Bile duct cell apoptosis is a rare event in primary biliary cirrhosis

Abstract

The frequency of apoptosis in bile duct cells of primary biliary cirrhosis is still unclear spanning from rare to 50% in the various reports. To study bile duct cell apoptosis in stage I primary biliary cirrhosis lesions. Nine stage I-II biopsies with a total number of 26 bile ducts of different sizes, selected from a larger series on the basis of the expression on serial frozen sections of HLA-DR and Fas antigens. Apoptosis was evaluated by a DNA fragmentation assay on frozen sections, according to the manufacturer's protocol and by expression of apoptosis related cytokeratin neoepitopes. Bile duct cell proliferation was assessed by MIB1 (Ki-67) expression. Apoptosis was frequently found in inflammatory cells of portal tracts and sinusoids. Apoptosis of hepatocytes was also systematically observed. Only 4 positive bile duct cells were found in 3 bile ducts from 3 biopsies. Quantitative evaluation was not attempted. Cholangiocyte proliferation was observed in the same ducts and occasionally in other biopsies. These data suggest that cholangiocyte death by apoptosis at the level of typical primary biliary cirrhosis lesions is a rare event, at least in early stages of the disease. The observed rate of proliferation was consistent with the rate of apoptosis.