Lineage tracing demonstrates no evidence of cholangiocyte epithelial-to-mesenchymal transition in murine models of hepatic fibrosis

TLDR

Whether cholangiocytes or their progenitors undergo EMT to become matrix‑producing myofibroblasts during biliary fibrosis is a significant controversy. The study assessed EMT activity during biliary fibrosis using Alfp‑Cre × Rosa26‑YFP mice that label liver epithelial cells with YFP. Cholangiocytes from the reporter strain were induced to undergo EMT in vitro with TGF‑β1/TNF‑α, and in vivo fibrosis was induced in Alfp‑Cre × Rosa26‑YFP mice using bile duct ligation, CCl₄, and DDC models. No YFP‑positive cells co‑expressed mesenchymal markers in any fibrosis model, indicating hepatocytes and cholangiocytes do not undergo EMT in mice. Hepatology 2011.

Abstract

Abstract Whether or not cholangiocytes or their hepatic progenitors undergo an epithelial-to-mesenchymal transition (EMT) to become matrix-producing myofibroblasts during biliary fibrosis is a significant ongoing controversy. To assess whether EMT is active during biliary fibrosis, we used Alfp-Cre × Rosa26-YFP mice, in which the epithelial cells of the liver (hepatocytes, cholangiocytes, and their bipotential progenitors) are heritably labeled at high efficiency with yellow fluorescent protein (YFP). Primary cholangiocytes isolated from our reporter strain were able to undergo EMT in vitro when treated with transforming growth factor-β1 alone or in combination with tumor necrosis factor-α, as indicated by adoption of fibroblastoid morphology, intracellular relocalization of E-cadherin, and expression of α-smooth muscle actin (α-SMA). To determine whether EMT occurs in vivo , we induced liver fibrosis in Alfp-Cre × Rosa26-YFP mice using the bile duct ligation (BDL) (2, 4, and 8 weeks), carbon tetrachloride (CCl4) (3 weeks), and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; 2 and 3 weeks) models. In no case did we find evidence of colocalization of YFP with the mesenchymal markers S100A4, vimentin, α-SMA, or procollagen 1α2, although these proteins were abundant in the peribiliary regions. Conclusion: Hepatocytes and cholangiocytes do not undergo EMT in murine models of hepatic fibrosis. (Hepatology 2011;)