In the liver, hepatic stem/progenitor cells (HPCs or HpSCs) represent a facultative stem/progenitor cell compartment located within the smaller branches of intrahepatic biliary tree. HPCs are bipotential stem cells characterized by the capability to differentiate towards mature hepatocytes and cholangiocytes. In different chronic human liver diseases, HPCs activate and proliferate as a consequence of impaired proliferation of mature parenchymal liver cells by a variety of insults. Beside the HPC niche, endoderm-like stem cells have been recently described within extrahepatic and large intrahepatic bile ducts. These Biliary Tree Stem Cells (BTSCs) are located within peribiliary glands.
The general aim of the present project will be to investigate the role of hepatic and biliary tree stem cells in human pathologies and the activation of specific signaling pathways. Specific objectives of the present project will be: i) to investigate the activation of hepatic progenitor cells (HPCs) in the progression of Non-Alcoholic Fatty Liver Diseases (NAFLD) and the relationship with levels of Lipopolysaccharide (LPS) and adipokines; ii) to study the signaling pathways driving the stem cell activation in human cholangiopathies; iii) to individuate the role of peribiliary glands (PBGs) in the pathogenesis of biliary strictures after liver transplantation and in the development of cholangiocarcinoma (CCA) in Primary Sclerosing Cholangitis (PSC).
Data that will be obtained from this the project will be useful to understand cellular mechanisms at the basis of NAFLD and cholangiopathy progression and could individuate novel molecular tools and cellular target for therapeutic approaches. Investigations on the mechanisms driving stem cell activation and differentiation in liver diseases could help the development of potential therapeutic strategies triggering stem cell niches.
The present project will clarify important aspects on the activation of hepatic progenitor cells (HPCs) within the liver and the organization of stem/progenitor cell niches along the biliary tree, by the examination of their role in the response to pathologic conditions, including the diseases of liver and biliary tract.
The objective #1 of the present project will characterize cellular cross-talk at the basis of NASH development. In particular, the results coming from this specific objective will assess the contribution of macrophage activation in the evolution of NASH and its relationship with the activation of HPC niche. Moreover, the possible role of WNT/beta-catenin pathway will be elucidated in this cellular cross-talk and specific clinical setting (i.e. NAFLD). Moreover, the investigation of patients who underwent Bariatric Surgery (BS) will individuate the histo-pathological modifications due to weight loss in term of liver histology and HPC niche activation; the parallel investigation in the same patients of visceral adipose tissue will be useful to individuate parallel changes in the liver and adipose tissue after BS. In term of molecular target, this study will provide information about the pathogenetic role of LPS and the concomitant presence of TLR4 positive macrophages and pNF-kB activation in NASH development. This will have interesting implications regarding the clinical association between liver-gut axis and NAFLD. Furthermore, the modification in hepatic adipokine production will be studied in the context of NASH progression and after BS and eventual cross-talk between adipose tissue and the liver. The correlation of histological aspects with serum levels of LPS and inflammatory cytokines will furnish clinical information and, in general, data obtained from this part of the project will be useful to understand cellular mechanisms at the basis of NAFLD progression and could individuate novel molecular tools and cellular target for therapeutic approaches.
The objective #2 of the present project will further clarify the role of HPCs in the progression of cholangiopathies. In particular, the eventual correlation of progenitor cell activation with cholangiocyte loss and fibrosis will be established. Moreover, these aspects will be associated with clinical prognostic validated score and with clinical model to predict the response to therapy. Thus, results coming from this part of the project would individuate pathological basis of treatment failure by exploring the physio-pathology of hepatic progenitor cells and their involvement in PSC and PBC. Moreover, the signaling pathway involved in progenitor cell activation will be dissected and this information could furnish information on possible molecular targets in these diseases.
Finally, the present project will characterize the niche of Biliary Tree Stem Cells (BTSC) in peribiliary glands and the role of BTSCs in primary sclerosing cholangitis (PSC), in biliary complications after transplantation, and in the development of cholangiocarcinoma. To this regard, the results coming from specific objective #3 will clarify the pathophysiological role of cholangiocytes in PSC and whether BTSC are involved in the pathogenesis of PSC and whether their activation/proliferation is involved in progression towards cholangiocarcinoma. Moreover, this study will characterize the spectrum of progressive lesions from the inflammation of biliary tree, the bile duct fibrosis, and biliary malignancies; our results will describe the morpho-pathological features of cholangiocarcinoma arising in PSC patients. Finally, the role of epithelial to mesenchymal transition, autophagy, VEGF, and hedgehog pathway will be investigated as a marker for the progression and prognosis of this disease.
Thus, our project will further characterize pathogenetic mechanisms underlying biliary complications in transplanted organs and assess whether they are related to ischemia. Biliary complications after liver transplantation represent a major cause for re-transplantation, with a reported incidence varying between 5% and 30%; therefore, the study of their pathogenesis would be crucial to individuate possible prognostic and clinical target. Thus, our results would clarify whether the high incidence of biliary complications associated with transplantation of livers donated after cardiac death (DCD) could be due to defect in biliary tree stem cells and peribiliary glands. Finally, the correlation of histological study with clinical and surgical parameters will unravel whether a proper activation of PBG niche both in term of degree and commitment would be necessary for regenerating surface epithelium defect due to transplantation procedure.