Chronic senolytic treatment alleviates established vasomotor dysfunction in aged or atherosclerotic mice

Role of Zinc and Selenium in Oxidative Stress and Immunosenescence: Implications for Healthy Aging and Longevity

Aging is a complex process that includes gradual and spontaneous biochemical and physiological changes which contributes to a decline in performance and increased susceptibility to diseases. Zn and Se are essential trace elements that play a pivotal role in immune functions and antioxidant defense and, consequently, are claimed to play also a role in successful aging trajectories. Consistently with their nature of essential trace elements, a plethora of data obtained “in vitro” and “in vivo” (in humans and animal models) support the relevance of Zn and Se for both the innate and adoptive immune response. Moreover, Zn and Se are strictly involved in the synthesis and regulation of activity of proteins and enzymes, e.g., metallothioneins (MT) and glutathione peroxidase (GPX), that are necessary for our endogenous antioxidant response. This is clearly important to protect our cells from oxidative damage and to slow the decline of our immune system with aging. Age-related changes affecting tissue levels of Zn and Se may indicate that the risk of Zn and Se deficiency increases with aging. However, it is still unclear which of these changes can be the consequence of a “real deficiency” and which can be part of our physiological compensatory response to the accumulating damage occurring in aging. Furthermore, the upregulation of antioxidant proteins (Zn and Se dependent) may be a manifestation of self-induced oxidative stress. By the way, Zn and Se dependent proteins are modulated not only by nutritional status, but also by well-known hallmarks of aging that play antagonistic functions, such as the deregulated nutrient sensing pathways and cellular senescence. Thus, it is not an easy task to conduct Zn or Se supplementation in elderly and it is emerging consistent that these kind of supplementation requires an individualized approach. Anyway, there is consistent support that supplementation with Zn using doses around 10 mg/day is generally safe in elderly and may even improve part of immune performances in those subjects with a baseline deficiency. Regarding Se supplementation, it may induce both beneficial and detrimental effects on cellular immunity depending on the form of Se, supplemental dose, and delivery matrix. The nutritional association of supplements based on “Zn plus Se” is hypothesized to provide additional benefits, but this will likely need a more complex individualized approach. The improvement of our knowledge around screening and detection of Zn and Se deficiency in aging could lead to substantial benefits in terms of efficacy of nutritional supplements aimed at ameliorate performance and health in aging.

Proceedings of the 2018 Santa Fe Bone Symposium: Advances in the Management of Osteoporosis

The Santa Fe Bone Symposium is an annual meeting devoted to clinical applications of recent advances in skeletal research. The 19th Santa Fe Bone Symposium convened August 3-4, 2018, in Santa Fe, New Mexico, USA. Attendees included physicians of many specialties, fellows in training, advanced practice providers, clinical researchers, and bone density technologists. The format consisted of lectures, case presentations by endocrinology fellows, and panel discussions, with all involving extensive interactive discussions. Topics were diverse, including an evolutionary history of calcium homeostasis, osteoporosis treatment in the very old, optimizing outcomes with orthopedic surgery, microbiome and bone, new strategies for combination and sequential therapy of osteoporosis, exercise as medicine, manifestations of parathyroid hormone excess and deficiency, parathyroid hormone as a therapeutic agent, cell senescence and bone health, and managing patients outside clinical practice guidelines. The National Bone Health Alliance conducted a premeeting on development of fracture liaison services. A workshop was devoted to Bone Health TeleECHO (Bone Health Extension for Community Healthcare Outcomes), a strategy of ongoing medical education for healthcare professions to expand capacity to deliver best practice skeletal healthcare in underserved communities and reduce the osteoporosis treatment gap.

Signal Transduction, Ageing and Disease

Ageing is defined by the loss of functional reserve over time, leading to a decreased tissue homeostasis and increased age-related pathology. The accumulation of damage including DNA damage contributes to driving cell signaling pathways that, in turn, can drive different cell fates, including senescence and apoptosis, as well as mitochondrial dysfunction and inflammation. In addition, the accumulation of cell autonomous damage with time also drives ageing through non-cell autonomous pathways by modulation of signaling pathways. Interestingly, genetic and pharmacologic analysis of factors able to modulate lifespan and healthspan in model organisms and even humans have identified several key signaling pathways including IGF-1, NF-κB, FOXO3, mTOR, Nrf-2 and sirtuins. This review will discuss the roles of several of these key signaling pathways, in particular NF-κB and Nrf2, in modulating ageing and age-related diseases.

Influences of Sex and Estrogen in Arterial and Valvular Calcification

Vascular and cardiac valvular calcification was once considered to be a degenerative and end stage product in aging cardiovascular tissues. Over the past two decades, however, a critical mass of data has shown that cardiovascular calcification can be an active and highly regulated process. While the incidence of calcification in the coronary arteries and cardiac valves is higher in men than in age-matched women, a high index of calcification associates with increased morbidity, and mortality in both sexes. Despite the ubiquitous portending of poor outcomes in both sexes, our understanding of mechanisms of calcification under the dramatically different biological contexts of sex and hormonal milieu remains rudimentary. Understanding how the critical context of these variables inform our understanding of mechanisms of calcification-as well as innovative strategies to target it therapeutically-is essential to advancing the fields of both cardiovascular disease and fundamental mechanisms of aging. This review will explore potential sex and sex-steroid differences in the basic biological pathways associated with vascular and cardiac valvular tissue calcification, and potential strategies of pharmacological therapy to reduce or slow these processes.

Senescent cell clearance by the immune system: Emerging therapeutic opportunities

Senescent cells (SCs) arise from normal cells in multiple organs due to inflammatory, metabolic, DNA damage, or tissue damage signals. SCs are non-proliferating but metabolically active cells that can secrete a range of pro-inflammatory and proteolytic factors as part of the senescence-associated secretory phenotype (SASP). Senescent cell anti-apoptotic pathways (SCAPs) protect SCs from their own pro-apoptotic SASP. SCs can chemo-attract immune cells and are usually cleared by these immune cells. During aging and in multiple chronic diseases, SCs can accumulate in dysfunctional tissues. SCs can impede innate and adaptive immune responses. Whether immune system loss of capacity to clear SCs promotes immune system dysfunction, or conversely whether immune dysfunction permits SC accumulation, are important issues that are not yet fully resolved. SCs may be able to assume distinct states that interact differentially with immune cells, thereby promoting or inhibiting SC clearance, establishing a chronically pro-senescent and pro-inflammatory environment, leading to modulation of the SASP by the immune cells recruited and activated by the SASP. Therapies that enhance immune cell-mediated clearance of SCs could provide a lever for reducing SC burden. Such therapies could include vaccines, small molecule immunomodulators, or other approaches. Senolytics, drugs that selectively eliminate SCs by transiently disabling their SCAPs, may prove to alleviate immune dysfunction in older individuals and thereby accelerate immune-mediated clearance of SCs. The more that can be understood about the interplay between SCs and the immune system, the faster new interventions may be developed to delay, prevent, or treat age-related dysfunction and the multiple senescence-associated chronic diseases and disorders.

Advances and challenges in geroscience research: An update

Aging remains the most pervasive risk factor for a wide range of chronic diseases that afflict modern societies. In the United States alone, incidence of age-related diseases (e.g., cardiovascular disease, stroke, Alzheimer's disease, vascular cognitive impairment and dementia, cancer, hypertension, type-2 diabetes, chronic obstructive pulmonary disease, and osteoarthritis) is on the rise, posing an unsustainable socioeconomic burden even for the most developed countries. Tackling each and every age-related disease alone is proving to be costly and ineffective. The emerging field of geroscience has posed itself as an interdisciplinary approach that aims to understand the relationship between the biology of aging and the pathophysiology of chronic age-related diseases. According to the geroscience concept, aging is the single major risk factor that underlies several age-related chronic diseases, and manipulation of cellular and systemic aging processes can delay the manifestation and/or severity of these age-related chronic pathologies. The goal of this endeavor is to achieve health improvements by preventing/delaying the pathogenesis of several age-related diseases simultaneously in the elderly population by targeting key cellular and molecular processes of aging instead of managing diseases of aging as they arise individually. In this review, we discuss recent advances in the field of geroscience, highlighting their implications for potential future therapeutic targets and the associated scientific challenges and opportunities that lay ahead.

Nrf2 deficiency in aged mice exacerbates cellular senescence promoting cerebrovascular inflammation

Aging-induced pro-inflammatory phenotypic alterations of the cerebral vasculature critically contribute to the pathogenesis of vascular cognitive impairment. Cellular senescence is a fundamental aging process that promotes inflammation; however, its role in cerebrovascular aging remains unexplored. The present study was undertaken to test the hypothesis that advanced aging promotes cellular senescence in the cerebral vasculature. We found that in cerebral arteries of 24-month-old mice, expression of molecular markers of senescence (p16^INK4a, p21) is upregulated as compared to that in young controls. Induction of senescence programs in cerebral arteries is associated by an upregulation of a wide range of inflammatory cytokines and chemokines, which are known to contribute to the senescence-associated secretory phenotype (SASP) in vascular cells. Age-related cerebrovascular senescence and inflammation are associated with neuroinflammation, as shown by the molecular footprint of microglia activation in the hippocampus. Genetic depletion of the pro-survival/anti-aging transcriptional regulator Nrf2 exacerbated age-related induction of senescence markers and inflammatory SASP factors and resulted in a heightened inflammatory status of the hippocampus. In conclusion, our studies provide evidence that aging and Nrf2 dysfunction promote cellular senescence in cerebral vessels, which may potentially cause or exacerbate age-related pathology.

Histopathological and molecular analysis of idiopathic pulmonary fibrosis lungs from patients treated with pirfenidone or nintedanib

AIMS

The objective of this study was to quantify the impact of pirfenidone or nintedanib treatment on lung histopathology and molecular mediators of fibrosis in patients with idiopathic pulmonary fibrosis (IPF).

METHODS AND RESULTS

We collected lung tissue from IPF patients at the time of lung transplantation. Histopathological changes were quantified using a blinded scoring method. Proteins associated with senescence or active TGF-β were quantified in lung tissues by immunoblot and immunostaining. Histopathological quantification showed similar amounts of dense collagen fibrosis, fibroblast foci and alveolar macrophages in untreated or pirfenidone- or nintedanib-treated IPF patients. There was less diffuse alveolar damage and organising pneumonia in pirfenidone-treated IPF patients. Lungs of nintedanib-treated patients had a trend towards less lymphocytic interstitial infiltration. There was no difference in expression of p-SMAD3, p21 or p16 in the lungs of untreated, pirfenidone- or nintedanib-treated IPF patients. Alveolar epithelial cells, but not fibroblast foci, were immunoreactive to p16. Pirfenidone or nintedanib treatment did not inhibit activation of senescence programming in cultured lung epithelial cells mediated by hydrogen peroxide.

CONCLUSION

Pirfenidone and nintedanib do not modulate expression of senescence markers, levels of p-SMAD3 or the amount of fibrosis in IPF lungs. Treated patients have less histopathological evidence of acute lung injury at the time of lung transplantation.

Elimination of p19ARF -expressing cells protects against pulmonary emphysema in mice

Senescent cells accumulate in tissues during aging and are considered to underlie several aging‐associated phenotypes and diseases. We recently reported that the elimination of p19^ARF‐expressing senescent cells from lung tissue restored tissue function and gene expression in middle‐aged (12‐month‐old) mice. The aging of lung tissue increases the risk of pulmonary diseases such as emphysema, and cellular senescence is accelerated in emphysema patients. However, there is currently no direct evidence to show that cellular senescence promotes the pathology of emphysema, and the involvement of senescence in the development of this disease has yet to be clarified. We herein demonstrated that p19^ARF facilitated the development of pulmonary emphysema in mice. The elimination of p19^ARF‐expressing cells prevented lung tissue from elastase‐induced lung dysfunction. These effects appeared to depend on reduced pulmonary inflammation, which is enhanced after elastase stimulation. Furthermore, the administration of a senolytic drug that selectively kills senescent cells attenuated emphysema‐associated pathologies. These results strongly suggest the potential of senescent cells as therapeutic/preventive targets for pulmonary emphysema.

Fisetin is a senotherapeutic that extends health and lifespan

BACKGROUND

Senescence is a tumor suppressor mechanism activated in stressed cells to prevent replication of damaged DNA. Senescent cells have been demonstrated to play a causal role in driving aging and age-related diseases using genetic and pharmacologic approaches. We previously demonstrated that the combination of dasatinib and the flavonoid quercetin is a potent senolytic improving numerous age-related conditions including frailty, osteoporosis and cardiovascular disease. The goal of this study was to identify flavonoids with more potent senolytic activity.

METHODS

A panel of flavonoid polyphenols was screened for senolytic activity using senescent murine and human fibroblasts, driven by oxidative and genotoxic stress, respectively. The top senotherapeutic flavonoid was tested in mice modeling a progeroid syndrome carrying a p16INK4a-luciferase reporter and aged wild-type mice to determine the effects of fisetin on senescence markers, age-related histopathology, disease markers, health span and lifespan. Human adipose tissue explants were used to determine if results translated.

FINDINGS

Of the 10 flavonoids tested, fisetin was the most potent senolytic. Acute or intermittent treatment of progeroid and old mice with fisetin reduced senescence markers in multiple tissues, consistent with a hit-and-run senolytic mechanism. Fisetin reduced senescence in a subset of cells in murine and human adipose tissue, demonstrating cell-type specificity. Administration of fisetin to wild-type mice late in life restored tissue homeostasis, reduced age-related pathology, and extended median and maximum lifespan.

INTERPRETATION

The natural product fisetin has senotherapeutic activity in mice and in human tissues. Late life intervention was sufficient to yield a potent health benefit. These characteristics suggest the feasibility to translation to human clinical studies. FUND: NIH grants P01 AG043376 (PDR, LJN), U19 AG056278 (PDR, LJN, WLL), R24 AG047115 (WLL), R37 AG013925 (JLK), R21 AG047984 (JLK), P30 DK050456 (Adipocyte Subcore, JLK), a Glenn Foundation/American Federation for Aging Research (AFAR) BIG Award (JLK), Glenn/AFAR (LJN, CEB), the Ted Nash Long Life and Noaber Foundations (JLK), the Connor Group (JLK), Robert J. and Theresa W. Ryan (JLK), and a Minnesota Partnership Grant (AMAY-UMN#99)-P004610401-1 (JLK, EAA).

Mechanisms of Dysfunction in the Aging Vasculature and Role in Age-Related Disease

Advancing age promotes cardiovascular disease (CVD), the leading cause of death in the United States and many developed nations. Two major age-related arterial phenotypes, large elastic artery stiffening and endothelial dysfunction, are independent predictors of future CVD diagnosis and likely are responsible for the development of CVD in older adults. Not limited to traditional CVD, these age-related changes in the vasculature also contribute to other age-related diseases that influence mammalian health span and potential life span. This review explores mechanisms that influence age-related large elastic artery stiffening and endothelial dysfunction at the tissue level via inflammation and oxidative stress and at the cellular level via Klotho and energy-sensing pathways (AMPK [AMP-activated protein kinase], SIRT [sirtuins], and mTOR [mammalian target of rapamycin]). We also discuss how long-term calorie restriction-a health span- and life span-extending intervention-can prevent many of these age-related vascular phenotypes through the prevention of deleterious alterations in these mechanisms. Lastly, we discuss emerging novel mechanisms of vascular aging, including senescence and genomic instability within cells of the vasculature. As the population of older adults steadily expands, elucidating the cellular and molecular mechanisms of vascular dysfunction with age is critical to better direct appropriate and measured strategies that use pharmacological and lifestyle interventions to reduce risk of CVD within this population.

The role of senescence, telomere dysfunction and shelterin in vascular aging

In the United States and other westernized nations, CVDs are the leading cause of death in adults over 65 years of age. Large artery stiffness and endothelial dysfunction are increased with age and age-associated arterial dysfunction is an important antecedent of CVDs. One age-associated change that may contribute to vascular dysfunction and CVD risk is an increase in the number of resident senescent cells in the vasculature. Senescent cells display a pro-oxidant, pro-inflammatory phenotype known as the SASP. However, the mechanisms that drive the SASP and the vascular aging phenotype remain elusive. A putative mechanism is the involvement of oxidative stress and inflammation in telomere function. Telomeres are the end caps of chromosomes which are maintained by a six-protein complex known as shelterin. Disruption of shelterin can uncap telomeres and induce cellular senescence. Accordingly, in this review, we propose that oxidative stress and inflammation disrupt shelterin in vascular cells, driving telomere dysfunction and that this mechanism may be responsible for the induction of SASP. The proposed mechanisms may represent some of the initial changes that lead to vascular dysfunction in advanced age.

A versatile drug delivery system targeting senescent cells

Senescent cells accumulate in multiple aging-associated diseases, and eliminating these cells has recently emerged as a promising therapeutic approach. Here, we take advantage of the high lysosomal β-galactosidase activity of senescent cells to design a drug delivery system based on the encapsulation of drugs with galacto-oligosaccharides. We show that gal-encapsulated fluorophores are preferentially released within senescent cells in mice. In a model of chemotherapy-induced senescence, gal-encapsulated cytotoxic drugs target senescent tumor cells and improve tumor xenograft regression in combination with palbociclib. Moreover, in a model of pulmonary fibrosis in mice, gal-encapsulated cytotoxics target senescent cells, reducing collagen deposition and restoring pulmonary function. Finally, gal-encapsulation reduces the toxic side effects of the cytotoxic drugs. Drug delivery into senescent cells opens new diagnostic and therapeutic applications for senescence-associated disorders.

Endothelial dysfunction and angiogenesis impairment in the ageing vasculature

Ageing is the main risk factor for the development of cardiovascular diseases. A central mechanism by which ageing promotes vascular pathologies is compromising endothelial health. The age-related attenuation of endothelium-dependent dilator responses (endothelial dysfunction) associated with impairment of angiogenic processes and the subsequent pathological remodelling of the microcirculation contribute to compromised tissue perfusion and exacerbate functional decline in older individuals. This Review focuses on cellular, molecular, and functional changes that occur in the endothelium during ageing. We explore the links between oxidative and nitrative stress and the conserved molecular pathways affecting endothelial dysfunction and impaired angiogenesis during ageing. We also speculate on how these pathological processes could be therapeutically targeted. An improved understanding of endothelial biology in older patients is crucial for all cardiologists because maintenance of a competently functioning endothelium is critical for adequate tissue perfusion and long-term cardiac health.

The Spectrum of Fundamental Basic Science Discoveries Contributing to Organismal Aging

Aging research has undergone unprecedented advances at an accelerating rate in recent years, leading to excitement in the field as well as opportunities for imagination and innovation. Novel insights indicate that, rather than resulting from a preprogrammed series of events, the aging process is predominantly driven by fundamental non-adaptive mechanisms that are interconnected, linked, and overlap. To varying degrees, these mechanisms also manifest with aging in bone where they cause skeletal fragility. Because these mechanisms of aging can be manipulated, it might be possible to slow, delay, or alleviate multiple age-related diseases and their complications by targeting conserved genetic signaling pathways, controlled functional networks, and basic biochemical processes. Indeed, findings in various mammalian species suggest that targeting fundamental aging mechanisms (eg, via either loss-of-function or gain-of-function mutations or administration of pharmacological therapies) can extend healthspan; ie, the healthy period of life free of chronic diseases. In this review, we summarize the evidence supporting the role of the spectrum of fundamental basic science discoveries contributing to organismal aging, with emphasis on mammalian studies and in particular aging mechanisms in bone that drive skeletal fragility. These mechanisms or aging hallmarks include: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. Because these mechanisms are linked, interventions that ameliorate one hallmark can in theory ameliorate others. In the field of bone and mineral research, current challenges include defining the relative contributions of each aging hallmark to the natural skeletal aging process, better understanding the complex interconnections among the hallmarks, and identifying the most effective therapeutic strategies to safely target multiple hallmarks. Based on their interconnections, it may be feasible to simultaneously interfere with several fundamental aging mechanisms to alleviate a wide spectrum of age-related chronic diseases, including osteoporosis. © 2018 American Society for Bone and Mineral Research.

Cellular Senescence: The Sought or the Unwanted?

Cellular senescence is a process that results in irreversible cell-cycle arrest, and is thought to be an autonomous tumor-suppressor mechanism. During senescence, cells develop distinctive metabolic and signaling features, together referred to as the senescence-associated secretory phenotype (SASP). The SASP is implicated in several aging-related pathologies, including various malignancies. Accumulating evidence argues that cellular senescence acts as a double-edged sword in human cancer, and new agents and innovative strategies to tackle senescent cells are in development pipelines to counter the adverse effects of cellular senescence in the clinic. We focus on recent discoveries in senescence research and SASP biology, and highlight the potential of SASP suppression and senescent cell clearance in advancing precision medicine.

Proinflammatory Arterial Stiffness Syndrome: A Signature of Large Arterial Aging

Age-associated structural and functional remodeling of the arterial wall produces a productive environment for the initiation and progression of hypertension and atherosclerosis. Chronic aging stress induces low-grade proinflammatory signaling and causes cellular proinflammation in arterial walls, which triggers the structural phenotypic shifts characterized by endothelial dysfunction, diffuse intimal-medial thickening, and arterial stiffening. Microscopically, aged arteries exhibit an increase in arterial cell senescence, proliferation, invasion, matrix deposition, elastin fragmentation, calcification, and amyloidosis. These characteristic cellular and matrix alterations not only develop with aging but can also be induced in young animals under experimental proinflammatory stimulation. Interestingly, these changes can also be attenuated in old animals by reducing low-grade inflammatory signaling. Thus, mitigating age-associated proinflammation and arterial phenotype shifts is a potential approach to retard arterial aging and prevent the epidemic of hypertension and atherosclerosis in the elderly.

Senolytics improve physical function and increase lifespan in old age

Physical function declines in old age, portending disability, increased health expenditures, and mortality. Cellular senescence, leading to tissue dysfunction, may contribute to these consequences of aging, but whether senescence can directly drive age-related pathology and be therapeutically targeted is still unclear. Here we demonstrate that transplanting relatively small numbers of senescent cells into young mice is sufficient to cause persistent physical dysfunction, as well as to spread cellular senescence to host tissues. Transplanting even fewer senescent cells had the same effect in older recipients and was accompanied by reduced survival, indicating the potency of senescent cells in shortening health- and lifespan. The senolytic cocktail, dasatinib plus quercetin, which causes selective elimination of senescent cells, decreased the number of naturally occurring senescent cells and their secretion of frailty-related proinflammatory cytokines in explants of human adipose tissue. Moreover, intermittent oral administration of senolytics to both senescent cell-transplanted young mice and naturally aged mice alleviated physical dysfunction and increased post-treatment survival by 36% while reducing mortality hazard to 65%. Our study provides proof-of-concept evidence that senescent cells can cause physical dysfunction and decreased survival even in young mice, while senolytics can enhance remaining health- and lifespan in old mice.

Spontaneous DNA damage to the nuclear genome promotes senescence, redox imbalance and aging

Accumulation of senescent cells over time contributes to aging and age-related diseases. However, what drives senescence in vivo is not clear. Here we used a genetic approach to determine if spontaneous nuclear DNA damage is sufficient to initiate senescence in mammals. Ercc1-/∆ mice with reduced expression of ERCC1-XPF endonuclease have impaired capacity to repair the nuclear genome. Ercc1-/∆ mice accumulated spontaneous, oxidative DNA damage more rapidly than wild-type (WT) mice. As a consequence, senescent cells accumulated more rapidly in Ercc1-/∆ mice compared to repair-competent animals. However, the levels of DNA damage and senescent cells in Ercc1-/∆ mice never exceeded that observed in old WT mice. Surprisingly, levels of reactive oxygen species (ROS) were increased in tissues of Ercc1-/∆ mice to an extent identical to naturally-aged WT mice. Increased enzymatic production of ROS and decreased antioxidants contributed to the elevation in oxidative stress in both Ercc1-/∆ and aged WT mice. Chronic treatment of Ercc1-/∆ mice with the mitochondrial-targeted radical scavenger XJB-5-131 attenuated oxidative DNA damage, senescence and age-related pathology. Our findings indicate that nuclear genotoxic stress arises, at least in part, due to mitochondrial-derived ROS, and this spontaneous DNA damage is sufficient to drive increased levels of ROS, cellular senescence, and the consequent age-related physiological decline.

Premature Physiologic Aging as a Paradigm for Understanding Increased Risk of Adverse Health Across the Lifespan of Survivors of Childhood Cancer

The improvement in survival of childhood cancer observed across the past 50 years has resulted in a growing acknowledgment that simply extending the lifespan of survivors is not enough. It is incumbent on both the cancer research and the clinical care communities to also improve the health span of survivors. It is well established that aging adult survivors of childhood cancer are at increased risk of chronic health conditions, relative to the general population. However, as the first generation of survivors age into their 50s and 60s, it has become increasingly evident that this population is also at risk of early onset of physiologic aging. Geriatric measures have uncovered evidence of reduced strength and speed and increased fatigue, all components of frailty, among survivors with a median age of 33 years, which is similar to adults older than 65 years of age in the general population. Furthermore, frailty in survivors independently increased the risk of morbidity and mortality. Although there has been a paucity of research investigating the underlying biologic mechanisms for advanced physiologic age in survivors, results from geriatric populations suggest five biologically plausible mechanisms that may be potentiated by exposure to cancer therapies: increased cellular senescence, reduced telomere length, epigenetic modifications, somatic mutations, and mitochondrial DNA infidelity. There is now a critical need for research to elucidate the biologic mechanisms of premature aging in survivors of childhood cancer. This research could pave the way for new frontiers in the prevention of these life-changing outcomes.

Local delivery of tetramethylpyrazine eliminates the senescent phenotype of bone marrow mesenchymal stromal cells and creates an anti-inflammatory and angiogenic environment in aging mice

Aging drives the accumulation of senescent cells (SnCs) including stem/progenitor cells in bone marrow, which contributes to aging‐related bone degenerative pathologies. Local elimination of SnCs has been shown as potential treatment for degenerative diseases. As LepR⁺ mesenchymal stem/progenitor cells (MSPCs) in bone marrow are the major population for forming bone/cartilage and maintaining HSCs niche, whether local elimination of senescent LepR⁺MSPCs delays aging‐related pathologies and improves local microenvironment need to be well defined. In this study, we performed local delivery of tetramethylpyrazine (TMP) in bone marrow of aging mice, which previously showed to be used for the prevention and treatment of glucocorticoid‐induced osteoporosis (GIOP). We found the increased accumulation of senescent LepR⁺MSPCs in bone marrow of aging mice, and TMP significantly inhibited the cell senescent phenotype via modulating Ezh2‐H3k27me3. Most importantly, local delivery of TMP improved bone marrow microenvironment and maintained bone homeostasis in aging mice by increasing metabolic and anti‐inflammatory responses, inducing H‐type vessel formation, and maintaining HSCs niche. These findings provide evidence on the mechanisms, characteristics and functions of local elimination of SnCs in bone marrow, as well as the use of TMP as a potential treatment to ameliorate human age‐related skeletal diseases and to promote healthy lifespan.

p16(Ink4a) and senescence-associated β-galactosidase can be induced in macrophages as part of a reversible response to physiological stimuli

Constitutive p16^Ink4a expression, along with senescence-associated β-galactosidase (SAβG), are commonly accepted biomarkers of senescent cells (SCs). Recent reports attributed improvement of the healthspan of aged mice following p16^Ink4a-positive cell killing to the eradication of accumulated SCs. However, detection of p16^Ink4a/SAβG-positive macrophages in the adipose tissue of old mice and in the peritoneal cavity of young animals following injection of alginate-encapsulated SCs has raised concerns about the exclusivity of these markers for SCs. Here we report that expression of p16^Ink4a and SAβG in macrophages is acquired as part of a physiological response to immune stimuli rather than through senescence, consistent with reports that p16^Ink4a plays a role in macrophage polarization and response. Unlike SCs, p16^Ink4a/SAβG-positive macrophages can be induced in p53-null mice. Macrophages, but not mesenchymal SCs, lose both markers in response to M1- [LPS, IFN-α, Poly(I:C)] and increase their expression in response to M2-inducing stimuli (IL-4, IL-13). Moreover, interferon-inducing agent Poly(I:C) dramatically reduced p16^Ink4a expression in vivo in our alginate bead model and in the adipose tissue of aged mice. These observations suggest that the antiaging effects following eradication of p16^Ink4a-positive cells may not be solely attributed to SCs but also to non-senescent p16^Ink4a/SAβG-positive macrophages.

Senescent cells: a therapeutic target for cardiovascular disease

Cellular senescence, a major tumor-suppressive cell fate, has emerged from humble beginnings as an in vitro phenomenon into recognition as a fundamental mechanism of aging. In the process, senescent cells have attracted attention as a therapeutic target for age-related diseases, including cardiovascular disease (CVD), the leading cause of morbidity and mortality in the elderly. Given the aging global population and the inadequacy of current medical management, attenuating the health care burden of CVD would be transformative to clinical practice. Here, we review the evidence that cellular senescence drives CVD in a bimodal fashion by both priming the aged cardiovascular system for disease and driving established disease forward. Hence, the growing field of senotherapy (neutralizing senescent cells for therapeutic benefit) is poised to contribute to both prevention and treatment of CVD.

Strategies targeting cellular senescence

Cellular senescence is a physiological phenomenon that has both beneficial and detrimental consequences. Senescence limits tumorigenesis and tissue damage throughout the lifetime. However, at the late stages of life, senescent cells increasingly accumulate in tissues and might also contribute to the development of various age-related pathologies. Recent studies have revealed the molecular pathways that preserve the viability of senescent cells and the ones regulating their immune surveillance. These studies provide essential initial insights for the development of novel therapeutic strategies for targeting senescent cells. At the same time they stress the need to understand the limitations of the existing strategies, their efficacy and safety, and the possible deleterious consequences of senescent cell elimination. Here we discuss the existing strategies for targeting senescent cells and upcoming challenges in translating these strategies into safe and efficient therapies. Successful translation of these strategies could have implications for treating a variety of diseases at old age and could potentially reshape our view of health management during aging.

Inhibiting Cellular Senescence: A New Therapeutic Paradigm for Age-Related Osteoporosis

Context

With the aging of the population and projected increase in osteoporotic fractures coupled with the declining use of osteoporosis medications, there is a compelling need for new approaches to treat osteoporosis. Given that age-related osteoporosis generally coexists with multiple other comorbidities (e.g., atherosclerosis, diabetes, frailty) that share aging as the leading risk factor, there is growing interest in the "Geroscience Hypothesis," which posits that manipulation of fundamental aging mechanisms will delay the appearance or severity of multiple chronic diseases because these diseases share aging as the underlying risk factor. In this context, one fundamental aging mechanism that has received considerable attention recently as contributing to multiple age-related morbidities is cellular senescence. This mini-review provides an overview on cellular senescence with a focus on its role in mediating age-related bone loss.

Methods

This summary is based on the authors' knowledge of the field supplemented by a PubMed search using the terms "senescence," "aging," and "bone."

Results

There is compelling evidence from preclinical models and supportive human data demonstrating an increase in senescent cells in the bone microenvironment with aging. These cells produce a proinflammatory secretome that leads to increased bone resorption and decreased bone formation, and approaches that either eliminate senescent cells or impair the production of their proinflammatory secretome have been shown to prevent age-related bone loss in mice.

Conclusions

Targeting cellular senescence represents a novel therapeutic strategy to prevent not only bone loss but potentially multiple age-related diseases simultaneously.

Telomere uncapping and vascular aging

Although most telomere biology research continues to focus on telomere shortening, there is increasing evidence that telomere deprotection, or "uncapping," is more biologically and possibly clinically important. Telomeres form t-loops to prevent the chromosome ends from appearing as a double-stranded DNA break and initiating a DNA damage response. Breakdown of the t-loop structure, referred to as uncapping, can lead to cellular senescence, increased oxidative stress, and inflammation in tissues. In this review, we describe how telomere uncapping potentially leads to age-related vascular dysfunction and increased cellular senescence, oxidative stress, and inflammation. Importantly, we present evidence to argue that telomere uncapping is more biologically relevant than telomere shortening and a better marker of vascular aging and target for antiaging interventions.

Vascular Senescence in Cardiovascular and Metabolic Diseases

In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere shortening and reactive oxygen species induce “cellular senescence”, which is characterized by growth arrest and alteration of the gene expression profile. Chronological aging is associated with development of age-related diseases, including heart failure, diabetes, and atherosclerotic disease, and studies have shown that accumulation of senescent cells has a causative role in the pathology of these age-related disorders. Endothelial cell senescence has been reported to develop in heart failure and promotes pathologic changes in the failing heart. Senescent endothelial cells and vascular smooth muscle cells are found in atherosclerotic plaque, and studies indicate that these cells are involved in progression of plaque. Diabetes is also linked to accumulation of senescent vascular endothelial cells, while endothelial cell senescence per se induces systemic glucose intolerance by inhibiting skeletal muscle metabolism. A close connection between derangement of systemic metabolism and cellular senescence is also well recognized. Aging is a complex phenomenon, and there is no simple approach to understanding the whole process. However, there is accumulating evidence that cellular senescence has a central role in the development and progression of various undesirable aspects of aging. Suppression of cellular senescence or elimination of senescent cells reverses phenotypic changes of aging in several models, and proof-of-concept has been established that inhibiting accumulation of senescent cells could become a next generation therapy for age-related disorders. It is clear that cellular senescence drives various pathological changes associated with aging. Accordingly, further investigation into the role of this biological process in age-related disorders and discovery of senolytic compounds are important fields for future exploration.

The senescent bystander effect is caused by ROS-activated NF-κB signalling

Cell senescence is an important driver of the ageing process. The accumulation of senescent cells in tissues is accelerated by stress signals from senescent cells that induce DNA damage and ultimately senescence in bystander cells. We examine here the interplay of senescence-associated mitochondrial dysfunction (SAMD)-driven production of reactive oxygen species (ROS) and senescence-associated secretory phenotype (SASP) in causing the bystander effect. We show that in various modes of fibroblast senescence ROS are necessary and sufficient to activate the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), which facilitates a large part of the SASP. This ROS-NF-κB axis causes the DNA damage response in bystander cells. Cytokines IL-6 and IL-8 are major components of the pro-inflammatory SASP in senescent fibroblasts. However, their activation in senescence is only partially controlled by NF-κB, and they are thus not strong candidates as intercellular mediators of the bystander effect as mediated by the ROS-NF-κB axis.

Source of Chronic Inflammation in Aging

Aging is a complex process that results from a combination of environmental, genetic, and epigenetic factors. A chronic pro-inflammatory status is a pervasive feature of aging. This chronic low-grade inflammation occurring in the absence of overt infection has been defined as “inflammaging” and represents a significant risk factor for morbidity and mortality in the elderly. The low-grade inflammation persists even after reversing pro-inflammatory stimuli such as LDL cholesterol and the renin–angiotensin system (RAS). Recently, several possible sources of chronic low-grade inflammation observed during aging and age-related diseases have been proposed. Cell senescence and dysregulation of innate immunity is one such mechanism by which persistent prolonged inflammation occurs even after the initial stimulus has been removed. Additionally, the coagulation factor that activates inflammatory signaling beyond its role in the coagulation system has been identified. This signal could be a new source of chronic inflammation and cell senescence. Here, we summarized the factors and cellular pathways/processes that are known to regulate low-grade persistent inflammation in aging and age-related disease.

Cellular senescence as a therapeutic target to improve renal transplantation outcome

Kidney transplants from aged donors are more vulnerable to ischemic injury, suffer more from delayed graft function and have a lower graft survival compared to kidneys from younger donors. On a cellular level, aging results in an increase in cells that are in a permanent cell cycle arrest, termed senescence, which secrete a range of pro-inflammatory cytokines and growth factors. Consequently, these senescent cells negatively influence the local milieu by causing inflammaging, and by reducing the regenerative capacity of the kidney. Moreover, the oxidative damage that is inflicted by ischemia-reperfusion injury during transplantation can induce senescence and accelerate aging. In this review, we describe recent developments in the understanding of the biology of aging that have led to the development of a new class of therapeutic agents aimed at eliminating senescent cells. These compounds have already shown to be able to restore tissue homeostasis in old mice, improve kidney function and general health- and lifespan. Use of these anti-senescence compounds holds great promise to improve the quality of marginal donor kidneys as well as to remove senescent cells induced by ischemia-reperfusion injury. Altogether, senescent cell removal may increase the donor pool, relieving the growing organ shortage and improve long-term transplantation outcome.

Inducers of Senescence, Toxic Compounds, and Senolytics: The Multiple Faces of Nrf2-Activating Phytochemicals in Cancer Adjuvant Therapy

The reactivation of senescence in cancer and the subsequent clearance of senescent cells are suggested as therapeutic intervention in the eradication of cancer. Several natural compounds that activate Nrf2 (nuclear factor erythroid-derived 2-related factor 2) pathway, which is involved in complex cytoprotective responses, have been paradoxically shown to induce cell death or senescence in cancer. Promoting the cytoprotective Nrf2 pathway may be desirable for chemoprevention, but it might be detrimental in later stages and advanced cancers. However, senolytic activity shown by some Nrf2-activating compounds could be used to target senescent cancer cells (particularly in aged immune-depressed organisms) that escape immunosurveillance. We herein describe in vitro and in vivo effects of fifteen Nrf2-interacting natural compounds (tocotrienols, curcumin, epigallocatechin gallate, quercetin, genistein, resveratrol, silybin, phenethyl isothiocyanate, sulforaphane, triptolide, allicin, berberine, piperlongumine, fisetin, and phloretin) on cellular senescence and discuss their use in adjuvant cancer therapy. In light of available literature, it can be concluded that the meaning and the potential of adjuvant therapy with natural compounds in humans remain unclear, also taking into account the existence of few clinical trials mostly characterized by uncertain results. Further studies are needed to investigate the therapeutic potential of those compounds that display senolytic activity.

Young plasma reverses age-dependent alterations in hepatic function through the restoration of autophagy

Recent studies showing the therapeutic effect of young blood on aging‐associated deterioration of organs point to young blood as the solution for clinical problems related to old age. Given that defective autophagy has been implicated in aging and aging‐associated organ injuries, this study was designed to determine the effect of young blood on aging‐induced alterations in hepatic function and underlying mechanisms, with a focus on autophagy. Aged rats (22 months) were treated with pooled plasma (1 ml, intravenously) collected from young (3 months) or aged rats three times per week for 4 weeks, and 3‐methyladenine or wortmannin was used to inhibit young blood‐induced autophagy. Aging was associated with elevated levels of alanine transaminase and aspartate aminotransferase, lipofuscin accumulation, steatosis, fibrosis, and defective liver regeneration after partial hepatectomy, which were significantly attenuated by young plasma injections. Young plasma could also restore aging‐impaired autophagy activity. Inhibition of the young plasma‐restored autophagic activity abrogated the beneficial effect of young plasma against hepatic injury with aging. In vitro, young serum could protect old hepatocytes from senescence, and the antisenescence effect of young serum was abrogated by 3‐methyladenine, wortmannin, or small interfering RNA to autophagy‐related protein 7. Collectively, our data indicate that young plasma could ameliorate age‐dependent alterations in hepatic function partially via the restoration of autophagy.

Targeting Senescent Cells in Fibrosis: Pathology, Paradox, and Practical Considerations

PURPOSE OF THE REVIEW

Senescent cells have the capacity to both effect and limit fibrosis. Senotherapeutics target senescent cells to improve aging conditions. Here, we review the contexts in which senescent cells mediate wound healing and fibrotic pathology and the potential utility of senotherapeutic drugs for treatment of fibrotic disease.

RECENT FINDINGS

Multi-action and temporal considerations influence deleterious versus beneficial actions of senescent cells. Acutely generated senescent cells can limit proliferation, and the senescence-associated secretory phenotype (SASP) contains factors that can facilitate tissue repair. Long-lived senescent cells that evade clearance or are generated outside of programmed remodeling can deplete the progenitor pool to exhaust regenerative capacity and through the SASP, stimulate continual activation, leading to disorganized tissue architecture, fibrotic damage, sterile inflammation, and induction of bystander senescence. Senescent cells contribute to fibrotic pathogenesis in multiple tissues, including the liver, kidney, and lung. Senotherapeutics may be a viable strategy for treatment of a range of fibrotic conditions.

c-Myb and C/EBPβ regulate OPN and other senescence-associated secretory phenotype factors

Tumorigenesis results from the convergence of cell autonomous mutations and corresponding stromal changes that promote tumor cell growth. Senescent cells, which secrete a plethora of pro-tumorigenic factors termed the senescence-associated secretory phenotype (SASP), play an important role in tumor formation. Investigation into SASP regulation revealed that many but not all SASP factors are subject to NF-kB and p38MAPK regulation. However, many pro-tumorigenic SASP factors, including osteopontin (OPN), are not responsive to these canonical pathways leaving the regulation of these factors an open question. We report that the transcription factor c-Myb regulates OPN, IL-6, and IL-8 in addition to 57 other SASP factors. The regulation of OPN is direct as c-Myb binds to the OPN promoter in response to senescence. Further, OPN is also regulated by the known SASP regulator C/EBPβ. In response to senescence, the full-length activating C/EBPβ isoform LAP2 increases binding to the OPN, IL-6, and IL-8 promoters. The importance of both c-Myb and C/EBPβ is underscored by our finding that the depletion of either factor reduces the ability of senescent fibroblasts to promote the growth of preneoplastic epithelial cells.

The role of cellular senescence in aging through the prism of Koch-like criteria

Since Hayflick's discovery of cellular senescence (CS), a great volume of knowledge in the field has been accumulated and intensively discussed. Here, we attempted to organize the evidence "for" and "against" the hypothesized causal role of CS in aging. For that purpose, we utilized robust Koch-like logical criteria, based on the assumption that some quantitative relationships between the accumulation of senescent cells and aging rate should exist. If so, it could be expected that (i) the "CS load" would be greater in the premature aging phenotype and lesser in longevity phenotype; (ii) CS would promote age-related diseases, and (iii) the interventions that modulate the levels of senescent cells should also modulate health/lifespan. The analysis shows that CS can be considered a causal factor of aging and an important player in various age-related diseases, though its contribution may greatly vary across species. While the relative impact of senescent cells to aging could overall be rather limited and their elimination is hardly expected to be the "fountain of youth", the potential benefits of the senolytic strategy seems a promising option in combating age-related diseases and extending healthspan.

Extracellular vesicles and aging

Aging and the chronic diseases associated with aging place a tremendous burden on our healthcare system. As our world population ages dramatically over the next decades, this will only increase. Hence, there is a great need to discover fundamental mechanisms of aging to enable development of strategies for minimizing the impact of aging on our health and economy. There is general agreement that cell autonomous mechanisms contribute to aging. As cells accrue damage over time, they respond to it by triggering individual cell fate decisions that ultimately disrupt tissue homeostasis and thus increase risk of morbidity. However, there are numerous lines of evidence, including heterochronic parabiosis and plasma transfer, indicating that cell non-autonomous mechanisms are critically important for aging as well. In addition, senescent cells, which accumulate in tissues with age, can display a senescence-associated secretory phenotype (SASP) that contributes to driving aging and loss of tissue homeostasis through a non-cell autonomous mechanism(s). Given the diverse roles of blood-borne extracellular vesicles (EVs) in modulating not only the immune response, but also angiogenesis and tissue regeneration, they likely play a key role in modulating the aging process through cell non-autonomous mechanisms. The fact that senescent cells release more EVs and with a different composition suggests they contribute to the adverse effects of senescence on aging. In addition, the ability of EVs from functional progenitor cells to promote tissue regeneration suggests that stem cell-derived EVs could be used therapeutically to extend healthspan. This review focuses on the potential roles of EVs in aging, the potential of EV-based therapeutic applications for extending healthspan and the potential for use of circulating EVs as biomarkers of unhealthy aging.

Hallmarks of progeroid syndromes: lessons from mice and reprogrammed cells

Ageing is a process that inevitably affects most living organisms and involves the accumulation of macromolecular damage, genomic instability and loss of heterochromatin. Together, these alterations lead to a decline in stem cell function and to a reduced capability to regenerate tissue. In recent years, several genetic pathways and biochemical mechanisms that contribute to physiological ageing have been described, but further research is needed to better characterize this complex biological process. Because premature ageing (progeroid) syndromes, including progeria, mimic many of the characteristics of human ageing, research into these conditions has proven to be very useful not only to identify the underlying causal mechanisms and identify treatments for these pathologies, but also for the study of physiological ageing. In this Review, we summarize the main cellular and animal models used in progeria research, with an emphasis on patient-derived induced pluripotent stem cell models, and define a series of molecular and cellular hallmarks that characterize progeroid syndromes and parallel physiological ageing. Finally, we describe the therapeutic strategies being investigated for the treatment of progeroid syndromes, and their main limitations.

Summary: This Review defines the molecular and cellular hallmarks of progeroid syndromes according to the main cellular and animal models, and discusses the therapeutic strategies developed to date.

Aging of mice is associated with p16(Ink4a)- and β-galactosidase-positive macrophage accumulation that can be induced in young mice by senescent cells

Senescent cells (SCs) have been considered a source of age-related chronic sterile systemic inflammation and a target for anti-aging therapies. To understand mechanisms controlling the amount of SCs, we analyzed the phenomenon of rapid clearance of human senescent fibroblasts implanted into SCID mice, which can be overcome when SCs were embedded into alginate beads preventing them from immunocyte attack. To identify putative SC killers, we analyzed the content of cell populations in lavage and capsules formed around the SC-containing beads. One of the major cell types attracted by secretory factors of SCs was a subpopulation of macrophages characterized by p16(Ink4a) gene expression and β-galactosidase activity at pH6.0 (β-gal(pH6)), thus resembling SCs. Consistently, mice with p16(Ink4a) promoter-driven luciferase, developed bright luminescence of their peritoneal cavity within two weeks following implantation of SCs embedded in alginate beads. p16(Ink4a)/β-gal(pH6)-expressing cells had surface biomarkers of macrophages F4/80 and were sensitive to liposomal clodronate used for the selective killing of cells capable of phagocytosis. At the same time, clodronate failed to kill bona fide SCs generated in vitro by genotoxic stress. Old mice with elevated proportion of p16(Ink4a)/β-gal(pH6)-positive cells in their tissues demonstrated reduction of both following systemic clodronate treatment, indicating that a significant proportion of cells previously considered to be SCs are actually a subclass of macrophages. These observations point at a significant role of p16(Ink4a)/β-gal(pH6)-positive macrophages in aging, which previously was attributed solely to SCs. They require re-interpretation of the mechanisms underlying rejuvenating effects following eradication of p16(Ink4a)/β-gal(pH6)-positive cells and reconsideration of potential cellular target for anti-aging treatment.

New agents that target senescent cells: the flavone, fisetin, and the BCL-XL inhibitors, A1331852 and A1155463

Senescent cells accumulate with aging and at sites of pathology in multiple chronic diseases. Senolytics are drugs that selectively promote apoptosis of senescent cells by temporarily disabling the pro-survival pathways that enable senescent cells to resist the pro-apoptotic, pro-inflammatory factors that they themselves secrete. Reducing senescent cell burden by genetic approaches or by administering senolytics delays or alleviates multiple age- and disease-related adverse phenotypes in preclinical models. Reported senolytics include dasatinib, quercetin, navitoclax (ABT263), and piperlongumine. Here we report that fisetin, a naturally-occurring flavone with low toxicity, and A1331852 and A1155463, selective BCL-X_L inhibitors that may have less hematological toxicity than the less specific BCL-2 family inhibitor navitoclax, are senolytic. Fisetin selectively induces apoptosis in senescent but not proliferating human umbilical vein endothelial cells (HUVECs). It is not senolytic in senescent IMR90 cells, a human lung fibroblast strain, or primary human preadipocytes. A1331852 and A1155463 are senolytic in HUVECs and IMR90 cells, but not preadipocytes. These agents may be better candidates for eventual translation into clinical interventions than some existing senolytics, such as navitoclax, which is associated with hematological toxicity.

Cellular senescence: Implications for metabolic disease

The growing burden of obesity- and aging-related diseases has hastened the search for governing biological processes. Cellular senescence is a stress-induced state of stable growth arrest strongly associated with aging that is aberrantly activated by obesity. The transition of a cell to a senescent state is demarcated by an array of phenotypic markers, and leveraging their context-dependent presentation is essential for determining the influence of senescent cells on tissue pathogenesis. Biomarkers of senescent cells have been identified in tissues that contribute to metabolic disease, including fat, liver, skeletal muscle, pancreata, and cardiovascular tissue, suggesting that pharmacological and behavioral interventions that alter their abundance and/or behavior may be a novel therapeutic strategy. However, contradictory findings with regard to a protective versus deleterious role of senescent cells in certain contexts emphasize the need for additional studies to uncover the complex interplay that defines multi-organ disease processes associated with obesity and aging.

Extracellular matrix alterations in senescent cells and their significance in tissue homeostasis

Normal cells after a defined number of successive divisions or after exposure to genotoxic stresses are becoming senescent, characterized by a permanent growth arrest. In addition, they secrete increased levels of pro-inflammatory and catabolic mediators, collectively termed "senescence-associated secretory phenotype". Furthermore, senescent cells exhibit an altered expression and organization of many extracellular matrix components, leading to specific remodeling of their microenvironment. In this review we present the current knowledge on extracellular matrix alterations associated with cellular senescence and critically discuss certain characteristic examples, highlighting the ambiguous role of senescent cells in the homeostasis of various tissues under both normal and pathologic conditions.

Mechanisms driving the ageing heart

Cardiovascular disease (CVD) is the leading cause of death globally. One of the main risk factors for CVD is age, however the biological processes that occur in the heart during ageing are poorly understood. It is therefore important to understand the fundamental mechanisms driving heart ageing to enable the development of preventions and treatments targeting these processes. Cellular senescence is often described as the irreversible cell-cycle arrest which occurs in somatic cells. Emerging evidence suggests that cellular senescence plays a key role in heart ageing, however the cell-types involved and the underlying mechanisms are not yet elucidated. In this review we discuss the current understanding of how mechanisms known to contribute to senescence impact on heart ageing and CVD. Finally, we evaluate recent data suggesting that targeting senescent cells may be a viable therapy to counteract the ageing of the heart.