Establishment of isolation procedure of human hepatic stem cell and tissue engineering technique to reconstitute hepatic tissue using the stem cell.

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[Aim]ln this study, we first tried to establish the procedure for isolation ofhepatic stem cell from healthy human liver. Next, we examined whether the hepatic stem cell has potential to differentiate into hepatocyte, biliary epithelial cell, or pancreatic cell under tri-dimensional culture condition by using collagen gel developed by Akita Sumitomo Bakelite Co., Ltd. Finally, we aimed the clinical application of topo-organ reconstituted by the ex vivo transplantation of hepatic stem cell.[Achievements](1)We have established a liver epithelial cell line, designated hepatic stem like (HSL) cell, from nonparenchymal fraction of healthy rat liver.(2)The HSL cells are small with 20 μm in diameter and showed high nucleus/cytoplasm ratios. These cells expressed α-fetoprotein, but not albumin nor cytokeratin 19, indicating the cells have immature phenotype.(3)We cultured the HSL cells in collagen gels or with hepatic stellate cells to investigate their potential to differentiate. Consequently, both of culture conditions induced the HSL cells to express albumin, showing that the HSL cells are able to differentiate into mature cells.(4)Finally, we examined how we process the HSL cells to manifest the hepatic function in vivo. To this end, we transplanted the HSL cells which were mixed with collagen gel or embedded in collagen sponge into analbuminemic rats. As a result, analbuminemic rats that showed the increased levels of serum albumin were 67% in the rats transplanted the HSL cells with collagen gel and 57% in the rats with collagen sponge. This suggests that the transplanted HSL cells have differentiated into albumin producing cells and function as hepatocytes in vivo. The present study implies the possibility of clinical application of HSL cells.