Umbilical cord blood (UCB) gained high interest as a source of stem cells for use in cellular therapies. The immune modulatory effect of mesenchymal stem cells (MSCs) originating from bone marrow, adipose tissue and amniotic membrane was previously proved. In this study we aimed at isolation of MSCs from UCB, and evaluate their immune-modulatory effect on peripheral blood lymphocytes proliferation by two different techniques; 5-Bromo-2-deoxyuridine (Brdu) enzyme linked immunsorbant assay (ELISA) and Carboxy Fluorescine diacetate Succinimidyl Ester (CFSE) flow cytometric technique. MSCs were isolated from UCB, propagated until passage 4, characterized for cell surface markers by flow cytometry and ability of mesodermal differentiation was induced towards osteocytes and adipocytes. The immunosuppressive effect on peripheral blood lymphocytes was examined by co-culturing Mitomycin C treated UCB MSCs with mitogen-stimulated lymphocytes for 72 hours. Thereafter, proliferation of lymphocytes was detected by CFSE flow cytometry and colorimetric ELISA. The level of cytokines in cell culture supernatant was also assayed to detect the possible mechanism of immunomodulation. UCB MSCs were able to suppress mitogen-stimulated lymphocytes proliferation; this is due to cell-cell contact as well as due to cytokines secretion. The level of transforming growth factor beta (TGFβ) and interleukin (IL) 10 increased and the level of interferon gamma (IFNγ) decreased in the supernatant of co-cultures. UCB MSCs suppressed the proliferation of mitogen-stimulated lymphocytes. However further in vivo studies are still required to fully evaluate the immune-modulatory effect of UCB MSCs.
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