Immunosuppressive Effect Of Mesenchymal Stem Cell In Rat Cardiac Transplantation

In recent years heart transplantation still remains the only effectivetherapeutic modalityintreatmentofend-stageheartdiseases. Buthowto avoid the side effects of lifelong immunosuppressive medicationscontinues to be a difficult problem in organ transplantation.Theoreticallyoneofthe effectiveways toresolverejectionreactionsisthe active induction of tolerance with immunocompetence preserved.Mesenchymal stem cell(MSC) is one of the most promisingnonhematopoietic pluripotent cells present in adult bone marrow thatcan differentiate under appropriate stimuli along three principallineages: osteoblastic, adipocytic and chondrocytic lineages.Furthermore,invitroMSCshavebeenshownto suppressactivationofT cells; in vivo MSCs can prolong the survival of transplanted skinand treat graft-versus-host disease. But little is known about MSCs inheart transplantation. In our study we investigated the immunomodulatory function and possible mechanisms through ratcardiactransplantation model.Purpose Heterotopic rat heart transplantation model is made andisolationandcultureofMSCsarestandardized.Toinvestigatewhetherintravenous infusion with MSCs would prolong the survival oftransplanted heart and the possible underlying mechanisms andfurthermoredevelopanewapproachtotoleranceinduction.Methods MSCs were isolated and ex vivo cultured according todensity gradient centrifugation method. In vitro suppression of T cellactivation is shown by mixed lymphocyte reaction. Intra-abdominalcardiac transplantation was performed between donor Wistar rats andrecipient F344 rats; MSCs derived from Wistar rats were infused intorecipients via the tail vein at designated intervals(one week before, onoperativeday,andconsecutivethreedayspostoperative).Transplantedhearts were screened with real-time PCR to analyze Th1 and Th2cytokine gene expression change. Cell-mediated lympholysis wasconducted to investigate MSC's effect on T cell cytotoxicity aftertransplantation.Results Immunocytochemical findings revealed that MSCs werenegative for hematopoietic markers CD34, CD45 but typicallyexpressed the antigens CD29, CD106, and CD117. In vitro mixedlymphocyte reaction indicated that allogeneic T cell response wasgreatly suppressed by MSC in a dose-dependent manner. Comparedwith control group, survival of MSC-treated allografts was markedly prolonged(mean survival days: 12.4±5.3 vs 6.4±2.0, P=0.009).According to real-time PCR heart allografts of MSC-treated groupshowed a highly significant(P<0.05) reduction in the expression ofgenes encoding the pro-inflammatory Th1-type cytokines IL-1βandIFN-γ, while the anti-inflammatoryTh2-typecytokinesIL-4andIL-10were greatly expressed in MSC-treated group but not in controlgroup(P<0.001). Cell-mediated lympholysis results indicated that TcellcytotoxicitywasalsosignificantlyinhibitedinMSC-treatedgroupcomparedwithcontrolgroup.Conclusions1.Density gradient centrifugation method with percollsolution is an easy and effective method for MSCs isolation andculture. 2. Allogeneic T cell response can be suppressed in accordingto mixed lymphocyte reaction and cell-mediated lympholysis. 3.Accordingtoratcardiactransplantationmodel andbywayofRT-PCRintravenous administration of MSCs can prolong the survival oftransplanted heart possibly by induction of allograft tolerance throughchangingTh1/Th2balance.