Detection of apoptosis and expression of apoptosis-related proteins during human intrahepatic bile duct development

Abstract

We investigated apoptosis by nick end labeling and the expression of apoptosis-related proteins by immunohistochemistry in fetal development of human intrahepatic bile ducts and hepatocytes. During intrahepatic bile duct development, apoptosis was present at all stages, and its positive ratio was high in the remodeling ductal plate, moderate in the ductal plate, and relatively low in remodeled ducts. The cell proliferative activity as determined by proliferating cell nuclear antigen was also high in the remodeling ductal plate, and relatively low in the ductal plate and remodeled ducts. fas antigen and c-myc protein were constantly positive in the ductal plate, remodeling ductal plate and remodeled ducts. Bcl-2 protein was negative or faintly positive in the ductal plate and remodeling ductal plate, but was apparently positive in remodeled ducts. Lewisy as detected by the BM-1 antibody was present in the ductal plate, remodeling ductal plate, and remodeled ducts. p53 protein was not found in any cell types in the liver development. During hepatocyte development, many apoptotic and proliferating cell nuclear antigen-positive hepatocytes were noted. The developing hepatocytes expressed c-myc protein and fas antigen. Bcl-2 protein and Lewisy antigen were also weakly positive in the developing hepatocytes. These findings showed that balanced cell proliferation and apoptosis are involved in the normal development of intrahepatic bile ducts and hepatocytes, and suggest that c-myc protein, fas antigen, Bcl-2 protein, and Lewisy antigen modulate apoptosis of fetal intrahepatic biliary cells and hepatocytes, probably by stimulative (c-myc protein and fas and Lewisy antigens) or inhibitory (Bcl-2 protein) effects.