Fight Aging!

First generation stem cell therapies involve sourcing immune privileged cells from sources such as umbilical cord blood, or a patient's own cells from fat tissue or similar, expanding the cells in culture, and then injecting them. Only minimal modifications are permitted to cells prior to transplantation in the US, before it would be classed as a therapy that must go through the IND process with the FDA for specific approval. Outside the US, in the medical tourism market, a range of approaches are undertaken with the goal of altering cultured cell behavior to improve patient outcomes. Unfortunately very little of this is backed by published human trial data.

This class of cell therapy produces little to no engraftment of the transplanted cells. Benefits result from the signals generated by the transplanted cells in the short time before they die. The primary outcome is a reduction in inflammatory signaling, dampening the chronic inflammation associated with aging and disease, with some hope of improved tissue maintenance and regeneration. Beneficial outcomes beyond a reduction in inflammation have proven to be quite unreliable, however.

Given that signaling is the mechanism, and that a sizable fraction of molecular traffic between cells is carried in extracellular vesicles such as exosomes, researchers and clinicians have increasingly focused on harvesting these vesicles as a basis for therapy. It is much easier (and thus cheaper) to store, transport, and use exosomes than to store, transport, and use cells. Based on the evidence to date, the outcomes are broadly similar.

Mechanism of Action of Mesenchymal Stem Cell-Derived Exosomes in the Intervertebral Disc Degeneration Treatment and Bone Repair and Regeneration

Exosomes are bilayered extracellular functional vesicles released by different cells with a diameter ranging between 40-120 nm. Exosomes carry out their functions by fusing with cell membranes or binding membrane proteins of the recipient cells. They contain functional proteins, nucleic acids (mRNA, miRNA, lncRNA, etc.) and lipids, and are carriers of intercellular communication between donor and recipient cells. Exosomes originate from a wide range of sources, and almost all cells can secrete exosomes. The exosomes secreted under normal and pathological conditions are different, even for the same cells.

Currently, exosomes are widely viewed as effective therapeutic components derived from mesenchymal stem cells (MSCs), and the secretion of exosomes is an important way for MSCs to promote the repair of surrounding tissue injuries. There is ongoing research into the benefits of therapy with MSC-Exos for IDD, as well as bone defects and injuries. The core underlying pathophysiologic mechanism of intervertebral disc degeneration (IDD) are abnormalities and a reduced number of nucleus pulposus cells (NPCs). The functional substance in MSC-Exos can regulate the cell metabolism and function by transferring to NPCs, endplate chondrocytes and annulus fibrosus cells, thus inhibiting IDD. Additionally, MSC-Exos also showed great therapeutic potential in terms of repair in bone defects and injuries via promoting osteogenic differentiation and angiogenesis and regulating the immune response, and similar results have been illustrated with respect to its therapeutic and preventive effects against cartilage injuries and osteoporosis.

Furthermore, the application of novel biomaterials such as hydrogels could prolong the duration of exosomes at the bone injury site and maintain the function and stability of intracapsular proteins and miRNA. In order to enable MSCs to play a better role in repairing tissue injury, studies should continue the exploration of new methods to promote the delivery of bioactive substances in exosomes more efficient and novel biomaterials that can maintain the physiological state of MSC-Exos.

Fibrosis is a malfunction of tissue maintenance, in which excessive amounts of extracellular matrix structure are created, forming scar-like features that disrupt normal tissue function. Fibrosis is a feature of aging and can rise to the level of life-threatening issue in organs such as the lung, liver, kidneys, and heart. This is particularly the case because there are no truly effective therapies to treat fibrosis; it is an inexorable condition that leads towards organ failure. Progress towards the reversal of fibrosis has been slow, unfortunately, despite the comparatively recent discovery that senescent cells appear to drive fibrosis in many organs, including the heart.

Cardiac fibrosis is a common feature of acute myocardial infarction (MI) and various other chronic diseases, such as hypertension, diabetes mellitus, and chronic kidney disease. Numerous studies emphasized that the severity of cardiac fibrosis correlates with adverse cardiac events and mortality. Cardiac fibrosis is defined as an increase in the myocardial extracellular matrix (ECM) protein deposition, mainly collagen I and collagen III, that impairs cardiac function.

Two types of cardiac fibrotic lesions have been defined depending on their localization and the feature of ECM protein deposition. The first one is a reparative process, also named replacement fibrosis, that is observed as scar tissue. In this ischemic disease, oxygen deprivation of the heart muscle results in the necrosis and apoptosis of cardiomyocytes, leading to a loss of large amounts of cardiac cells that are essential for cardiac function. Cardiomyocyte death initiates a triphasic immune response that aims at clearing cell debris and promoting the replacement of the injured myocardium to maintain cardiac function.

The second type of fibrotic lesion is interstitial fibrosis, characterized by the diffuse deposition of collagen in the endomysium and perimysium. This interstitial fibrosis frequently comes with perivascular fibrosis and is specifically observed as secondary to chronic injuries, such as a pressure overload (aortic stenosis, hypertension), cardiac inflammation (myocarditis), and metabolic disorders (obesity, diabetes mellitus) as well as aging. Diffuse fibrosis is also frequently observed in the surviving infarcted heart, where it develops in remote areas. The myocardial interstitial fibrosis development alters myocardial architecture and physiology, modifying left ventricular compliance, diastolic function, and electrical connectivity, leading to arrythmia and adverse outcomes (hospitalization, mortality).

Whatever the context, interstitial cardiac fibrosis is correlated with cardiac dysfunctions and is known to contribute to HF with or without preserved ejection fraction. Thus, understanding the molecular pathways involved in cardiac fibroblast activation will permit the development of new therapeutic strategies to fight cardiac fibrosis and reverse HF.

Link: https://doi.org/10.3390/ijms24021756

As might be expected, epidemiological data shows that obesity in mid-life raises the risk of suffering frailty in later life. Excess visceral fat tissue increases the pace at which senescent cells accumulate in the body and generates chronic inflammation, disruptive of tissue structure and function. In that sense it literally accelerates aging and the onset of age-related conditions, particularly those known to be driven in large part by chronic inflammation.

The present study followed 4,509 community-dwelling participants from the population-based Tromsø study from 1994 to 2016 to examine the association between general and abdominal obesity and the risk of frailty. This study suggests an increased likelihood of pre-frailty/frailty among those with baseline obesity. Increased likelihood of pre-frailty/frailty was also observed among those with high or moderately high waist circumference (WC) at baseline.

Participants with baseline obesity (adjusted odds ratio [OR] 2.41), assessed by body mass index (BMI), were more likely to be pre-frail/frail than those with normal BMI. Participants with high (OR 2.14) or moderately high (OR 1.57) baseline WC were more likely to be pre-frail/frail than those with normal WC. Participants in the 'overweight to obesity' or the 'increasing obesity' trajectories had increased odds of pre-frailty/frailty compared with those in the stable normal BMI trajectory. Additionally, participants with a high WC at baseline, whose WC gradually or steeply increased throughout the follow-up period, had increased odds of being pre-frail/frail compared with those in a stable normal WC trajectory.

There are different mechanisms through which obesity might contribute to pre-frailty/frailty. Increased adiposity leads to increased secretion of pro-inflammatory adipokines, thus contributing to inflammation, which is also associated with frailty among older adults. Obesity leads to increased fat mass and increased lipid infiltration in muscle fibres resulting in reduced muscle strength and function. When coupled with an age-related decline in muscle mass and strength, it causes 'sarcopenic obesity', which is linked to an increased risk of frailty and disability.

Link: https://doi.org/10.1136/bmjopen-2022-065707

Mitochondria are the power plants of the cell, producing the chemical energy store molecule ATP, but are also integrated into a wide range of fundamental cellular processes. Mitochondrial function declines with age, likely an important contribution to age-related declines in energy-hungry tissues such as the brain and muscles. It is also known that mitochondrial dysfunction can provoke chronic inflammation via the mislocation of mitochondrial DNA into parts of the cell where it will act as a damage-associated molecular pattern. This upregulation of inflammatory signaling is a reasonable proposal for the way in which mitochondrial aging can contribute meaningfully to atherosclerosis.

Atherosclerosis is considered an inflammatory condition. Fundamentally, atherosclerosis results from the dysfunction of the macrophage cells responsible for clearing excess cholesterol from blood vessel walls. Greater inflammatory signaling reduces the ability of macrophages to undertake repair-related activities, encouraging them to instead enter an inflammatory mode of activity. Once a tipping point is reached in the establishment of toxic deposits of excess cholesterol in blood vessels walls, the lesions will grow over time as ever more macrophages are attracted to the problem, become overwhelmed, and die. Greater inflammatory signaling causes that tipping point to occur more readily.

The second plausible pathway for mitochondrial aging to contribute to atherosclerosis is via the increased generation of oxidative molecules observed to take place in the mitochondrial of cells in aged tissues. Oxidation of cholesterol, other lipids, and lipid carriers such as LDL particles can produce additional stress on the macrophages responsible for cleaning up this metabolic waste. Again, the tipping point in fatty lesions present in blood vessel walls occurs more readily given greater oxidative stress and consequent production of toxic lipids.

Mitochondrial Dysfunction: The Hidden Player in the Pathogenesis of Atherosclerosis?

The atherosclerotic process is very often responsible for several cardiovascular and cerebrovascular diseases. It is now well accepted and documented that atherosclerosis starts from endothelial dysfunction and lipid deposition, which progresses through macrophage infiltration, smooth muscles://en.wikipedia.org/wiki/Smooth_muscle">smooth muscle cell migration, and blood borne material deposition, and becomes clinically relevant due to complications, eventually leading to local intravascular thrombus formation. Modified lipoproteins, mainly oxidized low-density lipoproteins (oxLDL), are considered the major contributors to the genesis, progression, and immunological response occurring during the atherosclerotic process.

The first report linking mitochondria to atherosclerosis is from 1970. However, only in the last few years has increasing evidence really underlined the key role of mitochondrial dynamics in the pathogenesis of atherosclerosis. Vascular cells, such as endothelial and smooth muscle cells, due to their metabolic functions and their barrier role are the main targets of mitochondrial dysfunction. In the atherosclerosis process, dysfunctional mitochondria might cause alterations in cellular metabolism and respiration resulting in the excessive production of reactive oxygen species (ROS), leading to oxidative stress. While low levels of ROS exert important signaling functions, elevated ROS production induces the damage of cellular structures, alters DNA, proteins, and other molecules. These conditions can become chronic, thereby favoring atherosclerosis progression and destabilization.

Atherosclerosis is a multifactorial disease. Multiple clinical trials and basic studies have clearly demonstrated that the management of the known risk factors only is not enough to limit the burden of this condition which underlies most cardiovascular diseases. Increasing evidence suggests an important role for mitochondria in the initial steps of this process. They regulate the inflammatory response and oxidative stress, two key steps that, once dysfunctional, might modulate initiation and progression of the atherosclerotic lesion. Thus, the modulation of mitochondrial function could delay the development of endothelial dysfunction, which represents the primum movens of the atherosclerotic process. In this context, it will be important for research, at both preclinical and clinical levels, to define the precise therapeutic interventions focusing on mitochondrial functions.

Researchers here use nematode worms to demonstrate that a commonly used antihypertensive drug is a calorie restriction mimetic. The beneficial response to calorie restriction, resulting in improved health and longevity, evolved very early in the development of life, and the underlying mechanisms are surprisingly similar across near all species, even if the end results vary in degree. Long-lived species do not exhibit the sizable gains in life span observed in short-lived species, for example, even though the health benefits remain noteworthy. In the nematode study, the drug produces less impressive results than actual calorie restriction in this species, always the case with these compounds, but the extension of life span is the same ballpark as the results obtained using various other calorie restriction mimetic strategies and related genetic alterations in nematodes.

Repurposing drugs capable of extending lifespan and health span has a huge untapped potential in translational geroscience. Here, we searched for known compounds that elicit a similar gene expression signature to caloric restriction and identified rilmenidine, an I1-imidazoline receptor agonist and prescription medication for the treatment of hypertension. We then show that treating Caenorhabditis elegans with rilmenidine at young and older ages increases lifespan. We also demonstrate that the stress-resilience, health span, and lifespan benefits of rilmenidine treatment in C. elegans are mediated by the I1-imidazoline receptor nish-1, implicating this receptor as a potential longevity target.

Consistent with the shared caloric-restriction-mimicking gene signature, supplementing rilmenidine to calorically restricted C. elegans, genetic reduction of TORC1 function, or rapamycin treatment did not further increase lifespan. The rilmenidine-induced longevity required the transcription factors FOXO/DAF-16 and NRF1,NRF2,NRF3/SKN-1. Furthermore, we find that autophagy, but not AMPK signaling, was needed for rilmenidine-induced longevity. Moreover, transcriptional changes similar to caloric restriction were observed in liver and kidney tissues in mice treated with rilmenidine.

Together, these results reveal a geroprotective and potential caloric restriction mimetic effect by rilmenidine that warrant fresh lines of inquiry into this compound.

Link: https://doi.org/10.1111/acel.13774

A broad discussion of extracellular vesicles is really a broad discussion of cell communication, as much of the traffic of molecules between cells is carried inside vesicles. Researchers here discuss what is known of the roles played by vesicle-mediated communication in neurodegenerative conditions, still a very broad topic. One of the noteworthy contributions is that this traffic of vesicles enables the spread of prion-like altered and misfolded proteins, such as tau and α-synuclein, that are capable of seeding the generation of more such harmful molecules in the destination cell. Whether there are ways to selectively prevent this process of spread and seeding remains an open question; it seems a daunting prospect, since every part of the vesicle communication infrastructure performs useful functions.

Many neurodegenerative disorders are characterized by the abnormal aggregation of misfolded proteins that form amyloid deposits which possess prion-like behavior such as self-replication, intercellular transmission, and consequent induction of native forms of the same protein in surrounding cells. The distribution of the accumulated proteins and their correlated toxicity seem to be involved in the progression of nervous system degeneration. Molecular chaperones are known to maintain proteostasis, contribute to protein refolding to protect their function, and eliminate fatally misfolded proteins, prohibiting harmful effects. However, chaperone network efficiency declines during aging, prompting the onset and the development of neurological disorders.

Extracellular vesicles (EVs) are tiny membranous structures produced by a wide range of cells under physiological and pathological conditions, suggesting their significant role in fundamental processes particularly in cellular communication. They modulate the behavior of nearby and distant cells through their biological cargo. In the pathological context, EVs transport disease-causing entities, including prions, α-synuclein, and tau, helping to spread damage to non-affected areas and accelerating the progression of neurodegeneration. However, EVs are considered effective for delivering therapeutic factors to the nervous system, since they are capable of crossing the blood-brain barrier (BBB) and are involved in the transportation of a variety of cellular entities.

Here, we review the neurodegeneration process caused mainly by the inefficiency of chaperone systems as well as EV performance in neuropathies, their potential as diagnostic biomarkers and a promising EV-based therapeutic approach.

Link: https://doi.org/10.3390/ijms24020927

The skin is arguably one of the easiest of the large organs in the body to target for delivery of gene therapies, via established microneedle approaches. Nonetheless, much of the initial thrust of gene therapy clinical development focused instead on the liver, one of the other more tractable targets. Most material injected into the bloodstream ends up in the liver, and a single injection is logistically easier than coverage of large amounts of skin via microneedle patches, among other reasons.

Given the advent of messenger RNA (mRNA) encapsulated in lipid nanoparticles (either artificial or repurposed extracellular vesicles) as a proven gene therapy vector, however, adjusting the behavior of skin cells to generate elastin or collagen to reverse some of the loss of structure and elasticity in aged skin seems a practical goal at the present time. This while bearing in mind that elastin structure is complex, and any solution there will probably look more like adjusting the regulation of correctly structured elastin deposition rather than just expressing more elastin.

LNP-delivered mRNA lasts only a short time in tissues, a matter of a few days at most. This is a big advantage for any therapy one might hope to deliver to very large numbers of people, given the way that regulators such as the FDA think about risk and safety. From a regulatory point of view, one of the (many) issues with the early gene therapy technologies, such as viral vectors, is that they last for a very long time. This dramatically limits the potential applications.

Given an mRNA therapeutic that actually works, one or more genes that when upregulated will dramatically improve the structural integrity of aged skin, such a treatment could be adopted and widely used by the established "anti-aging" clinical infrastructure. That ecosystem that already uses microneedle techniques extensively to deliver marginal or useless treatments. One can hope that the good will chase out the bad in the long term, and snake oil will give way to effective therapies.

Intradermally delivered mRNA-encapsulating extracellular vesicles for collagen-replacement therapy

Recent developments in messenger RNA-modification techniques have enhanced the therapeutic efficiency of mRNA delivery and its potential for near-term clinical applications, including protein-replacement therapy and vaccination against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. However, the intrinsic inability and potential immunogenicity of mRNAs require that they be encapsulated within delivery vehicles. Current mRNA-delivery modalities centre on the usage of lipid nanoparticle (LNP) carriers for encapsulation and transport.

Extracellular vesicles (EVs), including exosomes and microvesicles, play a major role in the transport of biomolecules and nucleic acids, including mRNAs, within the human body. As a result, in recent years, EVs have emerged as promising carriers for nucleic-acid-based therapeutics owing to their intrinsic biocompatibility, their ability to cross physiological barriers and their low immunogenicity. Unlike LNPs, EVs, including exosomes, are endogenously produced by the body's cells and lead to lower levels of inflammatory responses. Moreover, strategies to cheaply and easily produce large quantities of exosomes have been developed.

We previously reported a cellular nanoporation (CNP) method in which transient nanometric pores were created on the surface of source cells to allow for the large-scale loading of full-transcript mRNAs into secreted EVs. Here, by using a mouse model of acute photoaging that closely mimics the pathophysiological features of aging-damaged skin in humans, we show the utility of exosome-based COL1A1 mRNA therapy to replace dermal collagen-protein loss as an anti-aging treatment for photoaged skin. To improve the efficiency of mRNA delivery and retention, we also show that the delivery of collagen mRNA via a hyaluronic acid (HA) microneedle (COL1A1-EV MN) patch allows for a more efficient distribution of mRNA in the dermis, resulting in durable collagen-protein engraftment and in an improved treatment of wrinkles in photoaged skin.

If I'm understanding the results presented here correctly, the reversine small molecule enables senescent cells to return to a more normal state of function, including replication, at least in muscle cells examined in cell culture. The researchers believe it is triggering some of the same reprogramming pathways as the Yamanaka factors, perhaps by inducing expression of Oct4, but are not yet certain as to what is going on under the hood. Is it a good idea to take senescent cells in the body and return them to normal function? That is a good question, and has been raised for other approaches to senescence reversal. At least some senescent cells are senescent for a good reason, being damaged in ways that may lead to cancer, and all senescent cells undergo significant DNA damage in the process of becoming senescent. Reversal of senescence, versus just destroying senescent cells, sounds a lot like a cancer waiting to happen.

Skeletal muscle has a remarkable capacity to regenerate by activation of myogenic progenitor cells; however, both the number of these progenitors and their regenerative capacity decline with aging and cellular senescence. Metabolic changes such as impaired glycolysis, insulin sensitivity, and mitochondrial respiration are affected by senescence contributing to loss of the myoblast capacity to differentiate. Aging is also associated with impaired autophagy, which is essential to maintain satellite cell stemness and mitochondrial turn over.

Several studies found that the small molecule 2,6-disubstituted purine, reversine, increased cellular plasticity as demonstrated by increased differentiation potential of progenitor cells toward the neuroectodermal lineage; dedifferentiation of C2C12 myoblasts to a progenitor-like state; as well as dedifferentiation of sheep fibroblasts into multipotent progenitor cells, possibly via expression of the pluripotent factor, Oct4. Other studies reported that reversine may have anticancer properties. Indeed, reversine is an Aurora B protein kinase inhibitor, causing failure in mitotic chromosome segregation, cytokinesis, and cell proliferation.

Based on these results, we hypothesized that reversine might ameliorate the hallmarks of cellular senescence in human myoblasts. We discovered that short-term treatment of fully senescent myoblasts with reversine could restore insulin resistance, enhance glucose metabolism and oxidative phosphorylation, likely via reactivation of autophagy, ultimately restoring the differentiation ability of myoblasts to form myofibers. Our results suggest that reversine may have the potential to be used as a novel, antiaging treatment.

Link: https://doi.org/10.1111/acel.13764

Osteopontin levels are higher in blood samples taken from older people than in those taken from young people. It is a component of the senescence-associated secretory phenotype (SASP) produced by senescent cells, disruptive to tissue function. Osteopontin acts as a regulator in a number of tissues, and appears to be relevant to the age-related decline, such as of hematopoiesis and muscle function. Here, researchers review what is known of the role of osteopontin in aging.

Osteopontin (OPN) is a multifunctional noncollagenous matrix phosphoprotein that is expressed both intracellularly and extracellularly in various tissues. As a growth regulatory protein and proinflammatory immunochemokine, OPN is involved in the pathological processes of many diseases. Recent studies have found that OPN is widely involved in the aging processes of multiple organs and tissues, such as T-cell senescence, atherosclerosis, skeletal muscle regeneration, osteoporosis, neurodegenerative changes, hematopoietic stem cell reconstruction, and retinal aging. However, the regulatory roles and mechanisms of OPN in the aging process of different tissues are not uniform, and OPN even has diverse roles in different developmental stages of the same tissue, generating uncertainty for the future study and utilization of OPN.

Numerous research results have shown the dual roles of OPN in the aging process. For example, in the nervous system, OPN not only causes neurotoxicity but also acts as a neuroprotective agent for Parkinson's disease. In the process of liver aging, OPN not only induces the occurrence and development of age-related liver fibrosis but also delays the aging and apoptosis of hepatocytes and promotes their regeneration by restoring the autophagy activity of aging liver cells. In addition, OPN also plays a dual role in the process of eye aging. On the one hand, in the early stage of the disease, OPN expression increases to mediate its protective effect on adverse pathological changes. On the other hand, excessive accumulation of OPN aggravates calcification and calcium deposition in tissues, which is an important link in pathological degeneration.

The role of OPN in the aging process has not been fully clarified. More importantly, the critical point of this phenomenon is not completely clear. Therefore, further in-depth studies investigating whether OPN mediates and participates in the effects of antiaging factors such as sports, nutrition, and healthy lifestyle on the aging process are worthwhile and will hopefully provide new ideas and treatment schemes for many clinical diseases in the future.

Link: https://doi.org/10.3389/fendo.2022.1014853

The comparative biology of aging, the study of aging in species with widely divergent life spans, is hoped to improve the catalog and understanding of important mechanisms of aging. It may or may not turn out to be the case that the biochemistry of long-lived species can give rise to practical therapies that slow aspects of human aging, at least in the near future of the next few decades. Engineering a human that ages more slowly seems a far more daunting task than the production of rejuvenation therapies that repair the known forms of cell and tissue damage that drive aging.

An alternative to comparing other species with humans is to take a collection of closely related species with divergent life spans and attempt to find out why they are different. Even if these species are very different from our own, aging evolved very early indeed in the tree of life, and there is the hope that lessons can be learned.

Even from fish, as today's open access paper discusses. The authors report on their initial investigation of rockfish species, with life spans varying from a decade to a few centuries. Any given strand of this sort of comparative biology research can progress for decades, gathering data without arriving at a clear picture as to the biochemistry and how it might be used to build new medicines for our species. One might look at the long-running investigation of proficient regeneration in salamanders, for example. It is definitely too soon to say what might be learned from a closer look at rockfish biochemistry.

Convergent genomics of longevity in rockfishes highlights the genetics of human life span variation

Aging pathologies may be delayed, ameliorated, or prevented in aggregate by targeting the molecular foundations of the declines in homeostasis and function that arise over time. The knowledge of foundational targets suitable for such intervention remains limited, yet evolution has already leveraged such means, as is evident in the vast diversity of longevities in nature. Various species display aging-associated functional declines at wildly different rates and timings, including those that survive well beyond a human life span. As these traits are heritable and defining for many species, the underlying genetic mechanisms can be tracked through comparative genomic approaches.

There are many examples of long-lived animals. The Rougheye Rockfish, Sebastes aleutianus, is one such vertebrate species, with a maximum life span of over 205 years. Regardless of the aging mechanism - oxidative damage, proteostasis collapse, DNA damage, telomere/genomic maintenance, epigenetic drift, etc. - S. aleutianus resists the deleterious effects of age for over two centuries, enduring the variety of internal and external stressors assured with time. S. aleutianus is not the only rockfish lineage with this exceptional capability. The clade encompasses at least 107 extant species, ranging in maximum longevity from 11 to 205 years. Fortunately, multiple, independent lineages of rockfishes exhibit impressive life spans, imparting power into comparative approaches.

Our analyses reveal a common network of genes under convergent evolution, encompassing established aging regulators such as insulin signaling, yet also identify flavonoid (aryl-hydrocarbon) metabolism as a pathway modulating longevity. The selective pressures on these pathways indicate the ancestral state of rockfishes was long lived and that the changes in short-lived lineages are adaptive. These pathways were also used to explore genome-wide association studies of human longevity, identifying the aryl-hydrocarbon metabolism pathway to be significantly associated with human survival to the 99th percentile. This evolutionary intersection defines and cross-validates a previously unappreciated genetic architecture that associates with the evolution of longevity across vertebrates.

As noted here, joining the circulatory systems of an old and young mouse results in some degree of rejuvenation in the old mouse. Where brain function is improved, researchers are interested in how changes in the blood signaling environment might be involved. While research initially focused on factors in young blood that are reduced in old blood, it is increasingly thought that the important mechanism is a dilution of harmful factors carried in the old bloodstream. This has led to a few studies of plasma transfer and dilution in humans, and at least one company attempting to determine the optimal dose and protocol to make this approach into a widely used therapy.

Researchers have recently leveraged evolving proteomic approaches and single-cell RNA-sequencing technologies to begin to decode the functional impact of intertissue communication on brain aging. The application of molecular approaches to investigate systemic and lifestyle interventions, such as heterochronic parabiosis (in which the circulatory systems of young and aged animals are surgically connected), young blood plasma administration, exercise, and caloric restriction, has uncovered broad rejuvenating effects on the aged brain that are mediated through blood, which question the very notion that brain aging is immutable.

To what extent do pro-aging and pro-youthful factors act through convergent or divergent mechanisms? With respect to a common tissue of origin, the hematopoietic system and inflammatory processes emerge as a source of pro-aging factors. Nevertheless, in many cases, the cell type or tissue sources remain obfuscated. Although earlier work identified a series of muscle-derived myokines, the liver as a major secretory organ is rapidly emerging as an additional source of exercise-induced factors, with IGF1, GPLD1, SEPP1, and clusterin all being putative liver-derived exerkines.

Regarding mechanisms of action, numerous aging and rejuvenating factors exert similar effects on the brain; therefore, it is important to understand whether each factor acts through the same or parallel cellular targets and molecular pathways. Given the predominant immune nature of pro-aging factors in old blood, microglia appear an obvious first target. However, several recent studies are highlighting brain endothelial cells as a potential nexus by which pro-aging factors, including VCAM1, ASM, CyPA, and CCL2, regulate brain aging. Conversely, pro-youthful factors identified across interventions, such as GDF11, clusterin, GPLD1, and α-klotho, may likewise exert their rejuvenating effects indirectly on the aged brain by restoring function to the aging vasculature and additional peripheral targets.

Additionally, a series of pro-youthful factors, including TIMP2, osteocalcin, SPARCL1, and THSB4, appear to selectively enhance synaptic or cognitive functions; whereas others, such as FGF17 and SEPP1, have been demonstrated to regulate regenerative and stem cell functions. Collectively, these findings indicate that brain function can be restored through several parallel targets as well as direct and indirect mechanisms with relevance for future therapeutic approaches.

Link: https://doi.org/10.1038/s41593-022-01238-8

Diabetes involves the loss of insulin-generating β-cells in the pancreas. In recent years, evidence has suggested that the accumulation of senescent cells in the pancreas - with age and with obesity - is an important contributing factor in this condition. Researchers here report on a study of senescent cell clearance in a mouse model of type 2 diabetes, finding that there doesn't appear to be any downside to trying, but that only some of the treated mice showed improvement. That is suggestive that other mechanisms derived from obesity are also relevant and important to disease progression.

Type 2 diabetes is partly characterized by decreased β-cell mass and function which have been linked to cellular senescence. Despite a low basal proliferative rate of adult β-cells, they can respond to growth stimuli, but this proliferative capacity decreases with age and correlates with increased expression of senescence effector, p16Ink4a. We hypothesized that selective deletion of p16Ink4a-positive cells would enhance the proliferative capacity of the remaining β-cells due to the elimination of the local senescence-associated secretory phenotype (SASP).

We aimed to investigate the effects of p16Ink4a-positive cell removal on the mass and proliferative capacity of remaining β-cells using INK-ATTAC mice as a transgenic model of senolysis. Clearance of p16Ink4a positive subpopulation was tested in mice of different ages, males and females, and with two different insulin resistance models: high-fat diet (HFD) and insulin receptor antagonist (S961).

Clearance of p16Ink4a-positive cells did not affect the overall β-cell mass. β-cell proliferative capacity negatively correlated with cellular senescence load and clearance of p16Ink4a positive cells in 1-year-old HFD mice improved β-cell function and increased proliferative capacity in a subset of animals. Single-cell sequencing revealed that the targeted p16Ink4a subpopulation of β-cells is non-proliferative and non-SASP producing whereas additional senescent subpopulations remained contributing to continued local SASP secretion. In conclusion, deletion of p16Ink4a cells did not negatively impact beta-cell mass and blood glucose under basal and HFD conditions and proliferation was restored in a subset of HFD mice opening further therapeutic targets in the treatment of diabetes.

Link: https://doi.org/10.18632/aging.204483

To what degree is autophagy important in the sizable differences in life span between mammalian species? That is an interesting question. It appears that long-lived species exhibit more effective autophagy, and it also appears that many of the methods of altering metabolism in order to modestly slow aging that were discovered over the past thirty years involve upregulation of autophagy. The effects of calorie restriction on longevity depend upon the correct function of autophagy, and vanish if autophagy is disabled.

It is worth noting that autophagy is difficult to measure, however. It involves many distinct processes, such as identification of materials for recycling, formation and transport of autophagosomes, the operation of lysosomes, and so forth. One can measure the activity of specific proteins involved in various steps of autophagy, but that isn't necessarily informative as to whether the whole autophagic system is functioning correctly.

Further, calorie restriction may extend life in mice by up to 40%, but it certainly doesn't do anywhere near as much in long-lived mammalian species such as our own. Can autophagy really be so great a contribution to species differences in life span if calorie restriction and consequent upregulation of autophagy only adds a few years to human life span? It is hard to reconcile that with the difference between a rat life span of a few years and a naked mole-rat life span of a few decades, or the sizable difference in life span between a human and the longest-lived whales.

Autophagy and longevity: Evolutionary hints from hyper-longevous mammals

The decline of autophagic ability is one of the most acknowledged molecular hallmarks of cellular aging. As eukaryotic organisms age, they suffer from a progressive, maladaptive decrease in the ability to activate autophagy and benefit from its degradative/renewal properties, leading the cells to accumulate damaged organelles and cytotoxic macromolecules overall. Autophagy appears to be intimately connected with the modulation of longevity, as proved by several studies which demonstrated an effect on cellular and organismal lifespan when autophagy was harnessed either genetically or pharmacologically. The exact mechanisms behind this connection are yet unclear, given the vastity of genes involved in the process and the different function afforded by autophagy including proteostasis, nutrient regulation, and immunity.

Evolution provides us with evidence of selective adaptations in the autophagic process across long-lived organisms, including phylogenetically close-to-humans taxa belonging to the mammalian clade. This confirms the existence of an either direct or indirect link between autophagy and lifespan modulation but concurrently may represent a unique opportunity to shed light on the key molecular elements involved through comparative studies. A connection between autophagic activity and organismal lifespan was first identified in a pioneering study on insulin/IGF-1 signalling, where autophagy-inducing mutations in daf-2 were associated with lifespan extension in C. elegans and later confirmed in organisms such as drosophila, mice, and humans. Another important discovery linking autophagy with longevity emerged from studies on mTOR signalling and dietary restriction, an established universal life-extending intervention. Starvation-induced autophagy was proven to be causal to lifespan extension in several animal models from yeasts to great apes.

Transcriptomic studies of the longest-lived mammal, the bowhead whale (Balaena mysticetus), revealed overexpression of genes for DNA repair, autophagy induction, and ubiquitination. To better inquire into the evolution of longevity in mammals, further studies were aimed towards the identification of unique adaptations in molecular markers of aging in taxa characterised by high longevity quotients. One of the most studied mammalian species characterised by a high longevity quotient is the naked mole rat (NMR, Heterocephalus glaber). This rodent is capable of living substantially more than expected more for a mammal of comparable body size. Interestingly, studies of the NMR showed higher basal autophagic activity (measured as expression of LC3II and beclin-1 autophagic marker proteins) when compared with C57Bl/6 mice. Furthermore, NMR's transcriptome analyses recapitulated features found in the bowhead whale, with overexpression of genes for DNA repair and autophagy, which proved down-regulated in mammals with low longevity quotients, such as mice and cattle.

A study on the speciation of another noncanonical rodent model characterized by a high longevity quotient, the blind mole rat (Spalax galili), revealed a strong dependence on proteostatic machineries such as autophagy and the proteasome in determining niche adaptation, since these animals need to deal with a high metabolic stress deriving from the limited nutrient sources of soil dwelling.

Another example of this phenomenon may be the case of the unique evolution witnessed in bats, the order of mammals with the highest longevity quotient among all. During the last years, several studies have been aimed to decipher the exceptional resistance of bats against aging and age-related diseases with many of these reporting an upregulation of autophagic activity across different tissues when compared with mice and other mammals. In a study on primary fibroblasts, both young and aged bats were found to have a constitutively higher level of autophagic flux than murine counterparts. Further analyses on the blood transcriptome showed upregulation of autophagy-associated genes and transcript enrichment for terms associated with macroautophagy and positive regulation of autophagy. Autophagy in bats arguably evolved to face the massive production of cytotoxic metabolic by-products deriving from the extremely energetically demanding activity of powered flight.

Finally, being aging now acknowledged as the driving cause of all age-related disorders, worth of interest are the evolutionary implications deriving from evidence of resistance from these diseases in the longest-lived mammalian models. Further attesting to autophagy as an anti-aging biological asset, recent studies found high autophagic activity to inversely correlate with the incidence and severity of pathologies associated with aging, such as neurodegeneration, frailty, and cancer. Bats are once again a unique study model as they show high cognitive performances (e.g., echolocation) throughout their extended lifespan, do not display phenotypic aging (young and old bats are macroscopically indistinguishable), and show lower occurrence of cancer when compared with other mammals.

Senescent cells are constantly created and destroyed in all tissues of the body throughout life, but the number present at any given time increases with age, in large part because the immune system ceases to clear senescent cells as efficiently as it should. Senescent cells secrete pro-growth, pro-inflammatory factors that are useful in the short term, such as during wound healing, or to draw attention to potentially cancerous cells. When kept up for the long term, however, the signaling of senescent cells is highly disruptive to tissue structure and function. The example given here, of disrupted intestinal stem cell function resulting from specific molecules generated by senescent cells, is but one of many.

Cellular senescence and the senescence-associated secretory phenotype (SASP) are implicated in aging and age-related disease, and SASP-related inflammation is thought to contribute to tissue dysfunction in aging and diseased animals. However, whether and how SASP factors influence the regenerative capacity of tissues remains unclear. Here, using intestinal organoids as a model of tissue regeneration, we show that SASP factors released by senescent fibroblasts deregulate stem cell activity and differentiation and ultimately impair crypt formation.

The SASP (including factors like Ptk7, which are not technically secreted but are shed as a consequence of senescent cell surface remodeling) is believed to be a critical part of the contribution of senescent cells to age-related disease, primarily by influencing the tissue microenvironment and spreading senescence through a "bystander effect". Accordingly, selective elimination of senescent cells improves many aging symptoms and disease phenotypes. Our study identifies sPtk7 as a critical SASP factor that has a direct and reversible impact on intestinal stem cell proliferation and differentiation.

Our data show that Ptk7 is also expressed in fibroblasts and epithelial cells of the mouse small intestine, and that shedding of the N-terminal domain of Ptk7 is increased in the gut of old mice. Our co-culture experiments of intestinal organoids with senescent intestinal fibroblasts further show that fibroblast-derived Ptk7 impairs differentiation of intestinal stem cells. How this effect on intestinal stem cells influences epithelial homeostasis and regeneration remains to be established.

Link: https://doi.org/10.1038/s41467-022-35487-9

Mitochondria are the distance descendants of symbiotic bacteria, and the hundreds of mitochondria present in every cell behave much like bacteria. They constantly fuse together, undergo fission, and swap component parts. This mitochondrial dynamics becomes imbalanced in aged tissues, the immediate consequence of epigenetic changes that alter the availability of various proteins involved in fusion or fission. Researchers here note that pushing mitochondrial dynamics too far in either direction, too much fusion or too much fission, will produce inflammatory signaling. This is an interesting connection between mitochondrial dysfunction and the chronic inflammation characteristic of aging.

Mitochondrial dynamics regulate mitochondrial homeostasis through the modulation of multiple elements such as organelle interaction and mitochondrial morphology. In this study, we provide evidence that mitochondrial dynamics also controls the activation of intracellular inflammatory pathways. Our conclusion is based on a number of observations, namely that: a) repression of the mitochondrial fusion proteins Mfn1 or Mfn2 induces mitochondrial fragmentation and TLR9-dependent NFκB activation; and b) Drp1 or Fis1 repression causes mitochondrial elongation and both NFκB-dependent and type I IFN inflammatory responses.

Given the role of mitochondrial dynamics in regulating mitochondrial function and mitophagy, it is conceivable that alterations in these processes could be involved in triggering inflammation upon mitochondrial dynamics disturbances. Here, we show that indeed, the different manipulations induced by repressing Mfn1, Mfn2, Drp1, or Fis1 lead to very different patterns of alterations in mitochondrial membrane potential, mitochondrial superoxide production, mitochondrial mass, mitochondrial respiration, or mitophagy, which does not explain the inflammatory response observed in each condition. In contrast, we find that the inflammatory responses depend on the presence of mitochondrial DNA (mtDNA), which suggests that those changes in mitochondrial function and quality are consequences of adaptations in mitochondrial biology that are not directly related to the inflammatory response.

Mitochondrial stress can trigger sterile inflammation by inducing mtDNA mislocation and allowing mtDNA recognition by DNA sensors, mitochondrial dynamics are essential in maintaining mitochondrial homeostasis, and muscle inflammation and atrophy are hallmarks of impaired muscle health. Based on our findings, we propose that the maintenance of mitochondrial dynamics is a key factor in preventing the trigger of inflammatory responses characterized by mtDNA mislocation and DNA sensor activation, and that muscle inflammation induced by mitochondrial fragmentation plays a causative role in the development of muscle atrophy.

Link: https://doi.org/10.1038/s41467-022-35732-1

Treatment with radiation to kill cancerous cells results in an increased burden of senescent cells, both in and around the tumor. This is a fair trade-off; a senescent cancerous cell may be harmful in and of itself, but it is a good deal less harmful in the long run than an active cancer cell. Unfortunately senescent cells produce pro-growth, pro-inflammatory signaling that is disruptive of tissue function, raises the risk of suffering a range of age-related conditions, and increases the risk of both reoccurrence of the treated cancer and the development of later unrelated cancers.

Thus given the work taking place outside the cancer research community on the development of therapies to selectively destroy senescent cells, suppress senescent cell signaling, or prevent cells from becoming senescent, researchers are starting to consider how to integrate these approaches into the treatment of cancer. At the very least, it seems sensible to start by applying senolytics to destroy lingering senescent cells after cancer therapy is complete, in order to reduce the lasting side-effects of such therapies. Beyond that it is an open question as to when and whether it is a good idea to combine targeting of senescent cells with cancer therapy. It isn't at all clear as to when it will be beneficial to remove senescent cells during treatment.

Radiation-induced senescence: therapeutic opportunities

Cellular senescence, which is a normal consequence of aging, is characterized by irreversible cell cycle arrest in response to various stress stimuli, resistance to apoptosis and senescent-associated secretory phenotype (SASP). Cellular senescence is a cell fate decision and normal physiological event, which plays essential roles in development, prevention of cancer, and the wound healing process. However, when cells are subjected to sustained sub-lethal injury including radiation therapy or chemotherapy, continued oxidative stress and chronic inflammation prompt entry into cellular senescence. The chronic state of radiation-induced senescence together with secretion of pro-inflammatory factors, a phenomenon known as the SASP, contribute to the major pathology of radiation-induced normal tissue and organ injury.

Factors influencing the role of cellular senescence in the tumor tissue widely vary in part due to the tumor tissue heterogeneity, the oncogenic status, immune cell recognition by acute vs chronic senescence and radiation dose regimen, to name a few. For example, acute induction of cellular senescence is considered important for cancer prevention by stimulating the immune system to rapidly eliminate the genetically unstable cells, whereas chronic cellular senescence creates a tumor promoting environment through a secretion of SASP. Chronic cellular senescence also contribute to the radiation-induced late effects in the normal tissues and organs such as lung and skin fibrosis, cognitive dysfunction/necrosis to name a few. Overall, the SASP of senescent cancer cells is considered to be primarily detrimental in therapy resistance, immunosuppression and metastasis.

Senolytics are a class of drugs that selectively eliminate senescent cells. Multiple pharmacological strategies are under investigation to remove senescent cells. They include small molecules, peptides, and antibodies. Our new preliminary data show the potential of senolytic as well as anti-cancer agents to illustrate the foregoing point. Alvespimycin (17-DMAG), an HSP-90 inhibitor, reduced normal tissue damage after a radiation exposure without compromising radiotherapy effectiveness. Using another class of senolytics, other researchers have shown some functional and structural improvement in cardiovascular function, and radiation-induced muscle weakness using the combined senolytics, dasanitib and quercetin. Using another class of senolytics, navitoclax, a Bcl-2 family inhibitor, improved radiation-induced pulmonary fibrosis, radiation-induced hematotoxicity, age related hematopoietic stem cell (HSC) dysfunction, and delayed malignant glioma/en.wikipedia.org/wiki/Glioma">malignant glioma recurrence by eliminating the radiation-induced senescent astrocytes. The potential of navitoclax to mitigate normal tissue radiation damage while sensitizing radiation cytotoxicity in tumors is further supported by navitoclax's ability to overcome hypoxia-driven radiosensitivity.

For every researcher interested in new approaches, there are another few whose horizons end at supplements and exercise. Thus one finds papers like this one, in which the authors discuss whether probiotics and exercise can help to ameliorate the aging of the gut microbiome. It seems a little ridiculous to focus completely on these options in a world in which fecal microbiota transplantation has been shown to produce much larger, lasting effects on the gut microbiome following a single treatment, and a few other less well developed options on the table, such as flagellin immunization, may prove to be as effective and useful.

Despite numerous interindividual differences, it is now clear that the composition of the microbiota of the elderly differs significantly from that of young and middle-aged people. Numerous progresses have been made on the study of the microbiota, and evidence is accumulating on the efficacy of therapies based on the microbiota, even if the clinical applications on obtaining the slowing down of aging are still lacking and more advanced human studies at strain-level resolution are required. The gut microbiota research should be pointed on specific signatures related to longevity. Future research should consider the individuals' baseline microbiome features and customize the therapies to meet their needs. Although knowledge on the microbiota in humans is limited, the present evidence led to hypothesizing strategies useful for maintaining a good state of health in the elderly.

A healthy lifestyle, with a balanced diet rich in unrefined foods of natural origin, together with adequate physical exercise, aerobic or combined, sustained for sufficiently long periods, allows for restoration and maintenance of a healthy microbiota even in old age, promoting healthy aging. Of course, prevention of the decline of the microbiota with a delayed onset of age-related pathologies should be preferred; however, a detailed knowledge of the actions of gut microorganisms will allow the formulation and diffusion of products containing supplements such as probiotics, prebiotics, and nutraceuticals with specific properties. Obviously, the use of supplements must be targeted, individualized and calibrated on the needs of the individual subject, and appropriate strategies must be implemented to maintain the restored microbiota.

In this review, we focalized on the influence of lifestyle on the maintenance of a healthy microbiota in the elderly and on the consequences on the general state of health of the subject. The effects of specific supplements were also highlighted, in order to suggest personalized microbiota-based strategies for healthy aging.

Link: https://doi.org/10.3390/cells12010034

Researchers here discuss the relevance of the hallmarks of aging to the pathology of Alzheimer's disease. The hallmarks of aging are a mix of causative process and downstream consequences of those causes, and have come to be used as a laundry list of topics in discussions of aging in the years since the original paper was published. The underlying causes of Alzheimer's disease are still much debated, at least in the sense of establishing relative importance and the direction of causation. It is certainly a condition characterized by chronic inflammation and the buildup of protein aggregates, but how do these phenomenon arise? How do they connect to deeper causes of aging? That remains a challenging question to answer; the fastest and best approach is probably to develop the means to repair the damage of aging, repair each in isolation in animal models, and observe the outcome.

Alzheimer's disease (AD) is the most prevalent form of dementia, affecting more than 50 million individuals worldwide. AD is a multifactorial disease with environmental (30%) and genetic (70%) causes. Environmental factors are usually associated with sporadic AD (SAD), while genetic factors are associated with familial AD (FAD) and SAD. Interestingly, FAD and SAD differ in age of onset. According to the age of onset, AD can be divided into two categories of early-onset AD (EOAD) and late-onset AD (LOAD) before or after the age of 65. In all AD cases, approximately 5% are EOAD and 95% are LOAD, indicating that most AD is caused by aging in concert with a complex interaction of genetic and environmental risk factors.

AD, especially LOAD, is associated with aging and is characterized by selective neuronal vulnerability (SNV). However, the relationship between aging and SNV and the molecular basis of AD are not completely understood which need to be urgently elucidated. Aging is the inevitable time-dependent decline in physiological organ integrity, leading to impaired function and increased vulnerability to death. It is characterized by nine tentative hallmarks grouped into three main categories: primary hallmarks (genomic instability, telomere attrition, epigenetic alterations, and loss of proteostasis), antagonistic hallmarks (deregulated nutrient sensing, altered mitochondrial function, and cellular senescence), and integrative hallmarks (stem cell exhaustion and altered intercellular communication).

To date, the role of each aging hallmark in AD development remains unclear. This article will focus on the primary aging hallmarks as these are interconnected with other aging characteristics and are at the base of the hierarchical order of aging features, and have been shown to be related to AD. It is an attempt to improve our understanding of the pathological mechanisms of AD to find potential therapeutic approaches and diagnostic tools.

Link: https://doi.org/10.7150/thno.79535

Using 16S rRNA sequencing, it is possible to accurately measure the composition of the gut microbiome from a stool sample, producing a comprehensive picture of the distribution of microbial species. Given this capability, now widely available at low cost, researchers have shown that the gut microbiome changes with age in characteristic ways. Microbial species that provoke chronic inflammation or otherwise deliver harmful metabolites into the body increase in number. Species that deliver beneficial metabolites, such as the butyrate that is known to upregulate BDNF expression and improve neurogenesis, decline in number. A large part of this shift may be due to the age-related decline of the immune system, but given that significant changes in the gut microbiome occur as young as mid-30s, lifestyle choices may play a significant role.

Importantly, the ability to measure the microbiome allows researchers to assess whether specific interventions can restore a more youthful gut microbiome to older individuals. The use of fecal microbiota transplant from young to old animals has shown that restoration is possible, producing a lasting improvement in the microbiome following a single treatment, and consequent benefits to health and life span. Today's research materials are an example of the type, showing that fecal microbiota transplant from young donors in mice improves aging immune function.

This ability to produce lasting change suggests that the aging of the microbiome is only loosely coupled to the aging of the body; presumably it will continue to degrade at some pace following improvement, but that pace is slow enough to make such an improvement an attractive form of therapy. Beyond fecal microbiota transplantation, other interventions have shown some ability to produce lasting improvement in the gut microbiome, such as flagellin immunization in order to provoke the immune system into more aggressively removing harmful microbes. In principle probiotics might be able to achieve the same goal, but as yet the available probiotics represent only a small fraction of the species delivered by fecal microbiota transplantation, and do not appear to produce lasting effects.

Fecal microbiota transplantation from young mice rejuvenates aged hematopoietic stem cells by suppressing inflammation

Hematopoietic stem cell (HSC) aging is accompanied by hematopoietic reconstitution dysfunction, including loss of regenerative and engraftment ability, myeloid differentiation bias and elevated risks of hematopoietic malignancies. Gut microbiota, a key regulator of host health and immunity, has been recently reported to impact hematopoiesis. However, there is currently limited empirical evidence elucidating the direct impact of gut microbiome on aging hematopoiesis.

In this study, we performed fecal microbiota transplantation (FMT) from young mice to aged mice and observed significant increment in lymphoid differentiation and decrease in myeloid differentiation in aged recipient mice. Further, FMT from young mice rejuvenated aged HSCs with enhanced short-term and long-term hematopoietic repopulation capacity. Mechanistically, single-cell RNA sequencing deciphered that FMT from young mice mitigated inflammatory signals, upregulated FoxO signaling pathway and promoted lymphoid differentiation of HSCs during aging. Finally, integrated microbiome and metabolome analyses uncovered that FMT reshaped gut microbiota construction and metabolite landscape, and Lachnospiraceae and tryptophan-associated metabolites promoted the recovery of hematopoiesis and rejuvenated aged HSCs.

Together, our study highlights the paramount importance of the gut microbiota in HSC aging and provides insights into therapeutic strategies for aging-related hematologic disorders.

The treatment of atherosclerosis is trapped in a rut, and has been for some time. Near all of the development in this field is focused on producing ever more innovative ways to reduce LDL-cholesterol in the bloodstream. Unfortunately, this cannot do more than modestly slow the condition; it can't reverse existing plaque to any great degree. By the time a plaque has formed, it has become a self-sustaining lesion, inflamed and attracting ever more immune cells to become overwhelmed by the toxic plaque environment and die, adding their mass to the plaque. The input of LDL-cholesterol from the bloodstream, while creating the tipping point of plaque formation in the early stages, becomes a minor contribution at that later stage of the condition.

Cyclarity is one of the few groups attempting to break out of the rut, along with Repair Biotechnologies. Cyclarity is testing whether or not targeted removal of the toxic modified cholesterol known as 7-ketocholesterol can improve the state of the disrupted plaque tissue environment far enough to enable some form of repair and reversal by otherwise overwhelmed tissue maintenance systems. Since animal models would be fairly uninformative on this question, the company is instead taking a very fast path to human trials based on tissue models and safety data alone. It will be interesting to see how well this works at the end of the day.

The development of therapeutics to combat atherosclerotic cardiovascular disease (CVD) forms a significant part of humankind's battle against chronic disease. The basic pathological process of atherosclerosis has been characterized for over a century. Despite its multifaceted nature, the major clinical focus for treatment of atherosclerosis has involved targeting cholesterol metabolism to reduce the rate of plaque accumulation within blood vessels or improving recovery after a cardiovascular event. Of all therapeutic interventions, cholesterol-lowering statins dominate the CVD market. In fact, statins are the most commonly-prescribed drug in the world. In essence, the field of CVD therapeutics has adopted a strategy of slowing the rate of disease progression and reducing the risk of complications from disease (i.e. cardiovascular events, like heart attacks). Although this strategy has played a role in the significant increase in average human lifespan over the past century, it is essentially a disease management approach that has failed to erase CVD from the list of humanity's most prolific killers.

There are several downstream events that transform cholesterol into a toxic waste product. Most importantly, the development of atherosclerosis is contingent upon cholesterol penetrating blood vessels and becoming oxidized - making it non-degradable and toxic. This corrupted form of cholesterol ultimately drives an insidious cycle of low level chronic inflammation (inflammaging), macrophage dysfunction, and plaque accumulation. Cyclarity Therapeutics works to rehabilitate the cardiovascular system's own, natural self-repair mechanism, removing the toxic byproducts that cause macrophage dysfunction and restoring their natural ability to manage and reduce plaque. This is a "first in class" therapy that could redefine the treatment paradigm for atherosclerosis, paving a path for a new class of disease-modifying therapeutics. For the first time in the history of mankind's fight against chronic disease, the possibility of disease reversal has been enabled.

Cyclarity's candidate UDP-003 belongs to a class of compounds known as cyclodextrins. Cyclodextrins have special chemical properties that give them powerful fat/cholesterol binding capabilities. Cyclarity uses its novel computational platform technology to engineer cyclodextrins to enhance target specificity, safety, and efficacy relative to generic cyclodextrins. UDP-003 is designed to precisely bind and clear a toxic form of oxidized cholesterol, 7-ketocholesterol (7-KC), that builds up in immune cells (macrophages), transforming them into foam cells - the root cause of plaque formation.

Link: https://longevity.technology/investment/report/atherosclerosis/

The first senolytic therapy to be tested in mice and humans was the combination of dasatinib and quercetin. This continues to be tested in human trials by the Mayo Clinic, and has been shown to reduce the burden of senescent cells in humans to much the same degree as it does in mice. It remains to be seen as to whether any of the many forms of senolytic treatment under development are very much better at clearing senescent cells from aged tissues than dasatinib and quercetin. Either way, it is likely that the use of multiple different senolytics will be better than one alone, due to tissue by tissue differences in biodistribution and effectiveness.

Aging results in an elevated burden of senescent cells, senescence-associated secretory phenotype (SASP), and tissue infiltration of immune cells contributing to chronic low-grade inflammation and a host of age-related diseases. Recent evidence suggests that the clearance of senescent cells alleviates chronic inflammation and its associated dysfunction and diseases. However, the effect of this intervention on metabolic function in old age remains poorly understood.

Here, we demonstrate that dasatinib and quercetin (D&Q) have senolytic effects, reducing age-related increase in senescence-associated β-galactosidase, expression of p16 and p21 gene and P16 protein in perigonadal white adipose tissue (pgWAT). This treatment also suppressed age-related increase in the expression of a subset of pro-inflammatory SASP genes (mcp1, tnf-α, il-1α, il-1β, il-6, cxcl2, and cxcl10), crown-like structures, abundance of T cells and macrophages in pgWAT. In the liver and skeletal muscle, we did not find a robust effect of D&Q on senescence and inflammatory SASP markers.

Although we did not observe an age-related difference in glucose tolerance, D&Q treatment improved fasting blood glucose and glucose tolerance in old mice that was concomitant with lower hepatic gluconeogenesis. Additionally, D&Q improved insulin-stimulated suppression of plasma NEFAs, reduced fed and fasted plasma triglycerides, and improved systemic lipid tolerance. Collectively, results from this study suggest that D&Q attenuates adipose tissue inflammation and improves systemic metabolic function in old age. These findings have implications for the development of therapeutic agents to combat metabolic dysfunction and diseases in old age.

Link: https://doi.org/10.1111/acel.13767

Evidence suggests that there is a bidirectional relationship between tau aggregation and inflammation in the aging brain. Both occur in all brains, and when present to a greater degree contribute to the neurodegenerative conditions termed tauopathies. The most well known of these is Alzheimer's disease, in which tau aggregates and their surrounding toxic biochemistry cause the widespread cell death and severe symptoms that characterize the final stages of the condition.

Various studies individually support each of the two directions of the relationship between tau and inflammation. Removing senescent cells from the brain dampens inflammatory signaling, and thereby reduces tau pathology, for example. Here, researchers demonstrate a mechanism by which tau aggregation encourages transposable element activity that in turn provokes an inflammatory response. We might view the later stages of many neurodegenerative conditions as runaway feedback loops in which inflammation produces consequences that encourage further inflammation.

Pathogenic tau-induced transposable element-derived dsRNA drives neuroinflammation

Deposition of tau protein aggregates in the brain of affected individuals is a defining feature of "tauopathies," including Alzheimer's disease. Studies of human brain tissue and various model systems of tauopathy report that toxic forms of tau negatively affect nuclear and genomic architecture, identifying pathogenic tau-induced heterochromatin decondensation and consequent retrotransposon activation as a causal mediator of neurodegeneration. On the basis of their similarity to retroviruses, retrotransposons drive neuroinflammation via toxic intermediates, including double-stranded RNA (dsRNA).

We find that dsRNA and dsRNA sensing machinery are elevated in astrocytes of postmortem brain tissue from patients with Alzheimer's disease and progressive supranuclear palsy and in brains of tau transgenic mice. Using a Drosophila model of tauopathy, we identify specific tau-induced retrotransposons that form dsRNA and find that pathogenic tau and heterochromatin decondensation causally drive dsRNA-mediated neurodegeneration and neuroinflammation. Our study suggests that pathogenic tau-induced heterochromatin decondensation and retrotransposon activation cause elevation of inflammatory, transposable element-derived dsRNA in the adult brain.

Researchers here report on an investigation of mechanisms regulating the turnover of tau protein in brain cells. The hope is to find approaches that will more aggressively clear the tau aggregates found in neurodegenerative conditions via the usual cell maintenance processes responsible for breaking down excess proteins, such as autophagy and proteasomal degradation. It is far too early to say how promising this approach might turn out to be at the end of the day, but the initial exploration is interesting.

A novel screening approach led researchers to 11 new in vivo validated tau regulators. Of these, three targets - ubiquitin-specific protease 7 (USP 7), RING-Type E3 Ubiquitin Transferase (RNF130), and RING-Type E3 Ubiquitin Transferase (RNF149) - converged on the ubiquitin protein degradation pathway. The majority of intracellular proteins within all tissues are degraded by the ubiquitin-proteasomal pathway. This is a complex, tightly regulated process involving several discrete and successive steps. Ubiquitin molecules are first activated and transferred to carrier proteins. Multiple ubiquitin molecules are attached to the protein substrate via a group of enzymes called the E3 ubiquitin ligases. Finally, the ubiquitinated substrate is degraded.

Previous studies have implicated the ubiquitin ligase, CHIP (C-terminus of Hsc70-interacting protein), as an important regulator of tau turnover and a critical player in the selective elimination of abnormal tau species. Interestingly, in this study, the researchers discovered that USP7 stabilizes tau by protecting it from CHIP-mediated degradation. They also found that RNF130 and RNF149 decrease the levels of the tau degrader (CHIP) and that their inhibition increases CHIP which in turn decreases tau levels. To test if these target genes can regulate CHIP and tau levels in the brain, the team turned off their expression in adult mice that overexpress mutant tau.

"Turning off the expression of USP7, RNF130, or RNF149 in adult mice with tauopathy using a doxycycline-inducible system increased CHIP level, and reduced total and phosphorylated-tau proteins. We also saw a decrease in other tell-tale signs of tau pathology and neuroinflammation. Most excitingly, these mice performed as well as age-matched normal mice in tasks that require learning and memory - a strong indicator that increasing CHIP levels in addition to a concomitant reduction in tau levels can improve neuronal and overall brain function in these mice."

Link: https://www.eurekalert.org/news-releases/976562

Researchers are attempting to determine exactly how the gut microbiome contributes to age-related chronic inflammation, particularly inflammation in the brain. This may be largely due to a few compounds produced by specific microbial species, some of which become more populous with age at the expense of beneficial microbes. The results noted here are an example of the output of this sort of research. Ultimately, this will lead to more deterministic ways of adjusting the gut microbiome in older individuals. At present the most effective approach is to transplant a fecal sample from a young individual, sidestepping our comparative ignorance of the fine details. It should be possible to improve upon this, however, given greater understanding of the interaction between the gut microbiome and the brain.

Evidence is accumulating that the gut microbiomes in people with Alzheimer's disease can differ from those of healthy people. But it isn't clear whether these differences are the cause or the result of the disease - or both - and what effect altering the microbiome might have on the course of the disease. To determine whether the gut microbiome may be playing a causal role, the researchers altered the gut microbiomes of mice predisposed to develop Alzheimer's-like brain damage and cognitive impairment.

When such genetically modified mice were raised under sterile conditions from birth, they did not acquire gut microbiomes, and their brains showed much less damage at 40 weeks of age than the brains of mice harboring normal mouse microbiomes. When such mice were raised under normal, nonsterile conditions, they developed normal microbiomes. A course of antibiotics at 2 weeks of age, however, permanently changed the composition of bacteria in their microbiomes. For male mice, it also reduced the amount of brain damage evident at 40 weeks of age.

Further experiments linked three specific short-chain fatty acids - compounds produced by certain types of gut bacteria as products of their metabolism - to neurodegeneration. All three of these fatty acids were scarce in mice with gut microbiomes altered by antibiotic treatment, and undetectable in mice without gut microbiomes. These short-chain fatty acids appeared to trigger neurodegeneration by activating immune cells in the bloodstream, which in turn somehow activated immune cells in the brain to damage brain tissue. When middle-aged mice without microbiomes were fed the three short-chain fatty acids, their brain immune cells became more reactive, and their brains showed more signs of tau-linked damage.

Link: https://www.eurekalert.org/news-releases/976371

You may recall the work linking DNA double strand break repair to epigenetic changes characteristic of aging. Repeated cycles of this repair cause some form of depletion of necessary factors or other disarray in the mechanisms controlling gene expression. This is a compelling way to link random DNA damage, largely occurring in parts of the genome that are inactive in any given cell, largely occurring in cells that will not go on to divide many times, and occurring in completely different locations from cell to cell, to a consistent, characteristic aspect of aging. Beyond the question of cancer risk, the only other compelling way to connect stochastic DNA damage to the general declines of aging is to consider somatic mosaicism emerging as a result of mutational damage to stem cells, as that mutation spreads throughout a tissue.

In today's materials, researchers describe a way to accelerate this epigenetic change caused by repair of breaks in DNA, and characterize a mouse lineage engineered to undergo a great deal of DNA damage, but damage that occurs only in inactive portions of the genome, and should thus produce no harm to the genomic information needed for cell function. The result appears to be accelerated aging, occurring though the mechanism of epigenetic change noted above. This allows researchers to more readily test the use of partial reprogramming as a means to reverse this epigenetic change, and better understand how this reversal works.

As ever, one should be cautious about declaring models that focus on just one mechanism of aging to actually exhibit accelerated aging. Any form of biological damage run amok, such as occurs for DNA damage in progeroid syndromes, can produce outcomes that bear a strong resemblance to normal aging - but they are not normal aging. The details as to how exactly they are different are important when it comes to drawing conclusions from these models about the best approaches to treating aging. It is a little early in the research into DNA repair and epigenetic change for a good understanding as to how this sort of model will differ from normal aging, as researchers have for progeroid mice.

Loss of Epigenetic Information Can Drive Aging, Restoration Can Reverse It

A component of epigenetics is the physical structures such as histones that bundle DNA into tightly compacted chromatin and unspool portions of that DNA when needed. Genes are inaccessible when they're bundled up but available to be copied and used to produce proteins when they're unspooled. Thus, epigenetic factors regulate which genes are active or inactive in any given cell at any given time. By acting as a toggle for gene activity, these epigenetic molecules help define cell type and function. Since each cell in an organism has basically the same DNA, it's the on-off switching of particular genes that differentiates a nerve cell from a muscle cell from a lung cell.

The team's main experiment involved creating temporary, fast-healing cuts in the DNA of lab mice. These breaks mimicked the low-grade, ongoing breaks in chromosomes that mammalian cells experience every day in response to things like breathing, exposure to sunlight and cosmic rays, and contact with certain chemicals. In the study, to test whether aging results from this process, the researchers sped the number of breaks to simulate life on fast-forward. The team also ensured that most of the breaks were not made within the coding regions of the mice's DNA - the segments that make up genes. This prevented the animals' genes from developing mutations. Instead, the breaks altered the way DNA is folded.

The researchers called their system ICE, short for inducible changes to the epigenome. At first, epigenetic factors paused their normal job of regulating genes and moved to the DNA breaks to coordinate repairs. Afterward, the factors returned to their original locations. But as time passed, things changed. The researchers noticed that these factors got "distracted" and did not return home after repairing breaks. The epigenome grew disorganized and began to lose its original information. Chromatin got condensed and unspooled in the wrong patterns, a hallmark of epigenetic malfunction. As the mice lost their youthful epigenetic function, they began to look and act old. The researchers saw a rise in biomarkers that indicate aging. Cells lost their identities as, for example, muscle or skin cells. Tissue function faltered. Organs failed.

Next, the researchers gave the mice a gene therapy that reversed the epigenetic changes they'd caused. The therapy delivered a trio of genes - Oct4, Sox2, and Klf4, together named OSK - that are active in stem cells and can help rewind mature cells to an earlier state. The ICE mice's organs and tissues resumed a youthful state. The therapy set in motion an epigenetic program that led cells to restore the epigenetic information they had when they were young. How exactly OSK treatment achieved that remains unclear. At this stage, the discovery supports the hypothesis that mammalian cells maintain a kind of backup copy of epigenetic software that, when accessed, can allow an aged, epigenetically scrambled cell to reboot into a youthful, healthy state.

Loss of epigenetic information as a cause of mammalian aging

All living things experience an increase in entropy, manifested as a loss of genetic and epigenetic information. In yeast, epigenetic information is lost over time due to the relocalization of chromatin-modifying proteins to DNA breaks, causing cells to lose their identity, a hallmark of yeast aging. Using a system called "ICE" (inducible changes to the epigenome), we find that the act of faithful DNA repair advances aging at physiological, cognitive, and molecular levels, including erosion of the epigenetic landscape, cellular exdifferentiation, senescence, and advancement of the DNA methylation clock, which can be reversed by OSK-mediated rejuvenation. These data are consistent with the information theory of aging, which states that a loss of epigenetic information is a reversible cause of aging.

Studies of the variance in human longevity due to genetics and environment are a matter of chasing small effect sizes, modest increases in the (still low) odds of living to extreme old age, and trying to distinguish those effects from the much larger impact of lifestyle choices and wealth. It isn't an easy endeavor, and at the end of the day small effect sizes are not the starting point from which to build ways to meaningfully extend the healthy human life span. Nonetheless, there is a great deal of this sort of research out there, interesting in its own right, but not the road to the future. The example here focuses on trace elements in drinking water, and might be compared with similar work focused on lithium intake via drinking water.

Longevity, as a complex life-history trait, shares an ontogenetic relationship with other quantitative traits, such as epigenetic and environmental factors. Therefore, it is important to identify environmental factors that may modify the epigenome to establish healthy aging. This study explored the association between tap drinking water and longevity in Cilento, Italy, to understand whether trace elements in local drinking water may have an influence on old, nonagenarian, and centenarian people and promote their health and longevity.

Data on population and water sources were collected through the National Demographic Statistics, the Cilento Municipal Archives, and the Cilento Integrated Water Service. Ordinary least squares (OLS) regression and a geographically weight regression (GWR) model were used to study the spatial relationship between the explanatory and outcome variables of longevity.

The results of the study showed that the prevalence of longevity is concentrated in the central, northern and southeastern areas of the territory and that some trace elements present in tap water may contribute to local longevity in Cilento. Specifically, all Cilento municipalities had alkaline tap water, and the municipalities with the highest longevity concentrations had higher alkalinity levels than the other municipalities, soft to medium-hard water hardness, an amount of total dissolved solids equivalent to the level of excellent water, lower amounts of sodium, adequate iron concentration, and adequate dietary intake of manganese per day.

Link: https://doi.org/10.3390/nu15010218

Upregulation of BDNF is a useful goal, as it produces greater neurogenesis in the brain. Neurogenesis, the production of new neurons from neural stem cells, and their integration into neural circuits, is important in memory, learning, and the resilience of the brain to damage and aging. Increased levels of BDNF may also improve metabolism and reduce inflammation in brain tissue. BDNF levels decline with age, but evidence suggests that BDNF expression can be boosted via calorie restriction and exercise. Researchers here compare these approaches for effectiveness, finding that short bursts of high intensity exercise produce the best outcome.

The specialised protein named brain-derived neurotrophic factor (BDNF) promotes neuroplasticity (the ability of the brain to form new connections and pathways) and the survival of neurons. Animal studies have shown that increasing the availability of BDNF encourages the formation and storage of memories, enhances learning, and overall boosts cognitive performance. These key roles and its apparent neuroprotective qualities have led to the interest in BDNF for ageing research.

To tease apart the influence of fasting and exercise on BDNF production researchers compared the following factors to study the isolated and interactive effects: (a) fasting for 20 hours; (b) light exercise (90-minute low intensity cycling); (c) high-intensity exercise (six-minute bout of vigorous cycling); and (d) combined fasting and exercise. Twelve physically active participants (six males, six females aged between 18 and 56 years) took part in the study. The researchers found that brief but vigorous exercise was the most efficient way to increase BDNF compared to one day of fasting with or without a lengthy session of light exercise. BDNF increased by four to five-fold (396 pg/L to 1170 pg/L) more compared to fasting (no change in BDNF concentration) or prolonged activity (slight increase in BDNF concentration, 336 pg/L to 390 pg/L).

The cause for these differences is not yet known and more research is needed to understand the mechanisms involved. One hypothesis is related to the cerebral substrate switch and glucose metabolism, the brain's primary fuel source. The cerebral substrate switch is when the brain switches its favoured fuel source for another to ensure the body's energy demands are met, for example metabolising lactate rather than glucose during exercise. The brain's transition from consuming glucose to lactate initiates pathways that result in elevated levels of BDNF in the blood. The observed increase in BDNF during exercise could be due to the increased number of platelets (the smallest blood cell) which store large amounts of BDNF. The concentration of platelets circulating in the blood is more heavily influenced by exercise than fasting, and increases by 20%.

Link: https://www.eurekalert.org/news-releases/976126

Parkinson's disease is characterized by aggregation of α-synuclein, one of a number of harmful protein aggregates that form and spread in the aging brain. At present, it is thought that in many patients this process of aggregation starts in the intestines rather than in the brain. So it is perhaps not that surprising to find that alterations in the balance of microbial populations in the gut microbiome are characteristic of Parkinson's disease. Researchers have been looking into correlations between the microbiome and various age-related diseases with increasing energy for some years now.

Exactly how the gut microbiome contributes to Parkinson's is yet to be established. It may be as simple as the consequence of increased inflammatory signaling as populations of harmful microbes grow in number. That is an attractive argument, given the disruptive nature of chronic inflammation, but wagering on a biological process turning out to be simple is rarely a winning proposition. Regardless of underlying mechanisms, given that the state of the microbiome can be both measured via 16S rRNA sequencing and radically adjusted via fecal microbiota transplantation, there is the possibility of (a) effective screening for risk of Parkinson's, and perhaps (b) effective prevention via restoration of a healthy balance of microbial populations.

New study puts gut microbiome at the center of Parkinson's disease pathogenesis

Investigators employed metagenomics, the study of genetic material recovered directly from the stool microbiome of persons with Parkinson's disease (PD) and neurologically healthy control subjects. Investigators found an overabundance of opportunistic pathogens and immunogenic components, which suggest infection and inflammation at play, overproduction of toxic molecules, and overabundance of the bacterial product curli. This induces PD pathology and dysregulation of neurotransmitters, including L-dopa. At the same time, there was a shortage of neuroprotective molecules and anti-inflammatory components, which makes recovery difficult.

The researchers studied 257 species of organisms in the microbiome, and of these, analysis indicated 84, more than 30 percent, were associated with Parkinson's disease. Of the 84 PD-associated species, 55 had abnormally high abundance in persons with PD, and 29 were depleted. At one end of the spectrum, Bifidobacterium dentium was elevated by sevenfold, Actinomyces oris by 6.5-fold and Streptococcus mutans by sixfold. At the other end of the spectrum, Roseburia intestinalis was reduced by 7.5-fold and Blautia wexlerae by fivefold.

"Undoubtedly more information will be revealed as we increase the sample size and others also conduct metagenomics studies and share the data. We anticipate that in the near future we will have the tools and the analytic power to use metagenomics as a new approach to study PD heterogeneity, search for biomarkers, delve deeper into the origin and progression of PD sub-phenotypes, and investigate the potential in manipulating the microbiome to prevent, treat and halt the progression of PD."

Metagenomics of Parkinson's disease implicates the gut microbiome in multiple disease mechanisms

Parkinson's disease (PD) may start in the gut and spread to the brain. To investigate the role of gut microbiome, we conducted a large-scale study, at high taxonomic resolution, using uniform standardized methods from start to end. We enrolled 490 PD and 234 control individuals, conducted deep shotgun sequencing of fecal DNA, followed by metagenome-wide association studies to declare disease association, network analysis to identify polymicrobial clusters, and functional profiling.

Here we show that over 30% of species, genes, and pathways tested have altered abundances in PD, depicting a widespread dysbiosis. PD-associated species form polymicrobial clusters that grow or shrink together, and some compete. PD microbiome is disease permissive, evidenced by overabundance of pathogens and immunogenic components, dysregulated neuroactive signaling, preponderance of molecules that induce alpha-synuclein pathology, and over-production of toxicants; with the reduction in anti-inflammatory and neuroprotective factors limiting the capacity to recover.

The many aspects of degenerative aging arise from a smaller set of common underlying processes of damage, giving rise to a web of interacting consequences. It can be hard to pin down the chains of cause and effect, and the degree to which any one contributing cause is responsible for the end result, but nonetheless many aspects of aging correlate with one another for the simple reason that the root causes are much the same. This can be the case even when degeneration occurs in very different bodily systems. For example, as shown here, loss of sense of smell and general physical frailty show a correlation.

To examine the relationship between frailty and olfaction, the research team analyzed data from 1,160 older adults enrolled in the National Social Life, Health and Aging Project between 2015 and 2016. The mean age of subjects was 76 and 55.7% were female. Participants were exposed to five scents to measure olfactory identification and six scents to measure sensitivity levels. Results were then matched to a subject's frailty score.

Researchers concluded that for every one-point increase in both olfactory identification and sensitivity scores, there was a significant and meaningful reduction in frailty status, implying that improvements in smell were associated with improved health status and resilience of older results. Conversely, the worse the sense of smell, the frailer a subject was, suggesting that smell loss can be a measurable biomarker and potential risk factor for frailty in older adults.

Although these findings in older adults add to a body of literature that suggests the sense of smell can be a bellwether of frailty and impending mortality, the relationship of these unique sensory losses with unhealthy aging over time is unclear. Common consequences of smell loss include a loss of appetite, difficulty monitoring personal hygiene, depression, and an inability to detect toxic fumes. In older adults, this may be associated with weight loss, malnutrition, weakness, inadequate personal care, and even potential injuries caused by gas leaks or fires.

Link: https://www.hopkinsmedicine.org/news/newsroom/news-releases/the-nose-knows-study-suggests-it-may-be-wise-to-screen-for-smell-loss-to-predict-frailty-and-unhealthy-aging-1

The Longevity Escape Velocity Foundation (LEVF) is initially working to assess combinations of approaches to the treatment of aging, to assess the degree to which mouse life span is affected. Aging consists of many distinct mechanisms, and comprehensive rejuvenation will require a diverse package of therapies. Yet the research and development community undertakes little work on combined treatments. Here, the Lifespan.io team talks to Aubrey de Grey about some of the details of the work presently under way.

We are obviously very excited about LEVF's robust mouse rejuvenation (RMR) project. Could you walk our readers through its design and goals?

This is envisioned as a rolling research program aiming to increase both the mean and maximum lifespan of mice by at least 12 months with various combination therapies started late in life. For the first study, four therapies have been chosen: rapamycin, a senolytic, hematopoietic stem cell transplantation (HSCT), and telomerase expression. I believe we'll have two outcomes. One of them scientific, and the other more, if you like, rhetorical. We want to get mice to live a lot longer than they do now: at least a year longer, starting the treatment or treatments only after middle age. The idea is that this will appeal more directly to people who care, vote, pay taxes, and make donations than if you do early-onset interventions. So, I decided to put numbers on this, to have a milestone that clearly says this is where we want to get to. We believe this will be a sufficiently dramatic result.

With such a lofty goal at hand, would you like to make some predictions about the results? For instance, which interventions or combinations are more likely to succeed?

Definitely not. Let's be clear: I do not actually have lofty expectations for this first experiment. We've been saying from the beginning that this is a rolling research program, and our top priority is, as soon as we get this one kicked off, we're going to design the next one, and to bring in the money, which is about three million dollars for each round. So, no, I have no idea what we're going to get with this one, but I'm hoping that we'll be able to do subsequent rounds more than once a year - maybe every nine months or so - because we don't need to wait for the results of the first one to decide how to do the second one. We're also incorporating masses of information from the community, from literature, and we already have a plenty good list of things that we'd like to try in the next round.

Have you decided on what senolytic will be used?

Yes, we just decided on it. We're going to use conjugated navitoclax. As you probably know, navitoclax has a reputation as a reasonably good senolytic. However, it's not very specific. But researchers had this extraordinarily simple and brilliant idea based on the fact that most senescent cells have a high expression of beta-galactosidase. You covalently attach galactose to the molecule in a location that makes the molecule not work. But because it's galactose, if the cell is producing beta-galactosidase, galactose will be cleaved off in senescent cells and only in senescent cells.

What will you be measuring?

We're going to measure all sorts of stuff in addition to lifespan. We will focus heavily on function with tests such as the rotarod, so that we have good information on healthspan. We'll be doing that in different ways. First, we'll have a bunch of non-invasive things that measure agility, visual acuity, physical appearance, including alopecia and kyphosis (the bending of the spine). These are well-established measures of biological age. In addition, we will be sacrificing some mice at various periods during the study and asking what condition they're in. On top of that, we will be looking at mice that die naturally during the experiment and figuring out what they died of. So, we're really covering all the bases.

Link: https://www.lifespan.io/news/aubrey-de-grey-on-levf-and-robust-mouse-rejuvenation/

Age-related changes in the structure of the extracellular matrix that surrounds and supports cells are not as well studied as changes in cell behavior. Nonetheless, there is plenty of evidence for changes in the extracellular matrix to negatively affect tissue function. Cells create and maintain the matrix, but the state of the matrix in turn influences cells, and over time is affected by more than just cell behavior. Metabolic processes can alter and fragment elastin, cross-link collagen molecules, and so forth.

Cross-linking of matrix molecules occurs with age as a byproduct of the normal operation of metabolism, reducing flexibility and increasing stiffness. Targeting this cross-linking is a field still in its infancy, and only a few lines of research and development have made significant progress. Clinical trials of cross-link breaking in the lens of the eye have been undertaken, but this chemistry isn't relevant to the rest of the body. Some inroads have been made on finding ways to break down the persistent glucosepane cross-links that appear to be the most relevant to human extracellular matrix aging elsewhere in the body, but despite the launch of a company, Revel Pharmaceuticals, to develop these candidate treatments, there is still a long road ahead.

New mechanism uncovered behind osteoarthritis could inform new treatments

Osteoarthritis occurs when cartilage in a joint stiffens and begins to break down which then damages the underlying bone, resulting in pain, swelling and feelings of stiffness. There are currently no treatments to reverse this cartilage stiffening and resulting damage. Much has remained unknown about the molecular causes of this damage and how to treat it. These unknowns are especially germane to knee osteoarthritis, where no single event causes the cartilage damage, and the greatest predictive risk factor is aging.

Using advanced mass spectrometry technology, the researchers mapped out the trajectory of structural and protein changes in mice with knee osteoarthritis over the course of their lifetimes and according to sex. They then compared their findings to the current understanding of knee osteoarthritis in humans. The researchers found that Klotho was heavily involved in the molecular process that led to osteoarthritis. This work was an extension of previous studies showing that Klotho protects mitochondria within skeletal muscle and plays a key role in skeletal muscle regeneration following injury. As people age, their klotho levels go down, hence why it's referred to as a longevity protein.

The new analysis revealed that when knee cartilage tissue became stiffer, the gene that codes for Klotho was repressed. They verified this in models of young and old chondrocyte cells responsible for cartilage formation, which were seeded in environments designed to mimic young and old tissue stiffness. Young chondrocyte cells looked old when put on a stiff surface due to the loss of Klotho, but when the researchers protected the cells from the stiffness in their environment, they observed chondrocyte health.

Age-related matrix stiffening epigenetically regulates α-Klotho expression and compromises chondrocyte integrity

Extracellular matrix stiffening is a quintessential feature of cartilage aging, a leading cause of knee osteoarthritis. Yet, the downstream molecular and cellular consequences of age-related biophysical alterations are poorly understood. Here, we show that epigenetic regulation of α-Klotho represents a novel mechanosensitive mechanism by which the aged extracellular matrix influences chondrocyte physiology. Using mass spectrometry proteomics followed by a series of genetic and pharmacological manipulations, we discovered that increased matrix stiffness drove Klotho promoter methylation, downregulated Klotho gene expression, and accelerated chondrocyte senescence in vitro.

In contrast, exposing aged chondrocytes to a soft matrix restored a more youthful phenotype in vitro and enhanced cartilage integrity in vivo. Our findings demonstrate that age-related alterations in extracellular matrix biophysical properties initiate pathogenic mechanotransductive signaling that promotes Klotho promoter methylation and compromises cellular health. These findings are likely to have broad implications even beyond cartilage for the field of aging research.

Skin heals poorly in old people, the consequence of mechanisms of aging such as the growing number of senescent cells present in aged tissues. Senescent cells are normally generated for a short period of time during wound healing and their pro-growth, pro-inflammatory signals help to coordinate the intricate dance of cell populations involved in regrowth following injury. The constant presence of senescent cells and their signals is disruptive to the healing process, however. As noted in this review paper, a number of other mechanisms are also relevant to the declining capacity for regeneration of skin in older people.

Skin is the human's largest organ and consists of three distinctive layers, the epidermis, dermis, and hypodermis. Skin is equipped with an innate immune response towards tissue injury, with the aim to restore normal tissue structure and function. The normal wound healing process comprises three distinctive stages, inflammation, reepithelialization, and tissue remodelling. The balance between inflammation and its control is essential to maintain a normal wound healing process. This is because acute inflammation at the early stage of wound healing is beneficial in removing cell debris and invading microbes. However, if the inflammation state is prolonged, this will lead to further destruction of adjacent cells and eventually inhibit wound healing.

Aging causes more platelets to adhere to the injured epithelium. This will cause the production of more pro-inflammatory cytokines such as PDGF, TGF-β, and TGF-α. In response to their release, neutrophils will rapidly be recruited to the site of injury. Simultaneously, monocytes will also be recruited to the site of injury. However, since monocytes are larger in size, they require specific adhesion molecules such as ICAM-1 and VCAM-1 to be expressed on the endothelial surface in order to infiltrate the site of injury. In aged skin, these adhesion molecules are greatly reduced, and this impairs the monocyte infiltration.

Reactive oxygen species (ROS) also have an important role in the wound healing process. They are produced by neutrophils and macrophages via NADPH oxidase and help in killing microbes and preventing wound infection. They also have a role as a vasoconstrictor to help reduce blood flow and promote thrombus formation soon after injury. Oxidative stress is also necessary for transition into the proliferative phase. A low amount of ROS provides positive effects on wound healing, whereas prolonged exposure to ROS has a detrimental effect on the wound healing process. Increased production of ROS, such as nitric oxide and superoxide anions, will increase tissue damage and impair healing. In aged skin, more ROS will accumulate due to prolonged inflammation. Hence, this will prolong the state of oxidative stress.

Aged skin will usually have damaged and impaired growth of blood vessels. Once the microcirculation is impaired, there are changes in the inflammatory response due to a reduction in the inflammatory cells and chemical mediators being able to reach the site of injury. On top of that, it also means that there is a relative hypoperfusion at the injury site, leading to less nutrients and oxygen being able to be supplied to support the wound healing process. Temporary hypoxia is important in wound healing process as it can stimulate the release of cytokines and growth factors to induce cell proliferation, migration, as well as angiogenesis. However, a prolonged hypoxia state will negatively affect the wound healing process.

Link: https://doi.org/10.3390/life12122142

Transposable elements are largely the remnants of ancient viral infections, DNA sequences capable of copying themselves within the genome via a number of different mechanisms. Transposable elements are suppressed in youth, but this suppression breaks down with age, and the resulting disruptive activity may provide a meaningful contribution to degenerative aging. Separately, researchers are finding that transposable elements are active in senescent cells, and contribute to some of the behaviors that make lingering senescent cells harmful in aged tissues, as noted in this paper.

Silent long-interspersed element-1 (LINE1) retrotransposons, belonging to non-long terminal repeat (non-LTR) retrotransposons, can be activated during senescence, triggering the innate immune response that is responsible for part of the senescence-associated phenotypes. A different class of retroelements, endogenous retroviruses (ERVs), belonging to LTR retrotransposons are a relic of ancient retroviral infection, fixed in the genome during evolution, comprising about 8% of the human genome. As a result of evolutionary pressure, most human ERVs (HERVs) accumulate mutations and deletions that prevent their replication and transposition function. However, some evolutionarily young subfamilies of HERV proviruses, such as the recently integrated HERVK human mouse mammary tumor virus like-2 (HML-2) subgroup, maintain open reading frames encoding proteins required for viral particle formation.

Except at specific stages of embryogenesis when DNA is hypomethylated and under certain pathological conditions such as cancer, HERVs are transcriptionally silenced by host surveillance mechanisms such as epigenetic regulation in post-embryonic developmental stages. Notably, whether ERVs can escape host surveillance during aging and, if so, what effects they may exert on cellular and organismal aging are still poorly investigated.

In this study, using cross-species models and multiple techniques, we revealed an uncharacterized role of endogenous retrovirus resurrection as a biomarker and driver for aging. Specifically, we identified endogenous retrovirus expression associated with cellular and tissue aging and that the accumulation of HERVK retrovirus-like particles (RVLPs) mediates the aging-promoting effects in recipient cells. These HERVK RVLPs constitute a transmissible message to elicit senescence phenotypes in young cells, which can be blocked by neutralizing antibodies. We can thus inhibit endogenous retrovirus-mediated pro-senescence effects to alleviate cellular senescence and tissue degeneration in vivo, suggesting possibilities for developing therapeutic strategies to treat aging-related disorders.

Link: https://doi.org/10.1016/j.cell.2022.12.017

Perhaps the most important early measure of the quality of a given approach to the treatment of aging is its effect on remaining life span in old mice. Prevention is a good approach, but it has the disadvantage of only working to its greatest effect in those who are not yet old. The best approaches to the treatment of aging will produce rejuvenation, and thus be applicable to both (a) prevention of degenerative aging in people who are entering later life and (b) reversal of degenerative aging in those already suffering its effects. Reversal of the cell and tissue damage that causes aging, when periodically applied prior to the worst pathology of aging, is prevention. Allowing mice to age into dysfunction followed by application of a therapy to restore health and extend life is a good indication that the therapy is producing rejuvenation.

In today's preprint paper, researchers outline an interesting approach to partial reprogramming, a way to restore a more youthful pattern of gene expression in the cells present in aged tissue. Evidence to date suggests that widespread partial reprogramming in most tissues is beneficial. The research employed an adeno-associated virus (AAV)-mediated gene therapy to introduce a conditional construct into the cells of aged mice, allowing the expression of Yamanaka factors in response to oral administration of the antibiotic doxycycline. Partial reprogramming could therefore be induced intermittently in all of the cells transduced by the AAV vector for the remainder of the mouse life span. The researchers used AAV9, an AAV variant that tends to give decent coverage of the major organs at the dose used in this study. The result was a doubling of remaining life span in the treated mice. This was a small study, 20 mice to a group, but the size of the outcome is large, a compelling result.

The intravenous AAV dose used here was at the high end of the practical and safe range for mice, and there have been deaths in human clinical trials at an equivalent dose. It puts stress on the liver, for example. AAV as it stands is a poor choice for uses that will require high dose systemic administration in large numbers of older patients, for a variety of logistical and regulatory reasons. There must be improvements to the AAV technology, or better gene therapy options must arise to replace it. Some lipid nanoparticles (LNPs) show promise, but they must be coupled with a payload able to reliably deliver genetic machinery into the cell nucleus. Many lines of work seem potentially able to solve one or other of these challenges, but none have as yet reached the goal to become both robustly functional and readily available for other projects.

One of the ways in which we will come to see improvement in gene therapy technologies is the continued demonstration in animal studies of ever more compelling outcomes that can be achieved via their use. Sizeable extension of remaining life span in old mice, achieved via use of a hot-topic technology currently backed by billions in funding for research and development, is likely to draw increased investment in ways to deliver the important advance of a gene therapy capable of cost-effective, safe-enough whole body introduction of long-lasting genetic additions.

Gene Therapy Mediated Partial Reprogramming Extends Lifespan and Reverses Age-Related Changes in Aged Mice

Using a cocktail of transcription factors, OCT4 (O), SOX2 (S), KLF4 (K), and c-MYC (M), collectively known as OSKM or Yamanaka factors, seminal studies showed that somatic cells can be reversed to a pluripotent state, thereby reversing a long-held paradigm of unidirectional differentiation. By short or cyclic induction of the Yamanaka factors in transgenic mice, investigators have demonstrated age extension in progeroid mice. These transgenic mouse models encoded a polycistronic OSKM cassette driven by a reverse tetracycline transactivator (rtTA) (4F mice); cyclic administration of doxycycline led to partial reprogramming without teratoma formation. This paradigm partially ameliorated aging phenotypes and extended the lifespan in the 4F-progeroid model. The study further showed that the epigenetic profile assessed by epigenetic methylation clocks of tissues, correlated with improved function.

The translation of these proof-of-concept genetic studies toward therapeutic interventions is to benefit the increasingly large aging population. In support of this endeavor, we have generated a systemically delivered two-part AAV9 system with doxycycline-inducible OSK, where one vector carried a constitutively expressed rtTa and the other vector contained a polycistronic OSK expression cassette driven by doxycycline responsive TRE promoter. We selected AAV9 capsid to ensure maximal distribution to most tissues. We injected 124-week-old wild type C57BL6/J mice retro-orbitally with 100 μl containing either PBS or 1E12 viral particles of each vector. We initiated the doxycycline induction for both the control and AAV administered groups the day after injections and alternated weekly on/off cycles for the remainder of the animals' lives.

Intriguingly, we observed a 109% extension in median remaining life in response to OSK expression (control mice had 8.86 weeks of life remaining vs. 18.5 weeks for TRE-OSK mice). Doxycycline-treated control mice had a median lifespan of ∼133 weeks, while the TRE-OSK mice had a median lifespan of 142.5 weeks. We observed a significant reduction in the frailty index from 7.5 points for doxycycline treated control mice to 6 points for TRE-OSK mice, suggesting that increased lifespan correlated to overall better health of the animals. We isolated DNA from heart and liver tissue from control and TRE-OSK treated mice at time of death and found that the Lifespan Uber Clock (LUC) for both liver and heart trended towards reduced epigenetic age.

This short overview skims recent work on the role of ADAR1 expression in aging. Levels of ADAR1 are reduced with age in many tissues, and this may affect a number of processes relevant to aging, such as cellular senescence. ADAR1 edits RNA, affecting the behavior of gene expression at a very low level. It is a good example of a protein that is thus involved in many, many processes in the cell, and which has indirect effects on any number of cell behaviors. It is exceptionally challenging to pin down specific important roles for such proteins. There is such a large space of possibilities to cover that decades of work may or may not arrive at the crucial realizations and studies that turn out to demonstrate a possible way forward to intervene in aging.

Researchers recently published five papers on the function and molecular mechanism of ADAR1 (adenosine deaminases acting on RNA) in aging, cancer, and autoimmune diseases. Four of the papers revealed that ADAR1 regulates autoimmune disease and cancer immunotherapy through canonical adenosine-to-inosine (A-to-I) RNA editing. Using a different approach, the fifth paper discovered that ADAR1 could suppress cellular senescence by regulating p16INK4a expression through an RNA editing independent pathway.

Researchers found that ADAR1 could promote the interaction between human antigen R (HuR) and SIRT1 mRNA, thereby increasing the stability of SIRT1 mRNA. The elevated SIRT1 expression, in turn, suppresses the translation of p16INK4a mRNA, thus inhibiting the occurrence of senescence. However, in aging cells, ADAR1 is degraded by lysosomal-mediated autophagy. Researchers found that the protein level of ADAR1 in the brain, ovary, and other tissues of aging mice was significantly lower than that of young mice. Because the ADAR1 mRNA expression level did not change significantly, this result indicates that the down-regulation of ADAR1 expression during aging mainly happened at the post-transcriptional level.

The researchers also found that applying small molecule inhibitors targeting the lysosomal autophagy pathway in aging cells could inhibit the loss of ADAR1 expression due to aging. Overall, the study revealed a novel mechanism of autophagy in promoting aging and indicated that the altered ADAR1 expression might be a biomarker of aging. Importantly, modulating ADAR1 expression levels may be potent in treating aging-related diseases.

Link: https://doi.org/10.1038/s41392-022-01276-5

The author of this commentary is overly critical of the science of rejuvenation as a whole, if one takes a tour of his work, but here he makes legitimate points about the harms done by an excess of hype. He picks on one of the easier targets, the publicity that David Sinclair has generated for his work, initially on sirtuins and later on reprogramming, with which it is fairly easy to find issues. Raising awareness, marketing potential programs, is a necessary evil in the matter of directing funding into new fields, but unrealistic promises sustained over time become damaging.

Is aging treatable? In the sense that the rate of aging can be modified by genes and the environment, yes. However, aging is easy to accelerate, i.e. by smoking, overweight, infectious diseases, and other factors, and much harder to slow. Do sirtuins extend lifespan in yeast, invertebrates and vertebrates? Has David Sinclair discovered sirtuin activators? Based on 25 years of work by academic and industrial investigators, the clear answer to both questions is no. Whereas Sinclair claims that sirtuins are dominantly acting longevity genes from yeast to humans, early reports of sirtuins extending lifespan in invertebrates could not be independently replicated. In 2011, researchers from 7 institutions published together that sirtuin genes do not extend lifespan in worms or flies.

Sinclair's theories were au courant for two decades. Indeed, sirtuins and resveratrol have been subjects of hundreds of stories in the mass media. A 2008article reported that sirtuin activators would be developed as diabetes medications that, as a side effect, would extend lifespan. The global interest in sirtuins and sirtuin activators was such that companies - most notably GSK - spent many billions of dollars trying to get a positive result and could not because the so-called sirtuin activators do not activate sirtuins and because sirtuins are not longevity genes. Sinclair's book Lifespan therefore represents a pivot in which a person central to the failure of the largest longevity medicine program in pharmaceutical history turns to the general public to retell his story. In the retelling, sirtuins are longevity genes and sirtuin activators are real.

Link: https://doi.org/10.1016/j.archger.2022.104825

Here find the first draft of a proposal regarding the best way forward at the present time to accelerate progress towards the development of diverse, effective rejuvenation therapies. The key is to use philanthropic funding to (a) prove efficacy in low-cost clinical trials, and then (b) market that data to ensure physician adoption of the first working rejuvenation therapies. A PDF version of this draft also exists.

Executive Summary

1. Aging is by far the greatest cause of human morbidity and mortality.

2. Rejuvenation therapies that will greatly reduce unnecessary late life suffering and death are under development, but slowly, and with limited funding.

3. Accelerating the development of rejuvenation therapies is an important goal that, if achieved, will improve quality of life and save many lives in the years ahead.

4. At present there is only limited public support for the goal of human rejuvenation.

5. Faster progress towards rejuvenation therapies will follow greater public and institutional support for rejuvenation therapies. It will mean more funding, more research programs, more biotech companies.

6. A few low-cost rejuvenation therapies exist today, already approved by US regulators for other uses. They can in principle be prescribed off-label in the US, but are not yet widely used.

7. Broad public and institutional support to accelerate the development of rejuvenation therapies will emerge following the widespread use of at least a few rejuvenation therapies.

8. Widespread use of the first rejuvenation therapies requires physician adoption of those therapies, as patients largely follow the options presented by physicians.

9. Physician adoption of an off-label rejuvenation therapy requires a convincing presentation of safety and efficacy in the treatment of common age-related conditions. This can be provided by favorable results from low-cost, few-hundred-patient clinical trials conducted by a reputable organization, and then marketed to physicians and physician organizations.

10. The cost of clinical trials to produce robust, trustworthy data for an existing therapy, already approved by regulators, can be a fraction of that required for clinical trials aimed at regulatory approval of a new treatment.

11. Given this funding, a number of existing organizations are well placed to conduct these trials and publicize the results. All that is needed is the will to act.

Aging is the Greatest Cause of Human Morbidity and Mortality

Age-related disease is by far the greatest cause of human morbidity and mortality. The many different ultimately fatal degenerative conditions of old age result from a much smaller number of underlying mechanisms of aging. These include the accumulation of senescent cells and forms of metabolic waste such as cross-links and amyloids, DNA damage, and more. [1][2]

The First Rejuvenation Therapies Exist ...

Historically, treatments for age-related disease have focused on the symptoms rather than the causes, and thus comparatively little headway has been made towards prevention and reversal - towards actual rejuvenation. Even though this remains true today, it is nonetheless the case that the first rejuvenation therapies exist, each capable of reversing to some degree a single contribution to degenerative aging.

For example, the senolytic combination of dasatinib and quercetin has been shown in human clinical trials to significantly reduce the burden of senescent cells in aged tissues following a single course of treatment. [3] Senescent cells grow in number with age, and their inflammatory secretions are disruptive of tissue structure and function, contributing to many of the common fatal age-related diseases. [4] Dasatinib is an FDA-approved drug that can be prescribed off-label at low cost, while quercetin is a supplement, readily available to all at an even lower cost.

As a second example, fecal microbiota transplant (FMT) from young to old individuals has been demonstrated in animal studies to produce a lasting reset of the aged gut microbiome and improved health. [5][6] Restoring the balance of microbial populations in the intestine to a youthful state reduces the harmful effects of an aged gut microbiome on long-term health, including raised inflammation, increased generation of toxic metabolites, and reduced generation of beneficial metabolites. One implementation of this treatment was recently approved by the FDA for treatment of C. difficile infection. [7] This makes it available off-label, in principle at least, and gives support to the community of practitioners that has for years been conducting FMT procedures on an ad hoc basis to treat various forms of dysbiosis.

... But are Not Widely Adopted

Despite the existence of these rejuvenation therapies, and evidence for their benefits in the context of aging, the two treatments noted above are neither widely used nor widely known. The broader public still sees aging as largely set in stone, and treatment of aging as the domain of frauds and snake oil salesmen. The public does not realize that a small number of low-cost medical therapies can, with a single program of treatment, produce a lasting improvement to late life health by addressing one of the contributing causes of aging. Comparatively few physicians are both aware of these therapies and comfortable prescribing them. Comparatively few research groups are working on human clinical trials that would produce further supporting evidence.

If must be noted that clearance of senescent cells and adjustment of the gut microbiome, while supported by evidence to show them to be individually beneficial, are not on their own sufficient for comprehensive rejuvenation of the old. Other contributing causes of aging must also be addressed, such as protein aggregates, cross-linking, stem cell decline, mitochondrial dysfunction, and so forth. [1] A faction within the biotech industry is working on new classes of rejuvenation therapy, and the funding for this effort has risen to a few billion dollars, spread unevenly across a few score companies. [8] This sounds like a lot, but it is an insignificant fraction of the funding devoted to more mainstream medical development; the end to end cost of developing a single therapy was reportedly more than $2 billion in 2013. [9]

If we wish to see rapid progress towards the effective treatment of aging within our lifetimes, a dramatic reduction of age-related disease, an end to frailty and dementia, then initiatives aimed at the production of rejuvenation therapies must greatly expand in size and number, and do so sooner rather than later. At the large scale, public support and understanding is necessary for the biggest, most conservative institutions to choose to put their shoulders to the wheel and advance the field of rejuvenation research. That support and understanding is missing at present, in large part because the first rejuvenation therapies are not widely used, and therefore remain largely unknown and unappreciated.

The problem we face is circular in nature. Little use of existing rejuvenation therapies means little knowledge of those therapies. Little knowledge in turn ensures little use. Presently sparse research and development means a slow pace of transmission of knowledge from the scientific community to thought leaders and the public at large. That lack of broad knowledge ensures that there is comparatively little support for greater funding and an expanded range of initiatives.

A slow process of bootstrapping is the usual way forward when faced with such self-reinforcing roadblocks, years of slow and incremental growth to open up a new field. There are other, faster ways paths ahead, however, enabled by the cost-effective deployment of philanthropic funding.

To Ensure Adoption, Persuade Physicians to Prescribe

The best way to break the cycle described above is to focus on physician adoption, to ensure that physicians and clinicians become comfortable prescribing and providing the few presently available rejuvenation therapies. Most patients only become familiar with the medical technologies presented by their physicians. Ensuring widespread off-label use by the medical community of the few existing, easily implemented, low-cost rejuvenation therapies would lead to a sizable improvement in public knowledge and attitudes regarding human rejuvenation.

A world in which most physicians routinely prescribe beneficial rejuvenation therapies to older patients is a world in which both the public and larger, conservative institutions will come to support further development of this form of medicine, aimed at ever more effective control of aging and age-related disease. Just as importantly, expanding the use of beneficial rejuvenation therapies is a great good in and of itself, a way to alleviate suffering and mortality in the older population.

Clinical Trial Data Persuades Physicians

The best way to convince physicians that a given FDA-approved treatment can be used off-label to treat many diseases of aging, or aging itself, is for reputable organizations to publish favorable results from multiple human clinical trials that employ the treatment. Such trials do not have to be anywhere near as expensive as the formal clinical trials conducted to persuade the FDA to approve a new therapy, as they do not need to be encumbered by the full set of regulatory concerns. They only need to be well run, such that the data produced is of high quality, and run by organizations with a good reputation, to ensure that the message is heard.

Trials of the few existing rejuvenation therapies are taking place, but only to a limited degree, and very slowly. The Mayo Clinic was one of the first groups to run clinical trials using dasastinib and quercetin in kidney disease [10], pulmonary fibrosis [11], and Alzheimer's disease [12], for example. But only for these few age-related conditions, with a limited budget, and at a sedate pace over years. Data has been published for only two of these trials over the last five years. Much more than the work of this single organization is needed to move the needle when it comes to persuading physicians.

It is possible to run a well-managed clinical trial of a low-cost, FDA-approved therapy in as many as two hundred patents for under $1 million, provided that the primary goal is to produce robust data rather than to satisfy regulators. Consider the PEARL trial for rapamycin [13], for example, which was crowdfunded with under $200,000 in charitable donations [14]. Trials for dasatinib and quercetin treatment or fecal microbiota transplantation need not be that much more expensive.

Existing Organizations Can Administer Clinical Trials

Given philanthropic funding for such trials, a number of reputable organizations are well positioned to undertake the task of trial administration. In practice this requires connections to potential principal investigators and clinics capable of performing the work, project management as the work progresses, and analysis and presentation of the results. Again, this is far less onerous for the type of clinical trial envisaged here than is the case for formal clinical trials conducted for regulatory approval of new therapies.

The non-profit Lifespan.io runs crowdfunding campaigns to support research goals, and has collaborated with AgelessRx [15] to fund and organize the PEARL clinical trial for rapamycin. The non-profit Forever Healthy Foundation [16] performs research analysis and holds conferences, is connected to the Kizoo Technology Ventures fund that invests in biotech companies, and could make the transition to organizing small trials. The LongevityTech investment fund [17] is constructing a network of clinics in a number of different locations for the express purpose of running first-in-human clinical trials for new therapies relevant to aging.

Each of these organizations has an existing reputation that can be built upon and expanded by taking on the task of running clinical trials aimed at persuading physicians to make use of the first rejuvenation therapies worthy of the name.

Outreach to Physicians

Given favorable data and reputable trial-running organizations, outreach to physicians is more or less a solved problem. It only requires funding and effort. Organizations that market therapies to physicians and clinical practices exist, while established physician networks and conferences can act as channels for broader discussion and outreach.

In Summary

The first rejuvenation therapies worthy of the name already exist, but are barely used. Ensuring a reasonable proof of efficacy and more widespread use of the first few of these will not just improve late life health, but also change the public perception of the treatment of aging. Physician adoption of these therapies is the key to widespread use, and can be achieved by running multiple, rapid, low-cost clinical trials for the first rejuvenation therapies, followed by marketing favorable results to physicians and physician organizations. Widespread physician-led adoption of the first rejuvenation therapies will produce far greater public and institutional support for progress towards a comprehensive set of rejuvenation therapies, technologies that, together, are capable of producing a dramatic reduction in late life suffering and mortality.

References

[1]: Intro to SENS Research. (2022, December 23) SENS Research Foundation. https://www.sens.org/our-research/intro-to-sens-research/

[2]: López-Otín, C., Blasco, M. A., Partridge, L., Serrano, M., & Kroemer, G. (2013). The Hallmarks of Aging. In Cell (Vol. 153, Issue 6, pp. 1194-1217). Elsevier BV. https://doi.org/10.1016/j.cell.2013.05.039

[3]: Hickson, L. J., Langhi Prata, L. G. P., Bobart, S. A., Evans, T. K., Giorgadze, N., Hashmi, S. K., Herrmann, S. M., Jensen, M. D., Jia, Q., Jordan, K. L., Kellogg, T. A., Khosla, S., Koerber, D. M., Lagnado, A. B., Lawson, D. K., LeBrasseur, N. K., Lerman, L. O., McDonald, K. M., McKenzie, T. J., … Kirkland, J. L. (2019). Senolytics decrease senescent cells in humans: Preliminary report from a clinical trial of Dasatinib plus Quercetin in individuals with diabetic kidney disease. In EBioMedicine (Vol. 47, pp. 446-456). Elsevier BV. https://doi.org/10.1016/j.ebiom.2019.08.069

[4]: Di Micco, R., Krizhanovsky, V., Baker, D., & d'Adda di Fagagna, F. (2020). Cellular senescence in ageing: from mechanisms to therapeutic opportunities. In Nature Reviews Molecular Cell Biology (Vol. 22, Issue 2, pp. 75-95). Springer Science and Business Media LLC. https://doi.org/10.1038/s41580-020-00314-w

[5]: Smith, P., Willemsen, D., Popkes, M., Metge, F., Gandiwa, E., Reichard, M., & Valenzano, D. R. (2017). Regulation of life span by the gut microbiota in the short-lived African turquoise killifish. In eLife (Vol. 6). eLife Sciences Publications, Ltd. https://doi.org/10.7554/elife.27014

[6]: Parker, A., Romano, S., Ansorge, R., Aboelnour, A., Le Gall, G., Savva, G. M., Pontifex, M. G., Telatin, A., Baker, D., Jones, E., Vauzour, D., Rudder, S., Blackshaw, L. A., Jeffery, G., & Carding, S. R. (2022). Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain. In Microbiome (Vol. 10, Issue 1). Springer Science and Business Media LLC. https://doi.org/10.1186/s40168-022-01243-w

[7]: Office of the Commissioner. (2022, November 30). FDA Approves First Fecal Microbiota Product. U.S. Food And Drug Administration. https://www.fda.gov/news-events/press-announcements/fda-approves-first-fecal-microbiota-product

[8]: AgingBiotech.info. (2023, January 05). https://agingbiotech.info/companies/

[9]: DiMasi, J. A., Grabowski, H. G., & Hansen, R. W. (2016). Innovation in the pharmaceutical industry: New estimates of R&D costs. In Journal of Health Economics (Vol. 47, pp. 20-33). Elsevier BV. https://doi.org/10.1016/j.jhealeco.2016.01.012

[10]: Hickson, L. J., Langhi Prata, L. G. P., Bobart, S. A., Evans, T. K., Giorgadze, N., Hashmi, S. K., Herrmann, S. M., Jensen, M. D., Jia, Q., Jordan, K. L., Kellogg, T. A., Khosla, S., Koerber, D. M., Lagnado, A. B., Lawson, D. K., LeBrasseur, N. K., Lerman, L. O., McDonald, K. M., McKenzie, T. J., … Kirkland, J. L. (2019). Senolytics decrease senescent cells in humans: Preliminary report from a clinical trial of Dasatinib plus Quercetin in individuals with diabetic kidney disease. In EBioMedicine (Vol. 47, pp. 446-456). Elsevier BV. https://doi.org/10.1016/j.ebiom.2019.08.069

[11]: Justice, J. N., Nambiar, A. M., Tchkonia, T., LeBrasseur, N. K., Pascual, R., Hashmi, S. K., Prata, L., Masternak, M. M., Kritchevsky, S. B., Musi, N., & Kirkland, J. L. (2019). Senolytics in idiopathic pulmonary fibrosis: Results from a first-in-human, open-label, pilot study. In EBioMedicine (Vol. 40, pp. 554-563). Elsevier BV. https://doi.org/10.1016/j.ebiom.2018.12.052

[12]: Gonzales, M. M., Garbarino, V. R., Marques Zilli, E., Petersen, R. C., Kirkland, J. L., Tchkonia, T., Musi, N., Seshadri, S., Craft, S., & Orr, M. E. (2021). Senolytic Therapy to Modulate the Progression of Alzheimer's Disease (SToMP-AD): A Pilot Clinical Trial. In The Journal of Prevention of Alzheimer's Disease (pp. 1-8). SERDI. https://doi.org/10.14283/jpad.2021.62

[13]: Participatory Evaluation (of) Aging (With) Rapamycin (for) Longevity Study (PEARL) (2022, October 04) https://clinicaltrials.gov/ct2/show/NCT04488601 ClinicalTrials.gov

[14]: Hill, S. (2021, September 1). PEARL Is Funded, Rapamycin Longevity Clinical Trials Begin. https://www.lifespan.io/news/pearl-is-funded-rapamycin-longevity-clinical-trials-begin/

[15]: AgelessRx. (2022, June 30). PEARL Trial to Prolong Life With Longevity Products. https://agelessrx.com/pearl/

[16]: forever-healthy. (2022, December 23). Forever Healthy - today, tomorrow and far beyond . . . Forever Healthy. https://forever-healthy.org/

[17]: LongevityTech.fund - Home. (2023, January 05). https://www.longevitytech.fund/

Random mutations in stem cells lead to a pattern of mutations throughout the tissue supported by those stem cells, as daughter cells are imprinted with a particular combination of mutations based on the ancestor stem cell and the timing of cell division versus timing of mutations. In principle, one can take a sample of somatic cells and reverse engineer the progression of mutations in the underlying stem cell and progenitor cell populations from the variety and combination of mutations observed in the sample. That progression can then be used as the basis for a measure of chronological or biological age, a novel form of aging clock to join the many others derived from age-related changes in biological data.

Biological age is typically estimated using biomarkers whose states have been observed to correlate with chronological age. A persistent limitation of such aging clocks is that it is difficult to establish how the biomarker states are related to the mechanisms of aging. Somatic mutations could potentially form the basis for a more fundamental aging clock since the mutations are both markers and drivers of aging and have a natural timescale. Cell lineage trees inferred from these mutations reflect the somatic evolutionary process and thus, it has been conjectured, the aging status of the body. Such a timer has been impractical thus far, however, because detection of somatic variants in single cells presents a significant technological challenge.

Here we show that somatic mutations detected using single-cell RNA sequencing (scRNAseq) from hundreds of cells can be used to construct a cell lineage tree whose shape correlates with chronological age. De novo single-nucleotide variants (SNVs) are detected in human peripheral blood mononuclear cells using a modified protocol. Penalized multiple regression is used to select from over 30 possible metrics characterizing the shape of the phylogenetic tree resulting in a Pearson correlation of 0.8 between predicted and chronological age and a median absolute error less than 6 years.

The geometry of the cell lineage tree records the structure of somatic evolution in the individual and represents a new modality of aging timer. In addition to providing a single number for biological age, it unveils a temporal history of the aging process, revealing how clonal structure evolves over life span. This complements existing aging clocks and may help reduce the current uncertainty in the assessment of geroprotective trials.

Link: https://doi.org/10.1101/2022.12.14.520419

Researchers here report on an interesting approach to treating scar tissue in skin. Noting that hair follicles appear to promote regeneration in healthy skin, they implant follicles into scar tissue. The result is some degree of beneficial remodeling of the scar. While the next logical step is to better understand the signaling involved in this effect, it is worth noting that researchers have been attempting to understand the mechanisms of skin regeneration for some time now. It is a very complex situation involving many different cell types, structures, and phases of activity that change over time. There is unlikely to be a simple solution that recapitulates the influence of follicle tissue on skin structure and maintenance.

Compared to scar tissue, healthy skin undergoes constant remodelling by the hair follicle. Hairy skin heals faster and scars less than non-hairy skin - and hair transplants had previously been shown to aid wound healing. Inspired by this, the researchers hypothesised that transplanting growing hair follicles into scar tissue might induce scars to remodel themselves. In a new study involving three volunteers, skin scars began to behave more like uninjured skin after they were treated with hair follicle transplants. The scarred skin harboured new cells and blood vessels, remodelled collagen to restore healthy patterns, and even expressed genes found in healthy unscarred skin.  

After transplantation, the follicles continued to produce hair and induced restoration across skin layers. Scarring causes the outermost layer of skin - the epidermis - to thin out, leaving it vulnerable to tears. At six months post-transplant, the epidermis had doubled in thickness alongside increased cell growth, bringing it to around the same thickness as uninjured skin. Scar maturation leaves the dermis with fewer cells and blood vessels, but after transplantation the number of cells had doubled at six months, and the number of vessels had reached nearly healthy-skin levels by four months. Scarring also increases the density of collagen fibres which causes them to align such that scar tissue is stiffer than healthy tissue. The hair transplants reduced the density of the fibres, which allowed them to form a healthier, 'basket weave' pattern, which reduced stiffness.

The researchers are unsure precisely how the transplants facilitated such a change. In their study, the presence of a hair follicle in the scar was cosmetically acceptable as the scars were on the scalp. They are now working to uncover the underlying mechanisms so they can develop therapies that remodel scar tissue towards healthy skin, without requiring transplantation of a hair follicle and growth of a hair fibre. They can then test their findings on non-hairy skin, or on organs like the heart, which can suffer scarring after heart attacks, and the liver, which can suffer scarring through fatty liver disease and cirrhosis. 

Link: https://www.eurekalert.org/news-releases/975634

The age-related decline and dysfunction of the vasculature kills a sizable fraction of humanity, directly through stroke and heart attack, and more indirectly through a number of other mechanisms. The rise of chronic inflammation with age can be blamed for much of this. Unresolved inflammatory signaling is highly disruptive to tissue function throughout the body. In the vasculature, it accelerates the altered macrophage behavior that lies at the root of atherosclerosis. It provokes some of the altered smooth muscle behavior that leads to hypertension as contraction and dilation of blood vessels become poorly controlled. It changes the behavior of cells in ways that lead to calcification of blood vessel walls.

The inner endothelium of blood vessels undergoes a range of detrimental functional changes with aging, and again many of these are driven at least in part by chronic inflammation. Disruption of this layer of the blood vessel wall appears to accelerate atherosclerosis, contribute to issues with the regulation of dilation and contraction, and produce leakage of the blood-brain barrier where blood vessels pass through the brain.

Endothelial Dysfunction and Chronic Inflammation: The Cornerstones of Vascular Alterations in Age-Related Diseases

Vascular diseases of the elderly are a topic of enormous interest in clinical practice, as they have great epidemiological significance and lead to ever-increasing healthcare expenditures. The mechanisms underlying these pathologies have been increasingly characterized over the years. It has emerged that endothelial dysfunction and chronic inflammation play a detrimental role among the most relevant pathophysiological mechanisms. As one can easily imagine, various processes occur during aging, and several pathways undergo irreversible alterations that can promote the decline and aberrations that trigger the diseases above.

Endothelial dysfunction and aging of circulating and resident cells are the main characteristics of the aged organism; they represent the framework within which an enormous array of molecular abnormalities occur and contribute to accelerating and perpetuating the decline of organs and tissues. Recognizing and detailing each of these dysfunctional pathways is helpful for therapeutic purposes, as it allows one to hypothesize the possibility of tailoring interventions to the damaged mechanism and hypothetically limiting the cascade of events that drive the onset of these diseases. With this paper, we have reviewed the scientific literature, analysing the pathophysiological basis of the vascular diseases of the elderly and pausing to reflect on attempts to interrupt the vicious cycle that connotes the diseases of aging, laying the groundwork for therapeutic reasoning and expanding the field of scientific research by moving from a solid foundation.

The prominence of inflammatory mediators, and the centrality of the inflammasome, have led scholars to set up studies to evaluate the possibility of inhibiting certain checkpoints from fighting the diseases of aging, so much so that there are ongoing trials to evaluate the efficacy of molecules that can inhibit the inflammasome from reducing cardiovascular risk. Blocking the inflammasome and reducing the blood concentrations of its products, first and foremost IL-1 beta and IL-18, could be an exciting target of future therapies, perhaps using monoclonal antibodies to tailor actions to specific targets. Compared with the past, today there are suggestive and fascinating pathways that hint at the possibility of counteracting the passage of time and the onset of age-related diseases. More pragmatically, the development of drugs of this type may enable successful aging.

As this paper notes, there is a great deal of data regarding genetics and aging, but as yet little in the way of useful conclusions when it comes to applying this knowledge to extend the healthy human life span. From a reductionist point of view, it is clear that genetic differences lie at the root of the large differences in trajectory of aging and life span that are observed between species. The evidence to date suggests that genetic variance within a species has little impact on life span, however. The observe range of life expectancy within a species is mostly a matter of environment and lifestyle. A great deal of funding and effort goes into the continued investigation of the genetics of human longevity, but it isn't at all clear that this will lead to ways to meaningfully extend healthy life span.

The search for key genes of aging and longevity and the study of intracellular signaling pathways can become the basis for the development of methods for diagnosis and correction of conditions that accompany the aging process and for the development of therapeutic methods that increase the duration and quality of life. Numerous studies using model organisms, study of the main mechanisms of cellular aging, large-scale genome-wide association studies in humans, and genetic studies of long livers made it possible to identify various evolutionary conservative metabolic pathways that are similar in various species of organisms and humans, as well as individual genetic loci that affect key traits of human aging and life expectancy.

A significant increase in the life expectancy and the inevitable demographic aging of mankind are pushing researchers to focus more and more on the search for genetic determinants of healthy aging and longevity. In this regard, there is a need to create publicly available high-quality resources with open and integrated databases. Currently, there are already several large resources containing databases of candidate genes and genetic variants associated with human longevity and aging.

Despite the success in identifying genes and metabolic pathways that may be involved in the life extension process in model organisms, the key question remains to what extent these data can be extrapolated to humans, for example, because of the complexity of its biological and sociocultural systems, as well as possible species differences in life expectancy and causes of mortality. New molecular genetic methods have significantly expanded the possibilities for searching for genetic factors of human life expectancy and identifying metabolic pathways of aging, the interaction of genes and transcription factors, the regulation of gene expression at the level of transcription, and epigenetic modifications. This review presents the latest research and current strategies for studying the genetic basis of human aging and longevity: the study of individual candidate genes in genetic population studies, variations identified by the GWAS method, immunogenetic differences in aging, and genomic studies to identify factors of "healthy aging."

Link: https://doi.org/10.1134/S1022795422120067

Researchers here report on an interesting approach to encouraging the immune system to attack cancer cells in an established tumor. They engineer cancer cells to be more visible to the immune system and then return them to the body, where they will naturally home to the site of the tumor. At present the proof of concept is established in animal models; time will tell as to whether this line of work attracts the support needed to progress further towards the clinic.

Cancer vaccines are an active area of research for many labs, but the new approach to treating the brain cancer glioblastoma that researchers have taken is distinct. Instead of using inactivated tumor cells, the team repurposes living tumor cells, which possess an unusual feature. Like homing pigeons returning to roost, living tumor cells will travel long distances across the brain to return to the site of their fellow tumor cells. Taking advantage of this unique property, the team engineered living tumor cells using the gene editing tool CRISPR-Cas9 and repurposed them to release a tumor cell killing agent.

In addition, the engineered tumor cells were designed to express factors that would make it easy for the immune system to spot, tag, and remember them, priming the immune system for a long-term antitumor response.  The team tested their repurposed CRISPR-enhanced and reverse-engineered therapeutic tumor cells in different mice strains, including one that contained bone marrow, liver, and thymus cells derived from humans, mimicking the human immune microenvironment. The team also built a two-layered safety switch into the cancer cell, which, when activated, eradicates therapeutic tumor cells if needed. This dual-action cell therapy was safe, applicable, and efficacious in these models, suggesting a roadmap toward therapy.

Link: https://hms.harvard.edu/news/vaccine-simultaneously-kill-prevent-brain-cancer

Change and disruption in the immune system is an important component of degenerative aging. Broadly, the immune system becomes ever more inflammatory (inflammaging) while also becoming ever less effective (immunosenescence). The immune system is not only responsible for defending against invasive pathogens and destroying errant cells, but it is also tightly integrated into the normal processes of tissue maintenance and operation. When immune cells become inflammatory, they abandon the range of tasks needed to keep tissues functional. Short-term inflammation is necessary in response to injury and infection, but unresolved, chronic inflammation is a major issue, highly disruptive, and contributing to the onset and progression of many age-related conditions.

That immune aging is a major issue is widely recognized, and many research and development initiatives are aimed at restoration of at least some aspect of lost immune function: largely reduction of inflammation, but also restoration of immune capacity in defense against pathogens or clearance of cancerous and senescent cells. The most promising direct approaches involve (a) improvement of hematopoietic stem cell function, (b) restoration of the thymus to enable greater production of T cells, (c) clearance of misconfigured and damaged immune cell populations. Removing the stimuli for chronic inflammation should also prove helpful, such as via clearance of senescent cells.

Immune system modulation in aging: Molecular mechanisms and therapeutic targets

Inflammation is a key factor for the onset and progression of almost all chronic diseases affecting aged individuals, with immunosenescence and inflammaging being two relevant phenomena that modulate the immune system during aging. Therefore, identification and characterization of the molecular and cellular mechanisms underlying the immune system dysfunction will surely help to develop effective therapeutic strategies to prevent the negative outcomes of infectious diseases on aged individuals.

For that reason, several pharmacological and cellular/genetic strategies have been developed to slow down or reverse the deleterious effects of immunosenescence on health: (a) Induced pluripotent stem cells (iPSCs) have been employed to generate hematopoietic cells and/or various specific immune cells; (b) administration of cytokine and growth factor cocktails boosted macrophage function; (c) bone marrow transplantation is a widely used therapy for thymus regeneration; (d) the use of Cdc42 and BATF inhibitors or antioxidants enhances the number and function of lymphoid-biased hematopoietic stem cells; (e) inhibition of dual specific phosphatases 4 boosts memory CD4+ T-cell function; (f) administration of fibroblast growth factor 7 (FGF7) stimulates naive T-cell production and promotes the removal of dysfunctional cells, thereby restoring thymus function; and (g) administration of rapamycin improves CD8+ T-cell function.

Finally, a relevant non-pharmacological strategy that has been proven to enhance immunity is caloric restriction; it delays the accumulation of senescent T cells and stimulates thymopoiesis through the activation of IGF-1 and/or PPAR pathways. On the other hand, recent studies have unveiled the relevance of functional foods to ameliorate oxidative stress and inflammation and to improve the metabolism of lipids associated with metabolic diseases, via Nrf2 and/or NF-κB signaling pathways.

Some of the molecules/pathways that modulate immunosenescence have therapeutic potential. Owing to the crucial role of the activator protein 1 (AP-1) signaling pathway in macrophage-mediated inflammation, targeting of AP-1 has been approached to attenuate inflammation. Transfection of lentiviral siRNA against AP-1 in mice fed with high-fat diet resulted in the alleviation of systemic and hepatic inflammation. Interestingly, the use of rosiglitazone, a PPARγ agonist, was found to exert a positive effect on animals with sepsis, decreasing cell death and cardiac inflammation; furthermore, increased fatty acid oxidation and improved insulin resistance were also observed in human skeletal muscle. Since aging is a very complex process that involves different biological processes, therapies aimed to modulate inflammaging have to be focused on the synergic effect of more than one compound, to regulate simultaneously different pathways. For instance, a combinatory treatment using three different compounds, rapamycin, acarbose, and 17α-estradiol, converge on the regulation of both ERK1/2 and p38-MAPK pathways.

The diverse processes of neurodegeneration are all running at the same time in an aging brain, with some individuals exhibiting more of one or less of another. It is challenging to pick apart distinct mechanisms in aging tissue to decide whether not they contribute to one another, or share specific underlying causes. The question of the direction of causation for specific mechanisms in aging is similarly challenging. Here, researchers discuss possible links and overlapping mechanisms for the aggregation of altered forms of TDP-43 and tau, both characteristic of the aging brain.

Autopsy-based research has revealed that comorbid pathology often has a disease-specific manner, in terms of the biochemical properties, morphological characteristics, and spatial distributions of aggregates, and has an impact for clinical phenotypes. Genetic studies have identified overlapping genetic risk factors between limbic-predominant age-related TDP-43 encephalopathy (LATE) and Alzheimer's disease (AD) or between TDP-associated ALS and frontotemporal dementia or tauopathies. These facts indicate that comorbid pathology is not an incidental bystander, but a part of the disease pathogenesis. It will be important to determine when a TDP-43 or tau pathology is comorbid during disease pathogenesis; antemortem studies using functional neuroimaging targeting aggregated proteins will be useful in the future.

Basic research findings have suggested that the molecular pathways are partially overlapped between TDP-43 proteinopathies and tauopathies. In vivo studies have revealed that aggregated TDP-43 altered the splicing of tau or exacerbated tau aggregation. Moreover, perturbation of the autophagosome-lysosome system-related molecules has been reported in both TDP-43 proteinopathy and tauopathy models. However, it currently seems to be difficult to reproduce the condition of double proteinopathy comprising TDP-43 and tau pathologies by altering just one of the known related molecules or genes. This fact suggests that pathogeneses of TDP-43 proteinopathies and tauopathies arise from multifactorial and polygenetic processes. Further investigations to clarify the pathogenetic factors that are shared by a broad spectrum of neurodegenerative disorders will establish key therapeutic targets.

Link: https://doi.org/10.3390/ijms232415755

Age-related hearing loss and cognitive impairment may arise from the same underlying processes of neurodegeneration, but equally there is evidence for each of these forms of impairment to contribute to the other. Today's paper is an example of this sort of analysis, in which the researchers employed data on hearing aid use in older patients as a way to investigate this relationship. They find that hearing loss appears to contribute to cognitive impairment.

Modifiable risk factors for dementia include untreated mid-life hearing loss, and it has been estimated that 8% of dementia cases globally are attributable to this factor. Proposed mechanisms underlying the relationship between hearing loss and the development of dementia include (i) common underlying pathology (probably vascular), (ii) impoverished input affecting brain structure and function, (iii) cognitive resources overoccupied in listening unavailable for higher functions and (iv) interaction between auditory function and dementia pathology. These mechanisms are not mutually exclusive.

Health records data from 380,794 Veterans who obtained hearing aids from the US Veterans Affairs healthcare system were analysed. Consistent with previous findings, we found that patients over 60 years of age without cognitive impairment at the time of hearing-aid fitting, who remained persistent hearing-aid users, had 27% reduced odds of receiving a dementia diagnosis 3.5-5 years after hearing-aid fitting than patients who did not persist in hearing-aid use. Our odds ratio (OR) of 0.73 is broadly in line with the hazard ratio of 0.82 found in a large sample of adults over 66 years of age with diagnosed hearing loss. The adjusted OR for incident dementia was 0.73 for persistent (versus non-persistent) hearing-aid users. The adjusted OR for hearing-aid use persistence was 0.46 in those with pre-existing dementia (versus those remaining free of mild cognitive impairment and dementia).

This suggests that of the four possible mechanisms linking hearing loss and dementia, the first (common pathology) is not dominant, since hearing-aid treatment cannot affect that pathology. Further probing of candidate mechanisms would at the very least require data on duration of hearing loss, which was not available in our dataset. This study provides (to the authors' knowledge) the first quantitative evidence that the diagnosis of dementia is associated with subsequent lower persistence of hearing-aid use. This may be due to reduced abilities to perform instrumental activities, or diverse other mechanisms, including memory problems, reduced motivation to engage in social interaction, and carers prioritising other aspects of care.

Link: https://doi.org/10.1093/ageing/afac266

In recent years, researchers have shown that a single injected dose of CASIN, an inhibitor of CDC42, can improve immune function in old mice, resulting in a lasting gain in health and extended life span. CASIN appears to work by altering epigenetic state in the hematopoietic stem cell populations responsible for producing new immune cells. This is also observed to be the case in other stem cell populations. Raised levels of CDC42 are observed with aging, and have been shown to impair hematopoietic stem cells. This is the case in both mice and humans, so there is some hope that some form of CDC42 inhibition can be used as the basis for a human therapy.

Mogling Bio was recently founded to develop therapies based on the results obtained with CASIN. As I understand it, while CASIN appears safe in animal studies, it isn't as bioavailable as might be desired. The animal doses are large enough that human equivalent doses would require an intravenous infusion rather than a simple injection. The Mogling Bio founders are likely to work on alternative approaches, or tinker with the structure - the usual approach for a new biotech company starting from the position of an interesting compound. That compound is the foundation for improvements that can be patented, providing the monopoly required to support the high company valuation that is needed to raise the sizable funding required to enter the regulatory process. It isn't the best of systems, given the incentives it places on development.

Still! Therapies for which a single dose produces a lasting effect, and where that effect is visible rejuvenation of function in old animals, are much more intriguing than those that require constant dosing over time. I would imagine that we'll see some interest in the self-experimenter community regarding CASIN as matters move ahead with development based on this compound, though (a) the logistics of use, given the large doses and need for injection, make it a more challenging project than is the case for most compounds, and (b) there is no human safety data, perhaps the more important point here. There are other CDC42 inhibitors with at least some human data, predictable emerging from the cancer research community, but these are not specific inhibitors of CDC42, and it is something of a question as to whether they would have similarly useful effects as CASIN.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice

The ability to restore or rejuvenate aged tissues by targeting endogenous stem cells is a central goal of regenerative medicine. However, systemic rejuvenation of aged stem cells remains a challenge and it is still unclear to what degree do stem cells contribute to overall organism health- and lifespan. Here, we show that a brief systemic treatment of aged mice with the Cdc42-activity inhibitor CASIN improves the regenerative potential of endogenous aged muscle stem cells (MuSCs) and hematopoietic stem cells (HSCs) in vivo.

We report that after CASIN treatment aged MuSCs divisional kinetic and myogenic capacity in vitro are enhanced and, after injuring the muscle in vivo, tissue regeneration is improved. Supporting that the MuSC improvement after CASIN might contribute to extend mouse healthspan, CASIN mice performed better than aged control mice in endurance and strength tests in steady-state and also after damage. Moreover, we report on systemic CASIN affecting Cdc42 and tubulin polarity as well as H4K16ac epigenetic polarity in aged HSCs. The data on H4K16ac obtained by histological analyses of whole mount bone marrow sections aligns to those previously reported on the DNA-methylation-based epigenetic clock and strongly support at least some traits of epigenetic rejuvenation in HSCs after systemic CASIN treatment.

Furthermore, the histological analysis shows an intriguing effect of CASIN also on aged HSC localization, which after the treatment is closer to arteries and endosteum, like young blood stem cells. At the transcriptional level, stress response, and inflammation constitute the major signaling pathways targeted by CASIN in vivo. Consistently, we have previously reported a significant reduction in the levels of inflammatory cytokines (IL1α, IL1β, and INFγ) in peripheral blood serum of aged mice after in vivo CASIN treatment. These same cytokines were also shown by others to play critical roles in aging of the blood and other tissues

The hematopoietic system is the carrier for many rejuvenation factors, and this leaves open the possibility that rejuvenating aged HSCs might represent an effective strategy to improve aging of the whole organism. Here we show that upon transplantation rejuvenated blood stem cells are sufficient to increase murine lifespan of aged immunocompromised mice. Altogether these results raise critical considerations for refining the targets and goals of anti-aging strategies focusing on a possible central role of HSCs and of the hematopoietic system. To note, previous data associated increased Cdc42 activity to aging in humans and in aged human HSCs, supporting the translational potential of these findings.

These data, together with the recent data supporting an improved activity of aged intestinal and hair follicle stem cells after CASIN treatment support that the increased activity of Cdc42 with aging impairs the function of several somatic stem cells in different tissues. Therefore, systemic treatment with CASIN can elicit distinct positive biological effects in vivo, which might depend on the doses and way of administration. Besides, recently Cdc42 activity has been shown to limit the lifespan of the budding yeast, hinting at a phylogenetically conserved mechanism of the Cdc42-polarity axis in affecting organism aging.

Researchers are increasingly considering chronic, unresolved inflammation in brain tissue to be an important pathological mechanism in Alzheimer's disease. Removing senescent cells from the brain has reduced pathology in mouse models of Alzheimer's disease. While, as ever, the issue with all such models is their artificiality, as mice do not naturally suffer anything resembling Alzheimer's disease, it is well established that inflammation is a feature of Alzheimer's disease in humans. We have a good idea as to the major causes of this inflammation: senescent cells, an altered gut microbiome, debris from stressed cells that provokes an innate immune reaction, and so forth. Targeting the causes of excessive inflammation without suppressing the whole immune response may well prove to be a useful preventative treatment for many age-related conditions.

Alzheimer's disease (AD) should be viewed as a systemic disease that involves dynamic processes in the peripheral and central immune compartments. The conceptualization of the pathogenesis of AD remains elusive, with many competing hypotheses, particularly those based on proteopathic and immunopathic mechanisms. The peripheral and central immune systems are dysregulated in AD and are related to the cognitive function and clinical status. They may change in a non-linear manner over time, and burgeoning evidence also suggests that the roles of the innate and adaptive immune processes differ depending on the pathological stage of AD.

Animal studies have provided insights into the possible mechanisms of peripheral and central immune communication, including direct pathways that involve peripheral immune cell infiltration of the central nervous system (CNS), as well as indirect pathways that involve the systemic-inflammation-driven modulation of the microglial function. The possibility of the involvement of other processes, such as the immune system, in AD remains underexplored, even though many immune mechanisms, such as phagocytosis, aid in the reduction in AD pathologies and, on the contrary, the dysfunction of the immune system has largely been painted as detrimental to the AD pathology. Recently, there has been increasing interest in the role of the immune system in neurodegeneration due to the accumulating evidence stressing the role of the immune system as an essential factor or a major driver of neuroinflammation processes, Alzheimer's pathogenesis and AD progression. In fact, immunosenescence is a dysregulation of the immune system that accompanies aging.

Immunotherapies and neuroimmune manipulations, which can treat a wide array of diseases, can effectively treat the disease and the changes it makes to our body's watchdog, the immune system. Moreover, the suppression of inflammatory cytokines has been seen to be beneficial in immunomodulation. In order to fight neuroinflammation under chronic neurodegenerative conditions, systemic immunity should be boosted rather than suppressed. Thus, we stress the idea that, in efforts to fight AD, it might be possible to target the immune system rather than directly target specific disease-escalating factors within the brain. The rebalancing of the immune response and its exploitation to wipe toxic plaques from the brain may bring new hope for a safe and effective treatment for this devastating illness.

Link: https://doi.org/10.3390/jpm12111817

Is outright replacement of tissues a viable option for the treatment of aging? There are factions within the longevity-interested community who think that the paths to either (a) engineering replacement brain tissue for parts of the brain not involved in memory, or (b) transplantation of an old head onto a young body or brain into a young body, are short enough to be worth pursuing, where "short enough" means a few decades of work given sufficient funding. To my mind, major surgery of the sort implied by replacement of large sections of tissue or entire organs is something to be avoided in later life, given the risks and cost. It is better to pursue a strategy of introducing new stem cells or repairing existing cell populations, a more gentle approach that would avoid the need for surgery, and at this point doesn't seem to require a much longer timeline for development.

Brain or cerebral organoids are very specific neuronal cell cultures that were developed from human-induced pluripotent stem cell cultures, but with a slightly modified protocol. Grown spheroids of pluripotent stem cell cultures can be integrated within special solubilized membrane matrices which can support growing cells in a 3D environment, hence, producing organoids. Several scientific publications have already successfully shown that such cerebral organoid cultures present diverse populations of neurons and display processes like cortical development and cell migration. They also excrete their own extracellular matrix with many physiologically relevant components like hyaluronic acid, proteoglycans, and various functional enzymes.

Human embryonic stem cell-derived brain organoids have been implemented with needles into the damaged brain parts of cortical impact-modeled severe combined immunodeficient mice. Grafted organoids not only survived, but also differentiated, showed electroactivity, and extended long signal projections. Moreover, they promoted brain tissue repair and vascularization, learning and memory ability, and reduced glial scarring. The study also raised more questions, like how far the transplanted grafts can go in terms of repairing traumatic brain damage and scarring, as well as how to improve the survival of these neural stem cells in the brain in the future.

Since 2012, there have been some efforts regarding brain transplantation in mice models. A Chinese orthopedic surgeon, famous for being a part of the team that successfully performed the first hand transplant, tried to graft a mouse's head onto another mouse, and the grafted heads survived for about half a year. Somewhere around the same time, an Italian brain surgeon published the protocol that claimed it would make human head transplantation possible. A later review discussed various protective strategies in head transplantation, as well as several protocols to keep the vascular systems connected and brains under hypothermia.

In 2017, further work took place on a cross-circulated bicephalic model of head transplantation to study the long-term effects of transplant rejection and blood flow restrictions during the head transference phase. By using vascular grafts, they connected the thoracic aorta and the superior vena cava from one rat to the carotid artery and extracorporeal veins of another rat. A third rat was used as a blood reservoir and its carotid artery and extracranial vein were connected to the donor rat with silicone tubes before the thoracotomy was performed on the donor rat. A pump and a heating device were connected to the silicone tubes to ensure regular blood supply and to prevent brain hypothermia. After performing the transplant surgery, the donor rat had pain and corneal reflexes, and the surgery opened up the possibility for the long-term survival of the patient.

Such scientific procedures have always drawn a lot of media frenzy and raised many ethical dilemmas. The first feeling people get when they hear "head transplant" or "brain transplant" is simply an ick. Funnily enough, they don't seem to respond in the same way when they hear about liver or kidney transplants. So far, head transplant surgeries have not been successful on live animal models, let alone on humans. While the ethical implications of such a procedure are immense, the technological limitations are such that it is too early to think about ethics. The largest technical limitation, like with any transplant, is still the immune response against the new "foreign" body. Even with increasing numbers and more frequent organ transplantations, particularly liver transplants, rejection still occurs very often, sometimes even a year after the surgery.

Link: https://www.forbes.com/sites/alexzhavoronkov/2022/11/22/can-you-transplant-a-brain-into-a-young-new-body-and-would-you/

The state of the gut microbiome is arguably as influential on health as exercise. Various microbial species present in the gut produce beneficial metabolites, such as butyrate, or harmful metabolites, such as isoamylamine, or can provoke chronic inflammation in a variety of ways. An individual can have a better or worse microbiome, assessing these and other functional contributions to health. With age, the balance of populations shifts towards fewer benefits and greater harm, unfortunately.

Since the composition of the microbiome can be assessed accurately and cheaply via 16S rRNA sequencing, understanding of the gut microbiome is advancing rapidly. There is no one optimal gut microbiome, but some species are more helpful than others. Looking at human populations, researchers are beginning to see patterns emerge from the study of the gut microbiome in healthier and more long-lived people. Today's open access paper is an example of this sort of work, in which the microbiomes of centenarians are assessed and compared with the broader population.

This is all interesting, but a short-cut to improving the aged gut microbiome does exist, in advance on understanding all of the desired component species, proportions, and effects on health. That is to conduct a fecal microbiota transplant from a young donor into an older recipient, using screened stool samples from a service such as Human Microbes. In animal studies, lasting rejuvenation of the gut microbiome, along with improved health and extended life span, can be achieved in this way. Robust human data has yet to be obtained, despite the use of fecal microbiota transplantation as a treatment for severe dysbiosis, but that is just a matter of time.

Gut microbiota as an antioxidant system in centenarians associated with high antioxidant activities of gut-resident Lactobacillus

Clinical studies have also shown that the diversity and composition of the gut microbiota is non-linear with age. In centenarians, the abundances of Roseburia and Escherichia were significantly higher than in non-centenarians, while Lactobacillus, Faecalibacterium, Parabacteroides, Butyricimonas, Coprococcus, Megamonas, Mitsuokella, Sutterella, and Akkermansia were significantly lower in centenarians than in non-centenarians. The age-related trajectories of the human gut microbiome are characterized by a loss of genes for short-chain fatty acid production and an overall decrease in glycolytic potential, while proteolytic functions are more abundant than in the gut metagenome of young adults.

A study using metagenomic sequencing to identify compositional and functional differences in the gut microbiota associated with age groups in Sardinia, Italy. The data showed that the gut microbiota of Sardinian centenarians was mainly characterized by depletion of Faecalibacterium prausnitzii and Eubacterium rectale, while enriched Methanobrevibacter smithii and Bifidobacterium adolescentis compared with young and old. Functional analysis showed that centenarians had higher metabolic capacity, especially glycolysis and fermentation of short-chain fatty acids (SCFAs), and lower genes encoding carbohydrate-degrading enzymes, including fiber and galactose.

Studies have shown that centenarians have a unique gut microbiome rich in microorganisms capable of producing unique secondary bile acids, including various isomers of lithocholic acid (LCA). These findings suggest that the metabolism of specific bile acids may be involved in reducing the risk of pathogenic infection and thus may contribute to the maintenance of intestinal homeostasis. Although we believe that longevity appears to be achieved by maintaining gut microbiota homeostasis, whether changes in gut microbiota are a consequence or a cause of aging, and the exact relationship between gut microbiota and aging remains to be further explored.

In this study, we combined metagenomic sequencing and large-scale in vitro culture to reveal the unique gut microbial structure of the world's longevity town - Jiaoling, China, centenarians, and people of different ages. Functional strains were isolated and screened in vitro, and the possible relationship between gut microbes and longevity was explored and validated in vivo, revealing associations of the gut microbiota with age and a number of clinical and metabolic parameters.

We uncovered age-specific gut microbiota characteristics, including a core set of seven microbial taxa enriched in centenarians and the gut microbiota of centenarians exhibited higher xenobiotics biodegradation and metabolism, oxidoreductase. We revealed age-related gut microbial characteristics in all populations, including increased alpha diversity and increased levels of abundances of the health-related bacteria such as Akkermansia, Lactobacillus, and short-chain fatty acid (SCFA) producers, and targeted screening an age-related gut-resident Lactobacillus with independent intellectual property rights, which metabolites and itself have good antioxidant effects.

Animal studies show that long term inadequate hydration shortens life span, causing changes in cell behavior similar to that of aging. Using sodium levels in blood samples as a proxy measure for hydration, researchers here show that high sodium (meaning poor hydration) correlates with increased risk of age-related disease in large study populations. The effect size is fairly large, in the same ballpark as sizable lifestyle differences. Given the low cost of adjusting water intake, perhaps something to bear in mind.

In this study, we report on serum sodium in the upper part of the normal range being a risk factor for accelerated aging. In the Atherosclerosis Risk in Communities (ARIC) study, odds to be biologically older than chronological age was increased in the study participants whose serum sodium exceeded 142 mmol/l, reaching 50% increased odds at sodium levels exceeding 144 mmol/l. Such elevated biological age at middle age (47-68 years) translates into an approximate 20% increased risk of premature mortality at sodium levels greater than 144 mmol/l and increased risk to develop chronic diseases, that was already evident at sodium concentrations greater than 140 mmol/l and increased to approximately 40% higher risk in 143-146 mmol/l group.

The results of our study support the hypothesis that optimal hydration can potentially be such systemic preventive approach that is able to prolong diseases-free lifespan. Our data are consistent with previous reports from epidemiological and interventional studies that link hypohydration biomarkers including higher serum sodium and copeptin as well as low fluid intake with adverse health effects and increased risk of mortality. In agreement with the ARIC data from four U.S. communities that were used in current study, similar sodium levels, greater than 144 mmol/l, were found to be associated with increased risk of all-cause and chronic disease associated mortality within 3-6 years for U.S. adults aged 51-70 years in 2009-2012 National Health and Nutrition Examination Survey (NHANES).

The main limitation of our study is its observational nature resulting in the possibility of residual confounding. This common limitation of the observational studies is reduced to some degree in our case, because the idea for this analysis originated from a well-controlled mouse study in which lifelong water restriction shortened life span and promoted degenerative changes in multiple organ systems. In addition to the direct effect of life-long water restriction on life span and degenerative changes in the mouse model, pro-aging effects of hypohydration is also supported by other results from previous basic research studies. In those studies, increased sodium in cell culture models as well as water restriction in mouse model triggered the same changes that have been identified as underlying factors for accelerated aging and are currently considered as targets for anti-aging interventions.

Link: https://doi.org/10.1016/j.ebiom.2022.104404

It is interesting to see the present state of popular science commentary on efforts to treat aging as a medical condition, given the recollection of widespread skepticism and mockery even as recently as a decade ago. The large-scale funding, many serious research programs, and dozens of new biotech companies are ensuring that the popular science press at least does its homework on the science underlying the prospects for human rejuvenation before committing an opinion to paper. Today's bootstrapping era of progress is very different from the turn of the century, a great deal more is being accomplished, but these are still only the first steps on a longer road, populated by many more travelers than presently the case.

Scientists now have a good handle on what causes us to age, biologically speaking: The so-called "hallmarks" of the aging process range from damage to our DNA - the instruction manual within each of our cells - to proteins that misbehave because of alterations to their chemical structure. Most excitingly, we now have ideas of how to treat them. By the end of 2023, it's likely that one of these ideas will be shown to work in humans. One strong contender is "senolytics," a class of treatments that targets aged cells - which biologists call senescent cells - that accumulate in our bodies as we age. These cells seem to drive the aging process - from causing cancers to neurodegeneration - and, conversely, removing them seems to slow it down, and perhaps even reverse it.

A 2018 paper showed that in experiments in which mice were given a senolytic cocktail of dasatinib (a cancer drug) and quercetin (a molecule found in colorful fruit and veg), not only did they live longer, but they were at lower risk of diseases including cancer, were less frail (they could run further and faster on the tiny mouse-sized treadmills used in the experiments), and even had thicker, glossier fur than their littermates not given the drugs.

There are more than two dozen companies looking for safe and effective ways to get rid of these senescent cells in people. The biggest is Unity Biotechnology, founded by the Mayo Clinic scientists behind that mouse experiment and with investors including Jeff Bezos, which is trialing a range of senolytic drugs against diseases like macular degeneration (a cause of blindness) and lung fibrosis. There are many approaches under investigation, including small proteins that target senescent cells, vaccines to encourage the immune system to clear them out, and even gene therapy by a company called Oisín Biotechnologies.

Link: https://www.wired.com/story/drugs-aging-medicine-biotech/

Today's popular science article is a tour of a few of the higher profile lines of research and development relevant to treating aging as a medical condition. The state of the field has changed greatly over the last decade, not least of these changes being a vast increase in the funding devoted to clinical translation of age-slowing and rejuvenation therapies. Cynically, I suspect that it is the funding that ensures that the popular science press takes a more respectful tone than they did ten years ago. It is much harder to advance (in writing!) a knee-jerk dismissal of a field of science when billions of dollars of funding and many large, conservative institutions are involved, as they are these days.

As you read the article, spare a thought for the many people - scientists, advocates, entrepreneurs, and philanthropists, some of whom are no longer with us - who spent years to decades laboring in comparative obscurity to build the foundations that led to the present stage of growth and interest in producing viable treatments for degenerative aging. The sudden sea change of public perception, funding, and breadth of research over the past decade, and indeed the advent of the entire longevity industry as it stands today, didn't just happen by accident. Success tends to erase the slow and painful process of bootstrapping that came before it, but that bootstrapping was still necessary and valuable.

Can ageing be cured? Scientists are giving it a try

Scientists are great at making mice live longer. Rapamycin, widely prescribed to prevent organ rejection after a transplant, increases the life expectancy of middle-age mice by as much as 60 percent. Drugs called senolytics help geriatric mice stay sprightly long after their peers have died. The diabetes drugs metformin and acarbose, extreme calorie restriction, and, by one biotech investor's count, about 90 other interventions keep mice skittering around lab cages well past their usual expiration date. The newest scheme is to hack the ageing process itself by reprogramming old cells to a younger state.

What about us? How far can scientists stretch our life span? And how far should they go? Between 1900 and 2020, human life expectancy more than doubled, to 73.4 years. But that remarkable gain has come at a cost: a staggering rise in chronic and degenerative illnesses. Ageing remains the biggest risk factor for cancer, heart disease, Alzheimer's, type 2 diabetes, arthritis, lung disease, and just about every other major illness. It's hard to imagine anyone wants to live much longer if it means more years of debility and dependence.

But if those mouse experiments lead to drugs that clean up the molecular and biochemical wreckage at the root of so many health problems in old age, or to therapies that slow-or, better yet, prevent-that messy buildup, then many more of us would reach our mid-80s or 90s without the aches and ailments that can make those years a mixed blessing. And more might reach what is believed to be the natural maximum human life span, 120 to 125 years. Few people get anywhere close. In industrialised nations, about one in 6,000 reaches the century mark and one in five million makes it past 110.

Human biology, it seems, can be optimised for greater longevity. Unimaginable riches await whoever cracks the code. No wonder investors are pouring billions into trying. This work is powered by artificial intelligence, big data, cellular reprogramming, and an increasingly exquisite understanding of the zillions of molecules that keep our bodies humming. Some researchers even talk about "curing" ageing.

Cellular senescence is a double-edged sword in the matter of cancer. A cancer cell turned senescent, and thus entered a state of growth arrest, is not a cancer cell that continues to replicate. It secretes pro-growth, pro-inflammatory signals that draw the attention of the immune system. This can be beneficial, helping to defeat a cancer, particularly in the early stages. After a certain point, however, too much cellular senescence aids the cancer in further growth. While it seems clear that senolytic treatments to remove lingering senescent cells are wholly beneficial after a cancer is defeated, it isn't clear that the same is true of senolytic treatment conducted before or during cancer therapy. As this paper notes, whether clearance of senescent cells during cancer therapy is beneficial or harmful may vary from patient to patient, even for the same type of cancer.

Clinical evidence of cellular senescence in cancer patients has long been underestimated, in part due to the difficult detection, since currently no specific and universal markers for senescent cells exist. Historically, cellular senescence was primarily considered as an endogenous tumor suppressor mechanism halting the proliferation of damaged cells which are at risk of malignant transformation, thereby protecting against cancer. However, during the last two decades, a more nuanced view on the involvement of cellular senescence in tumorigenesis and response to therapy has emerged.

Here, we provided a comprehensive overview on the prognostic implications of cellular senescence in cancer patients with solid tumors. Increasing clinical evidence add to the antagonistic pleiotropy of cellular senescence as differential prognostic outcomes, ranging from improved to impaired outcome, are demonstrated. In a simplified model we propose that the prognostic implications of oncogene-induced senescence (OIS) as well as therapy-induced senescence (TIS) are highly context-dependent and primarily depend on the senescence burden, the secretion and the composition of the senescence-associated secretory phenotype (SASP) and/or duration of SASP presence, thereby providing a rationale for the differential outcomes of OIS as well TIS observed within the same cancer type as well as between different types of cancer.

The detection of cellular senescence in cancer patients can be achieved by various methods and using various markers. Despite clear algorithms to accurately assess and quantify senescent cells in vitro and in vivo, a plethora of different senescence markers, single or combined with other markers, are currently used to demonstrate the presence of cellular senescence. Hence, it is difficult to compare clinical data and to draw reliable conclusions regarding the prognostic implications of cellular senescence, as well as the implementation of emerging senolytics (i.e., targeted removal of senescent cells) and senomorphics that modify/suppress the SASP, underlining the need for a uniform and consistent application of recognized and validated markers of cellular senescence.

Link: https://doi.org/10.1186/s13046-022-02555-3

Researchers here show that caveolin-2 expression increases with age in the endothelial cells lining blood vessels in the brain. Removing caveloin-2 reduces the age-related increase in neuroinflammation, suggesting that this protein is regulating some portion of the endothelial dysfunction characteristic of old age. Endothelial aging contributes to blood-brain barrier leakage, for example, and that might explain the link to inflammation in brain tissue, as inappropriate cells and molecules find their way into the vulnerable environment of the brain.

Aging is a major risk factor for common neurodegenerative diseases. Although multiple molecular, cellular, structural, and functional changes occur in the brain during aging, the involvement of caveolin-2 (Cav-2) in brain ageing remains unknown. We investigated Cav-2 expression in brains of aged mice and its effects on endothelial cells. Human umbilical vein endothelial cells (HUVECs) showed decreased THP-1 adhesion and infiltration when treated with Cav-2 siRNA compared to control siRNA. In contrast, Cav-2 overexpression increased THP-1 adhesion and infiltration in HUVECs.

Increased expression of Cav-2 and iba-1 was observed in brains of old mice. Moreover, there were fewer iba-1-positive cells in the brains of aged Cav-2 knockout (KO) mice than of wild-type aged mice. The levels of several chemokines were higher in brains of aged wild-type mice than in young wild-type mice; moreover, chemokine levels were significantly lower in brains of young mice as well as aged Cav-2 KO mice than in their wild-type counterparts. Expression of PECAM1 and VE-cadherin proteins increased in brains of old wild-type mice but was barely detected in brains of young wild-type and Cav-2 KO mice.

Collectively, our results suggest that Cav-2 expression increases in the endothelial cells of aged brain, and promotes leukocyte infiltration and age-associated neuroinflammation.

Link: https://doi.org/10.14348/molcells.2022.0045

Mitochondria are the power plants of the cell, several hundred working away in every cell to package the chemical energy store molecule adenosine triphosphate (ATP). At the heart of this energetic process taking place inside every mitochondrion is the electron transport chain, consisting of several complicated protein complexes, each made up of multiple subunit proteins that are manufactured from their genetic blueprints somewhat independently of one another.

Research into other complicated protein complexes, such as the proteasome, has shown that the relatively slow pace of production of one of the protein subunits can be rate-limiting to the formation of the complex as a whole. Overall function can thus be improved by increasing expression of just that one protein subunit. See the work on the β5 subunit of the fly proteasome, for example.

In today's open access paper, researchers report that a similar situation may exist for complex I of the electron transport chain in mitochondria. In the past, it has been demonstrated in animal studies that impairing expression of components of complex I can produce a compensatory response that leads to improved cell function and slower pace of aging. It is perhaps the case that increased expression of some components can also achieve a slowing of aging by compensating in part for the age-related decline in mitochondrial function.

This is probably not the best approach to the mitochondrial dysfunction of aging, however. At the present time, replacement of mitochondria throughout the body seems the most feasible near future approach, followed by systemic partial reprogramming to restore youthful gene expression of important mitochondrial proteins. The latter approach has sizable technical issues relating to delivery and tissues in which reprogramming may be harmful, while the former is really only a logistics challenge - the production of suitable mitochondria at scale, and to a high enough quality.

The membrane domain of respiratory complex I accumulates during muscle aging in Drosophila melanogaster

Studies in Drosophila have identified several genetic manipulations of mitochondrial proteins that have shown some promise in increasing lifespan. For example, induction of Dynamin-related protein 1 (Drp1), which is a major regulator of mitochondrial fission, during midlife in Drosophila increases lifespan. Similarly, forced expression of the yeast alternative NADH:ubiquinone oxidoreductase, which catalyzes the transfer of electrons from NADH to ubiquinone via FAD without pumping protons across the mitochondrial inner membrane increases lifespan. Further, overexpression of the alternative NADH:ubiquinone oxidoreductase reduces reactive oxygen species (ROS) production and increases several markers of complex 1 (CI) activity.

Paradoxically, a restrained knockdown of several CI proteins also enhances longevity. While the exact mechanisms involved in triggering the increased lifespan caused by mild CI disruption are still being unraveled, compensatory mitochondrial stress signaling cascades seem to contribute prominently. However, the question of whether boosting the expression of individual CI subunits can extend lifespan remains uncharted.

The boot-shaped respiratory complex I (CI) consists of a mitochondrial matrix and membrane domain organized into N-, Q- and P-modules. The N-module is the most distal part of the matrix domain, whereas the Q-module is situated between the N-module and the membrane domain. The proton-pumping P-module is situated in the membrane domain.

We explored the effect of aging on the disintegration of CI and its constituent subcomplexes and modules in Drosophila flight muscles. We find that the fully-assembled complex remains largely intact in aged flies. And while the effect of aging on the stability of many Q- and N-module subunits in subcomplexes was stochastic, NDUFS3 was consistently down-regulated in subcomplexes with age. This was associated with an accumulation of many P-module subunits in subcomplexes. The potential significance of these studies is that genetic manipulations aimed at boosting, perhaps, a few CI subunits may suffice to restore the whole CI biosynthesis pathway during muscle aging.

For many topics in aging for which there is presently little progress, it is nonetheless possible to find a great deal of relevant research and drug development undertaken over the past few decades. It is just that none of it managed to produce therapies, largely small molecule drugs given the primary focus of the research and development communities, that have a large enough effect to be interesting. This is the case for the improvement of cognitive function in old people. This review is a short tour through the highlights of past therapeutic development, and the summary at the end of the day is that nothing attempted to date can much improve on the effects of structured exercise programs. We can hope that this will change as more attention is given to targeting the underlying causes of aging, rather than the use of small molecules to manipulate specific protein interactions that are far downstream from those causes.

Aging is associated with cognitive impairment, including dementia and mild cognitive impairment (MCI). Successful drug development for improving or maintaining cognition in seniors is critically important. Although many novel targets are being explored for improving cognition in the past two decades, there are only several drugs approved to improve cognition in Alzheimer's disease (AD) and no drug has been approved for cognitive protection in MCI patients.

A growing number of studies show that non-pharmacological interventions can enhance cognition in the last decade. Emerging evidence indicates exercise not only promotes physical health but also contributes to the preservation of cognition function. The mechanisms account for the neuroprotective effects of exercise on the brain include evaluated neurotrophic factor levels, increased synaptogenesis, improved vascularization, decreased systemic inflammation, and reduced abnormal protein deposition.

Various pharmacological (cholinesterase inhibitors, memantine, antidiabetic agents, probiotics, cerebrolysin) and non-pharmacological interventions (cognition-oriented treatments, non-invasive brain stimulation, physical exercise, and lifestyle-related interventions) have been proposed for cognitive impairment in older people. Although a variety of new drug targets has been identified for cognition enhancement in older adults, these new drugs are still in development. The existing potential drug targets should be further exploited, and discovering new drug targets could be a solution to the lack of effective drugs. Most non-pharmacological interventions showed a small to moderate beneficial effect on cognitive function in cognitive impairment old people. Thus, combinations of pharmacological and non-pharmacological interventions or combinations of different types of non-pharmacological interventions may be more efficient in improving or preserving cognition.

Link: https://doi.org/10.3389/fnins.2022.1060556

The research community now considers chronic inflammation in brain tissue to be an important aspect of the development of neurodegenerative conditions. Unresolved inflammatory signaling is disruptive of tissue structure and function. With age, a state of chronic inflammation arises due to the presence of senescent cells, the reaction of the innate immune system to debris from stressed cells and metabolic waste such as protein aggregates, persistent viral infection, and a range of other contributing mechanisms. Therapies - such as senolytic treatments to clear senescent cells - that can suppress excess inflammation without affecting the useful, normal inflammatory reaction to injury and infection should slow down many of the manifestations of aging, including the onset of neurodegenerative conditions such as Alzheimer's disease.

Neuroinflammation exists in variety of aging-related neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), major depressive disorder (MDD), ischemic stroke, spinal cord injury, and schizophrenia. Among the many critical molecules that regulate neuroinflammation, the NLRP3 inflammasome complex was found to play important roles in cellular immune response such as during stress and infection. Recent evidence demonstrates that NLRP3-medicated neuroinflammation is involved in the pathology of neurodegenerative diseases.

Misfolded protein aggregates in neurons are well-known, cellular hallmarks in a variety of neurodegenerative diseases. Misfolded proteins and damaged organelles are degraded by inflammation-related cells such as microglia in the brain. Activated-NLRP3 inflammasome in microglia plays a key role for fighting with misfolded proteins to rescue neurons. Autophagy and ubiquitin-proteasome system in neurons also take part in the degradation or recycling of these mutant aggregates proteins. However, excessive aggregates in neurons impair the autophagy and ubiquitin protein degradation system, leading to activation of NLRP3 inflammasomes in microglia and neuronal death. Microglia activates NLRP3 inflammasomes and releases cytokines in response to toxic protein aggregates in neurodegenerative diseases.

AD is a common, age-dependent neurodegenerative disease which is characterized with the accumulation of amyloid beta (Aβ) and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein aggregates. The Aβ aggregates in brain are considered as a key pathological hallmark of AD. Interestingly, NLRP3 inflammasomes were found in AD patient's brain and animal models. Thus, approaches to degrading protein aggregates by the autophagy system and inhibit the neuroinflammation is a promising direction for the treatment of neurodegenerative diseases characterized by misfolded proteins.

Link: https://doi.org/10.3389/fnagi.2022.1102613

Mitochondria can be ejected and taken up by cells, or transferred via connections between cells, and this appears to one of the many ways in which cells communicate or attempt to assist in cases of damage. It is of great interest to the research community that intracellular mitochondria can be taken up and used by cells, given the existence of inherited diseases resulting from mitochondrial mutations, and given the late life decline in mitochondrial function that contributes to many age-related conditions. It may be possible to deliver fully functional mitochondria as a therapy, to be ingested by cells in order to repair their function.

Several startup biotech companies are working towards the infrastructure needed to use transplanted mitochondria as a therapy. To be cost-effective, these organelles would be harvested from standardized cell lines, potentially matching recipients and lines for the known human haplotypes of mitochondrial DNA. With this work in mind, it is interesting to note today's open access paper, in which researchers provide evidence for transplanted mitochondrial to be taken up preferentially by damaged cells. This is good news, provided that the mechanism of selective uptake operates in cells with age-damaged mitochondria as well as in those where mitochondrial function is compromised by other means.

Preferred Migration of Mitochondria toward Cells and Tissues with Mitochondrial Damage

Mitochondria play a fundamental role in cellular survival and growth by supplying energy in the form of ATP via oxidative phosphorylation. Isolated mitochondria can be transferred to any cell type via simple coincubation or brief centrifugation in vitro. Isolated mitochondria can also be internalized into tissues through local or systemic injection in vivo. It was suggested that mitochondrial internalization would be mediated by micropinocytosis or actin-dependent endocytosis. In animal models and patients, the injection of autologous or nonautologous mitochondria has been effective in treating injury and diseases, including ischemia/reperfusion injury, spinal cord injury, mouse fatty liver, cognitive deficits, inflammatory diseases, and Parkinson's disease.

Although the underlying mechanisms of such effects are not fully understood, it has been suggested that the transfer of healthy mitochondria (or mitochondrial transplantation) ameliorates mitochondrial defects and helps recover cellular function by increasing mitochondrial biogenesis or replacing abnormal mitochondria with healthy mitochondria. Recently, our data have demonstrated that mitochondrial transplantation attenuated the lipopolysaccharide-induced inflammation in vitro and in vivo by blockade of the activity of NFκB. Therefore, the transfer of fully functional mitochondria into defective cells or tissues could be an effective therapeutic strategy for treating mitochondrial dysfunction.

The key to successful mitochondrial transplantation therapy is the trafficking of mitochondria to the target cells, in which they can exert their biological effects. Therefore, systemically administrated mitochondria must have abilities that guide them to the sites with mitochondrial damage. Intravenously injected mitochondria might localize preferentially to damaged tissues; mitochondrial trafficking to the sites of injury is not well studied, however.

In the present study, we isolated mitochondria conjugated with green fluorescent protein (MTGFP) from stable HEK293 cells expressing TOM20 fused to an upstream green fluorescent protein (GFP). In a coculture system, MTGFP was internalized in a cell type-specific manner. We also found that selective MTGFP transplantation depended on the mitochondrial function of the receiving fibroblasts. Furthermore, compared with MTGFP injected intravenously into normal mice, MTGFP injected intravenously into bleomycin-induced idiopathic pulmonary fibrosis (IPF) mice located more abundantly in the lung tissue, suggesting that mitochondrial trafficking to damaged cells and tissues occurred.

Senescent cells accumulate in tissues throughout the body with age. Their pro-inflammatory, pro-growth signaling is disruptive of tissue structure and function, and has been implicated in the development of aneurysms. An aneurysm is a weakened area of the blood vessel wall, expanding under pressure to form a pocket vulnerable to rupture. This can be fatal, depending on location, such as in a major artery or the brain. Researchers here look at aortic tissues and find raised levels of oxidative signaling, shorter telomeres, and more cellular senescence in these tissues where aneurysms are present.

Aortic aneurysms are characterized by local inflammation with degeneration around the aorta, leading to vessel weakening and dilatation. Degenerative remodeling in the medial layer of aortic aneurysm tissue is characterized by loss of vascular smooth muscle cells (vSMC) and destruction of the extracellular matrix (ECM). This medial degeneration leads to weakening and progressive dilatation of the vascular wall, and ultimately results in aortic dissection or aneurysm rupture.

Telomere shortening is a predictor of age-related diseases, and its progression is associated with premature vascular disease. The aim of the present work was to investigate the impacts of chronic hypoxia and telomeric DNA damage on cellular homeostasis and vascular degeneration of thoracic aortic aneurysm (TAA). We analyzed healthy and aortic aneurysm specimens (215 samples) for telomere length, chronic DNA damage, and resulting changes in cellular homeostasis, focusing on senescence and apoptosis.

Compared with healthy thoracic aorta, patients with tricuspid aortic valve (TAV) showed telomere shortening with increasing aneurysm size, in contrast to genetically predisposed bicuspid aortic valve (BAV). In addition, telomere length was associated with chronic hypoxia and telomeric DNA damage and with the induction of senescence-associated secretory phenotype (SASP). Aneurysm in TAV specimens showed a significant difference in SASP-marker expression of IL-6, NF-κB, mTOR, and cell-cycle regulators (γH2AX, Rb, p53, p21), compared to healthy thoracic aorta and and aneurysm in BAV. We conclude that chronic hypoxia is associated with telomeric DNA damage and the induction of SASP in a diseased aortic wall, promising a new therapeutic target.

Link: https://doi.org/10.3390/ijms232415498

The primary approach to assessing neurodegeneration presently involves comparatively expensive imaging technologies. Better, less onerous ways to determine the early onset and later progression of Alzheimer's disease will hopefully enable greater screening of patients in the earliest stages of the condition, and drive greater efforts to find effective ways to prevent and reverse Alzheimer's disease. Researchers here report on an improvement in the assessment of tau protein that finds its way into the bloodstream from the brain, making it a viable biomarker for Alzheimer's disease, where in the past it was difficult to establish a correlation.

The biomarker, called "brain-derived tau," or BD-tau, outperforms current blood diagnostic tests used to detect Alzheimer's-related neurodegeneration clinically. It is specific to Alzheimer's disease and correlates well with Alzheimer's neurodegeneration biomarkers in the cerebrospinal fluid (CSF). Current blood diagnostic methods can accurately detect abnormalities in plasma amyloid beta and the phosphorylated form of tau, but the biggest hurdle lies in the difficulty of detecting markers of neurodegeneration that are specific to the brain and aren't influenced by potentially misleading contaminants produced elsewhere in the body. 

For example, blood levels of neurofilament light, a protein marker of nerve cell damage, become elevated in Alzheimer's disease, Parkinson's and other dementias, rendering it less useful when trying to differentiate Alzheimer's disease from other neurodegenerative conditions. On the other hand, detecting total tau in the blood proved to be less informative than monitoring its levels in CSF. Researchers have now developed a technique to selectively detect BD-tau while avoiding free-floating "big tau" proteins produced by cells outside the brain, however.

To do that, they designed a special antibody that selectively binds to BD-tau, making it easily detectible in the blood. They validated their assay across over 600 patient samples from five independent cohorts, including those from patients whose Alzheimer's disease diagnosis was confirmed after their deaths, as well as from patients with memory deficiencies indicative of early-stage Alzheimer's. The tests showed that levels of BD-tau detected in blood samples of Alzheimer's disease patients using the new assay matched with levels of tau in the CSF and reliably distinguished Alzheimer's from other neurodegenerative diseases. Levels of BD-tau also correlated with the severity of amyloid plaques and tau tangles in the brain tissue confirmed via brain autopsy analyses.

Link: https://www.upmc.com/media/news/122722-alzheimers-neurodegeneration

The Strategies for Engineered Negligible Senescence (SENS) view of the relevance of mitochondrial DNA damage to aging is that certain types of damage, large deletions for example, can produce pathological mitochondria that are both broken and able to outcompete their peers. Clones of the original damaged mitochondrion take over a cell, turning it into an exporter of large amounts of damaging reactive molecules. Only a small number of cells are affected by this type of damage in aged tissues, but it doesn't take that many cells acting in this way to produce pervasive changes to the signaling environment, as well as significant amounts of toxic, oxidized lipids and other molecules.

The fix for this problem is to copy mitochondrial genes into the nuclear genome, suitably altered to allow the proteins produced to find their way back to mitochondria where they are needed. With a backup supply of proteins, mitochondrial DNA deletions produce little to no effect on mitochondrial function. This process is known as allotopic expression, and is a work in progress at the SENS Research Foundation and a few other labs and ventures, such as Gensight Biologics, only achieved for a few of the thirteen necessary genes. Once it is ready, however, how to deliver this technology to the cells that need it?

The cutting edge of gene therapy delivery technology is still far removed from able to alter the genome of every cell in the adult body in a carefully defined way. Even setting aside the nature of the vector itself, reliably introducing that vector into a sizable fraction of all cells in a tissue is still a challenge. Further, viral and transposon based vectors introduce their genetic material into the genome haphazardly, potentially breaking existing genes, and creating a variable number of insertion sites. Equally problematic, most vectors are size-limited, meaning one couldn't insert more than one or two genes, not all thirteen mitochondrial genes at once. CRISPR gene editing technologies can perform targeted insertions, but not of meaningfully large sequences, for example.

As today's materials from the SENS Research Foundation staff note, all of this collectively presents a challenge. It is possible to build a highly efficient system for safe insertion of arbitrarily large numbers of therapeutic genes, and the SENS Research Foundation team has done so, provided one already has a suitable docking site in the genome. Getting that docking site into place, however, returns to the issue of whether one can suitably deliver a gene therapy broadly in the tissue of interest, targeted only to the cells of interest. It is a tough problem, but one that will likely be addressed in some way in the years ahead, given the strong interest in enabling the broader use of gene therapies.

SENSible Question: Delivering MitoSENS

From our earliest days, SENS Research Foundation has funded allotopic expression (AE) work in outside labs and had our in-house MitoSENS scientists laser-focused on the core biotechnology required to achieve all of that in cells. That's a sufficiently challenging and underinvested area of rejuvenation biotechnology to make it one of the best ways to get a healthy longevity bang for our donors' bucks. But once our and other scientists have developed allotopic constructs for all thirteen of the genes encoded in the mitochondrial DNA that work perfectly, we still need to get it into our cells to make it work! So your question is: how will we do that?

The first thing to point out is that the sheer scale of the problem isn't nearly as intimidating as the question assumes. Yes, there are some 30-37 trillion cells in the human body - but not all cells are high-priority targets for AE, and we can ignore a few cell types entirely. Most notably, red blood cells alone account for some 84% of all the cells in the human body, and they (uniquely) don't even contain mitochondria! With nothing there, there's nothing to break - or to fix.

But all right: every other cell in the body has mitochondria. However, although mitochondrial DNA can suffer mutations in any cell that bears mitochondria, only a tiny fraction of such mutations cause problems that meaningfully impact the rate of aging or impair our health. Where MitoSENS is badly needed is to supply a backup system in cell types that last for decades and don't divide - cells like brain neurons, heart muscle cells, and skeletal muscle fiber segments. The cells of interest are a small fraction of postmitotic cells in which the entire cell is overtaken by mitochondria that all bear the same single large deletion. This problem is even more prominent in Alzheimer's disease and Parkinson's disease, as well as in aging muscle and other particular diseases and disabilities of aging. And this takeover not only isn't constrained by the cell's mitophagy quality control machinery: perversely, it seems to be driven by it. It's for these cells that a robust mitochondrial damage-repair strategy is most clearly and most urgently needed. And to return to the question of scale: as a fraction of the body's cells, they are a tiny minority. Neurons comprise only about 0.03% of all the cells in the body, and muscle cells only 0.001%. However, that's still in the order of 100 billion neurons to engineer! So how are we going to do that?

Several potential gene therapy approaches are currently or soon to be used in human clinical trials, but none that are up to the task of delivering rejuvenation biotechnologies like AE that require it. Phage integrases would be a powerful alternative gene therapy technology for AE - if they can be made to work for humans. Phages are a kind of virus that naturally infects bacteria, not people. But there are compelling reasons to harness them for gene therapy if we can. First, they can insert gene constructs of essentially any size into their target site in the genomes of organisms they infect. Second, unlike AAVs, phage integrases will almost never insert their genetic payload anywhere but a few specific, non-disruptive, "safe" places in the genome - and for structural reasons, their genetic payload is highly unlikely to insert itself elsewhere in the genome independent of the integrase.

That sounds like exactly what we need! So the main challenge - and it's a big one! - is that phage integrases are designed to insert viral genes into bacterial genomes: the safe "docking site" that they target is not naturally present in either mice or humans. Thus first, hardwire the "docking site" into the genome of the mouse or human in whom you want to deliver therapies. Then you're free to use the more powerful phage integrase to safely deliver as large a construct as you like. For testing candidate rejuvenation biotechnologies in animal studies, you can engineer the docking site into a line of mice, which will then be born ready to receive new candidate gene therapies via phage integrases at any point in the lifespan. SENS Research Foundation began funding the development of these "Maximally-Modifiable Mice" (MMM) almost a decade ago, and our in-house MitoSENS team is now using them to test allotopic expression in living mice.

This is a critical step in proving out the engineered phage integrase system as a platform for gene therapy, and advancing AE from a technical achievement in cell biology into a working rejuvenation biotechnology that can keep our mitochondria cranking out cellular energy, even in the face of age-related mutations. But as you'll probably have noticed, there's just one problem: humans aren't born with a phage integrase docking site engineered into our genomes! Let's be frank about this: we don't yet know how exactly we will get the docking site engineered into all of the cells - or even all the high-priority cells for AE - of a person. Getting the docking site inserted into all of these cells using other gene therapy approaches will be challenging. But it's nothing compared to the alternative: delivering each and every one of the 13 mitochondrially-encoded proteins individually into all the not-previously-modified cells that need them using those same flawed tools.

Persistent viral infection, such as by HPV, can result in cancer. Researchers here suggest that senolytic therapies to clear senescent cells can reduce that risk by removing some fraction of the cells most impacted by persistent infection. Senescent cells accumulate with age, but it is becoming clear that they are problematic in many other contexts as well. The ability to remove excess senescent cells with a single treatment via any one of the senolytic therapies under development is a powerful form of intervention that may have many applications beyond the rejuvenation of old tissues.

Senescence represents a unique cellular stress response characterized by a stable growth arrest, macromolecular alterations, and wide spectrum changes in gene expression. Classically, senescence is the end-product of progressive telomeric attrition resulting from the repetitive division of somatic cells. In addition, senescent cells accumulate in premalignant lesions, in part, as a product of oncogene hyperactivation, reflecting one element of the tumor suppressive function of senescence. Oncogenic processes that induce senescence include overexpression/hyperactivation of H-Ras, B-Raf, and cyclin E as well as inactivation of PTEN.

Oncogenic viruses, such as Human Papilloma Virus (HPV), have also been shown to induce senescence. High-risk strains of HPV drive the immortalization, and hence transformation, of cervical epithelial cells via several mechanisms, but primarily via deregulation of the cell cycle, and possibly, by facilitating escape from senescence. Despite the wide and successful utilization of HPV vaccines in reducing the incidence of cervical cancer, this measure is not effective in preventing cancer development in individuals already positive for HPV. Accordingly, in this commentary, we focus on the potential contribution of oncogene and HPV-induced senescence (OIS) in cervical cancer. We further consider the potential utility of senolytic agents for the elimination of HPV-harboring senescent cells as a strategy for reducing HPV-driven transformation and the risk of cervical cancer development.

Link: https://doi.org/10.3390/ijms232415512

The gut microbiome changes with age, the balance of microbial populations shifting in ways that contribute to degenerative aging. There are more inflammatory microbes, more microbes generating harmful metabolites, and fewer microbes generating beneficial metabolites. One of the ways to address this issue is to transplant fecal matter from a young individual into the gut of the older individual. The result is a lasting improvement in the gut microbiome, and consequent improvement in health. Here, researchers look specifically at muscle and skin function in aged mice following fecal microbiota transplant from young mice, and find improvements.

Aging is a natural process that an organism gradually loses its physical fitness and functionality. Great efforts have been made to understand and intervene in this deteriorating process. The gut microbiota affects host physiology, and dysbiosis of the microbial community often underlies the pathogenesis of host disorders. The commensal microbiota also changes with aging; however, the interplay between the microbiota and host aging remains largely unexplored. Here, we systematically examined the ameliorating effects of the gut microbiota derived from the young on the physiology and phenotypes of the aged.

As the fecal microbiota was transplanted from young mice at 5 weeks after birth into 12-month-old ones, the thickness of the muscle fiber and grip strength were increased, and the water retention ability of the skin was enhanced with thickened stratum corneum. Muscle thickness was also marginally increased in 25-month-old mice after transferring the gut microbiota from the young. Bacteria enriched in 12-month-old mice that received the young-derived microbiota significantly correlated with the improved host fitness and altered gene expression. In the dermis of these mice, transcription of Dbn1 was most upregulated and DBN1-expressing cells increased twice.

We revealed that the young-derived gut microbiota rejuvenates the physical fitness of the aged by altering the microbial composition of the gut and gene expression in muscle and skin. Dbn1, for the first time, was found to be induced by the young microbiota and to modulate skin hydration. Our results provide solid evidence that the gut microbiota from the young improves the vitality of the aged.

Link: https://doi.org/10.1186/s40168-022-01386-w

Memory is in some way encoded in the synaptic connections between neurons, with the precise details yet to be determined. Destruction of synapses is a characteristic of neurodegenerative conditions involving loss of memory. Researchers here identify a regulatory receptor that controls the removal of synapses by the innate immune cells known as microglia in the brains of mice. Blocking the activity of this receptor reduces age-related memory loss in mice, suggesting that this aspect of aging is largely a matter of inappropriate microglial activity, destroying synapses that should remain intact.

Removal of synapses is not a bad thing per se, and is thought to be a necessary part of neural plasticity, essential for memory and learning. A range of evidence suggests that excessive synaptic removal might take place in an aged brain, however. This may be driven by chronic inflammation, a state the provokes microglia into excessive activity, but this is by no means certain. There is much yet to explore regarding the underlying mechanisms.

P2Y6 receptor-dependent microglial phagocytosis of synapses mediates synaptic and memory loss in aging

Microglia are central nervous system macrophages, specialized in the phagocytosis (i.e., engulfment and degradation) of bacteria, synapses, neurons, debris, and aggregated proteins. Microglia can phagocytose synapses during development, neuropathology, and aging, and microglia can also phagocytose dendrites, axons, and intact neurons. Microglial phagocytosis of neuronal structures is mediated by eat-me signals, opsonins, and phagocytic receptors. Interestingly, it has been shown that genetic knockout of the opsonin C3 reduced aging-induced loss of hippocampal synapses, neurons, and memory; and similarly, knockout of the phagocytic receptor TREM2 reduced aging-induced hippocampal synaptic and neuronal loss in mice. Thus, one may hypothesize that the neuroinflammation accompanying aging drives microglial phagocytosis of synapses, resulting in memory impairment and brain atrophy. Microglial biology changes with age, including upregulated expression of phagocytic receptors and opsonins, potentially resulting in excessive phagocytosis of the aging brain.

The P2Y6 receptor (P2Y6R, expressed from the P2ry6 gene) is a microglial receptor that mediates microglial phagocytosis of neurons. P2Y6R is expressed by multiple cell types in the body, but within the brain is almost exclusively expressed by microglia. Damaged or stressed neurons release the nucleotide UTP, which is rapidly degraded into UDP by extracellular nucleotide-degrading enzymes, and localized UDP then activates the P2Y6R on microglia to engulf such neurons. We have shown that activating P2Y6R causes microglia to engulf live neurons, and P2Y6R deficiency prevents lipopolysaccharide (LPS)-induced microglial phagocytosis of neurons both in vitro and in vivo. Moreover, P2Y6R knockout mice were also resistant to memory loss induced by beta-amyloid and extracellular tau. These previous studies lead us to ask whether (i) P2Y6R mediates microglial phagocytosis of synapses, and (ii) the synaptic and memory loss induced by natural aging of mice was also mediated by P2Y6R.

We found that aging wild-type mice to 17 months of age resulted in synapse and memory loss, whereas P2Y6R knockout mice had preserved memory. Microglia from 17-month-old wild-type mice had an age-associated increase in the internalization of synaptic material, but no such increase was observed in microglia from 17-month-old knockout mice. Moreover, we show here that inactivation of P2Y6R decreases microglial phagocytosis of isolated synapses (synaptosomes) and synaptic loss in neuronal-glial co-cultures. These findings are significant as they support the hypothesis that microglial phagocytosis of synapses contributes to aging-induced memory loss, and, more specifically, that inhibition of the P2Y6R may prevent this memory loss.

Long term restriction of dietary methionine intake is known to extend life in short-lived mammals. Methionine sensing is one of the triggers for the calorie restriction response, improving cell maintenance and adjusting metabolism into a state more resilient to the ongoing generation of molecular damage that contributes to degenerative aging. Researchers here note that methionine levels are lower in the heart tissue of longer-lived mammals, suggesting that altered methionine metabolism, maintaining lower levels of methionine in and around cells, is one of the adaptations that allows long-lived mammals to be long-lived. This may also go some way towards explaining why calorie restriction and related strategies such as methionine restriction have a lesser effect on life span in longer-lived species. Calorie restriction can increase mouse life span by as much as 40%, but cannot add more than a few years to human life span.

Long-lived species have evolved by reducing the rate of aging, which is an inherent consequence of oxidative metabolism. Hence, species that live longer benefit from more efficient intracellular metabolic pathways, including lipid, protein, and carbohydrate metabolism. The aim of this work is to determine whether the content of proteins' building blocks, named amino acids, are related with mammalian longevity. This was accomplished by analyzing the amino acid content in the hearts of seven mammalian species with a longevity ranging from 3.8 to 57 years.

Our findings demonstrate that the heart's content of amino acids differs between species and is globally lower in long-lived species. Moreover, long-lived species have lower content of amino acids containing sulfur, such as methionine and its related metabolites. Methionine constitutes a central hub of intracellular metabolic adaptations leading to an extended longevity. Our results support the existence of metabolic adaptations in terms of sulfur-containing amino acids. As has been described previously, our work supports the idea that the human population could benefit from reduced calorie intake, which would lead to reduced age-related diseases and healthier aging.

Link: https://doi.org/10.3390/biology11121821

Risk of cancer is a function of cell numbers and division rates, but also of the efficiency of cancer suppression mechanisms. In order for a species to evolve a longer life span, cancer suppression must improve. In order for a species to evolve a larger body mass, cancer suppression must improve. As this paper notes, comparatively little is definitively known of the anti-cancer strategies of various long-lived mammals. Elephants duplicate the tumor suppressor gene TP53, but that doesn't occur in other large and long-lived species, so it is likely that each species takes its own path. It is far too early to say whether what can be learned from this line of research into comparative biology might lead to ways to suppress cancer risk in humans.

The first indications that elephant lineage contains genetic strategies to enhance cancer protection mechanisms came from studies that found that elephants have a lower cancer rate than expected based on their body size compared with other mammalian species. This was related to multiple copies of the TP53 gene, widely known as a crucial tumor suppressor gene (TSG), preventing the growth and survival of potentially malignant cells. While most mammals have only one TP53 copy in their genome, the African bush elephant genome contains 19 extra copies of TP53, 9 to 20 copies were identified in the Asian elephant genome, and 21 to 24 copies were found in the African forest elephant genomes.

Many genomes of giant whales have been sequenced thus far but did not reveal duplications of TP53 similar to those in elephants, suggesting that they evolved different anticancer adaptations. Comparative genomics in the bowhead whale, the longest-lived whale, identified genes under positive selection and specific mutations in genes linked to cancer, aging, the cell cycle, and DNA repair, but without conclusive experiments. Researchers reported signals of positive selection in seven TSGs: CXCR2, ADAMTS8, ANXA1, DAB2, DSC3, EPHA2, and TMPRSS11A. Moreover, they revealed that the turnover rate of TSGs was almost 2.4 times faster in cetaceans than in other mammals, showing 71 duplicated genes in at least one of the Cetaceans species. Most duplication events and positively selected genes were identified in the lineage of large baleen whales, suggesting that they have evolved additional anticancer mechanisms.

As in other mammalian lineages, the maximum life span and body mass are correlated in primates, and the great apes are the largest body size and long-lived species among them. Researchers found only five genes with positive selection signals for the great ape lineage (IRF3, SCRN3, DIAPH2, GASK1B, and SELENO), all of which have functions related to cancer development and inflammatory responses. The results show that the evolution of strategies for cancer resistance in the primate lineage is quite diverse, with modifications that can be found at the coding, expression, and regulatory levels, and that although the great apes lineage provides evidence of specific changes capable of giving greater longevity to the species of the group, the understanding of the relationship with cancer resistance is still developing for nonhuman species and needs to be further investigated.

Bats have exceptional longevity given their body size, but there is still little data on how they evolved their extended lifespan and resisted cancer. Previous studies found reduced GH-IGF1 signaling associated with increased resistance to cancer. Additionally, it has been reported that long-lived bats have resilient telomeres that remain long despite advanced age. Also, bats do not show an increased level of mitochondrial damage given their metabolic rate, suggesting that this group evolved adaptations in their DNA repair and maintenance mechanisms. These molecular adaptations were underpinned by a study showing that bats exhibit a unique age-related regulation of genes associated with DNA repair, immunity, and tumor suppression that underlies extended bat longevity. Furthermore, it was reported that long-lived bats possess specific miRNAs that function as tumor suppressors. This provides a new potential molecular mechanism to decrease cancer risk not yet identified in any other lineage.

Link: https://doi.org/10.1590/1678-4685-GMB-2022-0133