De novo formation of the biliary system by TGFβ-mediated hepatocyte transdifferentiation

Abstract

Transdifferentiation is a complete and stable change in cell identity that serves as an alternative to stem-cell-mediated organ regeneration. In adult mammals, findings of transdifferentiation have been limited to the replenishment of cells lost from preexisting structures, in the presence of a fully developed scaffold and niche. Here we show that transdifferentiation of hepatocytes in the mouse liver can build a structure that failed to form in development-the biliary system in a mouse model that mimics the hepatic phenotype of human Alagille syndrome (ALGS). In these mice, hepatocytes convert into mature cholangiocytes and form bile ducts that are effective in draining bile and persist after the cholestatic liver injury is reversed, consistent with transdifferentiation. These findings redefine hepatocyte plasticity, which appeared to be limited to metaplasia, that is, incomplete and transient biliary differentiation as an adaptation to cell injury, based on previous studies in mice with a fully developed biliary system. In contrast to bile duct development, we show that de novo bile duct formation by hepatocyte transdifferentiation is independent of NOTCH signalling. We identify TGFβ signalling as the driver of this compensatory mechanism and show that it is active in some patients with ALGS. Furthermore, we show that TGFβ signalling can be targeted to enhance the formation of the biliary system from hepatocytes, and that the transdifferentiation-inducing signals and remodelling capacity of the bile-duct-deficient liver can be harnessed with transplanted hepatocytes. Our results define the regenerative potential of mammalian transdifferentiation and reveal opportunities for the treatment of ALGS and other cholestatic liver diseases.

Hepatocyte‐Specific β‐Catenin Deletion During Severe Liver Injury Provokes Cholangiocytes to Differentiate Into Hepatocytes

“…Previous studies have demonstrated that transdifferentiated cells, such as hepatocyte‐derived BECs, may revert back to their original cell type when liver injury has abated . Alternatively, it has been shown that with persistent need for transdifferentiated cells, such as in mice that lack the intrahepatic biliary system, hepatocyte‐to‐BEC conversion is permanent and stable for life . To determine if BEC‐derived hepatocytes would persist and further repopulate the liver, KO2 mice were allowed to recover on normal diet for either 3 or 6 months after CDE diet (Fig.…”

Sox9 Is a Modifier of the Liver Disease Severity in a Mouse Model of Alagille Syndrome

“…Work in several mouse models has shown that the severe BD paucity resulting from impaired Notch signaling improves over time . Accordingly, we examined whether Jag1 +/− animals recover from biliary paucity with age.…”

“…Black waterproof ink (Higgins, Leeds, MA) was injected using a 3‐mL syringe attached to a 32‐gauge needle and the PE10 cannula. Liver was resected and dehydrated through a methanol series to benzyl alcohol benzyl benzoate 1:2 solution to clear liver for imaging . For details on rehydration and staining of the ink‐injected livers, see Supporting Materials.…”

From Hepatocyte to Cholangiocyte: The Remarkable Potential of Transdifferentiation to Treat Cholestatic Diseases

“…Although many investigations have shown the potential for transdifferentiation through in vitro studies, few have demonstrated transdifferentiation in vivo , as shown by Schaub et al, with hepatocytes transdifferentiating into cholangiocytes . As background, in the setting of cholestatic liver injury, hepatocytes can undergo biliary differentiation to form reactive ductules.…”