Hepatic progenitor/oval cells appear in injured livers when hepatocyte proliferation is impaired. These cells can differentiate into hepatocytes and cholangiocytes and could be useful for cell and gene therapy applications. In this work, we studied progenitor/oval cell surface markers in the liver of rats subjected to 2-acetylaminofluorene treatment followed by partial hepatectomy (2-AAF/PH) by using rat
Hepatic repair is directed chiefly by the proliferation of resident mature epithelial cells. Further if predominant injury is to cholangiocytes, the hepatocytes can transdifferentiate to cholangiocytes to assist in the repair and vice versa as shown by various fate-tracing studies. However, the molecular bases of reprograming remain elusive. Using two models of biliary injury where repair occurs via cholangiocyte proliferation and hepatocyte transdifferentiation to cholangiocytes, we identify an important role of Wnt signaling. First we identify upregulation of specific Wnt proteins in the cholangiocytes. Next, using conditional knockouts of Wntless and Wnt co-receptors LRP5/6, transgenic mice expressing stable β-catenin, and in vitro studies, we show a role of Wnt signaling through β-catenin in hepatocyte to biliary transdifferentiation. Lastly, we show that specific Wnts regulate cholangiocyte proliferation but in a β-catenin-independent manner. Conclusion: Wnt signaling regulates hepatobiliary repair after cholestatic injury in both β-catenin dependent and independent manners.
Background & Aims The cause of hepatic failure in the terminal stages of chronic injury is unknown. Cellular metabolic adaptations in response to the microenvironment have been implicated to cellular breakdown. Methods To address the role of energy metabolism in this process we studied mitochondrial number, respiration, and functional reserve, as well as cellular adenosine-5′-triphosphate (ATP) production, glycolytic flux, and expression of glycolysis related genes in isolated hepatocytes from early and terminal stages of cirrhosis using a model that produces hepatic failure from irreversible cirrhosis in rats. To study the clinical relevance of energy metabolism in terminal stages of chronic liver failure, we analyzed glycolysis and energy metabolism related gene expression in liver tissue from patients at different stages of chronic liver failure according to Child-Pugh classification. Additionally, to determine whether the expression of these genes in early-stage cirrhosis (Child-Pugh Class A) is related to patient outcome, we performed network analysis of publicly available microarray data obtained from biopsies of 216 patients with hepatitis C-related Child-Pugh A cirrhosis who were prospectively followed up for a median of 10 years. Results In the early phase of cirrhosis, mitochondrial function and ATP generation are maintained by increasing energy production from glycolytic flux as production from oxidative phosphorylation falls. At the terminal stage of hepatic injury, mitochondria respiration and ATP production are significantly compromised, as the hepatocytes are unable to sustain the increased demand for high levels of ATP generation from glycolysis. This impairment corresponds to a decrease in glucose-6-phosphatase catalytic subunit and phosphoglucomutase 1. Similar decreased gene expression was observed in liver tissue from patients at different stages of chronic liver injury. Further, unbiased network analysis of microarray data revealed that these genes’ expression was down regulated in the group of patients with poor outcome. Conclusions An adaptive metabolic shift, from generating energy predominantly from oxidative phosphorylation to glycolysis, allows maintenance of energy homeostasis during early stages of liver injury, but leads to hepatocyte dysfunction during terminal stages of chronic liver disease because hepatocytes are unable to sustain high levels of energy production from glycolysis.
Glypican-3 (Gpc3), a cell surface-linked heparan sulfate proteoglycan is highly expressed during embryogenesis and is involved in organogenesis. Its exact biological function remains unknown. We have studied the expression of Gpc3 in fetal and adult liver, in liver injury models of activation of liver progenitor cells: D-galactosamine and 2-acetylaminofluorene (2-AAF) administration followed by partial hepatectomy (PH) (2-AAF/PH); and in the Solt-Farber carcinogenic model: by initiation with a single dose of diethylnitrosamine and promotion with 2-AAF followed by PH treatment. Gpc3 expression was studied using complementary DNA microarrays, reverse transcriptase-polymerase chain reaction, in situ hybridization (ISH); ISH combined with immunohistochemistry (IHC) and immunofluorescent microscopy. We found that Gpc3 is highly expressed in fetal hepatoblasts from embryonic days 13 through 16 and its expression gradually decreases towards birth. Dual ISH with Gpc3 and alpha-fetoprotein (AFP) probes confirmed that only hepatoblasts and no other fetal liver cells express Gpc3. At 3 weeks after birth the expression of Gpc3 mRNA and protein was hardly detected in the liver. Gpc3 expression was highly induced in oval cell of D-gal and 2-AAF/PH treated animals. Dual ISH/IHC with Gpc3 riboprobe and cytokeratin-19 (CK-19) antibody revealed that Gpc3 is expressed in activated liver progenitor cells. ISH for Gpc3 and AFP performed on serial liver sections also showed coexpression of the two-oncofetal proteins. FACS isolated oval cells with anti-rat Thy1 revealed expression of Gpc3. Gpc3 expression persists in atypical duct-like structures and liver lesions of animals subjected to the Solt-Farber model of initiation and promotion of liver cancer expressing CK-19. In this work we report for the first time that the oncofetal protein Gpc3 is a marker of hepatic progenitor cells and of early liver lesions. Our findings show further that hepatic progenitor/oval cells are the target for malignant transformation in the Solt-Farber model of hepatic carcinogenesis.
Background & Aim Considerable progress has been made in developing anti-fibrotic agents and other strategies to treat liver fibrosis; however, significant long-term restoration of functional liver mass has not yet been achieved. Therefore, we investigated whether transplanted hepatic stem/progenitor cells can effectively repopulate the liver with advanced fibrosis/cirrhosis. Methods Stem/progenitor cells derived from fetal livers or mature hepatocytes from DPPIV+ F344 rats were transplanted into DPPIV− rats with thioacetamide (TAA)-induced fibrosis/cirrhosis; rats were sacrificed 1, 2, or 4 months later. Liver tissues were analyzed by histochemistry, hydroxyproline determination, RT-PCR, and immunohistochemistry. Results After chronic TAA administration, DPPIV− F344 rats exhibited progressive fibrosis, cirrhosis and severe hepatocyte damage. Besides stellate cell activation, increased numbers of stem/progenitor cells (Dlk-1+, AFP+, CD133+, Sox-9+, FoxJ1+) were observed. In conjunction with partial hepatectomy (PH), transplanted stem/progenitor cells engrafted, proliferated competitively compared to host hepatocytes, differentiated into hepatocytic and biliary epithelial cells, and generated new liver mass with extensive long-term liver repopulation (40.8 ± 10.3%). Remarkably, more than 20% liver repopulation was achieved in the absence of PH, associated with reduced fibrogenic activity (e.g., expression of α-SMA, PDGFRβ, desmin, vimentin, TIMP1) and fibrosis (reduced collagen). Furthermore, hepatocytes can also replace liver mass with advanced fibrosis/cirrhosis, but to a lesser extent than FLSPCs. Conclusions This study is a Proof of Principle demonstration that transplanted epithelial stem/progenitor cells can restore injured parenchyma in a liver environment with advanced fibrosis/cirrhosis and exhibit anti-fibrotic effects.
Background & Aims Highly proliferative fetal liver stem/progenitor cells (FLSPC) repopulate livers of normal recipients by cell competition. We investigated the mechanisms by which FLSPC repopulate livers of older, compared with younger rats. Methods Fetal liver cells were transplanted from DPPIV+ F344 rats into DPPIV− rats of different ages (2, 6, 14, or 18 months); liver tissues were analyzed 6 months later. Cultured cells and liver tissues were analyzed by reverse transcription PCR, immunoblot, histochemistry, laser-capture microscopy, and TUNEL analyses. Results We observed 4–5-fold increases in liver repopulation when FLSPC were transplanted into older, compared with younger, rats. mRNA levels of cyclin-dependent kinase inhibitors increased progressively in livers of older rats; hepatocytes from 20-month old rats had 6.1-fold higher expression of p15INK4b and were less proliferative, in vitro, than hepatocytes from 2-month old rats. Expression of p15INK4b in cultured hepatocytes was upregulated by activin A, which increased in liver during aging. Activin A inhibited proliferation of adult hepatocytes, whereas FLSPC were unresponsive because they had reduced expression of activin receptors (e.g. ALK-4). In vivo, expanding cell clusters derived from transplanted FLSPC had lower levels of ALK-4 and p15INK4b and increased levels of Ki-67, compared with the host parenchema. Liver tissue of older rats had 3-fold more apoptotic cells than of younger rats. Conclusions FLSPC, resistant to activin A signaling, repopulate livers of older rats; hepatocytes in older rats have less proliferation, because of increased activin A and p15INK4b levels, and increased apoptosis than of younger rats. These factors and cell types might be manipulated to improve liver cell transplantation strategies in patients with liver diseases in which activin A levels are increased.
O ver the years, substantial evidence has accumulated demonstrating the existence of adult hepatic progenitor cells, also termed oval cells (OCs). When the regenerative capacity of terminally differentiated hepatocytes is exhausted or blocked, these cells are activated to proliferate and differentiate into hepatocytes and cholangiocytes. OCs sprout from the putative stem cell niche (canals of Hering), forming tortuous pseudoducts and invading the liver lobule. 1-6 These pseudoducts are in close proximity to desmin-positive stellate cells. 7 Recently, we found a population of activated mesenchymal cells, thymus cell antigen-1 (Thy-1)-expressing cells, surrounding OCs. These cells partially overlapped with the desmin-positive cells and produce inductive signals (growth factors and cytokines) in the OC niche. 8,9 Thy-1 is a cell surface glycophosphatidylinositollinked glycoprotein with a molecular mass of 35 kDa and is an adhesion molecule of the immunoglobulin super-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.