Mast cells can regulate skeletal muscle cell proliferation by multiple mechanisms

Abstract

Introduction: Mast cells (MCs) can stimulate cell proliferation, but their specific contribution to skeletal muscle regeneration is not well defined.

Methods: L6 myoblast proliferation was assessed in coculture with MCs or when grown with MC-conditioned media. To address the in vivo implication of MCs in regeneration, rats were treated with cromolyn, and myoblast proliferation, immune cell accumulation, and myogenic factors were assessed in bupivacaine-injured muscles.

Results: In vitro, both procedures increased the L6 cell proliferation rate, and this was tryptase-dependent. In vivo, MC stabilization increased myoblast proliferation and accumulation of macrophages CD68 and CD163 after injury. This correlated with a sequential increase in MyoD and myogenin protein level expression.

Conclusions: MCs can directly stimulate muscle cell proliferation via tryptase. MCs can influence myoblast proliferation in vivo, but this effect seems to be predominantly related to their modulation of macrophage recruitment. The MC is a potential actor in the early stages of muscle healing.

Keywords: leukocyte; macrophage; myoblast; myogenesis; tryptase.