The satellite cells, which serve as adult muscle stem cells, are both located beneath myofiber basement membranes and closely associated with capillary endothelial cells. We observed that 90% of capillaries were associated with pericytes in adult mouse and human muscle. During post-natal growth, newly formed vessels with their neuroglial 2 proteoglycan (NG2)-positive pericytes became progressively associated with the post-natal muscle stem cells, as myofibers increased in size and satellite cells entered into quiescence. In vitro, human muscle-derived pericytes promoted myogenic cell differentiation through insulin-like growth factor 1 (IGF1) and myogenic cell quiescence through angiopoietin 1 (ANGPT1). Diphtheria toxin-induced ablation of muscle pericytes in growing mice led both to myofiber hypotrophy and to impaired establishment of stem cells quiescence. Similar effects were observed following conditional in vivo deletion of pericyte Igf1 and Angpt1 genes, respectively. Our data therefore demonstrate that, by promoting post-natal myogenesis and stem cell quiescence, pericytes play a key role in the microvascular niche of satellite cells.

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