Endocrine Abstracts

Background and aims: Mesenchymal stem cells (MSCs) exert an immunosuppressive effect on immune system and can abrogate in vitro the pro-inflammatory Th1 response to islet antigen GAD in type 1 diabetes by impairing the production of IFN-gamma. The mechanism may involve paracrine factors. Microvesicles (MVs) released from MSCs may account for this paracrine mechanism through a horizontal transfer of mRNA and microRNA. In the present study we evaluated whether MSC-derived-MVs exert immunomodulatory effect similar to that of MSCs on T cell responses against GAD in type 1 diabetes.

Methods: MVs were purified from supernatants of human MSCs and were characterized by cytofluorimetic and gene array analyses. Peripheral blood mononuclear cell (PBMCs) were obtained from 4 type 1 diabetic patients at disease onset with a positive IFN-gamma response to GAD65 stimulation by ELISPOT assay. PBMCs GAD65-pulsed were incubated with or without MV followed by IFN-gamma ELISPOT. Levels of PGE2, TGF-beta, IL-10, IFN-gamma, IL-6 in supernatants were measured by ELISA.

Results: When determined by Nanosizer, the size of MVs has a mean value of 158 nm. MVs showed adhesion molecules expressed on MSC-membrane and contained mRNA and in particular mRNA related to immune regulation. MVs labeled were incorporated by PBMC, as shown by confocal microscopy. Incubation of PMBCs obtained from the GAD-responder patients with MVs, resulted in a significant decrease in the number of IFN-gamma spots. Levels of IFN-gamma, IL-6, in supernatants of GAD65-pulsed PBMCs incubated with MVs were decreased compare to GAD65-pulsed PBMCs alone. Levels of PGE2, TGF-β and IL-10 were significantly increased compare to GAD65-pulsed PBMCs alone.

Conclusions: These results provide evident that MSC-derived-MVs inhibited in vitro pro-inflammatory Th1 response to an islet antigenic stimulus, in diabetic patients, possibly mediated by PGE2 and TGF-β. MVs induce IL-10 secretion, suggesting a possible switch to an anti-inflammatory Th2signalling of T cells.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.