Establishment of a Standardized Rodent Model for Composite Tissue Allotransplantation (CTA): Improvement of Surgical Techniques, Anaesthesia and Monitoring of the Graft

To establish a valid and reproducible model of allogeneic vascularized limb transplantation different techniques of anaesthesia, transplant surgery, vascular anastomoses, ischemia time and the influence of common immunosuppressive therapy in an optimized rat model were analysed. Transplantation of the forelimb employed Cuff Anastomosis Technique with a mean Warm Ischemic Time (WIT) of 30 minutes in IM anaesthesia with spontaneous breathing appeared to be the best model. To analyze the influence of immunosuppression, animals were evaluated in five groups: two isogeneic (with / without immunosuppression) and three allogeneic (no immunosuppression, Cyclosporin A and Tacrolimus monotherapy). Experiments were stopped when graft Functional Capillary Density (FCD) declined by 30% as a sign of microthrombosis of small vessels or at day 24. FCD was controlled by Cytoscan technique at regular intervals. Allograft and Isograft transplant recipients were clinically evaluated daily for signs of rejection. Additionally, levels of Immunosuppressives and Interleukin 6 (IL-6) were analyzed and Cyto-Immunological Monitoring (CIM) was performed. Specimens were taken for histopathologic evaluation at completion. All Allograft and Isograft transplant recipients without immunosuppression had to be terminated before day 24. Animals of the Isogeneic group with Immunosuppression did not have a significant reduction of FCD at day 24. This illustrates that in all groups with the exception of the Isografts with immunosuppression a graft rejection appeared. However, graft survival time was significantly different between the groups. Differences between immunosuppressive regimes were not found. Levels of immunosuppressants remained within the defined range. No correlation between rejection, CIM and IL-6- level was found. From this data we may conclude that CIM and IL-6 levels are not effective in monitoring early rejection in composite tissue allografts in rats.