Mesenchymal stromal cells‐derived small extracellular vesicles modulate DC function to suppress Th2 responses via IL‐10 in patients with allergic rhinitis

Mesenchymal stromal cells (MSCs) are well known for their immunoregulatory roles on allergic inflammation particularly by acting on T cells, B cells, and dendritic cells (DCs). MSC‐derived small extracellular vesicles (MSC‐sEV) are increasingly considered as one of the main factors for the effects of MSCs on immune responses. However, the effects of MSC‐sEV on DCs in allergic diseases remain unclear. MSC‐sEV were prepared from the induced pluripotent stem cells (iPSC)‐MSCs by anion‐exchange chromatography, and were characterized with the size, morphology, and specific markers. Human monocyte‐derived DCs were generated and cultured in the presence of MSC‐sEV to differentiate the so‐called sEV‐immature DCs (sEV‐iDCs) and sEV‐mature DCs (sEV‐mDCs), respectively. The phenotypes and the phagocytic ability of sEV‐iDCs were analyzed by flow cytometry. sEV‐mDCs were co‐cultured with isolated CD4(+)T cells or peripheral blood mononuclear cells (PBMCs) from patients with allergic rhinitis. The levels of Th1 and Th2 cytokines produced by T cells were examined by ELISA and intracellular flow staining. And the following mechanisms were further investigated. We demonstrated that MSC‐sEV inhibited the differentiation of human monocytes to iDCs with downregulation of the expression of CD40, CD80, CD86, and HLA‐DR, but had no effects on mDCs with these markers. However, MSC‐sEV treatment enhanced the phagocytic ability of mDCs. More importantly, using anti‐IL‐10 monoclonal antibody or IL‐10Rα blocking antibody, we identified that sEV‐mDCs suppressed the Th2 immune response by reducing the production of IL‐4, IL‐9, and IL‐13 via IL‐10. Furthermore, sEV‐mDCs increased the level of Treg cells. Our study identified that mDCs treated with MSC‐sEV inhibited the Th2 responses, providing novel evidence of the potential cell‐free therapy acting on DCs in allergic airway diseases.