Overexpression of COX-2 but not indoleamine 2,3-dioxygenase-1 enhances the immunosuppressive ability of human umbilical cord-derived mesenchymal stem cells

Owing to their immunosuppressive properties mesenchymal stem cells (MSCs) are widely applicable in the treatment of autoimmune disease. The aim of this study was to investigate whether the indoleamine 2,3-dioxygenase-1 (ID 0-1) and cyclooxygenase-2 (COX-2) genes enhanced the immunosuppressive functional ability of MSCs following stable transfection. To strengthen the immunomodulatory ability of MSCs, ID 0-1 and COX-2 were overexpressed in umbilical cord progenitor cell-derived MSCs using recombinant plasmids and electroporation. RT-qPCR analysis and western blotting confirmed the expression of IDO-1 and COX-2 in transfected MSCs. Further functional assays in co-culture experiments, including lymphocyte proliferation and cytotoxicity assays showed that COX-2-transfected MSCs possessed more potent immunomodulatory cells than the untreated MSCs, or MSCs transfected with IDO-1. Additionally, synthesis of interferon-gamma and tumor necrosis factor-alpha (TNF-alpha) was significantly inhibited in lymphocytes co-cultured with COX-2-transfected MSCs, which was consistent with changes in immune-related genes in MSCs. An enhanced expression of IDO-1, COX-2, heme-oxygenase-1, inducible nitric-oxide synthase, TNF-alpha-stimulated gene/protein-6, transforming growth factor-beta (TGF-beta), human leukocyte antigen molecule 5 (HLA-G5) and interleukin-10 (IL-10) was identified following COX-2 transfection. We showed that the overexpression of COX-2 enhanced the immunosuppressive function of MSCs. COX-2-modified MSCs more potently inhibited the activation and proliferation of peripheral blood mononuclear cells.