B iliary atresia (BA) is characterized by a progressive, inflammatory, and sclerosing cholangiopathy. Little is known about the etiology and pathogenesis of BA, but recent studies have demonstrated the presence of Reoviridae (type 3 reovirus and type C rotavirus) having a double-strand RNA (dsRNA) in liver tissue of patients with BA, although conflicting results have been reported. [1][2][3][4][5] Moreover, the infection of newborn Balb/cmice with Reoviridae including type A rhesus rotavirus and type 3 reovirus (Abney) leads to cholestasis and biliary obstruction resembling human BA. 6,7 However, the role of these viruses in the pathogenesis of cholangiopathies in patients with BA is still unknown.Toll-like receptors (TLRs) are innate immune-recognition receptors that recognize pathogen-associated molecular patterns (PAMPs), and TLR3 recognizes dsRNA including dsRNA viruses. 8 The stimulation of TLR3 by dsRNA transduces signals to activate the transcription factors nuclear factor-B (NF-B) and interferon regulatory factor 3 (IRF3) via Toll-interleukin-1 receptor do-

Caroli's disease (congenital intrahepatic biliary dilatation) associated with congenital hepatic fibrosis is an autosomal recessive polycystic kidney disease. Recently, the polycystic kidney (PCK) rat, a spontaneous mutant derived from a colony of Crj:CD rats with polycystic lesions in the liver and an autosomal recessive mode of inheritance, was reported. In the present study, the pathology of the hepatobiliary system and the biliary cell-kinetics were evaluated in fetuses (day 18 to 21 of gestation) and neonates and adults (1 day to 4 months after delivery) of PCK rats. Crj:CD rats were used as a control. Multiple segmental and saccular dilatations of intrahepatic bile ducts were first observed in fetuses at 19 days of gestation. The dilatation spread throughout the liver and the degree of dilatation increased with aging. Gross and histological features characterizing ductal plate malformation were common in the intrahepatic bile ducts. Overgrowth of portal connective tissue was evident and progressive after delivery. These features were very similar to those of Caroli's disease with congenital hepatic fibrosis. Proliferative activity in the biliary epithelial cells was greater in PCK rats than controls during the development. In contrast, the biliary epithelial apoptosis was less extensive in PCK rats than the controls until 1 week after delivery, but greater after 3 weeks, suggesting that the remodeling defect in immature bile ducts associated with the imbalance of cell kinetics plays a role in the occurrence of intrahepatic biliary anomalies in PCK rats. The PCK rat could be a useful and promising animal model of Caroli's disease with congenital hepatic fibrosis.

IL-6 expression is inversely related to cell proliferation and positively related to differentiation in cholangiocarcinoma.

Cluster of differentiation 1 (CD1) is a family of four distinct nonpolymorphic major histocompatibility complex class I-like molecules that can present microbial nonpeptide lipid antigens to T cells. Among the CD1 gene family, CD1d is found in a wide range of tissues including the intestine and liver, and has been proposed to play an important role in mucosal immunity. Primary biliary cirrhosis (PBC) is an immune-mediated liver disease involving the intrahepatic small bile ducts, which also belong to the mucosal immune system. In this study, we studied the expression of CD1d in patients with PBC and compared the data with those of patients with hepatic sarcoidosis, primary sclerosing cholangitis (

Polycystic kidney (PCK) rats exhibit a multiorgan cyst pathology similar to human autosomal recessive polycystic kidney disease, and are proposed as an animal model of Caroli's disease with congenital hepatic fibrosis (CHF). This study investigated the expression and function of selected components of the mitogen activated protein kinase (MAPK) pathway in cultured intrahepatic biliary epithelial cells (BECs) of PCK rats. Compared to the proliferative activity of cultured BECs of control rats, those of the PCK rats were hyperresponsive to epidermal growth factor (EGF). The increase in BEC proliferation was accompanied by overexpression of MAPK/extracellular signal-regulated protein kinase (ERK) kinase 5 (MEK5), and subsequent phosphorylation of ERK5 in vitro. The increased proliferative activity was significantly inhibited by the transfection of short interfering RNA against MEK5 mRNA. An EGF receptor tyrosine kinase inhibitor, gefitinib ("Iressa", ZD1839), also significantly inhibited the abnormal growth of cultured BECs of PCK rats. By contrast, treatment with PD98059 and U0126, inhibitors for MEK1/2, was less effective. These results suggest that the activation of the MEK5-ERK5 cascade plays a pivotal role in the biliary dysgenesis of PCK rats, and also provide insights into the pathogenesis of Caroli's disease with CHF. As the MEK5-ERK5 interaction is highly specific, it may represent a potential target of therapy.