EXPRESSION OF APOMUCINS IN THE INTRAHEPATIC BILIARY TREE IN HEPATOLITHIASIS DIFFERS FROM THAT IN NORMAL LIVER AND EXTRAHEPATIC BILIARY OBSTRUCTION

Mucin plays an important role in the development of hepatoliths, which are formed within the intrahepatic large bile ducts. To date, eight a pomucins, components of mucin, have been identified. The purpose of th is study is to characterize the expression of MUC1, MUC2, MUC3, MUC5, and MUC6 apomucins at both the protein and messenger RNA (mRNA) levels in the intrahepatic large bile ducts and peribiliary glands in 36 liv ers from patients with hepatolithiasis, in 25 livers from the patients with extrahepatic biliary obstruction, and in 23 histologically-norma l livers. MUC3 and MUC6 were constantly and focally expressed, respect ively, in the biliary epithelial cells in the intrahepatic large bile ducts in normal livers, extrahepatic biliary obstruction, and, also, h epatolithiasis. In hepatolithiasis, MUC1, MUC2, and MUC5 apomucins wer e also focally expressed in 33%, 64%, and 89%, respectively, of the la rge intrahepatic bile ducts examined, whereas such expression was infr equent in normal livers and in extrahepatic biliary obstruction. The m arkedly proliferated intramural and extramural peribiliary glands in h epatolithiasis frequently expressed MUC3 and MUC6 apomucins and focall y expressed MUC2 and MUC5 apomucins. All of the apomucins mRNA express ion, except that of MUC1, resembled each protein expression. In conclu sion, the characteristics of apomucins in the intrahepatic biliary tre e in hepatolithiasis differs from those in normal livers and extrahepa tic biliary obstructrion. Increased expression of gel-forming mucins, such as MUC5 and MUC2, could be involved in the formation and developm ent of hepatolithiasis.