Notch-Hes1 signaling activation in Caroli disease and polycystic liver disease.

The Notch signaling pathway plays a key role in the morphogenesis of the biliary tree, but its involvement in cystic biliary diseases, such as Caroli disease (CD) and polycystic liver disease (PLD), has yet to be determined. Immunostaining was performed using liver sections of CD and PLD, and the results were compared with those of congenital hepatic fibrosis (CHF) and von Meyenburg complex (VMC). The expression of Notch receptor 1 (Notch1) was increased in the nuclei of biliary epithelial cells in all cases of CD and PLD, whereas it remained at a low level in CHF and VMC. In addition, Notch2 and Notch3 were preferably expressed in the nuclei of biliary epithelial cells of PLD. Accordingly, the Notch effector Hes1 was highly expressed in biliary epithelial cells of CD and PLD, and the cell proliferative activity was significantly higher in CD and PLD. The expression of the Notch ligand Delta-like 1 was significantly increased in biliary epithelial cells of CD and PLD, which may be causally associated with the nuclear overexpression of Notch1 and Hes1. These results indicate that aberrant activation of the Notch-Hes1 signaling pathway may be responsible for the progression of biliary cystogenesis in CD and PLD.

Ductal Plate Malformation in the Liver of Boxer Dogs: Clinical and Histological Features.

Ductal plate malformations (DPMs) represent developmental biliary disorders with a wide phenotypic spectrum. This study characterizes DPM in 30 Boxer dogs. Median age was 1.5 (range, 0.3-10.0) years, with 12 dogs <1 year. Clinical features included increased serum levels of liver enzymes (28), gastrointestinal signs (16), poor body condition (14), abdominal effusion (9), and hepatic encephalopathy (2). Additional malformations included gallbladder atresia (8), atrophied left liver (2), absent quadrate lobe with left-displaced gallbladder (1), portal vasculature atresia (left liver, 1), intrahepatic portosystemic shunt (1), and complex intrahepatic arteriovenous malformation (1). All dogs had portal tracts dimensionally expanded by a moderate-to-severe multiple small bile duct phenotype embedded in abundant extracellular matrix; 80% displayed variable portal-to-portal bridging. Quantitative analysis confirmed significantly increased fibrillar collagen and a 3-fold increased portal tract area relative to 6 Boxer and 10 non-Boxer controls. Biliary phenotype was dominated by tightly formed CK19-positive ductules, typically 10 to 15 µm in diameter, with 3 to >30 profiles per portal tract, reduced luminal apertures, and negative Ki-67 immunoreactivity. CK19-positive biliary epithelium intersected directly with zone 1 hepatocytes as a signature feature when considered with other DPM characteristics. Phenotypic variation included a multiple small bile duct phenotype (all dogs), predominantly thin-walled sacculated ducts (4), well-formed saccular ducts (4), and sacculated segmental, interlobular, and intralobular ducts (Caroli malformation, 2 dogs, one with bridging portal fibrosis). Histologic evidence of portal venous hypoperfusion accompanied increased biliary profiles in every case. We propose that this spectrum of disorders be referred to as DPM with appropriate modifiers to characterize the unique phenotypes.

Roles of myofibroblasts and notch and hedgehog signaling pathways in the formation of intrahepatic bile duct lesions in polycystic kidney rats.

Polycystic kidney (PCK) rats, an animal model of Caroli's disease, show a dilatation of intrahepatic bile ducts (IHBD) called "ductal plate malformation." Mesenchymal cells and the Notch and Hedgehog signaling pathways in portal tracts are reportedly involved in the normal development of IHBD, although there have been no studies on the roles of these signaling pathways in PCK rats. We immunohistochemically examined the expression of the molecules related to these signaling pathways in portal tracts. All molecules related to these signaling pathways expressed in portal tracts in Sprague Dawley (SD) rats (control) were also expressed in PCK rats. Mesenchymal cells (myofibroblasts) were frequently found in the connective tissue of portal tracts of 20 embryonic-day-old (E20D), 1-day-old (1D), and 1-week-old (1W) SD and PCK rats and were abundant in PCK rats. Interestingly, myofibroblasts almost disappeared at in both strains of 3W rats. Jagged1 was expressed in mesenchymal cells in portal tracts and was abundant in PCK rats. Double immunostaining showed that Jagged1-positive cells were myofibroblasts. Notch2 and HES1 were expressed in cholangiocytes of the bile ducts of both rats. Sonic Hedgehog was similarly expressed in the bile ducts of both rats. A well-balanced and time-sequential expression of the Notch and Hedgehog family in portal tracts might be essential for the normal development of IHBD in E20D to 1W SD rats, and an imbalanced interaction of these molecules, particularly increased Jagged1 expression in periductal and periportal myofibroblasts and Notch2 expressed in cholangiocytes, may be involved in the formation of bile duct lesions in PCK rats.

Biliary infection may exacerbate biliary cystogenesis through the induction of VEGF in cholangiocytes of the polycystic kidney (PCK) rat.

Cholangitis arising from biliary infection dominates the prognosis in Caroli's disease. To clarify the influences of bacterial infection on the biliary cystogenesis, in vivo and in vitro studies were performed using the polycystic kidney (PCK) rat as an animal model of Caroli's disease. Cholangitis became a frequent histological finding in aged PCK rats, and neovascularization around the bile ducts also increased in aged PCK rats. Immunohistochemistry revealed that expression of vascular endothelial growth factor (VEGF) was increased in PCK rat biliary epithelium. In vitro, PCK cholangiocytes overexpressed VEGF, and the supernatant of cultured PCK cholangiocytes significantly increased the proliferative activity, migration, and tube formation of cultured rat vascular endothelial cells. Stimulation with lipopolysaccharide (LPS) further induced VEGF expression in PCK cholangiocytes, which might be mediated by signaling pathways involving phosphatidylinositol 3-kinase (PI3K)-Akt and c-Jun N-terminal kinase (JNK). Both LPS and VEGF increased cell proliferative activity in PCK cholangiocytes, and siRNA against VEGF significantly reduced LPS-induced cell proliferation. Thus, LPS-induced overexpression of VEGF in the biliary epithelium may lead to hypervascularity around the bile ducts; concurrently, LPS and VEGF act as cell proliferation factors for cholangiocytes. Biliary infection may thus exacerbate biliary cystogenesis in PCK rats.

Monolobar ductal plate malformation disease of the liver.

We herein report a unique monolobar hepatic disease composed of Caroli's disease, peribiliary cysts, ductal plate malformations, peribiliary gland proliferation, hepatolithiasis, and portal phlebosclerosis with thrombi. A 73-year-old man underwent abdominal imaging, which revealed multiple segmental dilations of the left intrahepatic bile ducts. Polycystic kidney diseases were absent. Intrahepatic cholangiocarcinoma was suspected, and extended left lobectomy of the liver was preformed. Grossly, the hepatic left lobe was atrophic, and partly replaced by fibrous tissue. The intrahepatic bile ducts were dilated (Caroli's disease), and showed small calcium bilirubinate hepatoliths. Microscopically, the intrahepatic bile duct showed non-obstructive segmental dilations (Caroli's disease), numerous peribiliary cysts, numerous ductal plate malformations, proliferation of intrahepatic peribiliary glands, and calcium bilirubinate hepatolithiasis. Portal veins showed phlebosclerosis with thrombi. Immunohistochemically, the various biliary epithelial cells were positive for cytokeratin (CK) 7, 8, 18, and 19, and for MUC6 and CD10. They were negative for MUC2 and MUC5AC. The ductal plate malformations were positive for fetal biliary antigen MUC1, but other biliary cell types were negative for MUC1. The present case resembles 'monolobar Caroli's disease'. We believe that the present monolobular liver disease was congenital in origin.

Recent progress in the etiopathogenesis of pediatric biliary disease, particularly Caroli's disease with congenital hepatic fibrosis and biliary atresia.

Recent progress in elucidating the etiopathogenesis of pediatric biliary diseases, particularly Caroli's disease with congenital hepatic fibrosis (CHF) and biliary atresia (BA), is reviewed. The former is characterized by multiple saccular dilatations of the intrahepatic bile ducts. An animal model of this disease, the PCK rat, is being extensively studied. PCK rats and Calori's disease with CHF belong to autosomal recessive polycystic kidney disease (ARPKD) with ductal plate malformation. Mutations of PKHD1 have been identified in ARPKD, and fibrocystin, a product of PKHD1 located in the cilia of bile ducts is lacking in the pathologic intrahepatic bile ducts of ARPKD. Disordered cell kinetics, including apoptosis of biliary epithelial cells (BECs), may be significantly related to ductal plate malformation, and laminin and type IV collagen were immunohistochemically reduced in the basement membrane of intrahepatic bile ducts of ARPKD, and such a reduction is an additional factor for the dilatation of bile ducts. Abundant connective tissue growth factor retained diffusely in heparan sulfate proteoglycan in the fibrous portal tracts are responsible for non-resolving hepatic fibrosis. In addition, pathologic BECs of ARPKD may acquire mesenchymal features and participate in progressive hepatic fibrosis by producing extracellular matrix molecules. In an animal model of BA, an initial virus-induced, T-cell mediated autoimmune-mediated cholangiopathy has been reported. In human BA, virus-induced apoptosis of BECs by a TNF-related apoptosis-inducing ligand followed by the progressive obliteration of bile ducts is also suggested, and epithelial mesenchymal transition of BECs induced by viral infection may be involved in the fibrotic process in sclerosing cholangitis. However, the role of viral infections in the affected tissues is controversial. Comprehensive and analytical studies of ARPKD and BA using human materials and animal models may lead to the clarification of their etiopathogenesis and open the way for new therapeutic strategies.

Matrix proteins of basement membrane of intrahepatic bile ducts are degraded in congenital hepatic fibrosis and Caroli's disease.

Congenital hepatic fibrosis (CHF) and Caroli's disease are though to result from ductal plate malformation, and the basal laminar components play important roles in biliary differentiation during development. To clarify the involvement of basal laminar components in the ductal plate malformation, this study examined the immunohistochemical expression of laminin and type IV collagen in the livers of CHF and Caroli's disease. Using the polycystic kidney (PCK) rat, an animal model of Caroli's disease with CHF, in vivo and in vitro experiments were also performed. Immunostaining showed that basement membrane expression of laminin and type IV collagen around intrahepatic bile ducts was degraded in CHF, Caroli's disease, and the PCK rats. The degradation of laminin and type IV collagen around bile ducts was also observed in foci of cholangiocarcinoma in situ of Caroli's disease. In vitro, PCK cholangiocytes were found to overexpress plasminogen and a serine proteinase, the tissue-type plasminogen activator (tPA). When PCK cholangiocytes were cultured in Matrigel, the amounts of laminin and collagen in the gel were significantly reduced, and addition of alpha2-antiplasmin in the culture medium inhibited the degradation of laminin and collagen in Matrigel. These results suggest that biliary overexpression of plasminogen and tPA leads to the generation of excessive amounts of plasmin, and subsequent plasmin-dependent lysis of the extracellular matrix molecules may contribute to the biliary dysgenesis in CHF and Caroli's disease, including progressive cystic dilatation of the intrahepatic bile ducts in Caroli's disease. In addition, it is suggested that once cholangiocarcinoma in situ develops in the biliary epithelium of CHF and Caroli's disease, it tends to transform into invasive carcinoma, due to instability of the basement membrane of the bile ducts.

Interaction of Toll-like receptors with bacterial components induces expression of CDX2 and MUC2 in rat biliary epithelium in vivo and in culture.

The mechanism of transformation of biliary epithelium leading to intestinal metaplasia, which is significantly involved in biliary diseases, remains unclear. CDX2, an intestine-specific transcription factor, is thought to regulate intestinal mucin MUC2 (mucus core protein) expression. We took advantage of polycystic kidney (PCK) rats as a model of chronic suppurative cholangitis with intestinal metaplasia and of cultured biliary epithelial cells (BECs) from PCK rats to clarify the causal relation between bacterial components such as pathogen-associated molecular patterns (PAMPs) and the development of intestinal metaplasia of bile ducts. Histological, immunohistochemical, and in situ hybridization studies were conducted in PCK rat livers. In cultured BECs, CDX2 and MUC2 were expressed following treatment with PAMPs and inhibitors (anti-Toll-like receptor (TLR)2/TLR4 antibody, nuclear factor-kappaB (NF-kappaB) inhibitor MG132). Chronic suppurative cholangitis with intestinal metaplasia developed as the PCK rats aged, and intestinal metaplasia and aberrant CDX2 and MUC2 expression developed in parallel. Intraluminal bacteria and the expression of TLR2 and TLR4 in BECs were demonstrated in the bile ducts, showing chronic suppurative cholangitis. In cultured BECs, treatment with PAMPs induced upregulation of CDX2 and MUC2 expression, and this effect was abolished by pretreatment with anti-TLR2 and anti-TLR4 antibody and MG132. A knockdown of CDX2 by CDX2 small interfering RNA inhibited MUC2 expression in cultured BECs induced by PAMPs, and transfection of CDX2 expression vector induced MUC2 expression. In conclusion, bacterial components may induce upregulation of the CDX2 expression followed by MUC2 expression via TLR and the NF-kappaB system in cultured BECs, and could be related to the development of intestinal metaplasia of the bile ducts.

Polycystic kidney rat is a novel animal model of Caroli's disease associated with congenital hepatic fibrosis.

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.