Effects of extracellular matrixes and growth factors on the hepatic differentiation of human embryonic stem cells.

Hepatocytes derived from human embryonic stem cells (hESCs) are a potential cell source for regenerative medicine. However, the definitive factors that are responsible for hepatic differentiation of hESCs remain unclear. We aimed to evaluate the effects of various extracellular matrixes and growth factors on endodermal differentiation and to optimize the culture conditions to induce hepatic differentiation of hESCs. The transgene vector that contained enhanced green fluorescent protein (EGFP) under the control of human alpha-fetoprotein (AFP) enhancer/promoter was transfected into hESC lines. The transgenic hESCs were cultured on extracellular matrixes (collagen type I, laminin, and Matrigel) in the presence or absence of growth factors including hepatocyte growth factor (HGF), bone morphogenetic protein 4, fibroblast growth factor 4, all-trans-retinoic acid, and activin A. The expression of AFP-EGFP was measured by flow cytometry. The culture on Matrigel-coated dishes with 100 ng/ml activin A showed 19.5% of EGFP-positive proportions. Moreover, the sequential addition of 100 ng/ml activin A and 20 ng/ml HGF resulted in 21.7% and produced a higher yield of EGFP-positive cells than the group stimulated by activin A alone. RT-PCR and immunocytochemical staining revealed these EGFP-positive cells to differentiate into mesendoderm-like cells by use of activin A and then into hepatic endoderm cells by use of HGF. Two other hESC lines also differentiated into endoderm on the hepatic lineage by our method. In conclusion, we therefore found this protocol to effectively differentiate multiple hESC lines to early hepatocytes using activin A and HGF on Matrigel.