Rapid increase of bile salt secretion is associated with bile duct injury after human liver transplantation

Background/Aims Biliary strictures are a serious cause of morbidity after liver transplantation. We have studied the role of altered bile composition as a mechanism of bile duct injury after human liver transplantation. Methods In 28 liver transplant recipients, bile samples were collected daily posttransplantation for determination of bile composition. Hepatic expression of bile transporters was studied before and after transplantation. Histopathological criteria as well as biliary concentrations of alkaline phosphatase (ALP) and γ-glutamyltransferase (γ-GT) were used to quantify bile duct injury. Results Early after transplantation, bile salt secretion increased more rapidly than phospholipid secretion, resulting in high biliary bile salt/phospholipid ratio (BA/PL). In parallel with this, mRNA levels of the bile salt transporters NTCP and BSEP increased significantly after transplantation, whereas phospholipid translocator MDR3 mRNA levels remained unchanged. Bile duct injury correlated significantly with bile salt secretion and was associated with a high biliary BA/PL ratio. Conclusions Bile salt secretion after human liver transplantation recovers more rapidly than phospholipid secretion. This results in cytotoxic bile formation and correlates with bile duct injury. These findings suggest that endogenous bile salts have a role in the pathogenesis of bile duct injury after liver transplantation.