Differential and combined effects of cardiotrophin-1 and TGF-β1 on cardiac myofibroblast proliferation and contraction

Abstract

Myofibroblasts respond to an array of signals from mitogens and cytokines during the course of wound healing following a myocardial infarction (MI), and these signals may coordinate ventricular myofibroblast proliferation. Furthermore, myofibroblasts are contractile and contribute to wound contraction by imparting mechanical tension on surrounding extracellular matrix. Although TGF-β1, CT-1, and PDGF-BB participate in various stages of post-MI wound healing, their combined net effect(s) on myofibroblast function is unknown. We investigated myofibroblast proliferation, expression of cell cycle proteins, and contractile function of cells treated with TGF-β1 and/or CT-1. We confirmed that TGF-β1 (10 ng/ml) suppresses proliferation of these cells, whereas CT-1 (10 ng/ml) and, for comparative purposes, PDGF-BB (1 ng/ml) treatments were associated with proliferation. Specific TGF-β1 treatment ablated CT-1-induced myofibroblast proliferation. TGF-β1 effects were specific, as they were suppressed by either TGF-β-neutralizing antibody or viral Smad7 overexpression. TGF-β1 treatment also increased expression of p27 and decreased expression of cyclin E and Cdk2 in primary cells. CT-1 (10 ng/ml) treatment of myofibroblasts had no effect on collagen gel deformation versus controls, whereas TGF-β1 (10 ng/ml) and PDGF (10 ng/ml) treatments were associated with significant cell contraction; again, TGF-β1-mediated contraction was unaffected by CT-1. Alone, CT-1 and TGF-β1 treatments exert opposing effects on myofibroblast function, whereas in combination TGF-β1-mediated effects supersede those of CT-1 (and PDGF-BB). Thus TGF-β1 and CT-1 exert differential effects on myofibroblast proliferation and contraction in vitro, and we suggest that a balance of these effects may be important for the execution of normal cardiac wound healing.