Hepatic biliary epithelial cells acquire epithelial integrity but lose plasticity to differentiate into hepatocytes in vitro during development

Abstract

In developing organs, epithelial tissue structures are mostly developed by perinatal period. However, it is unknown whether epithelial cells are already functionally matured and whether they are fixed in their lineage. Here we show that epithelial cells alter plasticity during postnatal development by examining differentiation potential of epithelial cell adhesion molecule (EpCAM)+ cholangiocytes (biliary epithelial cells) isolated from neonatal and adult mouse livers. We found that neonatal cholangiocytes isolated from 1-week-old liver converted into functional hepatocytes in the presence of oncostatin M and Matrigel®. On the other hand, neither morphological changes nor expression of hepatocyte markers were induced in adult cholangiocytes. The transcription factors hepatocyte nuclear factor 4α and CCAAT/enhancer binding protein α (C/EBPα), which are necessary for hepatocytic differentiation, were induced in neonatal cholangiocytes but not in adult cells, whereas grainyhead-like 2 (Grhl2) and hairy-enhance of slit 1 (Hes1), which are implicated in cholangiocyte differentiation, were continuously expressed in adult cells. Overexpression of C/EBPα and Grhl2 promoted and inhibited hepatocytic differentiation, respectively. Furthermore, adult cholangiocytes formed a monolayer with higher barrier function than neonatal ones did, suggesting that cholangiocytes are still on the process of epithelial maturation even after forming tubular structures at neonatal period. Taken together, we considered that cholangiocytes lose plasticity to convert into hepatocytes during epithelial maturation. They lose competency to upregulate hepatocytic transcription factors and downregulate cholagiocytic ones under conditions inducing hepatocytic differentiation. Our results suggest that a molecular machinery augmenting epithelial integrity limits lineage plasticity of epithelial cells (243 words).