Abstract

Sequential development pattern of the intrahepatic bile ducts is analyzed histologically and immunohistochemically using 50 embryonal and fetal liver specimens. Serial sections are made to reconstruct the intrahepatic biliary system, and monoclonal antibodies were used for differential antigenic expression of the biliary system. By 9 weeks of gestation a layer of small round cells, namely plate cells, became first noticed around large portal vein branches close to the hepatic hilum. These plate cells extended subsequently to more distal branches. The ductal plates became duplicated to contain cleft-like spaces and tubular structures. These tubules gradually became incorporated into surrounding connective tissue around the protal vein, and gave the appearance of the individualized bile duct. At term(40 weeks of gestation) the smallest branches of the portal vein were still surrounded by a discontinuous ductal plate. The ductal plate cells showed strong positive reaction for CAM 5.2 and AE1/AE3. They also expressed CK 19 and AE1 from 9 weeks of gestation on. The immunoreactivity of bile duct cells for cytokeratins persisted throughout the whole gestational period. Carcinoembryonic antigen was expressed along the luminal border of the bile duct, duplicated ductal plate and intrahepatic bile canaliculi. Laminin was demonstrated along the basement membrane of the bile duct cells from 9 weeks of gestation. Few duplicated ductal plates were composed of two different types of cells, duct-like cells and hepatocyte-like cells. The duct-like cells and hepatocyte-like cells showed same imrhunoreactivity with the hepatocytes and the bile duct cells, respectively, suggesting that the intrahepatic bile duct cells are actually coming from the hepatocytes around the branches of the portal vein.

• Keywords: Intrahepatic bile duct;Development;Human;Immunohistochemistry;Liver