The gallbladder: innocent bystander or major factor in cholesterol-gallstone formation?

Cholesterol gallstone disease: focusing on the role of gallbladder

Gallstone disease (GSD) is one of the most common biliary tract diseases worldwide in which both genetic and environmental factors have roles in its pathogenesis. Biliary cholesterol supersaturation from metabolic defects in the liver is traditionally seen as the main pathogenic factor. Recently, there have been renewed investigative interests in the downstream events that occur in gallbladder lithogenesis. This article focuses on the role of the gallbladder in the pathogenesis of cholesterol GSD (CGD). Various conditions affecting the crystallization process are discussed, such as gallbladder motility, concentrating function, lipid transport, and an imbalance between pro-nucleating and nucleation inhibiting proteins.

Gallbladder histopathology during murine gallstone formation: relation to motility and concentrating function

C57L mice are susceptible and AKR mice are resistant to gallstone formation. We studied in male mice of both strains gallbladder histopathology, cholecystokinin-induced emptying, and concentrating function at 0, 14, 28, and 56 days on a lithogenic diet. Gallbladder wall thickness increased on the diet, with stromal granulocyte infiltration, progressive fibrosis, edema, and epithelial cell indentation, particularly in C57L. Strong basal cholecystokinin octapeptide-induced gallbladder emptying (70% of fasting volumes) occurred in both strains, but fasting gallbladder volumes were significantly larger in C57L (14.8 +/- 2.2 microl vs. 8.8 +/- 1.0 microl). On the diet, fasting volumes increased exclusively in C57L (28.6 +/- 2.9 microl on day 56), with progressively decreased emptying (27% of fasting volumes on day 56). Gallbladder emptying remained normal in AKR. Gallbladder concentrating function decreased on the lithogenic diet (especially in C57L), coinciding with decreased aquaporin-1 (AQP1) and AQP8 expression at the mRNA and protein levels. In additional experiments, similar downregulation of AQP1 and AQP8 mRNA expression occurred in farnesoid X receptor (FXR)-deficient mice after 1 week on the lithogenic diet, without any difference from corresponding wild-type mice. In conclusion, during murine lithogenesis, altered gallbladder histology is associated with impaired motility, reduced concentrating function, and decreased AQP1 and AQP8 expression, the latter without the involvement of the FXR.