In vivo analysis of γH2AX+ cells in skeletal muscle from aged and obese humans

Abstract

Over the past 20 years, various identifiers of cellular senescence have been used to quantify the abundance of these cells in different tissues. These include classic markers such as p16, senescence-associated β-gal, and γH2AX, in addition to more recent markers (Sudan Black B and HMGB1). In vivo data on the usefulness of these markers in skeletal muscle are very limited and inconsistent. In the present study, we attempted to identify senescent cells in frozen human skeletal muscle biopsies using these markers to determine the effects of age and obesity on senescent cell burden; however, we were only able to assess the abundance of DNA-damaged nuclei using γH2AX immunohistochemistry. The abundance of γH2AX+ cells, including satellite cells, was not higher in muscle from old compared to young individuals; however, γH2AX+ cells were higher with obesity. Additionally, terminally differentiated, postmitotic myofiber nuclei from obese individuals had elevated γH2AX abundance compared to muscle from lean individuals. Analyses of gene expression support the conclusion that the elevated DNA damage and the senescence-associated secretory phenotype are preferentially associated with obesity in skeletal muscle. These data implicate obesity as a larger contributor to DNA damage in skeletal muscle than aging; however, more sensitive senescence markers for human skeletal muscle are needed to determine if these cells are in fact senescent. K E Y W O R D SDNA damage, postmitotic, satellite cells, senescence, γH2AX | 7019 DUNGAN et Al.

Obese Adipose Tissue as a Driver of Breast Cancer Growth and Development: Update and Emerging Evidence

“…Both BMI and waist circumference were positively associated with DNA damage ( 94 ). Similar findings were made in an aging study, where obesity was a stronger predictor of skeletal muscle DNA damage compared to aging ( 96 ). In preclinical work, obese zucker rats were found to have increased levels of DNA damage in several organ sites as measured by frequency of cells staining positive for phosphorylated histone variant H2AX (γH2AX), a marker of double strand breaks in DNA ( 97 ).…”

Reduced stem cell aging in exercised human skeletal muscle is enhanced by ginsenoside Rg1

“…Increasing p16 INK4a expression during cellular aging is also an intrinsic mechanism to lower mitotic error of aged stem cells [4]. Since most of cells within the human body are short-AGING lived [5], p16 INK4a+ senescent cells are widely detectable in embryonic [6] and young adult tissues [7][8][9]. Lymphocyte p16 INK4a mRNA increases exponentially with age from 18 to 80 years old [10].…”

Regulation of microRNAs in Satellite Cell Renewal, Muscle Function, Sarcopenia and the Role of Exercise

“…However, a recent study had attempted to quantify senescent cells in human skeletal muscle using the phosphorylated form of the histone H2A variant gamma-H2AH (γH2AX) as a marker of DNA damage. In muscle cell biopsy of young subjects compared to elderly ones, the latter did not show a significant increase of senescent cells [52]. Interestingly, the same study demonstrated a higher cells senescence and senescence-associated secretory phenotype in muscle from obese individuals and in in vitro obesogenic environments, suggesting that DNA damage, which may reduce the function of the muscle, is more directly linked to obesity than aging.…”