Muscle Satellite Cell Cross-Talk with a Vascular Niche Maintains Quiescence via VEGF and Notch Signaling.

Skeletal muscle is a complex tissue containing tissue resident muscle stem cells (satellite cells) (MuSCs) important for postnatal muscle growth and regeneration. Quantitative analysis of the biological function of MuSCs and the molecular pathways responsible for a potential juxtavascular niche for MuSCs is currently lacking. We utilized fluorescent reporter mice and muscle tissue clearing to investigate the proximity of MuSCs to capillaries in 3 dimensions. We show that MuSCs express abundant VEGFA, which recruits endothelial cells (ECs) in vitro, whereas blocking VEGFA using both a vascular endothelial growth factor (VEGF) inhibitor and MuSC-specific VEGFA gene deletion reduces the proximity of MuSCs to capillaries. Importantly, this proximity to the blood vessels was associated with MuSC self-renewal in which the EC-derived Notch ligand Dll4 induces quiescence in MuSCs. We hypothesize that MuSCs recruit capillary ECs via VEGFA, and in return, ECs maintain MuSC quiescence though Dll4.