Transplantation of hepatocytes or bone marrow-derived cells has been shown to ameliorate liver fibrosis in animal models, but no direct comparison of relative efficiency has been made. The aim of this study was to compare the efficiency of a bone marrow-derived clonal mesenchymal stem cell line established by us (rBM25/S3) with that of its adipogenic or hepatogenic differentiation derivative for suppression of rat liver fibrosis. After induction of differentiation of rBM25/S3 cells into adipogenic or hepatogenic cells in culture, we intrasplenically transplanted the three types of cells into rats (3 x 10(7) cells/rat) before and 4 weeks after initiation of carbon tetrachloride treatment (1 ml/kg body weight twice a week for 8 weeks) to induce liver fibrosis. Undifferentiated rBM25/S3 cells were the most effective for suppression of liver fibrosis, followed by the adipogenic cells and hepatogenic cells. Expression levels of MMP-2 and MMP-9 were also highest in undifferentiated rBM25/S3 cells. These results indicate that bone marrow-derived clonal mesenchymal stem cell lines are useful for further mechanistic studies on cell-mediated suppression of liver fibrosis and that such cell lines will provide information on an appropriate cell source for transplantation therapy for cirrhosis.