Tchkonia, T

ABSTRACT Biological aging greatly impacts the body’s ability to handle glucose, and represents a major risk factor the development and progression of type 2 diabetes (T2D). Nonetheless, despite advances in cellular senescence research and the development of new senolytic therapies, the heterogeneity of cellular senescence in the human endocrine pancreas, as well as its roles in normal aging, remains to be elucidated at the single-cell level. Here, we performed single-cell–resolved spatial proteomics and transcriptomics on intact pancreas from 26 donors (ages 20–80) and multiplexed single-cell RNA sequencing and functional assays on dispersed islets from 14 donors (ages 34–69). We identify two discrete SnC subpopulations distinguished by relative expression of CDKN1A and CDKN2A. CDKN1A ⁺ senescent cells (SnCs) exhibit loss of β-cell identity, impaired insulin secretion, and a proinflammatory SASP associated with increased islet immune infiltration. In contrast, CDKN2A ⁺ SnCs retain transcriptional identity and functional competence, with lower inflammatory signaling. Together, these findings identify heterogeneous and functionally divergent senotypes in the human pancreas, distinguishing an adaptive ( CDKN2A ⁺) from a maladaptive ( CDKN1A ⁺) senescence program, thus providing a mechanism-guided framework for senescence-targeted therapies in T2D.

Key Points This study reveals the temporal development and progression of senescence in an arteriovenous fistula of uremic mice. Senescent genes including p21 increased 7 days after arteriovenous fistula placement, and p16 and phosphorylated p53 cells accumulate between days 14 and 28. Transcriptomic analyses confirm established genes in arteriovenous fistula failure and suggest a collection of novel genes of interest. Background Hemodialysis therapy for ESKD requires suitable vascular access, most commonly the arteriovenous fistula (AVF). Forty percent of AVFs fail within 1 year, leading to morbidity and care costs. Failure mechanisms remain unclear, and current therapies are inadequate. Cellular senescence may be critical in AVF failure, and ESKD itself may accelerate senescence and subsequent vascular dysfunction. Senescence follows AVF placement in rodents with normal kidney function, but the temporal and spatial features in uremic conditions are unknown. This study aimed to characterize AVF changes in uremic mice over time and versus control vessels. Methods Six- to eight-week-old male C57BL6/J mice underwent five/six nephrectomy. Twenty-eight days later, an AVF was created by cuff anastomosis (right carotid artery to the right jugular vein). Transcriptomic analysis was performed 7 days post-AVF, and further samples were collected at 14 and 28 days post-AVF creation for histologic assessment. Results AVF outflow vein morphometry showed reduced neointimal cell density. Whole transcriptomic analysis of outflow versus control veins at 7 days post-AVF placement revealed 1187 upregulated and 3256 downregulated genes. Differentially expressed genes were significantly enriched in two established senescence-related gene sets, SenMayo (a curated panel of approximately 125 genes validated across species to capture senescence and associated proteins) and SenSig (a broader panel assessed to represent fibrotic and stress-induced cell response). Histologically, senescence markers p16, p21, and phospho53 increased between days 14 and 28. Genes common to our dataset, SenMayo, and SenSig were validated with quantitative reverse transcription PCR. Conclusions These data support established markers of AVF failure, such as matrix-metalloproteinases and monocyte chemokines, and identify potential novel modulators of AVF survival that may inform senolytic strategies to improve patency. In summary, this study reveals for the first time the chronologic progression of vascular senescence in the AVF of uremic mice.

Abstract Multiple changes occur in hormonal regulation with aging and across various endocrine organs. These changes are associated with multiple age-related disorders and diseases. A better understanding of responsible underling biological mechanisms could help in the management of multiple endocrine disorders over and above hormone replacement therapy (HRT). Cellular senescence is involved in multiple biological aging processes and pathologies common in elderly individuals. Cellular senescence, which occurs in many older individuals but also across the lifespan in association with tissue damage, acute and chronic diseases, certain drugs, and genetic syndromes, may contribute to such endocrine disorders as osteoporosis, metabolic syndrome, and type 2 diabetes mellitus. Drugs that selectively induce senescent cell removal, “senolytics,”, and drugs that attenuate the tissue-destructive secretory state of certain senescent cells, “senomorphics,” appear to delay the onset of or alleviate multiple diseases, including but not limited to endocrine disorders such as diabetes, complications of obesity, age-related osteoporosis, and cancers as well as atherosclerosis, chronic kidney disease, neurodegenerative disorders, and many others. More than 30 clinical trials of senolytic and senomorphic agents have already been completed, are underway, or are planned for a variety of indications. Targeting senescent cells is a novel strategy that is distinct from conventional therapies such as HRT, and thus might address unmet medical needs and can potentially amplify effects of established endocrine drug regimens, perhaps allowing for dose decreases and reducing side effects.

AbstractObjectiveThe aim of this study was to determine the effect of age of obesity onset on senescence‐related markers in abdominal (AB) and femoral (FEM) subcutaneous adipose tissue (SAT) before and after moderate (~10%) weight loss.MethodsAB and FEM SAT were collected from human females with childhood‐onset obesity (CO) or adult‐onset obesity (AO) before and after diet‐ and exercise‐induced weight loss. Immunofluorescence analysis of γH2AX/RAD51 (DNA damage/repair markers) and p53/p21 (senescence markers) was conducted in cultured preadipocytes, and senescence‐associated β‐galactosidase (SA‐β‐gal) activity was measured in SAT.ResultsCO had proportionately more AB and FEM preadipocytes with DNA damage (γH2AX+) and senescence markers (p53+ and/or p21+) than AO at baseline. The proportion of γH2AX+ FEM preadipocytes declined with weight loss in CO and was similar between groups after weight loss. The number of γH2AX foci in γH2AX+ preadipocytes decreased similarly between groups and regions with weight loss in parallel with an increase in RAD51. The proportion of p53+ and p21+ preadipocytes and SA‐β‐gal+ cells in SAT did not change with weight loss, but the total p21 intensity in p53+/p21+ FEM preadipocytes declined in AO.ConclusionsThese results provide preliminary evidence that females with CO have an accelerated preadipocyte aging state that improves with weight loss in terms of DNA damage but not senescence.

Abstract Cellular senescence has been identified as a pathological mechanism linked to tau and amyloid beta (Aβ) accumulation in mouse models of Alzheimer's disease (AD). Clearance of senescent cells using the senolytic compounds dasatinib (D) and quercetin (Q) reduced neuropathological burden and improved clinically relevant outcomes in the mice. Herein, we conducted a vanguard open-label clinical trial of senolytic therapy for AD with the primary aim of evaluating central nervous system (CNS) penetrance, as well as exploratory data collection relevant to safety, feasibility, and efficacy. Participants with early-stage symptomatic AD were enrolled in an open-label, 12-week pilot study of intermittent orally-delivered D+Q. CNS penetrance was assessed by evaluating drug levels in cerebrospinal fluid (CSF) using high performance liquid chromatography with tandem mass spectrometry. Safety was continuously monitored with adverse event reporting, vitals, and laboratory work. Cognition, neuroimaging, and plasma and CSF biomarkers were assessed at baseline and post-treatment. Five participants (mean age: 76±5 years; 40% female) completed the trial. The treatment increased D and Q levels in the blood of all participants ranging from 12.7 to 73.5 ng/ml for D and 3.29-26.30 ng/ml for Q. D levels were detected in the CSF of four participants ranging from 0.281 to 0.536 ng/ml (t(4)=3.123, p=0.035); Q was not detected. Treatment was well-tolerated with no early discontinuation and six mild to moderate adverse events occurring across the study. Cognitive and neuroimaging endpoints did not significantly differ from baseline to post-treatment. CNS levels of IL-6 and GFAP increased from baseline to post-treatment (t(4)=3.913, p=008 and t(4)=3.354, p=0.028, respectively) concomitant with decreased levels of several cytokines and chemokines associated with senescence, and a trend toward higher levels of Aβ42 (t(4)=-2.338, p=0.079). Collectively the data indicate the CNS penetrance of D and provide preliminary support for the safety, tolerability, and feasibility of the intervention and suggest that astrocytes and Aβ may be particularly responsive to the treatment. While early results are promising, fully powered, placebo-controlled studies are needed to evaluate the potential of AD modification with the novel approach of targeting cellular senescence.

Senescent cells exacerbate COVID-19 Cellular senescence is a state elicited in response to stress signals and is associated with a damaging secretory phenotype. The number of senescent cells increases with advanced age and this in turn drives age-related diseases. Camell et al. show that senescent cells have an amplified inflammatory response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (see the Perspective by Cox and Lord). This response is communicated to nonsenescent cells, suppressing viral defense mechanisms and increasing the expression of viral entry proteins. In old mice infected with a SARS-CoV-2–related virus, treatment with senolytics to reduce the senolytic cell burden reduced mortality and increased antiviral antibodies. Science , abe4832, this issue p. eabe4832 ; see also abi4474, p. 281

Abstract The elderly population is increasing faster than other segments of the population throughout the world. Age is the leading predictor for most chronic diseases and disorders, multimorbidity, geriatric syndromes, and impaired ability to recover from accidents or illnesses. Enhancing the duration of health and independence, termed healthspan, would be more desirable than extending lifespan merely by prolonging the period of morbidity toward the end of life. The geroscience hypothesis posits that healthspan can be extended by targeting fundamental aging mechanisms, rather than attempting to address each age-related disease one at a time, only so the afflicted individual survives disabled and dies shortly afterward of another age-related disease. These fundamental aging mechanisms include, among others, chronic inflammation, fibrosis, stem cell/ progenitor dysfunction, DNA damage, epigenetic changes, metabolic shifts, destructive metabolite generation, mitochondrial dysfunction, misfolded or aggregated protein accumulation, and cellular senescence. These processes appear to be tightly interlinked, as targeting any one appears to affect many of the rest, underlying our Unitary Theory of Fundamental Aging Mechanisms. Interventions targeting many fundamental aging processes are being developed, including dietary manipulations, metformin, mTOR (mechanistic target of rapamycin) inhibitors, and senolytics, which are in early human trials. These interventions could lead to greater healthspan benefits than treating age-related diseases one at a time. To illustrate these points, we focus on cellular senescence and therapies in development to target senescent cells. Combining interventions targeting aging mechanisms with disease-specific drugs could result in more than additive benefits for currently difficult-to-treat or intractable diseases. More research attention needs to be devoted to targeting fundamental aging processes.

Abstract Senolytics are a class of drugs that selectively clear senescent cells (SC). The first senolytic drugs Dasatinib, Quercetin, Fisetin and Navitoclax were discovered using a hypothesis‐driven approach. SC accumulate with ageing and at causal sites of multiple chronic disorders, including diseases accounting for the bulk of morbidity, mortality and health expenditures. The most deleterious SC are resistant to apoptosis and have up‐regulation of anti‐apoptotic pathways which defend SC against their own inflammatory senescence‐associated secretory phenotype (SASP), allowing them to survive, despite killing neighbouring cells. Senolytics transiently disable these SCAPs, causing apoptosis of those SC with a tissue‐destructive SASP. Because SC take weeks to reaccumulate, senolytics can be administered intermittently – a ‘hit‐and‐run’ approach. In preclinical models, senolytics delay, prevent or alleviate frailty, cancers and cardiovascular, neuropsychiatric, liver, kidney, musculoskeletal, lung, eye, haematological, metabolic and skin disorders as well as complications of organ transplantation, radiation and cancer treatment. As anticipated for agents targeting the fundamental ageing mechanisms that are ‘root cause’ contributors to multiple disorders, potential uses of senolytics are protean, potentially alleviating over 40 conditions in preclinical studies, opening a new route for treating age‐related dysfunction and diseases. Early pilot trials of senolytics suggest they decrease senescent cells, reduce inflammation and alleviate frailty in humans. Clinical trials for diabetes, idiopathic pulmonary fibrosis, Alzheimer’s disease, COVID‐19, osteoarthritis, osteoporosis, eye diseases and bone marrow transplant and childhood cancer survivors are underway or beginning. Until such studies are done, it is too early for senolytics to be used outside of clinical trials.

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