HUMAN BILIARY TREE STEM/PROGENITOR CELLS (hbTSCS) FROM PERIBILIARY GLANDS (PBGS) OF ADULT LIVER DISPLAY IMMUNOMODULATORY PROPERTIES THROUGH Fas/Fas LIGAND INDUCED T-CELL LYMPHOCYTE APOPTOSIS

Background and Aims: hBTSCs have the potential for regenerative medicine in liver and pancreas diseases. T-cell control was recently demonstrated for mesenchymal stem cells. The aims of this study were to evaluate Fas-L expression within the stem cell niches of adult biliary tree (PBGs), and to study the interaction between hBTSCs and human lymphocytes. Methods: HLA antigens, Fas and Fas-L expression were evaluated by immunofluorescence and western blotting (WB) in cells of human biliary tree in comparison with fibroblast cells, dental pulp stem cells and bone marrow mesenchymal stem cells. The influence of hBTSCs on lymphocytes’ activation and apoptosis were assessed by co-culturing experiments. Results: Adult hBTSCs expressed both class I and class II HLA antigens, whereas fetal hBTSCs only class I HLA antigens. 10 to 30% of the hBTSCs in PBGs were positive for Fas-L. Fas-L+ cells were mostly located at the bottom of PBGs and co-expressed EpCAM (Epithelial-Cell-AdhesionMolecule) and proliferation marker (PCNA:Proliferating-CellNuclear-Antigen). Mature cells at the bile duct surface epithelium (mature cholangiocytes) were almost all negative for Fas-L. In culture experiments confocal microscopy demonstrated that Fas-L expression was restricted to EpCAM+/LGR5+ (a marker associated with endodermal stem cells) hBTSCs. WB confirmed that hBTSCs constitutively expressed high level of Fas-L which increased after co-culture with T-cells. FACS analysis reveled that activated CD4+ and CD8+ T-cells co-cultured with hBTSCs underwent to a massiveinduction of apoptosis. Fas receptor appeared over-expressed in T-cells co-cultured with hBTSCs respect to resting T-cells. Conclusions: Our data demonstrated that hBTSCs can induce “premature” apoptosis in T-cells trough the activation of Fas/Fas-L pathway