Wnt/Beta‐Catenin Cooperates With Yap Signaling To Promote Hepatobiliary Repair In A Model Of Chronic Liver Injury

Abstract

Proliferation of atypical ductules and compensatory hepatocyte transdifferentiation to cholangiocytes is a hallmark of 3,5‐diethoxycarbonyl‐ 1, 4‐dihydro‐collidine (DDC) diet‐induced injury in mice. Because liver‐specific beta‐catenin conditional KO mice exhibit fewer proliferating ductules after DDC, we hypothesized that Wnt signaling plays a role in this process. To test this, WT animals on control and DDC diet were analyzed for Wnt expression. We found upregulation of 3 Wnts – 7a, 7b, and 10a – in the portal triad of DDC‐fed mice, as determined by tissue microdissection. Cell sorting showed expression of these three Wnts exclusively in the EpCAM+ cell compartment. Addition of Wnt7b and 10a to small cholangiocyte cell line induced proliferation in an autocrine manner, consistent with an increase in CK19+/Ki67+ cells after DDC. In contrast, direct co‐culture of Hek293 cells expressing recombinant Wnt7a significantly increased Sox‐9 gene expression in AML12 cells and primary hepatocytes. To elucidate the role of beta‐catenin in transdifferentiation, we analyzed liver‐specific transgenic (TG) ser45‐mutant b‐catenin‐expressing mice after DDC diet. Compared to WT, TG had significantly upregulated expression of EpCAM and CK19, and more Sox‐9+ hepatocytes. Further, Yap, which regulates liver cell fate, is increased in TG hepatocyte nuclei, concomitant with increased expression of Yap target genes. Thus, Wnt/beta‐catenin signaling cooperates with Yap pathway to regulate hepatobiliary repair after DDC injury.