Aims/hypothesis: Mesenchymal stem cells (MSCs) have been shown to abrogate in vitro the proinflammatory response in type 1 diabetes. The mechanism involves paracrine factors, which may include microvesicles (MVs). We evaluated whether MVs derived from heterologous bone-marrow MSCs exert an immunomodulatory effect on T cell responses against GAD (glutamic acid decarboxylase) antigen in type 1 diabetes.
Methods: MVs were purified from heterologous human MSCs by differential centrifugation. Peripheral blood mononuclear cells (PBMCs) were obtained from patients with type 1 diabetes at disease onset, and responses to GAD65 stimulation were assessed by IFN-γ enzyme-linked immunosorbent spot analysis. Levels of cytokines and prostaglandin E2 (PGE2) were measured in the supernatant fraction, and T helper 17 (Th17) and regulatory T cell analysis was performed.
Results: MVs were internalised by PBMCs, as assessed by confocal microscopy and flow cytometry analyses. MVs significantly decreased IFN-γ spots and levels in GAD65-stimulated PBMCs, and significantly increased transforming growth factor-β (TGF-β), IL-10, IL-6 and PGE2 levels. Furthermore, MVs decreased the number of Th17 cells and the levels of IL-17, and increased FoxP3(+) regulatory T cells in GAD65-stimulated PBMCs.
Conclusions/interpretation: These results provide evidence that MSC-derived MVs can inhibit in vitro a proinflammatory response to an islet antigenic stimulus in type 1 diabetes. The action of MVs involves PGE2 and TGF-β signalling pathways and IL-10 secretion, suggesting a switch to an anti-inflammatory response of T cells.