days embedded in a larger organization that seeks to apply new knowledge in any way possible, but this application is a secondary concern at the point at which new directions are chosen for aging research. Since the primary thrust of the work takes little account of the potential effectiveness of resulting technological applications, we end up with a great deal of effort devoted to developing calorie restriction mimetic drugs that might slightly slow aging, rather than that same effort devoted towards repair technologies capable of rejuvenating the old. This happens because the primary goal for researchers is gathering information about biochemistry, as opposed to bringing aging under medical control. In this, there is a set of fundamental mismatches between the expectations and goals of funding sources, researchers, entrepreneurs, and the public at large.

Aging and Caloric Restriction Research: A Biological Perspective With Translational Potential

The dramatic increase in average life expectancy has led to a rapid rise in the aging population across the globe. Age is a robust and independent risk factor for a range of non-communicable diseases like cancer, diabetes, cardiovascular disease, and neurodegenerative disease, and so it follows that this newfound increase in longevity creates a substantial burden in disease incidence and health care costs. Overwhelming evidence suggests that processes intrinsic to aging contribute to the pathogenesis of age-related diseases. Ongoing international efforts have made great strides in advancing our knowledge of the biology of aging and several "hallmarks" of aging have been identified that may play a causative role in the age-related increase in disease vulnerability.

These last few years have seen a shift in emphasis from the investigation of individual age-related diseases in isolation toward a broader context to define the basic biology of aging. The concept behind the recently coined pursuit of geroscience is that a strategy to delay the aging process itself would decrease vulnerability across the age-related disease spectrum leading to lower morbidity and comorbidity. Indeed the concept that aging might be a suitable drug target in a clinical context is gaining traction and there is considerable effort being applied to bring this idea to fruition. One of the most valuable tools in aging research is caloric restriction (CR), a proven intervention to delay aging and age-related disease. If we could understand what mechanisms are employed by CR to impinge on the aging process we could potentially identify causal networks that contribute to the increase in disease vulnerability as a function of normative aging.

To investigate the translatability of CR's beneficial effects from rodents to primates, three independent rhesus monkey studies were initiated in the late 1980s. The take home message from this joint initiative is that CR delays aging in primates, where lower food intake is associated with improvements in health and survival. The implications of this work are broader, first that aging in primates can be manipulated, supporting the concept that aging is a valuable target for intervention and eventual clinical application, and second, that the mechanisms recruited by CR to impinge on aging will likely have utility in the development of treatments to delay or abrogate age-related disease vulnerability.

With evidence that CR is effective in long-lived species the next question is whether its beneficial effects and mechanistic underpinnings are conserved in humans. The hallmarks of mammalian CR include lower adiposity, increased insulin sensitivity, favorable lipid profiles, and increased levels of the adipose-derived hormone adiponectin. Short-term studies of CR in humans have been conducted as part of the multicenter study CALERIE in 2 phases. In the first phase of CALERIE studies (CALERIE-I), the metabolic effects of 6 or 12 months of CR was evaluated in overweight individuals with a target level of restriction of 20-30%. Favorable changes in body weight, body composition, glucoregulatory function and serum risk factors for cardiovascular disease were reported in CR individuals. These outcomes were consistent with those reported for monkeys on CR. Overall, these studies are highly suggestive that CR's effect on aging is translatable to humans and confirm that nonhuman primates do indeed bridge the gap between human and rodent studies.

CR impinges on multiple signaling pathways that regulate growth, metabolism, oxidative stress response, damage repair, inflammation, autophagy, and proteostasis, to modulate the aging process. The relationship between calorie intake and longevity follows a U-shaped curve, dietary excess and malnutrition both negatively impact survival. Between the extremities there is an inverse linear relationship between lifespan and calorie/energy intake, suggesting that adaptive metabolism is a key component in the response to CR. Caloric restriction as an intervention is likely to be very difficult to implement in humans. Indeed the goal of CR research is to figure out how it works, not to promote it as a lifestyle. In order to gain the beneficial effects of CR without the restriction of calories, a number of nutraceuticals and established drugs are being explored as a means to mimic the effects of CR. The National Institute on Aging (NIA) has created the Interventions Testing Program (ITP) to investigate treatments with the potential to extend lifespan and delay age-related disease and dysfunction. To date several effective compounds have been identified some of which have been used in human clinical applications such as rapamycin (inhibitor of mTOR), metformin (activator of AMPK), and others that are only recently being applied in human studies such as resveratrol (activator of AMPK and SIRT1).

Aging research has entered a very exciting period where traditional scientific approaches to understanding the biology of aging are converging with clinical research and epidemiology. Technological advances in the last few decades have brought aging research to a place that could not even have been imagined back in the days when the establishment of the National Institute on Aging first officially recognized the science of aging. We have already seen the identification of genes and biomarkers associated with healthy aging and exceptional aging, and studies in laboratory animals have laid out a rich framework of factors that have established roles in regulation of longevity.

Outstanding questions include the molecular basis for the role of energy metabolism in aging. How do differences in mitochondrial function create vulnerability to disease? How do defects in mitochondrial efficiency and adaptation arise? To what extent do minor differences in energetic capacity or fuel utilization influence other cellular functions? What networks within the cell are responsive to these relatively small age-related changes? Another important avenue of investigation is the role of lipid metabolism in aging and disease vulnerability. Lipid transport and lipid handling are common themes in human and laboratory aging studies, and differences in lipid metabolism have been strongly implicated in the mechanisms of CR, but how does this translate to a change in disease vulnerability as a function of age?

Taking a broader view, it will be necessary to distinguish between events that are coincident with aging and those that are driving aging. Does aging arise first within discrete systems or is it orchestrated simultaneously across systems? To what extent are failures in individual processes such as repair or induction of senescence responsible for age-related disease vulnerability? To resolve these and other questions future directions must include synergistic collaborative efforts focused on aligning insights from human and laboratory aging studies. Caloric restriction research will also have a role to play, where interdisciplinary approaches can be brought to bear to determine the molecular details of CR's mechanisms and thereby identify the most promising candidate factors for targeted intervention.

The Contribution of Decreasing Cancer Mortality to Gains in Life Expectancy

This study provides an assessment of the impact of improvements in cancer prevention and cancer therapies over the past few decades, based on observed changes in life expectancy. In the opinion of the authors, better prevention is the more important contribution to these results - which doesn't say much for the current high level strategy in cancer research aimed at production of better therapies, given the vast sums devoted to that industry. Because of its focus on cancer, an unusual life expectancy construct is used in this study, considering only ages 40 to 84; cancer has a very low incidence at younger ages, and the risk declines again in late life, both absolutely, and in comparison to other causes of death.

Cancer is surpassing cardiovascular disease (CVD) as the leading cause of death in many high income populations and is projected to become a leading cause of morbidity and mortality worldwide in the coming decades. While substantial progress in reducing mortality from CVD has been shown, equivalent global assessment of cancer remains challenging, requiring a multifaceted and multi-indicator approach. Cancer mortality rates are declining in most highly developed countries, largely due to recent successes in the control of common cancers through programs of effective prevention, early detection, and treatment. In contrast, mortality rates of many types of cancer, including breast cancer and prostate cancer, are still increasing in transitioning countries, or at best stabilizing.

There is a need to quantify and better understand the position of cancer among other leading causes of avoidable death, including CVD, and the specific impact of major cancers as barriers to attaining old age. In this study, we quantify the contributions of changing cancer mortality rates on changes in life expectancy in ages 40-84 (LE40-84) over the period 1981-2010, adjusting for other causes of deaths, while making benchmark comparisons with equivalent gains achieved through the reduction of CVD mortality rates.

Only ages 40-84 were included, as individuals within this age group comprise the majority of cancer cases. In addition, in this age group there is also a lower probability of the causes of death being misreported and the existence of comorbid conditions compared with in those aged 85 or more, reducing bias related to competing causes of deaths. As a sensitivity test, we replicated the analysis for ages 0-39 and found that the contributions of cancer to change in life expectancy are negligible in this age group. Accordingly, LE40-84 throughout this article refers to life expectancy in ages 40-84, the expected number of years lived between ages 40 and 84, whereas we truncated years lived above age 85.

An overall decrease in mortality rates from all causes led to a noticeable increase in LE40-84 over the study period. In particular, very high Human Develpment Index (HDI) populations experienced gains of on average 3.7 and 2.5 years in LE40-84 among men and women, respectively, while respective values for medium and high HDI populations were lower, at 1.1 and 1.4 years. Decline in mortality rates from CVD was the main contributor, accounting for an average of more than 60% and 50% of declines in overall mortality rates in very high and medium and high HDI populations, respectively. Although decreasing overall cancer mortality rates were observed, they were greater in very high HDI populations (declines of 20% and 15% over the 30 year period for men and women, respectively) compared with medium and high HDI populations (4% and 5% decreases, respectively).

The past three decades have been marked by several triumphs in cancer control, which are clearly reflected in our results. For example, the increase in LE40-84 among men can be considered partly the result of corresponding declines in lung cancer mortality rates linked to improved tobacco control measures. Gains in life expectancy from a reduction of stomach cancer mortality rates links socioeconomic advancement to successes in combating infectious diseases through both "unplanned" prevention as well as treatment. In most of the very high HDI populations, the progress seen in terms of reductions in mortality rates from breast, prostate, and colorectal cancer can be related to a broad spectrum of cancer control interventions, including early detection, improved diagnosis, and better access to effective treatment.


Using RNA Regulation to Argue for the Relevance of Transposons in Aging

Of late a number of research groups have argued that transposon activity is a contributing cause of dysfunction in aging. Transposons are sections of genetic material that can move around within the genome, and more of this moving around occurs with advancing age, taking place in a more or less random manner within individual cells. The discussion over whether and why this can be a significant cause of aging is similar to that for stochastic mutational damage in nuclear DNA. Here researchers point to a comparative lack of transposon activity in lower organisms such as hydra, species that exhibit exceptional regeneration and minimal aging, as a point to consider in this debate.

Intense investigation in aging research has led to the identification of over five hundred evolutionarily conserved genes, the mutational or RNA interference-mediated inactivation of which slows down the rate of the aging process in divergent eukaryotic species. While many of these genetic interventions can significantly promote longevity, they are unable to halt aging. Even mutant animals with extreme longevity continue to age, albeit at a diminished rate when contrasted with their corresponding controls. A related problem in aging research is that of the mortality rate, which displays an exponential growth throughout the adult life in numerous animal species. As the accumulation of mutations and harmful metabolic factors, such as reactive oxygen species, causing cellular damage, is known to occur at a nearly constant rate during the lifespan, this has bred speculations regarding potential genetic or metabolic components that are likely to be generated exponentially, and to primarily contribute to aging.

Triggered by unrepaired mutations, genomic instability is a key feature of aging cells. Nonaging biological systems however show either no or only limited signs of genome disintegration. Such potentially immortal systems involve the germline that genetically interconnects the subsequent generations, somatic cancer stem cells with indefinite proliferation capacity, and certain organisms from some 'lower' animal taxa, somatic cells of which display stem cell-like features. The term of 'nonaging cells' refers to cells constituting a tissue that traces an essentially immortal lineage. Nonaging tissues display an indefinite renewal capacity. In nonaging cells, genome integrity remains largely stable during the lifespan.

Genomic instability in aging cells progressively increases during adulthood, thereby limiting their capacity to proliferate and survive. A molecular machinery primarily responsible for maintaining the integrity of genetic material is the Piwi-piRNA pathway. This small RNA-based gene regulatory system operates predominantly in nonaging cells. The pathway was originally discovered in the Drosophila male germline, and established to function in repressing the activity of mobile genetic elements, also called transposable elements (TEs), transposons, or 'jumping genes'. In addition planarian flatworms and freshwater hydra somatically express components of the Piwi-piRNA pathway, rendering the self-renewal ability of their somatic cells apparently unlimited.

In the absence of active Piwi-piRNA pathway components, aging somatic cells tend to increasingly lose heterochromatin, which normally maintains TEs under transcriptional repression. Thus, during adulthood, the gradual release of TEs may generate considerable levels of molecular damage that overwhelm the capacity of the cellular maintenance and DNA repair systems. In addition to their increasing mobilization during adult life, TEs can inactivate genes that function in the repair and maintenance systems, further contributing to the age-associated accumulation of cellular damage. In contrast, the Piwi-piRNA pathway protects the germline and nonaging somatic cells from TE-mediated mutagenesis. Occasional mutations generated by chemical and physical mutagens are effectively recognized and eliminated by cellular maintenance and repair mechanisms.

Alternatively, the Piwi-piRNA pathway may have a different, TE-independent, but as of yet unexplored function to ensure genomic integrity in nonaging cells. For example, the pathway may regulate the transcription of certain key genes via modulating chromatin organization. It is also possible that besides the Piwi-piRNA system, another molecular mechanism operates in nonaging cells to preserve the stability of their genomes. Such a mechanism however has not yet been identified. Nevertheless, the activity of the Piwi-piRNA pathway is a shared feature of all nonaging cells identified so far.


Arguing Against the Appearance of a Limit to Human Life Span in Historical Data

Today I'll point out the latest paper in a debate over whether there are limits to human life span. As everyone in the audience here is no doubt aware, human life expectancy is gently trending upward. Life expectancy at birth is rising at about two years with every decade, while life expectancy at 60 is rising at about a year with every decade. The evidence in support of this trend is robust, thanks to the enormous demographic databases collected over the past few decades. Is this trend approaching any sort of limit to human life span, however? Can historical data even be used to answer that question? This is a much more challenging proposition, as the available data for the oldest humans, the population of supercentenarians older than 110, is sparse. Very, very few people survive to these ages, to the point at which statistical methods operating on this data become ever more dubious with each additional year of age.

Still, people crunch the numbers and try to extract meaning. You might recall that last year, Jan Vijg's group put forward their argument for the data to show there to be a limit to human life span over the years in which that data was collected. It was coupled to some unexpectedly pessimistic commentary on the future development of longevity science, given that Vijg has for some time been counted among those researchers openly in favor of extending healthy life spans by treating aging as a medical condition. The paper sparked some occasionally heated discussion. I don't think the researchers expressed their argument all that well in their publicity materials, and the popular science press then generated more than the usual degree of mess and confusion when they pitched in.

So to the casual observer, it was a little difficult to see whether Vijg and company were making the obvious point, which is that human life span is effectively limited by the present level of medical technology, or whether some more subtle argument was being made. I think it is hard to disagree with the statement that medical technology determines limits to human life span. Where we can debate, given the sparse nature of the evidence to hand, is whether or not there exists one or more mechanisms of aging that have not been impacted in any meaningful way by improvements in medical technology over the past century, and which, on their own, can produce a very high rate of mortality in late life. That circumstance would look a lot like a limit when examining the consequent demographic data.

One mechanism that springs to mind here is the accumulation of transthyretin amyloid, found in one small study to be the majority cause of death in supercentenarians, but which appears to have only a smaller impact on mortality in younger old age - it is implicated in something like 10% of heart failure cases, for example. Can we argue that advances in medicine and public health over the past century have had little to no impact on the accumulation of misfolded transthyretin deposits in tissues, and thus this mechanism acts as a limit on life span? Or do some of these improvements in fact produce an small, incidental reduction in amyloid burden in later life? I think that the evidence to support any of the possible positions on these questions is presently lacking.

Whatever the state of effective limits on life span today, however, the limits on life span tomorrow are determined by progress towards rejuvenation therapies. There are treatments under development that can clear transthyretin amyloid from tissues, for example. The same is true for many of the other forms of molecular damage and waste accumulation that cause aging. Thus any debate over what the present demographics do or do not show is more academic than it might otherwise be. The natural state of human aging, already largely paved over by medicine, will be buried completely, made irrelevant in the decades ahead by the advent of means to repair the damage, restore youthful function, and eventually to indefinitely postpone all of the symptoms of aging.

No detectable limit to how long people can live

Supercentenarians, such as Jeanne Calment who famously lived to be 122 years old, continue to fascinate scientists and have led them to wonder just how long humans can live. A study published last October concluded that the upper limit of human age is peaking at around 115 years. Now, however, a new study comes to a starkly different conclusion. By analyzing the lifespan of the longest-living individuals from the USA, the UK, France and Japan for each year since 1968, researchers found no evidence for such a limit, and if such a maximum exists, it has yet to be reached or identified.

"We just don't know what the age limit might be. In fact, by extending trend lines, we can show that maximum and average lifespans, could continue to increase far into the foreseeable future." Many people are aware of what has happened with average lifespans. In 1920, for example, the average newborn Canadian could expect to live 60 years; a Canadian born in 1980 could expect 76 years, and today, life expectancy has jumped to 82 years. Maximum lifespan seems to follow the same trend. Some scientists argue that technology, medical interventions, and improvements in living conditions could all push back the upper limit. "It's hard to guess. Three hundred years ago, many people lived only short lives. If we would have told them that one day most humans might live up to 100, they would have said we were crazy."

Many possible maximum lifespan trajectories

A recent analysis of demographic trends led to the claim that there is a biological limit to maximum human lifespan (approximately 115 years). Although this claim is not novel - others have also identified a biological 'barrier' at 115 years - the methodology that the authors used is. Here we show that the analysis does not allow the distinction between the hypothesis that maximum human lifespan is approximately 115 years and the null hypothesis that maximum lifespan will continue to increase. The central difficulty with this exercise is accurately extrapolating onwards from a limited, noisy set of data.

Beyond a plateauing of maximum life span, there are other different trajectories that maximum lifespan could follow over time if the null hypothesis (that maximum lifespan will continue to increase) were true, with maximum lifespans continuing to increase to an eventual future plateau or continuing to increase indefinitely. All three models appear equally consistent with the known maximum lifespan data used. How the authors differentiated between these possibilities is important. Their claim rests on their identification of a plateau in the ages of maximum lifespan beginning around 1995. They separated the data into two groups, 1968-1994 and 1995-2006, and modelled each group using linear regression. While the first partition shows a trend for increasing maximum lifespan, the second partition does not. It is this latter partition upon which their conclusions are largely based. This is problematic, because, even within a dataset showing an overall trend for an increase with time, normal variability can generate apparent plateaus and even temporary decreases over small intervals.

Furthermore, the authors do not describe how they identified the lifespan plateau, nor the partition site, indicating that these were products of casual visual inspection. This is a critical point for the validity of their argument because even slight changes to the assumptions that they made can notably alter the results of their analysis, with markedly different outcomes. In conclusion, the analyses do not permit us to predict the trajectory that maximum lifespans will follow in the future, and hence provide no support for their central claim that the maximum lifespan of humans is "fixed and subject to natural constraints". This is largely a product of the limited data available for analysis, owing to the challenges inherent in collecting and verifying the lifespans of extremely long-lived individuals.

A reply from Jan Vijg's research group

The authors of the accompanying comment disagree with our finding of a limit to human lifespan. Although we thank them for alerting us to other work reporting a limit of around 115 years, we disagree with the arguments presented and remain confident in our results. We feel that the scenarios presented, although imaginative, are not informative. They argue that their three different models (which they extrapolate until the year 2300) are not statistically differentiable based on the data available. We used a data-driven approach to identify the trend in the maximum reported age at death (MRAD) by analysing actual data rather than arbitrary simulations; although the authors criticize us for visually inspecting our data, graphing data in order to evaluate the choice of model has long been acknowledged as a useful and important technique by statisticians. Taken together, and in the absence of solid statistical underpinning of various possible future scenarios, we feel that our interpretation of the data as pointing towards a limit to human lifespan of about 115 years remains valid.

This is, it has to be said, exactly the sort of exchange one might expect to see between researchers who are working with a very sparse set of data. It is always interesting to watch the ongoing efforts to better refine, mine, and interpret this data, but it is of limited relevance to the near future of therapies to treat aging. All of the present well-known demographics of later life will be changed greatly for the better as therapies capable of addressing the causes of aging emerge.

A Popular Science Overview of Calorie Restriction Research

This popular science piece covers some of the high points of recent years in the field of calorie restriction research. It is above average for the type, though it has to be said that the bar has been set low by the media in recent years. This long-standing area of research involves quantifying the benefits to health and longevity produced by consuming fewer calories while still obtaining an optimal level of micronutrients, mapping the cellular mechanisms involved, and a search for ways to recreate some of these effects via calorie restriction mimetic drugs rather than diet.

Thanks to advances in medicine and improvements in healthy living, we benefiting from longer lifespans and also experiencing longer "healthspans". So, what do we need to do to enhance the length and quality of our lives even more? Researchers worldwide are pursuing various ideas, but for some researchers, the answer is a simple change in diet. They believe that the key to a better old age may be to reduce the amount of food on our plates, via an approach called "calorie restriction". This diet goes further than cutting back on fatty foods from time-to-time; it's about making gradual and careful reductions in portion size permanently.

Since a foundational study in 1935 in white rats, a dietary restriction of between 30-50% has been shown to extend lifespan, delaying death from age-related disorders and disease. Of course, what works for a rat or any other laboratory organism might not work for a human. Long-term trials, following humans from early adulthood to death, are a rarity. "I don't see a human study of longevity as something that would be a fundable research programme. Even if you start humans at 40 or 50 years old, you're still looking at potentially 40 or 50 more years of study." That's why, in the late 1980s, two independent long-term trials - one at NIA and the other at the University of Wisconsin - were set up to study calorie restriction and ageing in Rhesus monkeys. Not only do we share 93% of our DNA with these primates, we age in the same way too.

They are far from malnourished or starving. Take Sherman, a 43-year-old monkey from NIA. Since being placed on the CR diet in 1987, aged 16, Sherman hasn't shown any overt signs of hunger that are well characterised in his species. Sherman is the oldest Rhesus monkey ever recorded, nearly 20 years older than the average lifespan for his species in captivity. Even into his 30s he would have been considered an old monkey, but he didn't look or act like one. The same is true, to varying extents, for the rest of his experimental troop at NIA. "We have demonstrated that ageing can be manipulated in primates. It kind of gets glossed over because it's obvious, but conceptually that's hugely important; it means that ageing itself is a reasonable target for clinical intervention and medical treatment."

If ageing can be delayed, in other words, all of the diseases associated with it will follow suit. "Going after each disease one at a time isn't going to significantly extend lifespan for people because they'll die of something else. If you cured all cancers, you wouldn't offset death due to cardiovascular disease, or dementia, or diabetes-associated disorders. Whereas if you go after ageing you can offset the lot in one go."

In the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy trial, also known as Calerie, over two years, 218 healthy men and women aged between 21 and 50 years were split into two groups. In one, people were allowed to eat as they normally would (ad libitum), while the other ate 25% less (CR). Both had health checks every six months. Unlike in the Rhesus monkey trials, tests over two years can't determine whether CR reduces or delays age-related diseases. There simply isn't enough time for their development. But the Calerie trials tested for the next best thing: the early biological signs of heart disease, cancer, and diabetes. The results after two years were very positive. In the blood of calorie-restricted people, the ratio of "good" cholesterol to "bad" cholesterol had increased, molecules associated with tumour formation - called tumour necrosis factors (TNFs) - were reduced by around 25%, and levels of insulin resistance, a sure sign of diabetes, fell by nearly 40% compared to people who ate their normal diets. Overall, blood pressure was lower.

With less food, is the metabolism forced to be more efficient with what it has? Is there a common molecular switch regulating ageing that is turned on (or off) with fewer calories? Or is there an as of yet unknown mechanism underpinning our lives and deaths? Answers to such questions might be long in coming. "If I cloned 10 of myself and we all worked furiously, I don't think we'd have it solved. The biology is inordinately complicated." It's a worthwhile undertaking - understand how CR works and other treatments could then be used to target that specific part of our biology. Ageing could be treated directly, that is, without the need of calorie restriction.


Centenarians Suffer from Significantly Lower Rates of Chronic Age-Related Disease than Younger Cohorts

Aging is an accumulation of molecular damage and its consequences. The greater the level of damage, the greater the dysfunction in organs and the immune system, then the closer the individual comes to the arbitrary dividing line at which that dysfunction becomes a formal, named age-related disease. Further, the more damage, the higher the mortality rate. Given this view of aging, it should be no great surprise to find that the longest lived people have a history of comparatively little age-related disease: the only ways to become extremely old are to either (a) have accumulated damage at a slower rate that everyone else, most likely through lifestyle choices, or (b) bear genetic variants that increase resistance to some forms of damage and consequence. In either case, cell and tissue damage, aging, longevity, and age-related disease are all linked together, facets of the same whole.

In a large cohort of predominantly male community-dwelling elderly veterans, centenarians had a lower incidence of chronic illness than those in their 80s and 90s. The centenarian population is one of the fastest growing in the country, according to the United States Social Security Administration. They are predicted to exceed one million by the close of this century, little is known about why this generation has achieved such longevity. In a recent study, researchers looked primarily at octogenarians, nonagenarians, and centenarians within the Veterans Affairs medical system. The sample that they studied comprised mostly of white males that had fought in World War II. "Additionally, this generation lived through the Great Depression. It is a wonder, considering the hardships they had faced, that they have achieved such longevity."

A key factor that the research team observed in these individuals is that, due to their military background, many had a developed sense of discipline and therefore were keen to make healthy decisions; many did not smoke or drink. The team also offered the hypothesis of compression of morbidity as a potential explanation for the extended health span in an individual's life span. The hypothesis states that the lifetime burden of illness could be reduced if the onset of chronic illness is postponed until very late in life, or in other words "the older you get, the healthier you have been."

Ninety-seven percent of centenarians were male, 88.0% were white, 31.8% were widowed, 87.5% served in World War II, and 63.9% did not have a service-related disability. The incidence rates of chronic illnesses were higher in octogenarians than centenarians (atrial fibrillation, 15.0% vs 0.6%; heart failure, 19.3% vs 0.4%; chronic obstructive pulmonary disease, 17.9% vs 0.6%; hypertension, 29.6% vs 3.0%; end-stage renal disease, 7.2% vs 0.1%; malignancy, 14.1% vs 0.6%; diabetes mellitus, 11.1% vs 0.4%; stroke, 4.6% vs 0.4%) and in nonagenarians than centenarians (atrial fibrillation, 13.2% vs 3.5%; heart failure, 15.8% vs 3.3%; chronic obstructive pulmonary disease, 11.8% vs 3.5%; hypertension, 27.2% vs 12.8%; end-stage renal disease, 11.9% vs 4.5%; malignancy, 8.6% vs 2.3%; diabetes mellitus, 7.5% vs 2.2%; and stroke, 3.5% vs 1.3%).


Adjusting Microglia Proportions as a Basis for the Treatment of Parkinson's Disease

The balance between different types of the immune cells known as macrophages is becoming a stronger theme these days, a line of research that falls somewhere into the broad overlap between regeneration, inflammation, and aging. I've seen quite a number of interesting papers on this topic in the past year, which seems to me a leap in the level of interest shown by the research community of late. While possibly oversimplifying a more complicated reality, we can think of macrophages as having a few different types, or polarizations. The M1 polarization tends towards aggressive destruction of problem cells, the creation of inflammation, and hindrance of regeneration. The M2 polarization tends towards suppression of inflammation and other behaviors that encourage regeneration. The cancer research community would like to be able to adjust macrophage populations towards the M1 type, more willing to destroy cancerous cells, while the regenerative medicine community would like to be able to adjust macrophage populations towards the M2 type to spur enhanced regeneration and tissue maintenance.

It may be that the increased interest in macrophage polarization is a function of the emergence of tools that now allow for cost-effective attempts to shift the balance of macrophage types. The infrastructure of biotechnology is advancing rapidly, and progress spurred by falling costs is a common theme in many parts of the field. Today I'll offer up another example of macrophage polarization research, this time involving microglia, a form of macrophage resident in the central nervous system. Changes in microglia have been shown to be important in any number of age-related neurodegenerative conditions: the immune system declines with age in the brain, just as elsewhere in the body, falling into a dysfunctional and inflammatory state. This affects regeneration and tissue maintenance as is the case for macrophages beyond the brain, but microglia also have additional roles in the correct function of neurons and neural connections, an area of our biochemistry that is still comparatively poorly understood. It is possible to achieve benefits for patients by coercing more microglia into the M2, pro-regenerative polarization? In this open access paper, researchers examine the question in the context of Parkinson's disease.

Targeting Microglial Activation States as a Therapeutic Avenue in Parkinson's Disease

A growing body of evidence suggest that neuroinflammation mediated by microglia, the resident macrophage-like immune cells in the brain, play a contributory role in Parkinson's disease (PD) pathogenesis. In the central nervous system (CNS), the innate immune response is predominantly mediated by microglia and astrocytes. Microglia play a vital role in both physiological and pathological conditions. Microglia appear to be involved in several regulatory processes in the brain that are crucial for tissue development, maintenance of the neural environment and, response to injury and promoting repair. Similar to peripheral macrophages, microglia directly respond to pathogens and maintain cellular homeostasis by purging said pathogens, as well as dead cells and pathological gene products.

Microglia participate in both physiological and pathological conditions. In the former, microglia restore the integrity of the central nervous system and, in the latter, they promote disease progression. Microglia acquire different activation states to modulate these cellular functions. When classically activated, microglia acquire the M1 phenotype, characterized by pro-inflammatory and pro-killing functions that serve as the first line of defense. The alternative M2 microglial activation state is involved in various events including immunoregulation, inflammation dampening, and repair and injury resolution.

Upon activation to the M1 phenotype, microglia elaborate pro-inflammatory cytokines and neurotoxic molecules promoting inflammation and cytotoxic responses. In contrast, when adopting the M2 phenotype microglia secrete anti-inflammatory gene products and trophic factors that promote repair, regeneration, and restore homeostasis. Relatively little is known about the different microglial activation states in PD, and the distribution of microglial M1/M2 phenotypes depends on the stage and severity of the disease. Understanding stage-specific switching of microglial phenotypes and the capacity to manipulate these transitions within appropriate time windows might be beneficial for PD therapy. The transition from the M1 pro-inflammatory state to the regulatory or anti-inflammatory M2 phenotype is thought to assist improved functional outcomes and restore homeostasis. The induction of M1 phenotype is a relatively standard response during injury. For peripheral immune cells it is thought that M1 polarization is terminal and the cells die during the inflammatory response. Although a shift from M1 to the M2 phenotype is considered rare for peripheral immune cells, microglia can shift from M1 to M2 phenotype.

To inhibit the pro-inflammatory damage through M1 activation of microglia, its downstream signaling pathways could be targeted. The M1 phenotype is induced by IFN-γ via the JAK/STAT signaling pathway and targeting this pathway may arrest M1 activation. In fact, studies show that inhibition of the JAK/STAT pathway leads to suppression of the downstream M1-associated genes in several disease models. Another approach to suppress M1 activation would be to target the pro-inflammatory cytokines such as TNF-α, IL-1β and IFN-γ, and decrease its ability to interact with its receptors on other cell types. Alternatively, molecules with the capability to activate the anti-inflammatory M2 phenotype or promote the transition of pro-inflammatory M1 phenotype to anti-inflammatory M2 could be useful in the treatment of PD. Anti-inflammatory molecules such as IL-10 and beta interferons produce neuroprotection by altering the M1 and M2 balance.

The critical role of microglia in most neurodegenerative pathologies including PD is increasingly documented through many studies. Until recently, microglial activation in pathological conditions was considered to be detrimental to neuronal survival in the substantia nigra of PD brains. Recent findings highlight the crucial physiological and neuroprotective role of microglia and other glial cells in neuropathological conditions. Studies on anti-inflammatory treatments targeting neuroinflammation in PD and other diseases by delaying or blocking microglial activation failed in many trials due to the lack of a specific treatment approach, possibly the stage of disease and an incorrect understanding of mechanisms underlying microglial activation. With the updated knowledge on different microglial activation states, drugs that can shift microglia from a pro-inflammatory M1 state to anti-inflammatory M2 state could be beneficial for PD. The M1 and M2 microglial phenotypes probably need further characterization, particularly in PD pathological conditions for better therapeutic targeting. We support targeting of microglial cells by modulating their activation states as a novel therapeutic approach for PD.

Evolutionary Trade-Offs in Stem Cell Populations: Repair Capacity versus Cancer Risk

This open access paper is an interesting companion piece to yesterday's discussion of the potential for expansion of mutations in stem cell populations to contribute to degenerative aging. What evolutionary constraints have led to the present state of stem cell populations in mammals: why are they not larger, with more capacity for tissue maintenance and regeneration in later life, for example?

Multicellular organisms continually accumulate mutations within their somatic tissues, constituting a significant, but poorly quantified, burden on tissue maintenance. To investigate this burden in a specific, well-parameterized context, we model the mammalian intestine and quantify the expected impact of mutation accumulation in stem cell populations. Furthermore, we explore how the population size of the stem cell niche influences mutation accumulation and demonstrate the expected trade-off between the risk of accumulating deleterious mutations, population size, and the risk of tumorigenesis. However, we further characterize how this trade-off can be expected to manifest over the lifetime of two well-studied mammalian systems, mice and humans, by estimating the expected effect of mutation accumulation on cellular homeostasis.

The intestinal epithelium is in constant flux, with populations of stem cells distributed throughout the intestine differentiating into other, transient, cell populations. These stem cells exist within small discrete populations in intestinal crypts, a compartmentalization thought to have evolved as a mechanism to deter tumorigenesis, as cells accumulating mutations that are beneficial to cellular fitness have a physical hindrance to spreading throughout the tissue. However, small populations are subject to significant genetic drift, that is, random changes in allele frequency that eventually lead to fixation or loss, and less effective selection.

The accumulation of damage causing the loss of cellular fitness is a hallmark of aging and is especially relevant when DNA damage occurs in stem cells, compromising their role in tissue renewal. Indeed, several mouse models with the diminished ability to maintain cellular genome integrity succumb to accelerated age-related phenotypes through the loss of tissue homeostasis caused by stem and progenitor cell attrition. Just as stem cell mutations conferring a beneficial fitness effect will increase cell production, mutations conferring a deleterious fitness effect will lead to decreased cell production and the diminished maintenance of healthy tissue.

When mutations confer a selective advantage or disadvantage within the niche, there exists an intermediate crypt size that minimizes the probability that any crypt accumulates the large beneficial mutations necessary to initiate a tumor. By modeling the fixation of mutations drawn from a full distribution of mutational effects and accumulating throughout the populations of the entire intestinal epithelium, we show that a secondary trade-off exists - populations maintained at a size that results in the lowest rate of tumorigenesis are expected to accumulate deleterious mutations that manifest in tissue attrition and contribute to organismal aging.

At small stem cell niche sizes, there exists a large number of crypts to maintain homeostasis, and a higher probability that any one crypt will obtain a rare mutation of large effect that would result in tumorigenesis. As stem cell niche size increases, the number of crypts needed to maintain the same amount of epithelium decreases, and so does the probability of fixing mutations within the crypts, and therefore the chance of fixing a rare mutation of large effect. However, for larger values of stem cell niche size, the strength of selection increases, thus increasing the chance that a fixed mutation was beneficial, leading to higher chances of tumorigenesis. At the observed intermediate population size in mice, the whole tissue size is expected to decline with age as deleterious mutations accumulate in stem cell niches. If selective pressures against tumorigenesis have selected for intermediate stem cell niche population sizes in mammalian species, then it has been at the expense of increasing epithelial attrition.


Oisin Biotechnologies Launches New Website

Oisin Biotechnologies is a senescent cell clearance company founded by long-standing members of our community, seed funded by the Methuselah Foundation and SENS Research Foundation, and supported by the investment of a number of folk in the audience here. Targeted removal of senescent cells is a form of narrowly focused rejuvenation, shown to turn back numerous measures of aging in animal studies, and the Oisin team has made great strides in proving out their programmable gene therapy approach. This sort of commercialization project is exact what our community has been working towards all these years, and the faster that implementations reach the clinic, the better off we all are.

Oisin Biotechnologies' ground-breaking research and technology is demonstrating that the solution to mitigating the effects of age-related diseases is to address the damage created by the aging process itself. Our first target is senescent cells. When cells detect that they have been irretrievably damaged, they enter a non-dividing condition known as cell-cycle arrest, or senescence. It's believed this occurs to prevent cells from going rogue and turning cancerous. Ideally, they should die by the process known as apoptosis, but as we age, more and more frequently they don't. They become zombie cells - unable to kill themselves or resume normal function.

Senescent cells secrete molecules that cause inflammation in an effort to attract immune cells that would usually clear them. But for reasons that are not fully known, as we age, persistently senescent cells accumulate, leading to a vast number of age-related diseases. Oisin is developing a highly precise, patent-pending, DNA-targeted intervention to clear these cells. As a recent study has shown, clearing senescent cells both reduces negative effects of aging pathologies and also extends median lifespan and survival.

There are two major challenges to clearing senescent cells using our approach. First is to design and create the DNA construct that recognizes that a cell has become senescent, and then destroys it. Second is to safely and efficiently deliver this construct into cells throughout the body. Both goals have been achieved in our pioneering proof of concept experiments in 2016. We've first demonstrated the ability to transduce cells both in vitro (cell culture) and in vivo (in aged mice). Then we showed that p16 positive senescent cells can be killed on demand in both in vitro and in vivo environments. Now we are embarked on experiments that will show improvements in both healthspan and lifespan in model organisms from mice to primates. And then, everything changes.

Our proprietary technology gives persistently senescent cells a helping hand to "do the right thing." By providing an exogenous apoptotic gene, which is only transiently expressed in cells that already have the p16 gene active, we can precisely induce the senescent cell to commit suicide. Oisin has shown as much as an 80% reduction in senescent cells in cell culture and significant reductions of senescent cell burden in naturally aged mice. SENSOlytics is an Oisin proprietary platform technology that enables precise targeting of a senescent cell based on the DNA expression of the cell, not on surface markers or other characteristics that might be shared with normal, undamaged cells.


Adjusting Macrophage Proportions as a Basis for the Treatment of Atherosclerosis

The immune cells known as macrophages are involved in debris cleanup and destruction of potentially harmful cells, among other tasks, but in recent years more attention has been drawn to the important role they play in the complex coordination of cellular activities relating to healing and tissue maintenance. It is even thought that a significant portion of the difference between limited human regeneration and proficient regeneration of the sort observed in salamanders might be explained by differences in macrophage behavior between these species.

Further, and possibly a near-future basis for therapies, macrophages involved in regenerative processes appear split into a few different classes with distinct behaviors and protein signatures. Although this is a case of arbitrary dividing lines drawn on a continuous spectrum rather than a case of clearly separate camps, it is a still a useful distinction to make. These types are known as polarizations, and the polarizations of interest in this discussion are M1 and M2. Both play important roles in the bigger picture, but M1 macrophages are generally less helpful in regeneration, spurring inflammation and fibrosis, while M2 macrophages are generally more helpful, suppressing inflammation and generating a supportive environment for regrowth.

Researchers are finding that it is possible to enhance the outcome of regeneration by increasing the ratio of M2 macrophages to M1 macrophages. More M2 macrophages and fewer M1 macrophages produces more rapid, more effective regrowth of tissues, and in some cases induces regrowth that normally doesn't occur with any reliability in mammals. This has been achieved in animal studies of nerve regeneration and bone healing, to pick a few examples. Interestingly, the cancer research community is interested in turning the dial in the opposite direction, generating more of the aggressive, inflammatory M1 macrophages that destroy cancer cells. As I said, both types have their part to play in the bigger picture.

Moving on to the topic at hand here today, the research below covers the impact of polarization on another part of the macrophage task list, that of debris clearance. Atherosclerosis is a condition in which oxidized, fatty metabolic waste enters the blood stream and sufficiently irritates a section of the blood vessel walls for the cells there to take action. Inflammatory signals draw macrophages that attempt to clean up the garbage, but macrophages are unfortunately unexpectedly frail in the face of this sort of fatty debris. Some ingest too much and either die or become senescent, dysfunctional foam cells, further aggravating the situation. Over time, a small irritated portion of a blood vessel wall swells into a self-perpetuating disaster zone of dead and dying macrophages. Eventually this happens somewhere critical, and driven by the hypertension of aging, a blood vessel wall or the fatty mass inside the vessel ruptures to cause a stroke or heart attack. It turns out that here, as elsewhere, it is the case that adjusting the natural balance towards more M2 and fewer M1 macrophages produces better outcomes, but just how useful this is for human medicine remains to be determined with any great certainty.

Mechanism Shown to Reverse Disease in Arteries

A certain immune reaction is the key, not to slowing atherosclerosis as cholesterol-lowering drugs do, but instead to reversing a disease that gradually blocks arteries to cause heart attacks and strokes. The study in mice focuses on reversing the effects of "bad cholesterol," which is deposited into the walls lining blood vessels in levels influenced by both genetics and a person's diet. By the fourth decade of life, and thanks to the chronic reaction to cholesterol, most people have inflamed "wounds" in their arteries, called plaques, which when severe enough can rupture to cause blood clots that block arteries. "Even the latest, most potent cholesterol-lowering drugs, PCSK9 inhibitors, let alone widely used statins, cannot fully reverse damage done to arteries over time. We need the next generation of drugs to go beyond cholesterol lowering to address the immune reaction to accumulated cholesterol, and to dismantle plaques as part of reversing or regressing mature disease."

Once deposited into arteries, bad cholesterol - known to physicians as low density lipoprotein - triggers the body's immune system, which is meant to destroy invading microbes but can drive inflammatory disease in the wrong context. Immune cells in the bloodstream called monocytes swarm to cholesterol deposits, and become either inflammatory or healing cell types based on signals there. In situations where disease is worsening in a plaque, past studies have shown that monocytes become M1 macrophages that amplify immune responses, increase inflammation, and secrete enzymes that gnaw at plaques until they rupture. The current study confirmed that monocytes arriving in plaques where disease is regressing instead become M2 "healing" macrophages, which dampen inflammation and prevent the ruptures that precede clotting.

When mice were engineered to lose the ability of monocytes to become M2 macrophages, they could no longer achieve normal disease regression. By surgically transplanting plaques from diseased mice into the arteries of healthy mice, the research team brought about dramatic drops in cholesterol levels. This drop has been shown to trigger a second benefit in mice, where monocytes automatically become M2 instead of M1 macrophages as plaques rapidly regress. It is not known whether cholesterol lowering alone triggers this M2 switch in humans, but new imaging techniques may soon be able to detect changes in the type and number of macrophages in plaques. In the meantime, if researchers learn how to boost the M2 switch, a number of clinical applications may become possible just as methods arrive that can measure their success. "A race is underway to develop treatments that enhance the decision of human monocytes to become M2 macrophages in cases where the disease has not yet caused clot formation, at which point it becomes irreversible."

Inflammatory Ly6Chi monocytes and their conversion to M2 macrophages drive atherosclerosis regression

Using a number of mouse models of atherosclerosis regression, including the aortic arch transplant used in the present study, we have previously shown that aggressive lipid lowering promotes the resolution of plaque inflammation, which is characterized by a decreased content of macrophages and an increase in the level of markers of the M2 state. We now extend these findings to show that plaque regression and the attendant resolution of inflammation surprisingly require the recruitment of new monocytes, which assume the characteristics of M2 macrophages. Furthermore, contrary to the prevailing paradigm, the newly recruited monocytes are drawn from the Ly6Chi circulating subset, generally considered to be "inflammation-prone" precursors of M1 macrophages.

The characteristic rapid reversal of hyperlipidemia in mouse atherosclerosis regression models is likely to reduce the continuous stimulation of the plaque inflammatory response by atherogenic lipoproteins, but clearly is not sufficient for the resolution of inflammation. Based on our results, M2 enrichment must also occur, and how the change in lipoprotein environment causes this to happen also remains to be determined. Our finding that it depends on STAT6-dependent signaling in the newly recruited monocytes suggests that local factors in the regressing plaque stimulate this signaling pathway. STAT6 is activated by two key cytokines, IL-4 and IL-13. However, which of these cytokines is the main player, as well as their cellular source(s), in promoting plaque regression is unclear.

Though many questions remain, the present results provide insights into the dynamic nature of the inflammatory process and the role of Ly6Chi monocytes in plaques. These cells were previously thought to contribute only to plaque progression and inflammation, but are now shown here to be important in regression and inflammation resolution. One clinically relevant insight raised by our studies is that strategies that promote the accumulation of M2 macrophages in atherosclerotic lesions may be a promising approach toward promoting plaque regression, consistent with recent studies in mice in which treatment with IL-13- or IL-4-based therapy was protective against atherosclerosis progression.

Gensight Continues to Forge Ahead with the First Implementation of Allotopic Expression of Mitochondrial Genes

Mitochondria, the power plants of the cell, bear their own DNA, a small remnant of their origin as symbiotic bacteria. Unfortunately, this DNA is more vulnerable than the DNA found in the cell nucleus, and can become damaged in ways that contribute significantly to the aging process. How to address this problem? Allotopic expression of a mitochondrial gene is a process by which an altered version of the gene is placed into the cell nucleus in order to provide a backup source of the protein encoded by the gene. In this age of genetic engineering, inserting the gene isn't really the challenge, instead the difficulty lies in figuring out how to alter the gene in order for the protein produced to be transported back to the mitochondria where it is needed.

Funded by philanthropic donations, the SENS Research Foundation has been supporting allotopic expression research for a decade now, seeking to accelerate the development of therapies that can remove this contribution to the aging progress. The first programs funded gave rise to Gensight Biologics, a company that is pioneering the use of allotopic expression of the ND4 gene to address an inherited blindness condition in which the gene is mutated and dysfunctional. This effort is well on the way to proving out the technology in human trials and thereby providing a solid foundation for work on the other genes that must be backed up. Three mitochondrial genes are demonstrated so far, including ND4, and there are another ten to go after that. Commercial efforts of this nature are an important part of the overall development process, and it is a good thing to see a company pulling in significant funding for a technology that will become a part of later rejuvenation therapies.

GenSight Biologics has raised €22.5 million to prepare to bring gene therapy GS010 to market in the U.S. and Europe. The financing gives the Novartis-backed biotech enough cash to deliver data from two phase 3 trials next year and gear up for anticipated approvals on both sides of the Atlantic. Paris-based GenSight raised the cash from a mix of new and existing institutional investors, most of which are based in the US. Strong interest from these backers saw GenSight ease past its initial target of €20 million to pull in €22.5 million in the private placement. When added to the €48.8 million GenSight had in the bank at the end of March, management thinks the money moves its runway out to the first quarter of 2019.

That runway covers a critical period for GenSight. Topline 48-week data from two phase 3 trials of GS010 in patients with Leber hereditary optic neuropathy (LHON) are due in the second and third quarters of next year. GenSight is looking to the trials for evidence GS010 improves the clarity of the vision of patients with LHON, a hereditary form of vision loss caused by mitochondrial defects. GS010 is injected into the eye to deliver the human wild-type ND4 gene via an adeno-associated virus to deliver. This gene encodes for a protein typically produced by mitochondria.

One trial is assessing GS010 in patients who started losing their vision in the six months prior to enrolling in the study. The other is recruiting patients whose vision started deteriorating between seven and 12 months ago. Both trials are injecting GS010 into one eye of each participant and pretending to inject it into the other eye. Data from an earlier phase 1/2 trial suggest the gene therapy is most effective in patients whose vision started deteriorating less than two years ago. A recent 96-week update found the treated eyes of such patients had a mean gain of 29 ETDRS letters, as compared to an increase of 15 letters in untreated eyes. ETDRS is the test showing progressively smaller letters opticians use to gauge vision. The performance of GS010 to date has enabled GenSight to secure the support of some big-name backers. Following the latest financing, its biggest shareholders are Novartis, Versant, Abingworth, and Fidelity.


Arguing a Role for Stochastic Mutation in Stem Cells in Cardiovascular Disease

To what degree does random mutation in nuclear DNA contribute to aging over the present human life span? The present consensus is that this is a cause of disarray in metabolic processes, and that it does reach a significant level of consequence for tissue function. Unfortunately there is little direct evidence for this view - it is hard to split out just nuclear DNA damage from the rest of aging in order to isolate its effects, though there a few lines of research showing promise in this direction. Researchers here take a different approach to the question; they suggest that some forms of random mutational damage that occurs in stem cells will expand throughout that population over time, because the damage in some way confers a replication advantage. In this way it can come to have a significant effect, and it should be feasible to correlate different degrees of the expansion of this sort of mutational damage with specific measures of aging. In this case, the correlation is with cardiovascular disease.

Several explanations have been offered for how age contributes to cardiovascular disease. Aging is associated with the acquisition and exposure duration of other established risk factors for cardiovascular disease, including high systolic blood pressure and increased levels of low-density lipoprotein cholesterol. However, analyses that adjust for the concomitant burden of other risk factors consistently identify age as an independent predictor of cardiovascular disease. Modifiable risk factors account for only about 12% of the age effect in men and 40% in women. Thus, the aging process itself must promote cardiovascular risk, although the mechanisms that are involved are poorly understood.

Researchers now provide new insight into how aging can promote atherosclerosis and cardiovascular events in their investigation of a phenomenon termed clonal hematopoiesis of indeterminate potential, or CHIP. This condition is an age-related disorder characterized by the acquisition of somatic mutations in hematopoietic stem cells that confer on these cells a selective advantage. As a consequence, instead of the normal polyclonal generation of blood cells, mutation-containing clones expand over time and make up an increasing percentage of the stem cells and their progeny and may include granulocytes, lymphocytes, and monocytes. CHIP is rarely found in patients who are younger than 40 years of age, whereas this condition may exist in up to 10% of persons over the age of 70 years. Patients with CHIP have a higher rate of death from noncancer causes (particularly cardiovascular disease) than do age-matched controls without CHIP.

To address the cause of excess cardiovascular mortality, researchers identified CHIP (which they define as clonal dominance of hematopoietic cells bearing pathogenic mutations in any of 74 known driver genes of hematologic cancers) among participants in several studies that ascertained cardiovascular disease. In studies involving participants with a mean age of 60 years or older, carriers of CHIP had nearly twice the risk of coronary heart disease as noncarriers. Among younger participants (below 50 years of age), CHIP carriers had four times the risk of myocardial infarction as noncarriers. Preclinical coronary disease, as assessed on imaging as coronary-artery calcification, was also associated with CHIP. Finally, four of the most commonly mutated genes in CHIP (DNMT3A, TET2, ASXL1, and JAK2) were each individually associated with coronary heart disease.

Collectively, the work supports the hypothesis that CHIP is linked to the clinical events of atherosclerosis and that certain CHIP driver genes are involved in regulating inflammation. Both TET2 and DNMT3A appear to inhibit inflammation, so loss-of-function mutations in these genes could plausibly promote inflammatory responses. Similarly, there is a large body of literature suggesting that JAK2 regulates both inflammation and thrombosis, two important factors in the clinical manifestations of atherosclerosis. Thus, the data is consistent with established paradigms that inflammation is an accelerator of atherosclerosis and coronary heart disease. Moreover, their findings should prompt a discourse about studying the use of anti-inflammatory agents in patients with CHIP to limit the most common cause of death in these patients - cardiovascular disease.


Healthy Life Span Increases, and the Age at which We Reach Old Age is Rising

Today I'll point out an interesting paper on the demographics of aging, one that I hope indicates the spread of more nuanced and useful views into forecasts of the future of aging and longevity. While a good read, and helpful for our cause in that it will further spread the message that increases in healthy life span are both realistic and currently taking place, it is nonetheless still the case that this and all of the other long-term projections arising from the demographic community are essentially fantasies. They are simple extrapolations of trends in adult life expectancy established over the past few decades, and are thus based on a model of the future in which methods of rejuvenation are never invented and commercialized. In this future, progress in medicine consists only of incremental improvements to the present marginally effective therapies that attempt to patch over or compensate for the damage of aging. These treatments fail to repair or otherwise address that damage in any meaningful way, which is precisely why they produce only marginal outcomes at best.

This proposed continuation of the present gentle upward trend in life expectancy will not come to pass. The trend was established across decades in which no therapy attempted to address the cases of aging, the accumulation of molecular damage to cell and tissue structures that produces age-related disease and degeneration. Consider that for any failing machinery, it is very hard to keep it running when unable to fix the root cause of that failure. This is also the case for our biology: damage accrues, causing progressively greater system failures that we experience as age-related disease. Aging is no longer inevitable, however, as the first generation of rejuvenation therapies are even now nearing the clinic. To pick one example, selective destruction of senescent cells has been carried forward by venture funded companies these past couple of years, with human trials starting soon. Further, successful trials have been carried out in the past few years for clearance of forms of amyloid from old individuals, and again there is sizable backing for those lines of development.

Old age in the future of deliberate efforts to repair the damage that gives rise to aging will be profoundly different from old age in the past, in which medicine failed to address the causes of aging. There will be an abrupt upward discontinuity in the past trend of life expectancy, a sudden and considerably faster rate of increase in years of health and vigor. It is the difference between doing nothing for the causes of aging versus doing something to tackle those causes, and here and now is the dividing line between those two periods of development in medicine.

New Measures of Aging May Show 70 is the New 60

Traditional population projections categorize "old age" as a simple cutoff at age 65. But as life expectancies have increased, so too have the years that people remain healthy, active, and productive. In the last decade, researchers have published a large body of research showing that the very boundary of "old age" should shift with changes in life expectancy, and have introduced new measures of aging that are based on population characteristics, giving a more comprehensive view of population aging. The study combines these new measures with UN probabilistic population projections to produce a new set of age structure projections for four countries: China, Germany, Iran, and the USA.

One of the measures used in the paper looks at life expectancy as well as years lived to adjust the definition of old age. Probabilistic projections produce a range of thousands of potential scenarios, so that they can show a range of possibilities of aging outcomes. For China, Germany, and the USA, the study showed that population aging would peak and begin declining by 2040 in Germany and by 2070 in China, well before the end of the century. Iran, which had an extremely rapid fall in fertility rate in the last 20 years, has an unstable age distribution and the results for the country were highly uncertain. Population aging - when the median age rises in a country because of increasing life expectancy and lower fertility rates - is a concern for countries because of the perception that population aging leads to declining numbers of working age people and additional social burdens.

Probabilistic population aging

Probabilistic population forecasts were motivated by Keyfitz. Keyfitz wrote: "Demographers can no more be held responsible for the inaccuracy in forecasting population 20 years ahead than geologists, meteorologists, or economists when they fail to announce earthquakes, cold winters, or depressions 20 years ahead. What we can be held responsible for is warning one another and our public what the error of our estimates is likely to be."

There is now an extensive literature of probabilistic forecasting. All the probabilistic measures of aging produced by the United Nations assume that the threshold of old age is a fixed chronological age, regardless of time, place, education, or other characteristics of people. Researchers have questioned this assumption: "To the extent that our concern with age is what it signifies about the degree of deterioration and dependence, it would seem sensible to consider the measurement of age not in terms of years elapsed since birth but rather in terms of the number of years remaining until death." It is suggested the old age threshold be defined on the basis of some plausible remaining life expectancy rather than any specific chronological age. We call the ages, that are obtained when life expectancy is the characteristic that is held constant, prospective ages and measures that use them prospective measures of population aging.

New measures of population aging are useful because tomorrow's older people will not be like today's. They may well have longer life expectancies, better cognition, better education, and fewer severe disabilities. In most OECD countries, the labor force participation of people 65+ years old is increasing as are the ages at which people can receive a normal national pension. Since changes in the characteristics of people are ignored in the conventional measures of aging, they become more outdated with the passage of time. The use of prospective ages is one way to create measures of aging that are more in line with observable changes.

We chose a remaining life expectancy of 15 years. That was the life expectancy at age 65 in many low mortality countries around 1970. We show estimated and forecasted old age thresholds based on a remaining life expectancy of 15 years for China, Germany, Iran and the US for the years 2013 through 2098. In 2013, the old age threshold was 66 in China and 72 in Germany. By 2098, the old age threshold is forecasted to increase to 79 in Germany and 77 in China. Most of the population aging that we measure in China, Germany, and the US occurs between now and around 2040. The probabilistic forecasts show that it is highly likely that the prospective median age of the population of Germany and the US will be lower in 2098 than it is today. Even in China there is around a 50 percent chance that the prospective median age will be lower at the end of the century than it is today. It is possible that people's concern about the future is related to the number of additional years they expect to live. Lower prospective median ages in 2098 than now indicate that the people at the median age will have even more years of additional life ahead of them than people at the median age have currently, despite that median age being higher.

Considering Epigenetic Clocks in Mice and Men

The development of a reliable and accurate biomarker of biological age is an important step for the longevity science field. Testing potential rejuvenation therapies is at present a drawn-out and expensive process, as the only truly effective way to determine outcomes is to wait and see. That requires years and millions of dollars in funding for mouse studies, a cost that greatly restricts the amount of experimentation and exploration it is possible to carry out, even for the better funded research groups. If instead a biomarker test could be applied shortly before and shortly after a treatment in order to assess its potential, that would greatly accelerate progress in the field. Epigenetic clocks based on assessment of patterns of DNA methylation are presently the most promising candidate for such a biomarker of aging, and here researchers discuss the behavior of presently established clocks in mice and humans.

Epigenetic clocks provide powerful tools to evaluate nutritional, hormonal, and genetic effects on aging. What can we learn from differences between species in how these clocks tick? One of the most fascinating findings in human aging is that it is associated with highly reproducible DNA methylation (DNAm) changes. DNAm levels at age-associated CG dinucleotides (CpG sites) can be integrated into epigenetic age predictors, which provide robust biomarkers to estimate chronological age. With the advent of more and more publically available DNAm profiles, such aging signatures were further developed to facilitate higher precision in age predictions, particularly for blood samples. Probably the most commonly used epigenetic aging signature is based on DNAm levels at 353 CpG sites and facilitates relatively precise age predictions for many human tissues: the median "error" (MAE), defined by the median absolute difference between DNAm age and chronological age, is usually less than 4 years.

Now - about 6 years after the first epigenetic clock paper - similar age predictors have been established for mice. Again, they were initially described for defined murine tissues, specifically liver and blood, taking into account the fact that there are notoriously large differences in the epigenetic makeup of cells from different tissues. However, it is also possible to derive a multi-tissue murine DNAm age predictor, in analogy to the most commonly used human clock. The signature is based on 329 CpGs and has been validated for cortex, muscle, lung, liver, and heart tissue. Overall, the multi-tissue age predictor reached a MAE of less than 4 weeks, although how it performs in other tissues has yet to be shown.

Studies indicate that the epigenetic clocks of mice tick faster than those of humans. This can be anticipated because the maximum life-span of mice (about 2 years) is much shorter than it is in humans (about 85 years). If the molecular changes of aging are linked to life expectancy and generation time, then this might support the notion that aging reflects a controlled evolutionary process. However, there is still an open debate on whether aging is due to an accumulation of cellular defects, or is driven by a developmental mechanism. Either way, comparison of epigenetic clocks in mice and men will provide new insights into the regulation of age-associated DNAm.

Direct comparison of age-associated CpGs in mice and men indicated that there is a moderate but significant association between the two species. It is not always trivial to identify orthologous CpG sites, and further interspecies comparison will be required to better understand similarities and differences of age-associated genomic regions. However, the overlap of age-associated CpGs in age predictors for human and mice seems to be rather low, and hence epigenetic clocks need to be trained specifically for different species. In terms of function, age-associated CpGs in humans and mice seem to be enriched in genes that are involved in morphogenesis and development. However, in both species age-associated DNAm changes are not generally reflected at the gene expression level - and thus the biological relevance remains largely unclear.

Mouse DNAm clocks provide powerful tools to study longevity interventions in one of the most relevant model organisms for aging research. These signatures were initially trained to correlate with the "real" chronological age of mice - but aging rates may differ between individuals. In fact, there is evidence that epigenetic clocks rather reflect the biological age, which is related to the perceived aging process of an organism. In analogy, it was previously demonstrated that human DNAm age is related to life expectancy: accelerated epigenetic age is associated with higher all-cause mortality. This finding has been validated in various additional cohorts and with different epigenetic age predictors. Furthermore, human epigenetic aging rates have been shown to be significantly associated with sex, race/ethnicity, and some disease risk factors. In mice, there was no clear difference in predicted DNAm age of male and females. However, ovariectomy, which reduces the average life span in female rats, results also in significant age acceleration. Caloric restriction or dietary rapamycin treatment, both of which result in increased life expectancy of mice, reduced epigenetic age. In humans, specific diet seems to have a less pronounced impact on epigenetic age, but there is significant association of DNAm age and body mass index (BMI). Apparently, different parameters can affect biological aging in mice and men.


Thoughts on Effective Advocacy for Rejuvenation Research

Following on from a recent post on the subject, here is another article from the Life Extension Advocacy Foundation (LEAF) on strategies and efforts to persuade the world to support work aimed at greatly lengthening healthy human life spans. For those of us to whom it is obvious that a very large amount of time and funding should be devoted to this goal, because aging is by far the greatest source of suffering and death, because the cost of bringing aging under medical control is small in comparison to what is spent on trying and failing to cope with it, and for a score of other equally good reasons, it can be frustrating to see that others do not presently think that way. They seem happy to march to their deaths, while at the same time happy to avail themselves of the small gains resulting from the comparatively crude medicine for age-related disease that is presently available. If rejuvenation therapies existed, these same people would use them and be thankful for them, but very few will so much as raise a finger to help create these technologies. It is a challenge.

One of the most frequent questions we at LEAF hear is this: when will innovative therapies to delay, stop and eventually reverse age-related damage become available? This is not an easy question to answer, because the pace of progress depends on many factors - predominantly, funding. Fundamental studies on aging are not well-funded and the accumulation of knowledge necessary to proceed from lab work to clinical trials and then clinical practice does not happen fast enough. Government funding is more often allocated to mainstream areas, such as research on single diseases. Business, for its part, does not show much interest in fundamental science, because usually there is no final product that can be sold. The only other source of funding is the general public. But most people are not yet sufficiently informed about the plausibility of bringing the aging processes under medical control and do not share the values of our community. Sometimes (to be frank, pretty often) activists trying to engage the public in an enlightening conversation can encounter resistance or even rejection.

Learning requires active, conscious participation. This means that students will seek and absorb information if they are interested, or they will ignore it if they do not see any personal benefit in it. So what do most people want? It's life extension right? Wrong! Studies show that when people are asked "how long would you like to live?" with no other conditions specified, people added around 5 to 10 years to the average life expectancy for their country and that was it. If we do not first explain the aging processes, the connection with age-related diseases and the repair based solutions that lead to healthy longevity, people think longevity means a longer life of prolonged ill health and frailty. Who wants to spend another ten or twenty years in a wheelchair or in a care home? And this is exactly the image most people have when these words are used. This is what the expression "life extension" means to the majority of people - and this is why we should avoid beginning the conversation with it.

At the same time, sociological studies show that if the possibility of perfect health throughout life is introduced into the equation from the very beginning, people show much more interest and support for the idea of ​​prolonging life. People literally switch from one camp to the other, those who just did not want to live for more than 80 years now decide they want to live to more than a hundred, and those who just wanted to get to 120 are suddenly ready to live to 150 or beyond. People are ready to support the development of new medical technologies, even scary ones like gene therapies or gene editing, under the condition they are going to be used for treatment. However their use for the prolongation of life belongs to the category of "human enhancement" and as such the idea is most often rejected. So it is highly recommended for advocates to add that these technologies will help treat or prevent serious chronic diseases, while extended lifespans will just be a possible nice side-effect.


SENS Research Foundation Publishes the 2016 Annual Rejuvenation Research Report

The SENS Research Foundation annual reports tend to arrive in the middle of the following year, and today the 2016 report was published. You can find it in PDF format at the foundation website. The story of SENS rejuvenation research, approaches that aim to repair the cell and tissue damage that causes aging, is one of growth and success over the years. It has been a bootstrapping from idea to reality, powered by the philanthropy and determined support of our community. We have come a long way and achieved a great deal these past fifteen years. Yet there remains the upward curve ahead, and the completion of the vision of an end to aging has yet to be accomplished.

It is true that the first SENS therapies are on the way to the clinic, their commercial development funded by venture capital now, and senescent cell clearance is at the front of the pack. But equally important approaches to removing the damage that causes aging, such as the breaking of glucosepane cross-links, are still in the laboratory, still entirely funded by charitable donations, still building the infrastructure and running the tests in search of the first potential basis for a working therapy. When that first breakthrough is made, matters speed up considerable and funding comes running from many sources - but getting there is a slow grind. The more we can do to help the SENS Research Foundation thrive, the faster they can push forward with this stage of development: planting the seeds that will blossom into vast medical industries, and in doing so bring great benefit to humanity.

SENS Research Foundation 2016 Annual Report (PDF)

Since SENS Research Foundation's founding in 2009, we've worked toward bringing our vision of a world free of age-related disease from concept to reality. In challenging ourselves on this front, we have likewise challenged you, our supporters. We've asked a lot of all of you, and not only have you accepted this challenge, you have delivered. The rejuvenation biotechnology community that has emerged over the past several years owes its existence to each and every one of you. You have become our most vocal advocates. Over 2000 of you have become our funders.

We asked you to help us change how the world researches and treats age- related disease. You did. Through the efforts of our donors, collaborators, and our advisory board, world-renowned institutions are pursuing age- related disease research specifically focused on the damage-repair paradigm. We asked you to help us move from basic research to translational research and clinical trials. You did. In 2016 we launched Project|21, our five-year plan to help move rejuvenation biotechnologies from concept to human clinical trials. Project|21 is now backed by a number of generous and forward-thinking individuals.

You asked us to follow through. We did. In lending your support, you place not only resources in our hands, but trust. We know that a world-changing nonprofit cannot operate on the power of vision alone; and we are here not just to inspire, but to deliver results. The purpose of this report is to demonstrate concrete examples of those results to you. With your help, we have taken great steps toward the establishment of a robust rejuvenation biotechnology industry and the realization of our vision. And every step we are able to take is proof of the power of your community.

Death-Resistant Cells: Toward Neutralizing the SASP

Buck Institute researchers led by Dr. Judith Campisi had shown that the presence of senescent cells alongside cancer cells can stimulate those cells to both multiply more rapidly and to spread to other parts of the body - the metastasis process, which ultimately makes most cancers so deadly. Repeating these studies in cell culture while inhibiting the senescence-associated secretory phenotype (SASP) with apigenin almost completely nullified the proliferation-stimulating and pro-metastatic effects of senescent cells on breast cancer cells. Drugs based on parts of apigenin's structure could dampen some of the harmful effects the SASP in senescent cells. Removing these cells is the ultimate solution to these problems, and in the last year several groups have made rapid progress toward this goal. In the meantime, these studies using apigenin may demonstrate important principles from which senescent-cell-focused rejuvenation biotechnologies may be derived.

Target Prioritization of Tissue Crosslinking

Our arteries slowly stiffen with age, in substantial part because of random crosslinking of the structural proteins collagen and elastin. Developing rejuvenation biotechnologies to break these crosslinks is key to restoring youthful arterial function. To tease out the effects and relative importance of all of these different sources of crosslinking in aging tissues, the Babraham Institute team has been studying the crosslinking process in the tissues of aging mice. This has required the development and validation of new experimental methods and assays, which are now ready for use. The team has evaluated multiple tissues for crosslink presence. Importantly, some of the crosslinks that have been reported by others to accumulate in aging tissues were not detected. While further studies are needed to confirm it decisively, these results suggest that several crosslinks now believed to accumulate in aging tissues may actually be experimental artifacts.

Engineering New Mitochondrial Genes to Restore Mitochondrial Function

Free radicals derived from our energy-producing mitochondria can mutate the organelle's DNA, leading to deletions of large stretches of the mitochondrial genome. These deletion mutations prevent the mitochondria from building various pieces of the electron transport chain (ETC), with which mitochondria generate most cellular energy. The accumulation of deletion-mutation-containing cells is a significant consequence of aging. A potential rejuvenation biotechnology to recover ETC function is the allotopic expression of functional mitochondrial genes: placing "backup copies" of all of the protein-coding genes of the mitochondria in the "safe harbor" of the nucleus, thereby giving the mitochondrion all of the proteins it needs to continue producing energy normally even when the original mitochondrial copies have been mutated.

This year, the SRF MitoSENS team reported a tremendous success: for what they believe is the first time, they have used allotopic expression to rescue the complete loss of a mitochondrially-encoded protein in a mammalian cell. A publication announced their success in the fall of 2016. The results show that their targeted and recoded ATP8 protein can be expressed from the nucleus, turned into protein in both normal and mutant cells, and efficiently targeted to the mitochondria. Furthermore, they can demonstrate functional rescue of cells. Under conditions where mutant cells die for lack of ability to produce energy, the cells with engineered allotopically-expressed proteins were able to survive and replicate. In addition to ATP8, the SRF MitoSENS team has further demonstrated expression and targeting of a second re-engineered protein, ATP6. It is proof-of-concept that ATP8 is not a special case.

Identification of the Genetic Basis of ALT in Cancer

Telomeres shorten every time a cell divides, and thus all cancers have to find a way to keep their telomeres long enough to prevent senescence or death. Most cancers use an enzyme called telomerase for this purpose, but about 10-15% of cancers use a telomerase-independent mechanism known as Alternative Lengthening of Telomeres (ALT). The ALT mechanism remains largely a mystery, and therefore the OncoSENS team at SENS Research Foundation is working hard to find new ways to attack ALT cancers. First, the team has developed and established two separate high-throughput assays measuring different ALT-specific biomarkers. These assays will finally enable cancer researchers to screen hundreds of thousands of compounds across multiple drug libraries, or even test every single one of the more than 20,000 genes in the human genome, for ways to shut down ALT cancers. In addition to their biomarker work, the team is also pursuing more targeted methods to kill ALT cancer cells.

Glucosepane Crosslinks and Routes to Cleavage

One major cause of crosslink accumulation in aging is Advanced Glycation Endproducts (AGE), and one AGE in particular, called glucosepane, is currently thought to be the single largest contributor to tissue AGE crosslinking. The Yale AGE team is studying the role of AGEs in aging, and developing novel tools and strategies for reversing AGE-mediated protein damage and develop new antibodies and reagents to enable rejuvenation research. Our pilot lab at Cambridge University found that all of the commercially-available antibodies for the major AGE-related molecules are actually highly unreliable. This is a serious impediment. The Yale glucosepane team is now tackling this problem via the novel chemistry and methods they have developed. In the last twelve months, the Yale team has made exciting progress in their work. Most notably, they have developed the first synthetic route to produce glucosepane. Their novel synthetic strategy is the first ever to provide high yields of pure samples of glucosepane, putting them (and soon other scientists) for the first time in a position to explore mechanisms through which crosslinks can be broken.

In collaboration with a colleague at Yale, they have also developed a high-throughput assay for screening proprietary libraries of organic catalysts for agents capable of breaking synthetic glucosepane. One of these libraries has already been taken forward for proof of concept, which led to the identification of several leads for catalysts that could be capable of breaking glucosepane. Beyond that, the Yale group has successfully generated proteins containing their synthetic glucosepane that can be used to identify antibodies that label glucosepane-containing proteins. These antibodies will enable the immunochemical detection of glucosepane crosslinks for a wide range of applications.

Tissue-Engineered Thymus

The thymus gland is responsible for the development of a class of immune cells called T-cells. As part of the degenerative aging process, the thymus shrinks in size. This process of thymic atrophy prevents the body from maturing new T-cells, progressively weakening the immune system's ability to fight off never-before-encountered infections. Engineering new, healthy thymic tissue would help to restore the vigorous immune response of youth. SENS Research Foundation has therefore funded a Wake Forest Institute for Regenerative Medicine (WFIRM) group to apply tissue engineering techniques to the creation of functional thymic tissue to fortify or replace the aging thymus. Engineering new tissues requires a "scaffold" in which to embed cells to give them structure and functional cues, and the WFIRM group has tested different scaffolding systems: decellularized donor scaffolds and hydrogels.

In the decellularized scaffold paradigm, an organ of the type that is needed is taken from a donor, but is then stripped of its original cells and DNA, leaving behind a protein structure with low potential for immunological rejection that can be repopulated with cells taken from the new organ recipient. The WFIRM group initially began work in this paradigm using mouse organs, but they found that once decellularized, mouse thymuses lacked the rigidity to serve in that role. They accordingly moved on to the pig thymus - a species that not only worked well as an experimental system, but has some clinical potential as well. The pig is closer to humans both immunologically and in terms of size.

Catalytic Antibodies Targeting Transthyretin Amyloid

As part of the degenerative aging process, proteins that normally remain dissolved in bodily fluids become damaged, and adopt a misfolded form called amyloid. Amyloid composed of the transporter protein transthyretin (TTR) deposits in the heart and other organs with age, beginning to impair heart function. With SRF funding, the University of Texas-Houston Medical School (UTHMS) extracellular aggregate team is working to develop novel catalytic antibodies ("catabodies") that would recognize and cleave TTR amyloid deposited in the heart and other tissues. Catabodies have the potential to be safer and more effective than conventional antibody-based immunotherapies: their catalytic activity minimizes the amount of antibody required to clear deposits from tissues, and the fact that they don't form stable complexes with their targets or engage immune cells is expected to minimize the inflammatory side-effects seen with other experimental antibody therapies.

Work has resulted in the identification of two powerful TTR-cleaving catabodies. When tested for their ability to degrade misfolded wild-type TTR, these candidates were able to hydrolyze both soluble aggregates and deposit-like particulates, while having no effect on either TTR in its healthy, normal conformation or on a selection of fourteen other physiologically important proteins. Concentrations required to disintegrate 80% of a sample of amyloid were many hundreds of times lower than those routinely achieved in the blood using other infused antibodies. The establishment of stable cell lines will enable larger-scale production, as the team works to develop these candidates into functional rejuvenation biotechnologies.

Rejuvenation of the Systemic Environment

There might be a misunderstanding of what was really going on in parabiosis. When animals are connected, they are not just given reciprocal blood transfusions, but are surgically joined together. So in addition to receiving young blood, the old animals also have their old blood filtered through the young animals' livers and kidneys, and diluted with the young pairmate's own blood. Might the effects of parabiosis mostly come from the removal of toxic or suppressive factors from the old animals' sluggish circulation instead of from the delivery of active rejuvenating factors?

To test this possibility - and to accelerate identification and testing of potential pro- and anti-rejuvenation factors in the exchanged blood - SENS Research Foundation funded Dr. Conboy and the UC Berkeley systemic environment team's development of a novel technological platform. Using a mixture of off-the-shelf and custom 3-D printed parts, this platform enables the group to easily and safely extract blood from small animals and transfuse it quickly and directly into another animal, without the reciprocal exchange of its blood or the passage of its blood through the pairmate's system. It thus separates the effects of the young animals' metabolic and excretory systems from the pure effects of their blood.

The team then used the new system to repeat key parabiosis experiments from Dr. Conboy's and others' labs. As compared with the impact of full-on parabiosis, the effects of isolated young blood on old muscles' ability to repair an injury were still substantial: the stem cells recovered significant regenerative powers, and less residual fibrosis remained after the wound was resolved. But by contrast, previously-reported benefits of parabiosis in the brain and the liver were either not present, or were far more modest. Another critical finding was the confirmation of suppressive factors in the old animals' blood, which inhibited neurogenesis and other regenerative responses of young animals transfused with it. While this clearer picture of the basis of the "parabiosis effect" indicates a lower likelihood of isolating true pro-rejuvenation factors in the blood of young mice, we are nonetheless closer to being able to filter out factors responsible for suppressing the regenerative potential of an older body.

Commercial Development

Two of the companies SENS Research Foundation has supported are moving to raise funding to move their research from the lab to clinical trials. Ichor Therapeutics announced a Series A offering to bring its Lysoclear product for age-related macular degeneration and Stargardt's macular degeneration through Phase I clinical trials. In 2014, Ichor Therapeutics completed a material and technology transfer agreement for rights to concepts and research pioneered by SENS Research Foundation. Lysoclear, which Ichor announced in 2017, is a recombinant enzyme product based on extending SRF's prior work that selectively localizes to the lysosomes of retinal pigment epithelium cells where A2E accumulates, and destroys it. Ongoing studies suggest that Lysoclear is safe and effective at targeting A2E, the main toxin driving these diseases, eliminating up to 10% with each dose. This product would be the first clinical candidate based on concepts and research pioneered by SENS Research Foundation.

Oisin Biotechnologies is focused on the genetic elimination of unwanted cells, but without involving the immune system. Oisin reports significant progress in showing that their vector works, efficiently transducing cells and delivering a DNA construct which can kill targeted cells on command. Oisin closed a $500K oversubscribed convertible debt round in mid-December and is working towards a substantial Series A in the next few months that would take it towards a Phase 1 clinical trial.

An Autoimmune Component to Parkinson's Disease

Researchers here provide evidence for Parkinson's disease to have a significant autoimmune component, adding to other factors known to contribute to the death of dopamine generating neurons that is characteristic of this disease. It is certainly the case that the growing dysfunction of the immune system in later life includes a variety of autoimmune aspects, and that those aspects are still poorly mapped. It is reasonable to expect that researchers will continue to uncover ways in which immune system failures contribute to well-known age-related conditions in the years ahead. The disovery here is particularly interesting, as it links autoimmunity to the buildup of metabolic waste and consequent failure of mechanisms of maintenance that is observed in aging. This is a target for the SENS rejuvenation research program, and therapies built on this approach should prove broadly beneficial, precisely because they will halt and turn back many chains of consequences akin to that reported by the researchers here.

Researchers have found the first direct evidence that autoimmunity - in which the immune system attacks the body's own tissues - plays a role in Parkinson's disease, the neurodegenerative movement disorder. The findings raise the possibility that the death of neurons in Parkinson's could be prevented by therapies that dampen the immune response. "The idea that a malfunctioning immune system contributes to Parkinson's dates back almost 100 years. But until now, no one has been able to connect the dots. Our findings show that two fragments of alpha-synuclein, a protein that accumulates in the brain cells of people with Parkinson's, can activate the T cells involved in autoimmune attacks. It remains to be seen whether the immune response to alpha-synuclein is an initial cause of Parkinson's or if it contributes to neuronal death and worsening symptoms after the onset of the disease. These findings, however, could provide a much-needed diagnostic test for Parkinson's disease and could help us to identify individuals at risk or in the early stages of the disease."

Scientists once thought that neurons were protected from autoimmune attacks. However, in a 2014 study, researchers demonstrated that dopamine neurons (those affected by Parkinson's disease) are vulnerable because they have proteins on the cell surface that help the immune system recognize foreign substances. As a result, they concluded, T cells had the potential to mistake neurons damaged by Parkinson's disease for foreign invaders. The new study found that T cells can be tricked into thinking dopamine neurons are foreign by the buildup of damaged alpha-synuclein proteins, a key feature of Parkinson's disease. "In most cases of Parkinson's, dopamine neurons become filled with structures called Lewy bodies, which are primarily composed of a misfolded form of alpha-synuclein."

In the study, the researchers exposed blood samples from 67 Parkinson's disease patients and 36 age-matched healthy controls to fragments of alpha-synuclein and other proteins found in neurons. They analyzed the samples to determine which, if any, of the protein fragments triggered an immune response. Little immune cell activity was seen in blood samples from the controls. In contrast, T cells in patients' blood samples, which had been apparently primed to recognize alpha-synuclein from past exposure, showed a strong response to the protein fragments. In particular, the immune response was associated with a common form of a gene found in the immune system, which may explain why many people with Parkinson's disease carry this gene variant.

Researchers hypothesizes that autoimmunity in Parkinson's disease arises when neurons are no longer able to get rid of abnormal alpha-synuclein. "Young, healthy cells break down and recycle old or damaged proteins, but that recycling process declines with age and with certain diseases, including Parkinson's. If abnormal alpha-synuclein begins to accumulate, and the immune system hasn't seen it before, the protein could be mistaken as a pathogen that needs to be attacked."


Altering Relative Macrophage Population Numbers to Enhance Nerve Regeneration

A good deal of evidence has accumulated to show that the immune cells called macrophages play important roles in regeneration. Further, there are several different classes of macrophage with quite different behaviors, and while all are essential in the bigger picture, one of them tends to hinder regeneration as a side-effect of the accomplishment of its other duties. Researchers have shown in a number of studies that adjusting the proportion of macrophages in a tissue, towards less of the hindering type, can significantly improve outcomes, and perhaps even produce regeneration that would normally not occur with any great reliability, such as regrowth of nerve tissue. This paper is a recent example of this area of research:

After nerve trauma, the standard clinical operating procedure is to oppose the two nerve ends and, when possible, suture them together. Ultimately, even with successful autografting, only 40% of patients regain useful function. Therefore, there is a clear, urgent, and unmet clinical need for an alternative approach that can match or exceed autograft performance. After peripheral nervous system (PNS) injuries, neurons respond rapidly by changing their activities and promoting a regenerative phenotype. At the distal nerve stump, Schwann cells (SCs) adopt a reparative phenotype. SCs, as well as infiltrating and resident macrophages, remove inhibitory debris, enabling new axons to sprout into the degenerated nerve. Although monocytes and their descendants (in particular, macrophages) have long been known to play an essential role in the degenerative process, only recently has their importance in positively influencing regeneration been recognized. Monocytes are abundant during nerve degeneration and regeneration and modulate the sequence of cellular events which can determine the outcome of the healing process.

After inflammatory insult, macrophages that accumulate at the site of injury appear to be derived largely from circulating monocytes. Entry of monocytes into the distal site of an injured nerve is enabled through up-regulation and release of a major monocyte chemokine, monocyte chemoattractant protein (CCL2) by SCs, which reaches its maximum 1 day after injury. Besides CCL2, the CX3CR1 ligand (fractalkine) can also recruit monocytes through the CX3CR1 receptor. In rats, two major subsets of monocytes have been identified. These two subtypes of monocytes can be recruited to injured tissues, where they can subsequently differentiate into classically activated (M1) or alternatively activated (M2) macrophages. These two phenotypes of macrophages represent a simplistic discrete depiction of a continuous spectrum between two activation states. Generally, M1 macrophages produce proinflammatory cytokines as well as high levels of oxidative metabolites, and M2 macrophages make the environment supportive for tissue repair by producing antiinflammatory cytokines that facilitate matrix remodeling and angiogenesis.

The plasticity of monocytes/macrophages makes them an attractive target for modulation in the context of nerve repair. A prior short-term study demonstrated that direct modulation of macrophages toward a prohealing phenotype, using interleukin 4 (IL-4), results in an increase in SC recruitment and axonal growth. The premise herein is that preferential recruitment of anti-inflammatory reparative monocytes to the site of injury will more effectively bias the immune microenvironment toward a prohealing response and in turn set off a regenerative biochemical cascade involving SCs and neuronal processes that leads to improved repair. Since CX3CR1 receptor is mainly expressed on antiinflammatory reparative monocytes, exogenous fractalkine, the ligand for CX3CR1, can be used to preferentially recruit these monocytes to the site of nerve injury and thus increase the subsequent ratio of prohealing to proinflammatory macrophages during the regeneration process.

Thus an immunomodulatory approach to stimulating nerve repair in a nerve-guidance scaffold was used to explore the regenerative effect of reparative monocyte recruitment. Early modulation of the immune environment at the injury site via fractalkine delivery resulted in a dramatic increase in regeneration as evident from histological and electrophysiological analyses. This study suggests that biasing the infiltrating inflammatory/immune cellular milieu after injury toward a proregenerative population creates a permissive environment for repair. This approach is a shift from the current modes of clinical and laboratory methods for nerve repair, which potentially opens an alternative paradigm to stimulate endogenous peripheral nerve repair.


Senescent Cells and Declining Heart Health in the Context of Oxidative Stress

There is every reason to believe that selective destruction of senescent cells in older individuals should improve heart health, lowering the risk of cardiovascular disease and dysfunction. Researchers who demonstrated 25% median life extension in mice engineered to lack senescent cells found improvements in a number of measures of cardiac health. There is a good deal of evidence for senescent cells to reduce stem cell activity and tissue regenerative capacity, perhaps through chronic inflammation and other consequences of changes in immune cell behavior. Senescent cells spur fibrosis, which disrupts small scale tissue structure with the formation of scar-like tissue, and the growth of fibrosis is important in heart tissue aging. And so on, through much of the list of problems in cell and tissue function known to be caused by the presence of senescent cells. In the paper I'll point out here, researchers focus specifically on oxidative signaling and rising levels of oxidative stress in the heart, and how senescent cells might be involved in this facet of heart aging.

Oxidative theories of aging were among the first such views of the causes of aging to be established in the modern era of cellular biochemistry. The original, simple theories that postulated aging as directly driven by oxidative damage to important molecules have since been put to one side in favor of more nuanced views. The failure of antioxidants, when applied generally, to slow aging is considered to disprove the simple view of aging as cellular damage that scales as the presence of oxidative molecules increases with age. It is certainly true that the oxidative molecules and signatures of harmful oxidative modification of vital proteins do increase with age, however. Equally it is also true that oxidative molecules and oxidative damage are used as signals in beneficial processes, such as the response to exercise - antioxidants can actually cause harm by interfering there. In short, oxidative metabolism is a complex, balanced process; that it is disrupted and runs awry with aging doesn't necessarily make it a cause rather than a consequence.

Over the years, attention has focused upon mitochondria, the power plants of the cell, as the prime source of oxidative molecules and possibly the prime source of disruption in oxidative metabolism in old tissues. Modestly increasing or reducing the flux of oxidative molecules generated by these organelles can improve health in short-lived species - in one direction by causing less damage and in the other by spurring greater repair and maintenance activities. Severe disruption of correct mitochondrial function, something that is known to occur in aged tissues, can drive cells into a failure state that results in large quantities of oxidative molecules pumped out into the surrounding tissues. To close the circle, mitochondrial dysfunction goes hand in hand with cellular senescence, though the bigger picture of cause and consequence here is complicated and still incomplete.

Cardiac Cell Senescence and Redox Signaling

Among age-related diseases, cardiovascular disease has an impressive prevalence, considering that the remaining lifetime risk for cardiovascular disease is about 50% at the age of 40. Consistently, the pathophysiologic modifications that are observed in aging hearts and arteries interact with alterations that characterize atherosclerosis progression, concurring to the development of age-associated heart failure. This latter is due to a combined diastolic and systolic dysfunction, caused by cardiac hypertrophy, replacement fibrosis, and myocardial ischemia, even in the absence of atherosclerotic coronary disease.

Morphometric data acquired in the early 1990s suggested that the number of left ventricle cardiomyocytes declines progressively with aging. Consistently, investigators have documented that although cardiomyocyte turnover occurs postnatally, the rate of cardiomyocyte renewal declines as age advances. Intriguingly, while the same investigators have recently suggested that the total number of cardiomyocytes residing in the left ventricle does not change with aging, evidence of myocyte death has been shown to occur both in male primates and in humans. In these latter, cardiac troponin T levels increase with aging and can predict cardiovascular events and death in the general population. This finding is thought to be the consequence of the age-related reduction of expression or activity of proteins that are involved in cardioprotection, a condition that eventually leads to an increased susceptibility of cardiac myocytes to injury.

To understand the mechanisms leading to heart failure, we and other authors hypothesized that the reduced cardiomyocyte turnover observed in aging was a consequence of the reduced cardiac growth reserve. Several independent groups have shown that undifferentiated, primitive cells reside in mammalian hearts and are involved in cardioprotection against heart failure, possibly generating new myocytes. Conversely, different lines of evidence obtained in animal models of heart failure and in humans indicate that senescent and dysfunctional cardiac resident stem/progenitor cells (CS/PC) accumulate as a consequence of cardiac pathology. Furthermore, with organism aging, senescent primitive and differentiated cells accumulate in mammalian hearts.

Although the concept of cellular senescence was introduced more than 50 years ago, the debate around this programmed cellular behavior is still ongoing. Specifically, in relatively recent years, it has been shown that cell senescence may exert positive effects, by promoting tissue healing after injury and protecting young organisms from cancer. However, in line with the antagonistic pleiotropy theory of aging, these beneficial effects exerted by cell senescence in young animals may be also responsible for the occurrence of functional impairment and age-related pathologies. Consistently, "rejuvenation" strategies aimed at reducing the frequency of senescent cells in the organism or designed to modulate those pathways whose activation status is altered in cell senescence can restore cardiac function in aged and failing hearts. Finally, we should emphasize that, while it has been postulated that reactive oxygen species (ROS) play a primary role in the development of cell senescence, the molecular mechanisms responsible for the development and evolution of cellular senescence are still a matter of intense research.

For many years it was believed that ROS were produced in an unregulated manner as a byproduct of cellular metabolism. Moreover, their ability to cause damage to macromolecules was thought to be responsible for organism aging (also known as the mitochondrial free radical theory of aging, MFRTA). Consistently, several pieces of evidence have shown an age-dependent decrease in mitochondrial integrity, and a parallel increase in the level of oxidized DNA (including mitochondrial DNA). These alterations have led to the formulation of "the vicious cycle hypothesis of mitochondrial ROS generation," according to which the mitochondrial production of ROS would damage mitochondrial DNA (mtDNA) and lead to mitochondrial dysfunction, thus increasing ROS generation. However, discordant results have been obtained in more recent years, which have either supported or refuted the increased production of mitochondrial ROS with aging.

These seemingly contradictory results can be reconciled if we consider that ROS have a dual nature. In fact, on top of their ability to damage in non-specific fashion biological molecules, ROS can exert useful and beneficial effects, by regulating signaling pathways. According to current models, ROS generation is highly regulated, and therefore oxidative stress would arise from the loss of this architecture. Importantly, redox signaling is a crucial regulator of stem cell quiescence, self-renewal, and differentiation. Conversely, loss of controlled redox signaling (oxidative stress) can obliterate stem cell function and promote cell senescence of stem and differentiated cells, two conditions that have been associated with the progressive loss of tissue renewal and reparative reserve that characterize aging.

Cardiac stem cells are not immune from these pathological processes, becoming dysfunctional and unable to effectively repair cardiac damage with organism aging and pathology. mTOR signaling, which associates with cardiac stem cell senescence, may affect redox signaling at multiple levels, overloading the endoplasmic reticulum, and inhibiting both lysosomal function and autophagy. Therefore, innovative interventions aimed at restoring proper redox signaling in primitive cells have the potential to reverse or attenuate age-associated stem cell dysfunction.

Enthusiasm for Rapamycin and Polypills in the Search for Ways to Slow Aging

The author of this paper is one of the more outspoken advocates in the research community when it comes to mTOR and rapamycin as a path to slowing the progression of aging. He keeps up quite the output of position papers, such as this one, which calls for immediate human trials of polypills made up of rapamycin and a brace of other drugs broadly used in treatment of age-related conditions, such as statins and metformin. I have to think that the evidence to date suggests this will be less effective than hoped, while still very plausibly being better than doing nothing, even considering the side-effects of the drugs involved. Effects in animal studies usually tend to be much more pronounced than effects in humans when it comes to slowing or preventing specific age-related diseases through pharmaceuticals.

If it was the only game in town, I'd be all for it, but there are far more effective ways forward towards the effective treatment of aging as a medical condition - approaches that aim at rejuvenation, not a mere slowing of aging. Still, I think the author here has the right general idea, in that the research community should move faster, the sooner plausible approaches are trialed the better, and that we should all pitch in to help, it is just that he is advocating a poor approach with a limited upside in comparison to other methodologies.

Inhibitors of mTOR, including clinically available rapalogs such as rapamycin (Sirolimus) and Everolimus, are gerosuppressants, which suppress cellular senescence. Rapamycin slows aging and extends life span in a variety of species from worm to mammals. Rapalogs can prevent age-related diseases, including cancer, atherosclerosis, obesity, neurodegeneration and retinopathy and potentially rejuvenate stem cells, immunity and metabolism. Here, I suggest how rapamycin can be combined with metformin, inhibitors of angiotensin II signaling (Losartan, Lisinopril), statins, propranolol, aspirin and a PDE5 inhibitor. Rational combinations of these drugs can maximize their anti-aging effects and decrease side effects.

At first, the discovery of anti-aging properties of rapamycin was met with skepticism because it challenged the dogma that aging is a decline driven by molecular damage caused by free radicals. By now, rapamycin has been proven to be an anti-aging drug. In contrast, anti-oxidants failed in clinical trials and the dogma was shattered. In the last decade, anti-aging effects of rapamycin have been confirmed. Anti-aging doses and schedules can be extrapolated from animal studies. Well-tolerated doses with minimal side effects can be deducted based on clinical use of rapalogs. So optimal anti-aging doses/schedules can be suggested. Given that rapamycin consistently extends maximal lifespan in mice, rapamycin will likely allow mankind to beat the current record of human longevity, which is 122 years. Yet, rapamycin will not extend life span as much as we might wish to. Now is the time for anti-aging drug combinations. For example, metformin is currently undergoing re-purposing as an anti-aging agent. Several other existing drugs can be re-purposed. Now we can design an anti-aging formula, using drugs available for human use.

Rapamycin (or another rapalog) should be a cornerstone of anti-aging combinations, given its universal anti-aging effect and the ability to delay almost all diseases of aging. Rapamycin and metformin: Both drugs extend lifespan in animals and have non- overlapping effects. In addition, they may, in theory, cancel possible metabolic side-effects of each other. Rapamycin and statins: Rapamycin promotes lipolysis increasing blood levels of fatty acids. This, in turn, increases levels of lipoproteins produced by the liver. Rapamycin-induced hyperlipidemia is benevolent and reversible. Still, statins are already used to prevent rapamycin-induced hyperlipidemia.

The 7-drug combination can be tested in mice, especially in mice on high fat diet and in cancer-prone mice. If started late in life, the experiments will take just several months to evaluate the effect on lifespan and cancer incidence as well as weight, blood pressure, glucose, insulin, triglycerides and leptin. In humans, the treatment program can be initiated regardless of any pre-clinical studies, because all 7 drugs are approved for human use and some of them such as aspirin and statin are widely used for disease prevention anyway. The only what is needed is to watch for side effects. Especially, heart rate, blood pressure, and glucose levels should be monitored.

The anti-aging formula is ready for human use. If one will wait until the life-extending effect will be shown in others, this individual will not be alive by the time of the result. Human clinical trials are needed to optimize the doses and schedules. However, unless we participate in clinical trials ourselves, we will not know how long participants will live because they are expected to outlive non-participants. If we want to live longer we should be participants in clinical trials. In the best scenario, this might allow us to live long enough to benefit from future discoveries of anti-aging remedies.


Evidence for Genetics to be a Challenging Road to Therapies for Age-Related Disease

Genetic engineering is now a fast path to cures for inherited diseases, those in which the cause is mutation in a single gene. Remove or suppress the bad gene, and insert the fixed version. This sort of approach, suppressing or editing a few specific genes, is unlikely to be as broadly and directly effective for age-related conditions, however. This is because, as is the case for aging, the disease state is influenced by thousands of genes, but directly caused by none of them. There are arguments, such as the research noted here, that suggest we should expect discoveries such as myostatin knockout for muscle growth, or ASGR1 and ANGPTL4 for reduced cardiovascular disease risk, to be unusual in the magnitude of their effects. When in search of genetic alterations to beneficially change a disease state, we should expect to come up more or less empty handed most of the time.

Here I am focused on the standard approach of editing or manipulating expression of one gene or a few genes, and not on more extensive engineering projects such as the SENS rejuvenation research program that aims to copy altered forms of mitochondrial DNA into the cell nucleus as a backup to remove the consequences of age-related damage to mitochondrial DNA. Or consider the Oisin Biotechnologies delivery of programmable DNA machinery to destroy a cell depending on its state. There will no doubt prove to be a role for other ambitious and essentially genetic reworkings of the cell, ways to improve redundancy of components or expand capabilities to ensure greater resilience, such as by providing a package of new enzymes capable of tackling problematic forms of metabolic waste.

This is, however, a very different class of approach to the single gene editing efforts that make up most of the field at present. This may be an era of medicine dominated by genetics, but we must, I think, recognize where it is limited as well as where there is the greatest potential. To my mind I see far too much enthusiasm for the sort of focus on genetic personalized medicine and single gene manipulations put forward by the likes of Human Longevity, to pick a representative example, while there just isn't enough of a benefit in their approach to be excited by it.

In a provocative new perspective piece, researchers say that disease genes are spread uniformly across the genome, not clustered in specific molecular pathways, as has been thought. The gene activity of cells is so broadly networked that virtually any gene can influence disease, the researchers found. As a result, most of the heritability of diseases is due not to a handful of core genes, but to tiny contributions from vast numbers of peripheral genes that function outside disease pathways. Any given trait, it seems, is not controlled by a small set of genes. Instead, nearly every gene in the genome influences everything about us. The effects may be tiny, but they add up.

The researchers call their provocative new understanding of disease genes an "omnigenic model" to indicate that almost any gene can influence diseases and other complex traits. In any cell, there might be 50 to 100 core genes with direct effects on a given trait, as well as easily another 10,000 peripheral genes that are expressed in the same cell with indirect effects on that trait. Each of the peripheral genes has a small effect on the trait. But because those thousands of genes outnumber the core genes by orders of magnitude, most of the genetic variation related to diseases and other traits comes from the thousands of peripheral genes. So, ironically, the genes whose impact on disease is most indirect and small end up being responsible for most of the inheritance patterns of the disease.

Researchers have thought of genetically complex traits as conforming to a polygenic model, in which each gene has a direct effect on a trait, whether that trait is something like height or a disease. In earlier work on the genetics of height, researchers were surprised to find that essentially the entire genome influenced height. "It was really unintuitive to me. To be honest, I thought that it was probably wrong. I gradually started to realize that the data don't really fit the polygenic model. We started to think, 'If the whole genome is involved in a complex trait like height, then how does that work?'"

The polygenic model leads researchers to focus on the short list of core genes that function in molecular pathways known to impact diseases. So, therapeutic research typically means addressing those core genes. A common approach to gene discovery is to do larger and larger genome-wide association studies, but the team argues against this approach because the sample sizes are expensive and the thousands of peripheral genes uncovered are likely to have tiny, indirect effects. "After you get the first 100 hits, you've probably found most of the core genes you're going to get through genomewide association studies." Instead, the team recommends switching to deep sequencing the core genes to hunt down rare variants that might have bigger effects. "If this model is right, it's telling us something profound about how cells work that we don't really understand very well. And so maybe that puts us a little bit further away from using genome-wide association studies for therapeutics. But in terms of understanding how genetics encodes disease risk, it's really important."


Aging is a Medical Problem that Should be Addressed

Aubrey de Grey of the SENS Research Foundation is the advocate and scientist at the center of a diverse network of people and organizations who, collectively, are changing the world when it comes to aging, medicine, and research. It wasn't so very long ago that the research community and its associated sources of funding were hostile towards any effort to consider the treatment of aging as a medical condition. Decades were lost to a scientific culture whose leading members wanted to distance themselves from "anti-aging" snake oil at any cost - including the sacrifice of any real possibility of progress. Change has come but slowly, and required outsiders such as de Grey to enter the research field and raise hell until the existing factions and establishments were forced to acknowledge the potential to extend healthy life and reverse the progression of age-related conditions. Younger researchers now benefit from a field in which they can build a better world, applying biotechnology to the causes of aging in order to alleviate this greatest cause of suffering and death. This field is no longer the poorly regarded backwater it once was, thanks to people like de Grey and his allies, but now one of the most exciting areas of modern life science research, the seed that will blossom into a vast and enormously beneficial industry in the years ahead.

Yet this is a transformation still in progress. The first battles have been won, the first rejuvenation therapies after the SENS vision of damage repair - those involving clearance of senescent cells - are well on their way to the clinic. But the majority of research programs and funding sources remain slow to change course. Funding for aging research remains minimal in comparison to funding for other areas of medicine. Where there is funding, it is still largely directed towards initiatives that cannot possibly do more than slightly slow aging, or merely patch over the symptoms of aging, as little attention is given to the cell and tissue damage that is the root cause of all age-related disease, dsyfunction, and death. Longevity science is a field in which the greatest challenge is not the discovery of great swathes of new information about aging, but rather to persuade the research community to make proper use of what is already known, and then fund that work sufficiently. All of the necessary classes of therapy needed for rejuvenation can be constructed based on the knowledge of twenty years ago; the development plans are set out in some detail. Yet all too much of the field remains focused on continued exploration of the details of aging as it operates in the absence of intervention.

This is where we come in. Our philanthropic support of organizations such as the Methuselah Foundation and SENS Research Foundation helps to move the research forward. Our investment in and support of startup companies working on SENS technologies helps to push meaningful therapies for aging closer towards the clinic. The growth and legitimacy of SENS and SENS-like rejuvenation research is something that our broader community has bootstrapped from an idea to its present state. We have succeeded to no small degree! There is much to do yet, however. Our ability to attract support to the most important lines of research and development has increased greatly in recent years, and will continue to soar as SENS approaches such as senescent cell clearance are proven out in trials and animal studies. Now is not the time to rest upon our laurels: so make a point to tell someone you know about the field of rejuvenation research, and that the promising therapies currently in development are the result of donations wisely made in past years. The more people who know today, the more supporters will join us in the years ahead, and this is far more a challenge of persuasion than a challenge of science at this stage.

Science Isn't The Reason That Humans Can't Live Forever

If humanity were to appoint a general in our war against aging, Aubrey de Grey would likely earn the honor. The British author and biomedical gerontologist has been on the front line for years, researching ways to free the world of age-related disease and, ultimately, extend human life indefinitely. From the SENS Research Foundation Research Center (SRF-RC) in Mountain View, CA, foundation scientists conduct proof-of-concept research with the goal of addressing the problems caused by aging. They focus on repairing damage to the body at the molecular level, and their work is helping advance the field of rejuvenation biotechnology.

SRF-RC teams are currently focusing on two equally complex-sounding research projects, one centered on allotopic expression (a way to bypass the harmful effects of age-caused mitochondrial mutations) and the other on telomerase-independent telomere elongation (a little-researched process by which some cancer cells overcome mortality). Either project could lead to major breakthroughs in anti-aging treatments, but as de Grey explains, the path to immortality doesn't just run through the science lab. While the research being conducted at the SRF-RC is far from simple, de Grey claims DNA mutations and cancer cells aren't the biggest hurdles to anti-aging breakthroughs: "The most difficult aspect of fighting age-related diseases is raising the money to actually fund the research." The nature of most science research is exploratory. Researchers don't know that what they're working on is going to yield the results they expect, and even if it does, turning basic research into income is no easy task. To support their work, most have to rely on funding from outside sources, such as government grants, educational institutions, or private companies.

"It's still an incredibly hard sell," de Grey claims. "We have very limited resources. We only have about 4 million dollars a year to spend, and so we spent it very judiciously." That money isn't going to just the two in-house projects, either. The SENS Research Foundation funds anti-aging research at institutions across the globe and provides grants and internships for students, so raising money to support those endeavors is key to continued success in its fight against aging. The benefits of ending the problem of aging would be tremendous. Not only would we be living longer, we'd be living healthier for longer.

Essential to raising money for anti-aging research is ensuring that those with the funds understands why it's worth the investment - a not-so-easy task given current misconceptions about aging. In 2015, eight major aging-focused organizations, released a report detailing what they call the many "notable gaps" that exist between expert perspectives on aging and the public's perception of the process. If the public isn't well informed on aging, it's even less knowledgeable about anti-aging. Fifty-eight percent of respondents in a 2013 Pew Research study said they had never even heard of radical life extension before. When asked if they would undergo treatments that would allow them to live to the age of 120 or older, the majority of those surveyed said they would not, and 51 percent thought such treatments would be "bad for society."

"There is still a huge amount of resistance to the logic that aging is bad for you and that it's a medical problem that needs to be addressed," explains de Grey. "It's really, really extraordinary to me that it's so hard to get this through to people, but that is the way it is. Aging is not mysterious. We understand it pretty well. It's not even a phenomenon of biology. It's more a phenomenon of physics. Any machine with moving parts is going to damage itself ... and the result is inevitably going to be that eventually the machine fails. It's the same for the human body as it is for a car, for example, and if we think about it that way, it becomes pretty easy to actually see what to do about it."

Cytomegalovirus Research in Immune Senescence Comes of Age

Researchers are these days feeling more confident in the identification of cytomegalovirus as a significant cause of immune system dysfunction in aging, as the conference report here illustrates. We might hope that this growing interest in cytomegalovirus in the context of aging will lead to more funding of means to repair the situation, aiming to restore some of the youthful capability to respond to pathogens and destroy potentially dangerous cells.

The immune system is an adaptable machine, but one with limits. In adults new immune cells are generated at a very slow pace in comparison to the overall count of such cells in circulation. This effectively produces what looks a lot like a limit on the number of immune cells. As the years pass, that limited population is increasingly taken over by endlessly duplicated memory cells specialized to cytomegalovirus. Uselessly specialized, as the immune system cannot effectively clear this virus from the body. Near everyone is infected by cytomegalovirus by the time old age is reached, but aside from its insidious long-term effects on the immune system, it causes no noticeable problems in the vast majority of people. Thus approaches to tackling it have not been given any great priority in the medical science community of past decades. When much of the immune system is overtaken by cytomegalovirus-specific cells, however, that leaves all too little room for cells capable of productively carrying out other functions, and the result is a failing immune system, characteristic of the old.

The best near-team approach to this problem is probably some form of selective destruction of the unwanted specialized immune cells, in order to free up capacity. That can be coupled with the generation of replacement immune cells from a patient cell sample, returned to the body to quickly make up the numbers. This is a very plausible goal, given the various trials and technology demonstrations of immune cell clearance for therapeutic purposes. The greatest challenge involved is to develop targeted cell destruction approaches that are safe and have minimal side effects for the patient, in comparison to the damaging pharmaceuticals used to date in human trials.

Nearly two decades ago, two key findings connected cytomegalovirus (CMV) with immune senescence. In 1999, researchers showed that CMV-positive and -negative humans exhibit dramatically different T cell subset ratios and that the effect seems to be increasing with aging. Around the same time, others described "memory inflation" driven by CMV in mice. Since then, numerous studies have been published investigating the associations between human, non-human primate or murine CMV with their respective hosts in the course of aging. The interest in the topic has been so sustained that it led to the establishment of CMV and Immunosenescence Workshops. This overview summarizes the state of the field before and the discussions at the 6th International CMV and Immunosenescence Workshop.

CMV, a member of beta-herpesvirus family, is the largest human virus. As is the case for other herpesviruses, following a brief acute infection period that elicits a typical CD8 T cell response, as well as CD4 and B cell responses, CMV establishes persistence that includes latency. Persistence/latency is established in reservoir cells that are distributed broadly across the organism. However, it is clear that the primary CMV infection is followed by a period of viral shedding and it remains unclear whether the virus, that is a master in immune evasion, ever really is truly latent in all its reservoirs or whether some cells produce it as a smoldering infection at low levels at most, if not all times. As a consequence, a large population of CMV-specific CD8, and to a lesser extent, CD4 T cells, is generated in response to cycles of viral reactivation (aptly called memory inflation). How exactly this memory inflation impacts the ability of an older immune system to function and provide defense against other infections is one of the key topics of interest.

The 6th International Workshop on CMV and Immunosenescence was organized with a primary goal to fill a gap identified at several recent meetings. Specifically, in addition to the topics reviewed above from the fifth workshop, it was felt that stronger attention must be focused on the biology of the virus itself and on its interactions with the host in the course of latency and reactivation. In fact, one of the greatest weaknesses of research into HCMV and immunosenescence comes from our inability to control and measure the state of viral activity. Another area of major interest is the impact of CMV on diseases on aging - whether and how the virus may be involved in modulating frequent age-related morbidities, in particular cardiovascular diseases (CVD), where there are strong epidemiological associations between CMV infection and morbidity and mortality from CVD.


Methylation of Ribosomal RNA Genes Correlates with Aspects of Aging

This paper is an example of the further explorations of DNA methylation and aging presently taking place in the research community. DNA methylation is one of the epigenetic decorations to DNA that alter gene expression, and thus the pace at which specific proteins are generated in the cell. A few different epigenetic clocks have been discovered in recent years, patterns of change in DNA methylation levels that correlate well with biological age, in that people of a given chronological age who are more damaged and impacted by aging than their peers tend to have distinctively different DNA methylation patterns. Moving beyond the existing epigenetic clocks, researchers are now searching for more and better correlations, as well as specific mechanistic links with other cellular processes already known to change with age.

Alteration of the ribosome biogenesis and an overall protein synthesis rate decline have been observed to characterize aging process in many organisms, including humans. This decline could be an effect of the progressive deterioration in most cellular functions usually associated with aging, or it could be a concurrent factor in the process. If to date a general reduction of protein synthesis has been attributed to the decreased frequency of mRNA translation, current studies, reporting an involvement of epigenetic mechanisms in silencing a large fraction of the ribosomal RNA (rRNA) genes, with a consequent impairment of ribosomal DNA (rDNA) function, could lead to a new understanding of the phenomenon.

On the basis of this evidence, we investigated whether changes in the DNA methylation patterns of the rRNA gene promoter take place during the lifetime. DNA samples were extracted from whole blood collected from differently aged human individuals displaying different phenotypes according to cognitive, functional, and psychological parameters. We did not find a consistent statistically significant association between the methylation levels of the analyzed CpG sites with the age of the donor. On the other hand, although it is not associated with chronological aging, in middle/advanced-aged subjects the variability of CpG_5 methylation was found to be significantly correlated with both cognitive performances and survival in the 9-year follow-up period. This last result, which held multiple test correction, was further confirmed in the replication sample.

Our results seem to be particularly attractive, because they show a fine remodeling of the methylation profile associated with the biological aging rather than to the chronological age. The effects at molecular levels of the above association have to be clarified, but it is plausible to hypothesize that the decrease in the rRNA levels we observed late in life may be determined by the methylation of the CpG_5 site that in turn might be driven by multiple factors, including genetic variations, diet, environment, and the interindividual variation of the structure of rDNA cluster itself.

How could the methylation changes of peculiar CpG sites be functionally involved in the functional decline characterizing the aging process? If the epigenetic modification of functional sites may hamper ribosomal biogenesis, this may drastically reduce the cellular protein synthesis, being ultimately responsible of those multisystem deficits occurring over the lifetime. Thus, an interdependence seems to exist between rDNA promoter methylation and the aging process, and in particular with the aging associated decay, and these sites may represent an potential evolutionary conserved biomarker of the rate of the aging process.


A Combination Cell and Gene Therapy Repairs Severe Bone Fractures

The progress in various approaches to gene therapy over the past decade has succeeded in reducing cost and increasing reliability. This has reached the point at which researchers can afford, from the point of view of both time and funding, to begin to combine gene therapies with other areas of medicine under development. In particular, reliable gene therapies targeting the controlling switches and dials of cell growth and regeneration should be a way to greatly improve the effectiveness of cell therapies and other, similar forms of regenerative medicine. The research reported below is a good example of the type, in which scientists combine a scaffold-based cell therapy with gene therapy to encourage local cells towards increased, controlled bone regrowth to replace severe fracture damage.

There are many methods of delivery for the introduction of therapeutic genes. The familiar use of viruses as a vector for the transfection of genes into a cell is just one class of approach - perhaps the most obvious one, given that viruses are in essence machines whose primary purpose is to place DNA into cells. But there are other approaches. Considered in the larger context, this diversity is a good thing, as greater competition and exploration always leads to a superior end result once all is said and done. The method used here is one of the pore-forming variations, in which one or another form of stimulus induces cells to open pores in the cell membrane and let in the DNA-bearing particles. In this case, the stimulus is physical, provided by cavitation of ultrasound-created microbubbles. It is worth bearing in mind that all of these methods have the potential to damage and kill cells, some more than others, and thus must be carefully calibrated. When it works, however, the results can be fairly impressive.

Injured Bones Reconstructed by Gene and Stem Cell Therapies

Investigators have successfully repaired severe limb fractures in laboratory animals with an innovative technique that cues bone to regrow its own tissue. If found to be safe and effective in humans, the pioneering method of combining ultrasound, stem cell and gene therapies could eventually replace grafting as a way to mend severely broken bones. "We are just at the beginning of a revolution in orthopedics. We're combining an engineering approach with a biological approach to advance regenerative engineering, which we believe is the future of medicine."

The new technique could provide a much-needed alternative to bone grafts. In their experiment, the investigators constructed a matrix of collagen, a protein the body uses to build bones, and implanted it in the gap between the two sides of a fractured leg bone in laboratory animals. This matrix recruited the fractured leg's stem cells into the gap over two weeks. To initiate the bone repair process, the team delivered a bone-inducing gene directly into the stem cells, using an ultrasound pulse and microbubbles that facilitated the entry of the gene into the cells. Eight weeks after the surgery, the bone gap was closed and the leg fracture was healed in all the laboratory animals that received the treatment. Tests showed that the bone grown in the gap was as strong as that produced by surgical bone grafts.

In situ bone tissue engineering via ultrasound-mediated gene delivery to endogenous progenitor cells in mini-pigs

We hypothesized that localized ultrasound-mediated, microbubble-enhanced therapeutic gene delivery to endogenous stem cells would induce efficient bone regeneration and fracture repair. To test this hypothesis, we surgically created a critical-sized bone fracture in the tibiae of Yucatán mini-pigs, a clinically relevant large animal model. A collagen scaffold was implanted in the fracture to facilitate recruitment of endogenous mesenchymal stem/progenitor cells (MSCs) into the fracture site. Two weeks later, transcutaneous ultrasound-mediated reporter gene delivery successfully transfected 40% of cells at the fracture site, and flow cytometry showed that 80% of the transfected cells expressed MSC markers. Human bone morphogenetic protein-6 (BMP-6) plasmid DNA was delivered using ultrasound in the same animal model, leading to transient expression and secretion of BMP-6 localized to the fracture area.

Micro-computed tomography and biomechanical analyses showed that ultrasound-mediated BMP-6 gene delivery led to complete radiographic and functional fracture healing in all animals 6 weeks after treatment, whereas nonunion was evident in control animals. Collectively, these findings demonstrate that ultrasound-mediated gene delivery to endogenous mesenchymal progenitor cells can effectively treat nonhealing bone fractures in large animals, thereby addressing a major orthopedic unmet need and offering new possibilities for clinical translation.

How to Speed Up the Development of Rejuvenation Biotechnology?

While it certainly seems a long time - and that we have come a long way - since the years in which SENS rejuvenation research was only an idea, and the research community was generally hostile towards the idea of treating aging as a medical condition, these are really still the early stages of the upward curve in the bigger picture. That curve leads to a mainstream research community as consumed by the effort to bring aging under medical control as it is presently consumed by work on cancer and stem cell science - and a public at large who support an end to aging just as greatly as they presently support an end to cancer. We'd all like it to go faster.

As our community of scientists, advocates, and supporters grows, the diversity of opinions on what we should be doing in order to speed up progress towards working rejuvenation therapies will also grow. I think this to be a good thing. The more approaches out there being tried in earnest, the more likely that one or another group will find ways to effectively speed up the present phase of the bootstrapping process. There will be disagreements, of course, and I disagree with some of the details in the piece linked here, but so what? Each to their own. Proof of correctness lies in implementations that effectively move the needle, not in opinion. If you have an idea, get out there and try it.

We have made huge strides in the last decade or so and we know a great deal about the processes and damages aging causes, but sadly this does not mean we know enough. There is much more to be learned in order to develop effective interventions and therapies to address these processes, and this is where basic science comes in. The countdown to accessible therapies against aging will not start unless each mechanism of aging is well understood. If all of them were understood right now, you would still need to wait for another 17 years to get a full range of therapies against aging. If you add 17 years to your current age and don't like the resulting number and its relation to the onset of age-related diseases, then ask yourself this, is supporting basic research on aging now in your interest? You may not be very excited about life extension in mice, but remember, no results in mice equals no translation to humans.

It is true the government funds research institutions and awards research grants. But the idea of preventing age-related diseases by addressing its underlying mechanisms is relatively new. There are not many experts among the decision makers in the grant system who can assess the breakthrough projects aimed at the hallmarks of aging and truly understand their potential. This is why these kinds of projects have less support from the government than the mainstream studies of a single disease like Alzheimer's or cancer.

In the case of government funding, the money goes from the taxpayer to the government treasury, where its future allocation is decided, and then to specific research institutions whose plan of research falls within the mainstream priorities. This makes it very hard for our community to influence the direction of research, which is a serious limitation indeed. Crowdfunding does not have this limitation, because it allows the public to connect with the researchers directly and support only the projects they believe are important. The amount of money collected during a crowdfunding campaign can be as much as a government grant (often even bigger), plus there is no need for the excessive paperwork typical for a government grant. This means that the researchers can focus on what they do best of all: their studies.

The number of ardent supporters of aging and longevity studies is relatively small due to the slow dissemination of information from scientists to the public. Most people still believe there is nothing we can do about biological aging, and so they see these studies as researchers simply feeding their scientific curiosity. Education regarding the plausibility and desirability to defeat aging takes time, patience and a lot of effort. It cannot be done by the scientists themselves (as their job is to work in the lab, not to make shows), and here is where advocacy groups and science popularizers should step in. However, people tend to forget that the best results can only be achieved if a group is well-organized, disciplined and uses evidence-based practices in all activities, from planning and management to crowdfunding, educating and lobbying. Steady progress requires a mindful and responsible approach from each person joining an advocacy group - which is sadly rarely seen.

Many members of our community prefer to profess their desire for indefinite lifespans directly, shocking the public. It is important properly explain the connection between aging and age-related diseases, and the causal relationship between aging prevention, health improvement, and longevity - longevity being a side-effect of better health. Being patient and addressing concerns people may have in relation to longer lives (like overpopulation, unequal access, boredom and others) is another important job which is rarely done properly, with enough supporting data to hand. Despite the fact that most of the sociological studies on public attitudes regarding life extension are available to read and have even been summarized by different members of the community, many people still refuse to explain the basics, or insist on using counterproductive radical messages, provoking additional skepticism and closing doors that would otherwise be open. Before starting a conversation with someone who is not familiar with the idea of healthy life extension, it would be useful to take a look at the existing data regarding how to make such conversation productive.


Senescent Cells as a Cause of Age-Related Fatty Liver Disease

Fatty liver disease, or hepatic steatosis, is both age-related and self-inflicted in the sense that in most sufferers the primary cause appears to be the metabolic dysfunction that accompanies obesity, but the risk also rises with age, and even an exemplary life can sometimes eventually result in the appearance of this condition. Chronic inflammation may play an important role in the development of fatty liver disease without obesity, and whenever that it is the case it is sensible to immediately turn to the age-related accumulation of senescent cells as a potential contributing mechanism, as these cells are a potent source of inflammatory signals. The researchers here do just that, and in the course of their work demonstrate that senescent cells are in fact an important cause of the problem, just as they are for many other age-related conditions. This is good news for patients with fatty liver disease, and those destined to be patients absent an effective treatment, given the present pace of progress towards senolytic therapies capable of safely and selectively destroying these unwanted and harmful cells.

Non-alcoholic fatty liver disease (NAFLD) is characterized by excess hepatic fat (steatosis) in individuals who drink little or no alcohol. NAFLD is more prevalent in older populations. The mechanisms underlying this condition are not understood nor is why its prevalence increases with ageing. It has been speculated that ageing processes may promote NAFLD via different mechanisms, including adipose tissue dysfunction, impaired autophagy, and oxidative stress.

Cellular senescence is a state of irreversible cell-cycle arrest, which can be induced by a variety of stressors, including telomere dysfunction and genotoxic and oxidative stress. Senescent cells frequently have increased secretion of a broad repertoire of proinflammatory factors, collectively known as the senescence-associated secretory phenotype, which can induce tissue dysfunction in a paracrine manner. Senescent cells have mitochondrial dysfunction, with decreased oxidative phosphorylation and concomitantly increased generation of reactive oxygen species (ROS), caused at least partly by failing mitophagy.

A significant fraction of hepatocytes develop a senescent phenotype during the life course of mice and with age-related liver disease in humans. However, the relationship between cellular senescence and liver fat accumulation remains unclear. Here we hypothesized that cellular senescence results in impaired fat metabolism and that removal of senescent cells may diminish liver steatosis.

We found a close relationship between senescence markers and fat accumulation in hepatocytes of mice fed ad libitum (AL), dietary restricted (DR) or following dietary crossover and in a small cohort of NAFLD patients. Furthermore, clearance of senescent cells by suicide gene-meditated ablation of p16Ink4a-expressing senescent cells in INK-ATTAC mice and a senolytic cocktail of dasatinib plus quercetin reduced overall hepatic steatosis in ageing, obese, and diabetic mice. In contrast, hepatocyte-specific induction of senescence by a local DNA repair defect resulted in liver steatosis. Finally, we found that induction of senescence in mouse fibroblasts and hepatocytes resulted in decreased ability to metabolize fat. Our findings suggest that interventions targeting senescent cells may be developed into therapies to reduce steatosis during NAFLD.


Common Human Growth Hormone Receptor Variant Associated with Greater Longevity

The longest lived laboratory mice, more than a decade after the creation of the first lineage, are still those with impaired growth hormone signaling. That record has yet to be overtaken, and I suspect that it may well stand unbroken until the development of rejuvenation therapies based on damage repair is further advanced, and senescent cell clearance is joined by other types of therapy, their effects adding together. Thus growth hormone and growth hormone receptor genes in humans are one of the places to look for variants and mutations that might improve our understanding of how metabolism influences aging, and as a bonus for those interested in pharmacological or genetic adjustment of metabolism, may lead to ways to modestly slow aging.

With this in mind, attention has fallen on a rare human lineage with a growth hormone receptor mutation that produces dwarfism, the Laron syndrome population. Unfortunately it isn't yet possible to say whether or not these individuals have any advantage over the rest of us when it comes to longevity. They do appear to be resistant to cancer and type 2 diabetes, though the evidence in support of that conclusion isn't completely iron-clad at this point. People with Laron syndrome and, separately, people who practice calorie restriction for its health benefits can be compared with the same processes operating in mice. When doing so, we can see that human longevity is not enormously changed, while mouse longevity does increase by up to 70% for growth hormone disruption, and up to 40% for calorie restriction. That degree of gain is certainly not the case in humans. Evolution has delivered a much more plastic life span to short-lived mammals, responsive to environmental circumstances, and with a biochemistry capable of these large changes in the pace of aging.

Putting growth hormone signaling to one side for the moment, considerable effort has been devoted over the years to the broader search for human genetic variants that are associated with longevity. The consensus on genes and longevity is that individual variations in your genome have little influence over aging until later life, and from that point forward, the older and more damaged you get the more that genetic variation matters. Nonetheless, the search has found very few compelling associations. There is solid evidence for variants in APOE and FOXO3A, and less solid evidence for a few other variants such as in TXNRD1, but these are not large effects. Beyond this there are scores of other associations that are never replicated, showing up in only one study or one population, and again with small effects - by which I mean maybe you have a 1.5% chance of living to 100 instead of a 1% chance if you held one of these variants. The big picture is of hundreds or thousands of individually tiny effects; which of these genes and variants are more or less relevant varies widely between populations and individuals, and is very dependent on environmental factors.

That said, there are genetic variants with sizable effects on resistance to specific age-related disease, such as those in ASGR1 or ANGPTL4, both of which reduce blood cholesterol and cardiovascular disease risk. Nothing is published on their effects on longevity at this time, but give it time. Should we believe that there are human genetic variants that meaningfully increase life expectancy in the carriers based on what we've seen to date? The association studies with their poor catch of results suggest no. The existence of the variants mentioned above suggest maybe, but equally it is the case that aging has many facets. Being resistant - or even immune - to one thin facet, such as cardiovascular disease, is thought unlikely to do a great deal to overall longevity. It just means that something else gets you in the end, perhaps a couple of years later.

Returning to growth hormone metabolism, I see that researchers are claiming that a common human gene variant of growth hormone receptor, per their statistics, may result in a ten year difference in life expectancy. This is replicated in multiple study populations, but the effect appears only in men. It is interesting, but there is every reason to be cautious with this sort of very statistical genetic association study. I'd say read the paper and put it aside until someone replicates the result. Would a ten year gain from a growth hormone signaling genetic variant be surprising if this turns out in fact be the case? Maybe not, given what we know about the relative sizes of effects in mice and humans. Ten years is about on the outside end of variations that can plausibly exist in some numbers and yet blend in with broader population data, and the effects in mice are considerably larger on a relative basis.

The GH receptor exon 3 deletion is a marker of male-specific exceptional longevity associated with increased GH sensitivity and taller stature

Growth hormone (GH) and insulin-like growth factor (IGF) play a central role in development, differentiation, growth, and metabolism among divergent taxa. Dwarf individuals appear to live longer among many species, suggesting a role for the GH/IGF-1 axis in modulating aging and life span. A considerable body of in vitro experimental evidence also suggests an important role for the IGF axis in human longevity and aging-related processes in a tissue-specific manner. Furthermore, several studies in selected human populations lend support on the role of this axis in health and life span.

For instance, we have previously identified a cluster of functional mutations in the IGF-1 receptor in centenarians. We showed that Laron dwarfs, who are naturally short, have decreased prevalence of diabetes, cancer, and stroke, suggesting increased health span although life span in this small sample size cannot be determined accurately. Also, we previously established that centenarians with lower levels of IGF-1 had significantly longer survival. Clearly, individuals with severe GH deficiency have reduced life expectancy, suggesting that some GH is necessary for survival. On the other hand, interventional GH therapy in humans is commonly used to reverse age-related morbidities; hence, the kind of deficiency that will be most beneficial for health span and longevity needs to be further established.

GH production is decreased with age; however, it is never completely diminished. That said, there is accumulating evidence that GH may play a crucial role in modulating aging. Surprisingly, GH deficiency or diminished secretion has been linked to longevity phenotypes both in mice models and in humans with familial longevity. The GH receptor (GHR) gene has nine coding exons and consists of two common isoforms: (i) full-length GHR-flGHR and (ii) a shorter form with a deletion of exon 3, d3-GHR. The allele frequencies of these isoforms among human populations range from 68-90% for flGHR and 10-32% for d3-GHR.

Investigations of the effects of GHR isoforms on human health have provided mixed results. In two Genome Wide Association Studies (GWAS) based on single-nucleotide polymorphisms (SNPs), the GHR locus showed association with final height. However, to our knowledge, the association of d3-GHR with final height has not been examined, possibly because individuals with d3-GHR are expected to maintain normal GH action despite lower GH production. It is reasonable to hypothesize that increased GH sensitivity can also alter IGF-1 secretion and therefore regulate longevity. Given the potential role of the GH/IGF axis in longevity, we hypothesize that low IGF-1 levels will assure longevity of the d3-GHR carriers. To address this hypothesis, we genotyped the d3-GHR locus in four human cohorts with long-lived participants, and we tested its association with longevity-related phenotypes and stature with a relatively common GHR variation.

In Ashkenazi males, but not in females, a marked difference in allele frequency for the exon 3 deletion polymorphism (d3-GHR) was found between centenarian and control, as well as offspring and control groups. Whereas the male control group carried only 4% homozygote deletions, male offspring of centenarians and male centenarians carried 11 and 12%, respectively. We further validated these results in three independent cohorts - the Old Order Amish (OOA), Cardiovascular Health Study (CHS), and the French Long-Lived Study (FLLS). These results demonstrate a consistent relationship between homozygosity for the d3-GHR deletion allele and longevity among the cohorts studied. However, this observation was limited only to males; the frequency of d3-GHR deletion homozygosity among females did not differ with age in any of the cohorts studied. On average, d3/d3 homozygotes were 1 inch taller than the wild-type (WT) allele carriers and also showed lower serum IGF-1 levels. Multivariate regression analysis indicated that the presence of d3/d3 genotype adds approximately 10 years to life span.

It appears that deletion of the GHR gene exon 3 might have originated from complex genomic events taking place after the emergence of Old World monkeys, followed by homologous recombination between two retro-elements in Homo sapiens. Thereafter, it spread throughout the human clades to be present now in approximately 25% of Caucasian chromosomes. In centenarians, most IGF-1 regulation seems to respond to caloric and protein nutritional signals, not from GH. IGF-1 is not lower in carriers of d3-GHR during childhood, adolescence, and adulthood despite several reports showing that the GHR genotype may influence circulating IGF-1 under basal conditions. People with d3-GHR or fl-GHR alleles produce comparable amounts of circulating IGF-1. That said, we suspect people with d3-GHR alleles to have a decreased GH secretion.

Yeast Life Extension via Lithocholic Acid Provides Support for the Membrane Pacemaker Hypothesis of Aging

A fair amount of aging research starts in yeast (or worms, or flies) for reasons of cost, only later moving to mammals such as laboratory mice. A surprisingly large fraction of the cellular mechanisms relevant to aging are much the same in all of these species. Most of the ways in which metabolism determines natural variations in longevity, both between individuals and between species, were established very early in the evolution of cellular life. With this in mind, you might recall researchers demonstrating earlier this year that life span in yeast can be extended via provision of lithocholic acid. The open access paper here follows that with a consideration of the mechanisms involved: it appears to work via alteration of the composition of mitochondria, making them more resistant to damage.

The membrane pacemaker theory of aging puts mitochondrial composition front and center, based on comparisons of mitochondria between species with very different life spans. Longer-lived species tend to have mitochondria built out of more resilient lipids - though in this paper the researchers suggest that such differences in lipid composition are far more influential in the cell than simply a matter of damage resistance. Mitochondrial function and mitochondrial damage are any case considered to be very important in aging. Loss of mitochondrial activity is seen in many age-related diseases, and some forms of damage to mitochondria appear capable of creating dysfunctional cells that export harmful reactive molecules into the surrounding tissues. Restoring mitochondria to youthful function in the aged is an important component of rejuvenation research.

Mitochondria are indispensable for organismal physiology and health in all eukaryotes. The efficiencies with which these organelles generate the bulk of cellular ATP and make biosynthetic intermediates for amino acids, nucleotides, and lipids are known to deteriorate with age. Such age-related deterioration of mitochondrial functionality is the universal feature of aging in evolutionarily distant eukaryotic organisms.

A number of mechanisms underlie the essential roles of some traits of mitochondrial functionality in both modes of yeast aging. These traits in replicatively and chronologically aging yeast include mitochondrial electron transport chain and oxidative phosphorylation, membrane potential, reactive oxygen species (ROS) homeostasis, protein synthesis and proteostasis, iron-sulfur cluster formation, and synthesis of amino acids and NADPH. Until recently, it was unknown if such trait of mitochondrial functionality as the composition of mitochondrial membrane lipids can influence aging in yeast. Our recent studies have revealed that lithocholic bile acid (LCA) can delay the onset and decrease the rate of yeast chronological aging. We demonstrated that the robust geroprotective effect of exogenously added LCA is due to its ability to cause certain changes in lipid compositions of both mitochondrial membranes. These changes in mitochondrial membrane lipids enable mitochondria to establish and maintain an aging-delaying pattern of the entire cell.

This LCA-driven remodeling of mitochondrial lipidome triggers major changes in mitochondrial abundance and morphology and also alters mitochondrial proteome. These changes in the abundance, morphology, and protein composition of mitochondria lead to specific alterations in mitochondrial functionality. Our recent unpublished data indicate that the LCA-dependent alterations in mitochondrial lipidome, proteome, and morphology can also elicit changes in lipidomes of other organelles and in concentrations of a specific set of water-soluble metabolites. By sensing different aspects of mitochondrial functional state, a discrete set of ten transcription factors orchestrates a distinct transcriptional program for many nuclear genes. The denouement of this cascade of consecutive events is the establishment of a cellular pattern that delays the onset and slows the progression of yeast chronological aging.

Of note, the proposed mechanism here for how the LCA-dependent remodeling of mitochondrial lipidome in the yeast S. cerevisiae allows to establish an aging-delaying cellular pattern is reminiscent of the mechanism in which the mitochondrial unfolded protein response causes remodeling of the mitochondrial lipidome in the nematode C. elegans, and then triggers a cascade of events that institute an aging-delaying cellular pattern. Moreover, the essential role of mitochondrial lipid metabolism in defining the pace of yeast chronological aging further supports the notion that the vital role of lipid homeostasis in healthy aging has been conserved in eukaryotes.


Mutant Dietary Bacteria as a Way to Explore Mechanisms of Aging in Nematodes

Researchers here outline a novel method of searching for longevity-related mechanisms in nematode worms: mutate the bacteria that the worms eat. The researchers worked their way through a selection of bacterial mutations, and along the way uncovered a few items of interest for further exploration. I think the leap made by press and publicly materials to supplements for human consumption containing mutated bacteria is getting far ahead of the science, however. This is, as of the moment, really only a demonstration of a new method of discovery in a commonly used laboratory species.

Scientists have identified bacterial genes and compounds that extend the life of and also slow down the progression of tumors and the accumulation of amyloid-beta, a compound associated with Alzheimer's disease, in the laboratory worm C. elegans. "The scientific community is increasingly aware that our body's interactions with the millions of microbes in our bodies, the microbiome, can influence many of our functions, such as cognitive and metabolic activities and aging. In this work we investigated whether the genetic composition of the microbiome might also be important for longevity."

This question is difficult to explore in mammals due to technical challenges, so the researchers turned to the laboratory worm C. elegans, a transparent, simple organism that is as long as a pinhead and shares essential characteristics with human biology. During its 2 to 3 week long lifespan, the worm feeds on bacteria, develops into an adult, reproduces, and progressively ages, loses strength and health and dies. Many research laboratories around the world work with C. elegans to learn about basic biological processes.

Researchers employed a complete gene-deletion library of bacterium E. coli; a collection of E. coli, each lacking one of close to 4,000 genes. "We fed C. elegans each individual mutant bacteria and then looked at the worms' life span. Of the nearly 4,000 bacterial genes we tested, 29, when deleted, increased the worms' lifespan. Twelve of these bacterial mutants also protected the worms from tumor growth and accumulation of amyloid-beta." Further experiments showed that some of the bacterial mutants increased longevity by acting on some of the worm's known processes linked to aging. Other mutants encouraged longevity by over-producing the polysaccharide colanic acid. When the scientists provided purified colanic acid to C. elegans, the worms also lived longer. Colanic acid also showed similar effects in the laboratory fruit fly and in mammalian cells cultured in the lab.

Interestingly, the scientists found that colanic acid regulates the fusion-fission dynamics of mitochondria, the structures that provide the energy for the cell's functions. "These findings are also interesting and have implications from the biological point of view in the way we understand host-microbe communication. Mitochondria seem to have evolved from bacteria that millions of years ago entered primitive cells. Our finding suggests that products from bacteria today can still chime in the communication between mitochondria in our cells. We think that this type of communication is very important and here we have provided the first evidence of this. Fully understanding microbe-mitochondria communication can help us understand at a deeper level the interactions between microbes and their hosts."


Revisiting Whole Body Induced Cell Turnover as a Therapeutic Strategy

Last year some of the researchers associated with the Biogerontology Research Foundation proposed a class of therapy they call whole body induced cell turnover. I noticed a new paper and publicity materials on this topic today. In essence the goal is to augment the normal processes of cell turnover with therapies that remove and replace more cells than would normally be the case, thus clearing out the damage in those cells along the way. Since aging is caused by cell and tissue damage, in the ideal case this approach should act as a form of rejuvenation therapy. Obviously there are some limits here, such as areas of the brain where cells are storing the state of the mind, but in principle all other tissues are amenable to cell replacement. Beyond that, however, there is also the question of damage outside cells, such as waste compounds in tissue fluids and within the extracellular matrix structures that support cells. Further, consider signals propagated by damaged cells in one part of a tissue that affect normal cells elsewhere, such as the inflammation spurred by senescent cell signaling.

That said, it is nonetheless clear that the logical long-term direction for tissue engineering and regenerative medicine strategies must be to move towards more incremental, in-situ, small-scale replacement of damaged parts. Practical tissue engineering in the years immediately ahead will certainly start with tissue sections and organs grown in bioreactors and then transplanted into patients. Surgery is expensive and traumatic, however, and especially so in the old. In order to avoid those costs, all treatments will ultimately involve manipulation and repair of cell populations in the body, with the complexity baked into the therapeutics, and little human supervision of their progression required. This might be accomplished by delivery of signals, delivery of cells, or various other more sophisticated therapeutics, but there will be no surgery and no construction of tissue outside the body.

It is easy enough to point out the underpinnings of this trend, and theorize at the high level as to how to make it a reality, but the implementation details are of great importance - they are the whole of the story, in fact. Replacing cells in a way that is safe, and that also removes cellular damage rather than propagating it, isn't a straightforward task with an obvious solution, for all that there are plenty of starting points in today's biotechnology industry and research community. Strategies will likely vary considerably from tissue to tissue. It is likely that much more of the biochemistry of natural regenerative processes must be mapped and understood, so as to avoid interfering in counterproductive ways. Targeted cell destruction technologies must evolve into more sophisticated and discriminating forms. And so on. It is a big task and an expansive vision for the future of medicine.

Induced Cell Turnover: A proposed modality for in situ tissue regeneration and repair

Researchers originally proposed Induced Cell Turnover (ICT) in 2016. The proposed therapeutic modality would aim to coordinate the targeted ablation of endogenous cells with the administration of minimally-differentiated, hPSC-derived cells in a gradual and multi-phasic manner so as to extrinsically mediate the turnover and replacement of whole tissues and organs with stem-cell derived cells. In a new paper the authors refine the methodological underpinnings of the approach, take a closer look at potential complications and strategies for their deterrence, and analyze ICT in the context of regenerative medicine as an intervention for a broader range of conditions.

"One of the major hurdles limiting traditional cell therapies is low levels of engraftment and retention, which is caused in part by cells only being able to engraft at locations of existing cell loss, and by the fact that many of those vacancies have already become occupied by extracellular matrix (ECM) and fibroblasts (i.e. scar tissue) by the time the cells are administered, long after the actual occurrence of cell loss. The crux underlying ICT is to coordinate endogenous cell ablation (i.e. induced apoptosis) with replacement cell administration so as to manually vacate niches for new cells to engraft, coordinating these two events in space and time so as to minimize the ability for sites of cell loss to become occupied by ECM and fibroblasts. This would be done in a gradual manner so as to avoid acute tissue failure resulting from the transient absence of too many cells at any one time. While the notion of endogenous cell clearance prior to replacement cell administration has become routine for bone marrow transplants, it isn't really on the horizon of researchers and clinicians working with solid tissues, and this is something we'd like to change."

Cell-type and tissue-specific rates of induced turnover could be achieved using cell-type specific pro-apoptotic small molecule cocktails, peptide mimetics, and/or AAV-delivered suicide genes driven by cell-type specific promoters. Because these sites of ablation would still be "fresh" when replacement cells are administered, the presumption is that the patterns of ablation will make administered cells more likely to engraft where they should, in freshly vacated niches where the signals promoting cell migration and engraftment are still active. By varying the dose of cell-type targeted ablative agents, cell type and tissue-specific rates of induced turnover could be achieved, allowing for the rate and spatial distribution of turnover to be tuned to the size of the tissue in order to avoid ablating too many cells at once and inadvertently inducing acute tissue failure.

"ICT could theoretically enable the controlled turnover and rejuvenation of aged tissues. The technique is particularly applicable to tissues that are not amenable to growth ex vivo and implantation (as with solid organs) -- such as the vascular, lymphatic, and nervous systems. The method relies upon targeted ablation of old, damaged and/or senescent cells, coupled with a titrated replacement with patient-derived semi-differentiated stem and progenitor cells. By gradually replacing the old cells with new cells, entire tissues can be replaced in situ. The body naturally turns over tissues, but not all tissues and perhaps not optimally."

Induced Cell Turnover: A novel therapeutic modality for in situ tissue regeneration

Induced Cell Turnover (ICT) is a theoretical intervention in which the targeted ablation of damaged, diseased and/or nonfunctional cells is coupled with replacement by partially differentiated induced pluripotent stem cells in a gradual and multi-phasic manner. Tissue-specific ablation can be achieved using pro-apoptotic small molecule cocktails, peptide mimetics, and/or tissue-tropic AAV-delivered suicide genes driven by cell-type specific promoters. Replenishment with new cells can be mediated by systemic administration of cells engineered for homing, robustness, and even enhanced function and disease resistance. Otherwise, the controlled release of cells can be achieved using implanted biodegradable scaffolds, hydrogels, and polymer matrices. In theory, ICT would enable in situ tissue regeneration without the need for surgical transplantation of organs produced ex vivo, and addresses non-transplantable tissues (such as the vasculature, lymph nodes, skin and nervous system). We have outlined several complimentary strategies for overcoming barriers to ICT in an effort to stimulate further research at this promising interface of cell therapy, tissue engineering, and regenerative medicine.

Using Photosynthetic Microbes to Oxygenate Ischemic Tissue

Ischemic injuries, in which insufficient oxygen is delivered to tissues, can occur in numerous ways, but heart attacks are among the most common, evident, and dangerous. A sizable branch of the research community works on ways to efficiently and quickly provide oxygen to the impacted tissues so as to reduce the long-term damage and speed recovery. At the end of this road lie permanent enhancements such as respirocyte nanomachinery that will provide hours of supplemental oxygen for all tissues, but for now researchers are still working on the first potential advances in emergency oxygen supplementation, such as the example noted here.

The use of photosynthetic microorganisms to provide much needed oxygen to damaged heart tissue could be a feasible approach to treating heart attacks. Recent research describes the injection of the cyanobacterium Synechococcus elongatus into ischemic heart muscles of live rats, where, in response to light exposure, the microbes produced oxygen and improved organ function. Photosynthetic organisms capture energy from sunlight and use it to convert carbon dioxide and water into carbohydrates for growth. The process creates a surplus of oxygen, which the organisms simply expel into the atmosphere, much to the delight of aerobic organisms such as humans. "One day I was thinking: what is the fundamental problem with a heart attack? It's the absence of oxygen being delivered to the heart muscle. And, what in nature makes oxygen for us every single minute? Plants."

"Cardiologists are always thinking about how to deliver more blood to ischemic heart tissue. But, if oxygen is the critical component, what if you could take a plant, or the photosynthetic mechanism of a plant, and put it right next to a heart cell?" To investigate this unusual idea, researchers took an equally unusual approach. "We started grinding up kale and spinach to isolate the chloroplasts and put them with heart cells." But the results of these experiments were disappointing. "What we found is that chloroplasts do not like being outside of a plant cell. They're not very stable."

So, the team instead tried the photosynthetic unicellular microorganism S. elongatus. "We put them with heart cells in a dish and we found that they could live together and, when we shone light on them, they could produce oxygen." The team then tested the idea in live rats. They gave the animals heart attacks and then injected their hearts with S. elongatus and exposed the hearts to light. After just 10 minutes, oxygen in the bacteria-containing and light-exposed hearts had risen approximately 25-fold compared with just a 3-fold rise in oxygen in bacteria-containing hearts kept in darkness. And by 45 minutes, left ventricle pressure and cardiac output had improved, suggesting increased heart contractility. The microbes also provided long-term improvements to heart function. Four weeks after rats were subjected to temporary cardiac ischemia (60 minutes) - during which the animals were, or were not, injected with S. elongatus and exposed to light - analyses of heart function revealed that recipients of the microbe treatment had significantly improved contractility compared with controls.


Weak Evidence for Amino Acid Processing Dysfunction Theories of Sarcopenia

One of the theories relating to causes of sarcopenia, the characteristic loss of muscle mass and strength with age, is that it relates to dysfunction in the processing of amino acids such as leucine. There is evidence for leucine supplementation to help slow the progression of sarcopenia, for example. The research here adds more along these lines, though it seems the authors will have to run a redesigned study to see whether or not the cellular differences observed actually produce meaningful results over a longer period of time:

The loss of skeletal muscle mass and quality is common with aging. This loss highlights the development of sarcopenia, where diminished muscle mass and strength are major contributors engendering loss of independence and quality of life for older adults. Current research suggests that reductions in the ability to stimulate muscle protein synthesis and promote proliferation and differentiation of muscle satellite cells may be important contributors to the development of sarcopenia.

It is well known that exercise and the ingestion of essential amino acids (EAA), in particular the amino acid leucine, are important stimulators of muscle protein synthesis through activation of the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway. While an anabolic resistance to the independent effects of exercise and EAA or protein is prevalent with aging, combining the two stimuli shows promise in combating sarcopenia via the ability for this combination to maximally stimulate mTORC1 and upregulate the translation initiation machinery. Indeed, we have recently demonstrated that provision of leucine-enriched EAA mixture following a bout of high-intensity resistance exercise (RE) stimulates mTORC1 and prolongs myofibrillar protein synthesis for up to 24 hours post-RE in the very same cohort of older men we examined in this study whereas, in the absence of EAA this mTORC1 response is blunted in older adults.

A host of evidence has suggested increased satellite cell (SC) activation and content following RE in human skeletal muscle, yet we and others have demonstrated a blunting of or a delayed ability to activate and increase the SC pool in older men compared with a younger cohort. EAA and leucine provision has been shown to upregulate SC activity via mTORC1. Therefore, we hypothesized that EAA ingestion, which we have previously shown to potently activate mTORC1 following an acute bout of leg resistance exercise, would enhance skeletal muscle satellite cell proliferative capacity and content in older men. We demonstrate that older men do not appear to increase skeletal muscle satellite cell content at 24 hours following heavy, high volume resistance exercise in the absence of EAA ingestion. However, when 10g of EAA is ingested one hour postexercise we found that MHC I myofiber satellite cell content displays obvious trends to be greater than when older men are not given postexercise EAA. Although this pattern is visually evident in MHC II myofibers and when all myofibers are pooled, the current data set did not reach statistical significance.


Recent Examples of the Road to Pharmacological Enhancement of Muscle Regeneration

Numerous research teams are interested in finding ways to enhance muscle regeneration, and below find the publicity materials for a couple of different lines of research along these lines - researchers in search of specific mechanisms that might be amenable to change, and thus the potential foundation for a drug discovery program and therapies in the clinic. Enhanced muscle regeneration encompasses more than just faster and more comprehensive recovery from injury, as much the same set of mechanisms are also involved in the normal maintenance and growth of muscles. As I'm sure the audience here is well aware, muscle tissue weakens and diminishes with age, a condition known as sarcopenia. Researchers hope that enhancements to the processes of muscle repair will be able to at least partially compensate for the losses of age, or delay those losses somewhat, even though they fail to directly address the underlying reasons for this form of age-related decline.

There is considerable debate over the causes of sarcopenia, and as for most aspects of aging, it is not yet possible to draw a consensus line of cause and effect from the sort of root cause forms of cellular damage outlined in the SENS rejuvenation research proposals all the way to well known age-related diseases, passing through the better explored metabolic changes observed in aging along the way. There is a great deal of data for sarcopenia, however: it is a puzzle in which at least some of the pieces are already joined together, even if it isn't quite settled as how these little islands of knowledge relate to one another in the bigger picture.

Changes in processing of amino acids appear important, as does the decline in diet and exercise in later life. Cellular senescence is implicated, as is becoming the case in many parts of the field now that more attention is being given to removal of senescent cells. Loss of mitochondrial function is also thought important, and there are related views involving loss of capillaries and nutrient supply in older tissue. Of late, there has been a fairly compelling argument to point to loss of stem cell activity as the primary lynchpin issue, though everything else just mentioned may well contribute to that loss. Everything is connected to everything else in cellular metabolism, and there are many angles from which the wise men can approach this elephant.

Inflammatory molecule essential to muscle regeneration in mice

Muscle stem cells usually nestle quietly along the muscle fibers. They spring into action when a muscle is damaged by trauma or overuse, dividing rapidly to generate enough muscle cells to repair the injury. But it's not entirely clear what signals present in inflammation activate the stem cells. Prostaglandin E2, or PGE2, is a metabolite produced by immune cells that infiltrate the muscle fiber as well by the muscle tissue itself in response to injury. Anti-inflammatory treatments have been shown to adversely affect muscle recovery, but because they affect many different pathways, it's been tough to identify who the real players are in muscle regeneration.

Researchers discovered a role for PGE2 in muscle repair by noting that its receptor was expressed at higher levels on stem cells shortly after injury. They found that muscle stem cells that had undergone injury displayed an increase in the expression of a gene encoding for a receptor called EP4, which binds to PGE2. Furthermore, they showed that the levels of PGE2 in the muscle tissue increased dramatically within a three-day period after injury, indicating it is a transient, naturally occurring immune modulator. "This transient pulse of PGE2 is a natural response to injury. When we tested the effect of a one-day exposure to PGE2 on muscle stem cells growing in culture, we saw a profound effect on the proliferation of the cells. One week after a single one-day exposure, the number of cells had increased sixfold compared with controls."

After seeing what happened in laboratory-grown cells, researchers tested the effect of a single injection of PGE2 into the legs of the mice after injury. "When we gave mice a single shot of PGE2 directly to the muscle, it robustly affected muscle regeneration and even increased strength. Conversely, if we inhibited the ability of the muscle stem cells to respond to naturally produced PGE2 by blocking the expression of EP4 or by giving them a single dose of a nonsteroidal anti-inflammatory drug to suppress PGE2 production, the acquisition of strength was impeded." The researchers next plan to test the effect of PGE2 on human muscle stem cells in the laboratory, and to study whether and how aging affects the stem cells' response. Because PGE2 is approved by the Food and Drug Administration for use in the induction of labor, a path to the clinic could be relatively speedy.

Researchers Find Key to Muscle Regeneration

Earlier this year, researchers published findings showing that a nuclear receptor called REV-ERB is involved in lowering LDL cholesterol. They previously studied REV-ERB's role in regulating mammals' internal clocks. Now the researchers are uncovering REV-ERB's role in muscle regeneration. Skeletal muscle comprises 40 to 50 percent of our total body mass and is essential for postural support, locomotion and breathing. With a high capacity for regeneration, skeletal muscle normally maintains muscle mass and function in response to minor injuries and normal wear and tear without much trouble. When injuries are severe - with more than 20 percent loss of muscle mass - normal muscle regeneration often cannot keep pace with the regenerative demands. In this scenario, the loss of skeletal muscle mass can trigger widespread fibrosis and loss of muscle function.

"Identifying new means of accelerating muscle regeneration has proved a daunting challenge. Therefore understanding the underlying mechanisms that regulate muscle cell regeneration and coordinate regenerative repair could provide future therapeutic options for stymieing the loss of muscle function in the traumatically injured." A simplified version of muscle cells' life-cycle looks like this: muscle stem cells produce myoblasts that will either reproduce (proliferate) or form muscle tissue (differentiate). Successful regeneration of skeletal muscle after traumatic injury depends on the replenishment of muscle fibers through elevated myoblast proliferation and differentiation.

The research team identified a mechanism through which REV-ERB may regulate gene expression pre and post muscle differentiation. "We demonstrate that REV-ERB can stimulate muscle regeneration upon acute muscle injury in an animal model. Our findings reveal that REV-ERB may be a potent therapeutic target for the treatment of a myriad of muscular disorders."

A Profile of Valter Longo's Work on Fasting and Calorie Restriction

Valter Longo is one of the more recognizable names in calorie restriction research. Beyond the science, his most noteworthy recent achievement has been to figure out how to commercialize the research, pulling in for-profit funding by packaging low-calorie diets as a medical product. This has helped to fund a series of advances in quantifying the effects of reduced calorie intake and fasting in humans, in search of the 80/20 point for optimal benefits, and along the way generating new knowledge of the effects on the immune system and other important areas of cellular metabolism. One of the most interesting outcomes is the accumulation of evidence to suggest that low-calorie diets can be about as effective as fasting in our species, at least in the near term.

As an aside, the tale of Longo's early work on the biochemistry of aging, provided in the article here, is illustrative of the degree to which the field was held back, both internally and by the rest of the research community. Aging research was a backwater, disrespected, lacking in funding. We could be ten to twenty years further ahead in treating aging as a medical condition than we are today, had the study of aging been taken as seriously as was the study of age-related diseases over the past fifty years. It is just one more example of the irrationality of the human condition that people are so enthused about research to treat heart disease, Alzheimer's disease, and so on, but reject outright work on the root causes of these conditions. The only way to cure age-related disease is to control the processes of aging - everything else is just putting thin patch over the problem and hoping. We should be thankful that this era of deliberate repression of aging research has largely come to an end, thanks to persistent and outspoken advocacy by those within and without the research community, and the field now has a chance to grow in funding and support.

He knows he sounds like a snake-oil salesman. It's not every day, after all, that a tenured professor at a prestigious university starts peddling a mail-order diet to melt away belly fat, rejuvenate worn-out cells, prevent diseases ranging from diabetes to cancer - and, for good measure, turn back the clock on aging. But biochemist Valter Longo is convinced that science is on his side. He now believes he's developed a diet that may boost longevity - by mimicking the effect of periodic fasting. His approach stands out because he insists he can use certain combinations of nutrients to trick the body into thinking it's fasting without actually being on a punishing, water-only diet.

Intrigued, we reviewed dozens of scientific studies and talked to a half-dozen aging and nutrition experts about fasting in general and Longo's diet in particular. Our conclusion? Fasting does appear to boost health - certainly in mice, and preliminary evidence suggests it might do so in humans as well, at least in the short term. It's not yet clear whether that's because abstaining from food prompts cellular changes that promote longevity, as some scientists believe - or because it simply puts a brake on the abundant and ceaseless stream of calories we consume to the detriment of our health. Either way, it can be a powerful force.

Mice and rats on fasting regimes are slimmer, live longer, and stay smarter and physically stronger as they age. They resist tumors, inflammatory diseases, and the neurodegeneration that characterizes diseases like Parkinson's and Alzheimer's. They handily fight off infection and can even sprout new neurons. They don't end up with diabetes, autoimmune disease, high cholesterol or fatty livers. Longo believes he knows why. Fasting, he and others argue, gives cells a break to rest, renew, rebuild themselves and, essentially, take out the trash as the body shifts from storing fat to burning it. They can't do that when the body is constantly ingesting food, stockpiling excess calories and pushing cells and organs to exhaustion.

Of course, many exciting findings that hold true for lab mice don't translate to more complex human biology. Small, short-term studies in humans do show that periodic fasting reduces weight, abdominal fat, cholesterol, and blood glucose, as well as proteins like C-reactive protein and IGF-1 that are linked to inflammatory diseases and cancer. But it's not clear how long these effects last or whether they translate into any lasting clinical advantage - such as fewer heart attacks or longer lifespan.

In the 1990s Longo was growing frustrated with attempts to study longevity in humans, and even mice, without having adequate tools to drill down into the genetic mechanisms underlying aging. He transferred to a genetics lab focused on yeast, figuring that would let him study the mechanisms of aging in the simplest of organisms. Few people took his early results seriously. Studying aging was still considered flaky. And many scientists at the time were deeply skeptical that you could learn much about human biology by studying simple yeast. "If someone said, 'What are you working on?' we would say oxidative chemistry. You couldn't say aging. That was viewed as a joke." Convinced his work was important, Longo kept his head down and kept going.

In just a year, Longo was able to work out a genetic pathway to describe aging in yeast and show that food - proteins and sugars - could speed aging. It was 1994. "I was so excited, I thought people were going to say, 'This is the discovery of the century.' Of course, it was sent back - rejected." He rewrote the paper and resubmitted. No luck. He couldn't get any of the work published without taking out every last reference to aging. As years passed, other groups started publishing work detailing, as Longo had, specific aging pathways, first in worms and eventually in flies. "The frustrating thing is that we had all of these things figured out and no one was listening."


Measurable Amyloid Buildup Occurs Significantly Before Alzheimer's Disease

Named and formally recognized age-related diseases are the late stages of processes of damage that start much earlier in life. So it is never a surprise to see that specific forms of damage strongly associated with any one specific age-related disease can be detected in smaller amounts earlier in old age, and that the people with more of that damage have a higher risk of later exhibiting the disease state. In the case of the research materials noted here, the disease is Alzheimer's, and the damage is accumulation of amyloid-β, a form of misfolded protein that accumulates in the brain. It and its surrounding halo of chemical interactions disrupt the correct function of brain cells, ultimately causing significant neurodegeneration.

The obvious solution here is to try to remove the amyloid, and in fact the Alzheimer's research community has and continues to spend considerable effort on this goal. It is one of the few areas where mainstream aging research aligns with the goals of the SENS rejuvenation research programs: identify the root cause damage that produces differences between old and young tissue, and repair it. Sadly, safe and effective clearance of amyloid has proven to be far more challenging than hoped. The field is littered with failed attempts, largely forms of immunotherapy, and only in the past couple of years have there been signs of success in human trials. Nonetheless, removing amyloid, and then expanding efforts to other forms of repair therapy, is the only game in town if the goal is to cure age-related neurodegenerative disease rather than just slow it down it little.

Older adults with elevated levels of brain-clogging plaques - but otherwise normal cognition - experience faster mental decline suggestive of Alzheimer's disease, according to a new study that looked at 10 years of data. Just about all researchers see amyloid plaques as a risk factor for Alzheimer's. However, this study presents the toxic, sticky protein as part of the disease - the earliest precursor before symptoms arise. Notably, the incubation period with elevated amyloid plaques - the asymptomatic stage - can last longer than the dementia stage. "To have the greatest impact on the disease, we need to intervene against amyloid, the basic molecular cause, as early as possible."

The researchers likened amyloid plaque in the brain to cholesterol in the blood. Both are warning signs with few outward manifestations until a catastrophic event occurs. Treating the symptoms can fend off the resulting malady - Alzheimer's or a heart attack - the effects of which may be irreversible and too late to treat. The researchers hope that removing amyloid at the preclinical stage will slow the onset of Alzheimer's or even stop it.

One in three people over 65 have elevated amyloid in the brain, and the study indicates that most people with elevated amyloid will progress to symptomatic Alzheimer's within 10 years. The study uses 10 years of data from the Alzheimer's Disease Neuroimaging Initiative, an exploration of the biomarkers that presage Alzheimer's. Although elevated amyloid is associated with subsequent cognitive decline, the study did not prove a causal relationship. Researchers measured amyloid levels in 445 cognitively normal people via cerebrospinal fluid taps or positron emission tomography (PET) scans: 242 had normal amyloid levels and 202 had elevated amyloid levels. Cognitive tests were performed on the participants, who had an average age of 74. Although the observation period lasted 10 years, each participant, on average, was observed for three years. The maximum follow-up was 10 years.

The elevated amyloid group was older and less educated. Additionally, a larger proportion of this group carried at least one copy of the ApoE4 gene, which increases the odds that someone will develop Alzheimer's. Based on global cognition scores, at the four-year mark, 32 percent of people with elevated amyloid had developed symptoms consistent with the early stage of Alzheimer's disease. In comparison, only 15 percent of participants with normal amyloid showed a substantial decline in cognition. Analyzing a smaller sample size at year 10, researchers noted that 88 percent of people with elevated amyloid were projected to show significant mental decline based on global cognitive tests. Comparatively, just 29 percent of people with normal amyloid showed cognitive decline.


Recent Research into the Details of Cellular Senescence

Today's papers are representative of present investigations that aim primarily to expand our knowledge of the details of cellular senescence. This is as opposed to efforts to immediately produce treatments that can address the impact of senescent cells on health. Senescent cells accumulate with age, and their presence is one of the root causes of degenerative aging. The most important work on cellular senescence at the moment is that aimed at selective destruction of these cells. The vast majority of cells that become senescent in our bodies, countless numbers day in and day out, are in fact already efficiently destroyed, either through programmed cell death or via the actions of the immune system. We'd all be much better off if the lingering remainder, the tiny fraction that evade this fate, were also removed.

That said, a sizable fraction of today's research into cellular senescence aims to better understand the processes involved, or to intervene so as to reduce the harms caused by these cells, or reduce the number of cells that become senescent, or even attempt to reverse senescence, rather than destroy these cells after the fact. I have to think that this isn't anywhere near as cost-effective a path forward when it comes to the development of practical therapies, in particular because destroying senescent cells effectively deals with the harms we don't understand in addition to those we do - and mapping cellular biochemistry is a slow and expensive process. There are long years ahead for those who want to fully understand how senescent cells cause harm at the detail level, and destruction solves the problem now. It is nonetheless the case that more information is better than less information in the long term, and expanded knowledge may well lead to new targets for the development of selective cell destruction therapies - a point illustrated in the first of the two papers below.

How is it that a comparatively small number of senescent cells are so harmful? In old age, senescent cells are perhaps a few percent by number of the cells present in any given tissue, yet their presence strongly shapes the functional decline of that tissue. The answer is that they produce a potent mix of signal molecules that cause chronic inflammation, degrade the normal regenerative and tissue maintenance activities of stem cells and immune cells, induce fibrosis and other disruptions of the extracellular matrix structure important for normal tissue function, and reduce tissue elasticity, among other issues. There is evidence for many other contributions to disease progression, from calcification of arteries to buildup of fatty deposits in blood vessels to failing lung function. Ridding our bodies of these cells would produce rapid benefits in later life, a point already well illustrated in a number of animal studies.

p21 maintains senescent cell viability under persistent DNA damage response by restraining JNK and caspase signaling

Senescent cells present elevated activity of senescence-associated beta-galactosidase (SA-β-gal) and a persistent DNA damage response that distinguish them from other non-proliferating cell populations. In addition, senescent cells produce a variety of characteristic secreted factors, collectively termed the senescence-associated secretory phenotype (SASP), which reinforces senescence arrest in an autocrine manner and mediates immune surveillance of the senescent cells. With aging, however, senescent cells accumulate in the organism promoting local inflammation that drives tissue aging, tissue destruction, and potentially also tumorigenesis and metastasis in a cell non-autonomous manner. Recent studies have shown that elimination of senescent cells promotes stem cell proliferation and prolongs lifespan. Therefore, mechanisms that regulate the viability of senescent cells in tissues evidently play an important role in tissue homeostasis.

The senescence program is driven by a complex interplay of signaling pathways. To promote and support cell cycle arrest, p16INK4A (CDKN2A), accompanied by the p53 (TP53) target p21 (CDKN1A), inhibits cyclin-dependent kinases (CDKs), thereby preventing phosphorylation of the retinoblastoma protein (pRb) and thus in turn suppressing the expression of proliferation-associated genes. In addition, the nuclear factor kappa B protein complex (NF-κB) acts as a master regulator of SASP and therefore affects both the microenvironment of senescent cells and their immune surveillance.

Whereas mechanisms driving senescence have been extensively studied, the mechanisms allowing their prolonged retention in tissues are much less well characterized. Recently, the anti-apoptotic BCL-2 family members BCL-W, BCL-XL, and BCL-2 were shown to facilitate the resistance of senescent cells to apoptosis. However, the contribution of pathways that regulate the formation of senescent cells to the resistance of these cells to cell death has yet to be determined. On one hand, senescent cells cannot accumulate p53 protein to the levels required for apoptosis. On the other hand, the p53 target p21, via its ability to promote cell cycle inhibition, can protect some cells from apoptosis.

This effect might be governed by both p53-dependent and -independent upregulation of the pro-apoptotic protein BAX, or by activation of members of the tumor necrosis factor (TNF)-α family of death receptors, or by effects on DNA repair. We therefore set out to determine how p21 regulates the viability of senescent cells after DNA damage. We found that following p21 knockdown, senescent cells sustain multiple DNA lesions, leading to further activation of DNA damage response and NF-κB pathways. This activation was regulated by both TNF-α secretion and JNK activation, and it mediated senescent cell death in a caspase-dependent and JNK-dependent manner. Moreover, p21 knockout in mice led to the elimination of senescent cells from fibrotic scars in the liver and alleviated liver fibrosis. These results uncovered new mechanisms that control the fate of senescent cells.

MicroRNA Regulation of Oxidative Stress-Induced Cellular Senescence

In the past years, microRNAs (miRNAs) turned out to be important players in controlling aging and cellular senescence by regulating gene expression. Of note, a global decrease in miRNAs abundance was found in aging of different model organisms, suggesting aging-associated alteration of miRNAs biogenesis. In fact, aging-induced dysregulation of miRNAs biogenesis proteins is reported to promote aging and aging-associated pathologies. Among them, ribonuclease Dicer is most studied and a reduced level was reported in tissues of aged mice and rats, as well as in senescent cells.

Although the mechanisms of miRNA biogenesis have been intensively investigated in recent years, processes regulating miRNA stability remain to be explored. miRNAs have been generally considered as stable molecules with half-life of days long, while some miRNAs are actually short lived with half-life of no more than few hours. It is now clear that the absolute levels of mature miRNAs are also controlled by factors that directly affect stability. Whether miRNA stability changes during cellular senescence is so far, to our knowledge, not known. Further researches on miRNA stability and degradation mechanisms in cellular senescence and aging are needed to identify its impact on age-associated process and may provide potential new targets to interfere the process.

A number of miRNAs have been found to be differentially expressed in senescent cells or aged tissues and play a role in cellular senescence. Recently, miRNAs have been found extracellularly and function in intercellular communication upon taken up by recipient cells. The fact that circulating miRNAs are packed in the form of microvesicles protects them from degradation. The stability of miRNAs in the circulation and in body fluids, their tissue and disease specificity, and the easy and reliable quantification methods make them feasible as potential biomarkers. Several miRNAs detected in blood samples have been found in several studies to be associated with human aging. Further efforts are needed to identify consensus miRNA biomarkers not only as indicators of aging process and aging-associated disease but also as longevity predictors and eventually therapeutic approaches to modulate the aging process.

Although a relatively new field of research, miRNAs add substantial complexity to the regulation of aging processes and cellular senescence. On one side, a single miRNA can regulate the expression of hundreds of genes from different signaling pathways, which means the whole signaling network could be reset by modulating the expression of one single miRNA. In contrast, miRNAs as players of adaptive stress response could act both as promoters and inhibitors of senescence, depending on the type of stress, the cell or tissue where they are located, and the molecular context in which they play a role. Further efforts are needed to explore the modulatory role of miRNAs in cellular senescence.

An Update on the Effects on PAPP-A Knockout on Longevity in Mice

Deletion of pregnancy-associated plasma protein-A (PAPP-A) is one of a number of genetic alterations that have been used to produced lineages of long-lived mice. For researchers interested in translating this sort of discovery into treatments that might modestly slow human aging, an important question is whether the mice live longer because this alteration was present throughout development and childhood, or whether the effects on life span are determined over the course of adult life. Only in the latter case would researchers be able to proceed with any confidence to work on the basis for a human treatment. To further investigate the basis for enhanced longevity in mice lacking PAPP-A, researchers have now used a form of gene therapy to delete PAPP-A in adult mice, an approach we should expect to see applied in the years ahead to all of the genetic approaches that extend life in mice. Here, they report on the results.

To date, the only known function of pregnancy-associated plasma protein-A (PAPP-A) is to enhance local insulin-like growth factor (IGF) availability for receptor activation through cleavage of inhibitory IGF binding proteins. As reduced IGF signaling has been shown to increase life span in a wide variety of species, we postulated that loss of PAPP-A would suppress IGF receptor signaling and extend life span. This was proven true in that both male and female PAPP-A knockout (KO) mice lived significantly longer than their wild-type littermates. The PAPP-A KO mice were also resistant to the development of several age-related diseases, such as atherosclerosis.

However, these mice were generated through homologous recombination in embryonic stem cells. To distinguish the impact of PAPP-A deficiency in the adult from that during fetal and early postnatal development, we developed a mouse model suitable for tamoxifen (Tam)-inducible, Cre recombinase-mediated excision of the PAPP-A gene. In an atherosclerosis-prone mouse model, Tam administration in adult mice inhibited established atherosclerotic plaque progression by 70%. In this study, we sought to answer the question of whether conditional reduction of PAPP-A gene expression in adult mice would result in extended life span.

Female mice homozygous for floxed PAPP-A (fPAPP-A) and either positive (pos) or negative (neg) for Tam-Cre were used in the life span study. fPAPP-A/neg and fPAPP-A/pos mice had similar weights at the start of the experiment and showed equivalent weight gain up to 17 months of age. We found that fPAPP-A/pos mice had a significant extension of life span. The median life span was increased by 21% for fPAPP-A/pos compared to fPAPP-A/neg mice. Mortality in life span quartiles indicates that the proportion of deaths of fPAPP-A/pos mice were lower than fPAPP-A/neg mice at young adult ages and higher than fPAPP-A/neg mice at older ages. This study is the first to show that downregulation of PAPP-A expression in adult mice can significantly extend life span.

Importantly, this beneficial longevity phenotype is distinct from the dwarfism of long-lived PAPP-A KO, Ames dwarf, Snell dwarf and growth hormone receptor (GHR) KO mice with germ-line mutations. Thus, downregulation of PAPP-A expression joins other treatment regimens, such as resveratrol, rapamycin and dietary restriction, which can extend life span when started in mice as adults. In a recent study, inducible knockdown of the GHR in young adult female mice increased maximal, but not median, life span. Tissue-specific PAPP-A KO models would provide insight into the tissues and organs that contribute to extended life span and healthspan.


Another Potential Approach to the Creation of Tissue Engineered Cartilage

Cartilage is a comparatively simple, homogeneous tissue, and the medical community has a great deal of experience in treating cartilage injuries, so it is an obvious place to start for tissue engineers. Creating cartilage that has the correct load-bearing characteristics has proven to be a challenge, however: you can't just put cartilage cells into a bioreactor on their own and expect to obtain anything other than a sloppy gel at the end of the day. Fortunately, a number of groups have made progress in recent years on this front, finding approaches to convince the cells involved to generate the suitably structured extracellular matrix needed to form a solid, high-strength tissue. The method described here is one of the more straightforward ones:

Biomedical engineers have created a lab-grown tissue similar to natural cartilage by giving it a bit of a stretch. The tissue, grown under tension but without a supporting scaffold, shows similar mechanical and biochemical properties to natural cartilage. Articular cartilage provides a smooth surface for our joints to move, but it can be damaged by trauma, disease or overuse. Once damaged, it does not regrow and is difficult to replace. Artificial cartilage that could be implanted into damaged joints would have great potential to help people regain mobility.

Natural cartilage is formed by cells called chondrocytes that stick together and produce a matrix of proteins and other molecules that solidifies into cartilage. Bioengineers have tried to create cartilage, and other materials, in the lab by growing cells on artificial scaffolds. More recently, they have turned to "scaffold-free" systems that better represent natural conditions. The research team grew human chondrocytes in a scaffold-free system, allowing the cells to self-assemble and stick together inside a specially designed device. Once the cells had assembled, they were put under tension - mildly stretched - over several days. They showed similar results using bovine cells as well. "As they were stretched, they became stiffer. We think of cartilage as being strong in compression, but putting it under tension has dramatic effects."

The new material had a similar composition and mechanical properties to natural cartilage, the researchers found. It contains a mix of glycoproteins and collagen, with crosslinks between collagen strands giving strength to the material. Experiments with mice show that the lab-grown material can survive in a physiological environment. The next step is to put the lab-grown cartilage into a load-bearing joint, to see if it remains durable under stress. "The artificial cartilage that we engineer is fully biological with a structure akin to real cartilage. Most importantly, we believe that we have solved the complex problem of making tissues in the laboratory that are strong and stiff enough to take the extremely high loads encountered in joints such as the knee and hip."


I'm Not Dead Yet as a Path to Calorie Restriction Mimetics

INDY, I'm Not Dead Yet, is one of the earliest of longevity-associated genes to be documented. Researchers uncovered its effects in flies at the turn of the century, something like half an eternity ago given the pace of modern biotechnology. Despite the rapid pace of progress in the field as a whole, the INDY gene is also an example of the extremely slow and incremental progression that is characteristic of any one specific line of research in molecular biochemistry. The open access paper I'll point out today is a review of what is presently known of INDY in flies and mammals, information gathered over the what is now going on for two decades of work. The focus is on the ways in which the beneficial effects of reduced levels of INDY appear quite similar to those of calorie restriction - though clearly it is a complicated overlap, because trying both reduced levels of INDY and calorie restriction either has no effect or shortens life span. Regardless, anything that looks a lot like calorie restriction tends to be treated as a potential road to the development of calorie restriction mimetic drugs in this day and age.

Why is progress slow when you follow any one particular thread in aging research? Well, for one funding for aging research is small in comparison to other fields of medical research. Secondly, cellular biochemistry is enormously complex. It does in fact tend to take a few years even now for any one group to make a single connection in the complex web that is cellular metabolism. Just moving the focus of research into INDY from flies to mice took a long time, and it is still clearly in its early stages when considered in the context of the bigger picture of identifying targets, developing drugs, and producing clinical treatments. Mapping and tinkering with metabolism is a good thing in the long term, as gaining a full understanding of our cells is - and should be - the goal of the life sciences, but it certainly isn't the fast road to meaningful interventions to slow or reverse the aging process. For that we need engineering approaches like SENS, turning what we already know of aging into repair treatments capable in principle of rejuvenation.

INDY - A New Link to Metabolic Regulation in Animals and Humans

The Indy (I'm Not Dead Yet) gene encodes the fly homolog of the mammalian SLC13A5 transporter of the tricarboxylic acid (TCA) cycle intermediates. Reduced expression of the Indy gene in flies and worms extends longevity in all but one study. INDY is expressed on the plasma membrane of metabolically active tissues. In flies INDY is predominantly expressed in the midgut, fat body, and oenocytes (fly liver). In humans, Indy mRNA is mainly expressed in the liver, less in the brain and testis, while small levels of Indy mRNA expression were found in the kidneys, thymus, ovaries, adipose tissue, stomach, and colon.

Decreased expression of Indy in worms, flies, mice, and rats alters metabolism in a manner similar to calorie restriction (CR). This is supported by similar phenotypes found in CR wild type flies and in Indy flies that were kept on a high calorie diet. These Indy flies have lower lipid levels, increased mitochondrial biogenesis, increased spontaneous physical activity and a reduction in components of the insulin-signaling pathway activity. Furthermore, Indy heterozygous flies laid more eggs during their life compared to controls. However, under CR condition, Indy heterozygous flies have reduced fecundity due to lower energy resource caused by the effect of reduced Indy on metabolism. Consistently, CR does not further extend longevity of long-lived Indy heterozygous flies and shortens longevity of Indy homozygous flies.

Preservation of intestinal stem cell (ISC) homeostasis has a key role in maintaining normal midgut function and contributes to extended health and longevity in flies. Changes in mitochondrial biogenesis found in the midgut of Indy flies, combined with increased antioxidant activity and reduced production of reactive oxygen species preserve ISC homeostasis and intestinal integrity in Indy flies. These changes maintain midgut function and mediate extended health and longevity of Indy flies.

Reduced activity of the Indy homologs in other organisms is associated with similar metabolic effects that mimic CR. siRNA mediated knockdown of Indy/CeNac2, the worm Indy homolog, results in worms that are smaller, have reduced lipid levels, and have extended longevity. Mammalian Indy (mIndy)-/- knockout mice are protected from the negative effects of aging or a high-fat diet on metabolism, which include hepatic fat accumulation, obesity, and insulin insensitivity. These mice have increased energy expenditure, reduced hepatic lipogenesis, increased mitochondrial biogenesis, and enhanced hepatic fatty acid (FA) oxidation. Whole-genome microarray studies comparing mIndy-/- and mIndy-/+ revealed that transcriptional changes found in the liver of mIndy-/- mice are 80% identical to changes found in the liver of CR mice. All of these findings confer that INDY reduction creates a state similar to CR.

In summary, reduction of Indy gene activity in flies and worms extends their health and longevity. Genetically reduced INDY expression has beneficial effects on metabolism and prevents diet-induced obesity in flies and mice, suggesting INDY as a target in the treatment of metabolic disorders in humans. By contrast, high levels of INDY are associated with negative effects on metabolism and health. Recently, increased hepatic levels of mINDY were linked to insulin resistance in obese humans. These findings illustrate both the relevance of the mIndy gene to human health and a highly conserved role for INDY in the metabolism of a broad range of species. Thus, mIndy has emerged as a novel target for the treatment of age- and diet-associated metabolic syndrome. The further development of mIndy inhibitors may additionally provide effective interventions targeting the debilitating health effects that are often associated with aging and will thereby allow a healthier life.

Ghrelin Knockout Mice Eat Less But Fail to Live Longer as a Result

One of the many interesting but unresolved questions relating to calorie restriction and its beneficial effects on health and longevity is the role played by ghrelin. This hormone regulates appetite, but also has a range of other effects on metabolism. For example, it appears to be involved in immune function and inflammation. This sort of observation raises the question of the degree to which the full physiological experience of hunger is a necessary part of the benefits produced by calorie restriction. Researchers here take a first step in the exploration of this topic with a study of mice genetically engineered to lack ghrelin. The interesting portion of the data is that mice without ghrelin eat less, at least while young, but did not live longer, as is reliably the case in normal mice with a reduced calorie intake. I think that the authors head off in the wrong direction with a focus on AMPK, rather than exploring calorie restriction as an explanation for much of what they observed. There is no real discussion of why it might be that life span was not increased in ghrelin knockout mice, which seems to me the real question here.

In line with what is seen in humans during aging, here we show that old wild-type (WT) mice show an increase in body weight and fat mass, along with a significant decrease in muscle strength and endurance. Although ghrelin deletion (KO) in young animals on regular diet was previously shown not to have a significant effect on food intake, energy expenditure, or body weight, we show for the first time that ghrelin deletion significantly prevented body weight and fat mass gain in older mice while maintaining lean mass and muscle function when compared to wild-type age-matched animals.

As body weight gain develops as a result of energy imbalance, food intake and energy expenditure were studied in detail. Aging was associated with a decline in food intake, but also in spontaneous locomotor activity and total energy expenditure. Ghrelin deletion decreased food intake in young animals and partially prevented the decrease in energy expenditure seen with aging in WT mice. Given that the decrease in locomotor activity seen with aging was similar in WT and KO mice, we postulate that the difference in total energy expenditure between genotypes was primarily due to changes in resting energy expenditure. The data also suggest that a decrease in energy expenditure due to decrease locomotor activity and, perhaps also in resting energy expenditure, is the main variable driving the energy imbalance during aging in mice.

We found no differences in muscle mass or whole body lean mass between genotypes. Nevertheless, the decline in endurance and grip strength seen with aging in WT mice was also partially prevented by ghrelin deletion. In this study, we also show a significant increase in type IIa (fatigue resistant, more oxidative) fiber content with aging in KO compared to WT mice that is likely to be responsible for the increased endurance seen in KO aged animals. We postulate that this increase in type IIa, fatigue-resistant, oxidative fibers could have contributed to the increased energy expenditure and subsequently decreased fat mass seen in aged KO mice as skeletal muscle fibers are major contributors to resting energy expenditure.

At the molecular level, the age-related decreases in endurance and muscle strength were associated with downregulation of phospho-AMPK and its downstream mediators. These changes were partially prevented by ghrelin deletion. Previous studies have shown the importance of the AMPK pathway on improving endurance, and this finding suggests that AMPK modulation by ghrelin could contribute to the phenotype seen in our model of increased endurance and muscle strength. The interplay between ghrelin and AMPK is not well-understood, however. There are no previous reports of chronic effects of ghrelin or ghrelin blockade on AMPK activation; however, it is known that AMPK target genes are key to mitochondrial biogenesis, fatty acid oxidation, and energy expenditure. Taken together, the data are consistent with the hypothesis that AMPK modulation by ghrelin may contribute to ghrelin's effects on muscle function, fat accumulation, and energy expenditure.


Regeneration of Structured, Full-Thickness Skin, Including Hair Follicles

The tissue engineering company PolarityTE is claiming regrowth of correctly structured skin in pigs, incorporating hair follicles and various glands. The press release and company website are light on some of the more interesting details, such as just how close to natural skin the end result is in this case, but we shouldn't have to wait too long to find out more. Clinical trials are starting this year.

PolarityTE, Inc. today announced pre-clinical results demonstrating that the Company's lead product, SkinTE, regenerated full-thickness, organized skin and hair follicles in third degree burn wounds. The findings represent the first known successful regeneration of skin and hair in full-thickness swine wound models, the standard animal model for human skin. The Company expects to initiate a human clinical trial evaluating the autologous homologous SkinTE construct in the third quarter of 2017. In pre-clinical models of full-thickness burns and wounds, SkinTE demonstrated scar-less healing, hair follicle growth, immediate complete wound coverage, and the progressive regeneration of all skin layers including epidermis, dermis and hypodermal layers.

"These findings using SkinTE demonstrate an entirely new and pragmatic system whereby Polarity has used autologous tissue to regenerate full-thickness skin, hair follicles and appendages for the treatment of burns and wounds. Our revolutionary approach to a new form of regenerative healing offers hope to both burn and wound patients, as well as medical providers who have not seen a significant advance in skin regeneration since the 1980s." Swine models of burns and wounds are known to be predictive of results found in humans due to the unique similarities between swine and human skin. Of note, it is believed that swine skin may be more difficult to regenerate with all layers and appendages (hair and glands), as was done in the studies by PolarityTE, suggesting that the results of these studies may predict similar efficacy in human patients when clinical trials begin later this year.


Advocacy for the Importance of Mitochondrial Function in Aging

The open access paper I'll point out today should be taken as an opinion piece rather than something more rigorous, I think. The authors link together a few findings from past years in order to make an argument about some of the specifics of mitochondrial function and its importance in aging. It is interesting, albeit a touch overwritten, when considered in the bigger picture. It is certainly the consensus in the scientific community that mitochondria are important in aging, a consensus based on many lines of research and a large amount of evidence accumulated over decades. Atop that consensus, however, there is still considerable room to debate the precise details and mechanisms involved in the influence of mitochondria upon aging. I suspect that this will continue to be the case until someone builds a working rejuvenation therapy based on one or another mitochondrial theory of aging. Biology is complex enough that at the present stage of technological development it is easier to prove a point through intervention than through investigation.

Mitochondria are the power plants of the cell, though they also have many other duties; nothing is ever simple in cellular biochemistry. They evolved from symbiotic bacteria, a replicating herd of them in every cell, and their primary task is to generate chemical energy store molecules to power cellular operations. This makes their correct function especially important in more energy-hungry tissues such as the brain, and thus declines in mitochondrial function frequently appear as a topic in research into most neurodegenerative conditions. Declines in mitochondrial activity across the board may be due to regulatory reactions to rising levels of cell and tissue damage, but the full picture of this process is still hazy with regards to how the known pieces of the puzzle fit together. Beyond this, there is the view of mitochondrial damage in which certain rarely occurring forms of dysfunction can produce mitochondria that take over their host cell and make it malfunction in ways that promote aging, exporting a flood of reactive molecules into surrounding tissues.

Researchers can also compare mitochondrial biochemistry between species with different life spans, and have found strong correlations between life span and mitochondrial activity and structure. Species in which mitochondria have a more resilient composition, made up of molecules more resistant to oxidative damage, tend to live longer. There is even a fair amount of evidence to suggest that differences in mitochondrial function are important in natural variations in longevity between individuals of the same species. Thus there is a great deal of evidence that, when considered as a whole, should encourage greater efforts to repair mitochondrial function in the old, to reverse observed declines, to fix damaged mitochondria. There is every reason to think that this might be one of the forms of therapy needed to produce rejuvenation.

Aging Reversal and Healthy Longevity is in Reach: Dependence on Mitochondrial DNA Heteroplasmy as a Key Molecular Target

A wealth of biomedical data supports a key role of impaired mitochondrial bioenergetics functionally linked to marked dysregulation of diverse cellular processes as a unifying causative factor in the etiology and persistence of major pathological conditions afflicting human populations. It appears that the contextual bases of normal aging, genetically determined lifespan, and mortality are intrinsically linked to the total number of tissue- and organ-specific multicellular complexes competing for relatively limited energy sources during temporal stages of growth and development. It follows that the stereotypically defined lifespans of diverse species of higher animals reflect the existential "price" to pay for the exquisite cellular diversity required for integrated regulation of complex organ function. Variations in longevity within individual members across species of higher animals may then be effectively sorted according to age-dependent losses of single-cell metabolic integrity functionally linked to impaired mitochondrial bioenergetics within compromised complex organ systems.

Recent studies have focused on the functional role of mitochondrial heteroplasmy, defined as a dynamically determined co-expression of wild-type (WT)-inherited polymorphisms and somatic mutations in varying ratios within individual mitochondrial DNA (mtDNA) genomes. Based on the empirically determined number of mitochondria with differing mtDNA copy numbers distributed in tissue-specific cell types, the total concentration of mtDNA molecules exceeds the number of nuclear DNA molecules by two to five orders of magnitude. It is also apparent that high levels of heteroplasmic mtDNA genomes within the intra-mitochondrial compartment in individual human cell types is required for normative mitochondrial bioenergetics that is markedly compromised in human disease states.

A potential window of opportunity for practical achievement of aging reversal and extended longevity in human populations is alluded to in a study that has highlighted the importance of functional mitochondria in the maintenance of differentiation and reprogramming of induced pluripotent stem cells (iPSCs). A transition from somatic mitochondrial oxidative metabolism to glycolytic metabolism, highly reminiscent of cancer cells, was observed to be required for successful reprogramming of iPSCs. Importantly, somatic mitochondria and associated oxidative bioenergetics were extensively remodeled with the induction of an iPSC-like phenotype. Preservation of tissue-selective patterns of mtDNA heteroplasmy within a viable reserve of iPSCs would appear to represent a key molecular target for practical augmentation of anti-aging therapies and lifespan extension.

State-dependent transfer of functional mitochondria from healthy to metabolically compromised cell types has been extensively documented. Interestingly, within developing and/or reparative cellular systems, intercellular trafficking of optimally functional mitochondria is achieved using tunneling nanotubes or cellular derived vesicles in an elaborate transfer system. Thus, technological transplantation of functionally viable mitochondria comes with the anticipation of the significant restoration of normative cellular function functionally linked to the preservation of cell-specific mosaic patterns of heteroplasmic mtDNA expression. From a translational perspective, restoration of genetically determined patterns of mitochondrial heteroplasmy has the potential to restore and maintain mitochondrial dynamics in multiple organ systems. Long-term restoration and preservation of tissue- and organ-specific patterns of mitochondrial heteroplasmy and mtDNA copy number represent practical goals for bioengineering strategies designed to overcome age-related limitations in meeting physiological energy demands.

Cell-specific patterning of mtDNA heteroplasmy encompassing thousands of mitochondrial genomes within a single cell may be viewed as a reservoir required to effect minute changes in energy requirements critically linked to physiological demands. Normative cellular expression of mtDNA heteroplasmy may effectively represent a sophisticated molecular coping strategy with critical biological importance to cellular/organismic survival and health, and mechanistic relevance to lifespan extension and longevity. Within this context, chronic dysregulation of mitochondrial function leading to the initiation and persistence of diverse pathophysiological states may be attributed to a temporal loss of ongoing restorative processes that appear to be inherently dependent on normal mitochondrial heteroplasmy. We surmise that the extent of short- and long-term cellular and mitochondrial damage may be effectively ameliorated by the selective targeting and reversal of debilitating somatic mutations in mtDNA. Restoration of relatively slow, age-related, perturbations of normative mitochondrial heteroplasmy is then proposed to promote enhanced quality of life via prolonged maintenance of essential cellular signaling pathways that have been widely associated with age-related metabolic rundown.

The Classification and Screening of Geroprotector Drug Candidates

One faction in the aging research community defines drugs that modestly slow aging as "geroprotectors," and maintains an online database of studies and results for such drug candidates. These drug candidates generally work through alterations to metabolism that either slow the pace of accumulated cell and tissue damage, or make older individuals modestly more resistant to the consequences of that damage. These are all marginal effects - don't look for rejuvenation and radical life extension in this part of the field. That can only occur through comprehensive repair of the molecular damage that causes aging. Geroprotectors are perhaps best represented at this time by calorie restriction mimetics, replicating some fraction of the beneficial response to a lower calorie intake, and by compounds that boost autophagy, increasing cellular repair and maintenance.

Aging causes disease progress and a gradual decline in physical and mental function. Because of the rapid aging of the population, the risk of economic collapse in developed countries is increasing. Therefore, anti-aging and disease prevention has become a high priority science challenge. Although geroprotector discovery is a popular biomedical trend and more than 200 compounds can slow aging and increase the lifespan of animal models, there are still no geroprotectors on the market. The reasons may be related to the lack of a unified concept of aging mechanisms, the problem of translation of geroprotectors studies results from model organisms to humans, low level of interest from big pharma since aging has no status as a disease.

But one of the main obstacles, in our opinion, is the lack of a concept of geroprotector accepted by the scientific community. Such concept as a system of criteria for geroprotector identification and classification can form the basis for an analytical model of geroprotectors, help consolidate the efforts of various research initiatives in this area and compare their results. This model can serve as a platform for formulating and solving a variety of tasks, from a selection of the most promising and efficient existing candidate geroprotectors to possible constructing of a model geroprotector that can be searched in the libraries of compounds or synthesized purposefully.

The most significant main rule for geroprotectors is evidently the ability to increase lifespan. Candidate geroprotectors should ameliorate molecular, cellular, and physiological biomarkers to a younger state or slow the progression of age-related change in these markers. The therapeutic lifespan extending dose of a geroprotector should be several orders of magnitude less than the toxic dose. Potential geroprotectors should improve health-related quality of life: physical, mental, emotional, and social functioning of the treated person. The target or mechanism of action of the geroprotector should be evolutionarily conserved. Reproducibility of geroprotective effects on different model organisms increases the possibility of effects will also be discovered in humans, even in the absence of a known conserved target. Candidate geroprotectors should be able to delay the progress of one or several age-associated disorders. Potential geroprotectors should increase the organism's resistance to unfavorable environmental factors.

The compliance of a substance with at least the majority of these criteria allows the claim that we are dealing with a candidate geroprotector. With the help of modern mathematical tools for data analysis and decision-making, such a system would facilitate formulating and solving a number of important scientific and applied problems, the most significant of which is the selection of geroprotectors with the largest and most reliable effect on life expectancy.


A Report from the 2nd Scripps Symposium on the Biology of Aging

This open access paper reports on the proceedings at the 2nd Scripps Symposium on the Biology of Aging held earlier this year. Like much of the field now, the focus in unabashedly on intervening in the aging process, which is good to see. Also like much of the field there is still considerable reluctance to talk in public about the potential for rejuvenation and radical life extension, however, rather than aiming at more modest gains. Still, the core message that we should treat aging as a medical condition has now spread far beyond the small groups that started this advocacy. One of the seven SENS rejuvenation research programs needed to reverse aging, senescent cell clearance, has been adopted enthusiastically by the scientific mainstream. These are important and necessary advances on the way towards a future of longer, healthier lives for all.

The goal of the symposium was to bring together leaders in the fields of aging and drug development to discuss strategies for identifying and developing therapeutic approaches to extend human healthspan. This symposium made it highly evident that the biology of aging field is moving quickly toward translational research. At the symposium, there were numerous reports of successful drug screens and drug testing in a variety of model systems. There was also an overall sense of excitement, given that multiple therapeutic modalities, including young plasma, recombinant proteins, and small molecules, extend healthspan and lifespan in model organisms and that clinical trials to test the efficacy of these treatment modalities on healthspan and resilience have been initiated.

The concept of geroscience, defined as the understanding of the relationship between aging and age-related diseases and preventing/delaying disease by targeting fundamental mechanisms of aging, was an underlying theme of the symposium. As reiterated by the keynote speakers, aging is the main risk factor for most chronic diseases. Thus, developing approaches to therapeutically target aging should be a funding priority for the majority of institutes at the National Institutes of Health, as well as other funding agencies, philanthropists, and foundations. The socioeconomic need to extend human healthspan also was made clear. As a consequence of the advances in prevention and treatment of infectious diseases, there will be an unprecedented increase in the number of persons over 65 over the next decades. By 2035, the cost of treating Americans 65 years and older is expected to be over $2 trillion annually. Thus, finding ways to prevent all age-related diseases is one of the most imperative biomedical pursuits.

A common theme arising from the symposium was the need for appropriate model organisms to study aging and age-related disease including models carrying reporters of senescence, mitochondrial function, autophagy and reactive oxygen species (ROS). The use of these reporters or testing of therapeutics needs to be performed in aged model organisms, a problem that has also plagued the cancer field because of the cost and time involved, at least in rodent models. Here, the National Institute on Aging (NIA) Interventions Testing Program in mice (ITP) and in Caenorhabditis elegans (C. elegans) (CITP) have made significant contributions to the identification of drugs/compounds able to extend lifespan. Despite the ITP, CITP, and new models of aging, there still is a need for an expansion of efforts to measure the effects of drugs/compounds on healthspan or resilience, which has greater translational relevance. Thus, many investigators are beginning to incorporate functional analysis of aged mice undergoing therapeutic interventions.

An emerging paradigm in the field of aging is that the burden of senescent cells increases with age in multiple tissues and reducing this senescent cell burden improves healthspan. The reduction of senescent cells in mice reduced atherosclerosis, improved metabolism, prevented tumor metastasis and reduced osteoarthritis in an injury model. Thus, the hunt is on for senolytics or drugs that specifically kill senescent cells. Whether optimized senolytics will have similar positive effects on human healthspan is still unclear, but clinical trials are being planned to determine their effectiveness. It is important to note that it is likely that no one senolytic will be effective in eliminating all types of senescent cells. Individual senolytic compounds are apt to have tissue-specific and even cell type-specific effects. Furthermore, there is increasing evidence that different drivers of senescence can lead to differences in how senescence manifests, which in turn could have a variable impact on the senescent cell's environment.

Adult stem cell function is known to decline with aging. However, it has taken longer to demonstrate that the loss of stem cell function contributes to aging and is not simply a consequence of it. Treatment of a mouse model of accelerated aging with two types of young stem cells extends healthspan and lifespan. Although the exact mechanism for how these stem cell populations affect aging is unknown, preliminary data suggest that their effect is mediated by factors secreted by young, but not old stem cells. These factors appear to reduce cellular senescence and improve the function of endogenous, aged stem cells. Whether these stem cell-derived soluble factors are the same as those found in young plasma is currently unknown. This will undoubtedly remain an area of intense research spanning from continued investigations into fundamental mechanisms of aging to clinical trials.

Clear evidence that the field of aging is moving forward quickly is the number of ongoing or soon-to-be-initiated clinical trials. Importantly, the use of specific short-term clinical endpoints to determine if resilience or function of a specific tissue could be improved is employed to reduce study size, duration, and cost. For example, short-term treatment of a cohort of elderly people with a rapamycin analogue (rapalog) was tested for its ability to improve immune function. The inclusion of additional endpoints provides further information about not only the effect of the intervention on immune function, but also on other aspects of aging that might be modulated and measured in future clinical trials. Similarly, short-term clinical trials with the mitochondrial-targeted SS-31 peptide are in progress for heart disease based on very promising preclinical data. These short-term treatment trials with well-defined, disease-specific endpoints are in contrast to the highly anticipated Treating Aging with Metformin (TAME) trial. The TAME trial is designed to enable evaluating whether metformin extends the healthspan of humans albeit in a rapid 3-5 year format. It is hoped that the TAME trial will serve as a template for pharmaceutical companies to do future testing of drugs aimed at targeting fundamental mechanisms of aging.

It also is clear that support from the private sector will be essential for moving clinical trials forward as there is a huge need for funding from sources other than the NIH to expedite aging research. The successful completion of the first clinical trial demonstrating that human healthspan can be extended is anticipated to instigate tremendous interest in the field by biotech investors and potentially philanthropists. Thus, this first proof-of-principle clinical trial and funding support for it is considered a significant hurdle that must be crossed to accelerate funding and progress in the field.


On the Ethics of Extending Healthy Longevity

If you survey our community, asking in detail about moral and ethical views on medical approaches to extending the healthy human life span, and follow up with opinions on exactly which biotechnologies should be pursued for the greatest benefit, then I suspect that you would be hard pressed to find any two people with exactly the same collection of opinions. There is a great deal of variation, even among those who primarily give their support to SENS rejuvenation research. When it comes to the technology and the prioritization, everyone has their own private SENS variant; a little added here, a little removed there. The same is true of the ethical view regarding exactly why it is that we should enable the choice of living longer for as many people as possible, as soon as possible.

For my part, I'm more or less a utilitarian, minus the part wherein one should be willing to sacrifice N to enable N+1. Ends do not blindly justify means. My utility function tends towards assigning value to time spent alive, to freedom and breadth of choice, and the absence of suffering. I think that a greater number of sentient entities, more capable sentient entities, and less suffering are all good things. The motivation really doesn't have to be any more complex than this. The most sensible approach for any individual who desires to help keep the trend of development moving in that direction is to attack the greatest causes of death, limitation, and pain in descending order. Aging is right up there at the top of the list: the greatest cause of death by far, the greatest limitation on the human condition at the present time precisely because it kills most people, and the greatest cause of suffering. We should do something about that.

Frequently Asked Questions on the Ethics of Lifespan and Healthspan Extension

The mission of healthy life extension, or healthy longevity promotion, raises a broad variety of questions and tasks, relating to science and technology, individual and communal ethics, and public policy, especially health and science policy. Despite the wide variety, the related questions may be classified into three groups. The first group of questions concerns the feasibility of the accomplishment of life extension. Is it theoretically and technologically possible? What are our grounds for optimism? What are the means to ensure that the life extension will be healthy life extension?

The second group concerns the desirability of the accomplishment of life extension for the individual and the society, provided it will become some day possible through scientific intervention. How will then life extension affect the perception of personhood? How will it affect the availability of resources for the population?

The third and final group can be termed normative. What actions should we take? Assuming that life extension is scientifically possible and socially desirable, and that its implications are either demonstrably positive or, in case of a negative forecast, they are amenable - what practical implications should these determinations have for public policy, in particular health policy and research policy, in a democratic society? Should we pursue the goal of life extension? If yes, then how? How can we make it an individual and social priority?

Quite surprisingly (at least for the proponents of healthy longevity), for decades and centuries, there has been expressed strong opposition to the very idea of life extension. The opposition has been frequent among philosophers, and even among physicians and researchers of aging. There has been a strong tendency among well-established physicians and scholars to consider aging as inexorable and therefore "normal," and to see the lifespan as fixed and immutable. Accordingly, any attempts to "meddle" with the aging process or to significantly extend longevity would be considered foolish, futile and even somehow unethical.

The apparent weight of authority of the critics and skeptics, and the wide popularity of the skeptical views, may emphasize the question: "Is increasing longevity, especially healthy longevity, really desirable, for the individual or the society?" The answer that may be given by the proponents of life extension is very simple: "Yes. People want to live longer and to live healthier." Or to put it even more bluntly, "it is better to be healthy, wealthy, wise and long-lived, than otherwise." And that may conclude the discussion. Yet, some explanations and arguments are still required. Usually, the arguments against extending longevity are standard and are refutable in standard ways. The questions and answers below may provide a short summary of such debates.

Would extending longevity enhance human suffering, or conversely, is death a solution against suffering? No. Death is not a solution against suffering. Suffering is not inevitable. Human beings have the ability to actively influence their fate and relieve suffering. And essentially, the desire to extend life does not imply a desire to prolong suffering, but a desire to prolong health (increase the healthspan).

Would extending longevity lead to extending boredom? Arguably no, as extended life also implies extended ability to learn and change. The sense of boredom does not necessarily depend on the period, and often comes and goes periodically. And generally, the feeling of boredom does not seem to be a sufficient reason to abandon the pursuit of life. And if it is (for some people) - their choices are in their hands, and should not diminish the choices and chances of others.

Would extending longevity make human life meaningless? Arguably no, as life may carry a meaning of its own, independent of death. It is difficult or even impossible to place a temporal limit on the meaning, love and enjoyment of life. Human beings are entitled to choose a prolonged existence, and that choice and pursuit alone may give their life meaning.

Would not extending longevity stop progress, make individuals and societies stagnant? Rather to the contrary, the potential for learning will be increased by longer life-spans, and such a prolonged "cultural adaptation" may be sufficient and necessary for the survival of the society. Moreover, rationally controlled development and care for the survival of the weak may be more advantageous for progress than blind and cruel Darwinian selection.

Are not aging and death from aging natural and inevitable? Does not their acceptance as natural and inevitable give comfort in facing them? Concerning the inexorable "natural" limit to the human life, however comforting a reconciliation with death may be, it should not replace an active quest for life preservation. Almost never is a particular cause of death completely "inevitable," but is always due to some identifiable material agent, and thus subject to prevention or amelioration. There is no limit "set in stone" to either the lifespan or the healthspan.

Would not the life-extending means be made available only for the rich and powerful, or some other select groups? How can we prevent this injustice? Indeed, perhaps the most frequent type of worry relates to the future availability of resources due to life extension. The common assumption is that 'there will never be enough for everybody'. Yet, in any case, the inequality of access does not seem to be a reason to hinder the emergence of new medical technologies, but only to intensify their development. The sooner they emerge, the faster they will likely become available for the people, hopefully for all.

Would not extending longevity lead to shortage of resources for the society, or "overpopulation"? It has been a persistent fear that extending longevity would lead to a shortage of resources for the global population as a whole due to its unsustainable increase. This scenario is also commonly known as 'the problem of overpopulation due to life extension'. Yet, it must be argued that the term "overpopulation" does not simply relate to the number of people on a certain territory. Rather, it indicates the degree of availability of resources, especially food, for people at that territory. And, based on the available evidence and trends of development, scarcity of resources should not be anticipated as a result of increasing longevity. It was calculated already in the 1960s by the Agricultural Economics Research Institute, Oxford, that the agricultural productivity, even at that time, would be more than sufficient to feed 45 billion people globally. Since that time the agricultural capabilities in the developed countries increased dramatically, way ahead of increases in life expectancy or population. The technological capabilities are here to feed the world.

Would not increasing life quantity mean decreasing life quality? In other words, wouldn't we have "too many old sick people"? It must be emphasized that the improvement in life quantity is commonly (though not always) inseparable from the improvement in life quality. A robust organism (similar to a robust machine) as a rule both operates efficiently and for longer periods of time. Essentially, it is the extension of the human healthspan (healthy and productive lifespan) and not just of the lifespan that is pursued in the research and development of new medical means and technologies.

The main obstacle slowing down progress in the development of anti-aging and life-extending therapies is perhaps the immense scientific difficulty of the problem itself. Aging is an extremely complex process, with many uncertainties. Hence, any potential attempts at intervention will yet require a vast amount of careful thought and effort. This does not mean that such attempts should be abandoned. On the contrary - we need to tackle the problem, "not because it is easy, but because it is hard." The payoff from its solution would be too great to abandon. But we need to admit that the problem is difficult and therefore its solution will require strong efforts. People would need to make such efforts, and they are not always willing or ready to make them. Hence one of the major bottlenecks is perhaps the general deficit in the ability or willingness of many people to invest time, effort, money and thought for the development of healthspan and lifespan extending therapies and technologies. Clearly, the more people become supportive and involved for their development, the more resources are intelligently and productively invested in it, the faster the technologies will arrive and the wider will be their availability.

Studying the Beneficial Effects of Intermittent Fasting and Calorie Restriction

This article from the more scientific end of the popular science press covers recent research into the beneficial effects of calorie restriction and intermittent fasting in humans. These interventions have been shown to extend life and improve health in near all species tested to date, slowing measures of aging along the way. This area of the field has grown in recent years, with the addition of a fair amount of new human data. Fasting and low calorie diets have been tested as adjuvants for cancer treatment, for example, and as independent ways to improve metrics of health.

When external calories stop fueling an animal's metabolism, stores of triglycerides in fat cells are mobilized, and levels of ketones - chemicals that result from the burning of fat for fuel - rise. Decreases in body weight follow. Scientists are further detailing both the underlying metabolic dynamics and interesting physiological phenomena aside from weight loss as they study permutations of fasting in animal models and in humans. Data has recently emerged from research on several forms of so-called intermittent-fasting regimens, including alternate-day fasting, the so-called 5:2 diet, time-restricted feeding, and periodic fasting. Although these regimens vary, they all involve a rhythmic disruption in the typical flow of calories into the metabolic machinery. As the body of scientific literature around fasting has grown, results have been cherry-picked and molded into fad diets. But as books of dubious scientific merit extolling the virtues of fasting fill the shelves, serious researchers continue to probe the genetic, immunologic, and metabolic dynamics that occur in fasting animals to separate hype from reality.

For the majority of genus Homo's more than 2 million year evolution, hominins' access to nutrients and calories was spotty, at best. Perhaps our ancestors, and their digestive systems, evolved to endure periodic bouts of starvation. Oscillations between feast and famine may even have served as a selective pressure, tuning early human physiology to function optimally in an environment where resources were unpredictable. "Individuals whose brains and bodies and physical performance were optimal in a fasted state would be more likely to get food and compete with other individuals who were not able to function at quite as good a level. So the assumption then is that we evolved probably most of our organ systems to be able to function optimally in intermittent fasting-type conditions."

Results from studies in both animal models and humans point to distinct benefits of withholding food in one temporal pattern or another. In recent years, scientists have learned that fasting might trigger not only weight loss and life-span extension - benefits that have long been linked to caloric restriction - but also boost the performance of the brain, the immune system, and organs central to metabolism, such as the liver and pancreas. Fasting, some researchers claim, can even alter the course of some diseases, from cancer and multiple sclerosis to diabetes and Alzheimer's.

Fasting that involves longer periods of food deprivation can cause changes to the immune system and the hematopoietic stem cells that support it. Researchers are finding that periodic fasting, less frequent but longer bouts of severe calorie restriction, can reshape immune cell populations in the body. One research group employs the fasting-mimicking diet (FMD). Using a periodic three-day FMD regimen for 30 days in a mouse model of multiple sclerosis, the researchers showed that the fast-and-feed cycles pruned away populations of autoimmune T cells, replacing them with immune cells that were no longer bent on attacking neural tissue. Oligodendrocyte precursor cells regenerated and remyelinated axons, and the clinical severity of the autoimmune disorder declined. "One in five of the mice went to back to no symptoms at all. One in two of the mice went down to very low levels of the symptoms. The real benefit that we've shown in a number of papers is about killing damaged cells and then turning on stem cells. And then in the refeeding period, [stem cells are] replacing the dead cells with newly generated cells. I think that is where the real benefit is."


Considering Efforts to Repair the Signs of Aging

The research team who recently assessed the effects of FOXO4-DRI on clearing senescent cells here publish a short commentary on the broader scope of targeting the causes of aging for repair. Note that the commentary is available in PDF format only at this point. It is good to see more scientists, and even some of the more conservative voices in the research community talking openly on this topic, advocating progress towards rejuvenation. This is a considerable change in comparison to the state of the field even as recently as fifteen years ago, a time when researchers largely kept silent for fear of losing grants and the opportunity for career advancement.

"Targeting signs of aging". It sounds more like a punch-line of a TV commercial, than a consequence of fundamental science. But as we observed recently, it might actually be possible to achieve just that, using a prospectively designed FOXO4-p53 interfering peptide that targets so-called "senescent" cells. More research is needed to fully assess its true translational potential and whether it is even safe to remove such cells. However, these findings pose a very attractive starting point to develop ways to live out our final years in better health.

Aging has often been considered as an integral part of life; a form of "noise" that cannot be targeted or tampered with. This is in part because for long the underlying causes of organismal aging were simply too elusive to comprehend, let alone modify. The chronic build-up of DNA damage has now evidently been established as a major cause for aging, but to counteract the genomic damage that has occurred over a lifetime is an entirely different challenge altogether. One approach to overcome this issue, is to eliminate those cells that are too damaged to faithfully perform their duty and to replace them by fresh and healthy counterparts. Senescent cells are exciting candidates for such an approach.

Comparable to formation of rust on old equipment, like a bicycle, senescent cells accumulate during aging and especially at sites of pathology. They develop a chronic secretory profile that is thought to impair tissue renewal and contribute to disease development, for instance by keeping neighboring cells "locked" in a permanent state of stemness. Senescence can be beneficial in a transient setting, but the genetic removal of senescent cells over a prolonged period of time was found to be safe and to potently extend health- and lifespan of naturally aging mice. Thus, senescence is an established cause for aging and targeting senescent cells is warranted. But can they also be eliminated therapeutically? And are such methods then safe on their own? And last, but not least, would such methods be applicable to not merely delay, but also to reverse aging?

Aging is still inevitable. But perhaps it can be strongly postponed, or even reversed, when independent anti-aging therapies are combined? It remains to be determined whether extension of lifespan is possible in humans, let alone whether this is desirable and then to what age? After all, life could at some point not simply "complete"? While this might be true for some, nobody likes being sick and frail. Imagine the possibilities if we would be able to enjoy our time with loved ones, exercise and travel more and simply just enjoy life in good health, instead of spending it in a retirement home.

Extending the healthy years of life is now closer than ever, but we are still not there yet. While mechanics can remove defective parts from an old bicycle, it is far more challenging to remove damaged parts from an old body. Anti-aging strategies have therefore necessarily focused thus far on stalling the inevitable for as long as possible by eating less and exercising more. A multitude of new diets make it to the mainstream public each year, but ironically, people tend to exercise less and gain more and more weight. This argues that instead of focusing so much on dietary interventions, independent approaches deserve to be investigated. Here, we underscored the potential of therapeutic elimination of senescent cells, for instance by FOXO4-DRI. In addition, exciting developments were recently reported in the field of stem cell biology, where it was shown that transient expression of the Yamanaka stem cell factors can promote tissue rejuvenation. This is not yet therapeutically applicable, but most likely this will only be a matter of time.

It is no longer merely science-fiction to restore healthspan with rationally designed approaches. To fully achieve the best possible outcome, it will therefore deserve special consideration to combine existing methods to delay aging with the recently developed therapies that counter senescence and promote tissue rejuvenation. With these, we finally have exciting tools to maintain and repair the aging cycle of life. Time to gear up and head for the finish!


Yet More Research Groups are Aiming to Make the Heart More Regenerative

The heart is one of the least regenerative of tissues in mammals, and we might well stop for a moment to ask why this is the case. Species capable of exception regeneration, such as salamanders and zebrafish, can regrow entire sections of the heart when injured. But even restricting ourselves to a consideration of mammals, why is it that the heart cannot regenerate as well as, say, the liver, the most regenerative of adult mammalian organs? Asking why the heart cannot regenerate goes hand in hand with asking how to change this state of affairs. There are a fair number of research groups involved in various different approaches to the questions above and the consequent development of treatments. It is a busy corner of the field. Even putting aside work on the comparative biology of salamanders, zebrafish, and other proficient regenerators, in just the last few months there have been papers on the manipulation of PORCN and activation of STAT3 as ways to enhance heart regeneration, bringing it more in line with other tissues.

What would we gain with a more regenerative heart? Probably a lower mortality rate for cardiovascular disease, though it is hard to say just how most of these manipulations would interact with the disruption of regenerative processes and reduced tissue maintenance that is present in older individuals. Any improvement in healing would reduce mortality following a heart attack, but this is a poor second best to preventing such injuries from happening in the first place. I think the most likely place for this sort of thing in the future roadmap for applied rejuvenation biotechnology is to help remediate the structural damage done to heart tissue over the course of aging. The first old people to undergo repair therapies that remove the low-level cell and tissue damage that causes aging will still be left with hearts that have remodeled and weakened as a consequence of decades of an increasing load of that damage. You might read around the topic of ventricular hypertrophy in this context, for example. These structural changes will not fix themselves, as things stand in the normal operation of even youthful human biology, and thus some form of enhanced and guided regeneration will be required to set matters to rights.

Here, I'll point out a couple more examples of recent research into heart regeneration: why it is suppressed, and how it might be improved. They are quite different from one another, and from the examples noted above, which is encouraging. When there are numerous diverse approaches to a problem in biotechnology or medicine, it is that much more likely that at least one of the approaches will, in the end, prove both useful and practical.

New insight into why the heart does not repair itself

Heart muscle is one of the least renewable tissues in the body, which is one of the reasons that heart disease is the leading cause of death. Researchers have studied pathways known to be involved in heart cell functions and discovered a previously unknown connection between processes that keep the heart from repairing itself. "We are investigating the question of why the heart muscle doesn't renew. In this study, we focused on two pathways of cardiomyocytes or heart cells: the Hippo pathway, which is involved in stopping renewal of adult cardiomyocytes, and the dystrophin glycoprotein complex (DGC) pathway, essential for cardiomyocyte normal functions."

Previous work had hinted that components of the DGC pathway may somehow interact with members of the Hippo pathway. The researchers genetically engineered mice to lack genes involved in one or both pathways, and then determined the ability of the heart to repair an injury. These studies showed for the first time that dystroglycan 1, a component of the DGC pathway, directly binds to Yap, part of the Hippo pathway, and that this interaction inhibited cardiomyocyte proliferation. "The discovery that the Hippo and the DGC pathways connect in the cardiomyocyte and that together they act as 'brakes,' or stop signals to cell proliferation, opens the possibility that by disrupting this interaction one day it might be possible to help adult cardiomyocytes proliferate and heal injuries caused by a heart attack, for example."

Young at Heart: Restoring Cardiac Function with a Matrix Molecule

Heart disease remains the leading cause of death worldwide, yet the few available treatments are still mostly unsuccessful once the heart tissue has suffered damage. Mammalian hearts are actually able to regenerate and repair damage - but only up to around the time of birth. Afterward, that ability disappears, seemingly forever. Research at has uncovered a molecule in newborn hearts that appears to control the renewal process. When injected into adult mouse hearts injured by heart attacks, this molecule, called Agrin, seems to "unlock" that renewal process and enable heart muscle repair.

Following a heart attack in humans, the healing process is long and inefficient. Once damaged, muscle cells called cardiomyocytes are replaced by scar tissue, which is incapable of contracting and thus cannot participate in pumping. This, in turn, leads to further stress on the remaining muscle and eventual heart failure. Heart regeneration into adulthood does exist in some of our fellow vertebrates. Fish, for example, can efficiently regenerate damaged hearts. Closer relatives on the evolutionary tree - mice - are born with this ability but lose it after a week of life. That week gives researchers a time window in which to explore the cues that promote heart regeneration.

Researchers believed that part of the secret might lay outside of the heart cells themselves - in the surrounding supportive tissue known as the extracellular matrix, or ECM. Many cell-to-cell messages are passed through this matrix, while others are stored within its fibrous structure. So the team began to experiment with ECM from both newborn and week-old mice, clearing away the cells until only the surrounding material was left, and then observing what happened when bits of the ECM were added to cardiac cells in culture. The researchers found that the younger ECM, in contrast to the older, elicited cardiomyocyte proliferation.

A screening of ECM proteins identified several candidate molecules for regulating this response, among them Agrin. Agrin was already known for its effects on other tissues - particularly in the neuromuscular junction, where it helps regulate the signals passed from nerves to muscles. In mouse hearts, levels of this molecule drop over the first seven days of life, suggesting a possible role in heart regeneration. The researchers then added Agrin to cell cultures and noted that it caused the cells to divide.

Next, the researchers tested Agrin on mouse models of heart injury, asking whether it could reverse the damage. Indeed, they found that following a single injection of Agrin mouse hearts were almost completely healed and fully functional, although the scientists were surprised to find that it took over a month for the treatment to impart its full impact on cardiac function and regeneration. At the end of the recovery period, however, the scar tissue was dramatically reduced, replaced by living heart tissue that restored the heart's pumping function. The researchers speculate that in addition to causing a certain amount of direct cardiomyocyte renewal, Agrin somehow affects the body's inflammatory and immune responses to a heart attack, as well as the pathways involved in suppressing the fibrosis, or scarring, which leads to heart failure. The length of the recovery process, however, is still a mystery, as the Agrin itself disappears from the body within a few days of the injection.

If in a speculative mood, you might revisit research published last year in which the authors demonstrated that extracellular matrix taken from zebrafish, a species capable of regenerating heart tissue, produced enhanced regeneration in mouse hearts following transplant. It would be interesting to see whether or not agrin is the mediator of that effect as well.

More Autophagy is Good, and More Resistant Macrophages Slow Atherosclerosis

This research neatly demonstrates two quite different points. Firstly, that increased autophagy in our cells is generally a good thing, and a good basis for a range of therapies. It makes cells more efficient and more resistant to stress. Secondly, that finding ways to make the immune cells known as macrophages more efficient and more resistant to stress helps to slow the progression of atherosclerosis. Macrophages are responsible for cleaning up the oxidized lipids and fatty garbage that form the atherosclerotic plaques that disrupt blood vessel structure. Unfortunately these cells are easily overwhelmed, and much of the mass of these plaques in fact consists of the debris from dead macrophages by the time the disease reaches its dangerous later stages, in which major blood vessels are vulnerable to rupture. There are other studies to show that any method of making macrophages tougher and more resilient helps. That said, I think that the best class of approach to this challenge is to find ways to break down and remove at least the most challenging of the lipids, rather than trying to engineer a better class of macrophage. The former should be easier than the latter.

Studying mice, researchers have shown that a natural sugar called trehalose revs up the immune system's cellular housekeeping abilities. These souped-up housecleaners then are able to reduce atherosclerotic plaque that has built up inside arteries. Such plaques are a hallmark of cardiovascular disease and lead to an increased risk of heart attack. "We are interested in enhancing the ability of these immune cells, called macrophages, to degrade cellular garbage - making them super-macrophages."

Macrophages are immune cells responsible for cleaning up many types of cellular waste, including misshapen proteins and excess fat droplets. "In atherosclerosis, macrophages try to fix damage to the artery by cleaning up the area, but they get overwhelmed by the inflammatory nature of the plaques. Their housekeeping process gets gummed up. So their friends rush in to try to clean up the bigger mess and also become part of the problem. A soup starts building up - dying cells, more lipids. The plaque grows and grows."

The showed that mice prone to atherosclerosis had reduced plaque in their arteries after being injected with trehalose. The sizes of the plaques measured in the aortic root were variable, but on average, the plaques measured 0.35 square millimeters in control mice compared with 0.25 square millimeters in the mice receiving trehalose, which translated into a roughly 30 percent decrease in plaque size. The difference was statistically significant, according to the study. The effect disappeared when the mice were given trehalose orally or when they were injected with other types of sugar, even those with similar structures.

Past work by many research groups has shown trehalose triggers an important cellular process called autophagy, or self-eating. But just how it boosts autophagy has been unknown. In this study, researchers show that trehalose operates by activating a molecule called TFEB. Activated TFEB goes into the nucleus of macrophages and binds to DNA. That binding turns on specific genes, setting off a chain of events that results in the assembly of additional housekeeping machinery - more of the organelles that function as garbage collectors and incinerators. "Trehalose is not just enhancing the housekeeping machinery that's already there. It's triggering the cell to make new machinery. This results in more autophagy - the cell starts a degradation fest. Is this the only way that trehalose works to enhance autophagy by macrophages? We can't say that for sure - we're still testing that. But is it a predominant process? Yes."


Identifying Loss of Stem Cells as the Primary Cause of Sarcopenia

The decline in muscle mass and strength that occurs with aging, known as sarcopenia, is thought to correlate with a loss of motor neurons, theorized to be an important cause of the process. Researchers here point instead to loss of stem cells as the primary cause of age-related muscle decline. Stem cell activity is well known to fade with age, an evolutionary adaptation to increasing levels of tissue damage that may serve to reduce cancer risk. Progress in the stem cell research field to date, such as the development of therapies based on spurring more youthful levels of stem cell activity in the old, suggest that there is considerable room for greater regeneration without higher rates of cancer, however.

Researchers have discovered that loss of muscle stem cells is the main driving force behind muscle decline in old age in mice. Their finding challenges the current prevailing theory that age-related muscle decline is primarily caused by loss of motor neurons. Study authors hope to develop a drug or therapy that can slow muscle stem cell loss and muscle decline in the future. As early as your mid 30s, the size and strength of your muscles begins to decline. The changes are subtle to start - activities that once came easily are not so easy now - but by your 70s or 80s, this decline can leave you frail and reliant on others even for simple daily tasks. While the speed of decline varies from person to person and may be slowed by diet and exercise, virtually no one completely escapes the decline.

All adults have a pool of stem cells that reside in muscle tissue that respond to exercise or injury - pumping out new muscle cells to repair or grow your muscles. While it was already known that muscle stem cells die off as you age, the study is the first to suggest that this is the main driving factor behind muscle loss. To better understand the role of stem cells in age-related muscle decline, researchers depleted muscle stem cells in mice without disrupting motor neurons, nerve cells that control muscle. The loss of stem cells sped up muscle decline in the mice, starting in middle, rather than old age. Mice that were genetically altered to prevent muscle stem cell loss maintained healthier muscles at older ages than age-matched control mice.

At the same time, researchers did not find evidence to support motor neuron loss in aging mice. Very few muscle fibers had completely lost connection with their corresponding motor neurons, which questions long-held and popular theory. According to the theory, age-related muscle decline is primarily driven by motor neurons dying or losing connection with the muscle, which then causes the muscle cells to atrophy and die. "I think we've shown a formal demonstration that even for aging sedentary individuals, your stem cells are doing something. They do play a role in the normal maintenance of your muscle throughout life."


Reviewing What is Known of PTEN and its Longevity Effects

The PTEN gene shows up in a number of places in aging research, and today's paper is a review of what is known of its relevance to the field. To pick a few items, PTEN appears to be involved in some of the processes and pathways that control nutrient sensing, and is thus of interest to researchers attempting to recreate the beneficial effects of calorie restriction via pharmaceuticals. It is also involved in regeneration and cancer as a governor that prevents excessive cell growth. In this context, PTEN suppression has been shown to enhance nerve regrowth in mice, but of course there are other, adverse consequences to turning off a cancer suppression gene should that be accomplished too broadly or for too long a period of time. Moving the dial in the other direction, researchers have found that increasing the amounts of protein generated from the PTEN gene reduces cancer incidence and extends life in mice.

To find a cancer suppressor that also extends life when present in larger amounts is actually somewhat unexpected. The (perhaps overly) simple view of cancer suppressor genes is that they act to reduce cellular replication, which in turn diminishes tissue maintenance more rapidly as aging progresses. The net result is mixed: less cancer, true, but also a shorter life span and greater incidence of frailty. This is the case for the general application of tumor suppressor gene p53, for example. But even for p53, it is possible to find more subtle ways to apply the increase, such as only generating more p53 in the situations where it is needed, rather than all the time. That can both extend life and reduce cancer. The unusual nature of PTEN is that more of it, applied globally, has this wholly beneficial effect, without the need for subtlety. The results from the first PTEN study of cancer and aging suggested that the observed slowing of aging in mice was a matter of altered fat metabolism: the mice were lean, energetic, and suffered lesser degrees of insulin resistance. It is known that visceral fat is important in aging, and in mice a significant increase in life span can even be obtained via the very blunt solution of surgical removal of that fat in adult life.

In humans, when compared to mice, lifestyle influences such as calorie restriction and the level of visceral fat tend to have similar short-to-mid-term effects on health, but lesser effects on longevity. Calorie restriction can reliably increase life span by 40% in mice, but in humans it is more likely to be somewhere near five years at most. We are long-lived for our size as mammals, and there are evolutionary arguments to explain why it is that low or high calorie intake and resulting levels of fat tissue have a smaller effect on life span in our species. Enhanced longevity in response to calorie restriction evolved because it increases survival in the face of famine. Famines are seasonal, however, and while a season is a sizable fraction of the mouse life span, it is small in comparison to a human life span - so only the mouse has the evolutionary pressure to evolve a very plastic lifespan, capable of living half as long again when there is little food.

This paper can be taken as an example of present opinions on aging and longevity at the more optimistic end of the portion of the research community that seeks to modestly slow aging by altering metabolism. This usually involves changing circulating levels of proteins important in core cellular processes such as replication or nutrient sensing, of which PTEN is one example. While it is always pleasant to see more researchers explicitly advocating extension of healthy life span as a goal, I have to say that I don't think that this high level strategy is the right approach. It is an expensive, slow road to small benefits. If we are to live significantly longer than past generations, that must be achieved through comprehensive repair of the cell and tissue damage that causes aging, not by altering our metabolism so as to slightly slow the pace at which that damage accumulates. In the near term of the next few decades, only the former can reverse the progression of aging, only the former is useful to people already old, and only the former can produce very large increases in healthy life span.

PTEN, Longevity and Age-Related Diseases

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN, also known as MMAC1 and TEP1) was first discovered in 1997 by two independent groups and recognized as the long sought after tumor suppressor gene frequently lost on human chromosome 10q23. This locus is highly susceptible to mutation in human cancers: the frequency of mutations have been estimated to be 50%-80% in sporadic tumors such as glioblastomas, prostate cancers and endometrial carcinomas; and 30%-50% in lung, colon and breast tumors. PTEN is often associated with advanced cancers and metastases, due to loss of PTEN having been observed at its highest frequency in late stages of cancers. Together with p53, Ink4a and Arf, PTEN makes up the four most important tumor suppressors in mammals as evidenced by their overall high frequency of inactivation across a variety of cancer types. Because of this, it is vital to understand the mechanisms of how PTEN functions.

The main function of PTEN is to antagonize the PI3K/AKT pathway, thereby opposing the pathway's cell proliferative response and, more important to longevity, opposing AKT's downregulation of antioxidant genes and proteins. In concert with this function, PTEN has been reported to bind with another antioxidant gene, p53, and arresting the cell cycle whilst positively regulating protein dealing with DNA-damage. These functions serve not only to extend cellular longevity but also prevent deleterious DNA-damage that can lead to malignant tumors.

The purpose of the report is to serve as a comprehensive review of the links that have been made between PTEN and the potential effects it may have on ageing. It will cover various issues such the regulators of PTEN, the regulatory effects of PTEN, its cellular functions, its associations with cancer and its direct effects on longevity in the effort to understand the many and varied pathways that PTEN is a part of, and how these intricate and integral pathways are key to effecting longevity. While Ponce de León's dream of a fountain of youth may be unobtainable as of yet, this report will show that extended longevity is highly possible. This paper follows in the theme of recent papers which show the strides that anti-ageing research have made over recent years. PTEN has the potential the play a crucial role alongside these other studies as, beyond its documented ability to extend longevity, its function as a tumor repressor is vital to any lasting extended longevity to prevent the rise of tumors often associated with extended longevity.

To sum up a lengthy report: PTEN has significant implications for extending human longevity through its actions on DNA-damage reduction, antioxidant activity, caloric restriction, inhibition of replication and tumor suppression. The importance cannot be overstated as PTEN overexpression can assist a variety of maladies including weight-related diseases such as diabetes to age-related diseases such as Alzheimer's and Parkinson's. Its function as a tumor suppressor can maintain an anguish-free life. It is because of this variety and necessity of function that PTEN is a vital subject for further research. Through studies done on invertebrates and on mammals we have seen that the application of this knowledge is successful, that PTEN's effect on longevity is not merely theoretical but practical. That PTEN can enhance longevity is no longer questionable, but neither is it irrefutable. Before any final concluding statements can be made, human trials with PTEN transfection must first be done. The authors of this study are currently working on cell culture trials, which is only the first step.

PTEN alone cannot extend longevity indefinitely, however, as a past study demonstrated only a 9%-16% increase in longevity, and while this is a significant milestone, this is hardly the fountain of youth that Ponce de León dreamt of. This is not to say that such a dream may not happen, merely that PTEN alone would not accomplish it. Others presented findings that telomerase can reverse tissue damage in aged mice. This rejuvenative quality bodes well as a potential partner for PTEN, and its most important feature, that of telomere extension, could potentially extend longevity as long as needed. PTEN is well suited as a partner for telomerase due to its tumor suppressive quality. This is because of two reasons. Telomerase have been commonly associated with cancer and a tumor suppressor may prevent this. However, more importantly, the longer one lives, the probability of having cancer increases. It is PTEN's tumor suppressive quality that sets it apart from other recent studied genes such as SIRT1.

The variety of genes, proteins and enzymes being studied today show how the interconnectivity of the human system also necessitates a complex solution to longevity. Whether this is achieved through the main pathways of telomerase, SIRT1, PTEN or others remains to be seen. What must be done now is testing, and further testing, until an answer is found. With the importance of such work, it deserves no less. While human trials oblige a lengthy testing time, it is an inevitable obstacle that must be overcome if Pons de León's dream is to be fulfilled.

Chimeric Antigen Receptor Therapies Continue to Do Well Against Blood Cancers

Chimeric antigen receptor approaches to cancer treatment involve taking a patient's T cells and equipping them with a new receptor that allows the immune cells to target specific characteristics of cancer cells. Despite the usual complications and challenges that tend to occur in the development of immunotherapies, involving potentially dangerous disruption of the immune system, this type of therapy has proven to be highly effective against blood cancers. It remains to be deployed against solid cancers, although researchers are well on their way towards reaching that goal, but there is every reason to expect it to be just as effective in that scenario.

In an early clinical trial, 33 out of 35 (94%) patients had clinical remission of multiple myeloma upon receiving a new type of immunotherapy - chimeric antigen receptor (CAR) T cells targeting B-cell maturation protein or BCMA. Most patients had only mild side effects. "Although recent advances in chemotherapy have prolonged life expectancy in multiple myeloma, this cancer remains incurable. It appears that with this novel immunotherapy there may be a chance for cure in multiple myeloma, but we will need to follow patients much longer to confirm that."

CAR T-cell therapy is custom-made for each patient. The patient's own T cells are collected, genetically reprogrammed in a lab, and injected back into the patient. The reprogramming involves inserting an artificially designed gene into the T-cell genome, which helps the genetically reprogrammed cells find and destroy cancer cells throughout the body. Over the past few years, CAR T-cell therapy targeting a B-cell biomarker called CD19 proved very effective in initial trials for acute lymphoblastic leukemia (ALL) and some types of lymphoma, but until now, there has been little success with CAR T-cell therapies targeting other biomarkers in other types of cancer. This is one of the first clinical trials of CAR T cells targeting BCMA, which was discovered to play a role in progression of multiple myeloma in 2004.

The authors report results from the first 35 patients with relapsed or treatment-resistant (refractory) multiple myeloma enrolled in this ongoing phase I clinical trial in China. First signs of treatment efficacy appeared as early as 10 days after initial injection of CAR T cells (patients received three split doses of cells over a week). Overall, the objective response rate was 100%, and 33 (94%) patients had an evident clinical remission of myeloma (complete response or very good partial response) within two months of receiving CAR T cells. To date, 19 patients have been followed for more than four months, a pre-set time for full efficacy assessment by the International Myeloma Working Group (IMWG) consensus. Of the 19 patients, 14 have reached stringent complete response (sCR) criteria, one patient has reached partial response, and four patients have achieved very good partial remission (VgPR) criteria in efficacy. There has been only a single case of disease progression from VgPR; an extramedullary lesion of the VgPR patient reappeared three months after disappearing on CT scans. There has not been a single case of relapse among patients who reached sCR criteria. The five patients who have been followed for over a year (12-14 months) all remain in sCR status and are free of minimal residual disease as well (have no detectable cancer cells in the bone marrow).

Cytokine release syndrome or CRS, a common and potentially dangerous side effect of CAR T-cell therapy, occurred in 85% of patients, but it was only transient. In the majority of patients symptoms were mild and manageable. CRS is associated with symptoms such as fever, low blood pressure, difficulty breathing, and problems with multiple organs. Only two patients on this study experienced severe CRS (grade 3) but recovered upon receiving tocilizumab, an inflammation-reducing treatment commonly used to manage CRS in clinical trials of CAR T-cell therapy. No patients experienced neurologic side effects, another common and serious complication from CAR T-cell therapy.


Deletion of Gene Enhancer DNA Improves Cancer Resistance in Mice with No Apparent Loss of Normal Tissue Function

The path to effective control of cancer involves finding common mechanisms that target many different types of cancer, departing from the present approach of one costly project for every subtype of cancer. Here, researchers undertake a novel approach to the challenge, finding a sizable region of the genome that can be deleted in mice with no apparent loss of normal function. The deletion improves cancer resistance to a degree that makes suppression of the contents of this region of the genome worth pursuing as the basis for therapies that might control many types of cancer.

Our cells each contain close to 20,000 genes, which provide the instructions needed to build our bodies and keep us alive. At any one time in the life of the cell, only some of these genes are active. The activity of each gene is constantly regulated to allow the cell to respond to changes in its environment. Enhancers are sections of DNA, outside of the genes, that act as molecular switches controlling the activity of genes. A gene can have many such enhancers; each enhancer is linked to a particular set of signals and having multiple enhancers allows the same gene to be activated by different signals in different tissues in the body.

Changes to enhancers can have serious consequences. By altering the activity of genes, an enhancer can have widespread effects on the health and behavior of a cell, including transforming it from healthy to cancerous. The small differences in enhancers also make some people more susceptible to cancers than others. If we can identify enhancers whose activity is commonly altered in cancers, it could be possible to target them through treatment. Yet, it is not clear whether targeting enhancers in this way could be effectively used to treat cancer without damaging healthy cells.

Now, researchers have examined a large enhancer region with known links to several different cancers - including prostate, breast and colon cancers - to uncover whether it also plays a critical role in healthy cells and if it could be safely targeted for treatment. The region has multiple enhancers for a cancer-linked gene called MYC and is implicated in many cancer-associated deaths every year. This particular enhancer region is found in both humans and mice, which share many genes in common. Using genetic engineering, researchers removed this enhancer region from the genetic information of a group of mice. The experiment showed that mice without the enhancer region were completely healthy. Also, when tested for cancer development, these mice were much less susceptible to several major types of cancer.

The gene desert upstream of the MYC oncogene on chromosome 8q24 contains susceptibility loci for several major forms of human cancer. The region shows high conservation between human and mouse and contains multiple MYC enhancers that are activated in tumor cells. However, the role of this region in normal development has not been addressed. Here we show that a 538 kilobase deletion of the entire MYC upstream super-enhancer region in mice results in 50% to 80% decrease in Myc expression in multiple tissues. The mice are viable and show no overt phenotype. However, they are resistant to tumorigenesis, and most normal cells isolated from them grow slowly in culture. These results reveal that only cells whose MYC activity is increased by serum or oncogenic driver mutations depend on the 8q24 super-enhancer region, and indicate that targeting the activity of this element is a promising strategy of cancer therapy.


An Update on the Work of Oisin Biotechnologies: Building Therapies for Aging, Cancer, and Other Conditions by Targeting Harmful Cells for Destruction

Oisin Biotechnologies is a creation of our core community of longevity advocates, researchers, philanthropists, and others. The present CEO, Gary Hudson, was one of the first donors to support the newly formed Methuselah Foundation fifteen years ago. The company's seed funding was provided by the Methuselah Foundation and SENS Research Foundation a few years ago. A number of people in the audience here, myself included, invested in the company early last year in order to support this initiative. The initial goal of development at Oisin Biotechnologies is the targeted destruction of senescent cells, a path to produce one of the first working rejuvenation therapies to follow the SENS model of treating aging through damage repair. Matters are proceeding apace, as described in the interview below, and Oisin is presently raising a series A round of venture funding to continue the path to the clinic.

The SENS approach is to identify and fix the root causes of aging, which are also the root causes of all age-related disease. Cellular senescence is one of these causes: a lingering population of senescent cells accumulate with age, a tiny leftover fraction of the constant flow of cells that become senescent and then, usually, self-destruct. The presence of a growing number of such leftover cells is a side-effect of the normal operation of metabolism, and is in effect a form of damage. Senescent cells generate signal molecules that spur chronic inflammation, create fibrosis, and accelerate the progression of numerous other forms of failure in tissue function. Safely destroying these cells will remove a significant contribution to degeneration, turning back the clock on this aspect of aging. This approach has been shown to extend life in mice, and reliably reverse a range of specific measures of aging and age-related disease.

Oisin Biotechnologies differs from other companies producing senolytic therapies, the name given to treatments that destroy senescent cells, in one very important way. The Oisin technology is highly adaptable, and can be programmed to kill any class of cell that has some distinct internal marker in the form of high levels of expression of a specific protein. The founders started with senescent cells based on the p16 marker, but as this latest interview with Gary Hudson makes clear, have expanded their efforts to effectively target cancer with p53, and beyond that they are really only limited by time, funding, and a good map of the internal biochemistry of the target cell type. The sky is the limit in the long term: any type of cell that is undesirable should have some distinctive chemistry that can be attacked, and there are many possible targets.

Oisin Biotechnologies has been hard at work for a year and a half since the last Fight Aging! interview; what has been accomplished?

Lots. In June and August of last year we demonstrated that naturally-aged, 80-week-old B6 mice, could be safely treated with our therapeutic and have their senescent cells (SCs) reduced significantly in a dose-dependent fashion. For example, a single treatment reduced senescence-associated β-galactosidase (β-gal) staining (a well-accepted marker for senescence) by more than 50% in the kidneys, and restored the tissue appearance to that of about 18-week-old animals. This reduction in SCs was also confirmed by DNA PCR analysis.

We were then challenged by one of our investors (the Methuselah Foundation) to explore the use of our therapeutic in oncology applications. Specifically, they asked us to explore our ability to target tumors with p53, in place of the p16 targeting we use in our anti-aging applications. The work was first done in immunodeficient NSG mice so the mice couldn't reject the human PC3 prostate cancer cells that were implanted in their flanks. Surprisingly, we saw as much as 90% reductions in tumor mass in 24-48 hours of treatment. These results were astonishing and virtually unprecedented.

We subsequently repeated these studies in immunocompetent mice intravenously infused with the aggressive B16 melanoma cell line and showed a reduction in lung tumor metastases of nearly twenty-fold over controls.

Has the Oisin cell killing technology evolved significantly since we last talked, with the new focus on cancer in addition to cellular senescence?

The platform technology is evolving, but the core idea remains the same. We've got a hammer we can wield to kill cells via apoptosis, and it's pretty effective. Exactly which cells we choose to kill will change as we target various age-related diseases. So far, we've gone after p16 and p53 expressing cells.

It might be helpful for readers if I recap our basic technology. The technology uses two elements. First, we design a DNA construct that contains the promoter we wish to target. This promoter controls an inducible suicide gene, also called iCasp9 (no relation to CRISPR's Cas9). Next, we encapsulate that DNA in a specialized type of liposome known as a fusogenic lipid nanoparticle (LNP). The LNP protects the DNA plasmid during transit through the body's vasculature, and enables rapid fusion of the LNP with cell membranes. This LNP vector is consider "promiscuous" as it has no particular preference for senescent cells - it will target almost any cell type. Once it does, the DNA plasmid is deposited into the cytoplasm and traffics to the nucleus. There it remains dormant unless the cell has transcription factors active that will bind to our promoter. If that happens, then the inducible iCasp9 is made. The iCasp9 doesn't activate unless a small molecule dimerizer is injected; the dimerizer causes the iCasp9 protein halves to bind together, immediately triggering apoptosis. This process insures that the target cells and bystander cells are left unharmed. So far, we have not observed any off-target effects.

We've also got some tweaks to both the promoter side and the effector side of the constructs that will provide even more interesting and useful extensions to the basic capability, but I can't discuss those until later this year for IP reasons.

The adaptability of the Oisin technology seems to me a big deal. Beyond cancer, what else can usefully be accomplished in medicine by killing specific cells? Do you see further diversification of the company's efforts ahead?

We've only begun to explore some of the more exotic possibilities. But clearance of immune cells that have become aberrant in some manner is on the list. No doubt many opportunities will emerge as people become more familiar with our technology. As I mentioned earlier, we only have a hammer, but it can be both powerful and yet have exquisite precision when swung properly.

If a company turns up at your door with a compelling use for the Oisin technology and the desire to license it, is that interesting? Is being a hub for many third party cell-killing efforts a viable future vision for Oisin?

Definitely. We've begun such conversations with several parties already and are eager for more.

Have you established any ongoing collaboration with other companies and research groups?

We've been talking to a number of groups, both academic and industrial, and expect to enter into collaborative agreements with several later this year.

I understand you are starting in on a larger fundraising round. How is that going?

We have begun a Series A round and have it partially filled at this time. Negotiations have begun with "the usual suspects" to fill out the subscriptions to the round. Unlike the earlier seed rounds, which were primarily filled by angel investors, it looks like this round will also have family offices, VCs, and pharmaceutical industry partners.

We're all waiting for a successful senolytic therapy to arrive at the clinic. When do you see Oisin's approach being tested in humans? What are the steps yet to be accomplished on that road?

The next step for us is a toxicology study. We will begin our first non-human primate toxicology studies in about six weeks, and expect results by September. This pilot study will be followed by GLP toxicology studies in multiple species, in compliance with regulatory guidance for pre-clinical studies that will allow us to embark on Phase 1 and 2 human trials. We haven't yet picked the indication we'll be targeting in those trials, but very likely it will be prostate cancer. Cancer is a good first indication since it provides an easier path to the clinic than is the case for more subtle aging indications. But once we have completed Phase 1 and 2, we can reuse most of the data to ease the path to the clinic for purely aging-associated indications such as COPD, atherosclerosis, or liver diseases, to name some potential targets.

I've previously mentioned companion animals as another possible route to early commercialization, and we haven't lost interest in that option, but it is frankly easier to treat humans (who don't mind holding still for a few hours while we do an infusion of LNPs) compared with a dog or cat that needs to be lightly anesthetized to be similarly treated.

When it comes to reaching the clinic more rapidly, what are your thoughts on medical tourism and privately run, transparent trials as an alternative to the FDA process for Oisin?

It's a tricky course to navigate. Naturally, we have a fiduciary duty to our shareholders, and a moral duty to our patients, not to do anything that compromises our ability to be approved for a wide range of indications in the US and Europe, among other jurisdictions. But it is also true that the barriers to market here are difficult for a small company to overcome. That's why we are talking to potential pharma partners, for example relating to our oncology indications. But we've also found that certain "western" jurisdictions are a bit easier in which to operate (Canada and Australia come to mind). So we don't have to necessarily "go offshore" - in the piratical sense - to get the first therapies to market. Yet it may be that some regulatory environments will be more conducive to treating aging indications - or indeed aging as the indication - earlier than the U.S. If so, we will work with local authorities in compliance with law to do everything we can to accelerate the approval process.

The field of senolytics has certainly blossomed in the past year; putting the Oisin approach to one side for the moment, do you have opinions on the relative quality of other senolytic technologies and companies?

Oisin believes a healthy senolytic industry will require a number of different approaches to the problem of clearing SCs. We certainly don't want to say on approach is to be preferred over another for all SC targets, at least at this stage of our ignorance. For my part, I like the "information-based" approach we are taking more than small-molecule approaches, due to the unlikeliness of off-target effects. But successful whole body repair and rejuvenation is likely to require several complementary therapies.

What can our community do to help Oisin succeed in this stage of its development?

Public interest in the field of aging therapy must, sooner or later, be translated into public policy action. Letting legislators know that working on repair and regeneration is a "public good" is the first step towards getting the FDA to accept aging as a legitimate indication for treatment.

I'd like to close by saying that SENS technology is too important to be left to a handful of us who have pledged our lives, fortunes and honor to the task. We need more researchers, more companies, and more money. Get out there and do it!

As I have said in the past, Oisin Biotechnologies is an example of a close to ideal vehicle for our community, considering things in the longer term. To the degree that this venture succeeds, a sizable amount of the gains will go to individuals who are already strong supporters of SENS rejuvenation research, and who have been for some time. Thus significant amounts of the wealth generated in the years ahead by a successful Oisin Biotechnologies will, I predict, find its way back to funding further development of the SENS roadmap for comprehensive human rejuvenation. In that sense, this stage in the growth of our community, the initial phase of commercialization, is a very important step. We must build a virtuous cycle of development, with commercial success feeding further research. The closer to our community that company founders and investors happen to be, the better off we'll all be as a result.

More Physical Activity Correlates with Less Sarcopenia

Sarcopenia is the name given to the characteristic loss of muscle mass and strength that occurs with aging. It is somewhere in the long process of being formally characterized as a disease, so in addition to the loose definition under which we could say that everyone suffers sarcopenia to some degree, there will be a formal definition in which only those with the greatest loss are said to be suffering sarcopenia. In that model, everyone else is undergoing "normal, healthy aging." I'm not much in favor of this scheme of categorization. It defines a loss of function and decline with defined causes that might be addressed as nonetheless being outside the scope of medicine, and thus propagates the current ridiculous situation in which regulatory agencies will not approve treatments for the effects of aging until they are in their final, severe stages. The mechanisms are the same under the hood, amenable to the same forms of potential therapy at any degree of resulting dysfunction.

An open question for sarcopenia, as is the case for many aspects of aging, is the degree to which it is caused by primary aging, the set of processes resulting from molecular damage that cannot be much affected or avoided at this time, versus secondary aging, the consequences of environment and lifestyle choices such as lack of exercise that can be avoided or minimized. Obviously, exercise and other forms of physical activity are fairly important when it comes to the state of muscle health, and here researchers add to the small mountain of data that exists to illustrate that point.

Although diseases related to the aging process are problematic themselves, they rarely occur in isolation and the effects of one may spark the onset of another. As such ailments progress, the importance of physical activity (PA) remains high, with previous research confirming that regular PA is essential for healthy aging. Specifically, PA plays a substantial role in lowering the risk of coronary heart disease, as well as many other age-related conditions. Although PA may have an indirect impact on some health aspects, it has a direct impact on muscle quality and quantity.

Sarcopenia, which was first described as the progressive decrease in muscle mass and strength during aging, is a syndrome that is directly affected by PA. Soon after sarcopenia was defined, muscle mass assessment had been recommended as the main sarcopenia diagnosing method. Later, several groups were formed for sarcopenia consensus on definition and diagnosis. These groups recommended including muscle strength and physical performance measurement as the additional methods for sarcopenia diagnosing.

Previous research has shown that physical inactivity contributes to the development of sarcopenia, and other studies have shown that PA increases muscle strength and muscle mass in older adults. Therefore, a strong link has emerged between PA and a lower prevalence of sarcopenia. Specifically, resistance training is generally considered to be the best countermeasure for preventing sarcopenia. Although many reviews and meta-analyses have summarized the effects of individual or combined interventions (e.g., resistance training and nutritional supplementation) on sarcopenia, a systematic review and meta-analysis of the effects of PA defined as general activity that requires more energy than resting metabolic rate (e.g., exercising, strengthening, walking, working in the garden, and so on) on sarcopenia has not been published. Therefore, the main aim of this systematic review and meta-analysis was to describe the relationship between PA and the presence of sarcopenia.

We searched for articles addressing the relationship between PA and sarcopenia. Twenty-five articles were ultimately included in the qualitative and quantitative syntheses. A statistically significant association between PA and sarcopenia was documented in most of the studies, as well as the protective role of PA against sarcopenia development. Furthermore, the meta-analysis indicated that PA reduces the odds of acquiring sarcopenia in later life (odds ratio 0.45). The results confirm the beneficial influence of PA in general for the prevention of sarcopenia.


Better Characterizing Calorie Restriction to Better Evaluate Calorie Restriction Mimetics

Work on the development of drugs to mimic portions of the response to calorie restriction is one of the most widespread of efforts to modestly slow the aging process. It is unlikely to produce enormous gains in human longevity, however, as while calorie restriction does produce striking improvements in human health, it certainly doesn't have the same impact on human longevity as it does in short-lived species. In mice, calorie restriction extends life by 40% or so, and such a large effect in humans attained only through diet would have been discovered long ago. Progress on a working calorie restriction mimetic therapy has been painfully slow and expensive, with little to show for it so far beyond increased knowledge of some areas of cellular metabolism and a handful of drug candidates that cannot be used in practice due to side-effects, unreliable results, or insignificant outcomes when they do work. Nonetheless, the efforts continues. Researchers here propose a greater level of detail when comparing the outcome of calorie restriction and drug candidates in order to better identify compounds that more accurately reproduce the calorie restriction response:

Calorie restriction (CR) without malnutrition of micronutrients has been known for decades to profoundly increase lifespan and healthspan in multiple strains of laboratory rodents. More recent studies in model organisms and nonhuman primates also provide support for increased survival or prevention of age-related pathology in these widely diverse animal models. There is interest in understanding if CR and genetic interventions that increase survival actually reduce rates of aging at the molecular level. Gene expression profiling studies of multiple tissues in aging mice have shown that CR initiated in early to mid-life delays age-related gene expression changes, suggesting a delay in aging at the molecular level. Analysis of age-dependent mortality rates suggests that CR delays aging at early ages, but is associated with a pattern that resembles a compression of the aging process in the late component of the lifespan. The mechanisms of action of CR remain unclear, and understanding how different tissues and strains of mice respond to this dietary intervention is likely to be useful in understanding how CR impacts the aging process.

Two major, interrelated CR research directions are the following: (i) the identification of mechanisms which underlie CR's favorable health outcomes and (ii) the discovery of agents which may mimic at least some of the desirable outcomes of CR in subjects fed a normal caloric intake. The development of CR mimetics (CRMs) is important because the widespread practice of CR itself is unlikely to be practical in humans. An early consideration of how to approach the identification of CRMs focused on metabolic interventions. This metabolic theme proved to be a productive avenue for the discovery of CRMs.

CRMs, in large part, are either drugs or phytochemicals. Regarding phytochemical compounds, the most widely studied compound shown to mimic CR is resveratrol. Interestingly, high-dose resveratrol does not appear to extend longevity of lean (genetically normal) mice. However, we reported that mice from a long-lived strain treated from 14 to 30 months of age with either a relatively low dose of resveratrol or CR showed fewer signs of cardiac aging than age-matched controls, implying positive effects on healthspan. Furthermore, there was striking mimicry of CR-induced transcriptional shifts by resveratrol in heart, muscle, and brain in old animals. These conflicting observations suggest that CRMs may have tissue-specific effects in aging and that a tissue-specific screening strategy may be useful in evaluating CRMs.

In this study, we utilized a gene expression profiling approach to identify robust tissue-specific transcriptional markers of CR that were significantly altered in expression in the majority of mouse strains tested. We focused on heart, gastrocnemius, white adipose tissue (WAT), and brain neocortex. Using quantitative PCR, we then screened seven candidate CRMs for their ability to influence the expression of some of the novel CR transcriptional markers in vivo. We also measured the effects of the candidate CRMs on previously characterized, nontranscriptional CR biomarkers.

Importantly, we have shown that a drug that has strong activity in modulating CR transcriptional markers (pioglitazone) also modulates physiological measures of CR, such as reduced adipocyte size and mitochondrial mass. However, pioglitazone increased the levels of the inflammatory marker TNF-α, a finding suggestive of drug side effects. The putative CR mimetic L-carnitine, an amino acid involved in lipid metabolism, exhibited even stronger effects on CR transcriptional markers while modulating adipocyte size in a manner consistent with CR mimicry. These findings support the use of tissue-specific, robust transcriptional markers of CR as an effective approach to screen and identify compounds that have the potential to mimic the beneficial effects of CR on lifespan and healthspan. We also note that based on the finding that different compounds display tissue-specific CRM activity, it appears likely that stronger CR mimicry at the organismal level may be achieved by combining different CRMs.


An Angiogenesis Hypothesis of Aging

There are many theories of aging, some with a broader scope, focused on the high level or the evolutionary explanation for aging and all of its variations in pace, and others that are more limited, examining just a few aspects of age-related decline and in search of the principle mechanisms that cause that decline. Today's example is one of the more compact theories of aging, restricting itself to considering the creation and maintenance of the network of capillaries that supplies tissues. The oxygen and nutrients carried by blood cannot perfuse far beyond blood vessels, and so every last cubic millimeter of the body must be reached by the circulatory system, where it branches out into the smallest and most numerous blood vessels, those too small to be discerned by the naked eye.

What does it tell us about aging that capillary density appears to decrease in older mammals? Cardiovascular disease is of course well known to be a major cause of mortality, but much of the focus there is on the stiffening of major blood vessels, hypertension, and dysfunction and remodeling of heart tissue. These are larger-scale phenomenon, undeniably important, but does their importance overwhelm what is going on at the small scale, in the network of capillaries throughout the body? The researchers here argue that the small scale is just as important.

One item to bear in mind when reading the paper here is that mitochondrial dysfunction of a fairly general sort, a global loss of function, is implicated in many aspects of aging. Mitochondria are the power plants of the cell, using nutrients to generate chemical energy store molecules. One might ponder on a connection between reduced capillary coverage and reduced mitochondrial activity due to a lack of nutrients; certainly a great deal of neurodegenerative disease research focuses on vascular dysfunction and consequently reduced delivery of oxygen and nutrients to the brain.

The other principle point made by the authors of this paper is that there may be a short path to therapies that can partially compensate for the loss of capillary density by spurring angiogenesis, the creation of new blood vessels. Angiogenesis has been fairly well studied in the cancer research community and elsewhere, and there are a wide range of targets and drug candidates to either increase or decrease angiogenesis rates. Since testing effectiveness would be a comparatively rapid process, it might be worth trying this approach even though it doesn't address the underlying reasons for the loss of capillary density. As to what those reasons might be, we can speculate; perhaps loss of stem cell activity, perhaps changes in the extracellular matrix, or perhaps chronic inflammation that disrupts the normal processes of regeneration and angiogenesis, to pick a few options for further discussion.

Pro-Angiogenesis Therapy and Aging: A Mini-Review

Elderly persons may experience a range of medical conditions: a fatal disease (cancer, stroke, etc.), chronic afflictions (diabetes, arthritis, atrial fibrillation, etc.), and troubling lesser ailments. The last is a collective term for 5 minor symptoms and signs of old age, which include general muscle weakness, cold intolerance, minor memory lapses, skin wrinkles, and the slow healing of bruises or abrasions in the skin. The lesser ailments of aging (LAA) are the focus of this review and are grouped together here because they may have a common vascular cause and may be treatable, as next explained.

It is well recognized that atherosclerosis in arteries and arterioles leads to major illnesses - stroke, heart disease, and peripheral vascular disease. Later in life, changes occur at the terminal end of the vascular tree, where capillaries develop looping, kinking, and extensive tortuosity. Not commonly appreciated is that capillaries also undergo significant regression in absolute number. Over 40 published studies have reported a reduced capillary density throughout the body of aged animals and people.

The development and maintenance of capillaries depend on angiogenesis - i.e., on genetically programmed levels of angiogenic growth factors (AGFs). During early growth and maturation of the body, the development and function of various organ systems involve rising levels of AGFs and an expanding microcirculation. However, during old age, people and animals show declining levels of such factors in various organ systems, paralleling the reduced capillary density. Thus, old age represents a deficiency condition for angiogenesis factors, much like hormone levels that are decreased in the elderly.

The idea that the lesser ailments may be due in part to age-associated diminished capillary density and AGFs is termed "the angiogenesis hypothesis of aging." Its corollary suggests that treatment with exogenous angiogenic factors should restore reduced capillary density in areas experimentally depleted of capillaries and may improve function in areas of naturally impaired microcirculation. Recombinant angiogenic factors have been shown to induce new capillary formation in ischemic and normoxic tissues within days, as observed in numerous animal studies. Thus, in theory, pro-angiogenesis therapy may ease the LAA after they have appeared or delay their development. This is in contrast to the pathology in the larger blood vessels, where fatty plaques and cholesterol deposits cannot be readily eliminated once acquired but only prevented in the decades before old age by avoiding risk factors - i.e., obesity, diabetes, hypertension, etc.

Countless theories have been advanced to explain aging in people but none has led to a widely accepted treatment based on reversing an underlying cause. Physiological aging is commonly assumed to be due to various causes. Indeed, if aging is the result of several enfeebling influences, then lessening any one might ease its symptoms and signs. Again, there is abundant evidence in the literature that a reduced capillary density and a waning angiogenesis occur during old age. It seems likely that these linked changes influence the physiological state of the aged body - accounting for its fading functions and possibly for the lesser ailments. A reduced cerebral capillary density may contribute to the more profound cognitive problems of old age; e.g., Alzheimer's disease.

Animal studies establish that exogenous AGFs generate new capillaries. While numerous investigators have administered recombinant AGFs to relieve specific conditions of ischemia in the human body, to my knowledge, no gerontologist has proposed pro-angiogenesis therapy for moderating or delaying the widespread reduced microcirculation occurring during old age. Therapeutic pro-angiogenesis seems a tenable consideration for the lesser ailments of the elderly. The extensive data referenced here bring to mind George Orwell's admonition "To see what is in front of one's nose needs a constant struggle."

Altering the Polarization of Microglia for Therapeutic Benefit

In past years, researchers have established that the immune cells known as macrophages are involved in wound healing, and are split into groups with different polarizations (M1 and M2) that play different roles in this process. Adjusting the balance between the numbers in each group may enhance regeneration, and a disarray in this balance of numbers appears to take place over the course of aging, perhaps contributing to the decline in regenerative capacity. This polarization and its consequences exist for microglia as well, the predominant immune cell in the brain. These cells are responsible for a great many tasks beyond those of immune cells elsewhere in the body; not just clearing debris and pathogens, but also deeply involved in the correct function of connections between brain cells, for example. In this paper, researchers discuss the potential to obtain therapeutic benefits through adjusting the balance of polarization types in the microglial population.

Microglia, the resident immune cells of the central nervous system (CNS), are highly specialized macrophages that play a fundamental role in neurodegenerative diseases. Microglia have been traditionally classified as either of the following: (1) resting with branched morphology and present in healthy brains or (2) activated with amoeboid morphology and present in diseased brains. Recent microglia classifications are more complex. Activated microglia are now recognized as being heterogeneous and plastic, and exist in various phenotypes in the CNS. Microglia can be divided into at least two types (neurotoxic or neuroprotective) based on their function. Microglia can promote neurotoxicity via the release of several pro-inflammatory mediators, such as nitric oxide, interleukin (IL)-1β, and tumor necrosis factor-alpha (TNF-α). Conversely, they can be neuroprotective and neurosupportive, via several mechanisms under certain conditions. For example, neuroprotective roles of microglia include glutamate uptake, removal of dead cell debris and abnormally accumulated proteins, and production of neurotrophic factors.

The dual nature of microglial functional polarization is consistent with the general classification of macrophages as being either the M1 (classic pro-inflammatory) or M2 (anti-inflammatory) phenotype. Specific environmental cues induce macrophages to adopt a given functionality. For example, stimulation with either lipopolysaccharide (LPS) or interferon (IFN)-γ induces activation of the classical M1 phenotype, whereas stimulation with either IL-4 or IL-13 induces the M2 activation. Microglia are critical to immune response in the CNS, and unsurprisingly, microglial functional polarization has been implicated in almost all CNS disorders, and in the progression of neurodegenerative diseases. Microglia also play key functional roles in recovery from brain injury and in the maintenance of homeostasis in the brain.

Although the specific classification of M1 and M2 functionally polarized microglia remains a topic for debate, the use of functional modulators of microglial phenotypes as potential therapeutic approaches for the treatment of neurodegenerative diseases has garnered considerable attention. The modulation of microglial polarization toward the M2 phenotype may lead to development of future therapeutic and preventive strategies for neuroinflammatory and neurodegenerative diseases.


An Update from Ambrosia on their Paid Plasma Transfusion Study

You might recall that Ambrosia was founded to obtain human data on blood plasma transfusions between young and old individuals. There has been the standard grumbling about their efforts being a paid trial without controls, but if one is only concerned with the identification or ruling out of large and reliable effects, that gets the job done. When the necessary millions of dollars for formal studies cannot be found, as is often the case, then patient paid studies are a way to make some progress. If compelling enough results are produced, than it will be much easier to fund more rigorous efforts to quantify outcomes.

This recent commentary suggests that none of the results so far are either large enough or extensive enough to definitively be something other than the placebo effect, chance, or other items such as a patient making lifestyle changes. I think there is some skepticism regarding the potential effectiveness of transfusions of young blood in any case; the data is somewhat mixed, and underlying theory on what is going on still in flux. Recent research suggests that the effects observed in parabiosis studies of mice with joined circulatory systems are due to a dilution of harmful factors in old blood rather than a delivery of helpful factors from young blood, for example. If the case, that would mean that transfusions should produce very limited results at best. Still, obtaining data is the important thing, and that is what is being done here. Those complaining the loudest should put in the work to raise funds and run a study they way they would prefer to.

Older people who received transfusions of young blood plasma have shown improvements in biomarkers related to cancer, Alzheimer's disease and heart disease. Since August 2016, Ambrosia has been transfusing people aged 35 and older with plasma - the liquid component of blood - taken from people aged between 16 and 25. So far, 70 people have been treated, all of whom paid Ambrosia to be included in the study. The first results come from blood tests conducted before and a month after plasma treatment, and imply young blood transfusions may reduce the risk of several major diseases associated with ageing.

None of the people in the study had cancer at the time of treatment, however the Ambrosia team looked at the levels of certain proteins called carcinoembryonic antigens. These chemicals are found in the blood of healthy people at low concentrations, but in larger amounts these antigens can be a sign of having cancer. The team detected that the levels of carcinoembryonic antigens fell by around 20 per cent in the blood of people who received the treatment. However, there was no control group or placebo treatment in the study, and it isn't clear whether a 20 per cent reduction in these proteins is likely to affect someone's chances of developing cancer.

The team also saw a 10 per cent fall in blood cholesterol levels. "That was a surprise." This may help explain why a study by a different company last year found that heart health improved in old mice that were given blood from human teenagers. They also report a 20 per cent fall in the level of amyloids - a type of protein that forms sticky plaques in the brains of people with Alzheimer's disease. One participant, a 55-year-old man with early onset Alzheimer's, began to show improvements after one plasma treatment, and his doctors decided he could be allowed to drive a car again. An older woman with more advanced Alzheimer's is reportedly showing slow improvements, but her results have not been as dramatic.


A High Level View of the State of SENS Rejuvenation Research

The Life Extension Advocacy Foundation (LEAF) volunteers caught up with Aubrey de Grey of the SENS Research Foundation at the recent International Longevity and Cryopreservation Summit held in Spain, and hence the publication of the high level view of current progress in SENS rejuvenation research that I'll point out today. The conference was an opportunity for members the overlapping European communities focused on longevity science, cryonics, and transhumanism to present their work, build their networks, and plan future initiatives. When it comes to longevity, the SENS research program looms large: its focus on repair of the known forms of molecular damage that cause aging so far appears to be the only approach to therapies for aging that can plausibly produce significant rejuvenation in our lifetime. Success here, meaning working rejuvenation therapies in the clinic, is conditional on continued growth in funding and support for this part of the field, however, and while a great deal has been accomplished, there is a lot of work yet to be done.

SENS: Where are we now?

RepleniSENS: Cell loss and tissue atrophy

Over the course of decades, long lived tissues like brain, heart and skeletal muscles gradually lose cells and as replacement dwindles their function becomes compromised. The brain also loses neurons which leads to cognitive decline and dementia as well as the loss of fine muscle movements. The immune system also suffers, with the thymus gradually shrinking and losing the ability to produce immune cells, leaving you vulnerable to diseases. Thankfully stem cell research and cell therapy is already a well advanced field. SENS has not needed to get involved in this area as it is well funded and moving along very rapidly. Only this month we have seen hematopoietic stem cells produced for the first time and research in this field is moving forward at a furious rate. It will be plausible in the near future that we will be able to produce every cell type within the body to replace age related losses.

OncoSENS: Cancerous cells

Cancer uses two pathways to uncontrolled growth: hijacking telomerase and using the Alternative Lengthening of Telomeres (ALT) mechanism. Both allow cancer to maintain its telomeres and grow out of control. Therapies that can inhibit these pathways could be combined and are therefore a potential way for us to defeat all cancers. ALT therapies are progressing following a successful fundraiser on last year. SENS has been developing a high throughput assay for ALT allowing cost effective candidate evaluation for drugs that can inhibit or destroy cancer cells using ALT. Within the next year a company based on ALT should be possible. Telomerase inhibiting therapies are being developed by a number of organizations and companies so the SENS Research Foundation does not need to get involved with this. Therapies that inhibit telomerase in cancer cells are already in clinical trials and are well funded.

MitoSENS: Mitochondrial mutations

As mitochondria produce the chemical energy store ATP they also generate waste products as a byproduct, in this case highly reactive molecules called free radicals. Free radicals can strike and damage parts of the cell including the mitochondrial DNA (mtDNA), which, due to their close proximity to the source of free radicals, are very vulnerable to these damaging strikes. Damaged mutant mitochondria enter an abnormal metabolic state to remain alive. This leads to cells with damaged mitochondria that dump waste into the circulation causing system wide levels of oxidative stress to rise and driving the aging process.

The solution to this problem is gene therapy to move the mtDNA to the cell nucleus where it will have a far greater level of protection from free radical strikes. The SENS Research Foundation successfully fundraised for the MitoSENS project on back in 2015. They then followed up with a publication in the prestigious Nucleic Acids Research journal showing their results in September 2016. Thanks to the support of the community the MitoSENS project succeeded in migrating not one but two mitochondrial genes to the cell nucleus, a world first. Since then progress has been rapid and they have now almost migrated 4 of the 13 mitochondrial genes. They are currently refining the process into a standardized therapy.

ApoptoSENS: Death-resistant cells

Our cells have a built-in safety device that causes cells that are dysfunctional and damaged to destroy themselves in a process known as apoptosis. However as we age cells increasingly fail to dispose of themselves in this manner and they enter a state known as senescence. As we age more of these cells build up leading to increasingly poor tissue repair and regeneration. There has been a huge level of interest in senescent cell removal therapies in the last year or two and a number of companies are currently developing senolytics. Unity Biotechnology is taking the first generation of senolytics into human clinical trials this year after being successfully funded by a number of big investors. However the heat is on as other companies are following up close behind with potentially more sophisticated approaches for removing senescent cells such as plasmid based solutions from Oisin Biotechnologies and a synthetic biology approach from CellAge who successfully fundraised on last year.

GlycoSENS: Extracellular matrix stiffening

Blood sugar and other molecules react with structural proteins in tissues and bond with them creating fused crosslinks. Crosslinks bind neighboring proteins together impairing their movement and function. In the case of the artery wall crosslinked collagen prevents the artery from flexing in time with the pulse leading to hypertension and a rise of blood pressure. The SENS Research Foundation proposes to find ways to break down these crosslinks to restore movement to the structural proteins and thus reversing the consequences of their formation. The problem for many years was obtaining enough glucosepane, the primary constituent of human crosslinks, to be able to test therapies on. Thanks to funding by the SENS Research Foundation progress at Yale University now allows the cheap production of glucosepane on demand, this means that researchers can now test directly on it and find antibodies and enzymes to dissolve the accumulated crosslinks. Yale already has some antibodies against glucosepane, it is anticipated that by the end of the year monoclonal antibodies will be available and there is strong evidence for the existence of bacteria with enzymes that can break down glucosepane.

AmyloSENS: Extracellular aggregates

Misfolded proteins produced in the cell are normally broken down and recycled within the cell, but as we age more and more misfolded proteins accumulate to form sticky aggregates. These misshapen proteins impair cell or tissue function with their presence. This extracellular junk is known as amyloid and comes in a number of types. The work SENS Research Foundation funded at UT Houston in Sudhir Paul's lab is now in the hands of his company Covalent Biosciences, hopefully we will hear some news from them in the near future. Fortunately a number of alternatives are in development such as the GAIM system that appears capable of clearing multiple types of amyloids included those associated with Alzheimer's, Parkinson's and amyloidosis. The AdPROM protein targeting system also holds promise for selectively degrading target amyloids and other undruggable proteins to treat age-related diseases.

LysoSENS: Intracellular aggregates

Cells have a number of systems for breaking down unwanted materials, the lysosome is one of them. The lysosome can be considered to be a kind of cellular garbage disposal unit which contains powerful enzymes for breaking down unwanted materials. However, sometimes materials are fused together so well that not even the lysosome can break them down. This leaves the unwanted material sitting there and over time more and more of this material accumulates until it starts to interfere with lysosomal function. The solution to this problem proposed by the SENS Research Foundation is to identify new enzymes able to digest these insoluble wastes and supply macrophages and other cells with them so they can break it down. Ichor Therapeutics is taking SENS Research Foundation technology to market for macular degeneration with a therapy that removes a Vitamin A derivative that accumulates in the eye and causes blindness. Ichor has successfully conducted a seed round and is now undertaking a 15 million dollar series A round. The company is less than a year away from human clinical trials.

It is true that the SENS initiative, the Strategies for Engineered Negligible Senescence, has come a long way from its turn of the century origins as a rallying point, a research proposal, and a few like-minded advocates and researchers. After fifteen years of earnest advocacy, fundraising, scientific work, and persuasion, some lines of SENS research are now in clinical trials and commercial development, numerous independent groups are working on SENS or SENS-like research, a great, sweeping, and positive change in the attitudes of the research community towards aging has taken place, and the SENS Research Foundation has a yearly budget of a few million dollars provided by philanthropic donations - a mix of grassroots support by our community, and the greater material support provided a few high net worth individuals. This progress is a big deal, make no mistake: collectively our community has bootstrapped something from nothing, and that something has made and continues to make a great difference to our odds of living to see aging brought under medical control.

Yet this is still the beginning of the story, the opening of the age of rejuvenation, the very first portion of a much bigger picture. A great deal of necessary growth is yet to be achieved. Wherever we stand on the upward curve of bootstrapping and success, there is still a mountain ahead. The yearly funding needs to be hundreds of millions, not a few million. SENS must become the majority concern in the broader research community, not just a handful of labs and a few dozen lines of research. I believe that is is possible for us to create this future, as success in the SENS approach of senescent cell clearance will be proof enough to direct ever more researchers and funding sources towards repair and rejuvenation as a guiding strategy rather than their current approach of tinkering with metabolism to slightly slow down aging.

In any machine, biological or otherwise, repair will almost always have better and more cost-effective outcomes than trying to alter the way in which the machine operates: remove the rust and replace the worn parts rather than merely changing the oil while hoping for the best. This has already been quite adequately demonstrated in the case of aging: repair in the sense of targeted removal of senescent cells has achieved a greater and more reliable impact on aging in a few short years of animal studies, than has been achieved by the far greater, much more expensive, and longer-lasting efforts devoted to calorie restriction mimetic development.

The potential for SENS rejuvenation research is tremendous, and we are just getting started.

Reviewing the Components of Age-Related Immune System Dysfunction

The short open access review paper noted here sketches a high-level picture of the known components of immune system aging, without going into great detail. The progressive failure of the immune system is a significant component of the frailty that accompanies old age; not only are the elderly vulnerable to pathogens that are easily resisted in youth, but the immune system fails to destroy senescent and potentially cancerous cells, increasing their contribution to aging and mortality risk. Some of this decline is the result of molecular damage after the SENS vision for the treatment of aging, but some is a matter of misconfiguration and limits.

The immune system retains a memory of the pathogens it encounters; that memory can become corrupted in a number of ways, and in the end it simply takes up too much of the limited capacity of the immune system. Capacity is limited in part because the thymus atrophies with age, reducing the supply of new immune cells to a low level in comparison to childhood. In old age, there are too many memory cells, most uselessly specialized to persistent but otherwise minor threats such as cytomegalovirus, and too few cells capable of tackling new pathogens. This part of the problem at least might be solved in the near future through selective destruction of misconfigured or damaged immune cells, and their replacement with new cells cultured from a patient blood sample.

Human aging is characterized by both physical and physiological frailty. With progressive age, the immune system and the propensity for abnormal immunity change fundamentally. Aging is associated with a decline in multiple areas of immune function. Aging is associated with a sort of paradox: a state of increased autoimmunity and inflammation coexistent with a state of immunodeficiency. Immunosenescence is a new concept that reflects the immunological changes associated with age. There are three theories that explain the phenomenon of immunosenescence.

According to the autoimmune theory of aging, the immune system tends to lose efficiency and experiences widespread dysfunction, evidenced by autoimmunity (immune reactions against one's own body proteins). Two age-related processes cause autoimmune diseases: (i) different rates of senescent cell accumulation in the immune system and target tissue/organ and heterogeneous accumulation of senescent cells in tissues/organs. Separately or combined, these two processes are at the base of autoimmune diseases. The production of autoantibodies has been hypothesized to be secondary to thymus involution with a decline of naïve T cells and the accumulation of clonal T cells with activation due to "neoantigens" during the aging process.

With advancing age the body is unable to defend itself from pathogens and results in a detrimental harm; this is the focus of immunodeficiency theory. Clinical evidence indicates that with advancing age, immune responses against recall antigens may still be conserved, but the ability to mount primary immune responses against novel antigens declines significantly. The impaired ability to mount immune responses to new antigens may result in a high susceptibility to infectious diseases. The immune responses to novel antigens rely on the availability of naive T cells. Together with the age-related thymic involution, and the consequent age-related decrease of thymic output of naive CD8+ T-cell reservoir, this situation leaves the body practically devoid of naive T cells, and thus likely more prone to a variety of infectious and non infectious diseases.

Ageing is associated with various changes in immune parameters, therefore many authors have postulated that these age-related diseases could be explained, at least in part, by an overall deregulation in the immune system response, leading to a deregulation theory of immune system aging. This is supported by an age-associated disruption to the balance of alternatively expressed isoforms for selected genes, suggesting that a modification of the mRNA processing may be a feature of human aging. The observed down regulation of toll-like receptors (TLRs) and nod-like receptors (NLRs) during the aging process may contribute to the lack of effective recognition of invading pathogens or the commensal flora. This effect results in aberrant secondary immune cell activation and could significantly contribute to morbidity and mortality at an advanced age.


Exercise and Cardiovascular Aging

As a companion piece to a recent paper on the degree to which cardiovascular aging can be postponed through lifestyle choices, here researchers review the differences observed in the cardiovascular system between people who do maintain physical activity and people who do not. While the benefits are undeniable, you can't reliably exercise your way to living to 100 in good health - the majority of physically fit people don't make it to 90 given today's level of medical technology, and everyone who lives to 100 is greatly impacted by the damage of aging. However, the fact that we live in an era of accelerating progress in biotechnology and its application to medicine suggests that every extra year counts. The technologies of tomorrow will be far more impressive than those of today. That extra year might mean that you avoid dying too early, or being too frail to benefit from the first generation of rejuvenation therapies that will emerge over the next few decades.

Chronological age is identified as the major risk factor for cardiovascular morbidity and mortality, with older people significantly more likely to have cardiovascular disease. In the absence of hypertension or clinically apparent cardiovascular disease, the cardiovascular system undergoes structural and functional changes with age that compromise cardiac reserve. These age-associated cardiovascular changes lower the threshold for the three major cardiac pathophysiological conditions such as left ventricular hypertrophy, chronic heart failure and atrial fibrillation, all seen with increasing age.

In order to understand the effects of aging on the cardiovascular system, it is important to consider the complex interaction between the heart as a pump and the afterload on the heart imposed by the arterial system. Cardiac aging is associated with progressive loss of myocytes and compensating mild hypertrophy, but also with reduced sensitivity to sympathetic stimuli that compromises myocardial contractility and pumping ability in older people. With advanced aging, the large arteries dilate, their walls become thicker and stiffer due to collagen and calcium deposition and fragmentation of the elastic fibres.

Physical activity, exercise, and associated high level of cardiorespiratory fitness reduce all cause and cardiovascular mortality, the risk of heart failure and myocardial infarction, and age-related arterial and cardiac stiffening. Epidemiologic studies investigating the association of physical activity with cardiovascular disease risk have been conducted for more than six decades now. The earliest studies from the 1950s showed that men who were physically active on the job experienced coronary heart disease mortality rates that were approximately half those of men who were sedentary at work. Following these observations, studies in the 1960s showed that men who died from coronary heart disease were approximately 40% to 50% less likely to be recreationally active, compared with men who remained alive.

Numerous epidemiological studies were published since these early investigations reporting strong association between physical activity in cardiovascular health with 30% to 40% reduction in all-cause and cardiovascular mortality in active men and women of different age. Conversely, low active and sedentary behaviour are associated with 63% greater risk to develop cardiovascular disease. From the evidence available it is now clear that physical activity and exercise can attenuate the age-related cardiovascular changes by improving functional capacity of the cardiovascular system, cardiac function, and metabolism.