Explore the vast range of titles available.

Senescence is a cell fate that contributes to multiple aging-related pathologies. Despite profound age-associated changes in skeletal muscle (SkM), whether its constituent cells are prone to senesce has not been methodically examined. Herein, using single cell and bulk RNA-sequencing and complementary imaging methods on SkM of young and old mice, we demonstrate that a subpopulation of old fibroadipogenic progenitors highly expresses together with multiple senescence-related genes and, concomitantly, exhibits DNA damage and chromatin reorganization. Through analysis of isolated myofibers, we also detail a senescence phenotype within a subset of old cells, governed instead by . Administration of a senotherapeutic intervention to old mice countered age-related molecular and morphological changes and improved SkM strength. Finally, we found that the senescence phenotype is conserved in SkM from older humans. Collectively, our data provide compelling evidence for cellular senescence as a hallmark and potentially tractable mediator of SkM aging.

Background Cellular senescence is a cell fate in response to diverse forms of age-related damage and stress that has been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). The associations between circulating levels of candidate senescence biomarkers and disease outcomes have not been specifically studied in IPF. In this study we assessed the circulating levels of candidate senescence biomarkers in individuals affected by IPF and controls and evaluated their ability to predict disease outcomes. Methods We measured the plasma concentrations of 32 proteins associated with senescence in Lung Tissue Research Consortium participants and studied their relationship with the diagnosis of IPF, parameters of pulmonary and physical function, health-related quality of life, mortality, and lung tissue expression of P16 , a prototypical marker of cellular senescence. A machine learning approach was used to evaluate the ability of combinatorial biomarker signatures to predict disease outcomes. Results The circulating levels of several senescence biomarkers were significantly elevated in persons affected by IPF compared to controls. A subset of biomarkers accurately classified participants as having or not having the disease and was significantly correlated with measures of pulmonary function, health-related quality of life and, to an extent, physical function. An exploratory analysis revealed senescence biomarkers were also associated with mortality in IPF participants. Finally, the plasma concentrations of several biomarkers were associated with their expression levels in lung tissue as well as the expression of P16 . Conclusions Our results suggest that circulating levels of candidate senescence biomarkers are informative of disease status, pulmonary and physical function, and health-related quality of life. Additional studies are needed to validate the combinatorial biomarkers signatures that emerged using a machine learning approach.

A diversity of factors influence student mental health, arguing for the importance of longitudinal monitoring of, and accountability for, student mental health at graduate institutions.

Produced by senescent cells, the senescence-associated secretory phenotype (SASP) is a potential driver of age-related dysfunction. We tested whether circulating concentrations of SASP proteins reflect age and medical risk in humans. We first screened senescent endothelial cells, fibroblasts, preadipocytes, epithelial cells, and myoblasts to identify candidates for human profiling. We then tested associations between circulating SASP proteins and clinical data from individuals throughout the life span and older adults undergoing surgery for prevalent but distinct age-related diseases. A community-based sample of people aged 20-90 years (retrospective cross-sectional) was studied to test associations between circulating SASP factors and chronological age. A subset of this cohort aged 60-90 years and separate cohorts of older adults undergoing surgery for severe aortic stenosis (prospective longitudinal) or ovarian cancer (prospective case-control) were studied to assess relationships between circulating concentrations of SASP proteins and biological age (determined by the accumulation of age-related health deficits) and/or postsurgical outcomes. We showed that SASP proteins were positively associated with age, frailty, and adverse postsurgery outcomes. A panel of 7 SASP factors composed of growth differentiation factor 15 (GDF15), TNF receptor superfamily member 6 (FAS), osteopontin (OPN), TNF receptor 1 (TNFR1), ACTIVIN A, chemokine (C-C motif) ligand 3 (CCL3), and IL-15 predicted adverse events markedly better than a single SASP protein or age. Our findings suggest that the circulating SASP may serve as a clinically useful candidate biomarker of age-related health and a powerful tool for interventional human studies.

ABSTRACT Cellular senescence is an irreversible form of cell‐cycle arrest caused by excessive stress or damage. While various biomarkers of cellular senescence have been proposed, there are currently no universal, stand‐alone indicators of this condition. The field largely relies on the combined detection of multiple biomarkers to differentiate senescent cells from non‐senescent cells. Here we introduce a new approach: unbiased cell culture selections to identify senescent cell‐specific folded DNA aptamers from vast libraries of trillions of random 80‐mer DNAs. Senescent mouse adult fibroblasts and their non‐senescent counterparts were employed for selection. We demonstrate aptamer specificity for senescent mouse cells in culture, identify a form of fibronectin as the molecular target of two selected aptamers, show increased aptamer staining in naturally aged mouse tissues, and demonstrate decreased aptamer staining when p16 expressing cells are removed in a transgenic INK‐ATTAC mouse model. This work demonstrates the value of unbiased cell‐based selections to identify new senescence‐specific DNA reagents. Pearson et al. report the selection of DNA aptamers against senescent mouse cells, demonstrating broad binding specificity for multiple senescent mouse cell types and induction methods. Two of the aptamers bind a form of fibronectin with sub‐nanomolar affinity even in complex protein mixtures. One aptamer detects age‐ and senescence‐associated changes in mouse lung tissue, highlighting the ability of DNA aptamer selection against a senescence phenotype to generate powerful new reagents with the potential to detect or target senescent cells.

Age is the primary risk factor for most chronic diseases in developed countries, including cancer, diabetes, neurodegeneration, and cardiovascular disease. Over the past century, there has been an unprecedented rise in human life expectancy. In 1900 only 3.1 million people in the US were aged 65 and older, but that number increased to 55.8 million people in 2020. While this change reflects technological and medical advancements which promote longevity, population aging poses new challenges. In light of population aging and the strong association between aging and chronic disease, there is substantial interest in understanding fundamental molecular mechanisms of aging to guide the development and implementation of interventions.The purpose of this dissertation is to evaluate two fundamental hallmarks of aging, cellular senescence and circadian dysregulation. Hallmarks of aging are distinct, but also interrelated and by studying the interplay between senescence and circadian rhythms in the context of aging, we provide novel insight into these fundamental mechanisms of aging.In Chapter 2, I describe the investigation of BMAL1, a pioneer transcription factor and master regulator of the molecular circadian clock, and its role in the senescence program. We demonstrate that BMAL1 is significantly upregulated in senescent cells and has altered rhythmicity compared to non-senescent cells. Through BMAL1-ChIP-seq, we show that BMAL1 is uniquely localized to genomic motifs associated with AP-1 in senescent cells. Integration of BMAL1-ChIP-seq data with RNA-seq revealed that BMAL1 presence at AP-1 motifs is associated with active transcription. Finally, we showed that BMAL1 contributes to AP-1 transcriptional control of key features of the senescence program, including altered regulation of cell survival pathways, and confers resistance to drug-induced apoptosis. Overall, these results highlight a previously unappreciated role of the core circadian clock component BMAL1 on the molecular phenotype of senescent cells.In Chapter 3, I describe a study which was designed to evaluate the impacts of a circadian rhythmicity-directed, late-life endurance exercise intervention in both male and female aged mice. We measured improvements in several readouts of late-life health, including improved physical and metabolic performance in exercised mice compared to matched sedentary control mice, and note substantial sex-based differences in these measures. Ongoing molecular analyses of exercised and sedentary aged mice will continue to explore the potential for circadian rhythmicity-directed exercise as a scalable intervention to modulate aging.Given the importance of senescent cells in contributing to tissue function and disease in aging, and the fact that there is no one standalone marker for senescent cells, in Chapter 4, we sought to characterize the senescence-associated secretory phenotype unique to different senescent cells. Through multiplexed proteomic identification of secreted factors, we demonstrate significant cell-type specific differences. This work also showed the potential for these factors to be used as a non-invasive readout of senescent cell burden in clinical population, and as biomarkers for clinically relevant health outcomes.Expanding on the challenge of identification of senescent cells, in Chapter 5, we utilize a new approach: unbiased cell culture selections to identify senescent cell-specific folded DNA aptamers from vast libraries of trillions of random DNAs. Through this approach, we identified candidate DNA aptamers which bind with high specificity to senescent cells over non-senescent control cells and have begun validation of molecular targets of these candidates. This proof-of-concept study supports the potential for DNA aptamer technology in selective labeling and biomarker discovery in the context of senescence.Together, this thesis provides insight into aspects of cellular senescence, circadian rhythmicity, and aging. Integration of in vitro studies of senescence and circadian rhythmicity, with in vivo studies in an aging context will provide further insight into how these different systems interact and drive the biology of aging. The growing concern of population aging has resulted in substantial demand for basic and clinical research that will facilitate targeting of fundamental mechanisms of aging, and in this dissertation, we sought to expand upon existing work on the interplay between cellular senescence and circadian rhythmicity in the context of aging.

Cellular senescence is an irreversible form of cell-cycle arrest caused by excessive stress or damage. While various biomarkers of cellular senescence have been proposed, there are currently no universal, stand-alone indicators of this condition. The field largely relies on the combined detection of multiple biomarkers to differentiate senescent cells from non-senescent cells. Here we introduce a new approach: unbiased cell culture selections to identify senescent cell-specific folded DNA aptamers from vast libraries of trillions of random 80-mer DNAs. Senescent mouse adult fibroblasts and their non-senescent counterparts were employed for selection. We demonstrate aptamer specificity for senescent mouse cells in culture, identify a form of fibronectin as the molecular target of two selected aptamers, show increased aptamer staining in naturally aged mouse tissues, and demonstrate decreased aptamer staining when p16 expressing cells are removed in a transgenic mouse model. This work demonstrates the value of unbiased cell-based selections to identify new senescence-specific DNA reagents.

Abstract Cellular senescence is a state of stable growth arrest in response to stress, which is a fundamental process of biological aging. They secrete products, the Senescence-Associated Secretory Phenotype (SASP), which consists of inflammatory cytokines, chemokines, growth factors and matrix remodeling proteins. Senescent cells accumulate with advancing age and partial elimination of senescent cells can reverse age-related dysfunction and increase mean lifespan in mice. However, it is not clear whether components of the SASP can be measured in human plasma and serve as aging biomarkers. Here we generated a candidate panel of senescence markers based on a multiplexed bead-based assay of proteins secreted by senescent preadipocytes, endothelial cells, fibroblasts, myoblasts, preadipocytes, and epithelial cells compared to non-senescent controls. The SASP undoubtedly varies by cell type; however, we observed that multiple components of the SASP are conserved. We then assessed circulating SASP components in human plasma samples from Mayo Clinic Biobank participants (n=280, 20 male and 20 female per decade, age 20-90) using the same method. We confirmed that components of the SASP can be quantified in human plasma with the multiplexed bead-based assay and observed several SASP components robustly increase with chronological age in humans. Our study illustrates that senescence-associated secretome components are detectable in human plasma and could potentially serve as biomarkers of systemic aging and senescent cell burden.

Endosomal Sorting Complexes Required for Transport (ESCRTs) drive reverse topology membrane remodeling events including the formation of intralumenal vesicles within multivesicular bodies, the budding of retroviruses from the plasma membrane, and the scission of the cytokinetic bridge. It has been difficult to study the physiological relevance of this machinery in mammals because many contributing components are essential for viability. To bypass this problem we used combinations of knockout (−), hypomorphic (H) and wildtype (+) alleles to generate a series of mice with a gradual reduction of HD-PTP (product of PTPN23), an ESCRT-associated protein known to cause embryonic lethality when fully depleted. Whereas PTPN23-/H mice died shortly after birth, PTPN23H/H mice developed into adulthood but had reduced size, lipodystrophy, and shortened lifespan. Analysis of 14-day inguinal adipose tissue indicated reduced expression of adipogenesis markers, and PTPN23 knockout preadipocytes similarly display reduced adipogenesis in vitro. Defects in insulin-stimulated signaling were apparent in differentiated PTPN23 knockout adipocytes and PTPN23H/H inguinal adipose tissue in vitro, correlating with reduced levels of insulin signaling hallmarks observed in adult PTPN23H/H inguinal adipose tissue in vivo. Whereas the ESCRT machinery have been suggested to downregulate signaling, these results indicate that HD-PTP promotes insulin-induced signaling in, as well as differentiation of, inguinal adipose tissue. These results revealed unexpected roles for HD-PTP in promoting fat accumulation in mammalian cells through supporting insulin signaling, adipogenesis, and lipid droplet formation.