| ObjectiveEstablished the rat liver transplantation model of chronic rejection. To study the role of VEGF in chronic liver allograft rejection,and liver pathology,and to explore its clinical significance.Methods1 Established the rat liver transplantation model of chronic rejection: orthotopic liver transplantations were performed from BN to Lewis rats with modified Kamada double-cuff method.Animals were randomly allocated to three group:Group A: Lewis→BN,n=20,animals received lml/kg/d normal saline from transplantation to day 30 by subcutaneous injection. Group B: Lewis→BN,n=32,animals received lml/kg/d CsA from transplantation to day 30 by subcutaneous injection. Group C: Lewis→Lewis (control group),n=32,animals received CsA similar to B group. Four animals from each group were randomly sacrificed on days 1,6, 10,21,30 and 60 after transplantation. The pathological changes of the liver graft were observed with Hematoxylin-Eosin(H-E),Van Gieson (VG)staining,Reticular fiber staining,cytokeratin 19(CK19) immunohistochemistry.2 Immunohistochemistry were used to measure the expression of VEGF in acute liver allograft,the chronic liver allograft and isogenic liver.Results1 Moderate acute rejection was discovered in group A with RAI score 6 to 7 after day 6.The pathological grading of damage in the liver graft gradually aggravated,and the grade of acute rejection rated as"severe"with RAI score 8 to 9 at day 10 or dying condition.2 The pathological grading of chronic rejection in the liver graft gradually increased in group B.The fibrosis of allograft increasely aggravated. The number of bile duct graduatelly decreased. Typical chronic rejection was discovered in group B with RAI score 9 to 12 after day 60,which shows bile duct inflammation injury,narrow of original lumen or occlusion of hepatic artery,portal tracts were obviously enlarged,Central veins were focal occlusion with inflammation ,some showed severe fibrosis.3 There was not immunological rejection in C group with RAI score 0 to 3,and similar to normal hepatic tissue day 6.4 Expression of VEGF in hepatocytes were obviously discovered in A group,B group and C group at day 1.The trend of VEGF expression is different among the three groups. The level of its expression gradually increased along with time extension in A group.The level in B group was up to a peak at day 6,then decreased gradually ,but began to increase and kept higher level at day 10. The level in C group began to decline and kept low,and there were almost not VEGF expression at day 60.5 At day 1, the differences of VEGF expression in liver graft among 3 groups were not statistically significant ( P >0.05 ). At day 6 , there were not statistically significant between B group and A group,also between B group and C group ( P >0.05 ).At day 10,there were statistical significances among the three groups( P<0.05 ), the level of hepatic graft in A group was the most highest, which followed by B group, for C group had the most slight expression.At day 60,the VEGF expression in B rejection group are higher than C group.Conclusion1 The appearances of liver graft pathology, in the rat strain combination of Lewis→BN with low-dose immunosuppression,were consistent with characteristics of chronic rejection after liver transplantation , so liver transplantation model with Lewis→BN rats combination is the ideal animal model to study chronic rejection after liver transplantation.2 Our results demonstrated that VEGF expression was increased in both acute and chronic rejection of rat liver transplantation. Our data suggested that VEGF may have an important role in the pathology of chronic rejection.
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