8, 9 In a microarray analysis of liver tissue from infants with a so-called embryonic form of biliary atresia in which extrahepatic malformations and early onset of cholestatic jaundice occur, a unique pattern of expression of genes involved in chromatin integrity and function and overexpression of five imprinted genes was found, HM781-36B concentration implying a failure to down-regulate embryonic gene programs that influence the development of the liver and other organs.10 Heterozygous CFC1 (encoding the cryptic protein) mutations have been rarely associated with biliary atresia and polysplenia, and therefore may represent a genetic predisposition to this pattern of malformations.11 So what

can the sea lamprey tell us about the human condition? It is important to emphasize that the entire biliary apparatus of larvae including bile canaliculi disappears completely during normal metamorphosis in contrast to the pathological state of human biliary atresia.12, 13 However, it would be interesting and informative with regard to the embryonic form of human biliary atresia to understand the genetic programming underlying disappearance of biliary apparatus in the

sea lamprey. As might be expected, the degeneration of bile ducts occurs via programmed cell death see more or apoptosis in a related, nonparasitic lamprey, Lethenteron reissner, and in the sea lamprey, Petromyzon marinus.15, 16 Similar to the lamprey, several reports have documented cholangiocyte apoptosis as evidenced by positive transferase-mediated dUTP nick end labeling (TUNEL) staining of cholangiocytes in the livers

上海皓元 of patients with biliary atresia. Although apoptosis is a normal process in remodeling of the mammalian ductal plate during liver development, it would not be expected in the extrahepatic biliary system except as part of the process of immunologic ductal injury.16 In the lamprey the order of degeneration of bile ducts, i.e., intrahepatic versus extrahepatic, is variable between species. In the sea lamprey the degenerative process is asynchronous, and occurs more rapidly in small peripheral biliary components than in larger, medial ducts.12, 13 There is gradual disruption of tight junctions at the bile canaliculi and relocalization of membrane enzymes including alkaline phosphatase, adenosinetriphosphatase, and 5′-nucleotidase from apical to lateral membranes. In the human the most severe focus of injury is in the extrahepatic biliary system. The intrahepatic bile ducts respond initially with ductular proliferation and may be obstructed by bile plugs. Further and irreversible injury results from the noxious effects of biliary obstruction and probable ongoing immunologic damage that is variably relieved by the Kasai hepato-portoenterostomy operation.17 In adult lampreys, there seem to be no immediate consequences from the absence of a biliary system for the elimination of bile products.