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- Heart Muscle Patches as a Vehicle to Improve Cell Engraftment and Survival
- Recent Papers on the Mitochondrial Contribution to Aging
- SENS Research Foundation Raises 5 Million, Largely in Cryptocurrency Donations
- Aubrey de Grey on Ending Aging and the Relative Merits of Various Approaches
- Senescent Cells are Large, which Suggests a Few Simpler Paths to Assays for Senescence Level in Human Subjects
- BMP4-Generating Endothelial Cells Spur Regeneration of the Thymus
- ZIPAR Staff Consider the Consequences of Engineering an End to Aging
- An Attempt at Using Protein Levels Rather than Epigenetic Patterns to Build a Biomarker of Aging
- Quercetin is Probably Not a Useful Senolytic
- An Example of the Need for Research and Development Investment in Cryonics
- Delivering Microglia-Like Cells to the Brain to Break Down Amyloid-β
- Torin1 as an Example of the Search for Better Rapalogs, with a Focus on Autophagy
- Evidence for mTOR to be Involved in Vascular Aging and thus Vascular Dementia
- Suggesting that Only Minimal Loss of Synapses Occurs in Alzheimer's Disease
- The Prospect of Filtering Harmful Factors from Old Blood
Heart Muscle Patches as a Vehicle to Improve Cell Engraftment and Survival
Heart muscle patches are thin engineered sections of tissue, lacking blood vessels because construction of microvasculature is still an unsolved challenge, and small because without blood vessels there is a size limit on engineered tissue. The study here suggests that we should be thinking of a present-day heart muscle patch, and most of its structure and cells, as a disposable vehicle to deliver only a fraction of its cells, keeping them alive long enough to engraft alongside native cells. The rest of the cells in the patch last only long enough to temporarily change the balance of signaling in an aged or injured heart. That signaling ensures that native cells alter their behavior, and it may be those cells, rather than the surviving new arrivals, that perform most of the work needed to produce some form of regeneration or lasting benefit.
It is the case that most types of modern stem cell therapy work via the beneficial signals produced by the transplanted cells in the short time before they die. Comparatively few classes of cell therapy deliver cells that stick around to some degree, engrafting and prospering in the patient, and these are largely the older, more established transplant therapies. Obviously there is a continuum between all of the transplanted cells dying rapidly and most cells engrafting to become productive members of the local population, and the research community is working its way along that line, tissue by tissue. The technology demonstration here is an improvement over past work on heart tissue, but at 10% engraftment there is clearly a way to go yet when it comes to building better approaches. Cells are fragile.
In the near future, the development of regenerative medicine for each tissue type is likely to split into two quite different approaches, a first that gives up on cells and just delivers the signals, assuming progress in the mapping and categorization of those signals, and a second that works towards more reliably replacing worn and malfunctioning native cells with new cells that survive the transfer process in large numbers. The former will most likely happen first, given that numerous research groups have been working on it for some years now, but the latter is far more relevant to human rejuvenation. The research community will need to be able to reliably replace cells of many types in order to achieve the SENS vision of repair of cell loss and atrophy. Simply adjusting the signaling to try to override the age-related reaction to cell and tissue damage is limited in the benefits it can achieve, even while those benefits can look impressive in comparison to past medical capabilities.
Heart-muscle patches created from human cells improve recovery from heart attacks
Large, human cardiac-muscle patches created in the lab have been tested, for the first time, on large animals in a heart attack model. Each patch is 1.57 by 0.79 inches in size and nearly as thick as a dime. Researchers found that transplanting two of these patches onto the infarcted area of a pig heart significantly improved function of the heart's left ventricle, the major pumping chamber. The patches also significantly reduced infarct size, which is the area of dead muscle; heart-muscle wall stress and heart-muscle enlargement; as well as significantly reducing apoptosis, or programmed cell death, in the scar border area around the dead heart muscle. Furthermore, the patches did not induce arrhythmia in the hearts, a serious complication observed in some past biomedical engineering approaches to treat heart attacks.
Each patch is a mixture of three cell types - 4 million cardiomyocytes, or heart-muscle cells; 2 million endothelial cells, which are well-known to help cardiomyocytes survive and function in a micro-environment; and 2 million smooth muscle cells, which line blood vessels. The three cell types were differentiated from cardiac-lineage, human induced pluripotent stem cells, or hiPSCs, rather than using hiPSCs created from skin cells or other cell types. Each patch was grown in a three-dimensional fibrin matrix that was rocked back and forth for a week. The cells begin to beat synchronously after one day.
Past attempts to use hiPSCs to treat animal models of heart attacks - using an injection of cells or cells grown as a very thin film - have shown very low rates of survival, or engraftment, by the hiPSCs. The present study had a relatively high rate of engraftment, 10.9 percent, four weeks after transplantation, and the transplantation led to improved heart recovery. Part of the beneficial effects of the patches may occur through the release of tiny blebs called exosomes from cells in the patches. These exosomes, which carry proteins and RNA from one cell to another, are a common cell-to-cell signaling method that is incompletely understood. In tissue culture experiments, the researchers found that exosomes released from the large heart-muscle patches appeared to protect the survival of heart-muscle cells.
Large Cardiac-Muscle Patches Engineered from Human Induced-Pluripotent Stem-Cell-Derived Cardiac Cells Improve Recovery from Myocardial Infarction in Swine
Here, we generated human cardiac muscle patches (hCMPs) of clinically relevant dimensions (4 cm × 2 cm × 1.25 mm). The hCMP matures in vitro during 7 days of dynamic culture. The hCMPs began to beat synchronously within 1 day of fabrication, and after 7 days of dynamic culture stimulation, in vitro assessments indicated the mechanisms related to the improvements in electronic mechanical coupling, calcium-handling, and force-generation suggesting a maturation process during the dynamic culture.
In vivo assessments were conducted in a porcine model of myocardial infarction (MI). The engraftment rate was 10.9±1.8% at 4 weeks after the transplantation. The hCMP transplantation was associated with signiﬁcant improvements in left ventricular (LV) function, infarct size, myocardial wall stress, myocardial hypertrophy, and reduced apoptosis in the peri-scar border zone myocardium. hCMP transplantation also reversed some MI-associated changes in sarcomeric regulatory protein phosphorylation. The exosomes released from the hCMP appeared to have cytoprotective properties that improved cardiomyocyte survival. The hCMP treatment is not associated with significant changes in arrhythmogenicity.
Recent Papers on the Mitochondrial Contribution to Aging
Mitochondria are the power plants of the cell, a herd of self-replicating structures evolved from ancient symbiotic bacteria, now fully integrated into the cell. Their primary task is the production of chemical energy stores, an energetic process that produces damaging reactive molecules as a side-effect. Much of the original bacterial DNA of the distant ancestors of today's mitochondia has migrated to the cell nucleus, leaving only a tiny remnant genome in the mitochondria themselves. When looking across species with widely divergent life spans, researchers have found good correlations between species life span and some combination of mitochondrial activity (metabolic rate) and mitochondrial composition (how resilient mitochondria are to oxidative damage). This strongly suggests, independently of the copious other evidence, that mitochondria are important determinants of aging and longevity.
There are numerous ways to look at the complexities of the mitochondrial contribution to aging, and until specific repair technologies successfully reverse that contribution, the degree to which different age-related changes in mitochondria are more or less relevant to aging will continue to be a topic of active debate and exploration. In the SENS viewpoint, damage to mitochondrial DNA is most important as a primary cause of aging. It occurs either during replication or as a result of damage from reactive molecules, and can produce mitochondria that are both faulty and able to replicate more readily than their peers. Cells become taken over by broken mitochondria, and become broken themselves, producing a flood of damaged and damaging molecules that contribute to age-related conditions. On the other hand, the more mainstream research community focuses on the general malaise that affects mitochondria in old tissues, characterized by reduced energy store creation, altered dynamics of fusion and fission, and other structural changes. In the SENS view, this is probably a secondary or later consequence of other forms of cell and tissue damage.
Of the two open access papers here, the first is a general, high-level review of mitochondria in aging that paints a picture of a field in flux, moving away from established theories of past decades now proven unhelpful, but not yet entirely sure of the direction for the future. The second examines the topic of how mitochondrial DNA damage originates. There is considerable debate over whether the primary cause is DNA replication errors or the activities of reactive molecules - such as those generated in large amounts by the mitochondria themselves. This paper argues for replication errors to be the important cause, and particularly important in stem cell populations, there contributing to the age-related decline in stem cell activity. The cause of errors, while certainly interesting, is actually not all that relevant to any of the near-term potential methods of repairing or working around the problem. If there is a way to reliably fix mitochondrial DNA in near all cells, or replace it, or provide backup copies of the proteins produced from that DNA blueprint, then it doesn't matter how the damage happened.
The Aging Mitochondria
On average, a healthy person lives 80 years and one of the highest risk factors known for most human diseases and mortality is aging. Many evolutionary and mechanistic theories have been elaborated on, trying to explain why and how living organisms age. However, from a mechanistic point of view, among all the theories, those that see mitochondria as main actors occupy a particular place. Indeed, mitochondria have been at the center of one leading hypothesis for 50 years: the free radical theory. Even though the scientific community has shifted to a more complex view to explain aging, embracing a network of events, mitochondria remain of high importance because of their central position in cell homeostasis of almost every tissue. Thus, as far as the description of molecular and cellular mechanisms are concerned, mitochondria have been shown to participate in every main aspect of aging: decline of stem cell functions, cellular senescence, "inflammaging," and many others.
Mitochondrial alterations have been extensively described in aging tissues of many organs for a long time. It has been particularly studied in muscle and heart, and sarcopenia and heart failure are two main causes of physical decline in the elderly. In particular, in these two tissues, but also in others like liver, brain and adipose tissue, mitochondrial alterations during aging are multiple. In particular, the number and density of mitochondria, as well as mitogenesis, have been showed to be reduced, whereas for mitochondrial dynamics and content contradictory inconclusive results have been reported. Importantly, mitochondrial function has been regularly reported to be impaired in different aging tissues, in terms of ATP production and respiratory chain (RC) capacity/activity.
A key reported feature of aging mitochondria was the increase in somatic point mutations and large deletions in the mitochondrial DNA (mtDNA). Interestingly, these mtDNA mutations have been shown to be responsible for mitochondrial dysfunction. Since mtDNA is located very close to the major source of reactive oxygen species (ROS), oxidative damage has been considered the main cause of mutations in mtDNA. Indeed, the Mitochondrial Free Radical Theory of Aging (MFRTA) considers the oxidative damage of mtDNA as the primary event affecting RC proteins, inducing its dysfunction and increasing ROS production in a vicious cycle. Yet, this theory has been strongly challenged and the scientific community has had to adjust working hypotheses to fit with a more complex mitochondria-centered network of aging mechanisms.
Proliferation Cycle Causes Age Dependent Mitochondrial Deficiencies and Contributes to the Aging of Stem Cells
Besides the nuclear genome, a typical animal cell also has from 100 to 1000 copies of mitochondrial DNA (mtDNA) that encode core subunits of electron transport chain complexes. While converting energy to ATP and carrying out biosynthesis, mitochondria also generate free radicals that can damage DNA, proteins, and lipids nearby. The mitochondrial genome has no histone protection and lacks efficient repair mechanisms. As a result, mtDNA is particularly prone to accumulating mutations. To make matter worse, inefficient electron transport chain (ETC) complexes produced by mtDNA mutations generate more free radicals and exacerbate the mitochondrial damage in a feed-forward cycle.
Accumulation of mtDNA mutations during lifetime has been postulated to cause age-related decline of energy metabolism and impairment of tissue homeostasis. Mitochondrial "mutator" mice with an elevated rate of mtDNA mutagenesis display premature aging, which, in principle, substantiates the correlation between mtDNA mutations and aging. However, mtDNA mutations from various tissues of normally aged human or experimental animals are found to be too low to possibly elicit any pathological consequences, which argues against a causative role of mtDNA mutations in physiological aging, particularly in post mitotic tissues.
DNA replication is a source of mutations. In adulthood, most tissues consist of post mitotic cells that have a slow turnover rate of mitochondria and mtDNA, which might explain the low mtDNA mutation frequency in post mitotic tissues. Therefore, the quest for connection between mtDNA mutations and aging might have focused on the wrong target from the very beginning. On the other hand, one would expect that mtDNA mutations in actively dividing cells, such as cancer cells and stem cells, could reach a high level during the aging process. In fact, there is increasing evidence demonstrating the accumulation of mtDNA mutations in aged stem cells. Stem cells are essential for tissue homeostasis and wound repair. Age dependent deterioration of stem cells contributes to several hallmarks of aging such as impaired capability of tissue repair and increased susceptibility to cancers and infectious diseases, and thereby has been proposed to play an important role in the natural aging process.
In current study, we utilized a physiological approach to manipulate the germline stem cell (GSC) division cycle independently of chronological age in flies, and examine its impact on GSC aging and female reproductive physiology. We demonstrated that the accumulation of division cycles played a major role in maternal age dependent decline of eggs' fitness and contributed to the age dependent decline of female fecundity. Additionally, we detected increased mutations on mtDNA and observed impaired mtDNA replication in aged ovaries. The strong correlation between the decline of stem cell activity and mitochondrial dysfunction in aged ovaries suggests that mtDNA mutations caused by proliferative cycles may contribute to stem cell aging.
SENS Research Foundation Raises 5 Million, Largely in Cryptocurrency Donations
I'm pleased to note that the 2017 year end SENS Research Foundation fundraiser raised far more than anyone thought was likely - more than 5 million, in fact. This was due to the generosity of a number of high net worth individuals who committed sizable philanthropic donations from their cryptocurrency holdings. These are exciting times for the treatment of aging as a medical condition! Many thanks are due to those people, and to everyone else who supported the continued work of the SENS Research Foundation staff and associated scientific groups to reverse aging through damage repair. We stand upon the verge of a truly massive revolution in medicine, and it is the philanthropists who will get us there.
SENS Research Foundation 2017 Year End Fundraiser Achieves Over 5 Million in Donations
SENS Research Foundation (SRF), a leading Silicon Valley nonprofit focused on diseases of aging, announced today that it received over 5 Million in donations during its year end fundraising campaign. These donations included 1 Million in Bitcoin from the Pineapple Fund; 1 Million in Bitcoin from an anonymous donor; and 2.4 Million in Ethereum from Vitalik Buterin, the cofounder of Ethereum and Bitcoin Magazine.
"SENS Research Foundation is pleased by the strong support we have received from members of the tech community who are innovative leaders in utilizing cryptocurrency. We appreciate their support and look forward to partnering with them going forward. We are very grateful to all of our donors for their incredible support of our Year End Campaign. Our initial campaign goal was 250,000. We were thrilled to receive over 1400 donations totaling over 5 million in just ten weeks. Achieving this level of donation in such a short period of time shows that the momentum SENS Research Foundation has achieved is continuing to accelerate. We are looking forward to engaging even more of the tech community in our work and to continue to accelerate our progress through the expansion of our research programs. Their support makes this growth possible."
On this topic, I have a pet theory regarding wealth and its use to change the world. Historically, people who became extraordinarily wealthy have done so only after many years of work on projects that they were deeply invested in for the sake of the work, not for the sake of financial reward. Consequently they had no real idea regarding what to do with that wealth, other than to keep on moving forward in the shape that they had carved out for their lives prior to that enrichment. They became one with the process that brought them to where they were. Further, these were usually older people by that point, come to terms with the human condition, more comfortable with the world as it is, not as a younger and more fiery individual would have it be. Not everyone is worn down to acceptance - look at the large-scale, results-oriented philanthropy of Bill Gates, for example - but I think it is definitely the case that vision is often one of the early casualties of aging, and the advent of personal wealth doesn't change that situation for any given individual. For every Bill Gates there are another twenty billionaires who fail to change the world in any significant way beyond the ventures that earned them their fortunes.
Cryptocurrencies, the first application of blockchain technologies, have resulted in a sizable number of people who have become enormously wealthy in a much shorter period of time, and at younger ages, than has typically been the case in the past. Even the dotcom bubble era and its immediate sequels didn't reach these levels of youthful enrichment, and that produced a fair number of people young enough and wealthy enough to set forth to remake sections of the world in the service of loftier agendas. They escaped being shaped by the processes of their enrichment to a great enough degree to retain fire and vision. Consider the willingness to put capital towards world-changing futurist ideals exhibited by Elon Musk, Peter Thiel, Mark Zuckerberg, and Sean Parker, to pick a few. But while that generation of high net worth individuals have certainly supported the life sciences, and in Peter Thiel's case SENS rejuvenation research, they largely haven't followed Thiel's support for the goal of treating aging as a medical condition, and Thiel himself has certain not gone all-in. He hasn't followed the logic further towards its end, in that the only rational use for excess capital in this age is to develop viable treatments to reverse aging. When you can buy time with money, and not just for yourself, but for everyone, then that is the rational thing to do.
The wealthy of the blockchain community may well proceed differently. The times are different, for one, as rejuvenation research after the SENS model of damage repair is more broadly known and accepted nowadays. The technology industry of the Bay Area, still in many ways the spiritual center of modern software engineering and invention, includes a great many supporters of SENS, the Methuselah Foundation, and the SENS Research Foundation, and that number has grown considerably over the past fifteen years. Aging is an engineering problem, SENS is a set of repairs and a set of outlines for repair technologies, and engineers grasp that readily. It isn't a coincidence that there are so many engineers, software and otherwise, to be found participating in the past fifteen years of philanthropy to support progress in rejuvenation research, work based on periodic repair of the cell and tissue damage that causes aging. Now it is the case that many of those engineers in the cryptocurrency space are both young and suddenly wealthy, people who have not been worn down to an acceptance of the world as it is, have not become one with their process of enrichment. They are still willing to consider radical change to the status quo, full of the fire of success, and equipped with sufficient resources to push forward the research and development that they would like to see happen. Exciting times, as I said.
Aubrey de Grey on Ending Aging and the Relative Merits of Various Approaches
Here is the transcript of an interview, published last week, with Aubrey de Grey, advocate and coordinator of rejuvenation research, originator of the Strategies for Negligible Senescence (SENS) scientific programs, and cofounder of the Methuselah Foundation and SENS Research Foundation. Over the past fifteen years, de Grey and his growing network of allies within and outside the scientific community have had an outsized influence on the culture of aging research, on public perception of the treatment of aging as a medical condition, and on meaningful progress towards therapies capable of rejuvenation. All of this has been achieved the old-fashioned way, ignored by mainstream funding institutions, and proceeding on the basis of a great deal of hard work and the pledges and philanthropic donations provided by a small, enthusiastic, and visionary community of supporters.
At the turn of the century, the field of gerontology was run by senior researchers who actively suppressed public discussion and funding aimed at lengthening life or addressing the causes of aging. That was the product of decades of setting themselves up in opposition to the fraudulent "anti-aging" marketplace of pills and potions, but it was still the wrong thing to do - and it held back progress. At that time, despite the wealth of evidence to point the way to the molecular damage that causes aging, anyone talking seriously about treating aging was mocked. That was the environment facing the first members of the modern rejuvenation research community of patient advocates and a few brave researchers willing to risk their careers.
In the years since then, we have collectively brought about a sea change, a great transformation in both research community and culture. Now, members of the scientific community enthusiastically discuss the treatment of aging, how to intervene in its progression, without fear of repercussion. A hundred times or more the investment in viable rejuvenation research programs is taking place, and venture investment in companies working on ways to address the medical condition of aging is well underway. The first rejuvenation therapies, those based on clearance of senescent cells, are under development in startup biotech companies, on their way to the clinic. None of this would have happened anywhere near as rapidly without the actions of those first individuals brave enough to champion an unpopular cause, to provide the first philanthropic funding for advocacy and research, to step up and make a difference, to swim against the current of the times.
Ending Aging, with Aubrey de Grey
Mark Sackler: You wrote the book Ending Aging in 2008. You identified seven areas of cellular and intracellular damage that you think need to be reversed as the best process for reversing aging. In the nine years since you wrote that book, what has changed? Are we where you thought we'd be by now? Have there been any breakthroughs?
Aubrey de Grey: People often ask me, "When are you going to write a new book - when are you going to update Ending Aging?" It's not a priority right now. It could easily be presumed to be saying that it's not my priority simply because I haven't made much progress and there's not much to say. But it's just the opposite of that - there's been massive progress, but it's been pretty much exactly the progress that we were predicting in the book. So essentially the plan is the same 7 points. There's no problem number 8 or 9 that came along and had to be added. And furthermore, the solutions that we discussed in the book are still the same solutions. There's nothing that has come along that has made us have to revisit it and say, well, OK, the approach that we thought was going to be the right way to go is actually much harder than we had expected and therefore we need something else - none of that has happened. There have been some surprises, but they have all been good surprises in the form of innovative technologies - new discoveries that have allowed us to pursue the same approaches but more effectively and more rapidly than we otherwise thought.
Now there is one downside, though, which is, back then I started making predictions about the time frames of how long this will all take. And of course, I was always making a lot of caveats emphasizing that a prediction of time frames was very speculative for any pioneer in technology. However, the fact is we haven't hit the time frames I was saying that we would. But what's gone wrong is not the science, but something else. The answer is the money. The fact is that my predictions were always very strongly conditional on the ability to bring in funding that was sufficient so that the rate of progress would only be limited by the sheer difficulty of the technology, the actual science and practice. I believe we've been going along three times more slowly than that initial prediction simply because it's been so much more difficult than I had expected to attract sufficient funding.
Mark Sackler: What about using pharmaceuticals or supplements to slow the aging process - to buy more time before we reach SENS 1.0? There are several agents out there now. Metformin is about to go into human clinical trials, Rapamycin is in trials with dogs, and NAD+ supplements are all the rage right now. What's your take on all of this?
Aubrey de Grey: So I'm all for this work. I think that it's very valuable in helping people to stay healthy longer. However, there is a very important feature of all of these supplements which is very often swept under the carpet by the researchers and companies that are working on them. They're all hypothesized to work by calorie restriction memetics. In other words, drugs that trick the body into thinking it's not getting as many calories as it would like, even though it is getting them. So that's wonderful. Except that there's a huge catch, and it has been a totally incontrovertible message in the animal data for decades. It is a fairly scandalous thing that has been swept under the carpet. The problem is that different species respond by different degrees to this kind of restriction. Specifically, long-lived species respond less than a short-lived species. The world record for how much you can extend the life of a nematode worm that normally lives about three weeks is by a factor of five. But then if you go up and look at organisms that live a couple of years, like mice, you can only get a factor of one and a half. That's still very impressive but it's definitely not five. But unfortunately, this trend persists as you go higher up the chain.
For example, about 20 years ago you're in a very thorough and rigorous trial made with Labrador dogs, which normally live about 11 years, and on the whole, it resulted in only about a 10% increase in lifespan. And over the past 20 odd years, two groups in the US have performed extraordinarily expensive and time-consuming experiments of calorie restriction on monkeys, and depending on how you interpret that, it yielded maybe a couple of percent increase. So, the prognosis for humans is not terribly good. Now again I want to emphasize I'm fine with the fact that people are excited by these drugs, because they do seem to keep people healthy; they are protective, but it is critical not to make the extrapolation that they are the foundation to extending life - because in no way has that happened.
Mark Sackler: One of the hottest biotech topics lately has been genetic editing, and there have been at least two individuals who recently had genetic editing therapy performed on themselves. I wonder what you make of those efforts.
Aubrey de Grey: Well, first let me talk about gene targeting in general. CRISPR is a fantastic breakthrough. When I was talking at the beginning about the surprises that we'd had, that's probably the single biggest one - because the fact is that before it came along, there was very little that we could do to change genes. We had methods for gene targeting, for modifying the genome, but they were very laborious and expensive. Now as for self-experimentation one can look at it in a whole bunch of ways. First, one can be curmudgeonly about it and say, well okay, this is very unsafe. God knows what's going to happen if bad things happen if these people die as a result of that therapy; it is going to set back the whole field to a large degree. That's all true up to a point. But at the same time, we have to remember that self-experimentation is not new. It has a long and very distinguished history in biology. JBS Haldane, the distinguished and respected British biologist from the 1930s, was rather famous for doing things to himself that I certainly wouldn't dare to. Certainly, the scientific information that will come from this sort of experimentation effort is probably very limited, simply by the fact that it is a sample size of 1. But on the other hand, the high-profile news that arises and the fact that people are talking about what is happening and a discussion is actually occurring, has its own value. If people are not interested in something, it's very hard to get them to think about it, whereas if they are interested, even for an unusual and rather tangential reason, you can educate them.
Mark Sackler: Earlier this year I interviewed David Wood on his book The Abolition of Aging. In it he forecast that by 2040 there is a 50-50 chance of there being widely available affordable rejuvenation therapy. How do you feel about that forecast right now? Is it overly optimistic? Is it well within reach if there's enough money, or is it totally uncertain?
Aubrey de Grey: It's pretty much exactly the same as my prediction. That may not be a coincidence.
Senescent Cells are Large, which Suggests a Few Simpler Paths to Assays for Senescence Level in Human Subjects
The rise in number of senescent cells with age is one of the root causes of degenerative aging. Somatic cells become senescent when they reach the Hayflick limit on replication, or become damaged, or encounter a toxic environment. They cease replication, and either self-destruct or are destroyed by the immune system. Some small fraction of the countless cells that become senescent each and every day manage to evade destruction, however. They linger, in ever greater numbers with each passing year, and the potent mix of signal molecules they secrete contributes to many forms of tissue dysfunction and organ failure, ranging from fibrosis and loss of regenerative capacity to increased inflammation and loss of tissue elasticity.
Fortunately, we stand just a few years removed from of the clinical availability of therapies that can destroy some fraction of these cells. A few startup companies are working on senolytic treatments ranging from repurposed chemotherapeutic drugs to gene therapies to antibody therapies. Senolytic treatments that work in humans will literally produce rejuvenation to some degree, turning back one of the causes of aging. They don't even have to be expensive in the case of repurposed drug candidates, though these are unlikely to be as effective as the final results of further development efforts. Indeed, the adventurous can order and use some of these drug candidates even now, and experiment upon themselves, with very little outlay of funds. Caution is always recommended, of course.
Perhaps the most important objection to self-experimentation in the matter of the first legitimate rejuvenation therapies is that there is no readily available measure that will determine just how many senescent cells have been destroyed by a treatment. This is a challenge for formal human pilot trials as well. It means that secondary measures or expensive laboratory work are required, and in a basically healthy individual in middle age, it may well be the case that it is hard to separate out the effects of a crude but legitimate rejuvenation therapy from the noise. Aging has numerous distinct contributing causes, forms of cell and tissue damage that mingle to produce the initially slow decline. It is reasonable to expect it to be hard to see the short-term effect of removing 25% of senescent cells in, say, a 50-something individual who has yet to develop a severe manifestation of any of the age-related conditions most strongly linked to cellular senescence. On the other hand, maybe it will produce meaningful impact in cardiovascular measures such as blood pressure and pulse wave velocity. Without referencing a body of data that doesn't yet exist, it is hard to say which of these is the case.
Measures of senescent cell counts in a living individual would be inarguable, however, assuming they could be carried out without generating injury in the process of obtaining that information, as senescent cells are generated temporarily as a part of the response to wounding. Given such a metric, assessed before and after a treatment, one could definitively say whether or not the treatment achieved the intended result - and then all the uncertainty in secondary benefits achieved at any given age and health status will become more a matter of interesting further research than an outright roadblock. Unfortunately, we don't yet have a useful and broadly available tool to achieve this result. Possibilities include, say, some form of blood sample analysis that looks for the distinctive pattern of signal molecules produced by senescent cells. That is a reasonable research and development project for any group capable of proteomics-based analysis of blood, and perhaps there are people out there working away on it, quietly.
The authors of the open access paper below present an intriguing alternative, and one that might be more easily established and deployed. It is based on the observation that senescent cells are large, some twice as large as normal cells, or even larger. Thus these cells could be filtered from blood via the use of suitably sized fluid channel devices and then counted via flow cytometry, a task that is well-established and business as usual in the microfluidic device industry. Is it reasonable to expect that a higher burden of senescence throughout the body would be more or less accurately reflected by a larger number of senescent cells in the bloodstream? Possibly, but again, the work to prove and quantify all of that has yet to be accomplished. Still, the microfluidics approach to a senescence assay seems a very promising direction for further development.
Senescence chips for ultrahigh-throughput isolation and removal of senescent cells
Cellular senescence is a state of permanent cell cycle arrest due to genotoxic stresses and has been shown to be involved in organismal aging and tumorigenesis. Therefore, cellular senescence is an important biomarker for aging as well as genotoxic stresses such as ionizing radiation. However, the small number of senescent cells in biofluids such as whole blood limits their quick and sensitive detection. An effective isolation approach is highly desired for senescent-cell-based point-of-care diagnostics such as radiation biodosimetry. Moreover, recent animal studies have demonstrated the potential of therapeutic targeting of senescent cells for anti-aging and age-related diseases. Because pathways up- or downregulated in senescent cells, such as those involving p16, p21, and p53, also function at various degrees in their healthy counterparts throughout the tissues and organs, conventional methods by targeting these pathways with small molecules and protein drugs could result in side effects in humans. Alternatively, physical means by taking advantage of the cell size increase during cellular senescence provides an attractive novel approach to selectively remove senescent cells from their nonsenescent counterparts and other background cells.
Different microfluidic techniques have been developed for cell separation based on their physical properties. Among those techniques, filtration is the most promising approach to process undiluted whole blood for rare cell separation, and easily scaled up for high throughput. However, several challenges need to be overcome before this technique could be widely used. In dead-end flow filtration which has the flow direction perpendicular to the filter surface, a common issue is the clogging and saturation of the filter, resulting in low separation efficiency, sample purity, and device robustness. In some studies, a periodic reversed flow or fluidic oscillation was adopted to address clogging. To avoid cell damage and clogging issue, cross-flow filtration in microfluidics was developed with a flow direction parallel to the filter surface. Therefore, a shear force was generated to bring the bigger particles to the downstream instead of entering the filtration pores. However, to ensure effective cell separation in a parallel-flow configuration, the cross-flow filtration typically has a much longer channel with a throughput usually lower than 1 ml/hr. Despite the inherent low throughput for microfluidic devices, a higher throughput (e.g., more than 1 ml/min) is highly desired to process a large volume of whole blood samples. High throughput is particularly challenging for a continuous flow because of the difficulties in system integration and fluidic control for multiplexing on a microfluidic chip.
To overcome the clogging and cell damage issue while still achieve a high throughput and recovery rate, we developed a microdevice (senescence chip) for three-dimensional size sieving by taking advantages of both dead-end flow and cross-flow filtrations. A slanted micropillar array was fabricated with an inclination angle relative to the fluidic flow (between 0° to 90°). Therefore, the particles could not only be sieved efficiently but also experience a fluidic shear force to reduce clogging and preserve cell integrity. Moreover, the micropillars worked as cantilevers, which had only one end fixed. Their flexibility allowed small deformation when experiencing a fluidic pressure, creating hundreds of shutters in the vertical direction responsive to the flow rate. These shutters helped to release backpressure, reduce clogging, and dramatically improve separation throughput.
We utilized our senescence chip to isolate and analyze senescent cells in undiluted whole blood and mouse bone marrow. We chose mesenchymal stem cells (MSCs) because we have previously characterized their ionizing radiation-induced senescence progression. In this study, we utilized H2O2- and X-ray-induced senescent human MSCs spiked in whole blood, as a model biological system, to demonstrate the rapid separation and analysis of senescent cells using our senescence chip. The optimized device was then used for an animal study to isolate senescent cells from the bone marrow of mice undergone total body irradiation (TBI) of X-ray. To achieve ultrahigh-throughput removal of senescent cells for blood purification, we enlarged the chip dimensions and stacked multiple chips to build a multiplexed system. We demonstrated that our scaled-up senescent chip could achieve a parallel processing with a throughput up to 300 ml/hr.
BMP4-Generating Endothelial Cells Spur Regeneration of the Thymus
The research community is interested in regeneration and tissue engineering of the thymus, as this could in principle resolve one of the causes of age-related decline in immune system function. It is worth keeping an eye on present efforts, such as the one noted here, at an early stage of exploration. The thymus is where cells of the adaptive immune system mature, and is thus one of two important gating factors determining the pace at which new immune cells enter the body, ready for action. The other is the quality and activity of the hematopoietic stem cell population in the bone marrow, where immune cells are created.
The thymus is very active in childhood, but in early adulthood much of the specialized tissue - that hosts immune cells as they mature - atrophies to be replaced by fat. The remaining portion of that tissue fades away more slowly over a lifetime, and the pace at which new immune cells arrive fades with it. A sizable part of the failure of the immune system in later life derives from the ever slower pace at which immune cells are introduced. Malfunctioning, exhausted, and senescent immune cells accumulate. The immune system is eventually overwhelmed by the wear and tear of its duties, its component parts not replaced often enough. Restoring the active portions of the thymus to a youthful size has been shown to help in mice, and the hope is that it will do the same in humans.
The thymus, an organ in the lymphatic system, plays a critical role in immune function, producing the T cells essential to the immune response. The thymus, which gets smaller as we age, is highly sensitive to damage from stress and infection. And while it can recover from such insults - the process is known as endogenous thymic regeneration - more serious injury, for example, from chemotherapy or radiation, can extend recovery time considerably. That can result in an increased susceptibility to infections and even cancer relapse in patients while their T-cell count is low. "We don't really understand why the thymus shrinks as we get older, or how to make it bigger in patients where it would likely be helpful to have T cells be made."
That the thymus can regenerate itself has been known for nearly a century, but the mechanisms that control this process have not been widely studied. So researchers performed a transcriptome analysis of a section of the mouse thymus following damage from total body irradiation (TBI). They found a suite of genes that were significantly upregulated, including several already known to be involved in thymic function, as well as Bmp4. "We're really interested in understanding these processes of endogenous regeneration so that we may exploit them into clinically relevant and innovative strategies to boost thymic function."
The researchers treated mice with a BMP inhibitor starting one day before TBI to determine whether BMP signaling is necessary for endogenous regeneration. The treated mice had significantly worse recovery than controls, indicating BMP's importance in the process. In a related experiment, the researchers then injected endothelial cells into the bloodstreams of mice 72 hours after TBI, and found that doing so increased the number of thymic cells compared to controls. When they injected the cells directly into the thymus, 100-fold fewer endothelial cells were required to result in the same capacity for endogenous regeneration than when they injected them intravenously. This suggests that some endothelial cells from the bloodstream do make it to the thymus, they wrote in their report.
Therapies based on the research would be more likely to use isolated BMP4 than an endothelial cell line. Another future interesting direction would be whether this same pathway could be used in the aging thymus. In this scenario, or in damage associated with chronic conditions, perhaps boosting BMP4 activity would also drive thymic regeneration.
ZIPAR Staff Consider the Consequences of Engineering an End to Aging
The folk at ZIPAR, the Zurich Institute of Public Affairs Research, have academic futurist interests somewhat analogous to those of the Future of Humanity Institute (FHI) in the UK, though with more of a short-term horizon and consequent consideration of what some might consider fiddly, unimportant policy details. If the true legacy of the FHI and its network is to give rise to many peer organizations, where an increasing number of people put time into thinking seriously about the future of technological progress and radical enhancement of the human body and mind ... well, there are certainly worse legacies than that. It might be regarded as one facet of the later stages of the quiet, sweeping victory of the past generation of futurist and transhumanist thought, in which it becomes a field of policy academia, at the same time as the first transformative technologies are implemented in order to remove limits on the human condition.
Technology is intertwined with epistemic progress: technology is the practical application of knowledge and skills obtained through rational inquiry, and in turn, technology allows us to further our rational understanding of the world. However, technology is more than just the product of and the means to a more accurate and a more complete understanding of the world. Technology allows us to do things that are beyond the natural limits of our biology. For the most part, we do not think much about this property of technology. When we ride a bicycle, for example, we are using a piece of technology that allows us to go from A to B in a much more efficient way than by going on foot.
Sometimes, however, transcending the limits of human biology via technology does not only raise eyebrows, but widespread concerns. Most people intuitively accept most ways in which technology changes or completely removes biological limits. Some biological limits, however, seem to be off-limits, so to speak. One such limit is the finite natural lifespan of humans: death is a natural part of life, and trying to end natural death might seem outlandish. Our visceral response to the idea of ending death, of course, is little more than status quo bias coupled with a variant of the is-ought-fallacy. Whether something is morally desirable is not determined by whether it is the status quo.
Ending natural biological death has a number of benefits that go beyond the intuitive idea that not existing feels weird. We humans are systematically irrational in many domains, due to our cognitive biases. One such domain is the assessment of risks. One source of our biased risk perception is our natural life cycle. Things that will happen some time in the future matter less to us than things that will happen immediately, simply because there is uncertainty about the future. If we end natural biological death, then we are radically changing our future prospect. We are not trying to imagine a world in which we do not exist anymore, but we are instead thinking about a future world that is some time off, but that we will be part of nonetheless. Such a radical shift in perspective might help alleviate some problems of the present bias.
Our biased time-preferences are not only present in the domain of risk perception, but also in the ostensibly simple domain of planning ahead. Ending natural biological death through rejuvenation could have a positive impact on our long-term planning capabilities. From an individual, micro-level perspective, knowing that the long-term future (in terms of traditional human lifespan) is not some uncertain world that one might not even live to see, but instead a state of the world that will come about in due time, might nudge individuals towards automatically correcting some of their planning biases. After all, if I know that 50 years into the future, I will still be physically the same as I am now, thanks to rejuvenation, then I might think more carefully about the decisions I make today that might affect me in the future.
Humans are capable of remarkable rationality, both in the sense of epistemic as well as instrumental rationality. Unfortunately, all sorts of "afflictions" prevent us from realizing our rational potential to the fullest. There are two ways in which an end to natural death could cumulatively increase individual rationality levels. First, active epistemic engagement by individuals would have a positive effect. Increasing human lifespan (potentially practically indefinitely) would mean that humans would experience changes in the world of the kind that was previously observable only on an intergenerational level. The second way in which the end of natural death might result in cumulatively higher rationality is accidental experience. The longer a person lives, the more probable it is that some strongly held belief will be accidentally challenged. Accidental contact with members of the outgroup can challenge our beliefs and reduce intergroup bias.
Most people fear death, or at least feel uneasy about death. Fear of death is a unique feeling that is, at once, both perfectly understandable and irrational. Ending natural biological death would mean removing death dread, either completely or to a large degree. Fear of death is probably one of the most unpleasant negative feelings because, contrary to almost all other causes of negative feelings, we cannot do anything about death (yet). Death dread is an unnecessary, cruel burden of nature; humankind loses nothing by getting rid of it.
But our lives do not consist only of the search for ways of higher-order progress. In our lives, there are many things that we simply enjoy. Enjoying things means that, every day and mostly without being fully aware of it, we experience some form or another of pleasure. Experiencing pleasure is something we value on an individual level, but it is also a general moral goal. Ending natural biological death could increase the amount of pleasure people experience. One reason why is obvious: The longer a person lives, the more pleasureable experiences can she or he have. But there is also a second reason why doing away with natural death would have a positive impact on pleasure: Technological and social progress. One of the most notable effects of technological and social progress is that it makes human life more pleasurable, in all kinds of ways.
Creating as much pleasure for as many people is a classical utilitarian goal, but pleasure is only one side of the utilitarian medal. The other, and perhaps more important moral aspect of existence is suffering. All things being equal, we should reduce suffering for as many people as much as possible. Ending natural death would reduce would almost certainly have a great positive impact on reducing suffering. Human morbidity is compressed towards later stages in life. Ending natural death through rejuvenation would mean avoiding the stage of compressed morbidity altogether, and with it, avoiding a lot of suffering associated with afflictions that are likely in later life stages. If we assume diagnostic and therapeutic medical treatments to advance in the future, then the overall suffering caused by disease will gradually approach zero. This means that people who live beyond their natural biological age limit will experience less and less disease-induced suffering the longer they live.
In conclusion, death is a natural part of human existence, but human progress is essentially a story of overcoming undesirable natural limits. In the near future, technological progress might make it possible to stop natural biological death. Should humankind embrace such technology? Yes: Even though such technology would not be without risks, the risks are almost certainly manageable. The benefits of ending natural death, on the other hand, are immense. Death is an obstacle that is slowing down human progress. If we remove that obstacle, humankind could increase the speed of both its moral and its epistemic progress.
An Attempt at Using Protein Levels Rather than Epigenetic Patterns to Build a Biomarker of Aging
The current best candidates for a sufficiently robust biomarker of aging are based on patterns of DNA methylation, epigenetic markers that control the pace at which specific proteins are produced, and which are constantly shifting in response to circumstances. The best of these epigenetic clocks have degrees of error in assessed age that are five years or less, depending on implementation. The researchers here have chosen to investigate patterns of protein levels in blood rather than epigenetic markers, in part driven by economic considerations, as the needed tools of biotechnology are more mature and less expensive. They use modern computational techniques to try to build useful biomarker algorithms through an analysis of raw data obtained from large numbers of people at various ages. Their efforts result in a degree of error of around six years, which might be taken as encouraging; it may well be possible to do better via this method.
To perform this study, we trained a series of deep neural networks on anonymized blood tests for patients from three distinct ethnic populations: Korean, Canadian, and Eastern European. We compared the predictive accuracy of our deep learning models first when trained using population-specific data, and then when using a combined and ethnically-diverse dataset that includes patients from all three patient populations. We used the same feature space of 20 blood biochemistry markers, cell counts, and sex to train three separate deep networks on three specific ethnic populations.
We present several novel hematological aging clocks. The best-performing predictor achieved a mean absolute error (MAE) of 5.94 years having greater predictive accuracy than the best-performing predictor of our previously-reported aging clock (which achieved an MAE of 6.07 years), despite being trained on a narrower feature space (21 compared to 41 features). These results are in line with the hypothesis that ethnically-diverse aging clocks have the potential to predict chronological age and quantify biological age with greater accuracy than generic aging clocks. Furthermore, they have a greater capacity to account for the confounding effect of ethnic, geographic, behavioral and environmental factors upon the prediction of chronological age and the measurement of biological age.
Albumin, glucose, urea, and hemoglobin were among the most important blood biochemistry parameters for all three population-specific predictors. Albumin is the most prevalent protein in blood and its primary function is the regulation of oncotic pressure, which is critical for transcapillary fluid dynamics, and hypoalbuminemia is often associated with malnutrition, liver disease, injury, chronic inflammation and the aging process. Blood glucose levels, on the contrary, tend to increase with age, and glucose is able to modify proteins via irreversible glycosylation, a feature that is directly associated with the aging process. Levels of serum urea also increase with age, which is associated with age-related decrease in muscle mass. Age-related decreases in hemoglobin is common in the elderly, a condition that increases the risk of cardiovascular disease, cognitive decline and an overall decline in quality of life.
Our hematological clock is consistent with what is already known about the biology and pathophysiology of aging. While the blood parameters are not accurate biomarkers of aging by themselves, when analyzed in combination they can be used to reasonably accurately predict chronological and biological age. Deep learning based hematological aging clocks, even when trained on a limited feature space, demonstrate reasonably high accuracy in predicting chronological age.
Quercetin is Probably Not a Useful Senolytic
Senolytic compounds are those that preferentially destroy senescent cells. Since these cells are one of the root causes of aging, there is considerable interest in finding and then quantifying the effectiveness of senolytic compounds. The known and alleged senolytics vary widely in effectiveness and quality of evidence, and quercetin is one of the more dubious examples. I don't think that anyone expects quercetin, on its own, to have a useful level of impact on senescent cells and their contribution to degenerative aging. The study here comes to the plausible conclusion that quercetin really can't achieve that goal. Yes, it is true that the 2015 mouse study of the chemotherapeutic dasatinib and quercetin demonstrated that the two together cleared more senescent cells than dasatinib alone, but synergy with other compounds is a very different story from unilateral effects. Quercetin is a widely used and extensively tested supplement compound. Any significant effect on health resulting from quercetin alone would likely have been discovered many years ago.
Previously, quercetin was reported to be a senolytic in irradiation-induced senescent human umbilical vein endothelial cells (HUVECs). HUVECs are derived from the umbilical cord of newborn babies, and for a long time were the only model of primary human endothelial cells (EC); however, these cells are not the best model of diseases associated with human arterial aging. HUVECs have been shown to differ substantially from primary endothelial cells derived from adult human vasculature. In the current study, we investigated whether quercetin is a senolytic in adult EC, and evaluated whether quercetin 3-D-galactoside (Q3G; hyperoside) would be a more selective senolytic.
Quercetin's low therapeutic/toxic ratio in the HUVEC study raised the possibility that quercetin could significantly injure non-senescent cells. It was unclear whether the proliferation of non-senescent cells could be compensating for some of the quercetin-mediated cell death, thus masking its toxicity to the young cells at the lower concentrations found to be selectively cytotoxic to senescent cells. We used adult human coronary artery endothelial cells (HCAEC), which are microvascular cells, as a relevant model, and generated two groups of cells from them to better understand the effect of quercetin: EP (early passage; young) and SEN (senescent), as a model of an aging tissue.
Our key findings are that quercetin at a concentration that reduced SEN EC also caused significant EP EC cell death, and that there was no evidence of senescent cell-specific cell death mediated by quercetin. Thus, quercetin is not a selective senolytic in adult human arterial endothelial cells, where both EP and SEN cells responded similarly to quercetin's toxicity.
To circumvent quercetin's toxicity on healthy, non-senescent cells, we investigated Q3G, a derivative of quercetin with limited toxicity to endothelial cells, which is processed by senescence-associated beta-galactosidase (SABG) enriched in senescent cells to release quercetin in situ. Q3G could act as a selective prodrug in senescent cells. However, Q3G had no significant toxicity to either EP or SEN EC. The lack of Q3G's toxicity in the current study may be due to Q3G being unable to enter the beta-galactosidase-rich lysosomes, or alternatively, Q3G being able to translocate to the lysosomes to release quercetin, which is further processed into an inert compound.
An Example of the Need for Research and Development Investment in Cryonics
Cryonics is a field that requires commercial success of some form for further expansion, such as in the reversible vitrification of organs, not least because either that or wealthier patrons than presently exist will be needed as a source of significant funding to improve current methodologies of preservation. The recent report from Alcor noted here illustrates the well-understood need for this sort of technical improvement. Alcor presents comparatively unfiltered reports on cryopreservations, where patients agree to it, and the staff and patients should be commended for this. Such reports are important to the quality of an industry, and open organizations are certainly better than closed ones.
It is arguably the case that the biggest hurdle today when it comes to obtaining an optimal cryopreservation is the illegality of assisted euthanasia, a state of affairs that forces the industry into the form of a standby and emergency response service. That makes it both expensive and challenging to achieve a high-quality cryopreservation immediately after clinical death, as a sizable fraction of deaths in late life are unexpected in their timing. When euthanasia becomes more broadly legal and accepted, however, it will then be the case that technical limitations such as access to blood vessels in stroke victims will become the biggest immediate hurdle. It is easy to envisage ways around that problem, and the more sophisticated apparatus, the better tools to get at the blood vessels of the brain at multiple points so as to introduce cryoprotectant in a controlled way during cooling. While cryonics remains a non-profit and comparatively resource poor industry, this sort of technology remains out of reach - which is why some form of commercial success is needed, to enable bootstrapping to the next level of operation.
As the example here illustrates, even when the patient's terminal decline is slow enough to organize a preservation immediately following clinical death, there are forms of death, such as those resulting from stroke, in which modern methods of vitrification cannot be used because the state of the art in the industry isn't yet advanced enough to work around significant blood vessel blockage in the brain in a cost-effective way. Vitrification requires introduction of cryoprotectant into the vascular system of the brain, and that cannot be done haphazardly. So by commonplace bad luck, the patient obtains a preservation that will introduce significant ice crystal formation and consequent tissue damage, rather than the vitrification intended to minimize that issue. That adds to the bad luck of having suffered earlier damage to the brain due to stroke and its consequences. These are all challenges that could be addressed giving meaningful investment into cryonics.
Alex Arevalo, a public, neuro member, was pronounced on October 20, 2017 in Tucson, Arizona and became Alcor's 153rd patient the same day. Alcor received an emergency text on October 20th just before 10:00 (all times are Mountain Time in 24-hour format). We were alerted that Alex Arevalo was suffering from a stroke. He had a previous stroke in January of 2017. Contact was made with Peggy, his wife. She stated he was unable to speak or to move his right hand, and suffered from right-sided facial droop. They were currently located in Las Cruces, NM and he was being transported to the closest stroke center in Tucson, AZ.
Josh Lado, Director of Medical Response, was traveling to Tucson that morning on personal business. He traveled to the hospital to which Alex had been flown and made contact with the attending physician in the Emergency Department. She stated that they had performed a CT scan and she didn't believe that the patient's brain was receiving any significant blood flow. The patient had suffered a hemorrhagic stroke at the brain stem. Josh called Alcor's Chief Medical Advisor, Dr. Harris to inform him and determine the best course of action.
Dr. Harris and Josh agreed that the patient should be taken off ventilation immediately to allow legal death by cardiopulmonary criteria to occur. He was extubated at 13:50. Josh called Dr. Harris and the decision was made not to perform any cryoprotectant perfusion once the patient was at Alcor and to perform a straight freeze. This decision was made because of the inability to perfuse the brain due to the hemorrhagic stroke and associated warm ischemia that had already occurred, and the chance that added pressure would cause more damage inside the patient's brain. Alex's vital signs significantly changed at 18:57 as his heart rate decreased, rhythm changes occurred, blood pressure spiked, and oxygen levels dropped significantly. Legal death was declared at 19:18. Alex had ice placed around the head and neck and preparations began for transport. Once paperwork was finished, hospital staff helped move the patient to the transport vehicle and assisted in moving him into the Ziegler case.
Four bags of ice were placed in the case to precool the metal box. 35 pounds of ice was added around his entire body. This was to ensure the ice wouldn't melt by the first stop just outside of Tucson. The patient left the hospital at 20:11 to head back to Alcor. The first stop to check for ice was at 20:36, and five pounds of ice was added. The second stop was at 21:33 and 5 more pounds were added. The reason for making two stops for ice was the limited space around the head for ice, between the wadded body bag corners and the case having 45 degree corners at head and foot. There was plenty of ice but Josh wanted to ensure continued cooling. The patient arrived at Alcor just after 22:30. Surgery was performed for neuro separation and cool down began right away.
Delivering Microglia-Like Cells to the Brain to Break Down Amyloid-β
The future of cell therapies might prove to be one in which transplants are largely done away with. Cell engineers will instead issue a carefully controlled set of signals that cause the body to generate the desired additional population of cells, move those cells to where they are needed, and then put them to work in a specific way. We stand a long way removed from the full realization of this sort of treatment, not least because the signaling environment of most tissues is still largely terra incognita when it comes to the fine details, but the research noted here is certainly a start along that road.
For brain microglia struggling to keep amyloid plaques under control, help could be on the way. Researchers have identified an antibody that triggers mouse bone marrow myeloid progenitors to become phagocytic microglia-like cells, which then make their way to the brain. In a mouse model of Alzheimer's disease (AD), the cells clustered around amyloid deposits and reduced plaque load.
The findings grew out of a problem seen with stem-cell therapies - it's not enough to generate the desired type of cell; the cells also must be directed to where they are needed. "After embryogenesis, the 'go there' part is shut down. Controlling migration is the other half of stem-cell therapy." To address that, researchers devised a screen for antibodies that induce stem cells to not only differentiate but also migrate to different tissues. After expressing antibodies on bone-marrow stem cells, researchers put those cells in mice and looked for the ones that gained the ability to migrate to the brain or other tissues. "In a normal selection, you look at a cell population and find something that's different. In this migration-based selection, the cells self-purify because they run away from the bone marrow, and take up residence in other tissues."
Researchers started with a lentivirus expression library comprising 100 million different single-chain antibody genes. They infected freshly isolated mouse bone-marrow cells with the library, then transplanted the entire batch of infected cells into mice whose own bone marrow had been destroyed by whole-body irradiation. After a week, they used PCR to detect traces of the antibody genes in different tissues. Of 60 different genes detected, they found one, dubbed B1, six times in brain tissue from different mice, and never in spleen, liver, or heart.
To ask if the microglia-like cells attack amyloid in vivo, the researchers repeated their transplantation experiments using APP/PS1 mice. They infused B1-transduced bone marrow cells into irradiated eight-week-old animals, and then waited. After six months, the B1 mice harbored approximately 60 percent less amyloid in their brains than animals transplanted with control bone marrow. The animals also had more microglia and fewer astrocytes than irradiated controls. Does B1 treatment induce bona fide microglia and if so, what type? This is difficult to evaluate. "I don't think these cells are the real deal, but I don't care. If, as claimed in the study, this antibody induces a type of cell that can migrate to plaque in non-irradiated mice, that's important. If this is associated with plaque removal, that's huge. Whether the cells become microglia is not as important."
Torin1 as an Example of the Search for Better Rapalogs, with a Focus on Autophagy
A sizable portion of the research community interested in intervening in the aging process searches for ways to mimic naturally occurring stress responses, those linked to a slowing of aging in animals. Much of this research in some way involves TOR, the target of rapamycin, and attempts to improve upon rapamycin as a drug candidate to inhibit TOR. TOR is connected to the regulation of autophagy, a cellular housekeeping process known to influence the pace of aging, but also to many other areas of cellular biochemistry relevant to aging. The relevant mechanisms and networks of protein interactions are only partially mapped, and are very complex - progress on that front is slow and expensive.
I point out the open access paper here as an illustrative example, representative of the work of many other scientific groups whose members aim to find and evaluate TOR inhibitors, also known as rapalogs, in search of drug candidates that are better than rapamyin. Better or not, however, it is still the case that this sort of thing is marginal in the grand scheme of what is possible - look at the survival curves in the paper to see how small the effect is in flies, and bear in mind that the effect size for stress response mechanisms diminishes greatly as species life span increases, where the data exists to compare directly. When it comes to what can be gained in terms of increased human life span, modestly slowing aging by activating cellular stress responses compares very unfavorably with rejuvenation strategies based on periodic repair of the molecular damage that causes aging.
Down regulation of the protein kinase TOR is reported to increase lifespan. TOR is highly conserved across eukaryotes and controls several fundamental cellular functions including autophagy - an important and highly conserved cellular repair mechanism. TOR is a major regulator of cellular growth and proliferation and is comprised of two differentially regulated protein complexes TOR complex 1 (TORC1) and TOR complex 2 (TORC2). TORC1 and 2 have distinct substrate specificities and are differentially sensitive to the TOR inhibitor rapamycin. TORC1 promotes anabolism and inhibits catabolism by blocking autophagy. TORC2 is known to be insensitive to rapamycin. Its role in protein synthesis isn't yet clear, though it plays roles in many cellular processes via the AGC kinases and is implicated in keratinocyte survival and cancer development.
The effects of TOR on autophagy are of interest in the context of ageing. It is known for example, that autophagy is naturally down-regulated as a result of normal ageing. The function of autophagy is to repair cellular damage, leading to the suggestion that manipulations that activate autophagy might increase lifespan by maintaining damage surveillance and increasing cellular repair. Consistent with this, over-expression of specific autophagy genes has been shown to extend lifespan in yeast, flies, and human cells. In general, manipulations involving changes to autophagy or autophagy genes are increasingly being reported to be associated with lifespan. Linking the two processes, it has been shown that the specific inhibition of TOR, which in turn activates autophagy, results in extension of lifespan in various species.
The TOR pathway can be inhibited, and hence autophagy activated, by inactivating TORC1 through treatment of cells with rapamycin or via nitrogen starvation. This increase in lifespan due to inhibition of TOR could potentially be via TOR's effects on protein synthesis. However, research on C. elegans suggests a more direct role of autophagy in the modulation of longevity, because inactivating autophagy genes specifically prevents the inhibition of TOR activity from extending lifespan. This finding suggests that the TOR pathway and autophagy act via the same signalling pathway to influence lifespan. However, it should also be noted that inhibition of TOR leads to decreased translation as well as increased autophagy, hence it can be important to distinguish whether either or both pathways are most associated with lifespan effects.
Torin1 is a well-established activator of autophagy via inhibition of the TOR pathway, which inhibits TOR with a higher degree of selectivity than other previously used pharmacological activators, e.g. rapamycin. Part of the mechanism of action of Torin1 is reported to be to suppress the rapamycin-resistant functions of TORC1 that are necessary to reduce autophagy. In addition, unlike rapamycin, Torin1 is reported to inhibit kinase function in both TORC1 and TORC2 complexes potentially giving it greater effectiveness. Torin1 inhibits cell growth and proliferation to a much greater degree than rapamycin and may represent a more effective and specific inhibitor.
In this study we initiated an investigation into the effects on lifespan and reproductive success of Torin1 supplied via the diet, in once-mated and continually mated D. melanogaster females, and on the lifespan of once-mated males. The main finding was that the addition of Torin1 to the diet activated autophagy and led to significant lifespan extension in both sexes. Elevated egg production was observed in females fed Torin1, but overall this did not result in higher overall fertility, owing to higher egg infertility in these females. Hence, there was no evidence for a trade-off between longevity and total fecundity, or between longevity and fertility. Elevated reproduction can lead to damage, which may result in reduced lifespan. Our hypothesis is that the activation of autophagy by dietary administration of Torin1 repairs damage caused by elevated reproduction, potentially minimising trade-offs between lifespan and reproductive rate.
Evidence for mTOR to be Involved in Vascular Aging and thus Vascular Dementia
Research into mTOR and aging is becoming quite diverse. Researchers here present evidence for mTOR to be involved in the aging of the vasculature, and thus also in the development of vascular dementia. One of the noteworthy aspects of aging is the declining ability of the vascular system to deliver sufficient nutrients and oxygen to cells, and this is considered important in the decline of both brain and muscles, two of the more energy-hungry tissue types.
The research here is a good example of the way in which most researchers restrict their scope to relationships between areas of protein machinery that are very close to the disease state, without looking back down the chain of cause and consequence towards any sort of root cause. Detailed changes in proteins and their interactions are cataloged, but there is next to no consideration of why these changes in levels and interactions of proteins take place in aging. Instead of working further backwards - or better, starting with the known root causes of aging and working forwards - the impetus is to intervene in order to adjust the protein interactions of the disease state in some way.
At the SENS Research Foundation, the home of interventions that target root causes in aging, this tendency in the scientific community is known as "messing with metabolism." It fails as a strategy precisely because it doesn't look to the root causes, but instead becomes distracted into mapping and tinkering with the details of the immensely complicated dysfunctional state of cellular biochemistry exhibited in age-related conditions. If root causes are left alone to fester and continue to produce any number of downstream issues, then there is very little that can be usefully done to cure such a condition - no amount of tinkering will help greatly.
Brain vascular dysfunction is involved in the etiology of dementias. Cerebrovascular dysfunction is one of the earliest events in these dementias, best exemplified by diminished cerebral blood flow (CBF). A recent study suggested that vascular dysfunction indicated by decreased CBF may be the first abnormal biomarker in Alzheimer's disease (AD) progression, as well as the one that shows the largest magnitude of change. A significant barrier to effective treatments for AD, which are currently unavailable, is that we still do not sufficiently understand the mechanisms that drive its onset and progression. While the neuronal contributions to AD pathogenesis have been extensively studied, cerebrovascular mechanisms of AD, which show substantial overlap with those of vascular cognitive impairment and dementia (VCID), are only partially understood.
The mechanistic/mammalian target of rapamycin (mTOR) may be a critical effector of cerebrovascular dysfunction in AD and potentially other dementias. mTOR is a major signaling hub that integrates nutrient/growth factor availability with cellular metabolism. mTOR also regulates the rate of aging across phyla, including invertebrates and mammals. Rapamycin, an mTOR inhibitor, is the first drug that has been experimentally proven to slow down the rate of aging in mice. Work from our lab and others has identified mTOR as a major regulator of cerebrovascular damage and dysfunction in AD. While mTOR has a critical role in the regulation of cellular metabolism through actions at multiple signaling pathways, some mTOR-dependent mechanisms are uniquely specific to the regulation of cerebrovascular function.
Underlying the CBF reductions observed in AD are decreases in regional and global vascular density. mTOR drives cerebromicrovascular density loss, leading to profound CBF deficits, by decreasing microvascular nitric oxide (NO) bioavailability in brains of mice modeling AD through inhibition of NO synthase (NOS) activity. Therefore, mTOR attenuation with rapamycin induces endothelium-dependent cortical vasodilation via NO release. In agreement with this notion, prior in vitro studies showed that mTOR inhibits endothelial NOS (eNOS) phosphorylation and activation and NO-dependent arterial vasodilation.
Aβ, causally implicated in AD, is generated in the brain by cleavage of the amyloid precursor protein (APP) in association with neuronal activation. Aβ is released at synaptic sites into the interstitial fluid. Several physiological mechanisms act to prevent Aβ accumulation, but the largest contributor is transvascular Aβ clearance, as over 85% of Aβ is continuously cleared out of the brain through the blood-brain barrier (BBB). Consistent with a critical role of microvascular integrity and function in Aβ removal from the brain, systemic mTOR inhibition reduces Aβ levels in the brain and improves cognitive function in mouse models of AD. In these AD models, mTOR promotes the accumulation of Aβ in the brain by inhibiting autophagy and by decreasing Aβ clearance as a result of decreased vascular density and reduced CBF.
The BBB is formed by a monolayer of vascular endothelial cells that line the brain microvasculature and dynamically regulate the exchange of molecules. Studies indicate that BBB breakdown is one of the earliest events in the pathogenesis of AD. It was found that mTOR attenuation reduces or prevents BBB breakdown in several models of age-associated neurological disorders, suggesting a broad role of mTOR in BBB dysfunction in age-related brain disease states. The exact mechanisms by which mTOR promotes BBB breakdown, however, have not yet been sufficiently studied.
Rapid increases in blood flow to areas of the brain with high neuronal activity are required to maintain cellular homeostasis and function. This is accomplished through neurovascular coupling, a homeostatic response mediated by complex intercellular signaling events. Significant neurovascular coupling deficits are observed in patients with AD. NO production via activation of the neuronal form of NOS (nNOS) contributes significantly to the neurovascular coupling response by inducing local vasodilation in response to neuronal activation. Dysfunctional neurovascular coupling in mouse models has been reported to occur both from reduced neuronal NO production as well as from a diminished CBF response to otherwise unimpaired NO signaling. Since mTOR is a key driver of cerebrovascular damage and disintegration in several mouse models of AD, it is reasonable to hypothesize that mTOR contributes, at least indirectly, to neurovascular coupling deficits in these models. Very little is known at present, however, about the role of mTOR in the regulation of neurovascular coupling.
Suggesting that Only Minimal Loss of Synapses Occurs in Alzheimer's Disease
There are signs from past years to suggest that Alzheimer's disease is a reversible condition, at least in its earlier stages. In other words, that there is little loss of the structures holding the data of the mind, and the condition degrades the operation of the mind, not its underpinnings. The consensus, however, is that this stops being the case further into the progression of the disease, and significant losses do in fact occur. The researchers here disagree with that consensus, providing data to suggest that even in later stages the condition is not destroying significant numbers of synapses. This will definitely require further supporting evidence before it can be taken at face value, particularly since it is really only assessing the presence of key synaptic proteins in tissue samples, rather than any more in-depth analysis of structure and function.
Frequently encountered in the elderly, Alzheimer's is considered a neurodegenerative disease, which means that it is accompanied by a significant, progressive loss of neurons and their nerve endings, or synapses. A new study now challenges this view. Conducted among more than 170 subjects at various stages of Alzheimer's disease, the study has shown instead that the disease is accompanied by a minor decline in neuronal and synaptic markers. "Much to our surprise, in studying the fate of eight neuronal and synaptic markers in our subjects' prefrontal cortices, we only observed very minor neuronal and synaptic losses. Our study therefore suggests that, contrary to what was believed, neuronal and synaptic loss is relatively limited in Alzheimer's disease. This is a radical change in thinking."
The scientists also attempted to correlate all these minor synaptic losses with the subjects' level of dementia. Their results show that the declines in synaptic biomarkers had little impact on the participants' cognitive skills. The study implicitly suggests that dementia is associated with a synaptic dysfunction rather than the disappearance of synapses from the patient's cortex. Identifying this dysfunction could lead to the development of effective treatments for this disease. "Until now, therapeutic interventions have been aimed at slowing synaptic destruction. Based on our study, we are going to have to change our therapeutic approach."
The Prospect of Filtering Harmful Factors from Old Blood
The Life Extension Advocacy Foundation volunteers here interview Irina and Michael Conboy, two of the more influential scientists involved in parabiosis research. When the circulatory systems of an old mouse and a young mouse are connected, the older partner shows some reversal of measures of degenerative aging, while the younger partner shows some acceleration of similar measures of degenerative aging. The Conboys have of late produced evidence to show that this is based on the presence of harmful factors in old blood, where parabiosis dilutes harmful factors in the old mouse but also passes them over to the young mouse. There is similar evidence for beneficial factors in young blood passing in the opposite direction, however.
All of this data raises the possibility of somehow filtering out the harmful factors if they can be reliably identified. While numerous forms of blood filtration equipment exist today, it seems unlikely to me that being hooked up to a suitably adapted variant for a short time would provide lasting benefits - though it could certainly be used in studies to settle debates over the degree to which specific factors are involved or important. Harmful factors are, after all, generated on an ongoing basis by cells that are damaged or are reacting to the damage of aging. To produce useful results, filtering would have to be permanently in place, such as via an implant of some sort, or enhancement to the kidneys, or pharmaceuticals that inhibit harmful factors, and none of these options seem likely to appear immediately - all would require significant development. Even with that development, such an approach is not actually addressing the causes of the issue, but rather tries to patch over just a thin portion of it.
For the sake of those new to the topic, what is it in young blood and aged blood that affects aging?
Numerous changes in the levels of proteins that together regulate cell and tissue metabolism throughout the body. We wondered why almost every tissue and organ in the body age together and at a similar rate, and from the parabiosis and blood exchange work now think that young blood has several positive factors, and old blood accumulates several negative, "pro-aging" factors. We have published on improved liver regeneration, reduced fibrosis and adiposity by transfusion of old mice with young blood, but these are genetically matched animals, and in people, we do not have our own identical but much younger twins.
How do you propose to balance the cocktail of factors in aged blood to promote a youthful tissue environment?
We are working on the NextGen blood apheresis devices to accomplish this. We are collaborating with Dr. Dobri Kiprov, who is a practicing blood apheresis physician with 35 years of experience, and he is interested in repositioning this treatment for alleviating age-related illnesses.
Do you think a small molecule approach is a viable and, more importantly, a logistically practical approach to calibrate all these factors compared to filtering aged blood?
Yes, it is a very feasible alternative to the NextGen apheresis that we are working and publishing on.
Even if we can "scrub" aged blood clean, is it likely to have a long-lasting effect, or would the factors reach pro-aging levels fairly quickly?
That needs to be established experimentally, but due to the many feedback loops at the levels of proteins, genes and epigenetics, the acquired youthful state might persist.
Ultimately, could a wearable or an implanted device that constantly filters the blood be the solution to these quickly accumulating factors?
Maybe, but the first step of a day at a NextGen apheresis clinic once every few months might be more realistic.
What do you think it will take for the government to fully support the push to develop rejuvenation biotechnology?
Clear understanding of the current progress and separating the real science from snake oil is very important for guiding funding toward realistic clinical translation and away from the myth and hype.