Heat Shock Enhances Troponin Expression and Decreases Differentiation-Associated Caspase-3 Dependence in Myoblasts Under Hypoxia

Abstract

Myoblast transplantation can functionally restore muscle tissues damaged by ischemic or other insults. Despite promising results in clinical trials, however, myoblast transplantation still presents several challenges, with effective differentiation under harsh conditions of the host tissue being one of the most demanding. In keeping with a straightforward clinical application, heat shock (HS) pretreatment as a nonviral method can be utilized with promising results in cell therapy. The aim of this study was to demonstrate whether HS-pretreated cells would receive a differentiation benefit under hypoxic conditions. We studied HS preconditioning of C2C12 myoblasts in relation to their differentiation- and apoptosis-associated responses under normoxia or 1% hypoxia. HS induced long-lasting expression of Hsp70/72 and Hsp90. Although myoblast differentiation proceeded in HS-pretreated and control cells under both normoxia and hypoxia, expression of differentiation-associated troponin was enhanced in HS-preconditioned cells under hypoxia. This effect persisted when differentiation was inhibited by Z-DEVD-FMK, a caspase-3 inhibitor. HS preconditioning enhances expression of myoblast differentiation-associated troponin and may reduce dependence of differentiation on caspase-3.