Recently hepatic differentiation of mesenchymal stem cells (MSCs) from bone marrow (BM), adipose tissue (AT), umbilical cord blood (UCB), and umbilical cord (UC) has been reported. In this study, the four-step sequential exposure with oncostatin M (OSM) plus trichostatin A (TSA) or OSM plus dimethyl sulfoxide (DMSO) at the final step induced hepatic differentiation of UC-MSCs. As a result, the morphology and protein expression were sequentially changed in the step-dependent manner. And the urea synthesis rates of (OSM plus TSA)- and (OSM plus DMSO)-treated cells on day 21 reached to 23 +/- 0.4 and 20 +/- 0.5 mu g/10(6) cells/day, respectively. The ammonia concentrations 24 h after culture with 1 mM NH(4)Cl-supplemented medium dropped to 0.41 +/- 0.08 mM (OSM plus TSA) and 0.57 +/- 0.05 mM (OSM plus DMSO). Also the ethoxyresorufin O-deethylase (EROD) activities were 3.4-fold (OSM plus TSA) and 2.2-fold (OSM plus DMSO) higher than non-induced controls on day 21. It is thought that TSA and DMSO cause the expression of key genes through epigenetic change. Although sequential exposure with TSA or DMSO induced some liver-specific functions to some extent, the degree of activities are yet lower than those of mature hepatocytes. So it will be necessary to optimize the concentration and exposure time for achieving comparable activities to normal hepatocytes in the future. (C) 2010 Elsevier Ltd. All rights reserved.