Posttransplant Administration Of Allogeneic Bone Marrow Transfusion Combined With FK506,MMF And Anti-CD28mAb Induces Rat Hepatic Allograft Tolerance

Posttransplant administration of allogeneic bone marrow transfusion combined with FK506,MMF and anti-CD28mAb induces rat hepatic allograft toleranceBackgrounds Organ transplantation is a routine clinical procedure for patients with end-stage organ failure. However, despite standardization of surgical techniques and continuous refinements in anti-rejection therapies, long-term results of transplantation have not significantly improved during the last two decades. While successfully preventing acute rejection episodes, current immunosuppressive treatments are unable to control chronic rejection, which is the primary cause of long-term graft loss. Inddition, they cause a global immunodeficiency predisposing to severe infections and malignancies. Therefore, transplantation tolerance defined as survival of the allograft in the absence any immunosuppression remains a major goal to achieve for transplant physicians and immunologists. There is no shortage of experimental strategies for the induction of tolerance. Numerous regimens leading to the indefinite acceptance of vascularized grafts have been reported in rodent models. The relevance of these models for developing a clinical protocol, however, is severely limited, as most of these strategies fail to achieve similar results when attempted in large animals. In view of recent progress in the field, a number of experimental studies have confirmed that the establishment of mixed hematopoietic chimerism , defined as the coexistence of host and donor cells, may contribute to the induction of transplantation tolerance. The recent advances in this strategy is that allow the induction of mixed chimerism through novel, considerably less toxic protocols in rodents. In our experiments, we use a model of liver transplantation in the rat and develop a non-toxic, nonmyeloablative conditioning regimen consisted of FK506,MMF and antiCD-28mAb combined Posttransplant administration of allogeneic bone marrow to induce transplantation tolerance. Meanwhile the mechanisms of this strategy for inducing allotolerance, including the cytokine mRNA expression and the cell apoptosis in the allogfafts and peripheral blood. The research work presented in this thesis can be summarized as follows:Partâ… Objectives: To establish a rat model of stable orthtopic liver transplantation ( OLT ) using cuff technique, the establishment of a rat OLT is the precondition to perform such study. Methods: OLT in 200 SD rats which received Wistar liver were established by using "the two-cuff technique" with some modification in cuff tube, recipients anesthesia , abdominal aorta perfusion and the anastomosis of suprahepatic vena cava, portal vein, infrahepatic vena cava. Results : The time of vascular anastomosis for suprahepatic vena cava was 10 to 15 minutes, the anhepatic phase was 12 to 18 minutes, more than 75% of the grafted animals survived for seven days. Bleeding, thrombosis, infection and biliary obstructionwere the main complications that occurred in the recipients after surgery. Conclusions: The innovated technique can increase surgical rate of liver transplantation in the rat, including abdominal aorta perfusion being better than portal vein perfusion. To lessen the mechanical injury to the liver, to prevent the twisting of cuffs, to improve the quality of anastomosis, and to reduce anhepatic phase would be the keys to reduce the complications and increase the survival rate of rat liver transplantation. Part â…¡Objectives: To observe the liver allografts survival time and rejection episodes after administration of immunosuppressive agents consisted of FK506, MMF and anti-CD28mAb combined with or without administration of allogeneic bone marrow transfusion on the time of operation. Methods: Orthotopic rat liver transplantation was performed in a Wistar-to-SD strain combination. All of transplantation models were divided into six groups. A groups: Wistar-to-Wistar or SD-to-SD ( n=6 ); B groups: Wistar-to-SD without immunosuppression ( n=14 ); C groups: combination...