Hypoxia Pre-Conditioned Embryonic Mesenchymal Stem Cell Secretome Reduces IL-10 Production by Peripheral Blood Mononuclear Cells

Background: Mesenchymal stem cells (MSCs) are important candidates for MSC-based cellular therapy. Current paradigm states that MSCs support local progenitor cells in damaged tissue through paracrine signaling. Therefore, study of paracrine effects and secretome of MSCs could lead to the appreciation of mechanisms and molecules associated with the therapeutic effects of these cells. This study analyzed anti-inflammatory and immune-modulatory effects of MSC secretomes derived from embryonic stem cells (ESCs) and bone marrow cells after hypoxia and normoxia preconditioning. Methods: ESCs differentiated into MSCs and characterized by flow cytometry and differentiation into adipocytes and osteoblasts. The experimental groups consisted of individual groups of ESC-MSCs and BM-MSCs (bone marrow-derived mesenchymal stromal cells), which were preconditioned with either hypoxia or normoxia for 24, 48 and 72 h.  After collecting the cell-free medium from each treatment, secretomes were concentrated by centrifugal filters. Using a peripheral blood mononuclear cell (PBMC) assay and ELISA, IL-10 concentration in PBMCs was evaluated after their incubation with different secretomes from preconditioned and non-preconditioned MSCs. Results: A significant difference was observed between ESC-MSC normoxia and ESC-MSC hypoxia in IL-10 concentration, and normoxia secretomes increased IL-10 secretion from PBMCs. Moreover, the strongest IL-10 secretion from PBMCs could be detected after the stimulation by ESC-MSC conditioned secretomes, but not BM-MSC conditioned medium. Conclusions: Human hypoxia preconditioned ESC-MSC secretome indicated stronger immune-modulatory effects compared to BM-MSC conditioned medium. It could be suggested that induced MSCs confer less immune-modulatory effects but produce more inflammatory molecules such as tumor necrosis α, which needs further investigation.