Transforming growth factor-β1 promotes contraction of collagen gel by cardiac fibroblasts through their differentiation into myofibroblasts

Myofibroblasts and transforming growth factor-beta (TGF-beta(1)) are key elements of cardiac tissue fibrosis development. The aim of this study was to determine whether the ability of TGF-beta(1) to affect the contractile activity of cardiac fibroblasts depends on their differentiation into myofibroblasts. Cardiac fibroblasts (from male adult Wistar rats) from passage 2 were therefore cultured to confluency and incubated on a hydrated collagen gel, both with and without TGF-beta(1) (0, 20, 40, 100, 200, 400 or 600 pmol/l), for 1, 2 and 3 days in a Dulbeccos Modified Eagles Medium (DMEM) without fetal bovine serum (FBS). Growing cultures of cardiac fibroblasts were obtained by incubating second-passage fibroblasts in DMEM with 10% FBS with or without TGF-beta(1) (0 to 600 pmol/l) for 6 days. These fibroblasts were then further incubated on the collagen gel for 1, 2 and 3 days in DMEM without FBS. TGF-beta(1) dose-dependently increased the contraction of collagen gel mediated by cardiac fibroblasts, either added directly to the gel or after growing of the cardiac fibroblasts in the presence of TGF-beta(1) for 6 days, reaching a maximal effect at 100 pmol/l TGF-beta(1). In both culturing conditions, TGF-beta(1) also stimulated the [H-3]-thymidine incorporation and the total protein content in the cardiac fibroblasts in the collagen gel lattice. TGF-beta(1) dose-dependently induced an increase in alpha-smooth muscle actin, a marker of myofibroblasts, in both culturing conditions. The TGF-beta(1)-induced reduction of area of the collagen gel was negatively correlated to the TGF-beta(1)-evoked appearance of alpha-smooth muscle actin in the collagen gel matrix. TGF-beta(1) increased the contractile activity of adult rat cardiac fibroblasts and their ability to differentiate into myofibroblasts. Because contractile activity was correlated with differentiation, the influence of TGF-beta(1) on cardiac fibroblast-induced collagen gel contraction may depend on the promotion of myofibroblast differentiation. (C) 2003 Prous Science. All rights reserved.