Inhibitory Effects of Menstrual Blood Stromal Stem Cells on Generation of Dendritic Cells from Peripheral Blood Monocytes

Menstrual blood stromal stem cells (MBSCs) share some phenotypic and functional similarities with mesenchymal stem cells (MSCs). MSCs are shown to inhibit either the function or generation of different immune cells, including dendritic cells (DCs). However, data regarding MBSCs’ potential effects on immune system cells are elusive. Here, we examine whether MBSCs affect the generation of human monocyte-derived DCs. Menstrual blood samples were collected from apparently healthy women on the second day of their menstrual cycles. The adherent portions were subcultured to omit unwanted cells and obtain MBSCs. Magnetically-isolated peripheral blood monocytes were differentiated towards DCs through treatment with recombinant granulocyte monocyte colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4) in the presence or absence of MBSCs. After five days, monocyte-derived DCs were analyzed for the expression of surface markers by flow cytometry. IL-6 level was determined in the co-culture supernatants. Co-culture with MBSCs significantly down regulated the expression of DC marker (CD1a) and up regulated the expression of monocyte marker (CD14) on monocyte-derived DCs compared with the control group. IL-6 level was shown to be significantly higher in the supernatant of the monocyte-MBSC co-culture. Collectively, this is the first study to show the inhibitory impacts of MBSCs on the generation of DCs. IL-6 could be viewd as a potential factor mediating this effect. Regarding the known advantages over MSCs, MBSCs could be considered as a promising future candidate for immunomodulatory purposes in the clinical setting.