Role of CD56-expressing immature biliary epithelial cells in biliary atresia

AIM: To analyze the clinical and pathological parameters and expression of the neural cell adhesion molecule(CD56) in patients with biliary atresia(BA).METHODS: Established clinical laboratory markers of hepatic function, including enzyme activity, protein synthesis, and bilirubin metabolism, were evaluated in patients with BA and compared with those in patients with choledochal cysts and neonatal hepatitis. Pathological changes in tissue morphology and fibrosis were examined by histological and tissue collagen staining. Immunohistochemical staining for the biliary epithelial cell markers CD56 and CK19 together with the Notch signaling related molecules Notch1 and Notch2 was performed in the context of alterations in the structure of intrahepatic biliary ducts.RESULTS: Differences in some clinical laboratoryparameters among the three diseases examined were observed, but they did not correlate with the pathological classification of fibrosis in BA. Immunohistochemical staining showed the presence of CD56-positive immature bile ducts in most patients(74.5%) with BA but not in patients with choledochal cysts or neonatal hepatitis. The number of CD56-expressing cells correlated with disease severity, with more positive cells present in the later stages of liver damage(81.8% vs 18.2%). Furthermore, bile plugs were mainly found in CD56-positive immature biliary ducts. Notch signaling was a key regulatory pathway in biliary duct formation and played a role in tissue fibrosis. Notch1 was co-expressed in CD56-positive cells, whereas Notch2 was found exclusively in blood vessels in the portal area of patients with BA. CONCLUSION: The maturation of biliary epithelial cells and the expression of Notch may play a role in the pathogenesis of BA.

Downregulation of Hes1 expression in experimental biliary atresia and its effects on bile duct structure

AIM To analyze the expression and function of the notchsignaling target gene Hes1 in a rhesus rotavirusinduced mouse biliary atresia model. METHODS The morphologies of biliary epithelial cells in biliary atresia patients and in a mouse model were examined by immunohistochemical staining. Then, the differential expression of Notch signaling pathway-related molecules was investigated. Further, the effects of the si RNAmediated inhibition of Hes1 expression were examined using a biliary epithelial cell 3 D culture system.RESULTS Both immature(Ep CAM+) and mature(CK19+) biliary epithelial cells were detected in the livers of biliary atresia patients without a ductile structure and in the mouse model with a distorted bile duct structure. The hepatic expression of transcripts for most Notch signaling molecules were significantly reduced on day 7 but recovered to normal levels by day 14, except for the target molecule Hes1, which still exhibited lower m RNA and protein levels. Expression of the Hes1 transcriptional co-regulator, RBP-Jκ was also reduced. A 3 D gel culture system promoted the maturation of immature biliary epithelial cells, with increased expression of CK19+ cells and the formation of a duct-like structure. The administration of Hes1 si RNA blocked this process. As a result, the cells remained in an immature state, and no duct-like structure was observed.CONCLUSION Our data indicated that Hes1 might contribute to the maturation and the cellular structure organization of biliary epithelial cells, which provides new insight into understanding the pathology of biliary atresia.