Cholangiocyte biology and cystic fibrosis liver disease

Cystic fibrosis (CF) is one of the most common inherited diseases in the white population. The disease results from mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR). How this gene defect leads to the clinical manifestations of the disease, however, is not entirely clear. CFTR functions as a Cl^-channel in the apical membrane of most secretory epithelia, including biliary epithelial cells, or cholangiocytes. In cholangiocytes, CFTR appears to be an important determinant of biliary secretion and bile flow. Additionally, recent evidence suggests that CFTR regulates other membrane transporters, channels, and proteins. Improving life expectancy has led to an increasing recognition of hepatobiliary complications from CF. The true prevalence of CF liver disease is unknown, but may affect up to 17-25% of CF patients. Clinical manifestations include hepatic steatosis, neonatal cholestasis, focal nodular cirrhosis, multilobular cirrhosis, and biliary tract complications. Why only a subset of CF patients develops severe liver disease and others with the same genotype do not is one of the many scientific curiosities of this disease. This review focuses on the function of CFTR in cholangiocytes with emphasis on ductular bile formation as well as the clinical consequences of abnormal CFTR, namely CF-associated liver disease. Data on the pathogenesis, prevalence, clinical course, and treatment of CF liver disease will be reviewed.