Deficiency of G9a boosts muscle regeneration through IL13/Musclin-mediated crosstalk between macrophage and myofiber.

Muscle regenerative capacity declines with aging and disease, which leads to muscle loss and reduced lifespan. Muscle regenerative failure is related to a disrupted network orchestrated by multiple muscle-harbored cell types; whether and how the interplay between macrophages and myofibers contributes to this process is largely unknown. Herein, we report upregulation of histone methyltransferase G9a in both aged human muscle and mouse muscle after injury. Deletion of G9a in either myeloid cells or myofibers accelerates muscle regeneration. Mechanistically, G9a down-regulates macrophage-derived interleukin 13 (IL13) and suppresses myofiber-derived myokine musclin, respectively, to inhibit myogenesis and macrophage phenotype transition during muscle regeneration. Either IL13 or musclin, per se, accelerated muscle regeneration, and their combined administration showed synergistic effects with therapeutic potentials for muscle degeneration disorders. Collectively, we highlight a crosstalk between macrophages and myofibers through IL13-Stat6 signaling and musclin, both regulated by G9a, which steers a pro-recovery microenvironment after muscle injury, with therapeutic potentials for muscle degeneration disorders.