Telomere length predicts replicative capacity of human fibroblasts

Uncovering key mechanisms and intervention therapies in aging skin

Advancements in understanding skin aging mechanisms, which encompass both external and internal aging processes, have spurred the development of innovative treatments primarily aimed at improving cosmetic appearance. These findings offer the potential for the development of novel therapeutic strategies aimed at achieving long-term, non-therapy-dependent clinical benefits, including the reversal of aging and the mitigation of associated health conditions. Realizing this goal requires further research to establish the safety and efficacy of targeting aging-related skin changes, such as pigmentation, wrinkling, and collagen loss. Systematic investigation is needed to identify the most effective interventions and determine optimal anti-aging treatment strategies. These reviews highlight the features and possible mechanisms of skin aging, as well as the latest progress and future direction of skin aging research, to provide a theoretical basis for new practical anti-skin aging strategies.

NRF2 signaling pathway and telomere length in aging and age-related diseases

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is well recognized as a critical regulator of redox, metabolic, and protein homeostasis, as well as the regulation of inflammation. An age-associated decline in NRF2 activity may allow oxidative stress to remain unmitigated and affect key features associated with the aging phenotype, including telomere shortening. Telomeres, the protective caps of eukaryotic chromosomes, are highly susceptible to oxidative DNA damage, which can accelerate telomere shortening and, consequently, lead to premature senescence and genomic instability. In this review, we explore how the dysregulation of NRF2, coupled with an increase in oxidative stress, might be a major determinant of telomere shortening and age-related diseases. We discuss the relevance of the connection between NRF2 deficiency in aging and telomere attrition, emphasizing the importance of studying this functional link to enhance our understanding of aging pathologies. Finally, we present a number of compounds that possess the ability to restore NRF2 function, maintain a proper redox balance, and preserve telomere length during aging.

Unusual Age-Dependent Behavior of Leukocytes Telomere Length in Friedreich's Ataxia

BACKGROUND

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by an expanded GAA repeat in the first intron of the FXN gene.

OBJECTIVE

The aim of this study was to analyze leukocyte telomeres length (LTL) in FRDA to verify the possible relationships between LTL and disease progression. We investigated LTL in a cohort of FRDA biallelic patients (n = 61), heterozygous (n = 29), and age-matched healthy subjects (n = 87).

METHODS

LTL was measured by real-time polymerase chain reaction quantitative analysis (qPCR).

RESULTS

The results showed that before 35 years of age, leukocyte telomeres were longer in patients than in controls, whereas the reverse applies in patients above 36 years of age. Interestingly, LTL was greater than controls at any age in heterozygous subjects. This picture mirrors what has been previously observed in vitro in FRDA cultured fibroblasts, showing significantly longer telomeres at early passages because of activation of an alternative lengthening of telomeres (ALT)-like mechanism, but showing accelerated telomere shortening as population doubling increases. GAA1 repeat length is positively correlated with the LTL and negatively correlated with the age at blood sampling. The relationship of LTL with clinical parameters (cardiomyopathy, diabetes, dependence on a wheelchair) was also analyzed. Significantly shorter leukocyte telomeres were associated with the presence of cardiomyopathy, but not with diabetes and the dependence on a wheelchair.

CONCLUSIONS

Overall, the present study indicates that telomere length analysis in FRDA may be a relevant biomarker for following the stages of the disease. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Telomere Length, HLA, and Longevity-Results from a Multicenter Study

Aging is an exceptionally complex process that depends on genetic, environmental, and lifestyle factors. Previous studies within the International HLA and Immunogenetics Workshop (IHIWS) component "Immunogenetics of Ageing" showed that longevity is associated with positive selection of HLA-DRB1*11- and DRB1*16-associated haplotypes, shown to be protective against diseases. Within the 18th IHIWS, we aimed to investigate the relevance of telomere length for successful aging and its association with classical HLAs. In total 957 individuals from Bulgaria, Turkey, Romania, and Poland in two age groups, elderly individuals (age 65-99 years) and ethnically matched young group (age 18-64 years), were investigated. The obtained results confirmed interpopulation differences in the distribution of HLA alleles, documented the lengths of telomeres in analyzed populations, and demonstrated significant associations of telomere length with aging as well as with the presence of some HLA class I or class II alleles. They suggest that telomere length assessment combined with HLA genotyping may help identify immunogenetic profiles associated with longevity. The associations between HLA and telomeres support the theory that HLA genes influence the aging process. However, further research is needed to clarify the biological basis of the observed relationships.

Telomerase RNA structural heterogeneity in living human cells detected by DMS-MaPseq

Telomerase is a specialized reverse transcriptase that uses an intrinsic RNA subunit as the template for telomeric DNA synthesis. Biogenesis of human telomerase requires its RNA subunit (hTR) to fold into a multi-domain architecture that includes the template-containing pseudoknot (t/PK) and the three-way junction (CR4/5). These two hTR domains bind the telomerase reverse transcriptase (hTERT) protein and are thus essential for telomerase catalytic activity. Here, we probe the structure of hTR in living cells using dimethyl sulfate mutational profiling with sequencing (DMS-MaPseq) and ensemble deconvolution analysis. Unexpectedly, approximately 15% of the steady state population of hTR has a CR4/5 conformation lacking features thought to be required for hTERT binding. The proportion of hTR CR4/5 that is folded into the primary functional conformation does not require hTERT expression and the fraction of hTR that assumes a misfolded CR4/5 domain is not refolded by overexpression of its hTERT binding partner. This result suggests a functional role for an RNA folding cofactor other than hTERT during telomerase biogenesis. Mutagenesis demonstrates that stabilization of the alternative CR4/5 conformation is detrimental to telomerase assembly and activity. Moreover, the alternative CR4/5 conformation is not found in telomerase RNP complexes purified from cells via an epitope tag on hTERT, supporting the hypothesis that only the major CR4/5 conformer is active. We propose that this misfolded portion of the cellular hTR pool is either slowly refolded or degraded. Thus, kinetic traps for RNA folding that have been so well-studied in vitro may also present barriers for assembly of ribonucleoprotein complexes in vivo.

Mechanisms of Senescence and Anti-Senescence Strategies in the Skin

The skin is the layer of tissue that covers the largest part of the body in vertebrates, and its main function is to act as a protective barrier against external environmental factors, such as microorganisms, ultraviolet light and mechanical damage. Due to its important function, investigating the factors that lead to skin aging and age-related diseases, as well as understanding the biology of this process, is of high importance. Indeed, it has been reported that several external and internal stressors contribute to skin aging, similar to the aging of other tissues. Moreover, during aging, senescent cells accumulate in the skin and express senescence-associated factors, which act in a paracrine manner on neighboring healthy cells and tissues. In this review, we will present the factors that lead to skin aging and cellular senescence, as well as ways to study senescence in vitro and in vivo. We will further discuss the adverse effects of the accumulation of chronic senescent cells and therapeutic agents and tools to selectively target and eliminate them.

Association Between Adverse Early Life Factors and Telomere Length in Middle and Late Life

Background and Objectives

Telomere length (TL) has been acknowledged as biomarker of biological aging. Numerous investigations have examined associations between individual early life factors and leukocyte TL; however, the findings were far from consistent.

Research Design and Methods

We evaluated the relationship between individual and combined early life factors and leukocytes TL in middle and late life using data from the UK Biobank. The early life factors (eg, maternal smoking, breastfeeding, birth weight, and comparative body size and height to peers at age 10) were measured. The regression coefficients (β) and 95% confidence interval (CI) were applied to assess the link of the early life factors and TL in adulthood. Flexible parametric survival models incorporated age to calculate the relationship between early life factors and life expectancy.

Results

Exposure to maternal smoking, lack of breastfeeding, low birth weight, and shorter height compared to peers at age 10 were identified to be associated with shorter TL in middle and older age according to the large population-based study with 197 504 participants. Individuals who experienced more than 3 adverse early life factors had the shortest TL in middle and late life (β = -0.053; 95% CI = -0.069 to -0.038; p < .0001), as well as an average of 0.54 years of life loss at the age of 45 and 0.49 years of life loss at the age of 60, compared to those who were not exposed to any early life risk factors.

Discussion and Implications

Early life factors including maternal smoking, non-breastfed, low birth weight, and shorter height compared to peers at age 10 were associated with shorter TL in later life. In addition, an increased number of the aforementioned factors was associated with a greater likelihood of shorter TL in adulthood, as well as a reduced life expectancy.

A defective splicing machinery promotes senescence through MDM4 alternative splicing

Defects in the splicing machinery are implicated in various diseases, including cancer. We observed a general reduction in the expression of spliceosome components and splicing regulators in human cell lines undergoing replicative, stress-induced, and telomere uncapping-induced senescence. Supporting the view that defective splicing contributes to senescence, splicing inhibitors herboxidiene, and pladienolide B induced senescence in normal and cancer cell lines. Furthermore, depleting individual spliceosome components also promoted senescence. All senescence types were associated with an alternative splicing transition from the MDM4-FL variant to MDM4-S. The MDM4 splicing shift was reproduced when splicing was inhibited, and spliceosome components were depleted. While decreasing the level of endogenous MDM4 promoted senescence and cell survival independently of the MDM4-S expression status, cell survival was also improved by increasing MDM4-S. Overall, our work establishes that splicing defects modulate the alternative splicing of MDM4 to promote senescence and cell survival.

Therapy-Induced Cellular Senescence: Potentiating Tumor Elimination or Driving Cancer Resistance and Recurrence?

Cellular senescence has been increasingly recognized as a hallmark of cancer, reflecting its association with aging and inflammation, its role as a response to deregulated proliferation and oncogenic stress, and its induction by cancer therapies. While therapy-induced senescence (TIS) has been linked to resistance, recurrence, metastasis, and normal tissue toxicity, TIS also has the potential to enhance therapy response and stimulate anti-tumor immunity. In this review, we examine the Jekyll and Hyde nature of senescent cells (SnCs), focusing on how their persistence while expressing the senescence-associated secretory phenotype (SASP) modulates the tumor microenvironment through autocrine and paracrine mechanisms. Through the SASP, SnCs can mediate both resistance and response to cancer therapies. To fulfill the unmet potential of cancer immunotherapy, we consider how SnCs may influence tumor inflammation and serve as an antigen source to potentiate anti-tumor immune response. This new perspective suggests treatment approaches based on TIS to enhance immune checkpoint blockade. Finally, we describe strategies for mitigating the detrimental effects of senescence, such as modulating the SASP or targeting SnC persistence, which may enhance the overall benefits of cancer treatment.

High resolution long-read telomere sequencing reveals dynamic mechanisms in aging and cancer

Telomeres are the protective nucleoprotein structures at the end of linear eukaryotic chromosomes. Telomeres' repetitive nature and length have traditionally challenged the precise assessment of the composition and length of individual human telomeres. Here, we present Telo-seq to resolve bulk, chromosome arm-specific and allele-specific human telomere lengths using Oxford Nanopore Technologies' native long-read sequencing. Telo-seq resolves telomere shortening in five population doubling increments and reveals intrasample, chromosome arm-specific, allele-specific telomere length heterogeneity. Telo-seq can reliably discriminate between telomerase- and ALT-positive cancer cell lines. Thus, Telo-seq is a tool to study telomere biology during development, aging, and cancer at unprecedented resolution.

The association of sleep duration and leukocyte telomere length in middle-aged and young-old adults: A cross-sectional study of UK Biobank

BACKGROUND

The relationships between sleep duration and aging-associated diseases are intricate. Leukocyte telomere length (LTL) is a biomarker of aging, while the association of sleep duration and LTL is unclear.

METHODS

The 310,091 study participants from UK Biobank were enrolled in this cross-sectional study. Restricted cubic splines (RCS) analysis was firstly performed to assess the nonlinear relationship between sleep duration and LTL. Sleep duration was then categorized into three groups: <7 h (short sleep duration), 7-8 h (reference group), and >8 h (long sleep duration) and multiple linear regression was applied to analyze the association of short sleep and long sleep duration with LTL. We further performed subgroup analyses stratified by sex, age, chronotype and snoring.

RESULTS

RCS showed an inverted J-shaped relationship between sleep duration and LTL. Compared with the reference group, the inverse association of long sleep duration and LTL was statistically significant in fully-adjusted model (P = 0.001). Subgroup analyses showed that this association was more apparent in people over 50 years (51-60 y: P = 0.002; >60 y: P = 0.005), in men (P = 0.022), and in people preferred evening chronotype (P = 0.001).

CONCLUSION

Compared with participants sleeping 7-8 h, those sleep longer than 8 h had shorter LTL in middle-aged and young-old adults. The negative association between long sleep duration and LTL was more apparent in older people, in men, and in people preferred evening chronotype.

Reprogramming Chromosome Ends by Functional Histone Acetylation

Cancers harness embryonic programs to evade aging and promote survival. Normally, sequences at chromosome ends called telomeres shorten with cell division, serving as a countdown clock to limit cell replication. Therefore, a crucial aspect of cancerous transformation is avoiding replicative aging by activation of telomere repair programs. Mouse embryonic stem cells (mESCs) activate a transient expression of the gene Zscan4, which correlates with chromatin de-condensation and telomere extension. Head and neck squamous cell carcinoma (HNSCC) cancers reactivate ZSCAN4, which in turn regulates the phenotype of cancer stem cells (CSCs). Our study reveals a new role for human ZSCAN4 in facilitating functional histone H3 acetylation at telomere chromatin. Next-generation sequencing indicates ZSCAN4 enrichment at telomere chromatin. These changes correlate with ZSCAN4-induced histone H3 acetylation and telomere elongation, while CRISPR/Cas9 knockout of ZSCAN4 leads to reduced H3 acetylation and telomere shortening. Our study elucidates the intricate involvement of ZSCAN4 and its significant contribution to telomere chromatin remodeling. These findings suggest that ZSCAN4 induction serves as a novel link between 'stemness' and telomere maintenance. Targeting ZSCAN4 may offer new therapeutic approaches to effectively limit or enhance the replicative lifespan of stem cells and cancer cells.

Epigenetic dynamics of aging and cancer development: current concepts from studies mapping aging and cancer epigenomes

PURPOSE OF REVIEW

This review emphasizes the role of epigenetic processes as incidental changes occurring during aging, which, in turn, promote the development of cancer.

RECENT FINDINGS

Aging is a complex biological process associated with the progressive deterioration of normal physiological functions, making age a significant risk factor for various disorders, including cancer. The increasing longevity of the population has made cancer a global burden, as the risk of developing most cancers increases with age due to the cumulative effect of exposure to environmental carcinogens and DNA replication errors. The classical 'somatic mutation theory' of cancer cause is being challenged by the observation that multiple normal cells harbor cancer driver mutations without resulting in cancer. In this review, we discuss the role of age-associated epigenetic alterations, including DNA methylation, which occur across all cell types and tissues with advancing age. There is an increasing body of evidence linking these changes with cancer risk and prognosis.

SUMMARY

A better understanding about the epigenetic changes acquired during aging is critical for comprehending the mechanisms leading to the age-associated increase in cancer and for developing novel therapeutic strategies for cancer treatment and prevention.

Guardians of the Genome: How the Single-Stranded DNA-Binding Proteins RPA and CST Facilitate Telomere Replication

Telomeres act as the protective caps of eukaryotic linear chromosomes; thus, proper telomere maintenance is crucial for genome stability. Successful telomere replication is a cornerstone of telomere length regulation, but this process can be fraught due to the many intrinsic challenges telomeres pose to the replication machinery. In addition to the famous "end replication" problem due to the discontinuous nature of lagging strand synthesis, telomeres require various telomere-specific steps for maintaining the proper 3' overhang length. Bulk telomere replication also encounters its own difficulties as telomeres are prone to various forms of replication roadblocks. These roadblocks can result in an increase in replication stress that can cause replication forks to slow, stall, or become reversed. Ultimately, this leads to excess single-stranded DNA (ssDNA) that needs to be managed and protected for replication to continue and to prevent DNA damage and genome instability. RPA and CST are single-stranded DNA-binding protein complexes that play key roles in performing this task and help stabilize stalled forks for continued replication. The interplay between RPA and CST, their functions at telomeres during replication, and their specialized features for helping overcome replication stress at telomeres are the focus of this review.

Social determinants of health and obstetric outcomes: A report and recommendations of the workshop of the Society for Maternal-Fetal Medicine

This article is a report of a 2-day workshop, entitled "Social determinants of health and obstetric outcomes," held during the Society for Maternal-Fetal Medicine 2022 Annual Pregnancy Meeting. Participants' fields of expertise included obstetrics, pediatrics, epidemiology, health services, health equity, community-based research, and systems biology. The Commonwealth Foundation and the Alliance of Innovation on Maternal Health cosponsored the workshop and the Society for Women's Health Research provided additional support. The workshop included presentations and small group discussions, and its goals were to accomplish the following.

Unlocking longevity: the role of telomeres and its targeting interventions

Average life expectancy has been steadily increasing in developed countries worldwide. These demographic changes are associated with an ever-growing social and economic strain to healthcare systems as well as society. The aging process typically manifests as a decline in physiological and cognitive functions, accompanied by a rise in chronic diseases. Consequently, strategies that both mitigate age-related diseases and promote healthy aging are urgently needed. Telomere attrition, characterized by the shortening of telomeres with each cell division, paradoxically serves as both a protective mechanism and a contributor to tissue degeneration and age-related ailments. Based on the essential role of telomere biology in aging, research efforts aim to develop approaches designed to counteract telomere attrition, aiming to delay or reduce age-related diseases. In this review, telomere biology and its role in aging and age-related diseases is summarized along with recent approaches to interfere with telomere shortening aiming at well- and healthy-aging as well as longevity. As aging research enters a new era, this review emphasizes telomere-targeting therapeutics, including telomerase activators and tankyrase inhibitors, while also exploring the effects of antioxidative and anti-inflammatory agents, along with indirectly related approaches like statins.

Structure, Topology, and Stability of Multiple G-quadruplexes in Long Telomeric Overhangs

Telomeres and their single stranded overhangs gradually shorten with successive cell divisions, as part of the natural aging process, but can be elongated by telomerase, a nucleoprotein complex which is activated in the majority of cancers. This prominent implication in cancer and aging has made the repetitive telomeric sequences (TTAGGG repeats) and the G-quadruplex structures that form in their overhangs the focus of intense research in the past several decades. However, until recently most in vitro efforts to understand the structure, stability, dynamics, and interactions of telomeric overhangs had been focused on short sequences that are not representative of longer sequences encountered in a physiological setting. In this review, we will provide a broad perspective about telomeres and associated factors, and introduce the agents and structural characteristics involved in organizing, maintaining, and protecting telomeric DNA. We will also present a summary of recent research performed on long telomeric sequences, nominally defined as those that can form two or more tandem G-quadruplexes, i.e., which contain eight or more TTAGGG repeats. Results of experimental studies using a broad array of experimental tools, in addition to recent computational efforts will be discussed, particularly in terms of their implications for the stability, folding topology, and compactness of the tandem G-quadruplexes that form in long telomeric overhangs.

Causal relationship between telomere length and epilepsy: A bidirectional Mendelian randomization study

OBJECTIVE

Observational studies have suggested a link between telomere length (TL) and epilepsy, but the direction of the effect and whether it is causal or not is still being debated. The objective of this study was to investigate the causal relationship between TL and epilepsy using Mendelian randomization (MR) analysis.

METHODS

We performed a bidirectional two-sample MR analysis using pooled statistics from genome-wide association studies (GWAS) of TL and epilepsy. Additionally, we conducted a replication analysis using data from another GWAS study on epilepsy to validate our findings. The final results were analyzed using five MR methods, with the inverse-variance weighted (IVW) method as the primary outcome. We applied methods such as radial MR, MR pleiotropy residual and outlier test and MR Steiger filters to exclude outliers. Sensitivity analyses were also conducted to assess heterogeneity and pleiotropy.

RESULTS

Our analysis found no evidence of a causal relationship between epilepsy and TL (all p-values >0.05). The sensitivity analysis confirms the robustness of these results.

SIGNIFICANCE

In summary, our study contradicts existing observational reports by not finding any evidence to support a causal relationship between epilepsy and TL. Further research is necessary to determine the underlying mechanism behind the association observed in observational studies.

Telomere length is associated with increased risk of cutaneous melanoma: a Mendelian randomization study

RESULTS

The MR analysis using two TL GWAS datasets revealed strong and consistent evidence that long TL is causally associated with an increased risk of CM. The analysis of the Codd et al. dataset found that long TL significantly predicted an elevated risk of CM (IVW OR = 2.411, 95% CI 2.092-2.780, P = 8.05E-34). Similarly, the analysis of the Li et al. dataset yielded consistent positive results across all MR methods, providing further robustness to the causal relationship (IVW OR = 2.324, 95% CI 1.516-3.565, P = 1.11E-04). The study provides evidence for a causal association between TL and CM susceptibility, indicating that longer TL increases the risk of developing CM and providing insight into the unique telomere biology in melanoma pathogenesis. Telomere maintenance pathways may be a potential target for preventing and treating CM.

Anti-Aging Activity and Modes of Action of Compounds from Natural Food Sources

Aging is a natural and inescapable phenomenon characterized by a progressive deterioration of physiological functions, leading to increased vulnerability to chronic diseases and death. With economic and medical development, the elderly population is gradually increasing, which poses a great burden to society, the economy and the medical field. Thus, healthy aging has now become a common aspiration among people over the world. Accumulating evidence indicates that substances that can mediate the deteriorated physiological processes are highly likely to have the potential to prolong lifespan and improve aging-associated diseases. Foods from natural sources are full of bioactive compounds, such as polysaccharides, polyphenols, carotenoids, sterols, terpenoids and vitamins. These bioactive compounds and their derivatives have been shown to be able to delay aging and/or improve aging-associated diseases, thereby prolonging lifespan, via regulation of various physiological processes. Here, we summarize the current understanding of the anti-aging activities of the compounds, polysaccharides, polyphenols, carotenoids, sterols, terpenoids and vitamins from natural food sources, and their modes of action in delaying aging and improving aging-associated diseases. This will certainly provide a reference for further research on the anti-aging effects of bioactive compounds from natural food sources.

TERRA expression is regulated by the telomere-binding proteins POT-1 and POT-2 in Caenorhabditis elegans

Several aspects of telomere biology are regulated by the telomeric repeat-containing RNA TERRA. While TERRA expression is conserved through evolution, species-specific mechanisms regulate its biogenesis and function. Here we report on the expression of TERRA in Caenorhabditis elegans. We show that C. elegans TERRA is regulated by the telomere-binding proteins POT-1 and POT-2 which repress TERRA in a telomere-specific manner. C. elegans TERRA transcripts are heterogeneous in length and form discrete nuclear foci, as detected by RNA FISH, in both postmitotic and germline cells; a fraction of TERRA foci localizes to telomeres. Interestingly, in germ cells, TERRA is expressed in all stages of meiotic prophase I, and it increases during pachytene, a stage in meiosis when homologous recombination is ongoing. We used the MS2-GFP system to study the spatiotemporal dynamics of single-telomere TERRA molecules. Single particle tracking revealed different types of motilities, suggesting complex dynamics of TERRA transcripts. Finally, we unveiled distinctive features of C. elegans TERRA, which is regulated by telomere shortening in a telomere-specific manner, and it is upregulated in the telomerase-deficient trt-1; pot-2 double mutant prior to activation of the alternative lengthening mechanism ALT. Interestingly, in these worms TERRA displays distinct dynamics with a higher fraction of fast-moving particles.

Approaches in line with human physiology to prevent skin aging

Skin aging is a complex process that is influenced by intrinsic and extrinsic factors that impact the skin's protective functions and overall health. As the body's outermost layer, the skin plays a critical role in defending it against external threats, regulating body temperature, providing tactile sensation, and synthesizing vitamin D for bone health, immune function, and body homeostasis. However, as individuals age, the skin undergoes structural and functional changes, leading to impairments in these essential functions. In contemporary society, there is an increasing recognition of skin health as a significant indicator of overall wellbeing, resulting in a growing demand for anti-aging products and treatments. However, these products often have limitations in terms of safety, effective skin penetration, and potential systemic complications. To address these concerns, researchers are now focusing on approaches that are safer and better aligned with physiology of the skin. These approaches include adopting a proper diet and maintaining healthy lifestyle habits, the development of topical treatments that synchronize with the skin's circadian rhythm, utilizing endogenous antioxidant molecules, such as melatonin and natural products like polyphenols. Moreover, exploring alternative compounds for sun protection, such as natural ultraviolet (UV)-absorbing compounds, can offer safer options for shielding the skin from harmful radiation. Researchers are currently exploring the potential of adipose-derived stem cells, cell-free blood cell secretome (BCS) and other endogenous compounds for maintaining skin health. These approaches are more secure and more effective alternatives which are in line with human physiology to tackle skin aging. By emphasizing these innovative strategies, it is possible to develop effective treatments that not only slow down the skin aging process but also align better with the natural physiology of the skin. This review will focus on recent research in this field, highlighting the potential of these treatments as being safer and more in line with the skin's physiology in order to combat the signs of aging.

Telomere Length Associations With Clinical Diagnosis, Age, and Polygenic Risk Scores for Anxiety Disorder, Depression, and Bipolar Disorder

Background

Accelerated biological aging might contribute to the lower life expectancy of individuals with mental disorders. The aim of this study was to characterize telomere length, a biological hallmark of aging, in individuals with mental disorders.

Methods

The UK Biobank is a multicenter community-based observational study that recruited >500,000 middle-aged and older adults. Average leukocyte telomere length (telomere repeat copy number/single-copy gene ratio) was measured using quantitative polymerase chain reaction. Polygenic risk scores (PRSs) were calculated for individuals of European ancestry. We estimated differences in telomere length between individuals with anxiety disorder, depression, or bipolar disorder and people without mental disorders and examined associations with psychotropic medication use, age, and PRSs for these 3 disorders.

Results

The analyses included up to 308,725 participants. Individuals with depression had shorter telomeres than people without mental disorders (β = -0.011, 95% CI, -0.019 to -0.004, Bonferroni-corrected p = .027). Associations between bipolar disorder and telomere length differed by lithium use. There was limited evidence that individuals with an anxiety disorder had shorter telomeres. There was no evidence that associations between age and telomere length differed between individuals with and without these disorders. PRSs for depression, but not anxiety disorder or bipolar disorder, were associated with shorter telomeres (β = -0.006, 95% CI, -0.010 to -0.003, Bonferroni-corrected p = .001).

Conclusions

Differences in telomere length were observed primarily for individuals with depression or bipolar disorder and in individuals with a higher PRS for depression. There was no evidence that the association between age and telomere length differed between individuals with and without an anxiety disorder, depression, or bipolar disorder.

Dynamics of redox signaling in aging via autophagy, inflammation, and senescence

Review paper attempts to explain the dynamic aspects of redox signaling in aging through autophagy, inflammation, and senescence. It begins with ROS source in the cell, then states redox signaling in autophagy, and regulation of autophagy in aging. Next, we discuss inflammation and redox signaling with various pathways involved: NOX pathway, ROS production via TNF-α, IL-1β, xanthine oxidase pathway, COX pathway, and myeloperoxidase pathway. Also, we emphasize oxidative damage as an aging marker and the contribution of pathophysiological factors to aging. In senescence-associated secretory phenotypes, we link ROS with senescence, aging disorders. Relevant crosstalk between autophagy, inflammation, and senescence using a balanced ROS level might reduce age-related disorders. Transducing the context-dependent signal communication among these three processes at high spatiotemporal resolution demands other tools like multi-omics aging biomarkers, artificial intelligence, machine learning, and deep learning. The bewildering advancement of technology in the above areas might progress age-related disorders diagnostics with precision and accuracy.

Low Antioxidant Glutathione Levels Lead to Longer Telomeres: A Sex-Specific Link to Longevity?

Telomeres are repetitive DNA sequences at the end of chromosomes that protect them from degradation. They have been the focus of intense research because short telomeres would predict accelerated ageing and reduced longevity in vertebrates. Oxidative stress is considered a physiological driver of the telomere shortening and, consequently, short lifespan. Among molecules fighting against oxidative stress, glutathione is involved in many antioxidant pathways. Literature supports that oxidative stress may trigger a compensatory "hormetic" response increasing glutathione levels and telomere length. Here, we tested the link between total glutathione concentration and telomere length in captive birds (zebra finches; Taeniopygia guttata). Total glutathione levels were experimentally decreased during birds' growth using a specific inhibitor of glutathione synthesis (buthionine sulfoximine; BSO). We monitored the birds' reproductive performance in an outdoor aviary during the first month of life, and their longevity for almost 9 years. Among control individuals, erythrocyte glutathione levels during development positively predicted erythrocyte telomere length in adulthood. However, BSO-treated females, but not males, showed longer telomeres than control females in adulthood. This counterintuitive finding suggests that females mounted a compensatory response. Such compensation agrees with precedent findings in the same population where the BSO treatment increased growth and adult body mass in females but not males. BSO did not influence longevity or reproductive output in any sex. However, early glutathione levels and adult telomere length interactively predicted longevity only among control females. Those females with "naturally" low (non-manipulated) glutathione levels at the nestling age but capable of producing longer telomeres in adulthood seem to live longer. The results suggest that the capability to mount a hormetic response triggered by low early glutathione levels can improve fitness via telomere length. Overall, the results may indicate a sex-specific link between glutathione and telomere values. Telomerase activity and sexual steroids (estrogens) are good candidates to explain the sex-biased mechanism underlying the early-life impact of oxidative stress on adult telomere length.

The multistep path to replicative senescence onset: zooming on triggering and inhibitory events at telomeric DNA

Replicative senescence is an essential cellular process playing important physiological functions, but it is better known for its implications in aging, cancer, and other pathologies. One of the main triggers of replicative senescence is telomere shortening and/or its dysfunction and, therefore, a deep understanding of the molecular determinants is crucial. However, replicative senescence is a heterogeneous and hard to study process, especially in mammalian cells, and some important questions still need an answer. These questions concern i) the exact molecular causes triggering replicative senescence, ii) the role of DNA repair mechanisms and iii) the importance of R-loops at telomeres in regulating senescence onset, and iv) the mechanisms underlying the bypass of replicative senescence. In this review, we will report and discuss recent findings about these mechanisms both in mammalian cells and in the model organism Saccharomyces cerevisiae.

Cell Survival, Death, and Proliferation in Senescent and Cancer Cells: the Role of (Poly)phenols

Cellular senescence has long been considered a permanent state of cell cycle arrest occurring in proliferating cells subject to different stressors, used as a cellular defense mechanism from acquiring potentially harmful genetic faults. However, recent studies highlight that senescent cells might also alter the local tissue environment and concur to chronic inflammation and cancer risk by secreting inflammatory and matrix remodeling factors, acquiring a senescence-associated secretory phenotype (SASP). Indeed, during aging and age-related diseases, senescent cells amass in mammalian tissues, likely contributing to the inevitable loss of tissue function as we age. Cellular senescence has thus become one potential target to tackle age-associated diseases as well as cancer development. One important aspect characterizing senescent cells is their telomere length. Telomeres shorten as a consequence of multiple cellular replications, gradually leading to permanent cell cycle arrest, known as replicative senescence. Interestingly, in the large majority of cancer cells, a senescence escape strategy is used and telomere length is maintained by telomerase, thus favoring cancer initiation and tumor survival. There is growing evidence showing how (poly)phenols can impact telomere maintenance through different molecular mechanisms depending on dose and cell phenotypes. Although normally, (poly)phenols maintain telomere length and support telomerase activity, in cancer cells this activity is negatively modulated, thus accelerating telomere attrition and promoting cancer cell death. Some (poly)phenols have also been shown to exert senolytic activity, thus suggesting both antiaging (directly eliminating senescent cells) and anticancer (indirectly, via SASP inhibition) potentials. In this review, we analyze selective (poly)phenol mechanisms in senescent and cancer cells to discriminate between in vitro and in vivo evidence and human applications considering (poly)phenol bioavailability, the influence of the gut microbiota, and their dose-response effects.

Association of Longer Leukocyte Telomere Length With Cardiac Size, Function, and Heart Failure

Importance

Longer leukocyte telomere length (LTL) is associated with a lower risk of adverse cardiovascular outcomes. The extent to which variation in LTL is associated with intermediary cardiovascular phenotypes is unclear.

Objective

To evaluate the associations between LTL and a diverse set of cardiovascular imaging phenotypes.

Design, Setting, and Participants

This is a population-based cross-sectional study of UK Biobank participants recruited from 2006 to 2010. LTL was measured using a quantitative polymerase chain reaction method. Cardiovascular measurements were derived from cardiovascular magnetic resonance using machine learning. The median (IQR) duration of follow-up was 12.0 (11.3-12.7) years. The associations of LTL with imaging measurements and incident heart failure (HF) were evaluated by multivariable regression models. Genetic associations between LTL and significantly associated traits were investigated by mendelian randomization. Data were analyzed from January to May 2023.

Exposure

LTL.

Main Outcomes and Measures

Cardiovascular imaging traits and HF.

Results

Of 40 459 included participants, 19 529 (48.3%) were men, and the mean (SD) age was 55.1 (7.6) years. Longer LTL was independently associated with a pattern of positive cardiac remodeling (higher left ventricular mass, larger global ventricular size and volume, and higher ventricular and atrial stroke volumes) and a lower risk of incident HF (LTL fourth quartile vs first quartile: hazard ratio, 0.86; 95% CI, 0.81-0.91; P = 1.8 × 10-6). Mendelian randomization analysis suggested a potential causal association between LTL and left ventricular mass, global ventricular volume, and left ventricular stroke volume.

Conclusions and Relevance

In this cross-sectional study, longer LTL was associated with a larger heart with better cardiac function in middle age, which could potentially explain the observed lower risk of incident HF.

TERRA beyond cancer: the biology of telomeric repeat-containing RNAs in somatic and germ cells

The telomeric noncoding RNA TERRA is a key component of telomeres and it is widely expressed in normal as well as cancer cells. In the last 15 years, several publications have shed light on the role of TERRA in telomere homeostasis and cell survival in cancer cells. However, only few studies have investigated the regulation or the functions of TERRA in normal tissues. A better understanding of the biology of TERRA in non-cancer cells may provide unexpected insights into how these lncRNAs are transcribed and operate in cells, and their potential role in physiological processes, such as aging, age-related pathologies, inflammatory processes and human genetic diseases. In this review we aim to discuss the findings that have advanced our understanding of the biology of TERRA using non-cancer mammalian cells as a model system.

GWAS-identified telomere length associated genetic variants predict risk of recurrence of HPV-positive oropharyngeal cancer after definitive radiotherapy

BACKGROUND

Lymphocyte telomere length (LTL)-related genetic variants may modulate LTL and affect recurrence of squamous cell carcinoma of the oropharynx (SCCOP).

METHODS

A total of 1013 patients with incident SCCOP were recruited and genotyped for 16 genome-wide association study (GWAS)-identified TL-related polymorphisms. Of these patients, 489 had tumour HPV16 status determination. Univariate and multivariate analyses were performed to evaluate associations.

FINDINGS

Of the 16 TL-related polymorphisms, four were significantly associated with LTL: rs1920116, rs3027234, rs6772228, and rs11125529, and the patients with putatively favourable genotypes had approximately 1.5-3 times the likelihood of shorter LTL compared with patients with the corresponding risk genotypes. Moreover, patients with one to four favourable genotypes of the four combined polymorphisms had approximately 3-11 times the likelihood of shorter LTL compared with patients with no favourable genotype. The four LTL-related polymorphisms were significantly associated with approximately 40% reduced risk (for favourable genotypes) or doubled risk (for risk genotypes) of recurrence, and similar but more pronounced associations were observed in patients with tumour HPV16-positive SCCOP. Similarly, patients with one to four risk genotypes had significantly approximately 2.5-4 times increased recurrence risk compared with patients with no risk genotype, and similar but more pronounced associations were observed in patients with tumour HPV16-positive SCCOP.

INTERPRETATION

Four LTL-related polymorphisms individually or jointly modify LTL and risk of recurrence of SCCOP, particularly HPV-positive SCCOP. These LTL-related polymorphisms could have potential to further stratify patients with HPV-positive SCCOP for individualized treatment and better survival.

FUNDING

Not applicable.

Distinct senescence mechanisms restrain progression of dysplastic nevi

TERT promoter mutations (TPMs) are frequently found in different cancer types, including approximately 70% of sun-exposed skin melanomas. In melanoma, TPMs are among the earliest mutations and can be present during the transition from nevus to melanoma. However, the specific factors that contribute to the selection of TPMs in certain nevi subsets are not well understood. To investigate this, we analyzed a group of dysplastic nevi (DN) by sequencing genes commonly mutated in melanocytic neoplasms. We examined the relationship between the identified mutations, patient age, telomere length, histological features, and the expression of p16. Our findings reveal that TPMs are more prevalent in DN from older patients and are associated with shorter telomeres. Importantly, these TPMs were not found in nevi with BRAF V600E mutations. Conversely, DN with BRAF V600E mutations were observed in younger patients, had longer telomeres, and a higher proportion of p16-positive cells. This suggests that these nevi arrest growth independently of telomere shortening through a mechanism known as oncogene-induced senescence (OIS). These characteristics extend to melanoma sequencing data sets, where melanomas with BRAF V600E mutations were more likely to have CDKN2A inactivation, overriding OIS. In contrast, melanomas without BRAF V600E mutations showed a higher frequency of TPMs. Our data imply that TPMs are selected to bypass replicative senescence (RS) in cells that were not arrested by OIS. Overall, our results indicate that a subset of melanocytic neoplasms face constraints from RS, while others encounter OIS and RS. The order in which these barriers are overcome during progression to melanoma depends on the mutational context.

Telomere Length in Human Spermatogenic Cells as a New Potential Predictor of Clinical Outcomes in ART Treatment with Intracytoplasmic Injection of Testicular Spermatozoa

Predicting the clinical outcomes of intracytoplasmic sperm injection (ICSI) cycles that use the testicular spermatozoa of azoospermic patients presents a challenge. Thus, the development of additional approaches to assessing the competence of a testicular-sperm-derived embryo without causing damage to gametes or the embryo is necessary. One of the key parameters in determining such developmental competence is telomere length (TL). We aimed to analyze TLs in spermatogenic cells from the testicular biopsy samples of azoospermic patients and determine how this parameter influences embryo competence for pre- and post-implantation development. Using Q-FISH, we studied the TL of the chromosomes in spermatogonia and spermatocytes I from the TESE biopsy samples of 30 azoospermic patients. An increase in TL was detected during the differentiation from spermatogonia to spermatocytes I. The patients' testicular spermatozoa were used in 37 ICSI cycles that resulted in 22 embryo transfers. Nine pregnancies resulted, of which, one was ectopic and eight ended in birth. The analysis of embryological outcomes revealed a dependence between embryo competence for development to the blastocyst stage and the TL in spermatogenic cells. The TLs in spermatogonia and spermatocytes I in the testicular biopsy samples were found to be higher in patients whose testicular sperm ICSI cycles resulted in a birth. Therefore, the length of telomeres in spermatogenic cells can be considered as a potential prognostic criterion in assessing the competence of testicular-sperm-derived embryos for pre- and post-implantation development. The results of this study provide the basis for the development of a laboratory test for the prediction of testicular sperm ICSI cycle outcomes.

Insulin-like growth factor binding protein-3 induces senescence by inhibiting telomerase activity in MCF-7 breast cancer cells

Insulin-like growth factor binding protein-3 (IGFBP-3) has been known to inhibit cell proliferation and exert tumor-suppressing effects depending on the cell type. In this study, we aimed to show that IGFBP-3 induces cellular senescence via suppression of the telomerase activity, thereby inhibiting MCF-7 breast cancer cell proliferation. We found that the induction of IGFBP-3 in MCF-7 cells enhanced the loss of cell viability. Flow cytometry revealed a higher percentage of non-cycling cells among IGFBP-3-expressing cells than among controls. IGFBP-3 induction also resulted in morphological alterations, such as a flattened cytoplasm and increased granularity, suggesting that IGFBP-3 induces a senescence-like phenotype. The percentage of IGFBP-3 expressing cells with senescence-associated β-galactosidase activity was 3.4 times higher than control cells. Telomeric repeat amplification and real-time PCR showed that IGFBP-3 decreased telomerase activity by reducing the levels of the RNA component (hTR) and catalytic protein component with reverse transcriptase activity (hTERT) of telomerase in a dose-dependent manner. These results suggest that IGFBP-3 is a negative regulator of MCF-7 breast cancer cell growth by inducing senescence through telomerase suppression.

Senescence-related impairment of autophagy induces toxic intraneuronal amyloid-β accumulation in a mouse model of amyloid pathology

Aging is the main risk factor for Alzheimer's disease (AD) and other neurodegenerative pathologies, but the molecular and cellular changes underlying pathological aging of the nervous system are poorly understood. AD pathology seems to correlate with the appearance of cells that become senescent due to the progressive accumulation of cellular insults causing DNA damage. Senescence has also been shown to reduce the autophagic flux, a mechanism involved in clearing damaged proteins from the cell, and such impairment has been linked to AD pathogenesis. In this study, we investigated the role of cellular senescence on AD pathology by crossing a mouse model of AD-like amyloid-β (Aβ) pathology (5xFAD) with a mouse model of senescence that is genetically deficient for the RNA component of the telomerase (Terc^-/-). We studied changes in amyloid pathology, neurodegeneration, and the autophagy process in brain tissue samples and primary cultures derived from these mice by complementary biochemical and immunostaining approaches. Postmortem human brain samples were also processed to evaluate autophagy defects in AD patients. Our results show that accelerated senescence produces an early accumulation of intraneuronal Aβ in the subiculum and cortical layer V of 5xFAD mice. This correlates with a reduction in amyloid plaques and Aβ levels in connecting brain regions at a later disease stage. Neuronal loss was specifically observed in brain regions presenting intraneuronal Aβ and was linked to telomere attrition. Our results indicate that senescence affects intraneuronal Aβ accumulation by impairing autophagy function and that early autophagy defects can be found in the brains of AD patients. Together, these findings demonstrate the instrumental role of senescence in intraneuronal Aβ accumulation, which represents a key event in AD pathophysiology, and emphasize the correlation between the initial stages of amyloid pathology and defects in the autophagy flux.

Mono-(2-ethylhexyl) Phthalate (MEHP)-Induced Telomere Structure and Function Disorder Mediates Cell Cycle Dysregulation and Apoptosis via c-Myc and Its Upstream Transcription Factors in a Mouse Spermatogonia-Derived (GC-1) Cell Line

As a typical environmental endocrine disrupting chemical (EDC), di-(2-ethylhexyl) phthalate (DEHP) is thought to be related to reproductive disorders, especially in males. Growing evidence suggests that various EDCs may result in an impaired telomere structure and function, which is associated with male infertility. However, the adverse effect of DEHP on telomeres in male reproductive cells has rarely been studied, and the related mechanisms remain unclear. In this study, we tested the effects of mono-(2-ethylhexyl) phthalate (MEHP), the primary metabolite of DEHP, on telomere dysfunction in mouse spermatogonia-derived cells (GC-1) and the potential role of TERT and c-Myc in MEHP-induced spermatogenic cell damage. Results showed that MEHP induced cell viability inhibition, G₀/G₁ phase cell cycle arrest, and apoptosis in GC-1 cells in a dose-dependent manner. Shortened telomeres, reduced telomerase activity, and decreased expression of TERT, c-Myc, and upstream transcription factors of c-Myc were also observed in the MEHP-treated cells. In conclusion, it can be concluded that TERT-mediated telomere dysfunction may contribute to MEHP-induced G₀/G₁ phase cell cycle arrest and apoptosis in GC-1 cells through the impairment of c-Myc and its upstream transcription factors.

Critically short telomeres derepress retrotransposons to promote genome instability in embryonic stem cells

Telomeres, at the ends of chromosomes, protect chromosomes from fusion and preserve genomic stability. However, the molecular mechanisms underlying telomere attrition-induced genome instability remain to be understood. We systematically analyzed the expression of retrotransposons and performed genomic sequencing of different cell and tissue types with telomeres of varying lengths due to telomerase deficiency. We found that critically short telomeres altered retrotransposon activity to promote genomic instability in mouse embryonic stem cells, as evidenced by elevated numbers of single nucleotide variants, indels and copy number variations (CNVs). Transpositions of retrotransposons such as LINE1 resulting from the short telomeres can also be found in these genomes with elevated number of mutations and CNVs. Retrotransposon activation is linked to increased chromatin accessibility, and reduced heterochromatin abundance correlates with short telomeres. Re-elongation of telomeres upon recovery of telomerase partly represses retrotransposons and heterochromatin accumulation. Together, our findings suggest a potential mechanism by which telomeres maintain genomic stability by suppressing chromatin accessibility and retrotransposon activity.

T cell immune deficiency rather than chromosome instability predisposes patients with short telomere syndromes to squamous cancers

Patients with short telomere syndromes (STS) are predisposed to developing cancer, believed to stem from chromosome instability in neoplastic cells. We tested this hypothesis in a large cohort assembled over the last 20 years. We found that the only solid cancers to which patients with STS are predisposed are squamous cell carcinomas of the head and neck, anus, or skin, a spectrum reminiscent of cancers seen in patients with immunodeficiency. Whole-genome sequencing showed no increase in chromosome instability, such as translocations or chromothripsis. Moreover, STS-associated cancers acquired telomere maintenance mechanisms, including telomerase reverse transcriptase (TERT) promoter mutations. A detailed study of the immune status of patients with STS revealed a striking T cell immunodeficiency at the time of cancer diagnosis. A similar immunodeficiency that impaired tumor surveillance was documented in mice with short telomeres. We conclude that STS patients’ predisposition to solid cancers is due to T cell exhaustion rather than autonomous defects in the neoplastic cells themselves.

Potent telomerase activators from a novel sapogenin via biotransformation utilizing Camarosporium laburnicola, an endophytic fungus

BACKGROUND

Cycloartane-type triterpenoids possess important biological activities, including immunostimulant, wound healing, and telomerase activation. Biotransformation is one of the derivatization strategies of natural products to improve their bioactivities. Endophytic fungi have attracted attention in biotransformation studies because of their ability to perform modifications in complex structures with a high degree of stereospecificity.

RESULTS

This study focuses on biotransformation studies on cyclocephagenol (1), a novel cycloartane-type sapogenin from Astragalus species, and its 12-hydroxy derivatives (2 and 3) to obtain new telomerase activators. Since the hTERT protein levels of cyclocephagenol (1) and its 12-hydroxy derivatives (2 and 3) on HEKn cells were found to be notable, biotransformation studies were carried out on cyclocephagenol and its 12-hydroxy derivatives using Camarosporium laburnicola, an endophytic fungus isolated from Astragalus angustifolius. Later, immunoblotting and PCR-based ELISA assay were used to screen starting compounds and biotransformation products for their effects on hTERT protein levels and telomerase activation. All compounds showed improved telomerase activation compared to the control group.

CONCLUSIONS

As a result of biotransformation studies, seven new metabolites were obtained and characterized, verifying the potential of C. laburnicola as a biocatalyst. Additionally, the bioactivity results showed that this endophytic biocatalyst is unique in transforming the metabolites of its host to afford potent telomerase activators.

Telomerase RNA plays a major role in the completion of the life cycle in Ustilago maydis and shares conserved domains with other Ustilaginales

The RNA subunit of telomerase is an essential component whose primary sequence and length are poorly conserved among eukaryotic organisms. The phytopathogen Ustilago maydis is a dimorphic fungus of the order Ustilaginales. We analyzed several species of Ustilaginales to computationally identify the TElomere RNA (TER) gene ter1. To confirm the identity of the TER gene, we disrupted the gene and characterized telomerase-negative mutants. Similar to catalytic TERT mutants, ter1Δ mutants exhibit phenotypes of growth delay, telomere shortening and low replicative potential. ter1-disrupted mutants were unable to infect maize seedlings in heterozygous crosses and showed defects such as cell cycle arrest and segregation failure. We concluded that ter1, which encodes the TER subunit of the telomerase of U. maydis, have similar and perhaps more extensive functions than trt1.

Close Ties between the Nuclear Envelope and Mammalian Telomeres: Give Me Shelter

The nuclear envelope (NE) in eukaryotic cells is essential to provide a protective compartment for the genome. Beside its role in connecting the nucleus with the cytoplasm, the NE has numerous important functions including chromatin organization, DNA replication and repair. NE alterations have been linked to different human diseases, such as laminopathies, and are a hallmark of cancer cells. Telomeres, the ends of eukaryotic chromosomes, are crucial for preserving genome stability. Their maintenance involves specific telomeric proteins, repair proteins and several additional factors, including NE proteins. Links between telomere maintenance and the NE have been well established in yeast, in which telomere tethering to the NE is critical for their preservation and beyond. For a long time, in mammalian cells, except during meiosis, telomeres were thought to be randomly localized throughout the nucleus, but recent advances have uncovered close ties between mammalian telomeres and the NE that play important roles for maintaining genome integrity. In this review, we will summarize these connections, with a special focus on telomere dynamics and the nuclear lamina, one of the main NE components, and discuss the evolutionary conservation of these mechanisms.

Telomere length and brain imaging phenotypes in UK Biobank

Telomeres form protective caps at the ends of chromosomes, and their attrition is a marker of biological aging. Short telomeres are associated with an increased risk of neurological and psychiatric disorders including dementia. The mechanism underlying this risk is unclear, and may involve brain structure and function. However, the relationship between telomere length and neuroimaging markers is poorly characterized. Here we show that leucocyte telomere length (LTL) is associated with multi-modal MRI phenotypes in 31,661 UK Biobank participants. Longer LTL is associated with: i) larger global and subcortical grey matter volumes including the hippocampus, ii) lower T1-weighted grey-white tissue contrast in sensory cortices, iii) white-matter microstructure measures in corpus callosum and association fibres, iv) lower volume of white matter hyperintensities, and v) lower basal ganglia iron. Longer LTL was protective against certain related clinical manifestations, namely all-cause dementia (HR 0.93, 95% CI: 0.91-0.96), but not stroke or Parkinson's disease. LTL is associated with multiple MRI endophenotypes of neurodegenerative disease, suggesting a pathway by which longer LTL may confer protective against dementia.

Functional T cells are capable of supernumerary cell division and longevity

Differentiated somatic mammalian cells putatively exhibit species-specific division limits that impede cancer but may constrain lifespans^1-3. To provide immunity, transiently stimulated CD8⁺ T cells undergo unusually rapid bursts of numerous cell divisions, and then form quiescent long-lived memory cells that remain poised to reproliferate following subsequent immunological challenges. Here we addressed whether T cells are intrinsically constrained by chronological or cell-division limits. We activated mouse T cells in vivo using acute heterologous prime-boost-boost vaccinations⁴, transferred expanded cells to new mice, and then repeated this process iteratively. Over 10 years (greatly exceeding the mouse lifespan)⁵ and 51 successive immunizations, T cells remained competent to respond to vaccination. Cells required sufficient rest between stimulation events. Despite demonstrating the potential to expand the starting population at least 10⁴⁰-fold, cells did not show loss of proliferation control and results were not due to contamination with young cells. Persistent stimulation by chronic infections or cancer can cause T cell proliferative senescence, functional exhaustion and death⁶. We found that although iterative acute stimulations also induced sustained expression and epigenetic remodelling of common exhaustion markers (including PD1, which is also known as PDCD1, and TOX) in the cells, they could still proliferate, execute antimicrobial functions and form quiescent memory cells. These observations provide a model to better understand memory cell differentiation, exhaustion, cancer and ageing, and show that functionally competent T cells can retain the potential for extraordinary population expansion and longevity well beyond their organismal lifespan.

High-throughput telomere length measurement at nucleotide resolution using the PacBio high fidelity sequencing platform

Telomeres are specialized nucleoprotein structures at the ends of linear chromosomes. The progressive shortening of steady-state telomere length in normal human somatic cells is a promising biomarker for age-associated diseases. However, there remain substantial challenges in quantifying telomere length due to the lack of high-throughput method with nucleotide resolution for individual telomere. Here, we describe a workflow to capture telomeres using newly designed telobaits in human culture cell lines as well as clinical patient samples and measure their length accurately at nucleotide resolution using single-molecule real-time (SMRT) sequencing. Our results also reveal the extreme heterogeneity of telomeric variant sequences (TVSs) that are dispersed throughout the telomere repeat region. The presence of TVSs disrupts the continuity of the canonical (5'-TTAGGG-3')n telomere repeats, which affects the binding of shelterin complexes at the chromosomal ends and telomere protection. These findings may have profound implications in human aging and diseases.

Targeting the "hallmarks of aging" to slow aging and treat age-related disease: fact or fiction?

Aging is a major risk factor for a number of chronic diseases, including neurodegenerative and cerebrovascular disorders. Aging processes have therefore been discussed as potential targets for the development of novel and broadly effective preventatives or therapeutics for age-related diseases, including those affecting the brain. Mechanisms thought to contribute to aging have been summarized under the term the "hallmarks of aging" and include a loss of proteostasis, mitochondrial dysfunction, altered nutrient sensing, telomere attrition, genomic instability, cellular senescence, stem cell exhaustion, epigenetic alterations and altered intercellular communication. We here examine key claims about the "hallmarks of aging". Our analysis reveals important weaknesses that preclude strong and definitive conclusions concerning a possible role of these processes in shaping organismal aging rate. Significant ambiguity arises from the overreliance on lifespan as a proxy marker for aging, the use of models with unclear relevance for organismal aging, and the use of study designs that do not allow to properly estimate intervention effects on aging rate. We also discuss future research directions that should be taken to clarify if and to what extent putative aging regulators do in fact interact with aging. These include multidimensional analytical frameworks as well as designs that facilitate the proper assessment of intervention effects on aging rate.

Characteristics of salivary telomere length shortening in preterm infants

OBJECTIVE

To examine the association between gestational age, telomere length (TL) and rate of shortening in newborns.

STUDY DESIGN

Genomic DNA was isolated from buccal samples of 39 term infants at birth and one year and 32 preterm infants at birth, term-adjusted age (40 weeks post-conception) and age one-year corrected for gestational duration. Telomere length was measured by quantitative real-time PCR. Demographic and clinical data were collected during clinic or research visits and from hospital records. Socioeconomic status was estimated using the deprivation category (DEPCAT) scores derived from the Carstairs score of the subject's postal code.

RESULTS

At birth, preterm infants had longer telomeres than infants born at term. However, there was no difference in telomere length between preterm infants and term infants at one year of age, implying that the rate of telomere shortening was greater in pre-term than term infants. Interestingly, TL at age 40 weeks post-conception in preterm infants was significantly longer than term infant TL at birth, suggesting that time since conception is not the only factor that affects rate of shortening. Several factors, including sex, fetal growth restriction, maternal age, maternal booking body mass index (BMI), mother education level and DEPCAT score, also differed between the preterm and term groups.

CONCLUSIONS

Preterm infants have longer telomeres than term infants at birth. In the studied cohort, the rate of telomere shortening was greater in the premature group compared with the term infants. This finding agrees with previous studies using cord blood, suggesting that the longer TL in premature infants detected at birth do not persist and demonstrating that use of saliva DNA is acceptable for studies of telomere dynamics in infants. However, that the TL at age 40 weeks post-conception in preterm is longer than term infants at birth suggests that biological factors other than time since conception also affect rate of shortening.

DNA Damage Response-Associated Cell Cycle Re-Entry and Neuronal Senescence in Brain Aging and Alzheimer's Disease

Chronological aging is by far the strongest risk factor for age-related dementia and Alzheimer's disease. Senescent cells accumulated in the aging and Alzheimer's disease brains are now recognized as the keys to describing such an association. Cellular senescence is a classic phenomenon characterized by stable cell arrest, which is thought to be applicable only to dividing cells. Emerging evidence indicates that fully differentiated post-mitotic neurons are also capable of becoming senescent, with roles in contributing to both brain aging and disease pathogenesis. The key question that arises is the identity of the upstream triggers and the molecular mechanisms that underly such changes. Here, we highlight the potential role of persistent DNA damage response as the major driver of senescent phenotypes and discuss the current evidence and molecular mechanisms that connect DNA repair infidelity, cell cycle re-entry and terminal fate decision in committing neuronal cell senescence.

Accelerated ageing is associated with increased COVID-19 severity and differences across ethnic groups may exist

Background

While increased age is an established risk factor for COVID-19, there is great heterogeneity in outcomes within age groups. This is because chronological age does not reflect health, unlike biological age. We intend to investigate the association between accelerated ageing and COVID-19 outcomes through the lens of three measures, namely phenotypic age acceleration (PhenoAgeAccel), telomere length (Adjusted T/S Ratio) and facial ageing, and to examine whether there are differences across ethnic groups.

Methods

Taking participants from the UK Biobank, we associated accelerated ageing with severe COVID-19 outcomes, defined as COVID-related hospitalisation or death. Separate logistic regressions models were created for age and the three accelerated ageing-related variables, adjusting for a variety of covariates in each model. Multivariable logistic regression models were also created within White, Black, Asian and Other ethnic groups to assess for potential differing associations. Forward likelihood ratio logistic regression models were created to evaluate importance of the variables and to assess for patterns of association across the total population and ethnic groups.

Results

After adjusting for all covariates, the odds ratio (OR) and 95% confidence interval (95% CI) of COVID-19 severe outcomes for age was 1.080 (1.074-1.086). After further adjusting age for the accelerated ageing variables, the ORs were 1.029 (1.020-1.039) for PhenoAgeAccel and 0.847 (0.772-0.929) for Facial Ageing's "Younger Than You Are" while Adjusted T/S ratio and "Older Than You Are" were statistically insignificant. The OR for age remained similar across ethnic groups. Both PhenoAgeAccel and younger facial ages in the White population and PhenoAgeAccel in the Black population had ORs of 1.031 (1.021-1.042), 0.853 (0.774-0.939), and 1.049 (1.001-1.100), respectively. Both Adjusted T/S Ratio and older facial ages showed statistical insignificance in all ethnicities. In forward logistic regression, age and PhenoAgeAccel were the age-related variables selected most frequently in all models.

Interpretation

Accelerated ageing is associated with increased COVID-19 severity. The mechanisms at work here are likely immunosenescence and inflamaging. This association indicates that anti-ageing treatment may improve COVID-19 outcome. The results within ethnic groups and that of telomere length were inconclusive, but point to a need for future, more focused research on the topic.

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.

Transmissible cancer and longitudinal telomere dynamics in Tasmanian devils (Sarcophilus harrisii)

A plethora of intrinsic and environmental factors have been shown to influence the length of telomeres, the protector of chromosome ends. Despite the growing interest in infection-telomere interactions, there is very limited knowledge on how transmissible cancers influence telomere maintenance. An emblematic example of transmissible cancer occurs in the Tasmanian devil (Sarcophilus harrisii), whose populations have been dramatically reduced by infectious cancer cells. To investigate associations between telomere dynamics and the transmissible cancer, we used longitudinal data from a Tasmanian devil population that has been exposed to the disease for over 15 years. We detected substantial temporal variation in individual telomere length (TL), and a positive significant association between TL and age, as well as a marginally significant trend for devils with devil facial tumour disease (DFTD) having longer telomeres. A proportional hazard analysis yielded no significant effect of TL on the development of DFTD. Like previous studies, we show the complexity that TL dynamics may exhibit across the lifetime of organisms. Our work highlights the importance of long-term longitudinal sampling for understanding the effects of wildlife diseases on TL.

In Vitro Determination of the Skin Anti-Aging Potential of Four-Component Plant-Based Ingredient

The beauty industry is actively searching for solutions to prevent skin aging. Some of the crucial elements protecting cells from the aging process are telomere shortening, telomerase expression, cell senescence, and homeostasis of the redox system. Modification of these factors using natural antioxidants is an appealing way to support healthy skin aging. Therefore, in this study, we sought to investigate the antiaging efficacy of a specific combination of four botanical extracts (pomegranate, sweet orange, Cistanche and Centella asiatica) with proven antioxidant properties. To this end, normal human dermal fibroblasts were used as a cell model and the following studies were performed: cell proliferation was established by means of the MTT assay and the intracellular ROS levels in stress-induced premature senescence fibroblasts; telomere length measurement was performed under standard cell culture conditions using qPCR and under oxidative stress conditions using a variation of the Q-FISH technique; telomerase activity was examined by means of Q-TRAP; and AGE quantification was completed by means of ELISA assay in UV-irradiated fibroblasts. As a result, the botanical blend significantly reversed the H2O2-induced decrease in cell viability and reduced H2O2-induced ROS. Additionally, the presence of the botanical ingredient reduced the telomere shortening rate in both stressed and non-stressed replicating fibroblasts, and under oxidative stress conditions, the fibroblasts presented a higher median and 20th percentile telomere length, as well as a lower percentage of short telomeres (<3 Kbp) compared with untreated fibroblasts. Furthermore, the ingredient transiently increased relative telomerase activity after 24 h and prevented the accumulation of UVR-induced glycated species. The results support the potential use of this four-component plant-based ingredient as an antiaging agent.