A simple method to identify bone marrow mesenchymal stromal cells with a high immunosuppressive potential

Background: The beneficial activity of mesenchymal stromal cells (MSC) in allogeneic hematopietic stem cell transplantation requires a correct use in terms of cell dose and timing of infusion and the identification of biomarkers for selection. The immunosuppressive bone marrow derived BM-MSC functions has been associated with the production of soluble HLA-G molecule (sHLA-G), via interleukin-10 (IL-10). We established a reliable method to evaluate BM-MSC HLA-G expression without the influence of peripheral blood mononuclear cells (PBMCs). Methods: Thirteen BM-MSCs from donors were activated with recombinant IL-10 or co-cultured with 10 different phytohaemaglutinin treated-peripheral blood mononuclear cells (PHA-PBMCs). Membrane-bound and soluble HLA-G expression was evaluated by flow cytometry and ELISA respectively; lymphoproliferation was measured by (methyl-3H) Thymidine. Results: The results demonstrated the ability of IL-10 to stimulate both membrane-bound and soluble HLA-G production by BM-MSCs. The levels of HLA-G expression induced by IL-10 in BM-MSCs were associated with the inhibition of PHA-PBMC proliferation (sHLA-G: p= 0.0008, r=0.9308; membrane HLA-G: p= 0.0005, r= 0.9502). Discussion: These results propose the evaluation of sHLA-G production in IL-10-treated BM-MSC cultures as a possible marker of immunoregulatory functions.