title: Effects of selective bile duct ligation on liver parenchyma in young animals: histologic and molecular evaluations.
abstract: OBJECTIVE
  The mechanisms of increased collagen production and liver parenchyma fibrosis are poorly understood. These phenomena are observed mainly in children with biliary obstruction (BO), and in a great number of patients, the evolution to biliary cirrhosis and hepatic failure leads to the need for liver transplantation before adolescence. However, pediatric liver transplantation presents with biliary complications in 20% to 30% of cases in the postoperative period. Intra- or extrahepatic stenosis of bile ducts is frequent and may lead to secondary biliary cirrhosis and the need for retransplantation. It is unknown whether biliary stenosis involving isolated segments or lobes may affect the adjacent nonobstructed lobes by paracrine or endocrine means, leading to fibrosis in this parenchyma. Therefore, the present study aimed to create an experimental model of selective biliary duct ligation in young animals with a subsequent evaluation of the histologic and molecular alterations in liver parenchyma of the obstructed and nonobstructed lobes.
  
  
  METHODS
  After a pilot study to standardize the surgical procedures, weaning rats underwent ligation of the bile ducts of the median, left lateral, and caudate liver lobes. The bile duct of the right lateral lobe was kept intact. To avoid intrahepatic biliary duct collaterals neoformation, the parenchymal connection between the right lateral and median lobes was clamped. The animals were divided into groups according to the time of death: 1, 2, 3, 4, and 8 weeks after surgical procedure. After death, the median and left lateral lobes (with BO) and the right lateral lobe (without BO [NBO]) were harvested separately. A group of 8 healthy nonoperated on animals served as controls. Liver tissues were subjected to histologic evaluation and quantification of the ductular proliferation and of the portal fibrosis. The expressions of smooth muscle α-actin (α-SMA), desmin, and transforming growth factor β1 genes were studied by molecular analyses (semiquantitative reverse transcriptase-polymerase chain reaction and real-time polymerase chain reaction, a quantitative method).
  
  
  RESULTS
  Histologic analyses revealed the occurrence of ductular proliferation and collagen formation in the portal spaces of both BO and NBO lobes. These phenomena were observed later in NBO than BO. Bile duct density significantly increased 1 week after duct ligation; it decreased after 2 and 3 weeks and then increased again after 4 and 8 weeks in both BO and NBO lobes. The portal space collagen area increased after 2 weeks in both BO and NBO lobes. After 3 weeks, collagen deposition in BO was even higher, and in NBO, the collagen area started decreasing after 2 weeks. Molecular analyses revealed increased expression of the α-SMA gene in both BO and NBO lobes. The semiquantitative and quantitative methods showed concordant results.
  
  
  CONCLUSIONS
  The ligation of a duct responsible for biliary drainage of the liver lobe promoted alterations in the parenchyma and in the adjacent nonobstructed parenchyma by paracrine and/or endocrine means. This was supported by histologic findings and increased expression of α-SMA, a protein related to hepatic fibrogenesis.
authors.affiliation: Pediatric Surgery Division, Pediatric Liver Transplantation Unit and Laboratory of Research in Pediatric Surgery (LIM 30), University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Ana Cristina A
authors.initials: AC
authors.lastname: Tannuri
authors.forename: Maria Cecília M
authors.initials: MC
authors.lastname: Coelho
authors.forename: Josiane
authors.initials: J
authors.lastname: de Oliveira Gonçalves
authors.forename: Maria Mercês
authors.initials: MM
authors.lastname: Santos
authors.forename: Luiz Fernando
authors.initials: LF
authors.lastname: Ferraz da Silva
authors.forename: Israel
authors.initials: I
authors.lastname: Bendit
authors.forename: Uenis
authors.initials: U
authors.lastname: Tannuri
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001653:Bile Ducts, Intrahepatic / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D015415:Biomarkers / Q000378:metabolism; D002780:Cholestasis, Intrahepatic / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D003094:Collagen / Q000378:metabolism; D004195:Disease Models, Animal; D008026:Ligation; D008099:Liver / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D008105:Liver Cirrhosis, Biliary / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: D000199:Actins; D015415:Biomarkers; D003094:Collagen; D053773:Transforming Growth Factor beta1; C498862:Acta2 protein, rat