Leflunomide Prolongs The Survival Time Of Xenograft In A Rat-to-mouse Heterotopic Heart Transplantation Model

Backgrounds:Xenotransplantation is an effective way to circumvent donor shortage in clinical transplantation.However,there come AVR and CMR to be the greatest barrier for clinical use of xenotransplantation.Moreover,the immunosuppressant regime used clinically is inadequate to help surpass the immunological barrier.Our aim is to establish a rat-to-mouse heterotopic heart transplantation model using the cuff technique.Then based on the model,we try to figure out whether leflunomide can inhibit the process of AVR or CMR.Methods:The heterotopic heart xenotransplantation model was successfully established using both BALB/c and C57BL/6 mice as recipient.Then the LEF-treated group was treated with LEF 30mg/kg/day ip.For a fixed day after transplantation,the donor hearts of the mouse in each group were HE stained,serum and T cell subsets,Bcells and Tfh cells were analysed by FCS.Results:1.The MST of xenografts in Lewis—BALB/c group is 4.310.8 days(n=6),and in LEF-treated group,the survival time can be maximumly prolonged to 15 days.The MST of xTx in Lewis—C57BL/6 group is 11.7±2.4 days(n=6),and the survival time can be maximumly prolonged to 25 days.2.The HE staining of xenografts in BALB/c recipients showed a typical AVR.whereas that of xenografts in C57BL/6 recipients showed a mixed AVR and CMR.3.By FCS analysis.we find that,the IgGl,IgG2a level in the serum of BALB/c recipients in positive control group harvested 4 days post-transplantation are obviously higher than that in naive group and LEF-treated group.However,the IgGl,IgG2a level in the serum of C57BL/6 recipients are of no significant difference among all three groups.4.For FCS analysis,we find that,the percentage of CD4+CD185+T cells of BALB/c recipients in positive control group are obviously higher than that in naive group.However,the percentage of CD4+CD185+T cells of C57BL/6 recipients are of no significant difference between nalive group and positive group.Conclusions:1.A rat-to-mouse heterotopic heart transplantation model can be successfully established using the cuff technique.The HE staining of xenografts in BALB/c recipients showed a typical AVR,whereas that of xenografts in C57BL/6 recipients showed a mixed AVR and CMR.2.Leflunomide can significantly prolong the MST of xenografts in both strains of recipients.The possible mechanism can be the down-regulation of donor-specific IgGl,IgG2a by inhibiting the T,3 response in BALB/c recipients.