TRPV2 in muscle satellite cells is crucial for skeletal muscle remodelling

Skeletal muscle remodelling relies on muscle stem cells (MuSCs) for regeneration after injury and hypertrophy in response to mechanical loading. However, the mechanisms that trigger MuSC activation and proliferation remain unclear. Transient receptor potential vanilloid 2 (TRPV2) ion channels respond to insulin-like growth factor-1 and mechanical stimuli to regulate the biological characteristics of various cells. Using a temporally inducible MuSC-specific conditional knockout (cKO) mouse, we show that TRPV2 regulates MuSC function and is essential for muscle remodelling. In cultured myofibre, MuSCs express TRPV2 and exhibit Ca2+ responses to the TRPV2 agonists 2-aminoethoxydiphenyl borate and probenecid, which are abolished upon TRPV2 deletion. TRPV2-deficient MuSCs exhibit reduced paired box 7 (Pax7) expression and impaired proliferation, suggesting TRPV2 is a factor that regulates the early stage of MuSC function. Myotube formation in MuSCs was enhanced by overexpression of TRPV2 and suppressed by TRPV2 deficiency, suggesting that TRPV2 is a factor that promotes myogenesis. Muscle-administered cardiotoxin promoted muscle regeneration and resulted in the appearance of numerous Pax7-positive MuSCs between myofibres. MuSC-specific TRPV2 cKO mice exhibit substantially impaired muscle regeneration after cardiotoxin-induced injury, drastically reducing Pax7-positive MuSCs between myofibres. In floxed mice, mechanical loading via synergist ablation induces hypertrophy and greatly increases the number of myonuclei per myofibre. In contrast, MuSC-specific TRPV2 cKO mice show no changes in myofibre thickness or nuclear number, either at baseline or after mechanical loading. Mechanical loading of floxed mice increased TRPV2+/Pax7+ double-positive MuSCs, but MuSC-specific TRPV2 cKO mice showed no change. Additionally, MuSCs exhibit Ca2+ responses to hypo-osmotic stimuli, which are suppressed by TRPV2 inhibitors and TRPV2 deletion, suggesting that MuSCs exhibit TRPV2-dependent mechanical responses. These results establish TRPV2 as a critical regulator of MuSC-mediated muscle remodelling, an important finding that may lead to therapeutic strategies for muscle repair and adaptation.