Experimental Study On Chronic Immunosuppression After Lung Transplantation Produced By Inducing Of The Mixed Chimerism Using BMC/BM-MSCs

Background:Lung transplantation is the most important method in healing the serious pulmonary disease. The advances in immunosuppressive drug have yielded improvement of transplantation; yet long-term survival recipient complications and graft loss continue to accompany chronic immunosuppression. Induction of tolerance may hold the key to improve transplant longevity and quality of life in recipient and increase the cost-effectiveness of transplant therapy at the same time. With further studies and developments of transplantation immunology, eliminating transplant rejection through inducing immune tolerance has become the main goal in organ transplantation. Obliterative bronchiolitis(OB) is the most important cause of graft dysfunction following lung transplantation.The purpose of this study was to induce chimera by donor bone marrrow and mesenchymal stem cells transplantation and observe its effects on obliterative bronchiolitis(OB) after lung transplantation, and investigate the pathogenesis of transplantation tolerance of chimera preliminarily in an animal model.Methods:1,SD and Wistar rat were, respectively, selected as donor and recipient In experimental group, while in control group, SD rat served as donors and recipients, respectively.All grafts were harvested 28 days after transplantation and stained with hematoxylin and eosin (HE) to observe the histopathology of the grafts. OB incidence in two groups was compared.2,SD and Wistar rat were, respectively, selected as donor and recipient.Donor and recipient were divided randomly into 8 groups. Recipient was conditioned with sublethal whole body irradiation (WBI) in Group A, B and C. Group A infused with saline solution; Group B infused with bone marrow cells (BMC) of SD rat; Group C infused with bone marrow mesenchymal stem cells (BM-MSCs) of SD rat. Animals in other groups did not receive whole body irradiation, they received FK506 3 mg two days before transplantation. Then Group D infused with saline solution. Group E infused with bone marrow cells (BMC) of SD rat. Group F infused with bone marrow mesenchymal stem cells (BM-MSCs) of SD rat. Group G infused with bone marrow mesenchymal stem cells (BM-MSCs) and bone marrow cells (BMC) of SD rat. The tracheal segments of Wistar rat were then heterotopically transplanted into recipient rats in all groups. Grafts were harvested at day 3, 14 ,28 after transplantation. To explore immune depression mechanisms, the mixed lymphocyte reaction (MLR) was performed. The level of IL-2,IL-10 and the obliteration ratio were also measured. Recipient rats were detected for donor origin cells in the peripheral blood lymphocyte and spleen by polymerase chain reaction (PCR). All grafts were harvested 28 days after transplantation and stained with hematoxylin and eosin (HE) to observe the histopathology of the grafts.Results:1,The experimental group showed the histopathology of OB. The incidence of OB in the experimental group was significantly lower than in the control group.2,The results showed that donor lymphoid chimeras can be found in the immune depression Wistar rat (Group C > Group B). Wistar rat were specifically tolerant to the SD rat in MLR assay in Group B and Group C. The obliteration ratio of allograft in group A was higher than that in group B and C( P<0.05).3. Chimera can be found in the peripheral blood and spleen lymphocyte in the tolerance Wistar rats of Group B, C, E, F, and G.4. Allografts in Groups infused with bone marrow mesenchymal stem cells (BM-MSCs) / bone marrow cells (BMC) of SD rat expressed significantly less IL-2 expression than that in Group A. 5.At the same time, lymphocytic infiltration and luminal obliteration were lower in Groups infused with bone marrow mesenchymal stem cells (BM-MSCs) / bone marrow cells (BMC) of SD rat than that in Group A and D (p<0.01).Conclusions:1,Heterotopic tracheal allografting in rat as a model of chronic allograft rejection after lung transplantation displays many advantages. 2,These results suggest that non-myeloablative conditioning regimens for allogeneic BMC/BM-MSCs transplantation can successfully establish mixed chimeras model from SD to Wistar rat and induce a specific immune depression in Wistar rat .