Immunosuppressive effects of rat mesenchymal stem cells: involvement of CD4+CD25+ regulatory T cells.

Background: Recent studies show that mesenchymal stem cells (MSCs) have immunomodulatory properties. They suppress the immune response to alloantigen and modify the proliferation of T cells. CD4+CD25+ regulatory T cells have strong immunomodulatory potential. However, little is known about the effects of rat MSCs (rMSCs) on the development of regulatory T cells.
Methods: MSCs were obtained from bone marrow of male Sprague-Dawley rats, and co-cultured with CD3+ T cells from allogeneic spleen cells. The proportion of CD4+CD25+ regulatory T cells was analyzed by flow cytometry. To further confirm the immunosuppressive activity of rMSCs, we used MTT assay and flow cytometry of CD3+ T cells to investigate the proliferative responses of CD3+ T cells to mitogenic stimuli. Enzyme-linked immunosorbent assay was performed to detect alterations of the cytokines TNF-alpha, TGF-beta and IL-10.
Results: The proliferation of CD3+ T cells decreased when co-cultured with rMSCs, and the degree of inhibition was concentration-dependent. The percentage of CD4+CD25+ regulatory T cells increased when CD3+ T cells were co-cultured with different concentrations of rMSCs. The levels of pro-inflammatory cytokine (TNF-alpha) decreased while anti-inflammatory (TGF-beta, IL-10) cytokines increased in mixed lymphocyte reaction.
Conclusions: rMSCs inhibit allogeneic T cell proliferation in mixed cell cultures. This immunosuppressive effect seems to be mediated by inducing the generation of CD4+CD25+ regulatory T cells and soluble factors.