Lack of β‐catenin in Hepatocytes Impairs Proliferation and Promotes Liver Progenitor Cell‐Mediated Repair in Response to the Choline‐Deficient Ethionine‐Supplemented Diet
Authors: Russell Jacquelyn Olivia , Okabe Hirohisa , Singh Sucha , Poddar Minakshi , Abrams Marc , Nejak‐Bowen Kari , Monga Satdarshan Paul 
Published: November 2023

Despite the liver's capacity for regeneration, liver disease is the 12th leading cause of death in the United States. Treatments for chronic liver disease are limited due to incomplete understanding of liver regeneration mechanisms. Typically, liver regeneration is mediated by proliferation of hepatocytes. When hepatocyte proliferation is impaired, biliary‐derived liver progenitor cells (LPCs) are activated and are thought to mediate regeneration by differentiating into hepatocytes. However, the role and origin of LPCs remains controversial. The choline‐deficient ethionine‐supplemented (CDE) diet model of liver injury is known to induce proliferation of LPCs. However, the CDE diet does not block hepatocyte proliferation. β‐catenin signaling plays an important role in liver regeneration by promoting hepatocyte proliferation. Therefore, we hypothesized that β‐catenin loss in hepatocytes would impair hepatocyte proliferation and lead to biliary‐derived LPC‐mediated hepatic repair in the CDE diet model. Mice that lack β‐catenin in both hepatocytes and biliary epithelial cells (BECs) (KO1) display increased liver injury and defective hepatocyte proliferation when compared to wild‐type (WT) littermates after 2 weeks of CDE diet. To investigate whether liver regeneration is mediated by LPCs in this model, we performed genetic fate tracing in mice by utilizing adeno‐associated virus serotype 8 carrying thyroid binding globulin‐driven Cre (AAV8‐TBG‐Cre) to simultaneously delete β‐catenin and permanently label hepatocytes with EYFP (KO2 mice). Importantly, in this model BECs contain β‐catenin and do not express EYFP. When these mice were given two weeks of CDE diet they displayed increased liver injury and a lack of hepatocyte proliferation compared to β‐catenin WT littermates. Furthermore, we utilized GalXC‐CTNNB1, a drug containing anti‐β‐catenin small interfering RNA (siRNA) conjugated to a hepatocyte‐targeting ligand, to knockdown expression of β‐catenin specifically in hepatocytes (KO3 mice). KO3 mice also displayed notably increased liver injury and significantly impaired hepatocyte proliferation after two weeks of CDE diet. Finally, in KO2 mice given two weeks of CDE diet followed by a two week recovery on normal diet we detected clusters of hepatocytes which expressed β‐catenin and did not express EYFP, indicating that they originated from the BEC compartment. We did not observe expansion of EYFP‐negative hepatocytes in control mice where hepatocytes retained β‐catenin expression. Our results demonstrate that loss of β‐catenin in hepatocytes impairs hepatocyte proliferation after CDE diet‐induced liver injury and supports the hypothesis that LPCs mediate liver regeneration when hepatocyte proliferation is blocked.

Support or Funding Information

Funding was provided via the NIH CATER training grant T32 EB001026. Funding was additionally provided through the NIDDK via 5R01DK062277‐13. Support was provided by the Cellular & Molecular Pathology Graduate Program at the University of Pittsburgh.