Study On Immunological Rejection In Transplantation Of Cryopreserved Aortic And Pulmonary Valved Homograft

ObjectiveTo investigate the influence of aortic and pulmonary homografts on host and the effect of immunological rejection on the homografts.Rat model of cryopreserved aortic and pulmonary valved homograft heterotopic transplantation was established to investigate the effect of cryopreservationg on the antigenticity of the aortic and pulmonary homografts,,observe the changes of humoral and cellular immunological responses and pathological changes of implanted homografts.to study the effect of immunosuppressive treatment on the aortic and pulmonary homograft transplantation.MethodsIn this study,Liquid nitrogen cryopreservation method was adopted in the long-term storage of the aortic and pulmonary homografts.Transmitting electron microscope was used to observe the effect of cryopreservation on endothelial structure and tissular structure.The animal models of aortic and pulmonary homograft transplantation were established by heterotopic insertion of aortic and pulmonary homografts of SD rats into abdominal aortae of Wistar rats.CsAwas employed in the treatment of immunological rejection in the immuusuppressive treatment group of aortic homograft transplantation.Respectively at 1th,2th,3th 4th,and 5thweeks after implantation,the blood samples of the transplanted animals were collected and the homografts retrieved.The area of intima and media of the implanted grafts was measured and a relative area ratio of intima to media (I/M area ratio) was calculated to estimate the degree of the intimal thickening. In addition,the munbers of nucleated cells in the media and adventitia were counted,and estimated as cell number per 0.1 mm~2.Immunohistochemical staining was performed to detect the MHCⅡdeposition of the aortic and pulmonary homografts and the percentage of CD4 +,CD8 + lymphocytes and the ratio of CD4 +/CD8 + in blood samples of the implanted rats.The biological activities of IL-2 and TNF-a in blood samples of the implanted rats were measured by means of ELISA.ResultsCryopreservation may maintain viabilities and normal intercellular connections of endothelial cells of the aortic and pulmonary homografts.The pathological changes of the explanted homografts presented damages of the endothelialcells, infiltration of inflammatory cells in media and advenfitia,intimal thickening of the homografts,etc.Intimal thickening progressively increased,the numbers of inflammatory cells infiltrated in the homografts maintain high leveh during the 5weeks after implantation.The MHCⅡdeposition were found respectively about 1 to 4 weeks after the implantation of aortic and pulmonary homografts. Thepercentage of CD4 + and CD8 + T lymphocytes,the ratio of CD4 + to CD8 +(CD4 +/CD8 +),and the biological activities of IL-2 and TNF-a in the blood samples of transphnted rats were remarkably increased after homografts implantation,and maintain high -activity levels during the 5 weeks after implantation. There was significant difference in the results between implantation group and control group(p＜0.05).the treatment of CsA had remarkably suppressive effect on deposition of MHCⅡ,infiltration of inflammatory cells,increase of intimal thickening,increase of the percentage of CD4 +,and the increase of biological activities of IL-2 and TNF-a in blood samples after homografts implantation. There was no obvious difference of infiltration of inflammatory cells,the increase of intimal thickening,and the increase of the percentage of CD4 + T lymphocytes, and the increase of biological activities of IL-2 and TNF-a in-blood samples between the aortic and pulmonary homografts imphatation groups. Conclusion1.Liquid nitrogen cryopreservation method may maintain the viability and normal structure of aortic and pulmonary homografts.2.There was obvious immunological rejection after implantation of aortic and pulmonary homografts,cellular and humoral immunological responses were involved in the process if immunological rejection.Cellular immune played a major role in chronic immunological rejection.3.the pathological changes of cryopreserved aortic and pulmonary homografts were progressive intimal-thickening,necrosis of smooth muscle cells in the media,and infiltrationg of inflammatory cells in the adventitia,which resulted in calcification and obstruction of aortic and pulmonary homografts.4.There was no difference in immunological rejection between aortic and pulmonary homografts after implantation.Immunological rejection is an important reason for the calcification of aortic and pulmonary homografts after implantation, while the degree of calcification has close relationship with calcium content in the homografts.5.The treatment of CsA has marked suppressive effect on immunological rejection and calcification.