Mesenchymal Stem Cells Prolong Composite Tissue Allotransplant Survival in a Swine Model

Background. This Study investigated whether mesenchymal stem cells (MSCs) combined with bone marrow transplantation (BMT), irradiation, or short-term immunosuppressant therapy could prolong composite tissue allotransplant survival in a swine hind-limb model. Methods. Heterotopic hind-limb transplantation was performed in outbred miniature swine. Group I (n=5) was the untreated control. Group 11 (n=3) received MSCs alone (given on days -1, +3, +7, + 14, +21). Group III (n=6) received cyclosporine A (CsA days 0 to +28). Group IV (n=4) received preconditioning irradiation (day - 1), BMT (day + 1), and CsA (days 0 to +28). Group V (n=5) received irradiation (day - 1), BMT (day + 1), CsA (days 0 to +28), and MSCs (days + 1, +7,+ 14). The expression and localization of CD4(+)/CD25(+) T cells and MSCs were assessed using flow cytometry and immunohistochemistry. Results. The allografts survival with MSCs alone revealed a significant prolongation, when compared with the controls (P=0.02). Allografts with CsA treatment exhibited delayed rejection. Irradiation and BMT-CsA treatment revealed no significant allograft survival benefit when compared with the CsA treatment group, but graft-versus-host disease (GVHD) was evident. However, combination of MSCs-BMT-CsA treatment demonstrated significant prolongation of allograft survival (>200 days, P<0.001) and no signs of GVHD with the lowest degree of rejection in the allo-skin and interstitial muscle layers. The CD4(+)/CD25(+) regulatory-like T-cell expression in the circulating blood and allo-skin significantly increased in the MSC-BMT-CsA group. Examination of bromodeoxyuridine-labeled MSCs revealed donor MSC engraftment into the recipient and donor skin and the recipient liver parenchymal tissue. Conclusion. These results suggested that the regulatory activity of MSCs on T cells and GVHD might contribute to significant prolongation of composite tissue allotransplant survival in the MSC-BMT-CsA treatment.