Figure 1.

JAK-STAT signaling progressively increases with age and inhibits satellite cell function. In young mice, Price et al.² and Tierney et al.³ find that JAK-STAT signaling is low and satellite cells are able to expand to form a proliferating myoblast pool, the majority of which differentiate and fuse to repair muscle fibers. A small fraction return to a quiescent satellite cell state in a process termed self-renewal. In mice in an aging or diseased environment, the authors find that hyperactive JAKSTAT signaling impairs myogenic proliferation, differentiation and self-renewal, leading to diminished regenerative capacity. In the presence of JAK or STAT inhibitors, satellite cell function is restored and muscle regeneration is rescued.