Fig. 1

The life cycle of muscle stem cells. MuSCs are located between the basal lamina of the muscle fibers and the sarcolemma. They undergo symmetric division or asymmetric division to maintain muscle homeostasis. G-CSF and EGFR have important roles in regulating the asymmetric division of MuSCs. Upon injury, MuSCs are activated and released from the niche. The necroptotic myofibers, FAPs, and infiltrated immune cells provide the microenvironment for MuSC proliferation. TNFα, IFNγ, IL-1ꞵ, IL-13, TNC, Collagen V, and other factors facilitate MuSC proliferation. The proliferated MuSCs fuse with the existing myofibers or differentiate to new myofibers to regenerate injured skeletal muscle. A small portion of MuSCs return to quiescence and replenish the stem cell pool