Large-scale chemical screen identifies Gallic acid as a geroprotector for human stem cells

The Antiaging Potential of Dietary Plant-Based Polyphenols: A Review on Their Role in Cellular Senescence Modulation

Aging is a complex biological process characterized by a progressive decline in physiological functions and an increased risk of chronic diseases. A key mechanism of this process is cellular senescence, the permanent arrest of the cell cycle in response to stress or damage, which contributes to the accumulation of dysfunctional cells in tissues. Recent research has highlighted the role of polyphenols, bioactive compounds present in numerous plant-based foods, in positively modulating these processes. Polyphenols exert antioxidant effects, regulate gene expression and improve mitochondrial function, helping to delay cellular aging and prevent age-related diseases. In addition, some polyphenols exhibit senolytic properties, selectively eliminating senescent cells and promoting tissue regeneration. This review summarizes the current evidence on the effects of polyphenols on aging and cellular senescence, exploring the underlying molecular mechanisms and discussing their potential in nutritional strategies aimed at promoting healthy aging.

Antioxidant and Anti-Senescence Polyvinyl Alcohol-Gallic Acid Supramolecular Hydrogels for Stem Cell Culture

Replicative senescence presents a significant challenge in mesenchymal stem cell (MSC) expansion due to high reactive oxygen species (ROS) levels generated during culture. Elevated ROS levels lead to oxidative stress, cellular damage, and senescence, limiting the biomedical applications of MSCs. In this study, a supramolecular thermo-reversible hydrogel composed of the natural polyphenolic compound gallic acid (GA) and polyvinyl alcohol (PVA) was designed to scavenge ROS and mitigate MSC senescence. The PVA-GA hydrogel, stabilized by strong hydrogen bonding forces, exhibited an elastic modulus comparable to that of human soft tissue and facilitated the sustained release of GA over 14 days. It enhanced MSC survival, protected against oxidative stress, reduced intracellular ROS levels, diminished mitochondrial damage, and decreased cellular senescence. The hydrogel maintained the multilineage differentiation potential and typical phenotype of MSCs. Additionally, it preserved vascular endothelial growth factor (VEGF) secretion from MSCs under oxidative stress and enhanced their pro-angiogenic effect. The conditioned medium derived from MSCs in the hydrogel group promoted migration and tube formation of human umbilical vein endothelial cells (HUVECs). These findings suggest that the PVA-GA hydrogel holds significant promise for the biomedical applications of MSCs, potentially addressing the challenges posed by oxidative stress and cellular senescence.

Roles of chromatin and genome instability in cellular senescence and their relevance to ageing and related diseases

Ageing is a complex biological process in which a gradual decline in physiological fitness increases susceptibility to diseases such as neurodegenerative disorders and cancer. Cellular senescence, a state of irreversible cell-growth arrest accompanied by functional deterioration, has emerged as a pivotal driver of ageing. In this Review, we discuss how heterochromatin loss, telomere attrition and DNA damage contribute to cellular senescence, ageing and age-related diseases by eliciting genome instability, innate immunity and inflammation. We also discuss how emerging therapeutic strategies could restore heterochromatin stability, maintain telomere integrity and boost the DNA repair capacity, and thus counteract cellular senescence and ageing-associated pathologies. Finally, we outline current research challenges and future directions aimed at better comprehending and delaying ageing.

Unraveling anti-aging mystery of green tea in C. elegans: Chemical truth and multiple mechanisms

Tea drinking impacts aging and aging-related diseases. However, knowledge of anti-aging molecules other than the major catechins in complex tea extracts remains limited. Here we used Caenorhabditis elegans to analyze the longevity effects of tea extracts and constituents comprehensively. We found that the hot water extract of green tea prolonged lifespan and heathspan. Further, the MeOH fraction prolonged lifespan significantly longer than other fractions. Correlation analysis between mass spectroscopic data and anti-aging activity suggests that ester-type catechins (ETCs) are the major anti-aging components, including 4 common ETCs, 6 phenylpropanoid-substituted ester-type catechins (PSECs), 5 cinnamoylated catechins (CCs), 7 ester-type flavoalkaloids (ETFs), and 4 cinnamoylated flavoalkaloids (CFs). CFs (200 μM) are the strongest anti-aging ETCs (with the longest 73% lifespan extension). Green tea hot water extracts and ETCs improved healthspan by enhancing stress resistance and reducing ROS accumulation. The mechanistic study suggests that they work by multiple pathways. Moreover, ETCs modulated gut microbial homeostasis, increased the content of short-chain fatty acids, and reduced fat content. Altogether, our study provides new evidence for the anti-aging benefits of green tea and insights into a deep understanding of the chemical truth and multi-target mechanism.

Ameliorative effect and underlying mechanism of the Xiaxue Kaiqiao formula on age-related dementia in Samp8 mice

BACKGROUND

Dementia, a major symptom of several neurodegenerative diseases, can be improved by acetylcholinesterase inhibitors (AChE); however, due to the complex etiology and long course of dementia, the efficacy of these drugs remains limited. Significant empirical evidence shows that traditional Chinese medicine (TCM) markedly ameliorates intractable disease; nevertheless, a suitable regimen has yet to be widely accepted, which is likely the result of gaps in the understanding of its causality. We propose that taking advantage of the TCM theory of collateral activation and prevention of accumulation by purgation may improve dementia treatment; thus, we designed the Xiaxue Kaiqiao formula (XKF) accordingly.

PURPOSE

To explore the ameliorative effect and underlying mechanism of XKF on dementia in a Samp8 mouse model.

METHODS

Samp8 mice were treated with XKF for eight weeks, and the amelioration of dementia was subsequently assessed using the novel object recognition, Barnes maze, and open-field behavioral tests. Neuropathological alterations were observed by immunofluorescence (IF) and Golgi staining of brain tissue. Drug safety was evaluated by blood biochemical tests, organ coefficients, and hematoxylin-eosin (H&E) staining. Proteomics analysis was performed on frozen brain tissue using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Behavioral testing revealed that the administration of XKF had significant ameliorative effects on memory discrimination, spatial learning memory, and anxiety in Samp8 mice. IF staining showed that XKF reduced the loss of postsynaptic density protein 95 (PSD95), myelin, neurons, and axons, as well as decreased the proliferation of astrocytes and microglia in the hippocampal and temporal lobe regions. Evaluation of drug safety demonstrated no abnormal organ morphology following XKF treatment.

CONCLUSION

XKF treatment improved the symptoms of dementia in Samp8 mice, indicating the potential for clinical application. The mechanism underlying the ameliorative effect of XKF on dementia is likely increased synaptic transmission between neurons. Our data provide reliable evidence for the TCM theory of collateral activation and prevention of accumulation by purgation.

Disorganized chromatin hierarchy and stem cell aging in a male patient of atypical laminopathy-based progeria mandibuloacral dysplasia type A

Studies of laminopathy-based progeria offer insights into aging-associated diseases and highlight the role of LMNA in chromatin organization. Mandibuloacral dysplasia type A (MAD) is a largely unexplored form of atypical progeria that lacks lamin A post-translational processing defects. Using iPSCs derived from a male MAD patient carrying homozygous LMNA p.R527C, premature aging phenotypes are recapitulated in multiple mesenchymal lineages, including mesenchymal stem cells (MSCs). Comparison with 26 human aging MSC expression datasets reveals that MAD-MSCs exhibit the highest similarity to senescent primary human MSCs. Lamina-chromatin interaction analysis reveals reorganization of lamina-associating domains (LADs) and repositioning of non-LAD binding peaks may contribute to the observed accelerated senescence. Additionally, 3D genome organization further supports hierarchical chromatin disorganization in MAD stem cells, alongside dysregulation of genes involved in epigenetic modification, stem cell fate maintenance, senescence, and geroprotection. Together, these findings suggest LMNA missense mutation is linked to chromatin alterations in an atypical progeroid syndrome.

Genetic and Epigenetic Interactions Involved in Senescence of Stem Cells

Cellular senescence is a permanent condition of cell cycle arrest caused by a progressive shortening of telomeres defined as replicative senescence. Stem cells may also undergo an accelerated senescence response known as premature senescence, distinct from telomere shortening, as a response to different stress agents. Various treatment protocols have been developed based on epigenetic changes in cells throughout senescence, using different drugs and antioxidants, senolytic vaccines, or the reprogramming of somatic senescent cells using Yamanaka factors. Even with all the recent advancements, it is still unknown how different epigenetic modifications interact with genetic profiles and how other factors such as microbiota physiological conditions, psychological states, and diet influence the interaction between genetic and epigenetic pathways. The aim of this review is to highlight the new epigenetic modifications that are involved in stem cell senescence. Here, we review recent senescence-related epigenetic alterations such as DNA methylation, chromatin remodeling, histone modification, RNA modification, and non-coding RNA regulation outlining new possible targets for the therapy of aging-related diseases. The advantages and disadvantages of the animal models used in the study of cellular senescence are also briefly presented.

The sirtuin-associated human senescence program converges on the activation of placenta-specific gene PAPPA

Sirtuins are pro-longevity genes with chromatin modulation potential, but how these properties are connected is not well understood. Here, we generated a panel of isogeneic human stem cell lines with SIRT1-SIRT7 knockouts and found that any sirtuin deficiency leads to accelerated cellular senescence. Through large-scale epigenomic analyses, we show how sirtuin deficiency alters genome organization and that genomic regions sensitive to sirtuin deficiency are preferentially enriched in active enhancers, thereby promoting interactions within topologically associated domains and the formation of de novo enhancer-promoter loops. In all sirtuin-deficient human stem cell lines, we found that chromatin contacts are rewired to promote aberrant activation of the placenta-specific gene PAPPA, which controls the pro-senescence effects associated with sirtuin deficiency and serves as a potential aging biomarker. Based on our survey of the 3D chromatin architecture, we established connections between sirtuins and potential target genes, thereby informing the development of strategies for aging interventions.

Emerging epigenetic insights into aging mechanisms and interventions

Epigenetic dysregulation emerges as a critical hallmark and driving force of aging. Although still an evolving field with much to explore, it has rapidly gained significance by providing valuable insights into the mechanisms of aging and potential therapeutic opportunities for age-related diseases. Recent years have witnessed remarkable strides in our understanding of the epigenetic landscape of aging, encompassing pivotal elements, such as DNA methylation, histone modifications, RNA modifications, and noncoding (nc) RNAs. Here, we review the latest discoveries that shed light on new epigenetic mechanisms and critical targets for predicting and intervening in aging and related disorders. Furthermore, we explore burgeoning interventions and exemplary clinical trials explicitly designed to foster healthy aging, while contemplating the potential ramifications of epigenetic influences.

Stress, epigenetics, and aging: Unraveling the intricate crosstalk

Aging, as a complex process involving multiple cellular and molecular pathways, is known to be exacerbated by various stresses. Because responses to these stresses, such as oxidative stress and genotoxic stress, are known to interplay with the epigenome and thereby contribute to the development of age-related diseases, investigations into how such epigenetic mechanisms alter gene expression and maintenance of cellular homeostasis is an active research area. In this review, we highlight recent studies investigating the intricate relationship between stress and aging, including its underlying epigenetic basis; describe different types of stresses that originate from both internal and external stimuli; and discuss potential interventions aimed at alleviating stress and restoring epigenetic patterns to combat aging or age-related diseases. Additionally, we address the challenges currently limiting advancement in this burgeoning field.

Hepatocyte reprogramming in liver regeneration: Biological mechanisms and applications

The liver is one of the few organs that retain the capability to regenerate in adult mammals. This regeneration process is mainly facilitated by the dynamic behavior of hepatocytes, which are the major functional constituents in the liver. In response to liver injury, hepatocytes undergo remarkable alterations, such as reprogramming, wherein they lose their original identity and acquire properties from other cells. This phenomenon of hepatocyte reprogramming, coupled with hepatocyte expansion, plays a central role in liver regeneration, and its underlying mechanisms are complex and multifaceted. Understanding the fate of reprogrammed hepatocytes and the mechanisms of their conversion has significant implications for the development of innovative therapeutics for liver diseases. Herein, we review the plasticity of hepatocytes in response to various forms of liver injury, with a focus on injury-induced hepatocyte reprogramming. We provide a comprehensive summary of current knowledge on the molecular and cellular mechanisms governing hepatocyte reprogramming, specifically in the context of liver regeneration, providing insight into potential applications of this process in the treatment of liver disorders, including chronic liver diseases and liver cancer.

Reducing oxidative protein folding alleviates senescence by minimizing ER-to-nucleus H2 O2 release

Oxidative protein folding occurs in the endoplasmic reticulum (ER) to generate disulfide bonds, and the by-product is hydrogen peroxide (H2 O2 ). However, the relationship between oxidative protein folding and senescence remains uncharacterized. Here, we find that the protein disulfide isomerase (PDI), a key oxidoreductase that catalyzes oxidative protein folding, accumulated in aged human mesenchymal stem cells (hMSCs) and deletion of PDI alleviated hMSCs senescence. Mechanistically, knocking out PDI slows the rate of oxidative protein folding and decreases the leakage of ER-derived H2 O2 into the nucleus, thereby decreasing the expression of SERPINE1, which was identified as a key driver of cell senescence. Furthermore, we show that depletion of PDI alleviated senescence in various cell models of aging. Our findings reveal a previously unrecognized role of oxidative protein folding in promoting cell aging, providing a potential target for aging and aging-related disease intervention.

MAVS Antagonizes Human Stem Cell Senescence as a Mitochondrial Stabilizer

Mitochondrial dysfunction is a hallmark feature of cellular senescence and organ aging. Here, we asked whether the mitochondrial antiviral signaling protein (MAVS), which is essential for driving antiviral response, also regulates human stem cell senescence. To answer this question, we used CRISPR/Cas9-mediated gene editing and directed differentiation techniques to generate various MAVS-knockout human stem cell models. We found that human mesenchymal stem cells (hMSCs) were sensitive to MAVS deficiency, as manifested by accelerated senescence phenotypes. We uncovered that the role of MAVS in maintaining mitochondrial structural integrity and functional homeostasis depends on its interaction with the guanosine triphosphatase optic atrophy type 1 (OPA1). Depletion of MAVS or OPA1 led to the dysfunction of mitochondria and cellular senescence, whereas replenishment of MAVS or OPA1 in MAVS-knockout hMSCs alleviated mitochondrial defects and premature senescence phenotypes. Taken together, our data underscore an uncanonical role of MAVS in safeguarding mitochondrial homeostasis and antagonizing human stem cell senescence.

Single-cell profiling reveals a potent role of quercetin in promoting hair regeneration

Hair loss affects millions of people at some time in their life, and safe and efficient treatments for hair loss are a significant unmet medical need. We report that topical delivery of quercetin (Que) stimulates resting hair follicles to grow with rapid follicular keratinocyte proliferation and replenishes perifollicular microvasculature in mice. We construct dynamic single-cell transcriptome landscape over the course of hair regrowth and find that Que treatment stimulates the differentiation trajectory in the hair follicles and induces an angiogenic signature in dermal endothelial cells by activating HIF-1α in endothelial cells. Skin administration of a HIF-1α agonist partially recapitulates the pro-angiogenesis and hair-growing effects of Que. Together, these findings provide a molecular understanding for the efficacy of Que in hair regrowth, which underscores the translational potential of targeting the hair follicle niche as a strategy for regenerative medicine, and suggest a route of pharmacological intervention that may promote hair regrowth.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Cellular rejuvenation: molecular mechanisms and potential therapeutic interventions for diseases

The ageing process is a systemic decline from cellular dysfunction to organ degeneration, with more predisposition to deteriorated disorders. Rejuvenation refers to giving aged cells or organisms more youthful characteristics through various techniques, such as cellular reprogramming and epigenetic regulation. The great leaps in cellular rejuvenation prove that ageing is not a one-way street, and many rejuvenative interventions have emerged to delay and even reverse the ageing process. Defining the mechanism by which roadblocks and signaling inputs influence complex ageing programs is essential for understanding and developing rejuvenative strategies. Here, we discuss the intrinsic and extrinsic factors that counteract cell rejuvenation, and the targeted cells and core mechanisms involved in this process. Then, we critically summarize the latest advances in state-of-art strategies of cellular rejuvenation. Various rejuvenation methods also provide insights for treating specific ageing-related diseases, including cellular reprogramming, the removal of senescence cells (SCs) and suppression of senescence-associated secretory phenotype (SASP), metabolic manipulation, stem cells-associated therapy, dietary restriction, immune rejuvenation and heterochronic transplantation, etc. The potential applications of rejuvenation therapy also extend to cancer treatment. Finally, we analyze in detail the therapeutic opportunities and challenges of rejuvenation technology. Deciphering rejuvenation interventions will provide further insights into anti-ageing and ageing-related disease treatment in clinical settings.

A comparative study of metformin and nicotinamide riboside in alleviating tissue aging in rats

Metformin (MET) and nicotinamide riboside (NR) have both been reported to exert geroprotective effects in multiple species. However, the mechanism by which MET and NR regulate the aging program and delay aging in multiple tissues remains unclear. Here, we demonstrated that MET and NR attenuate aging features in human mesenchymal stem cells. Moreover, by systematically investigating the pathophysiological changes in different tissues from aged rats after oral administration of MET and NR, we showed that both MET and NR treatment alleviated various aging-related characteristics in multiple tissues, including inflammation, fibrosis, and protein aggregates. Consistently, MET or NR treatment partially rescued aging-related gene expression changes in aged rats. Collectively, we report that both MET and NR attenuate senescence phenotypes in human stem cells in vitro and in a variety of rodent tissues in vivo, thus providing a valuable resource and foundation for further evaluation of these two compounds against aging.

The landscape of aging

Aging is characterized by a progressive deterioration of physiological integrity, leading to impaired functional ability and ultimately increased susceptibility to death. It is a major risk factor for chronic human diseases, including cardiovascular disease, diabetes, neurological degeneration, and cancer. Therefore, the growing emphasis on "healthy aging" raises a series of important questions in life and social sciences. In recent years, there has been unprecedented progress in aging research, particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes. In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases, we review the descriptive, conceptual, and interventive aspects of the landscape of aging composed of a number of layers at the cellular, tissue, organ, organ system, and organismal levels.

Epigenetic regulation of aging: implications for interventions of aging and diseases

Aging is accompanied by the decline of organismal functions and a series of prominent hallmarks, including genetic and epigenetic alterations. These aging-associated epigenetic changes include DNA methylation, histone modification, chromatin remodeling, non-coding RNA (ncRNA) regulation, and RNA modification, all of which participate in the regulation of the aging process, and hence contribute to aging-related diseases. Therefore, understanding the epigenetic mechanisms in aging will provide new avenues to develop strategies to delay aging. Indeed, aging interventions based on manipulating epigenetic mechanisms have led to the alleviation of aging or the extension of the lifespan in animal models. Small molecule-based therapies and reprogramming strategies that enable epigenetic rejuvenation have been developed for ameliorating or reversing aging-related conditions. In addition, adopting health-promoting activities, such as caloric restriction, exercise, and calibrating circadian rhythm, has been demonstrated to delay aging. Furthermore, various clinical trials for aging intervention are ongoing, providing more evidence of the safety and efficacy of these therapies. Here, we review recent work on the epigenetic regulation of aging and outline the advances in intervention strategies for aging and age-associated diseases. A better understanding of the critical roles of epigenetics in the aging process will lead to more clinical advances in the prevention of human aging and therapy of aging-related diseases.

BMAL1 moonlighting as a gatekeeper for LINE1 repression and cellular senescence in primates

Aging in humans is intricately linked with alterations in circadian rhythms concomitant with physiological decline and stem cell exhaustion. However, whether the circadian machinery directly regulates stem cell aging, especially in primates, remains poorly understood. In this study, we found that deficiency of BMAL1, the only non-redundant circadian clock component, results in an accelerated aging phenotype in both human and cynomolgus monkey mesenchymal progenitor cells (MPCs). Unexpectedly, this phenotype was mainly attributed to a transcription-independent role of BMAL1 in stabilizing heterochromatin and thus preventing activation of the LINE1-cGAS-STING pathway. In senescent primate MPCs, we observed decreased capacity of BMAL1 to bind to LINE1 and synergistic activation of LINE1 expression. Likewise, in the skin and muscle tissues from the BMAL1-deficient cynomolgus monkey, we observed destabilized heterochromatin and aberrant LINE1 transcription. Altogether, these findings uncovered a noncanonical role of BMAL1 in stabilizing heterochromatin to inactivate LINE1 that drives aging in primate cells.

Destabilizing heterochromatin by APOE mediates senescence

Apolipoprotein E (APOE) is a component of lipoprotein particles that function in the homeostasis of cholesterol and other lipids. Although APOE is genetically associated with human longevity and Alzheimer's disease, its mechanistic role in aging is largely unknown. Here, we used human genetic, stress-induced and physiological cellular aging models to explore APOE-driven processes in stem cell homeostasis and aging. We report that in aged human mesenchymal progenitor cells (MPCs), APOE accumulation is a driver for cellular senescence. By contrast, CRISPR-Cas9-mediated deletion of APOE endows human MPCs with resistance to cellular senescence. Mechanistically, we discovered that APOE functions as a destabilizer for heterochromatin. Specifically, increased APOE leads to the degradation of nuclear lamina proteins and a heterochromatin-associated protein KRAB-associated protein 1 via the autophagy-lysosomal pathway, thereby disrupting heterochromatin and causing senescence. Altogether, our findings uncover a role of APOE as an epigenetic mediator of senescence and provide potential targets to ameliorate aging-related diseases.

Cross-species metabolomic analysis identifies uridine as a potent regeneration promoting factor

Regenerative capacity declines throughout evolution and with age. In this study, we asked whether metabolic programs underlying regenerative capability might be conserved across species, and if so, whether such metabolic drivers might be harnessed to promote tissue repair. To this end, we conducted metabolomic analyses in two vertebrate organ regeneration models: the axolotl limb blastema and antler stem cells. To further reveal why young individuals have higher regenerative capacity than the elderly, we also constructed metabolic profiles for primate juvenile and aged tissues, as well as young and aged human stem cells. In joint analyses, we uncovered that active pyrimidine metabolism and fatty acid metabolism correlated with higher regenerative capacity. Furthermore, we identified a set of regeneration-related metabolite effectors conserved across species. One such metabolite is uridine, a pyrimidine nucleoside, which can rejuvenate aged human stem cells and promote regeneration of various tissues in vivo. These observations will open new avenues for metabolic intervention in tissue repair and regeneration.

Gallic acid inhibits neuroinflammation and reduces neonatal hypoxic-ischemic brain damages

Neuroinflammation is a leading cause of secondary neuronal injury in neonatal hypoxic-ischemic encephalopathy (HIE). Regulation of neuroinflammation may be beneficial for treatment of HIE and its secondary complications. Gallic acid (GA) has been shown to have anti-inflammatory and antioxidant effects. In this report we found that oxygen-glucose deprivation and/reoxygenation (OGD/R)-induced cell death, and the generation of excessive reactive oxygen species (ROS) and inflammatory cytokines by microglia were inhibited by GA treatment. Furthermore, GA treatment reduced neuroinflammation and neuronal loss, and alleviated motor and cognitive impairments in rats with hypoxic-ischemic brain damage (HIBD). Together, our results reveal that GA is an effective regulator of neuroinflammation and has potential as a pharmaceutical intervention for HIE therapy.

OUP accepted manuscript

Stem cell therapies, including stem cell transplantation and rejuvenation of stem cells in situ, are promising avenues for tackling a broad range of diseases. Stem cells can both self-renew and differentiate into other cell types, and play a significant role in the regulation of tissue homeostasis and regeneration after cell degeneration or injury. However, stem cell exhaustion or dysfunction increases with age and impedes the normal function of multiple tissues and systems. Thus, stem cell therapies could provide a solution to aging and age-associated diseases. Here, we discuss recent advances in understanding the mechanisms that regulate stem cell regeneration. We also summarize potential strategies for rejuvenating stem cells that leverage intrinsic and extrinsic factors. These approaches may pave the way toward therapeutic interventions aiming at extending both health and life span.