Hypertrophic scarring remains a major problem for patients who have suffered deep burns. The pathophysiology underlying hypertrophic scar formation may be driven by the biological activity of transforming growth factor beta1 (TGF-beta(1)). Decorin is a human proteoglycan that inactivates the effect of TGF-beta(1) and therefore displays a beneficial effect of antifibrosis in various tissues. Hypertrophic scarring is a fibroproliferative disorder of the dermis that occurs following wounding. This study investigated the effects of decorin on cell proliferation, TGF-beta(1) production, and collagen synthesis in hypertrophic scar fibroblasts. The cell proliferation rates, cell cycle distribution, low-molecular-weight apoptotic DNA and TGF-beta(1) levels, and contents of type I and type III collagen amino-terminal propeptide (PINP, PIIINP) in supernatants were assessed. Fibroblast proliferation was significantly (P<0.05) inhibited by decorin, and this effect was dose-dependent. The fibroblast population became stationary at decorin concentrations of 100 and 200 nM. Decorin inhibited fibroblast proliferation by inducing cell growth arrest but not apoptosis. TGF-beta(1) and PINP levels were significantly (P<0.05) lower in fibroblasts treated with 10, 50, 100, 200 nM of decorin compared with fibroblasts without decorin addition. However, there was no significant difference in PIIINP concentration between the decorin-treated group and the control group. These results suggest that decorin has a down-regulatory effect on cell proliferation, TGF-beta(1) production, and collagen synthesis in hypertrophic scar fibroblasts. Improved understanding of such a regulatory mechanisms may eventually be of therapeutic significance in the control of hypertrophic scarring.