hepatocyte-specific-ablation-zebrafish-to-study-biliary-driven-liver

Hepatocyte-specific Ablation in Zebrafish to Study Biliary-driven Liver Regeneration

The liver has a great capacity to regenerate. Hepatocytes, the parenchymal cells of the liver, can regenerate in one of two ways: hepatocyte- or ...

University of Pittsburgh

Wnt/β-catenin signaling plays multiple roles in liver development including hepatoblast proliferation and differentiation, hepatocyte differentiation, and liver zonation. A positive role for Wnt/β-catenin signaling in liver specification was recently identified in zebrafish; however, its underlying cellular mechanisms are unknown. Here, we present two cellular mechanisms by which Wnt/β-catenin signaling regulates liver specification. First, using lineage tracing we show that ectopic hepatoblasts, which form in the endoderm posterior to the liver upon activation of Wnt/β-catenin signaling, are derived from the direct conversion of non-hepatic endodermal cells, but not from the posterior migration of hepatoblasts. We found that endodermal cells at the 4-6(th) somite levels, which normally give rise to the intestinal bulb or intestine, gave rise to hepatoblasts in Wnt8a-overexpressing embryos, and that the distribution of traced endodermal cells in Wnt8a-overexpressing embryos was similar to that in controls. Second, by using an endoderm-restricted cell-transplantation technique and mosaic analysis with transgenic lines that cell-autonomously suppress or activate Wnt/β-catenin signaling upon heat-shock, we show that Wnt/β-catenin signaling acts cell-autonomously in endodermal cells to induce hepatic conversion. Altogether, these data demonstrate that Wnt/β-catenin signaling can induce the fate-change of non-hepatic endodermal cells into a liver fate in a cell-autonomous manner. These findings have potential application to hepatocyte differentiation protocols for the generation of mature hepatocytes from induced pluripotent stem cells, supplying a sufficient amount of hepatocytes for cell-based therapies to treat patients with severe liver diseases.

Wnt/β-catenin signaling cell-autonomously converts non-hepatic endodermal cells to a liver fate.

Hepatocellular carcinoma (HCC), the third most common cause of cancer-related deaths worldwide, lacks effective medical therapy. Large subsets of HCC demonstrate Wnt/β-catenin activation, making this an attractive therapeutic target. We report strategy and characterization of a novel small-molecule inhibitor, ICG-001, known to affect Wnt signaling by disrupting β-catenin-CREB binding protein interactions. We queried the ZINC online database for structural similarity to ICG-001 and identified PMED-1 as the lead compound, with ≥70% similarity to ICG-001. PMED-1 significantly reduced β-catenin activity in hepatoblastoma and several HCC cells, as determined by TOPflash reporter assay, with an IC50 ranging from 4.87 to 32 μmol/L. Although no toxicity was observed in primary human hepatocytes, PMED-1 inhibited Wnt target expression in HCC cells, including those with CTNNB1 mutations, and impaired cell proliferation and viability. PMED-1 treatment decreased β-catenin-CREB binding protein interactions without affecting total β-catenin levels or activity of other common kinases. PMED-1 treatment of Tg(OTM:d2EGFP) zebrafish expressing GFP under the β-catenin/Tcf reporter led to a notable decrease in β-catenin activity. The PMED effect on β-catenin signaling lasted from 12 to 24 hours in vitro and 6 to 15 hours in vivo. Thus, using a rapid and cost-effective computational methodology, we have identified a novel and specific small-molecule inhibitor of Wnt signaling that may have implications for HCC treatment.

Juhoon So

Department of Developmental Biology,
McGowan Institute for Regenerative Medicine,
Department of Developmental Biology, McGowan Institute for Regenerative Medicine

University of Pittsburgh

Hepatocyte-specific Ablation in Zebrafish to Study Biliary-driven Liver Regeneration

Juhoon So

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Developmental Biology,McGowan Institute for Regenerative Medicine,Department of Developmental Biology, McGowan Institute for Regenerative Medicine

University of Pittsburgh

Hepatocyte-specific Ablation in Zebrafish to Study Biliary-driven Liver Regeneration

Department of Developmental Biology,
McGowan Institute for Regenerative Medicine,
Department of Developmental Biology, McGowan Institute for Regenerative Medicine