Figure 1. Functional heterogeneity within biliary epithelial cell (BECs) subsets. BECs expand around the portal vein following injury forming auxiliary ducts during a ductular reaction (DR) . Single-cell sequencing revealed heterogeneity within BECs and highlighted distinct subsets with increased proliferate capacity, hepatocyte markers or expression of pro-inflammatory genes . BECs can expand during DR or transdifferentiate into hepatocytes to support liver regeneration [2,3]. However, BECs can also promote inflammation and peribiliary fibrosis, and overt proliferation of malignant transformed BECs results into cholangiocarcinoma formation [7,8].