In the liver, Hepatic stem/progenitor cells (HPCs or HpSCs) represent a resident stem/progenitor cell compartment located within the smaller branches of intrahepatic biliary tree. HPCs are bipotential stem cells characterized by 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 specific aims of the present project will be: i) to investigate the role of hepatic progenitor cells (HPCs) in the progression of Non-alcoholic Fatty Liver Diseases and its relationship with macrophage and myofibroblast pool; ii) to study the niche of Biliary Tree Stem Cells (BTSC) in peribiliary glands, in pancreatic duct glands, and in Brunner¿s Glands in duodenum; iii) to study the involvement of BTSCs in biliary damage during primary sclerosing cholangitis (PSC) and BTSC role in the pathogenesis of cholangiocarcinoma in primary sclerosing cholangitis patients.
Investigations on the mechanisms driving stem cell activation and differentiation in the course of liver diseases could help the development of potential therapeutic strategies triggering stem cell niches. A better knowledge on the patho-physiology of stem cell niche could help to optimize the strategies for stem cell isolation including, the best markers for cell sorting or the best portion of biliary tree , pancreatic ducts, or duodenum to be used for BTSC isolation.
The results obtained in the present project will elucidate the organization of stem/progenitor cell niches along the biliary tree and their role in the normal homeostasis and their response to pathologic conditions including the diseases of liver, biliary tract and pancreas.
In particular, the present project will characterize cellular cross-talk at the basis of NASH development and will elucidate the role of hepatic progenitor cells (HPCs) in the progression of Non-alcoholic Fatty Liver Diseases. Moreover, the present project will characterize the niche of Biliary Tree Stem Cells (BTSC) in peribiliary glands, in pancreatic duct glands and in Brunner's Glands in human normal biliary tree, pancreas, and duodenum; finally, the involvement of BTSCs in biliary damage during primary sclerosing cholangitis (PSC) and their possible role in the development of cholangiocarcinoma will be clarified.
The results coming out from specific objective #1 will assess the role of macrophage activation in the evolution of NASH and its relationship with the activation of HPC niche by the activation of WNT/beta-catenin pathway. Moreover, the investigation of patients treated with DHA will elucidate whether DHA modify macrophage polarization towards an anti-inflammatory phenotype and whether this modification could determine an up-regulation of WNT pathway. Finally, results obtained from patients who underwent BS will elucidate the role of adipokines and HPC in the modulation of liver damage, steatosis and inflammation during NAFLD. In all experiments, the cross-talk with fibrogenetic cells such as HSC will be studied with particular reference to fibrosis pathway. Finally, the expression of TRL4 and pNF-kB will be evaluated and the correlation with oxidative stress investigated. These data 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.
Moreover, the results that will be obtained from Specific objective #2 will: i) describe the distribution of Brunner's Glands (BGs) along the human duodenum; ii) elucidate whether BGs contain cells with the phenotype of stem/progenitor cells; iii) define where are located progenitor-like cells with the most primitive phenotype; iv) isolate BG stem cell and define their proliferative and differentiative capabilities. Our approach will compare the phenotype of stem cell population within the adult biliary tree, adult pancreatic ducts and duodenum and will define the relative proportion (and location) of the most primitive stem cells (e.g. those with co-localization of the pluripotency genes OCT4, NANOG, SOX2 in the nucleus of a cell). Assessing these points will be fundamental to the knowledge of stem cell niche and to optimize the strategies for stem cell isolation such as individuation of the best marker for cell sorting or of the best portion of biliary tree or pancreatic ducts from which isolate the BTSC. Moreover, we will develop methods for isolating stem cell from duodenum and characterized their potentiality as source of stem cell for endoderm organs. This point would be crucial for regenerative medicine of endodermal organs including the liver and the endocrine pancreas and could individuate novel cellular sources for the isolation of stem cells and their future applications in stem cell therapy.
Finally, the results coming out from specific objective #3 will clarify the pathophysiological role of cholangiocytes in PSC and whether BTSC are involved in the pathogenesis PSC and whether their activation/proliferation is involved in progression towards cholangiocarcinoma. Moreover, there results will be characterized 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.