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

ABSTRACT: Liver regeneration after injury is normally mediated by proliferation of hepatocytes, although recent studies have suggested biliary epithelial cells (BECs) can differentiate into hepatocytes during severe liver injury when hepatocyte proliferation is impaired. We investigated the effect of hepatocyte-specific β-catenin deletion in recovery from severe liver injury and BEC-to-hepatocyte differentiation. To induce liver injury, we administered choline-deficient, ethionine-supplemented (CDE) diet to three different mouse models, the first being mice with deletion of β-catenin in both BECs and hepatocytes (Albumin-Cre; Ctnnb1^flox/flox mice). In our second model, we performed hepatocyte lineage tracing by injecting Ctnnb1^flox/flox ; Rosa-stop^flox/flox -EYFP mice with the adeno-associated virus serotype 8 encoding Cre recombinase under the control of the thyroid binding globulin promoter, a virus that infects only hepatocytes. Finally, we performed BEC lineage tracing via Krt19-Cre^ERT ; Rosa-stop^flox/flox -tdTomato mice. To observe BEC-to-hepatocyte differentiation, mice were allowed to recover on normal diet following CDE diet-induced liver injury. Livers were collected from all mice and analyzed by quantitative real-time polymerase chain reaction, western blotting, immunohistochemistry, and immunofluorescence. We show that mice with lack of β-catenin in hepatocytes placed on the CDE diet develop severe liver injury with impaired hepatocyte proliferation, creating a stimulus for BECs to differentiate into hepatocytes. In particular, we use both hepatocyte and BEC lineage tracing to show that BECs differentiate into hepatocytes, which go on to repopulate the liver during long-term recovery. Conclusion: β-catenin is important for liver regeneration after CDE diet-induced liver injury, and BEC-derived hepatocytes can permanently incorporate into the liver parenchyma to mediate liver regeneration.

SUBMITTER: Russell JO

PROVIDER: S-EPMC6351199 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Prolonged exposure of mice to diet containing 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) results in hepatobiliary injury, atypical ductular proliferation, oval cell appearance, and limited fibrosis. Previously, we reported that short-term ingestion of DDC diet by hepatocyte-specific ?-catenin conditional knockout (KO) mice led to fewer A6-positive oval cells than wildtype (WT) littermates. To examine the role of ?-catenin in chronic hepatic injury and repair, we exposed WT and KO mice to DDC for 80 and 150 days. Paradoxically, long-term DDC exposure led to significantly more A6-positive cells, indicating greater atypical ductular proliferation in KO, which coincided with increased fibrosis and cholestasis. Surprisingly, at 80 and 150 days in KO we observed a significant amelioration of hepatocyte injury. This coincided with extensive repopulation of ?-catenin null livers with ?-catenin-positive hepatocytes at 150 days, which was preceded by appearance of ?-catenin-positive hepatocyte clusters at 80 days and a few ?-catenin-positive hepatocytes at earlier times. Intriguingly, occasional ?-catenin-positive hepatocytes that were negative for progenitor markers were also observed at baseline in the KO livers, suggesting spontaneous escape from cre-mediated recombination. These cells with hepatocyte morphology expressed mature hepatocyte markers but lacked markers of hepatic progenitors. The gradual repopulation of KO livers with ?-catenin-positive hepatocytes occurred only following DDC injury and coincided with a progressive loss of hepatic cre-recombinase expression. A few ?-catenin-positive cholangiocytes were observed albeit only after long-term DDC exposure and trailed the appearance of ?-catenin-positive hepatocytes.In a chronic liver injury model, ?-catenin-positive hepatocytes exhibit growth and survival advantages and repopulate KO livers, eventually limiting hepatic injury and dysfunction despite increased fibrosis and intrahepatic cholestasis.

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

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