Wnt/β-catenin信号调控EMT水平对小鼠胚胎干细胞向肝脏组织结构分化的影响

Objective: To study embryonic stem cell (ESC) differentiation into liver tissue structure from the perspective of epithelial mesenchymal transition (EMT). Methods: ESC of Balb/c mice was selected to induced into hepatic cell using hepatocyte growth factor (HGF), fibroblast growth factor (FGF) in vitro, and at the time points of metaphase (13 d) and maturity (17 d) of differentiation, dynamic inhibition of Wnt/β-catenin signal was made to reduce the level of EMT. Finally, three-dimensional organization structure growth of the differentiation cells was observed in the differentiation system. Expressions of the liver cells vascular markers[albumin (Alb) and vascular endothelial growth factor (VEGFR)]were detected. Results: During the differentiation of ESC, the level of early EMT in the experimental group and the control group was not significantly different. The level of mid-late EMT in the experiment group was significantly lower than the control group. On the day 18 and 20 of differentiation, the relative mRNA expression level of E-cadherin was 0.61±0.15 and 0.47±0.05 in the experimental group, and 0.07±0.05 and 0 in the control group, respectively. The expression level of ALB/AFP/CK8/CK19 in the experimental group was generally higher than that of the control group in the same period, while CD31/VEGFR1 markers in the experimental group decreased more slowly in the late period of differentiation compared with the control group. In the supernatant of ESC culture, the Alb of the experimental group could be detected onday 7, and the concentration was (0.32±0.02) mg/L, while Alb in the control group was (0.19±0.05) mg/L. Urea in the experimental group could be detected on the day 13, and the concentration was (8.7 ±1.0) μmol/L, and the urea concentration of the control group was (3.1±1.2) μmol/L. The concentration of Alb and urea in the culture supernatant of ESC differentiation system increased significantly with the prolongation of the differentiation time, and the Alb and urea concentrations in the experimental group were significantly higher than those in the control group at the same time period. In addition, the differentiated cells in the experimental group could maintain the growth of three-dimensional tissue, while the differentiated cells in the control group eventually showed a single cell state. The expression of hepatic and vascular cell markers could be detected in the experimental group. Immunofluorescence results showed that the hepatocytes and vascular structures were tightly arranged. HE staining showed the formation of hepatic lobular structure, while the control group had no vascular component markers. Conclusion: The differentiation of ESC into liver tissue can be effectively promoted by decreasing the level of EMT at the mid-late stage of ESC differentiation.