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AIM: To investigate the mechanism and regulation of differentiation from bone marrow mesenchymal stem cells (MSCs) into hepatocytes and to find a new source of celltypes for therapies of hepatic diseases. METHODS: MSCs were isolated by combining gradient density centrifugation with plastic adherence. The cells were cultured in osteogenic or adipogenic differentiation medium and determined by histochemical staining. MSCs were plated in plastic culture flasks that were not coated with components of extracellular matrix (ECM). When MSCs reached 70% confluence, they were cultured in low glucose Dulbeccos modified Eagles medium supplemented with 10 mL/L fetal bovine serum, 20 ng/mL hepatocyte growth factor (HGF) and 10 ng/mL fibroblast growth factor-4 (FGF-4). The medium was changed every 3 d and stored for albumin, alpha-fetoprotein (AFP) and urea assay. Glycogen store of hepatocytes was determined by periodic acid-Schiff staining.RESULTS: By combining gradient density centrifugation with plastic adherence, we isolated a homogeneous population of cells from rat bone marrow and differentiated them into osteocytes and adipocytes. When MSCs were cultured withFGF-4 and HGF, approximately 56.6% of cells became smallround and epithelioid on d 24 by morphology. Compared with the control, levels of AFP increased significantly from d 12 to 15.5±1.4 μg/L (t = 2.31, P＜0.05) in MSCs cultured with FGF-4and HGF, and were higher (46.2±1.5 μg/L)ond 21 (t = 41.926, P＜0.01), then decreased to 24.8±2.2 μg/L on d 24 (t = 10.345, P＜0.01). Albumin increased significantly on d 21 (t= 3.325, P＜0.01) to 1.4±0.2 μg/mL,and to 2.1±0.7 μg/mL on d 24 (t= 3.646, P＜0.01). Urea(2.3±0.4 mmol/L) was first detected on d 21 (t = 6.739, P＜0.01), and continued to increase to 2.6±0.9 mmol/Lon d 24 (t= 4.753, P＜0.01). Glycogen storage was first seen on d 21.CONCLUSION: The method combining gradient density centrifugation with plastic adherence can isolate MSCs. Rat MSCs may be differentiated into hepatocytes by FGF-4 and HGF. Cytokines may play a more important role in differentiation from rat MSCs into hepatocytes.