Molecular Marker And Regulational Mechanisms Of Cholangiocytic Differentiation In Fetal Hepatic Stem Cell

Liver stem cells are known to have differential capacities into hepatocyte and cholangiocyte. As the important member in “stem cellular therapy”, liver stem cells has aroused great concern and demand. However, current research about the differential characteristics and regulatory mechanisms of fetal hepatic stem cell is not yet mature, which restricts its clinic application greatly. Here, we enriched spheroidforming cells from mouse embryonic day 12.5 using suspension culture method, and found that these hepatic spheroid-derived cells had characteristics and differential potency of liver stem cell and stromal cell at the same time. This indicated that they were hepatic in epithelial-mesenchymal transition(EMT). We further discovered that it actually had Dlk1+ and Dlk1- subpopulations, and Dlk1+ cells could transform into Dlk1- cells. Considering that there exists membrane-bound Dlk1(Dlk1M) and secretory Dlk1(Dlk1S), We also demonstrated that Dlk1+ cells expressed both Dlk1 M and Dlk1 S, but Dlk1- cells only expressed Dlk1 S. Further study discovered that Dlk1+ cells could lose Dlk1 M and transformed into Dlk1- cells. Dlk1- cells remained the proliferative capacity, however, they had increased EMT level and acquired the speciality of biliary progenitor cell.After Dlk1- cells was transfected with Dlk1 M overexpression plasmid and reexpressed Dlk1 M, their differential characteristics could be reversed, which showed Dlk1 M had regulating function. And bFGF played an important role in inducing the disappearance of Dlk1 M in Dlk1+ cells. In addition, the analysis about autophagy indicated that the autophagy levels decreased when Dlk1+ cells transformed to Dlk1-cells, suggesting that autophagy may play a functional role in fetal hepatic stem cell.In conclusion, our study clarifies the dynamic changes of Dlk1 during the stem cell development, and reveals multiple factors involved in the differential process. This rereach not only provides theoretical guidance for the applications of liver stem cell, but also provides inspiration for the pathogenesis of liver-related diseases, such as cholangiocarcinoma.