The
polypeptide hormone relaxin has been proven to be effective in promoting both the remodeling and regeneration of various tissues, including cardiac muscle. In addition, our previous study demonstrated that
relaxin is beneficial to skeletal muscle healing by both promoting muscle regeneration and preventing
fibrosis formation. However, the molecular and cellular mechanisms of
relaxin in regulating both myogenic cell differentiation and muscle healing process are still unclear. In this study, C2C12 mouse myoblasts and primary human myoblasts were treated with
relaxin to investigate its potential effect in vitro;
relaxin was also injected intramuscularly into the injured site of the mouse on the second day after injury to observe its function in vivo, especially in the aged muscle. Results showed that
relaxin promoted myogenic differentiation, migration, and activation of
matrix metalloproteinases (
MMPs) of cultured myoblasts in vitro. In the injured muscle,
relaxin administration promoted the activation of Pax7-positive skeletal muscle satellite cells and increased its local population compared with nontreated control muscles. Meanwhile, both angiogenesis and revascularization were increased, while the extended inflammatory reaction was repressed in the
relaxin-treated injured muscle. Moreover,
relaxin similarly promoted muscle healing in mice with aged muscle. These results revealed the multiple effects of
relaxin in systematically improving muscle healing as well as its potential for clinical applications in patients with skeletal muscle
injuries and diseases.