GSE184413
Mechanotherapy promotes extracellular matrix remodeling in aged rat muscle recovering from disuse by reprogramming intercellular communication
A mechanistic understanding of the age-related impairment to skeletal muscle regrowth following disuse atrophy as well as therapies to augment recovery in the aged are currently lacking. Mechanotherapy in the form of cyclic compressive loading has been shown to benefit skeletal muscle under a variety of paradigms, but not during the recovery from disuse in aged muscle. To determine whether mechanotherapy promotes extracellular matrix (ECM) remodeling, a critical aspect of muscle recovery after atrophy, we performed single cell RNA sequencing (scRNA-seq) of gastrocnemius muscle cell populations, stable isotope tracing of intramuscular collagen, and histology of the ECM in adult and aged rats recovering from disuse, with and without mechanotherapy. ECM remodeling-related gene expression in fibro-adipose progenitor cells (FAPs) was absent in aged compared to adult muscle following 7 days of recovery, and instead were enriched in chemoattractant genes. There was a significantly lower expression of genes related to phagocytic activity in aged macrophages during recovery, despite enriched chemokine gene expression of numerous stromal cell populations, including FAPs and endothelial cells. Mechanotherapy reprogrammed the transcriptomes of both FAPs and macrophages in aged muscle recovering from disuse to restore ECM-and phagocytosis-related gene expression, respectively. Stable isotope labeling of intramuscular collagen and histological evaluation confirmed mechanotherapy-mediated remodeling of the ECM in aged muscle recovering from disuse. In summary, our results highlight mechanisms underlying age-related impairments during the recovery from disuse atrophy and promote mechanotherapy as an intervention that reprograms the muscle transcriptional environment more similar to that of adult skeletal muscle. Overall design: Examination of how extracellular matrix related gene expression in skeletal muscle mononuclear cells changes with age during the recovery from disuse atrophy, and in response to a mechanotherapy