Pericytes in the myovascular niche promote postnatal myofiber growth and satellite cell quiescence

The satellite cells, which serve as adult muscle stem cells, are both located beneath myofiber basement membranes and closely associated to capillary endothelial cells. We observed that 90% capillaries are associated with pericytes in adult mouse and human muscle. During postnatal growth, newly-formed vessels with their NG2+ pericytes became progressively associated with the postnatal 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 IGF-1, and myogenic cell quiescence through Angiopoietin-1. Diphtheria toxin-induced ablation of muscle pericytes in growing mice led to both myofiber hypotrophy and impaired establishment of stem cells quiescence. Similar effects were observed following conditional in vivo deletion of pericyte IGF-1 and Angiopoietin-1 genes, respectively. Our data therefore demonstrate that, by promoting postnatal myogenesis and stem cell quiescence, pericytes play a key role in the microvascular niche of satellite cells.