Transient receptor potential channel TRPV4 mediates TGF-β1-induced differentiation of human ventricular fibroblasts

Background: Cardiac fibroblasts (CFs) are principal extracellular matrix-producing cells. In response to injury, CFs transdifferentiate into myofibroblasts. Intracellular calcium (Ca2+) signaling, involved in fibroblast proliferation and differentiation, is activated in fibroblasts through transient receptor potential (TRP) channels, but the function of these channels has not been investigated in human ventricular CFs. Under evaluation in this study, was the role of TRP channels in the differentiation of human ventricular CFs induced by transforming the growth factor beta (TGF-beta), a pro-fibrotic cytokine. Methods: Human ventricular CFs were used in this study. The differentiation of CFs into myofibroblast was induced with TGF-beta and was identified by the expression of smooth muscle actin. Results: Results indicate that Ca2+ signaling was an essential component of ventricular CF differentiation. CFs treated with TGF-beta demonstrated increased expression of a TRP channel, TRPV4, both at the mRNA and protein levels, which corresponded with CF-myofibroblast trans-differentiation, as evidenced by the upregulation of alpha-smooth muscle actin, a myofibroblast marker, and plasminogen activator inhibitor-1, which are fibrogenesis markers. An agonist of TRPV4 induced the conversion of CFs into myofibroblasts, whereas it's antagonist as well a Ca2+ chelating agent reduced it, indicating that the Ca2+ influx through TRPV4 is required for CF trans-differentiation. Overall, these results demonstrate that TRPV4-mediated Ca2+ influx participates in regulating the differentiation of human ventricular CFs into myofibroblasts through the MAPK/ERK pathway. Conclusions: Overall, these results demonstrate that TRPV4-mediated Ca2+ influx participates in regulating the differentiation of human ventricular CFs into myofibroblasts through the MAPK/ERK pathway.