[Alteration of MMSC's immunosupression at reduced o2: direct cell-to-cell contacts and paracrine regulation]

During last two decades multipotent mesenchymal stromal (stem) cells (MMSCs) were not only identified and isolated from many tissues, but their immunopriviledge and immunosupressive potential along with high proliferative activity and multilineage differentiation were demonstrated. At the same time there is an increasing evidence of the MMSC plasticity due to a wide range of microenvironmental factors: extracellular matrix, cell-to-cell interactions, oxygen content, etc. In this paper, a comparative study of direct cell-to-cell and paracrine effects of MMSCs on human PHA-activated peripheral blood mononuclear cells (MNCs) in the standard (20%) and reduced to 5% O2 concentration in the culture medium was conducted. It is shown that after coculture with MMSCs the proliferative activity of PHA-MNCs, the share of HLA-DR(+) -T cells and IL-6, -8 and TNF-alpha concentrations were reduced, but IL-10 and IFN-gamma were increased in the medium. Potentiating effect on the MMSC immunomodulating properties was noted at low oxygen, which is of great importance for increasing the efficiency of immunosuppression.