MSC-small extracellular vesicles alleviated Th2-airway inflammation by regulating the metabolism of DCs in mice

BACKGROUND: Allergic airway inflammation is one of the chronic inflammatory diseases and is generally dominated by T helper 2 cells (Th2). Dendritic cells (DCs) are essential to mounting the Th2-mediated airway inflammation by presenting inhaled antigens to prime CD4+ T cells. Small extracellular vesicles (sEV) derived from mesenchymal stem cells (MSCs) exhibited great interest in intractable diseases. However, the effects and mechanisms of MSC-sEV on DCs in airway inflammation is still unclear. METHODS: We isolated MSC-sEV using anion-exchange chromatography. Mouse bone marrow-derived DCs (BMDCs) and human monocyte-derived DCs (moDCs) were used to study the effects of MSC-sEV on dendritic cell surface molecules and their cytokine release. Mice were sensitized with house dust mites (HDM) to induce airway inflammation, and treated with MSC-sEV, the effects of sEV on murine DCs were identified. Extracellular flux analysis techniques were used to study the effects of MSC-sEV on the metabolic state of dendritic cells. RNA sequencing to study altered gene expression in BMDCs after MSC-sEV treatment. RESULTS: MSC-sEV mitigated the accumulation of Th2-associated cDC2s and moDCs in mouse lung in response to HDM. In vitro, MSC-sEV treatment significantly attenuated the activation of BMDCs. Furthermore, we identified that DCs were able to take MSC-sEV in vitro and in vivo. Mechanistically, MSC-sEV exerted regulatory effects on the metabolic pathways of murine DCs, specifically enhancing the reliance on oxidative phosphorylation of BMDCs. Importantly, MSC-sEV displayed similar effects on human moDCs. CONCLUSIONS: MSC-sEV are able to alter the metabolic state of DCs, favoring DCs to maintain OXPHOS (oxidative phosphorylation) rather than glycolysis, thereby reducing DCs-initiated inflammatory responses and attenuating Th2 lung inflammation, suggesting MSC-sEV can be a potential clinical therapy for airway inflammation.