Enhanced in vitro maturation of subcultivated fetal human hepatocytes in three dimensional culture using poly-L-lactic acid scaffolds in the presence of oncostatin M

Fetal human liver cell fractions, which contain large numbers of hepatocyte progenitors, have high proliferation potential in vitro. To create an engineered liver tissue equivalent of a clinically significant size, however, repeated subcultivation and functional maturation are necessary in vitro. A commercially available human fetal liver cell fraction that was cultivated for some time in vitro has been reported to lose liver specific functions almost completely. We therefore investigated the effects of oncostatin M (OSM) and hepatocyte growth factor (HGF) in long term three-dimensional (3D) culture using macroporous poly-L-lactic acid (PLLA) scaffolds on the restoration of such liver-specific functions of the fraction. 3D culture using PLLA scaffolds with OSM remarkably enhanced the albumin production and cytochrome P450 1A1/2 capacity with the culture time. HGF alone had no preferable effect on these functions even in 3D culture. alpha-fetoprotein production was consistently suppressed in the 3D culture compared with that in monolayers. This suppression was not observed in the same types of culture of hepatocarcinoma Hep G2 cells. Despite these favorable observations on the 3D culture with OSM, the final attained functional levels at the 5th week were still over ten-times lower than those of Hep G2 cells when standardized with a cellular DNA amount. Although further improvement is needed for the complete functional restoration and maturation in vitro, these results demonstrate that a combination of 3D culture using PLLA scaffolds and OSM offers promising culture conditions for in vitro maturation of human hepatocyte progenitors.