Mechanisms of bile duct injury and liver fibrosis induced by MCP-1 and MIP-2 in liver tissues of biliary atresia mice

Abstract

Objective To establish a model of biliary atresia (BA) by infecting neonatal mice with rotavirus (RRV) and explore the mechanisms of intra-hepatic bile duct injury and liver fibrosis under a high expression of MCP-1 and MIP-2 in BA murine liver.Methods RRV was injected intraperitoneally to induce BA of neonatal mice as experimental group while 10％ fetal bovine serum-Dulbecco's modification of Eagle's medium (FBS-DMEM) was injected as control group.The neonatal mice were sacrificed at Days 4,7,14 and 21 and their extra-hepatic bile ducts and liver tissues were harvested.The histological changes of extra-hepatic bile ducts and liver tissues were analyzed by hematoxylin-eosin staining.The expressions of MCP-1 and MIP-2 in BA mice livers were detected by immunohistochemistry and fibrosis by Masson staining.And Image-Pro Plus software was used to measure the positive indices of MCP-1 and MIP-2 and the fibrosis level of liver tissues.Results The gain weights of BA mice were significantly slower than those of control group.And the BA mice had typical symptom of jaundice.HE staining showed plenty of cellular infiltrates in both bile ducts and liver tissues of BA group,partially narrowed bile ducts were observed at Day 7 and obliterated bile ducts at Day 14.The expressions of MCP-1 and MIP-2 were significantly higher than those of control group.The positive indices of MCP-1 and MIP-2 in BA mice livers were 5168.16 ± 627.30 and 783.38 ± 46.19 respectively at Day 21 days versus control group of 5168.16 ± 627.30 and 783.38 ± 46.19 (P＜0.001.There was a strong positive correlation with each other (r =0.918,P＜0.001).A large number of collagen deposition and even fibrosis were found in liver tissues of BA group.Collagen deposition in BA mice livers were (35.3 ± 5.45) ％ at Day 21 versus control group of (6.71 ± 0.83)％ (P＜0.001).And there was a positive correlation between collagen deposition and MCP-1 expression (r=0.529,P =0.005) and it was not observed in control group.Conclusions BA is an inflammatory disease probably mediated by a variety of inflammatory cytokines induced by virus infection.A high expression of MCP-1 and MIP-2 may play an important role in promoting inflammatory cell infiltration and collagen deposition leading to bile duct injury and liver fibrosis of BA mice. Key words: Biliary atresia; Monocyte chemoattractant protein; Macrophage inflammatory protein