Effects of 15-lipoxygenase overexpressing adipose tissue mesenchymal stem cells on the Th17 / Treg plasticity

15-lipoxygenase (15-LOX) is a critical enzyme that allows the direction of arachidonic acid metabolism to change from inflammation into the resolution. This study aims to reveal how the immunomodulation properties of mesenchymal stem cells (MSC) alter by the 15-LOX overexpression. For this purpose, peripheral blood mononuclear cells (PBMCs) isolated from seven healthy volunteers, and both MSCs and 15-LOX overexpressing MSCs (^15-LOXMSCs) were co-cultured at different cell ratios (1/1, 1/5 and 1/10). Alterations of CD4⁺Tbet⁺, CD4⁺Gata3⁺, CD4⁺RoRC2⁺, and CD4⁺FoxP3⁺ lymphocyte frequencies were detected by flow cytometry, and IFN-γ, IL-4, IL-6, IL-10, IL-17a, TGF-β and LXA₄ levels of medium supernatants were measured by ELISA method. According to our findings, MSC and ^15-LOXMSCs have a suppressive effect on PHA activated PBMCs. However, as the ratio of PBMCs increased, the effects of ^15-LOXMSCs increased significantly, while the effects of MSCs decreased. The most notable effect of the 15-LOX modification was the significant reduction in IL-6, IL-10 and IL-17a expression and the accompanying increase in TGF-β and LXA₄ levels. We also observed a similar situation between CD4⁺RoRC2⁺ and CD4⁺FoxP3⁺ cell frequencies. These data suggested that the effects of MSCs on the balance of Th17 / Treg could change by the 15-LOX overexpression, and this might be in favor of the Treg cells.