Isolation and characterization of stem/progenitor cells from adult human liver and evaluation of their hepatic repopulation after transplantation

Stem/progenitor cells from various intra or extra-hepatic sources have been isolated and studied in vitro and in vivo since long time. However, wide clinical application still remains so far because there are still many disagreements around their efficacy and long-term safety. The most logical source of stem/progenitor cells for liver disease treatment is the liver itself. In our study, emergence and proliferation of liver stem/progenitor cells was revealed after progressive death and detachment of primary isolated hepatocytes in vitro. Besides small hepatocytes - widely documented in the literature, the current thesis work allowed the isolation and the characterization of two original cell types with epithelial (liver epithelial-like cells or LECs) and mesenchymal (Adult derived human liver stem cells or ADHLSCs) phenotypes. We were not able to maintain small hepatocytes after trypsin application, reason why in vivo studies were not conducted. In contrary, LECs were isolated by direct trypsin application on their initial small colonies. The homogenous sub-culture of LECs spontaneously differentiated into hepatocytes and/or biliary cells, significantly altering their long-term survival in vitro. ADHLSCs were highly proliferative and could be cultivated for many passages at undifferentiated state. Their hepatogenic differentiation was inducible using specific condition media. These particularities make ADHLSCs more useful than small hepatocytes and LECs in large-scale production settings. Therefore, the major investigations of the current thesis work have been focused on ADHLSCs to evaluate their potential translation use for liver cell based therapy development.(MED 3) -- UCL, 201