Apoptotic stress causes mtDNA release during senescence and drives the SASP.

Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP)1. Mitochondria are major regulators of the SASP; however, the underlying mechanisms have not been elucidated2. Mitochondria are often essential for apoptosis, a cell fate distinct from cellular senescence. During apoptosis, widespread mitochondrial outer membrane permeabilization (MOMP) commits a cell to die3. Here we find that MOMP occurring in a subset of mitochondria is a feature of cellular senescence. This process, called minority MOMP (miMOMP), requires BAX and BAK macropores enabling the release of mitochondrial DNA (mtDNA) into the cytosol. Cytosolic mtDNA in turn activates the cGAS-STING pathway, a major regulator of the SASP. We find that inhibition of MOMP in vivo decreases inflammatory markers and improves healthspan in aged mice. Our results reveal that apoptosis and senescence are regulated by similar mitochondria-dependent mechanisms and that sublethal mitochondrial apoptotic stress is a major driver of the SASP. We provide proof-of-concept that inhibition of miMOMP-induced inflammation may be a therapeutic route to improve healthspan.

Senolytic Drugs: Reducing Senescent Cell Viability to Extend Health Span.

Senescence is the consequence of a signaling mechanism activated in stressed cells to prevent proliferation of cells with damage. Senescent cells (Sncs) often develop a senescence-associated secretory phenotype to prompt immune clearance, which drives chronic sterile inflammation and plays a causal role in aging and age-related diseases. Sncs accumulate with age and at anatomical sites of disease. Thus, they are regarded as a logical therapeutic target. Senotherapeutics are a new class of drugs that selectively kill Sncs (senolytics) or suppress their disease-causing phenotypes (senomorphics/senostatics). Since 2015, several senolytics went from identification to clinical trial. Preclinical data indicate that senolytics alleviate disease in numerous organs, improve physical function and resilience, and suppress all causes of mortality, even if administered to the aged. Here, we review the evidence that Sncs drive aging and disease, the approaches to identify and optimize senotherapeutics, and the current status of preclinical and clinical testing of senolytics.

Single-cell Mayo Map (scMayoMap): an easy-to-use tool for cell type annotation in single-cell RNA-sequencing data analysis.

BACKGROUND: Single-cell RNA-sequencing (scRNA-seq) has become a widely used tool for both basic and translational biomedical research. In scRNA-seq data analysis, cell type annotation is an essential but challenging step. In the past few years, several annotation tools have been developed. These methods require either labeled training/reference datasets, which are not always available, or a list of predefined cell subset markers, which are subject to biases. Thus, a user-friendly and precise annotation tool is still critically needed. RESULTS: We curated a comprehensive cell marker database named scMayoMapDatabase and developed a companion R package scMayoMap, an easy-to-use single-cell annotation tool, to provide fast and accurate cell type annotation. The effectiveness of scMayoMap was demonstrated in 48 independent scRNA-seq datasets across different platforms and tissues. Additionally, the scMayoMapDatabase can be integrated with other tools and further improve their performance. CONCLUSIONS: scMayoMap and scMayoMapDatabase will help investigators to define the cell types in their scRNA-seq data in a streamlined and user-friendly way.

Length-independent telomere damage drives post-mitotic cardiomyocyte senescence.

Ageing is the biggest risk factor for cardiovascular disease. Cellular senescence, a process driven in part by telomere shortening, has been implicated in age-related tissue dysfunction. Here, we address the question of how senescence is induced in rarely dividing/post-mitotic cardiomyocytes and investigate whether clearance of senescent cells attenuates age-related cardiac dysfunction. During ageing, human and murine cardiomyocytes acquire a senescent-like phenotype characterised by persistent DNA damage at telomere regions that can be driven by mitochondrial dysfunction and crucially can occur independently of cell division and telomere length. Length-independent telomere damage in cardiomyocytes activates the classical senescence-inducing pathways, p21CIP and p16INK4a, and results in a non-canonical senescence-associated secretory phenotype, which is pro-fibrotic and pro-hypertrophic. Pharmacological or genetic clearance of senescent cells in mice alleviates detrimental features of cardiac ageing, including myocardial hypertrophy and fibrosis. Our data describe a mechanism by which senescence can occur and contribute to age-related myocardial dysfunction and in the wider setting to ageing in post-mitotic tissues.

Biomarkers of cellular senescence in idiopathic pulmonary fibrosis.

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.

Scientific opportunities in resilience research for cardiovascular health and wellness. Report from a National Heart, Lung, and Blood Institute workshop.

Exposure of biological systems to acute or chronic insults triggers a host of molecular and physiological responses to either tolerate, adapt, or fully restore homeostasis; these responses constitute the hallmarks of resilience. Given the many facets, dimensions, and discipline-specific focus, gaining a shared understanding of "resilience" has been identified as a priority for supporting advances in cardiovascular health. This report is based on the working definition: "Resilience is the ability of living systems to successfully maintain or return to homeostasis in response to physical, molecular, individual, social, societal, or environmental stressors or challenges," developed after considering many factors contributing to cardiovascular resilience through deliberations of multidisciplinary experts convened by the National Heart, Lung, and Blood Institute during a workshop entitled: "Enhancing Resilience for Cardiovascular Health and Wellness." Some of the main emerging themes that support the possibility of enhancing resilience for cardiovascular health include optimal energy management and substrate diversity, a robust immune system that safeguards tissue homeostasis, and social and community support. The report also highlights existing research challenges, along with immediate and long-term opportunities for resilience research. Certain immediate opportunities identified are based on leveraging existing high-dimensional data from longitudinal clinical studies to identify vascular resilience measures, create a 'resilience index,' and adopt a life-course approach. Long-term opportunities include developing quantitative cell/organ/system/community models to identify resilience factors and mechanisms at these various levels, designing experimental and clinical interventions that specifically assess resilience, adopting global sharing of resilience-related data, and cross-domain training of next-generation researchers in this field.

Factors Associated With Physical Activity Levels in Patients With Breast Cancer.

Physical activity (PA) is associated with improvement in breast cancer treatment-related symptoms and survival, yet most breast cancer survivors do not meet national PA guidelines. This study aimed to identify characteristics of participants that were associated with an increased likelihood of meeting PA guidelines. Adults with breast cancer seen at Mayo Clinic (Rochester, MN) were surveyed regarding their PA participation, and those who self-reported at least 150 minutes of moderate and/or strenuous aerobic PA weekly on average were considered to be "meeting guidelines". Three thousand participants returned PA data. Younger age, completion of the survey 7-12 years after diagnosis, absence of recurrence, no bilateral mastectomy, absence of metastatic disease, and lower BMI at the time of survey completion were associated with PA participation (P < .05 in univariate and multivariate analyses). Findings were similar when a threshold of 90 minutes was applied. These results may inform the development of targeted PA-facilitating interventions.

Exercise Counters the Age-Related Accumulation of Senescent Cells.

We propose the beneficial effects of exercise are in part mediated through the prevention and elimination of senescent cells. Exercise counters multiple forms of age-related molecular damage that initiate the senescence program and activates immune cells responsible for senescent cell clearance. Preclinical and clinical evidence for exercise as a senescence-targeting therapy and areas needing further investigation are discussed.

Quality is more important than quantity: pre-operative sarcopenia is associated with poor survival in advanced ovarian cancer.

BACKGROUND: Sarcopenia is prevalent among older patients with cancer and is associated with poor outcomes. OBJECTIVE: To explore the relationship between muscle mass, quality, and patient age with overall survival after surgery for advanced ovarian cancer. METHODS: Patients with advanced stage (IIIC/IV) ovarian cancer who underwent primary cytoreductive surgery between January 2006 and July 2016 were included. Body composition measures were calculated from pre-operative CT imaging: skeletal muscle index (skeletal muscle index=skeletal muscle area normalized for height), skeletal muscle density, and skeletal muscle gauge (product of skeletal muscle index and skeletal muscle density). Each measure was transformed to a z-score and evaluated for association with risk of death using Cox proportional hazards models. Recursive partitioning was used to classify patients into homogeneous subgroups considering age and skeletal muscle gauge as predictors of overall survival. RESULTS: The study included 429 patients (mean age 64.2 years). Increased age moderately correlated with decreased skeletal muscle gauge (r=-0.45). Decreasing skeletal muscle density and skeletal muscle gauge were significantly associated with increased risk of death; HR (95% CI) per 1-unit decrease in z-score of 1.24 (1.10 to 1.39) for skeletal muscle density and 1.27 (1.12 to 1.44) for skeletal muscle gauge. Associations were diluted after adjusting for age (1.13 (1.00 to 1.29) skeletal muscle density and 1.14 (0.99 to 1.30) skeletal muscle gauge). Recursive partitioning identified three subgroups: <60 years old, ≥60 years old with skeletal muscle gauge ≥937.3, and ≥60 years old with skeletal muscle gauge <937.3; median overall survival was 5.8, 3.3, and 2.3 years, respectively (p<0.001). CONCLUSIONS: Skeletal muscle gauge, a novel sarcopenia measure incorporating quantity and quality, was associated with poorer survival in patients with advanced ovarian cancer, particularly among patients older than 60. Expanding our knowledge of how sarcopenia relates to solid tumor outcomes among high-risk patients can modify our treatment approach.

Dietary carbohydrates modulate metabolic and ß-cell adaptation to high-fat diet-induced obesity.

Obesity is associated with several chronic comorbidities, one of which is type 2 diabetes mellitus (T2DM). The pathogenesis of obesity and T2DM is influenced by alterations in diet macronutrient composition, which regulate energy expenditure, metabolic function, glucose homeostasis, and pancreatic islet cell biology. Recent studies suggest that increased intake of dietary carbohydrates plays a previously underappreciated role in the promotion of obesity and consequent metabolic dysfunction. Thus, in this study, we utilized mouse models to test the hypothesis that dietary carbohydrates modulate energetic, metabolic, and islet adaptions to high-fat diets. To address this, we exposed C57BL/6J mice to 12 wk of 3 eucaloric high-fat diets (>60% calories from fat) with varying total carbohydrate (1-20%) and sucrose (0-20%) content. Our results show that severe restriction of dietary carbohydrates characteristic of ketogenic diets reduces body fat accumulation, enhances energy expenditure, and reduces prevailing glycemia and insulin resistance compared with carbohydrate-rich, high-fat diets. Moreover, severe restriction of dietary carbohydrates also results in functional, morphological, and molecular changes in pancreatic islets highlighted by restricted capacity for ß-cell mass expansion and alterations in insulin secretory response. These studies support the hypothesis that low-carbohydrate/high-fat diets provide antiobesogenic benefits and suggest further evaluation of the effects of these diets on ß-cell biology in humans.

A Western diet impairs CNS energy homeostasis and recovery after spinal cord injury: Link to astrocyte metabolism.

A diet high in fat and sucrose (HFHS), the so-called Western diet promotes metabolic syndrome, a significant co-morbidity for individuals with spinal cord injury (SCI). Here we demonstrate that the spinal cord of mice consuming HFHS expresses reduced insulin-like growth factor 1 (IGF-1) and its receptor and shows impaired tricarboxylic acid cycle function, reductions in PLP and increases in astrogliosis, all prior to SCI. After SCI, Western diet impaired sensorimotor and bladder recovery, increased microgliosis, exacerbated oligodendrocyte loss and reduced axon sprouting. Direct and indirect neural injury mechanisms are suggested since HFHS culture conditions drove parallel injury responses directly and indirectly after culture with conditioned media from HFHS-treated astrocytes. In each case, injury mechanisms included reductions in IGF-1R, SIRT1 and PGC-1α and were prevented by metformin. Results highlight the potential for a Western diet to evoke signs of neural insulin resistance and injury and metformin as a strategy to improve mechanisms of neural neuroprotection and repair.

Knockout of sulfatase 2 is associated with decreased steatohepatitis and fibrosis in a mouse model of nonalcoholic fatty liver disease.

Sulfatase 2 (SULF2) is a heparan sulfate editing enzyme that regulates the milieu of growth factors and cytokines involved in a variety of cellular processes. We used a murine model of diet-induced steatohepatitis to assess the effect of SULF2 downregulation on the development of nonalcoholic steatohepatitis (NASH) and liver fibrosis. Wild-type B6;129 mice (WT) and Sulf2-knockout B6;129P2-SULF2Gt(PST111)Byg mice (Sulf2-KO) were fed a fast-food diet (FFD) rich in saturated fats, cholesterol, and fructose or a standard chow diet (SC) ad libitum for 9 mo. WT mice on FFD showed a threefold increase in hepatic Sulf2 mRNA expression, and a 2.2-fold increase in hepatic SULF2 protein expression compared with WT mice on SC. Knockout of Sulf2 led to a significant decrease in diet-mediated weight gain and dyslipidemia compared with WT mice on FFD. Knockout of Sulf2 also abrogated diet-induced steatohepatitis and hepatic fibrosis compared with WT mice on FFD. Furthermore, expression levels of the profibrogenic receptors TGFßR2 and PDGFRß were significantly decreased in Sulf2-KO mice compared with WT mice on FFD. Together, our data suggest that knockout of Sulf2 significantly downregulates dyslipidemia, steatohepatitis, and hepatic fibrosis in a diet-induced mouse model of NAFLD, suggesting that targeting of SULF2 signaling may be a potential therapeutic mechanism in NASH.NEW & NOTEWORTHY We report for the first time that in wild-type (WT) mice, fast-food diet (FFD) induced a threefold increase in hepatic Sulf2 mRNA and a 2.2-fold increase in sulfatase 2 (SULF2) protein expression compared with WT mice on standard chow diet (SC). We showed that knockout of SULF2 ameliorates FFD-induced obesity, hyperlipidemia, steatohepatitis, and fibrosis. These data, along with work from other laboratories, suggest that SULF2 may be critical to the ability of the liver to progress to nonalcoholic steatohepatitis and fibrosis in conditions of overnutrition.

Frailty is a determinant of suboptimal chemotherapy in women with advanced ovarian cancer.

OBJECTIVE: To evaluate the relationship between frailty and chemotherapy delivery among women with epithelial ovarian cancer (EOC). METHODS: We included women who underwent primary debulking surgery (PDS) for stage IIIC/IV EOC between 1/2/2003 and 12/30/2011, received adjuvant chemotherapy at our institution, and had data available to calculate a frailty deficit index. Frailty was defined as a frailty deficit index ≥0.15. Relative dose intensity (RDI) of chemotherapy was calculated as the percentage of the standard dose that was administered, and compared between frail and non-frail using the Wilcoxon rank-sum test. RESULTS: Failure to receive chemotherapy following PDS was twice as common among frail vs. non-frail women (26.7% vs 14.2%, p = 0.001). Of the 169 women who received chemotherapy at our institution, 17.2% (29/169) were frail. Frail women were older (mean, 67.9 vs 62.3 years, p = 0.01), had higher BMI (mean, 29.6 vs 25.7 kg/m2, p = 0.003), and were less likely to complete 6 cycles of chemotherapy (75.9 vs. 93.6%, p = 0.008). Using an RDI cutoff of 85%, frail women were less likely to have adequate doses of carboplatin (15.8 vs. 66.2%, p < 0.001) and paclitaxel (57.9 vs. 80.5%, p = 0.07) despite no differences in dose delays (34.5 vs. 42.1%), dose reductions (65.5 vs. 68.6%), and severe neutropenia (44.8 vs. 39.3%). After adjusting for age, frailty was associated with shorter progression-free (HR 1.58, 95% CI: 0.99-2.50) and overall survival (HR 2.14, 95% CI: 1.35-3.41). CONCLUSION: Frail women with EOC were less likely to receive chemotherapy or the optimal dose of chemotherapy after PDS despite no evidence of treatment-related toxicity. Frail EOC patients demonstrated shorter progression-free and overall survival. Further studies are needed to explore the association between frailty, chemotherapy, and survival.

Loss of Ovarian Hormones and Accelerated Somatic and Mental Aging.

Bilateral oophorectomy in premenopausal women is a unique condition causing the abrupt and premature loss of ovarian hormones, primarily estrogen. Bilateral oophorectomy causes an alteration of several fundamental aging processes at the cellular, tissue, organ, and system levels, leading to multimorbidity, frailty, and reduced survival. However, many questions remain unanswered.

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

PURPOSE OF THE REVIEW: Senescent cells have the capacity to both effect and limit fibrosis. Senotherapeutics target senescent cells to improve aging conditions. Here, we review the contexts in which senescent cells mediate wound healing and fibrotic pathology and the potential utility of senotherapeutic drugs for treatment of fibrotic disease. RECENT FINDINGS: Multi-action and temporal considerations influence deleterious versus beneficial actions of senescent cells. Acutely generated senescent cells can limit proliferation, and the senescence-associated secretory phenotype (SASP) contains factors that can facilitate tissue repair. Long-lived senescent cells that evade clearance or are generated outside of programmed remodeling can deplete the progenitor pool to exhaust regenerative capacity and through the SASP, stimulate continual activation, leading to disorganized tissue architecture, fibrotic damage, sterile inflammation, and induction of bystander senescence. Senescent cells contribute to fibrotic pathogenesis in multiple tissues, including the liver, kidney, and lung. Senotherapeutics may be a viable strategy for treatment of a range of fibrotic conditions.

JAK inhibition alleviates the cellular senescence-associated secretory phenotype and frailty in old age.

Chronic, low grade, sterile inflammation frequently accompanies aging and age-related diseases. Cellular senescence is associated with the production of proinflammatory chemokines, cytokines, and extracellular matrix (ECM) remodeling proteases, which comprise the senescence-associated secretory phenotype (SASP). We found a higher burden of senescent cells in adipose tissue with aging. Senescent human primary preadipocytes as well as human umbilical vein endothelial cells (HUVECs) developed a SASP that could be suppressed by targeting the JAK pathway using RNAi or JAK inhibitors. Conditioned medium (CM) from senescent human preadipocytes induced macrophage migration in vitro and inflammation in healthy adipose tissue and preadipocytes. When the senescent cells from which CM was derived had been treated with JAK inhibitors, the resulting CM was much less proinflammatory. The administration of JAK inhibitor to aged mice for 10 wk alleviated both adipose tissue and systemic inflammation and enhanced physical function. Our findings are consistent with a possible contribution of senescent cells and the SASP to age-related inflammation and frailty. We speculate that SASP inhibition by JAK inhibitors may contribute to alleviating frailty. Targeting the JAK pathway holds promise for treating age-related dysfunction.

Functional not chronologic age: Frailty index predicts outcomes in advanced ovarian cancer.

OBJECTIVES: To assess the impact of frailty as measured by a frailty deficit index (FI) on outcomes in advanced epithelial ovarian cancer (EOC) after primary debulking surgery (PDS). METHODS: Women with Stage IIIC/IV EOC who underwent PDS between 1/1/2003-12/31/2011 were included. Medical records were reviewed for patient characteristics and outcomes. The FI includes 30 items scored at 0, 0.5 or 1 and is calculated by summing across all the item scores and dividing by the total. Frailty was defined as a FI ≥0.15. Associations were assessed using logistic regression and Cox proportional hazards regression. RESULTS: Of the 535 studied, 78% had stage IIIC disease and mean (SD) age was 64.3 (11.3) years. Median FI was 0.08, and 131 patients (24.5%) were considered frail with FI ≥0.15. Compared to non-frail patients, frail patients were more likely to have an Accordion grade 3+ complication (28.2 vs. 18.8%; odds ratio (OR): 1.70, 95% CI: 1.08-2.68) and more likely to die within 90days of surgery (16.0 vs. 5.2%; OR: 3.48, 95% CI: 1.83-6.61). After adjusting for known risk factors, these associations remained significant, adjusted OR (aOR): 1.62, 95% CI: 1.00-2.62; aOR: 2.60, 95% CI 1.32-5.10; and aOR: 0.57, 95% CI 0.34-0.97, respectively. Overall survival (OS) for the entire cohort was 39.6months (m). OS was shorter in the frail versus non-frail (median 26.5 vs 44.9m, p<0.001). Frailty was independently associated with death (adjusted hazard ratio: 1.52, 95% CI: 1.21-1.92) after adjusting for known risk factors. CONCLUSIONS: Frailty is a common finding in patients with EOC and is independently associated with worse surgical outcomes and poorer OS. Routine assessments of frailty can be incorporated into patient counseling and decision-making for the EOC patient beyond simple reliance on single factors such as age.

Relationship between pre-transplant physical function and outcomes after kidney transplant.

BACKGROUND: Performance-based measures of physical function predict morbidity following non-transplant surgery. Study objectives were to determine whether physical function predicts outcomes after kidney transplant and assess how physical function changes post-transplant. METHODS: We conducted a prospective study involving living donor kidney transplants recipients at our center from May 2012 to February 2014. Physical function was measured using the Short Physical Performance Battery (SPPB [balance, chair stands, gait speed]) and grip strength testing. Initial length of stay (LOS), 30- day rehospitalizations, allograft function, and quality of life (QOL) were assessed. RESULTS: The majority of the 140 patients in our cohort had excellent pre-transplant physical function. In general, balance scores were more predictive of post-transplant outcomes than the SPPB. Decreased pre-transplant balance was independently associated with longer LOS and increased rehospitalizations but not with post-transplant QOL; 35% of patients experienced a clinically meaningful (≥ 1.0 m/s) improvement in gait speed 4 months post-transplant. CONCLUSIONS: Decreased physical function may be associated with longer LOS and rehospitalizations following kidney transplant. Further studies are needed to confirm this association. The lack of relationship between pre-transplant gait speed and outcomes in our cohort may represent a ceiling effect. More comprehensive measures, including balance testing, may be required for risk stratification.

Clearance of p16Ink4a-positive senescent cells delays ageing-associated disorders.

Advanced age is the main risk factor for most chronic diseases and functional deficits in humans, but the fundamental mechanisms that drive ageing remain largely unknown, impeding the development of interventions that might delay or prevent age-related disorders and maximize healthy lifespan. Cellular senescence, which halts the proliferation of damaged or dysfunctional cells, is an important mechanism to constrain the malignant progression of tumour cells. Senescent cells accumulate in various tissues and organs with ageing and have been hypothesized to disrupt tissue structure and function because of the components they secrete. However, whether senescent cells are causally implicated in age-related dysfunction and whether their removal is beneficial has remained unknown. To address these fundamental questions, we made use of a biomarker for senescence, p16(Ink4a), to design a novel transgene, INK-ATTAC, for inducible elimination of p16(Ink4a)-positive senescent cells upon administration of a drug. Here we show that in the BubR1 progeroid mouse background, INK-ATTAC removes p16(Ink4a)-positive senescent cells upon drug treatment. In tissues--such as adipose tissue, skeletal muscle and eye--in which p16(Ink4a) contributes to the acquisition of age-related pathologies, life-long removal of p16(Ink4a)-expressing cells delayed onset of these phenotypes. Furthermore, late-life clearance attenuated progression of already established age-related disorders. These data indicate that cellular senescence is causally implicated in generating age-related phenotypes and that removal of senescent cells can prevent or delay tissue dysfunction and extend healthspan.