The Establishment And Study Of An Experimental Model For Allograft Vasculopathy In Rat Aortic Allografts

PART 1:Establishment of an experimental model for allograft vasculopathy in rat aortic allograftsObjective:To establish an animal model to study the mechanism of allograft vasculopathy and methods of preventing allograft vasculopathy.Methods:48 rats were randomly assigned to allograft experimental group (Wistar→SD,n=24) and isograft control group(Wistar→Wistar,n=24).The establishment of model was used with thoracic aorta to abdominal aorta transplantation in rats.Animals were sacrificed at 5,14 and 28 days after transplantation.The aortic allografts were studied by light microscopy and transmission electronic microscopy.Regional changes in the lumen,intimal and medial layers were measured with computer imaging analysis system.Results:In this study,neointimal hyperplasia was observed in the allograft experimental group characterized by extensive intimal thickening at 28 days after transplantation.The lesion included intimal hyperplasia,which is mainly depended on the proliferation of smooth muscle cells and the accumulation of extracellular matrix,and inflammatory cells infiltration in neointimal and adventitia.There were no obvious changes in the aortic graft of the isograff control group.Conclusions:It was feasible to use thoracic aorta to abdominal aorta transplantation as a simple allograft vasculopathy model.The changes of transplanted aorta were analogous to graft vasculopathy in human.The animal model was suitable for the advanced research in the mechanism and prevention of allograft vasculopathy. PART 2:Role of vascular smooth muscle cells in allograft arteriosclerosis in rat aortic allograftsObjective:To investigate the effect of paclitaxel on the intimal proliferation in rat aortic allografts and the possible mechanism on preventing graft vasculopathy.Methods:32 rats were randomly divided into two groups:isograft control group (Wistar→Wistar) and allograft experimental group(Wistar→SD).The animals were operated on with a thoracic-to-abdominal aortic transplantation.Animals were sacrificed and the grafts were harvested at 28 days after operation.The aortic grafts were then processed for staining and measurements.Hyperplasia,smooth muscle cell proliferation were detected by pathological and immunohistochemical methods. The presence of apoptosis smooth muscle cells was demonstrated by terminal deoxynucleotidyl transferase biotin nick end-labeling(TUNEL) method.Results:The results show that there was proliferation and apoptosis of vascular smooth muscle cells in aortic grafts of both groups at 28 days after operation.In allografts proliferation and apoptosis happened in neointima while in isografts it happened generally in media.Allografts had significantly higher level in the average intimal thickness and the degree of inflammatory cells infiltration in adventitia compared with isografts.Immunohistochemical analysis of proliferating cell nuclear antigen(PCNA) and results of the TUNEL test indicated that both proliferation and apoptosis was more severe in allografts than in isigrafts.Conclusion:The results suggest that vascular smooth muscle cells play an important role in the pathological progress of allograft vasculopathy.Compared with apootosis, the degree of pathological proliferation in allografts is higher.It is the over-proliferation of vascular smooth muscle cells that induced intimal hyperplasia and neointima formation.