[Immune tolerance induced by human Stro-1 positive mesenchymal stem cells in mouse skin graft]

This study was aimed to evaluate whether human mesenchymal stem cell (MSC) and the Stro-1 positive subgroup have inducing immune tolerance effect in mouse skin graft model. Human MSC were isolated and cultured from bone marrow-derived mononuclear cells of healthy adults, and Stro-1 positive cells were sorted out. Female C57BL/6 mice and female BALB/c mice were respectively used as donors and recipients in skin allogenic graft model. The recipients were divided randomly into 4 groups: (1) Stro-1(+) MSC group: 2×10(6) Stro-1(+) MSC were injected into the irradiated recipient mice before skin graft. (2) MSC group: 2×10(6) MSC were injected into the irradiated recipient mice before skin graft. (3) Irradiation control group: the recipient mice were just irradiated before skin allogenic graft. (4) Congenic control group: the irradiated BALB/c mice received the skin from the congenic mice. The survival time and pathologic changes of skin grafts were observed by macro- and microscopy with HE staining. The transforming growth factor β1 (TGF-β1) concentration in plasma of recipient mice was measured by ELISA before and after grafting. The results indicated that the survival time of skin grafts in the MSC group was (12.13 ± 3.34) d, which was not notably longer than the irradiation control group (11.38 ± 1.01) d. The survival time of skin grafts was significantly prolonged in the Stro-1(+) MSC group (30.68 ± 5.89) d, as compared with the irradiation control group and the MSC group, respectively; the pathologic examination of skin grafts showed a clear structure. After grafting, the TGF-β1 concentration in plasma of recipient mice was almost the same as before grafting in the irradiation control group and the congenic control group, but it significantly increased in the MSC group and the Stro-1(+) MSC group. It is concluded that the Stro-1(+) MSC induce greater immune tolerance than the unsorted MSC, and significantly prolong the survival time of skin grafts in vivo, while TGF-β1 does not contribute to the immune tolerance.