Cholestatic serum in hepatocyte growth factor-induced system promotes the differentiation of embryonic stem cells into functional hepatocytes in vitro / 中国组织工程研究

ABSTRACT

BACKGROUND: Recently, little attention has been paid to how to induce and identify the functions of differentiated cells in the methods for embryonic stem (ES) cells differentiation into hepatocytes. Whether the differentiated cells express functional characteristics of hepatocytes should be one of the markers to identify the hepatic differentiation of ES cells.OBJECTIVE: To direct mouse embryonic stem cells in vitro differentiation into functional hepatocytes by introduction of murine cholestatic serum in hepatocyte growth factor (HGF)-induced system.DESIGN: A controlled observation and in vitro cytological trial.SETTING: Department of Hepatobiliary Surgery, the Second Affiliated Hospital of Sun Yat-sen University.MATERIALS The experiment was carried out in the Medical Research Center of the Second Affiliated Hospital of Sun Yat-sen University from October 2004 to February 2007. The mouse E14 ES cell line was kindly provided by the Stem Cell and Tissue Engineering Center of Sun Yat-sen University. Twenty male SD rats, aged 2 weeks, were purchased from the Experimental Animal Center of Sun Yat-sen University. All animal experimental procedures were abided by the rules of animal ethnics.METHODS: The SD rats were undergone common bile duct ligation to induce cholestasis. Ten days after the operation, the whole blood of rats was collected to prepare cholestatic serum. The ES cells were cultured using hanging-drop method for 5-7 days to develop embryonic bodies (EBs). The dissociated EBs cells were then induced hepatic differentiation with spontaneous system, HGF (20 μg/L) system and cholestatic serum (5%) plus HGF (20 μg/L) system, respectively.MAIN OUTCOME MEASURES: The cellular morphologic changes were observed using transverse microscopy dynamically. (2) The cell staining for albumin, α-fetoprotein, CK18/19, glycogen, indocyanine green (ICG) and fluorescein diacetate (FDA) was done after 4 weeks differentiation. (3) The hepatocyte-specific metabolic functions of synthesizing albumin, triacylglycerol and urea nitrogen were assayed at 3 days interval.RESULTS: (1) The differentiation of ES cells cultured in spontaneous system was uncontrolled and the cells could grow into a wide range of three-germ cells. The HGF could promote ES cells differentiation into endoderm and mesoderm (myocardium). But the differentiated cells only expressed low levels of hepatic specific functions in these two induced systems. (2) Under cholestatic serum plus HGF system, the ES cells could differentiate into polygonal cells with very uniform morphology which were positive in glycogen, ICG and FDA staining and showed higher capabilities of synthesizing albumin, triacylglycerol and urea nitrogen than the differentiated cells in the other systems (P＜0.05-0.01).CONCLUSION: The cholestatic serum, a mimic pathological microenvironment in vitro, could effectively promote ES cells-derived hepatocytes induced by HGF to express high level of liver-specific metabolism functions.