Progeria syndromes and ageing: what is the connection?

Identification of the cytoplasmic DNA-Sensing cGAS-STING pathway-mediated gene signatures and molecular subtypes in prostate cancer

BACKGROUND

Considering the age relevance of prostate cancer (PCa) and the involvement of the cGAS-STING pathway in aging and cancer, we aim to classify PCa into distinct molecular subtypes and identify key genes from the novel perspective of the cGAS-STING pathway. It is of significance to guide personalized intervention of cancer-targeting therapy based on genetic evidence.

METHODS

The 430 patients with PCa from the TCGA database were included. We integrated 29 key genes involved in cGAS-STING pathway and analyzed differentially expressed genes and biochemical recurrence (BCR)-free survival-related genes. The assessments of tumor stemness and heterogeneity and tumor microenvironment (TME) were conducted to reveal potential mechanisms.

RESULTS

PCa patients were classified into two distinct subtypes using AURKB, TREX1, and STAT6, and subtype 1 had a worse prognosis than subtype 2 (HR: 21.19, p < 0.001). The findings were validated in the MSKCC2010 cohort. Among subtype 1 and subtype 2, the top ten mutation genes were MUC5B, DNAH9, SLC5A10, ZNF462, USP31, SIPA1L3, PLEC, HRAS, MYOM1, and ITGB6. Gene set variation analysis revealed a high enrichment of the E2F target in subtype 1, and gene set enrichment analysis showed significant enrichment of base excision repair, cell cycle, and DNA replication in subtype 1. TME evaluation indicated that subtype 1 had a significantly higher level of T cells follicular helper and a lower level of plasma cells than subtype 2.

CONCLUSIONS

The molecular subtypes mediated by the cGAS-STING pathway and the genetic risk score may aid in identifying potentially high-risk PCa patients who may benefit from pharmacologic therapies targeting the cGAS-STING pathway.

Role and Potential Mechanisms of Nicotinamide Mononucleotide in Aging

Nicotinamide adenine dinucleotide (NAD+) has recently attracted much attention due to its role in aging and lifespan extension. NAD+ directly and indirectly affects many cellular processes, including metabolic pathways, DNA repair, and immune cell activities. These mechanisms are critical for maintaining cellular homeostasis. However, the decline in NAD+ levels with aging impairs tissue function, which has been associated with several age-related diseases. In fact, the aging population has been steadily increasing worldwide, and it is important to restore NAD+ levels and reverse or delay these age-related disorders. Therefore, there is an increasing demand for healthy products that can mitigate aging, extend lifespan, and halt age-related consequences. In this case, several studies in humans and animals have targeted NAD+ metabolism with NAD+ intermediates. Among them, nicotinamide mononucleotide (NMN), a precursor in the biosynthesis of NAD+, has recently received much attention from the scientific community for its anti-aging properties. In model organisms, ingestion of NMN has been shown to improve age-related diseases and probably delay death. Here, we review aspects of NMN biosynthesis and the mechanism of its absorption, as well as potential anti-aging mechanisms of NMN, including recent preclinical and clinical tests, adverse effects, limitations, and perceived challenges.

Insights into targeting cellular senescence with senolytic therapy: The journey from preclinical trials to clinical practice

Interconnected, fundamental aging processes are central to many illnesses and diseases. Cellular senescence is a mechanism that halts the cell cycle in response to harmful stimuli. Senescent cells (SnCs) can emerge at any point in life, and their persistence, along with the numerous proteins they secrete, can negatively affect tissue function. Interventions aimed at combating persistent SnCs, which can destroy tissues, have been used in preclinical models to delay, halt, or even reverse various diseases. Consequently, the development of small-molecule senolytic medicines designed to specifically eliminate SnCs has opened potential avenues for the prevention or treatment of multiple diseases and age-related issues in humans. In this review, we explore the most promising approaches for translating small-molecule senolytics and other interventions targeting senescence in clinical practice. This discussion highlights the rationale for considering SnCs as therapeutic targets for diseases affecting individuals of all ages.

Biomimetic Therapeutics for Bone Regeneration: A Perspective on Antiaging Strategies

Advances in modern medicine and the significant reduction in infant mortality have steadily increased the population's lifespan. As more and more people in the world grow older, incidence of chronic, noncommunicable disease is anticipated to drastically increase. Recent studies have shown that improving the health of the aging population is anticipated to provide the most cost-effective and impactful improvement in quality of life during aging-driven disease. In bone, aging is tightly linked to increased risk of fracture, and markedly decreased regenerative potential, deeming it critical to develop therapeutics to improve aging-driven bone regeneration. Biomimetics offer a cost-effective method in regenerative therapeutics for bone, where there are numerous innovations improving outcomes in young models, but adapting biomimetics to aged models is still a challenge. Chronic inflammation, accumulation of reactive oxygen species, and cellular senescence are among three of the more unique challenges facing aging-induced defect repair. This review dissects many of the innovative biomimetic approaches research groups have taken to tackle these challenges, and discusses the further uncertainties that need to be addressed to push the field further. Through these research innovations, it can be noted that biomimetic therapeutics hold great potential for the future of aging-complicated defect repair.

Sex-specific preservation of neuromuscular function and metabolism following systemic transplantation of multipotent adult stem cells in a murine model of progeria

Onset and rates of sarcopenia, a disease characterized by a loss of muscle mass and function with age, vary greatly between sexes. Currently, no clinical interventions successfully arrest age-related muscle impairments since the decline is frequently multifactorial. Previously, we found that systemic transplantation of our unique adult multipotent muscle-derived stem/progenitor cells (MDSPCs) isolated from young mice-but not old-extends the health-span in DNA damage mouse models of progeria, a disease of accelerated aging. Additionally, induced neovascularization in the muscles and brain-where no transplanted cells were detected-strongly suggests a systemic therapeutic mechanism, possibly activated through circulating secreted factors. Herein, we used ZMPSTE24-deficient mice, a lamin A defect progeria model, to investigate the ability of young MDSPCs to preserve neuromuscular tissue structure and function. We show that progeroid ZMPST24-deficient mice faithfully exhibit sarcopenia and age-related metabolic dysfunction. However, systemic transplantation of young MDSPCs into ZMPSTE24-deficient progeroid mice sustained healthy function and histopathology of muscular tissues throughout their 6-month life span in a sex-specific manner. Indeed, female-but not male-mice systemically transplanted with young MDSPCs demonstrated significant preservation of muscle endurance, muscle fiber size, mitochondrial respirometry, and neuromuscular junction morphometrics. These novel findings strongly suggest that young MDSPCs modulate the systemic environment of aged animals by secreted rejuvenating factors to maintain a healthy homeostasis in a sex-specific manner and that the female muscle microenvironment remains responsive to exogenous regenerative cues in older age. This work highlights the age- and sex-related differences in neuromuscular tissue degeneration and the future prospect of preserving health in older adults with systemic regenerative treatments.

Senescent cells at the crossroads of aging, disease, and tissue homeostasis

Originally identified as an outcome of continuous culture of primary cells, cellular senescence has moved beyond the culture dish and is now a bona fide driver of aging and disease in animal models, and growing links to human disease. This cellular stress response consists of a stable proliferative arrest coupled to multiple phenotypic changes. Perhaps the most important of these is the senescence-associated secretory phenotype, or senescence-associated secretory phenotype -a complex and variable collection of secreted molecules release by senescent cells with a number of potent biological activities. Senescent cells appear in multiple age-associated conditions in humans and mice, and interventions that eliminate these cells can prevent or even reverse multiple diseases in mouse models. Here, we review salient aspects of senescent cells in the context of human disease and homeostasis. Senescent cells increase in abundance during several diseases that associated with premature aging. Conversely, senescent cells have a key role in beneficial processes such as development and wound healing, and thus can help maintain tissue homeostasis. Finally, we speculate on mechanisms by which deleterious aspects of senescent cells might be targeted while retaining homeostatic aspects in order to improve age-related outcomes.

A Review on the Efficacy of Plant-derived Bio-active Compounds Curcumin and Aged Garlic Extract in Modulating Cancer and Age-related Diseases

Aging is a process characterized by accumulating degenerative changes resulting in the death of an organism. Aging is mediated by various pathways that are directly linked to the individual's lifespan and are shunted for many age-related diseases. Many strategies for alleviating age-related diseases have been studied, which can target cells and molecules. Modern drugs such as Metformin, Rapamycin, and other drugs are used to reduce the effects of age-related diseases. Despite their beneficial activity, they possess some side effects which can limit their applications, mainly in older adults. Natural phytochemicals which have anti-aging activities have been studied by many researchers from a broader aspect and suggested that plant-based compounds can be a possible, direct, and practical way to treat age-related diseases which has enormous anti-aging activity. Also, studies indicated that the synergistic action of phytochemicals might enhance the biological effect rather than the individual or summative effects of natural compounds. Curcumin has an antioxidant property and is an effective scavenger of reactive oxygen species. Curcumin also has a beneficial role in many age-related diseases like diabetes, cardiovascular disease, neurological disorder, and cancer. Aged garlic extracts are also another bioactive component that has high antioxidant properties. Many studies demonstrated aged garlic extract, which has high antioxidant properties, could play a significant role in anti-aging and age-related diseases. The synergistic effect of these compounds can decrease the requirement of doses of a single drug, thus reducing its side effects caused by increased concentration of the single drug.

Repurposing nucleoside reverse transcriptase inhibitors (NRTIs) to slow aging

Repurposing drugs already approved in the clinic to be used off-label as geroprotectors, compounds that combat mechanisms of aging, are a promising way to rapidly reduce age-related disease incidence in society. Several recent studies have found that a class of drugs-nucleoside reverse transcriptase inhibitors (NRTIs)-originally developed as treatments for cancers and human immunodeficiency virus (HIV) infection, could be repurposed to slow the aging process. Interestingly, these studies propose complementary mechanisms that target multiple hallmarks of aging. At the molecular level, NRTIs repress LINE-1 elements, reducing DNA damage, benefiting the hallmark of aging of 'Genomic Instability'. At the organellar level, NRTIs inhibit mitochondrial translation, activate ATF-4, suppress cytosolic translation, and extend lifespan in worms in a manner related to the 'Loss of Proteostasis' hallmark of aging. Meanwhile, at the cellular level, NRTIs inhibit the P2X7-mediated activation of the inflammasome, reducing inflammation and improving the hallmark of aging of 'Altered Intercellular Communication'. Future development of NRTIs for human aging health will need to balance out toxic side effects with the beneficial effects, which may occur in part through hormesis.

Identifying novel age-modulating compounds and quantifying cellular aging using novel computational framework for evaluating transcriptional age

The differentiation of human pluripotent stem cells (hPSCs) provides access to most cell types and tissues. However, hPSC-derived lineages capture a fetal-stage of development and methods to accelerate progression to an aged identity are limited. Understanding the factors driving cellular age and rejuvenation is also essential for efforts aimed at extending human life and health span. A prerequisite for such studies is the development of methods to score cellular age and simple readouts to assess the relative impact of various age modifying strategies. Here we established a transcriptional score (RNAge) in young versus old primary fibroblasts, frontal cortex and substantia nigra tissue. We validated the score in independent RNA-seq datasets and demonstrated a strong cell and tissue specificity. In fibroblasts we observed a reset of RNAge during iPSC reprogramming while direct reprogramming of aged fibroblasts to induced neurons (iN) resulted in the maintenance of both a neuronal and a fibroblast aging signature. Increased RNAge in hPSC-derived neurons was confirmed for several age-inducing strategies such as SATB1 loss, progerin expression or chemical induction of senescence (SLO). Using RNAge as a probe set, we next performed an in-silico screen using the LINCS L1000 dataset. We identified and validated several novel age-inducing and rejuvenating compounds, and we observed that RNAage captures age-related changes associated with distinct cellular hallmarks of age. Our study presents a simple tool to score age manipulations and identifies compounds that greatly expand the toolset of age-modifying strategies in hPSC derived lineages.

Epigenomic signature of accelerated ageing in progeroid Cockayne syndrome

Cockayne syndrome (CS) and UV-sensitive syndrome (UVSS) are rare genetic disorders caused by mutation of the DNA repair and multifunctional CSA or CSB protein, but only CS patients display a progeroid and neurodegenerative phenotype, providing a unique conceptual and experimental paradigm. As DNA methylation (DNAm) remodelling is a major ageing marker, we performed genome-wide analysis of DNAm of fibroblasts from healthy, UVSS and CS individuals. Differential analysis highlighted a CS-specific epigenomic signature (progeroid-related; not present in UVSS) enriched in three categories: developmental transcription factors, ion/neurotransmitter membrane transporters and synaptic neuro-developmental genes. A large fraction of CS-specific DNAm changes were associated with expression changes in CS samples, including in previously reported post-mortem cerebella. The progeroid phenotype of CS was further supported by epigenomic hallmarks of ageing: the prediction of DNAm of repetitive elements suggested an hypomethylation of Alu sequences in CS, and the epigenetic clock returned a marked increase in CS biological age respect to healthy and UVSS cells. The epigenomic remodelling of accelerated ageing in CS displayed both commonalities and differences with other progeroid diseases and regular ageing. CS shared DNAm changes with normal ageing more than other progeroid diseases do, and included genes functionally validated for regular ageing. Collectively, our results support the existence of an epigenomic basis of accelerated ageing in CS and unveil new genes and pathways that are potentially associated with the progeroid/degenerative phenotype.

[Progeroid syndromes : Aging, skin aging, and mechanisms of progeroid syndromes]

Progeroid syndromes (PSs) are characterized by the premature onset of age-related pathologies. PSs display a wide range of heterogeneous pathological symptoms that also manifest during natural aging, including vision and hearing loss, atrophy, hair loss, progressive neurodegeneration, and cardiovascular defects. Recent advances in molecular pathology have led to a better understanding of the underlying mechanisms of these diseases. The genetic mutations underlying PSs are functionally linked to genome maintenance and repair, supporting the causative role of DNA damage accumulation in aging. While some of those genes encode proteins with a direct involvement in a DNA repair machinery, such as nucleotide excision repair (NER), others destabilize the genome by compromising the stability of the nuclear envelope, when lamin A is dysfunctional in Hutchinson-Gilford progeria syndrome (HGPS) or regulate the DNA damage response (DDR) such as the ataxia telangiectasia-mutated (ATM) gene. Understanding the molecular pathology of progeroid diseases is crucial in developing potential treatments to manage and prevent the onset of symptoms. This knowledge provides insight into the underlying mechanisms of premature aging and could lead to improved quality of life for individuals affected by progeroid diseases.

BTG2 acts as an inducer of muscle stem cell senescence

BACKGROUND

Muscle aging is associated with muscle stem cell (MuSC) senescence, a process of whose DNA damage accumulation is considered as one of the leading causes. BTG2 had been identified as a mediator of genotoxic and cellular stress signaling pathways, however, its role in senescence of stem cells, including MuSC, remains unknown.

METHOD

We first compared MuSCs isolated from young and old mice to evaluate our in vitro model of natural senescence. CCK8 and EdU assays were utilized to assess the proliferation capacity of the MuSCs. Cellular senescence was further assessed at biochemical levels by SA-β-Gal and γHA2.X staining, and at molecular levels by quantifying the expression of senescence-associated genes. Next, by performing genetic analysis, we identified Btg2 as a potential regulator of MuSC senescence, which was experimentally validated by Btg2 overexpression and knockdown in primary MuSCs. Lastly, we extended our research to humans by analyzing the potential links between BTG2 and muscle function decline in aging.

RESULTS

BTG2 is highly expressed in MuSCs from elder mice showing senescent phenotypes. Overexpression and knockdown of Btg2 stimulates and prevents MuSCs senescence, respectively. In humans, high level of BTG2 is associated with low muscle mass in aging, and is a risk factor of aging-related diseases, such as diabetic retinopathy and HDL cholesterol.

CONCLUSION

Our work demonstrates BTG2 as a regulator of MuSC senescence and may serve as an intervention target for muscle aging.

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.

Progress in and Prospects of Genome Editing Tools for Human Disease Model Development and Therapeutic Applications

Programmable nucleases, such as zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas, are widely accepted because of their diversity and enormous potential for targeted genomic modifications in eukaryotes and other animals. Moreover, rapid advances in genome editing tools have accelerated the ability to produce various genetically modified animal models for studying human diseases. Given the advances in gene editing tools, these animal models are gradually evolving toward mimicking human diseases through the introduction of human pathogenic mutations in their genome rather than the conventional gene knockout. In the present review, we summarize the current progress in and discuss the prospects for developing mouse models of human diseases and their therapeutic applications based on advances in the study of programmable nucleases.

Manifold epigenetics: A conceptual model that guides engineering strategies to improve whole-body regenerative health

Despite the promising advances in regenerative medicine, there is a critical need for improved therapies. For example, delaying aging and improving healthspan is an imminent societal challenge. Our ability to identify biological cues as well as communications between cells and organs are keys to enhance regenerative health and improve patient care. Epigenetics represents one of the major biological mechanisms involving in tissue regeneration, and therefore can be viewed as a systemic (body-wide) control. However, how epigenetic regulations concertedly lead to the development of biological memories at the whole-body level remains unclear. Here, we review the evolving definitions of epigenetics and identify missing links. We then propose our Manifold Epigenetic Model (MEMo) as a conceptual framework to explain how epigenetic memory arises and discuss what strategies can be applied to manipulate the body-wide memory. In summary we provide a conceptual roadmap for the development of new engineering approaches to improve regenerative health.

The Anaphase-Promoting Complex/Cyclosome Is a Cellular Ageing Regulator

The anaphase-promoting complex/cyclosome (APC/C) is a complicated cellular component that plays significant roles in regulating the cell cycle process of eukaryotic organisms. The spatiotemporal regulation mechanisms of APC/C in distinct cell cycle transitions are no longer mysterious, and the components of this protein complex are gradually identified and characterized. Given the close relationship between the cell cycle and lifespan, it is urgent to understand the roles of APC/C in lifespan regulation, but this field still seems to have not been systematically summarized. Furthermore, although several reviews have reported the roles of APC/C in cancer, there are still gaps in the summary of its roles in other age-related diseases. In this review, we propose that the APC/C is a novel cellular ageing regulator based on its indispensable role in the regulation of lifespan and its involvement in age-associated diseases. This work provides an extensive review of aspects related to the underlying mechanisms of APC/C in lifespan regulation and how it participates in age-associated diseases. More comprehensive recognition and understanding of the relationship between APC/C and ageing and age-related diseases will increase the development of targeted strategies for human health.

Role of angiotensin II in aging

Aging is an inevitable progressive decline in physiological organ function that increases the chance of disease and death. The renin-angiotensin system (RAS) is involved in the regulation of vasoconstriction, fluid homeostasis, cell growth, fibrosis, inflammation, and oxidative stress. In recent years, unprecedented advancement has been made in the RAS study, particularly with the observation that angiotensin II (Ang II), the central product of the RAS, plays a significant role in aging and chronic disease burden with aging. Binding to its receptors (Ang II type 1 receptor - AT1R in particular), Ang II acts as a mediator in the aging process by increasing free radical production and, consequently, mitochondrial dysfunction and telomere attrition. In this review, we examine the physiological function of the RAS and reactive oxygen species (ROS) sources in detail, highlighting how Ang II amplifies or drives mitochondrial dysfunction and telomere attrition underlying each hallmark of aging and contributes to the development of aging and age-linked diseases. Accordingly, the Ang II/AT1R pathway opens a new preventive and therapeutic direction for delaying aging and reducing the incidence of age-related diseases in the future.

Aging of mesenchymal stem cell: machinery, markers, and strategies of fighting

Human mesenchymal stem cells (MSCs) are primary multipotent cells capable of differentiating into osteocytes, chondrocytes, and adipocytes when stimulated under appropriate conditions. The role of MSCs in tissue homeostasis, aging-related diseases, and cellular therapy is clinically suggested. As aging is a universal problem that has large socioeconomic effects, an improved understanding of the concepts of aging can direct public policies that reduce its adverse impacts on the healthcare system and humanity. Several studies of aging have been carried out over several years to understand the phenomenon and different factors affecting human aging. A reduced ability of adult stem cell populations to reproduce and regenerate is one of the main  contributors to the human aging process. In this context, MSCs senescence is a major challenge in front of cellular therapy advancement. Many factors, ranging from genetic and metabolic pathways to extrinsic factors through various cellular signaling pathways, are involved in regulating the mechanism of MSC senescence. To better understand and reverse cellular senescence, this review highlights the underlying mechanisms and signs of MSC cellular senescence, and discusses the strategies to combat aging and cellular senescence.

DNA damage contributes to age-associated differences in SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is known to disproportionately affect older individuals. How aging processes affect SARS-CoV-2 infection and disease progression remains largely unknown. Here, we found that DNA damage, one of the hallmarks of aging, promoted SARS-CoV-2 infection in vitro and in vivo. SARS-CoV-2 entry was facilitated by DNA damage caused by extrinsic genotoxic stress or telomere dysfunction and hampered by inhibition of the DNA damage response (DDR). Mechanistic analysis revealed that DDR increased expression of angiotensin-converting enzyme 2 (ACE2), the primary receptor of SARS-CoV-2, by activation of transcription factor c-Jun. Importantly, in vivo experiment using a mouse-adapted viral strain also verified the significant roles of DNA damage in viral entry and severity of infection. Expression of ACE2 was elevated in the older human and mice tissues and positively correlated with γH2AX, a DNA damage biomarker, and phosphorylated c-Jun (p-c-Jun). Finally, nicotinamide mononucleotide (NMN) and MDL-800, which promote DNA repair, alleviated SARS-CoV-2 infection and disease severity in vitro and in vivo. Taken together, our data provide insights into the age-associated differences in SARS-CoV-2 infection and a novel approach for antiviral intervention.

Inhibition of glutaminolysis restores mitochondrial function in senescent stem cells

Mitochondrial dysfunction, a hallmark of aging, has been associated with the onset of aging phenotypes and age-related diseases. Here, we report that impaired mitochondrial function is associated with increased glutamine catabolism in senescent human mesenchymal stem cells (MSCs) and myofibroblasts derived from patients suffering from Hutchinson-Gilford progeria syndrome. Increased glutaminase (GLS1) activity accompanied by loss of urea transporter SLC14A1 induces urea accumulation, mitochondrial dysfunction, and DNA damage. Conversely, blocking GLS1 activity restores mitochondrial function and leads to amelioration of aging hallmarks. Interestingly, GLS1 expression is regulated through the JNK pathway, as demonstrated by chemical and genetic inhibition. In agreement with our in vitro findings, tissues isolated from aged or progeria mice display increased urea accumulation and GLS1 activity, concomitant with declined mitochondrial function. Inhibition of glutaminolysis in progeria mice improves mitochondrial respiratory chain activity, suggesting that targeting glutaminolysis may be a promising strategy for restoring age-associated loss of mitochondrial function.

Lamin A to Z in normal aging

Almost since the discovery that mutations in the LMNA gene, encoding the nuclear structure components lamin A and C, lead to Hutchinson-Gilford progeria syndrome, people have speculated that lamins may have a role in normal aging. The most common HPGS mutation creates a splice variant of lamin A, progerin, which promotes accelerated aging pathology. While some evidence exists that progerin accumulates with normal aging, an increasing body of work indicates that prelamin A, a precursor of lamin A prior to C-terminal proteolytic processing, accumulates with age and may be a driver of normal aging. Prelamin A shares properties with progerin and is also linked to a rare progeroid disease, restrictive dermopathy. Here, we describe mechanisms underlying changes in prelamin A with aging and lay out the case that this unprocessed protein impacts normative aging. This is important since intervention strategies can be developed to modify this pathway as a means to extend healthspan and lifespan.

In vivo stress reporters as early biomarkers of the cellular changes associated with progeria

Age‐related diseases account for a high proportion of the total global burden of disease. Despite recent advances in understanding their molecular basis, there is a lack of suitable early biomarkers to test selected compounds and accelerate their translation to clinical trials. We have investigated the utility of in vivo stress reporter systems as surrogate early biomarkers of the degenerative disease progression. We hypothesized that cellular stress observed in models of human degenerative disease preceded overt cellular damage and at the same time will identify potential cytoprotective pathways. To test this hypothesis, we generated novel accelerated ageing (progeria) reporter mice by crossing the LmnaG609G mice into our oxidative stress/inflammation (Hmox1) and DNA damage (p21) stress reporter models. Histological analysis of reporter expression demonstrated a time‐dependent and tissue‐specific activation of the reporters in tissues directly associated with Progeria, including smooth muscle cells, the vasculature and gastrointestinal tract. Importantly, reporter expression was detected prior to any perceptible deleterious phenotype. Reporter expression can therefore be used as an early marker of progeria pathogenesis and to test therapeutic interventions. This work also demonstrates the potential to use stress reporter approaches to study and find new treatments for other degenerative diseases.

Accelerated aging in cyclophilin B deficient mice downstream of p21‐Cip1 /Waf1

Loss of bone mass and strength is a common problem of advanced age in humans. Defective bone is also a primary finding in osteogenesis imperfecta (OI), a genetic condition most commonly caused by autosomal dominant mutations in the type I collagen genes. Although altered collagen has been proposed to correlate with cellular processes that underlie aging, the causal relationships between them in vivo have not yet been completely explored. Whether aging plays a promoting role in OI development or whether OI contributes to aging, also remains unknown. The PpiB gene encodes cyclophilin B (CypB), a prolyl isomerase residing in the endoplasmic reticulum required for normal assembly of collagen. Germline deletion or mutations of CypB in mice or humans cause autosomal recessive OI (type IX). Here, we show that mice lacking CypB develop early onset of aging‐associated phenotypes, including kyphosis, fat reduction and weight loss, as well as abnormal teeth, skin, and muscle. Elevated senescence‐associated beta‐galactosidase (SA‐β‐Gal) activity was observed in fat tissues and in bone marrow–derived multipotent stromal cells. Protein levels of the cyclin‐dependent kinase (cdk)‐inhibitor p21‐Cip1/Waf1, a well known senescence marker, were significantly elevated in CypB‐deficient primary cells and mouse tissues. Importantly, loss of p21 in CypB knockout mice attenuated SA‐β‐Gal activity and delayed the development of kyphosis. In addition, less adipose tissue depot and higher SA‐β‐Gal activity were observed in a second OI model, Cola2^oim mutant mice. A potential upregulation of p21 was also revealed in a limited number of these mice. These findings suggest that some of the features in OI patients may be mediated in part through activation of the p21‐dependent pathway, one of which is closely associated with senescence and aging. This study provides new mechanistic insight into relationships between OI and aging and raises the possibility of using senolytics drugs to treat OI in the future. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Mechanisms involved in hematopoietic stem cell aging

Hematopoietic stem cells (HSCs) undergo progressive functional decline over time due to both internal and external stressors, leading to aging of the hematopoietic system. A comprehensive understanding of the molecular mechanisms underlying HSC aging will be valuable in developing novel therapies for HSC rejuvenation and to prevent the onset of several age-associated diseases and hematological malignancies. This review considers the general causes of HSC aging that range from cell-intrinsic factors to cell-extrinsic factors. In particular, epigenetics and inflammation have been implicated in the linkage of HSC aging, clonality, and oncogenesis. The challenges in clarifying mechanisms of HSC aging have accelerated the development of therapeutic interventions to rejuvenate HSCs, the major goal of aging research; these details are also discussed in this review.

Cellular senescence: a key therapeutic target in aging and diseases

Cellular senescence is a hallmark of aging defined by stable exit from the cell cycle in response to cellular damage and stress. Senescent cells (SnCs) can develop a characteristic pathogenic senescence-associated secretory phenotype (SASP) that drives secondary senescence and disrupts tissue homeostasis, resulting in loss of tissue repair and regeneration. The use of transgenic mouse models in which SnCs can be genetically ablated has established a key role for SnCs in driving aging and age-related disease. Importantly, senotherapeutics have been developed to pharmacologically eliminate SnCs, termed senolytics, or suppress the SASP and other markers of senescence, termed senomorphics. Based on extensive preclinical studies as well as small clinical trials demonstrating the benefits of senotherapeutics, multiple clinical trials are under way. This Review discusses the role of SnCs in aging and age-related diseases, strategies to target SnCs, approaches to discover and develop senotherapeutics, and preclinical and clinical advances of senolytics.

Optimized Protocol for Proportionate CNS Cell Retrieval as a Versatile Platform for Cellular and Molecular Phenomapping in Aging and Neurodegeneration

Efficient purification of viable neural cells from the mature CNS has been historically challenging due to the heterogeneity of the inherent cell populations. Moreover, changes in cellular interconnections, membrane lipid and cholesterol compositions, compartment-specific biophysical properties, and intercellular space constituents demand technical adjustments for cell isolation at different stages of maturation and aging. Though such obstacles are addressed and partially overcome for embryonic premature and mature CNS tissues, procedural adaptations to an aged, progeroid, and degenerative CNS environment are underrepresented. Here, we describe a practical workflow for the acquisition and phenomapping of CNS neural cells at states of health, physiological and precocious aging, and genetically provoked neurodegeneration. Following recent, unprecedented evidence of post-mitotic cellular senescence (PoMiCS), the protocol appears suitable for such de novo characterization and phenotypic opposition to classical senescence. Technically, the protocol is rapid, efficient as for cellular yield and well preserves physiological cell proportions. It is suitable for a variety of downstream applications aiming at cell type-specific interrogations, including cell culture systems, Flow-FISH, flow cytometry/FACS, senescence studies, and retrieval of omic-scale DNA, RNA, and protein profiles. We expect suitability for transfer to other CNS targets and to a broad spectrum of engineered systems addressing aging, neurodegeneration, progeria, and senescence.

Distinct and diverse chromatin-proteomes of ageing mouse organs reveal protein signatures that correlate with physiological functions

Temporal molecular changes in ageing mammalian organs are of relevance to disease aetiology because many age-related diseases are linked to changes in the transcriptional and epigenetic machinery that regulate gene expression. We performed quantitative proteome analysis of chromatin-enriched protein extracts to investigate the dynamics of the chromatin proteomes of the mouse brain, heart, lung, kidney, liver, and spleen at 3, 5, 10, and 15 months of age. Each organ exhibited a distinct chromatin proteome and sets of unique proteins. The brain and spleen chromatin proteomes were the most extensive, diverse, and heterogenous among the six organs. The spleen chromatin proteome appeared static during the lifespan, presenting a young phenotype that reflects the permanent alertness state and important role of this organ in physiological defence and immunity. We identified a total of 5928 proteins, including 2472 nuclear or chromatin-associated proteins across the six mouse organs. Up to 3125 proteins were quantified in each organ, demonstrating distinct and organ-specific temporal protein expression timelines and regulation at the post-translational level. Bioinformatics meta-analysis of these chromatin proteomes revealed distinct physiological and ageing-related features for each organ. Our results demonstrate the efficiency of organelle-specific proteomics for in vivo studies of a model organism and consolidate the hypothesis that chromatin-associated proteins are involved in distinct and specific physiological functions in ageing organs.

High prevalence of myeloid malignancies in progeria with Werner syndrome is associated with p53 insufficiency

Werner syndrome (WS) is a progeroid syndrome caused by mutations in the WRN gene, which encodes the RecQ type DNA helicase for the unwinding of unusual DNA structures and is implicated in DNA replication, DNA repair, and telomere maintenance. WS patients are prone to develop malignant neoplasms, including hematological malignancies. However, the pathogenesis of WS-associated hematological malignancies remains uncharacterized. Here we investigated the somatic gene mutations in WS-associated MDS/AML. Whole-exome sequencing (WES) of 4 WS patients with MDS/AML revealed that all patients had somatic mutations in TP53 but no other recurrent mutations in MDS/AML. TP53 mutations were identified at low allele frequencies at more than one year before the MDS/AML stage. All 4 patients had complex chromosomal abnormalities including those that involved TP53. Targeted sequencing of 9 WS patients without apparent blood abnormalities did not detect recurrent mutations in MDS/AML except for a PPM1D mutation. These results suggest that WS patients are apt to acquire TP53 mutations and/or chromosomal abnormalities involving TP53, rather than other MDS/AML-related mutations. TP53 mutations are frequently associated with prior exposure to chemotherapy; however, all 4 WS patients with TP53 mutations/deletions had not received any prior chemotherapy, suggesting a pathogenic link between WRN mutations and p53 insufficiency. These results indicate that WS hematopoietic stem cells with WRN insufficiency acquire competitive fitness by inactivating p53, which may cause complex chromosomal abnormalities and the subsequent development of myeloid malignancies. These findings promote our understanding of the pathogenesis of myeloid malignancies associated with progeria.

Splicing Variants, Protein-Protein Interactions, and Drug Targeting in Hutchinson-Gilford Progeria Syndrome and Small Cell Lung Cancer

Alternative splicing (AS) is a biological operation that enables a messenger RNA to encode protein variants (isoforms) that give one gene several functions or properties. This process provides one of the major sources of use for understanding the proteomic diversity of multicellular organisms. In combination with post-translational modifications, it contributes to generating a variety of protein–protein interactions (PPIs) that are essential to cellular homeostasis or proteostasis. However, cells exposed to many kinds of stresses (aging, genetic changes, carcinogens, etc.) sometimes derive cancer or disease onset from aberrant PPIs caused by DNA mutations. In this review, we summarize how splicing variants may form a neomorphic protein complex and cause diseases such as Hutchinson-Gilford progeria syndrome (HGPS) and small cell lung cancer (SCLC), and we discuss how protein–protein interfaces obtained from the variants may represent efficient therapeutic target sites to treat HGPS and SCLC.

ATM modulates subventricular zone neural stem cell maintenance and senescence through Notch signaling pathway

Ataxia telangiectasia mutated (ATM) plays an essential role in DNA damage response and the maintenance of genomic stability. However, the role of ATM in regulating the function of adult neural stem cells (NSCs) remains unclear. Here we report that ATM deficiency led to accumulated DNA damage and decreased DNA damage repair capacity in neural progenitor cells. Moreover, we observed ATM ablation lead to the short-term increase of proliferation of neural progenitor cells, resulting in the depletion of the NSC pool over time, and this loss of NSC quiescence resulted in accelerated cell senescence. We further apply RNA sequencing to unravel that ATM knockout significantly affected Notch signaling pathway, furthermore, notch activation inhibit the abnormal increased proliferation of ATM^-/- NSCs. Taken together, these findings indicate that ATM can serve as a key regulator for the normal function of adult NSCs by maintaining their stemness and preventing cellular senescence primarily through Notch signaling pathway.

More Than Skin Deep - the Effects of Ultraviolet Radiation on Cathepsin K and Progerin Expression in Cultured Dermal Fibroblasts

Introduction

Photoaging is a premature skin aging developing secondarily to the excessive exposure to ultraviolet radiation. Due to its complexity, an exact mechanism of photoaging has not been found yet; however, recent research has shown two new emerging players in this process – cathepsin K and progerin.

Aim

To evaluate how different wavelengths of ultraviolet radiation (UVA, narrowband UVB and broadband UVB) influence cathepsin K and progerin protein and mRNA expression in dermal cultured fibroblasts.

Materials and Methods

Primary human dermal fibroblasts (Detroit 551, ATCC CCL-110) were cultured and irradiated with UVA, narrowband UVB (UVBnb) and broadband UVB (UVBwb). Fibroblasts were irradiated with 2 protocols: single high-dose exposure to UVR with protein/mRNA extraction immediately after exposure, 24 h after exposure and 48 h after exposure, and repeated (0 h, 24 h and 48 h) low-dose exposure to UVR with protein/mRNA extraction 48 h after first exposure.

Results

Single high doses of UVA, UVBwb and UVBnb resulted in decreased expression of cathepsin K and progerin protein/mRNA in all subsequent time points. Repeated exposure to low doses of UVA results in significant increase of progerin mRNA and significant decrease of progerin protein after 48 h, but repeated exposure to UVBwb and UVBnb resulted in decreased progerin mRNA and protein expression. Repeated exposure to UVA, UVBwb and UVBnb resulted in decreased cathepsin K protein and mRNA expression.

Conclusion

The results suggest that there could be another progerin/cathepsin K regulatory pathway, which has not been described yet. Being contradictory with previous research, the influence of ultraviolet radiation on progerin and cathepsin K needs to be further elucidated.

Rethinking rare disease: longevity-enhancing drug targets through X-linked aneuploidy

Complex diseases, including ageing, often exhibit sexual dimorphism. These sex differences can obfuscate attribution to causal genes within a target ID campaign. Mendelian randomisation (MR)-inspired analysis provides a natural setting to incorporate X-linked aneuploid populations, resulting in prioritisation of longevity-enhancing drug targets and motivating greater inclusion of said populations in future profiling studies.

Role of mismatch repair in aging

A common feature of aging is the accumulation of genetic damage throughout life. DNA damage can lead to genomic instability. Many diseases associated with premature aging are a result of increased accumulation of DNA damage. In order to minimize these damages, organisms have evolved a complex network of DNA repair mechanisms, including mismatch repair (MMR). In this review, we detail the effects of MMR on genomic instability and its role in aging emphasizing on the association between MMR and the other hallmarks of aging, serving to drive or amplify these mechanisms. These hallmarks include telomere attrition, epigenetic alterations, mitochondrial dysfunction, altered nutrient sensing and cell senescence. The close relationship between MMR and these markers may provide prevention and treatment strategies, to reduce the incidence of age-related diseases and promote the healthy aging of human beings.

Neurovascular dysfunction and neuroinflammation in a Cockayne syndrome mouse model

Cockayne syndrome (CS) is a rare, autosomal genetic disorder characterized by premature aging-like features, such as cachectic dwarfism, retinal atrophy, and progressive neurodegeneration. The molecular defect in CS lies in genes associated with the transcription-coupled branch of the nucleotide excision DNA repair (NER) pathway, though it is not yet clear how DNA repair deficiency leads to the multiorgan dysfunction symptoms of CS. In this work, we used a mouse model of severe CS with complete loss of NER (Csa-/-/Xpa-/-), which recapitulates several CS-related phenotypes, resulting in premature death of these mice at approximately 20 weeks of age. Although this CS model exhibits a severe progeroid phenotype, we found no evidence of in vitro endothelial cell dysfunction, as assessed by measuring population doubling time, migration capacity, and ICAM-1 expression. Furthermore, aortas from CX mice did not exhibit early senescence nor reduced angiogenesis capacity. Despite these observations, CX mice presented blood brain barrier disruption and increased senescence of brain endothelial cells. This was accompanied by an upregulation of inflammatory markers in the brains of CX mice, such as ICAM-1, TNFα, p-p65, and glial cell activation. Inhibition of neovascularization did not exacerbate neither astro- nor microgliosis, suggesting that the pro-inflammatory phenotype is independent of the neurovascular dysfunction present in CX mice. These findings have implications for the etiology of this disease and could contribute to the study of novel therapeutic targets for treating Cockayne syndrome patients.

Vascular Aging in Rodent Models: Contrasting Mechanisms Driving the Female and Male Vascular Senescence

Increasing scientific interest has been directed to sex as a biological and decisive factor on several diseases. Several different mechanisms orchestrate vascular function, as well as vascular dysfunction in cardiovascular and metabolic diseases in males and females. Certain vascular sex differences are present throughout life, while others are more evident before the menopause, suggesting two important and correlated drivers: genetic and hormonal factors. With the increasing life expectancy and aging population, studies on aging-related diseases and aging-related physiological changes have steeply grown and, with them, the use of aging animal models. Mouse and rat models of aging, the most studied laboratory animals in aging research, exhibit sex differences in many systems and physiological functions, as well as sex differences in the aging process and aging-associated cardiovascular changes. In the present review, we introduce the most common aging and senescence-accelerated animal models and emphasize that sex is a biological variable that should be considered in aging studies. Sex differences in the cardiovascular system, with a focus on sex differences in aging-associated vascular alterations (endothelial dysfunction, remodeling and oxidative and inflammatory processes) in these animal models are reviewed and discussed.

Opportunities and Challenges in Stem Cell Aging

Studying aging, as a physiological process that can cause various pathological phenotypes, has attracted lots of attention due to its increasing burden and prevalence. Therefore, understanding its mechanism to find novel therapeutic alternatives for age-related disorders such as neurodegenerative and cardiovascular diseases is essential. Stem cell senescence plays an important role in aging. In the context of the underlying pathways, mitochondrial dysfunction, epigenetic and genetic alterations, and other mechanisms have been studied and as a consequence, several rejuvenation strategies targeting these mechanisms like pharmaceutical interventions, genetic modification, and cellular reprogramming have been proposed. On the other hand, since stem cells have great potential for disease modeling, they have been useful for representing aging and its associated disorders. Accordingly, the main mechanisms of senescence in stem cells and promising ways of rejuvenation, along with some examples of stem cell models for aging are introduced and discussed. This review aims to prepare a comprehensive summary of the findings by focusing on the most recent ones to shine a light on this area of research.

Mechanisms of angiogenic incompetence in Hutchinson-Gilford progeria via downregulation of endothelial NOS

Hutchinson–Gilford progeria syndrome (HGPS) is a rare genetic disorder with features of accelerated aging. The majority of HGPS cases are caused by a de novo point mutation in the LMNA gene (c.1824C>T; p.G608G) resulting in progerin, a toxic lamin A protein variant. Children with HGPS typically die from coronary artery diseases or strokes at an average age of 14.6 years. Endothelial dysfunction is a known driver of cardiovascular pathogenesis; however, it is currently unknown how progerin antagonizes normal angiogenic function in HGPS. Here, we use human iPSC‐derived endothelial cell (iPSC‐EC) models to study angiogenesis in HGPS. We cultured normal and HGPS iPSC‐ECs under both static and fluidic culture conditions. HGPS iPSC‐ECs show reduced endothelial nitric oxide synthase (eNOS) expression and activity compared with normal controls and concomitant decreases in intracellular nitric oxide (NO) level, which result in deficits in capillary‐like microvascular network formation. Furthermore, the expression of matrix metalloproteinase 9 (MMP‐9) was reduced in HGPS iPSC‐ECs, while the expression of tissue inhibitor metalloproteinases 1 and 2 (TIMP1 and TIMP2) was upregulated relative to healthy controls. Finally, we used an adenine base editor (ABE7.10max‐VRQR) to correct the pathogenic c.1824C>T allele in HGPS iPSC‐ECs. Remarkably, ABE7.10max‐VRQR correction of the HGPS mutation significantly reduced progerin expression to a basal level, rescued nuclear blebbing, increased intracellular NO level, normalized the misregulated TIMPs, and restored angiogenic competence in HGPS iPSC‐ECs. Together, these results provide molecular insights of endothelial dysfunction in HGPS and suggest that ABE could be a promising therapeutic approach for correcting HGPS‐related cardiovascular phenotypes.

Molecular Interactions between Dietary Lipids and Bone Tissue during Aging

Age-related bone disorders such as osteoporosis or osteoarthritis are a major public health problem due to the functional disability for millions of people worldwide. Furthermore, fractures are associated with a higher degree of morbidity and mortality in the long term, which generates greater financial and health costs. As the world population becomes older, the incidence of this type of disease increases and this effect seems notably greater in those countries that present a more westernized lifestyle. Thus, increased efforts are directed toward reducing risks that need to focus not only on the prevention of bone diseases, but also on the treatment of persons already afflicted. Evidence is accumulating that dietary lipids play an important role in bone health which results relevant to develop effective interventions for prevent bone diseases or alterations, especially in the elderly segment of the population. This review focuses on evidence about the effects of dietary lipids on bone health and describes possible mechanisms to explain how lipids act on bone metabolism during aging. Little work, however, has been accomplished in humans, so this is a challenge for future research.

Targeting cellular senescence in cancer and aging: roles of p53 and its isoforms

Cellular senescence and the associated secretory phenotype (SASP) promote disease in the aged population. Targeting senescent cells by means of removal, modulation of SASP or through cellular reprogramming represents a novel therapeutic avenue for treating cancer- and age-related diseases such as neurodegeneration, pulmonary fibrosis and renal disease. Cellular senescence is partly regulated by the TP53 gene, a critical tumor suppressor gene which encodes 12 or more p53 protein isoforms. This review marks a significant milestone of 40 years of Carcinogenesis publication history and p53 research and 15 years of p53 isoform research. The p53 isoforms are produced through initiation at alternative transcriptional and translational start sites and alternative mRNA splicing. These truncated p53 isoform proteins are endogenously expressed in normal human cells and maintain important functional roles, including modulation of full-length p53-mediated cellular senescence, apoptosis and DNA repair. In this review, we discuss the mechanisms and functions of cellular senescence and SASP in health and disease, the regulation of cellular senescence by p53 isoforms, and the therapeutic potential of targeting cellular senescence to treat cancer- and age-associated diseases.

Epigenetic Regulation of Genomic Stability by Vitamin C

DNA methylation plays an important role in the maintenance of genomic stability. Ten-eleven translocation proteins (TETs) are a family of iron (Fe²⁺) and α-KG -dependent dioxygenases that regulate DNA methylation levels by oxidizing 5-methylcystosine (5mC) to generate 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). These oxidized methylcytosines promote passive demethylation upon DNA replication, or active DNA demethylation, by triggering base excision repair and replacement of 5fC and 5caC with an unmethylated cytosine. Several studies over the last decade have shown that loss of TET function leads to DNA hypermethylation and increased genomic instability. Vitamin C, a cofactor of TET enzymes, increases 5hmC formation and promotes DNA demethylation, suggesting that this essential vitamin, in addition to its antioxidant properties, can also directly influence genomic stability. This review will highlight the functional role of DNA methylation, TET activity and vitamin C, in the crosstalk between DNA methylation and DNA repair.

Stiffness and Aging in Cardiovascular Diseases: The Dangerous Relationship between Force and Senescence

Biological aging is a process associated with a gradual decline in tissues' homeostasis based on the progressive inability of the cells to self-renew. Cellular senescence is one of the hallmarks of the aging process, characterized by an irreversible cell cycle arrest due to reactive oxygen species (ROS) production, telomeres shortening, chronic inflammatory activation, and chromatin modifications. In this review, we will describe the effects of senescence on tissue structure, extracellular matrix (ECM) organization, and nucleus architecture, and see how these changes affect (are affected by) mechano-transduction. In our view, this is essential for a deeper understanding of the progressive pathological evolution of the cardiovascular system and its relationship with the detrimental effects of risk factors, known to act at an epigenetic level.

Can Be miR-126-3p a Biomarker of Premature Aging? An Ex Vivo and In Vitro Study in Fabry Disease

Fabry disease (FD) is a lysosomal storage disorder (LSD) characterized by lysosomal accumulation of glycosphingolipids in a wide variety of cytotypes, including endothelial cells (ECs). FD patients experience a significantly reduced life expectancy compared to the general population; therefore, the association with a premature aging process would be plausible. To assess this hypothesis, miR-126-3p, a senescence-associated microRNA (SA-miRNAs), was considered as an aging biomarker. The levels of miR-126-3p contained in small extracellular vesicles (sEVs), with about 130 nm of diameter, were measured in FD patients and healthy subjects divided into age classes, in vitro, in human umbilical vein endothelial cells (HUVECs) “young” and undergoing replicative senescence, through a quantitative polymerase chain reaction (qPCR) approach. We confirmed that, in vivo, circulating miR-126 levels physiologically increase with age. In vitro, miR-126 augments in HUVECs underwent replicative senescence. We observed that FD patients are characterized by higher miR-126-3p levels in sEVs, compared to age-matched healthy subjects. We also explored, in vitro, the effect on ECs of glycosphingolipids that are typically accumulated in FD patients. We observed that FD storage substances induced in HUVECs premature senescence and increased of miR-126-3p levels. This study reinforces the hypothesis that FD may aggravate the normal aging process.

The aging proteostasis decline: From nematode to human

The aging proteostasis decline manifests in a failure of aging cells and organisms to properly respond to proteotoxic challenges. This proteostasis collapse has long been considered a hallmark of aging in nematodes, and has recently been shown to occur also in human cells upon entry to senescence, opening the way to exploring the phenomenon in the broader context of human aging. Cellular senescence is part of the normal human physiology of aging, with senescent cell accumulation as a prominent feature of aged tissues. Being highly resistant to cell death, senescent cells, as they accumulate, become pro-inflammatory and promote disease. Here we discuss the causes of human senescence proteostasis decline, in view of the current literature on nematodes, on the one hand, and senescence, on the other hand. We review two major aspects of the phenomenon: (1) the decline in transcriptional activation of stress-response pathways, and (2) impairments in proteasome function. We further outline potential underlying mechanisms of transcriptional proteostasis decline, focusing on reduced chromatin dynamics and compromised nuclear integrity. Finally, we discuss potential strategies for reinforcing proteostasis as a means to improve organismal health and address the relationship to senolytics.

FZD5 regulates cellular senescence in human mesenchymal stem/stromal cells

Human mesenchymal stem/stromal cells (hMSCs) have garnered enormous interest as a potential resource for cell‐based therapies. However, the molecular mechanisms regulating senescence in hMSCs remain unclear. To elucidate these mechanisms, we performed gene expression profiling to compare clonal immature MSCs exhibiting multipotency with less potent MSCs. We found that the transcription factor Frizzled 5 (FZD5) is expressed specifically in immature hMSCs. The FZD5 cell surface antigen was also highly expressed in the primary MSC fraction (LNGFR⁺THY‐1⁺) and cultured MSCs. Treatment of cells with the FZD5 ligand WNT5A promoted their proliferation. Upon FZD5 knockdown, hMSCs exhibited markedly attenuated proliferation and differentiation ability. The observed increase in the levels of senescence markers suggested that FZD5 knockdown promotes cellular senescence by regulating the noncanonical Wnt pathway. Conversely, FZD5 overexpression delayed cell cycle arrest during the continued culture of hMSCs. These results indicated that the intrinsic activation of FZD5 plays an essential role in negatively regulating senescence in hMSCs and suggested that controlling FZD5 signaling offers the potential to regulate hMSC quality and improve the efficacy of cell‐replacement therapies using hMSCs.

Cellular proteostasis decline in human senescence

Protein homeostasis (proteostasis), the balance between protein synthesis, folding, and degradation, is thought to deteriorate with age, and the prevalence of protein misfolding diseases (e.g., Alzheimer’s, Parkinson’s, etc.) with human aging is increased. However, while in worms this phenomenon has been well established, in humans, it remained unclear. Here, we show that proteostasis is declined in human cellular aging, termed cellular senescence. We found that while stress sensing is enhanced in senescent cells, and their response at the level of protein synthesis is intact, they fail to properly activate multiple programs required for stress adaptation at the level of gene transcription. Our findings support the notion that proteostasis decline may have major implications on human aging.

Proteostasis collapse, the diminished ability to maintain protein homeostasis, has been established as a hallmark of nematode aging. However, whether proteostasis collapse occurs in humans has remained unclear. Here, we demonstrate that proteostasis decline is intrinsic to human senescence. Using transcriptome-wide characterization of gene expression, splicing, and translation, we found a significant deterioration in the transcriptional activation of the heat shock response in stressed senescent cells. Furthermore, phosphorylated HSF1 nuclear localization and distribution were impaired in senescence. Interestingly, alternative splicing regulation was also dampened. Surprisingly, we found a decoupling between different unfolded protein response (UPR) branches in stressed senescent cells. While young cells initiated UPR-related translational and transcriptional regulatory responses, senescent cells showed enhanced translational regulation and endoplasmic reticulum (ER) stress sensing; however, they were unable to trigger UPR-related transcriptional responses. This was accompanied by diminished ATF6 nuclear localization in stressed senescent cells. Finally, we found that proteasome function was impaired following heat stress in senescent cells, and did not recover upon return to normal temperature. Together, our data unraveled a deterioration in the ability to mount dynamic stress transcriptional programs upon human senescence with broad implications on proteostasis control and connected proteostasis decline to human aging.

METTL3 counteracts premature aging via m6A-dependent stabilization of MIS12 mRNA

N6-Methyladenosine (m6A) messenger RNA methylation is a well-known epitranscriptional regulatory mechanism affecting central biological processes, but its function in human cellular senescence remains uninvestigated. Here, we found that levels of both m6A RNA methylation and the methyltransferase METTL3 were reduced in prematurely senescent human mesenchymal stem cell (hMSC) models of progeroid syndromes. Transcriptional profiling of m6A modifications further identified MIS12, for which m6A modifications were reduced in both prematurely senescent hMSCs and METTL3-deficient hMSCs. Knockout of METTL3 accelerated hMSC senescence whereas overexpression of METTL3 rescued the senescent phenotypes. Mechanistically, loss of m6A modifications accelerated the turnover and decreased the expression of MIS12 mRNA while knockout of MIS12 accelerated cellular senescence. Furthermore, m6A reader IGF2BP2 was identified as a key player in recognizing and stabilizing m6A-modified MIS12 mRNA. Taken together, we discovered that METTL3 alleviates hMSC senescence through m6A modification-dependent stabilization of the MIS12 transcript, representing a novel epitranscriptional mechanism in premature stem cell senescence.

Nutrition in Cancer Therapy in the Elderly-An Epigenetic Connection?

The continuous increase in life expectancy results in a steady increase of cancer risk, which consequently increases the population of older adults with cancer. Older adults have their age-related nutritional needs and often suffer from comorbidities that may affect cancer therapy. They frequently are malnourished and present advanced-stage cancer. Therefore, this group of patients requires a special multidisciplinary approach to optimize their therapy and increase quality of life impaired by aging, cancer, and the side effects of therapy. Evaluation strategies, taking advantage of comprehensive geriatric assessment tools, including the comprehensive geriatric assessment (CGA), can help individualize treatment. As epigenetics, an emerging element of the regulation of gene expression, is involved in both aging and cancer and the epigenetic profile can be modulated by the diet, it seems to be a candidate to assist with planning a nutritional intervention in elderly populations with cancer. In this review, we present problems associated with the diet and nutrition in the elderly undergoing active cancer therapy and provide some information on epigenetic aspects of aging and cancer transformation. Nutritional interventions modulating the epigenetic profile, including caloric restriction and basal diet with modifications (elimination diet, supplementary diet) are discussed as the ways to improve the efficacy of cancer therapy and maintain the quality of life of older adults with cancer.

Premature aging disorders: A clinical and genetic compendium

Progeroid disorders make up a heterogeneous group of very rare hereditary diseases characterized by clinical signs that often mimic physiological aging in a premature manner. Apart from Hutchinson-Gilford progeria syndrome, one of the best-investigated progeroid disorders, a wide spectrum of other premature aging phenotypes exist, which differ significantly in their clinical presentation and molecular pathogenesis. Next-generation sequencing (NGS)-based approaches have made it feasible to determine the molecular diagnosis in the early stages of a disease. Nevertheless, a broad clinical knowledge on these disorders and their associated symptoms is still fundamental for a comprehensive patient management and for the interpretation of variants of unknown significance from NGS data sets. This review provides a detailed overview on characteristic clinical features and underlying molecular genetics of well-known as well as only recently identified premature aging disorders and also highlights novel findings towards future therapeutic options.