A Study On The Immune Responses And The Healing Of Osteochondral Xenograft

Objective To investigage the immune responses and the healing of osteochondralxenograft.Methods36New Zealand rabbits were used as transplant recipients and transplant donorsfor autografts and allografts.1pig was used as transplant donor for xenografts. Rabbits wererandomly divided into three groups: Group A for autografts; Group B for allografts and Group Cfor xenografts. Osteochondral defection models were made on the femoral trochleae of eachrabbits. At the2,4and12weeks after surgery, peripheral blood samples were collected to detectIL-2, IL-4and IFN-γ.At the4and12weeks after surgery,6rabbits in each groups were killed toobtain distal femur samples, synovial tissue samples and synovial fluid samples for grossobservation, pathological testing and detecting IL-2, IL-4and IFN-γ.Results Moran gross scoring shows that the scores of Group C is lower than Group A andGroup B at the4weeks after surgery; at the12weeks after surgery, the scores of Group C islower than Group A, but no significant difference with Group B. Results of cytokine in the bloodserum and the synovial fluid demonstrated that at2weeks after surgery, the IFN-γ level in theblood serum of Group C is lower than Group A and Group B; the IL-4level in the blood serumof Group C is higher than Group A and Group B. After4weeks of the surgery, the IFN-γ level inthe blood serum of Group C is higher than Group A; the IL-2level in the synovial fluid of GroupC is higher than Group A and Group B; the IL-4level of Group C is higher than Group B in theblood serum, in the synovial fluid, the IL-4level of Group C is higher than Group A, but lowerthan Group B. After12weeks of the surgery, the IFN-γ level in the blood serum of Group C ishigher than Group A and Group B, and higher than Group A in the synovial fluid; the IL-2levelin the blood serum is higher than Group A and Group B, as well as in the synovial fluid; the IL-4level in the synovial fluid of Group C is higher than Group A. The result of the pathologicaltesting shows that the synovial tissues of Group B were infiltrated by inflammatory cells, andwere anastatic at the12weeks after surgery. Massive inflammatory cells were found in thesynovial tissues of Group C, which were reduced at the12weeks after surgery, but still morethan Group B. Mild inflammatory cells infiltration were found in some synovial samples ofGroup A.Conclusion The mechanism of the immune responses and the healing of osteochondralxenograft is different from allografts. The immune responses of xenografts are stronger thanallografts,especially in the early stage. The rejection of xenografts is mainly associated with Th2-type cell response, whereas the allografts with a Th1-type. The occurrence of the resorptionof xenografts are later than allografts.