The Study Of The Immunomodulatory Effect Of CD200 Differentially Expressed Between Two Sources Of Human Placental Mesenchymal Stem Cells On Mouse Skin Graft

Objective To compare the immunosuppression effects of maternal and fetal placenta mesenchymal stem cells(m PMSC and f PMSC, respectively)on the rejection of allogenic skin transplants in mice, and further to investigate the mechanism underlying this suppression. Providing a basis theoretical for Clinical that mesenchymal stem cells as seed cells on suppress of allogeneic skin graft rejection.Methods m PMSC and f PMSC were isolated from human term placentas. The expression of cell surface markers was detected by flow cytometry. Cell proliferation capacity was characterized by MTT colorimetric assay. In some studies, the CD200 protein expressed on f PMSC were neutralized with streaming monoclonal antibodies, and m PMSC were infected with adenovirus expression vector carrying CD200 c DNA. For skin transplantation, C57BL/6 mice were randomly divided into 6 groups as skin transplant recipients, and ICR mice were served as skin donors. After establishment of the allogenic skin transplants, the 6 groups of recipient mice were iv injected respectively with PBS, m PMSC, f PMSC, f PMSC+Anti-CD200 antibodies, m PMSC+CD200 expressing vectors, and m PMSC+empty vectors. The conditions and survive time of the skin grafts were live inspected daily, and the expression of interleukin 17(IL-17), interferon γ(INF-γ), Tumor Necrosis Factor α(TNF-α) and interleukin 10(IL-10) in blood and spleen were measured at the end of the study by ELISA and RT-PCR.Results The majority of f PMSC were detected CD200 positive, while only a minor fraction of CD200 positive cells were detected in m PMSC. In the allogenic skin graft mice, the graft survival time in both m PMSC-and f PMSC-treated groups were significantly longer than that in PBS group, while the f PMSC group was more dominated than m PMSC group. Neutralizing anti-CD200 antibody reduced the graft survival of the f PMSC group to the level of that in m PMSC group, while enforced expression of CD200 increased the graft survival of the m PMSC group to the level of the f PMSC group. The empty vector transfected m PMSC showed similar effect on graft survival as that in m PMSC group, longer than PBS group but shorter than f PMSC and m PMSC+CD200 groups. RT-PCR results showed that, comparing with PBS group, the expressions of IL-17、IFN-γ and TNF-α were significantly reduced in m PMSC group, the expressions of TNF-α was significantly reduced in f PMSC group, the expressions of IL-10 was significantly increased in f PMSC group. Comparing with m PMSC group, the expressions of IFN-γ and TNF-α were significantly reduced in f PMSC group. Comparing with f PMSC group, the expressions of IFN-γ、IL-17 and TNF-α were significantly increased in f PMSC+Anti-CD200 group. Comparing with m PMSC+CD200 expressing vectors group, the expressions of IFN-γ、IL-17 and TNF-α were significantly increased in m PMSC+empty vectors group, the expressions of IL-10 was significantly reduced in m PMSC+empty vectors group. ELISA results showed the same as RT-PCR.Conclusion The immunosuppression effect of f PMSC on the rejection of allogenic skin transplantation was higher than that of m PMSC, and this difference was partially contributed by CD200 signaling pathway. The mechanism of this suppression may mediate the inhibition of IL-17, INF-γ, TNF-α and IL-10 expression. f PMSC may be a suitable choice for immunosuppression on skin transplantation.