Antigenic phenotypes expressed by stem-like liver epithelial cells after intraductal transplantation and by developing and regenerating bile ducts in the rat liver

Previous studies suggest a biliary origin for stem-like cells in normal adult and carcinogen treated rat liver. While hepatocytic differentiation of hepatic stem-like cells has been previously demonstrated, to date their capacity for biliary differentiation has only been implied. Assuming the biliary tree would offer a supportive environment for biliary differentiation, we have developed an intraductal transplantation model. At two days after ligation, the extrahepatic bile duct of Fischer rats expressing enzymatically inactive dipeptidyl peptidase IV (DPPIV) was decompressed, cannulated, injected with donor cells derived from syngeneic rats expressing enzymatically active DPPIV and religated. Using DPPIV as an endogenous or β-galactosidase (β-gal) as an exogenous donor cell marker, we have demonstrated the ability of the following cell lines to integrate into liver or pancreatic ducts and survive for up to 52 days: (1) BDE1.1, a continuous line of bile duct epithelial cells (BDEC); (2) primary BDEC isolates; (3) primary fetal liver isolates; (4) CDE6, an oval cell line isolated from a Fischer rat maintained for 6 weeks on a choline deficient diet containing 0.1% ethionine; (5) H5D, a hepatoma cell line and (6) WB-psi, a clonal β-gal positive WB-F344 cell line. Using intraductal transplantation in conjunction with transplantation by direct injection into the hepatic parenchyma, we have examined the bipotentiality of the WB-psi, and CDE6 cell lines. Immunocytochemical analysis of liver frozen sections from animals sacrificed up to 52 days after intraductal and 82 days after parenchymal transplantation of the three cell lines, led to the following observations: (1) BDE1.1 cells maintains a mature ductal phenotype after ductal integration; (2) CDE6 cells integrate into hepatic cords and ducts and acquire hepatocyte or ductal markers, respectively; (3) WB-psi undergo hepatocytic differentiation following integration into hepatic cords but display a more limited capacity for acquiring ductal markers following ductal integration. Based on these findings, we conclude that WB-psi show a greater restriction towards a hepatocytic lineage than CDE6 cells.