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Increased Adipocyte Area in Injured Muscle With Aging and Impaired Remodeling in Female Mice.

ABSTRACT: We demonstrated that young male and female mice similarly regenerated injured skeletal muscle; however, female mice transiently increased adipocyte area within regenerated muscle in a sex hormone-dependent manner. We extended these observations to investigate the effect of aging and sex on sarcopenia and muscle regeneration. Cardiotoxin injury to the tibialis anterior muscle of young, middle, and old-aged C57Bl/6J male and female mice was used to measure regenerated myofiber cross-sectional area (CSA), adipocyte area, residual necrosis, and inflammatory cell recruitment. Baseline (uninjured) myofiber CSA was decreased in old mice of both sexes compared to young and middle-aged mice. Regenerated CSA was similar in male mice in all age groups until baseline CSA was attained but decreased in middle and old age female mice compared to young females. Furthermore, adipocyte area within regenerated muscle was transiently increased in young females compared to young males and these sex-dependent increases persisted in middle and old age female mice and were associated with increased Pparg Young female mice had more pro-inflammatory monocytes/macrophages in regenerating muscle than young male mice and increased Sca-1(+)CD45(-)cells. In conclusion, sex and age influence pro-inflammatory cell recruitment, muscle regeneration, and adipocyte area following skeletal muscle injury.

SUBMITTER: Fearing CM

PROVIDER: S-EPMC4945881 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Increased Adipocyte Area in Injured Muscle With Aging and Impaired Remodeling in Female Mice.

Fearing Caitlin M CM Melton David W DW Lei Xiufen X Hancock Heather H Wang Hanzhou H Sarwar Zaheer U ZU Porter Laurel L McHale Matthew M McManus Linda M LM Shireman Paula K PK

The journals of gerontology. Series A, Biological sciences and medical sciences 20150813 8

We demonstrated that young male and female mice similarly regenerated injured skeletal muscle; however, female mice transiently increased adipocyte area within regenerated muscle in a sex hormone-dependent manner. We extended these observations to investigate the effect of aging and sex on sarcopenia and muscle regeneration. Cardiotoxin injury to the tibialis anterior muscle of young, middle, and old-aged C57Bl/6J male and female mice was used to measure regenerated myofiber cross-sectional area ...[more]

PMID: 26273023

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Project description:BackgroundPresently, there is no effective treatment for the lethal muscle wasting disease Duchenne muscular dystrophy (DMD). Here we show that increased sphingosine-1-phoshate (S1P) through direct injection or via the administration of the small molecule 2-acetyl-4(5)-tetrahydroxybutyl imidazole (THI), an S1P lyase inhibitor, has beneficial effects in acutely injured dystrophic muscles of mdx mice.MethodsWe treated mdx mice with and without acute injury and characterized the histopathological and functional effects of increasing S1P levels. We also tested exogenous and direct administration of S1P on mdx muscles to examine the molecular pathways under which S1P promotes regeneration in dystrophic muscles.ResultsShort-term treatment with THI significantly increased muscle fiber size and extensor digitorum longus (EDL) muscle specific force in acutely injured mdx limb muscles. In addition, the accumulation of fibrosis and fat deposition, hallmarks of DMD pathology and impaired muscle regeneration, were lower in the injured muscles of THI-treated mdx mice. Furthermore, increased muscle force was observed in uninjured EDL muscles with a longer-term treatment of THI. Such regenerative effects were linked to the response of myogenic cells, since intramuscular injection of S1P increased the number of Myf5nlacz/+ positive myogenic cells and newly regenerated myofibers in injured mdx muscles. Intramuscular injection of biotinylated-S1P localized to muscle fibers, including newly regenerated fibers, which also stained positive for S1P receptor 1 (S1PR1). Importantly, plasma membrane and perinuclear localization of phosphorylated S1PR1 was observed in regenerating muscle fibers of mdx muscles. Intramuscular increases of S1P levels, S1PR1 and phosphorylated ribosomal protein S6 (P-rpS6), and elevated EDL muscle specific force, suggest S1P promoted the upregulation of anabolic pathways that mediate skeletal muscle mass and function.ConclusionsThese data show that S1P is beneficial for muscle regeneration and functional gain in dystrophic mice, and that THI, or other pharmacological agents that raise S1P levels systemically, may be developed into an effective treatment for improving muscle function and reducing the pathology of DMD.

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Dataset Information

Increased Adipocyte Area in Injured Muscle With Aging and Impaired Remodeling in Female Mice.

Publications

Increased Adipocyte Area in Injured Muscle With Aging and Impaired Remodeling in Female Mice.

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