INCREASED MUC6 APOMUCIN EXPRESSION IS A CHARACTERISTIC OF REACTIVE BILIARY EPITHELIUM IN CHRONIC VIRAL-HEPATITIS

The significance of bile ductular proliferation in the progression of various hepatobiliary diseases remains unclear. Increased expression o f MUC6 apomucin, a major gastric mucin, has previously been noticed in proliferating bile ductules in chronic viral hepatitis. The purpose o f the present study was to characterize MUC6 apomucin and mRNA express ion in 35 histologically 'normal livers', 47 livers with chronic viral hepatitis, 28 with primary biliary cirrhosis, and seven with extrahep atic biliary obstruction. MUC6 protein was expressed focally in cytopl asm and/or on the luminal surface of septal and interlobular bile duct s in normal and diseased livers. Bile ductules in normal livers rarely expressed MUC6 protein. The MUC6 expression intensified and spread in proliferating bile ductules and small bile ducts in chronic viral hep atitis and to a lesser degree in other diseases. In the former, the ex tent and degree of MUC6 expression paralleled the degree of active nec roinflammation. MUC6 mRNA expression resembled MUC6 protein expression in proliferating bile ductules and intralobular small biliary cells, suggesting increased transcription and synthesis of MUC6. In conclusio n, proliferating bile ductular cells express MUC6 apomucin in diseased liver, especially in chronic viral hepatitis with active necroinflamm ation. This secreted mucin may act as a cytoprotective agent and repre sent a phenotype of reactive biliary epithelium in chronic viral hepat itis. (C) 1998 John Wiley & Sons, Ltd.