Hepatic differentiation of mouse ES cells into BE cells in vitro.

To date, the hepatic differentiation of embryonic stem (ES) cells into biliary epithelial (BE) cells has only been identified in hepatocytes. In this study, an attempt was made to induce the differentiation of ES cells to BE cells. In order to induce hepatic, and then BE cell differentiation, growth factors such as TGF, FGF, HGF and EGF were added to the culture medium supplied to embryonic bodies (EBs) that were derived from ES cells. The marker genes and corresponding proteins of hepatocytes and BE cells such as AFP, ALB, CK8, CK18, CK7, CK19 and GGT, etc. were detected by reverse transcriptase-polymerase chain reaction (RT-PCR), immunocytochemistry (ICC) and enzymatic histochemistry. Lastly, the ratio of BE-like cells to all EBs cells was analyzed and determined by flow cytometry (FCM). Hepatocyte and BE cell marker genes and proteins were found to be expressed in the cytoplasm of differentiated cells. On day 10 of differentiation, many round structures appeared in the EBs culture system and the marker proteins of BE cells were found to be expressed in these structures. The BE cell differentiation ratio continually increased from its initial value of 1.7% on day 13 to 7.4% on day 21. ES cells were found to be able to differentiate into BE cells when cultured using medium with appropriate cell growth factors. These BE cells may be a novel source of differentiated cell types for liver engineering.