elastin and Biliary-Atresia

The extrahepatic bile duct is the primary tissue initially affected by biliary atresia. Biliary atresia is a cholangiopathy which exclusively affects neonates. Current animal models suggest that the developing bile duct is uniquely susceptible to damage. In this study, we aimed to define the anatomical and functional differences between the neonatal and adult mouse extrahepatic bile ducts.. We studied mouse passaged cholangiocytes, mouse BALB/c neonatal and adult primary cholangiocytes, as well as isolated extrahepatic bile ducts, and a collagen reporter mouse. The methods used included transmission electron microscopy, lectin staining, immunostaining, rhodamine uptake assays, bile acid toxicity assays, and in vitro modeling of the matrix.. The cholangiocyte monolayer of the neonatal extrahepatic bile duct was immature, lacking the uniform apical glycocalyx and mature cell-cell junctions typical of adult cholangiocytes. Functional studies showed that the glycocalyx protected against bile acid injury and that neonatal cholangiocyte monolayers were more permeable than adult monolayers. In adult ducts, the submucosal space was filled with collagen I, elastin, hyaluronic acid, and proteoglycans. In contrast, the neonatal submucosa had little collagen I and elastin, although both increased rapidly after birth. In vitro modeling of the matrix suggested that the composition of the neonatal submucosa relative to the adult submucosa led to increased diffusion of bile. A Col-GFP reporter mouse showed that cells in the neonatal but not adult submucosa were actively producing collagen.. We identified 4 key differences between the neonatal and adult extrahepatic bile duct. We showed that these features may have functional implications, suggesting the neonatal extrahepatic bile ducts are particularly susceptible to injury and fibrosis.. Biliary atresia is a disease that affects newborns and is characterized by extrahepatic bile duct injury and obstruction, resulting in liver injury. We identify 4 key differences between the epithelial and submucosal layers of the neonatal and adult extrahepatic bile duct and show that these may render the neonatal duct particularly susceptible to injury.

Topics: Animals; Animals, Newborn; Bile Ducts, Extrahepatic; Biliary Atresia; Cell Survival; Cells, Cultured; Collagen Type I; Collagen Type I, alpha 1 Chain; Disease Models, Animal; Elastin; Epithelial Cells; Female; Green Fluorescent Proteins; Humans; Hyaluronic Acid; Immunohistochemistry; Intercellular Junctions; Male; Mice; Mice, Inbred BALB C; Microscopy, Electron, Transmission; Mucous Membrane; Proteoglycans

Fibrillin-1, one of the main constituents of microfibrils, is present in normal adult liver and overexpressed in fibrotic area around cirrhotic nodules and hepatocellular carcinoma. In this work fibrillin-1 expression was studied by immunohistochemistry in liver samples from children with various cholestatic diseases corresponding to paucity of intrahepatic bile ducts, biliary atresia, congenital hepatic fibrosis, Byler's disease, mitochondrial cytopathy, sclerosing cholangitis, or choledochal cyst. As controls, histologically normal liver samples were used. In control liver, as in adult, fibrillin-1 was expressed in vessel walls, sinusoids, and portal connective tissue, particularly at the interface with the limiting hepatocytic plate and close to the basement membrane of bile ducts. In paucity of intrahepatic bile ducts without fibrosis, the fibrillin-1 distribution was similar to controls. In cholestatic diseases associated with severe fibrosis, such as biliary atresia, congenital hepatic fibrosis, Byler's disease, mitochondrial cytopathy, or sclerosing cholangitis, an enhanced deposition of fibrillin-1 was observed in portal connective tissue and fibrous septa. The strong fibrillin-1 expression close to the basement membrane of biliary structures was lost in cholestatic diseases, except biliary atresia. Finally, in normal and pathologic tissues, fibrillin-1 was co-localized with its putative receptor alphaVbeta3 in sinusoids but not around biliary structures.

Topics: Actins; Adolescent; Bile Ducts, Intrahepatic; Biliary Atresia; Child; Child, Preschool; Cholestasis; Collagen Type I; Collagen Type IV; Elastin; Fibrillin-1; Fibrillins; Fibrosis; Fluorescent Antibody Technique; Humans; Immunohistochemistry; Infant; Infant, Newborn; Laminin; Liver; Microfilament Proteins; Receptors, Vitronectin