The purpose of this study is to investigate the effect of interferon-gamma (IFN-gamma) on myofibroblast generation using four myofibroblast cell lines that we established from Dupuytren's nodules. Cells were cultured in Earl's medium with 15% fetal bovine serum (FBS) and plated on a microplate at a density of 10(4) cells/well. These cells were treated with various concentrations of IFN-gamma (0-1000 U/mL) for 3 days. By cell-capture enzyme immunoassay (CC-EIA), immunofluorescence staining, and reverse transcriptase polymerase chain reaction (RT-PCR) analysis, we evaluated the effect of IFN-gamma on the expression of alpha smooth muscle actin (alpha SMA) in these cells. CC-EIA and RT-PCR analysis showed that IFN-gamma suppressed alpha SMA expression, and immunofluorescence microscopy demonstrated that IFN-gamma markedly decreased the number of alpha SMA-positive cells. These results showed that IFN-gamma strongly inhibits myofibroblast generation in established myofibroblast cell lines and suggest the possibility of using IFN-gamma therapy for contractile disease.