Stro-1-positive human mesenchymal stem cells prolong skin graft survival in mice

Human mesenchymal stem cells (MSCs) and its stromal cell antigen 1 Stro-1 positive (Stro-1(+)) subgroup possess immunosuppressive properties. Our objective was to evaluate the in vivo inhibitory effect of MSCs and the Stro-1 subset.

Isolated human MSCs from bone marrow-derived mononuclear cells of healthy adults, and Stro-1(+) cells were cultured before sorting. Female C57BL/6 mice and female BALB/c mice were used as donors and recipients in an allogeneic skin graft model, respectively. The recipients were divided randomly into 4 groups: (1) The Stro-1(+) MSCs group received 2 × 10(6) Stro-1(+) MSCs injected into irradiated recipients before skin grafting. (2) The MSC group (2 × 10(6)) injected into the irradiated recipient mice before skin grafting. (3) The irradiated control group just irradiated before skin grafting. (4) The syngenic control group included irradiated BALB/c mice that received skin from syngenic mice. The main data included skin graft survival times, histologic changes on hematoxylin and eosin (HE) staining and plasma transforming growth factor (TGF)-β concentrations in recipients measured by enzyme-linked immunosorbent assay (ELISA) before and after transplantation.

The skin graft survival time in the MSCs group (12.13 ± 3.34 days) was not significantly prolonged versus the irradiated controls (11.38 ± 1.01 days), but it was notably prolonged among the Stro-1(+) MSCs group (30.68 ± 5.89 days) compared with the irradiated control and the MSCs groups, respectively. The histology of skin grafts among the stro-1(+) group showed a clear structure. After grafting, plasma TGF-β concentrations were almost the same as before transplantation among the irradiated and the syngenic controls but significantly increased in the MSCs and Stro-1(+) MSCs groups.

Stro-1(+) MSCs induced greater prolongation of skin grafts in mice than unsorted MSCs; however, TGF-β expression did not contribute to this effect.