Clinicopathological and cellular senescence biomarkers in chronic stalled wounds.

BACKGROUND: Chronic wounds have been associated with an elevated burden of cellular senescence, a state of essentially irreversible cell cycle arrest, resistance to apoptosis, and a secretory phenotype. However, whether senescent cells contribute to wound chronicity in humans remains unclear. The objective of this article is to assess the role of clinicopathological characteristics and cellular senescence in the time-to-healing of chronic wounds. METHODS: A cohort of 79 patients with chronic wounds was evaluated in a single-center academic practice from February 1, 2005, to February 28, 2015, and followed for up to 36 months. Clinical characteristics and wound biopsies were obtained at baseline, and time-to-healing was assessed. Wound biopsies were analyzed histologically for pathological characteristics and molecularly for markers of cellular senescence. In addition, biopsy slides were stained for p16INK4a expression. RESULTS: No clinical or pathological characteristics were found to have significant associations with time-to-healing. A Cox proportional hazard ratio model revealed increased CDKN1A (p21CIP1/WAF1) expression to predict longer time-to-healing, and a model adjusted for gender and epidermal hyperplasia revealed increased CDKN1A expression and decreased PAPPA expression to predict longer time-to-healing. Increased p16INK4a staining was observed in diabetic wounds compared to non-diabetic wounds, and the same association was observed in the context of high dermal fibrosis. CONCLUSIONS: The findings of this pilot study suggest that senescent cells contribute to wound chronicity in humans, especially in diabetic wounds.

Cell senescence, the senescence-associated secretory phenotype, and cancers.

Cellular senescence is a cell fate caused by multiple stresses. A 2008 article in PLOS Biology reported a senescence-associated secretory phenotype that can promote inflammation and cancer, eventually enabling the development of senolytic drugs.

SARS-CoV-2 causes senescence in human cells and exacerbates the senescence-associated secretory phenotype through TLR-3.

Senescent cells, which arise due to damage-associated signals, are apoptosis-resistant and can express a pro-inflammatory, tissue-destructive senescence-associated secretory phenotype (SASP). We recently reported that a component of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) surface protein, S1, can amplify the SASP of senescent cultured human cells and that a related mouse ß-coronavirus, mouse hepatitis virus (MHV), increases SASP factors and senescent cell burden in infected mice. Here, we show that SARS-CoV-2 induces senescence in human non-senescent cells and exacerbates the SASP in human senescent cells through Toll-like receptor-3 (TLR-3). TLR-3, which senses viral RNA, was increased in human senescent compared to non-senescent cells. Notably, genetically or pharmacologically inhibiting TLR-3 prevented senescence induction and SASP amplification by SARS-CoV-2 or Spike pseudotyped virus. While an artificial TLR-3 agonist alone was not sufficient to induce senescence, it amplified the SASP in senescent human cells. Consistent with these findings, lung p16INK4a+ senescent cell burden was higher in patients who died from acute SARS-CoV-2 infection than other causes. Our results suggest that induction of cellular senescence and SASP amplification through TLR-3 contribute to SARS-CoV-2 morbidity, indicating that clinical trials of senolytics and/or SASP/TLR-3 inhibitors for alleviating acute and long-term SARS-CoV-2 sequelae are warranted.

Epigenetic and senescence markers indicate an accelerated ageing-like state in women with preeclamptic pregnancies.

BACKGROUND: Preeclampsia is a pregnancy-specific hypertensive disorder characterized by proteinuria and/or multisystem involvement. Disease-specific therapy has yet to be developed due to the lack of understanding of underlying mechanism(s). We postulate that accelerated ageing in general, and particularly cellular senescence, play a role in its pathophysiology. METHODS: We compared women with preeclampsia vs. normotensive pregnancies with respect to epigenetic markers of ageing and markers of senescence in tissues/organs affected by preeclampsia (blood, urine, adipose tissue, and kidney). FINDINGS: We demonstrate that preeclamptic compared to normotensive pregnant women: (i) undergo accelerated epigenetic ageing during pregnancy, as demonstrated by an "epigenetic clock"; (ii) exhibit higher levels/expression of senescence-associated secretory phenotype factors in blood and adipose tissue; (iii) display increased expression of p16INK4A in adipose tissue and renal sections, and (iv) demonstrate decreased levels of urinary α-Klotho (an anti-ageing protein) at the time of delivery. Finally, we provide data indicating that pre-treatment with dasatinib, a senolytic agent, rescues the angiogenic potential of mesenchymal stem cells (MSC) obtained from preeclamptic pregnancies, and promotes angiogenesis, even under pro-inflammatory conditions. INTERPRETATION: Taken together, our results identify senescence as one of the mechanisms underpinning the pathophysiology of preeclampsia. Therapeutic strategies that target senescent cells may offer novel mechanism-based treatments for preeclampsia. FUNDING: This work was supported by NIH grants, R01 HL136348, R37 AG013925, P01 AG062413, R01 DK11916, generous gifts from the Connor Fund, Robert J. and Theresa W. Ryan and from The George G. Beasley family, the Noaber Foundation, and the Henry and Emma Meyer Professorship in Molecular Genetics.

Senolytics decrease senescent cells in humans: Preliminary report from a clinical trial of Dasatinib plus Quercetin in individuals with diabetic kidney disease.

BACKGROUND: Senescent cells, which can release factors that cause inflammation and dysfunction, the senescence-associated secretory phenotype (SASP), accumulate with ageing and at etiological sites in multiple chronic diseases. Senolytics, including the combination of Dasatinib and Quercetin (D + Q), selectively eliminate senescent cells by transiently disabling pro-survival networks that defend them against their own apoptotic environment. In the first clinical trial of senolytics, D + Q improved physical function in patients with idiopathic pulmonary fibrosis (IPF), a fatal senescence-associated disease, but to date, no peer-reviewed study has directly demonstrated that senolytics decrease senescent cells in humans. METHODS: In an open label Phase 1 pilot study, we administered 3 days of oral D 100 mg and Q 1000 mg to subjects with diabetic kidney disease (N = 9; 68·7 ±â€¯3·1 years old; 2 female; BMI:33·9 ±â€¯2·3 kg/m2; eGFR:27·0 ±â€¯2·1 mL/min/1·73m2). Adipose tissue, skin biopsies, and blood were collected before and 11 days after completing senolytic treatment. Senescent cell and macrophage/Langerhans cell markers and circulating SASP factors were assayed. FINDINGS: D + Q reduced adipose tissue senescent cell burden within 11 days, with decreases in p16INK4A-and p21CIP1-expressing cells, cells with senescence-associated ß-galactosidase activity, and adipocyte progenitors with limited replicative potential. Adipose tissue macrophages, which are attracted, anchored, and activated by senescent cells, and crown-like structures were decreased. Skin epidermal p16INK4A+ and p21CIP1+ cells were reduced, as were circulating SASP factors, including IL-1α, IL-6, and MMPs-9 and -12. INTERPRETATION: "Hit-and-run" treatment with senolytics, which in the case of D + Q have elimination half-lives <11 h, significantly decreases senescent cell burden in humans. FUND: NIH and Foundations. ClinicalTrials.gov Identifier: NCT02848131. Senescence, Frailty, and Mesenchymal Stem Cell Functionality in Chronic Kidney Disease: Effect of Senolytic Agents.

Targeting senescent cells alleviates obesity-induced metabolic dysfunction.

Adipose tissue inflammation and dysfunction are associated with obesity-related insulin resistance and diabetes, but mechanisms underlying this relationship are unclear. Although senescent cells accumulate in adipose tissue of obese humans and rodents, a direct pathogenic role for these cells in the development of diabetes remains to be demonstrated. Here, we show that reducing senescent cell burden in obese mice, either by activating drug-inducible "suicide" genes driven by the p16Ink4a promoter or by treatment with senolytic agents, alleviates metabolic and adipose tissue dysfunction. These senolytic interventions improved glucose tolerance, enhanced insulin sensitivity, lowered circulating inflammatory mediators, and promoted adipogenesis in obese mice. Elimination of senescent cells also prevented the migration of transplanted monocytes into intra-abdominal adipose tissue and reduced the number of macrophages in this tissue. In addition, microalbuminuria, renal podocyte function, and cardiac diastolic function improved with senolytic therapy. Our results implicate cellular senescence as a causal factor in obesity-related inflammation and metabolic derangements and show that emerging senolytic agents hold promise for treating obesity-related metabolic dysfunction and its complications.