Activation of peroxisome proliferator-activated receptor-γ inhibits transforming growth factor-β1 induction of connective tissue growth factor and extracellular matrix in hypertrophic scar fibroblasts in vitro

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands have been recently reported to have beneficial effects on organ fibrosis. However, their effects on extracellular matrix (ECM) turnover in hypertrophic scar fibroblasts (HSFs), and the related molecular mechanisms are unknown. HSFs were cultured and exposed to different concentration PPAR-gamma ligands in the presence of transforming growth factor-beta 1 (TGF-beta 1). In growth-arrested HSFs, a PPAR-gamma natural ligand (15-deoxy-D12,14-prostaglandin J2, 15d-PGJ2) and a synthetic ligand (GW7845) dose-dependently attenuated TGF beta 1-induced expression of Connective tissue growth factor (CTGF), collagens and fibronectin. Furthermore, the suppression of CTGF mRNA and protein expression are relieved by pretreatment with an antagonist of PPAR-gamma (GW9662). Moreover, GW7845 and 15d-PGJ2 partially inhibited the expression and phosphorylation of the TGF-beta 1/Smad pathway. These results suggest that in TGF beta 1-stimulated HSFs, PPAR-gamma ligands caused an antiproliferative effect and reduced ECM production through mechanisms that included reducing CTGF expression, and a crosstalk between PPAR-gamma and Smad may be involved in the inhibitory effects of PPAR-gamma ligands.