EpCAM inhibits differentiation of human liver progenitor cells into hepatocytes in vitro by activating Notch1 signaling

New and Old Key Players in Liver Cancer

Liver cancer represents a major health problem worldwide with growing incidence and high mortality, hepatocellular carcinoma (HCC) being the most frequent. Hepatocytes are likely the cellular origin of most HCCs through the accumulation of genetic alterations, although hepatic progenitor cells (HPCs) might also be candidates in specific cases, as discussed here. HCC usually develops in a context of chronic inflammation, fibrosis, and cirrhosis, although the role of fibrosis is controversial. The interplay between hepatocytes, immune cells and hepatic stellate cells is a key issue. This review summarizes critical aspects of the liver tumor microenvironment paying special attention to platelets as new key players, which exert both pro- and anti-tumor effects, determined by specific contexts and a tight regulation of platelet signaling. Additionally, the relevance of specific signaling pathways, mainly HGF/MET, EGFR and TGF-β is discussed. HGF and TGF-β are produced by different liver cells and platelets and regulate not only tumor cell fate but also HPCs, inflammation and fibrosis, these being key players in these processes. The role of C3G/RAPGEF1, required for the proper function of HGF/MET signaling in HCC and HPCs, is highlighted, due to its ability to promote HCC growth and, regulate HPC fate and platelet-mediated actions on liver cancer.

Liver Pathology, Including MOC31 Immunohistochemistry, in Congenital Tufting Enteropathy

Congenital tufting enteropathy (CTE) is a rare heritable cause of intractable diarrhea due to EPCAM mutation. Pathologic findings include intestinal villous atrophy, tufted discohesive tear-drop-shaped epithelium, and a normal brush border. In affected patients, absent intestinal epithelial cell adhesion molecule (EpCAM) expression results in loss of MOC31 immunostaining. CTE liver pathology has not yet been described. We identified CTE patients with liver biopsies and reviewed clinicopathologic material including MOC31 immunohistochemistry. Three CTE patients had 4 liver core biopsies (at ages 1, 5, 7, and 16 y), 2 for preintestinal transplant evaluation, and 2 (from a single patient) for pretreatment assessment of chronic hepatitis C; all had received parenteral nutrition (PN). All samples showed loss of biliary epithelial polarization and mild portal and lobular inflammation. Only the hepatitis C patient demonstrated fibrosis. One patient each had lobular neutrophilic microabscesses and macrovesicular steatosis. Proliferative ductular reactions were absent in CTE patients but present in all controls on PN for other reasons. MOC31 was absent in biliary epithelium and hepatocytes of all CTE patients; controls showed consistent strong membranous biliary epithelial and patchy membranous periportal hepatocyte staining. Our data show that, histologically, hepatopathy in CTE can be difficult to separate from comorbid disease including PN effect; however, the absent ductular reaction may be characteristic. MOC31 localization in the biliary epithelium and zone 1 hepatocytes of controls suggests these compartments of the liver might be most susceptible to effects of EpCAM deficiency. In addition, we validate the liver as suitable tissue for CTE diagnosis using MOC31 immunohistochemistry.

Chemical-based primary human hepatocyte monolayer culture for the study of drug metabolism and hepatotoxicity: Comparison with the spheroid model

Traditionally cultured monolayers of primary human hepatocytes (PHHs) deteriorate within days and thereby become unsuitable for drug-related studies. PHH spheroids (3D PHHs) maintain liver functions for weeks, but are considerably more demanding. Recently, a chemical-based approach (5C PHHs) succeeded in long-term culture of hepatocyte monolayers, but it remains unclear whether the drug-related functions are preserved. To clarify this, we compared the 5C and 3D PHHs in terms of gene expression analysis, proteomic analysis, functionality (basal and induced activities of representative CYP450 enzymes and urea and albumin secretions), survival in culture, and sensitivity to representative drugs. In all comparisons, which spanned culture durations of up to 4 weeks, the 5C PHHs performed at least as well as the 3D PHHs. Hence, the novel 5C PHH monolayer format combines the convenience of the traditional monolayer format with the functionality and maintainability of the spheroid format. Our results suggest that 5C PHH monolayers can be used more conveniently and efficiently for high-throughput drug screening, preclinical drug safety evaluations, and mechanistic studies.

Hepatogenic Potential and Liver Regeneration Effect of Human Liver-derived Mesenchymal-Like Stem Cells

Human liver-derived stem cells (hLD-SCs) have been proposed as a possible resource for stem cell therapy in patients with irreversible liver diseases. However, it is not known whether liver resident hLD-SCs can differentiate toward a hepatic fate better than mesenchymal stem cells (MSCs) obtained from other origins. In this study, we compared the differentiation ability and regeneration potency of hLD-SCs with those of human umbilical cord matrix-derived stem cells (hUC-MSCs) by inducing hepatic differentiation. Undifferentiated hLD-SCs expressed relatively high levels of endoderm-related markers (GATA4 and FOXA1). During directed hepatic differentiation supported by two small molecules (Fasudil and 5-azacytidine), hLD-SCs presented more advanced mitochondrial respiration compared to hUC-MSCs. Moreover, hLD-SCs featured higher numbers of hepatic progenitor cell markers on day 14 of differentiation (CPM and CD133) and matured into hepatocyte-like cells by day 7 through 21 with increased hepatocyte markers (ALB, HNF4A, and AFP). During in vivo cell transplantation, hLD-SCs migrated into the liver of ischemia-reperfusion injury-induced mice within 2 h and relieved liver injury. In the thioacetamide (TAA)-induced liver injury mouse model, transplanted hLD-SCs trafficked into the liver and spontaneously matured into hepatocyte-like cells within 14 days. These results collectively suggest that hLD-SCs hold greater hepatogenic potential, and hepatic differentiation-induced hLD-SCs may be a promising source of stem cells for liver regeneration.