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

Background: Allergic asthma is one of the chronic inflammatory diseases and is generally induced by CD4+ T helper 2 cells (Th2) in the context of persistent inhaled stimuli. 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, whether MSC-sEV play a role on DCs in airway inflammation is still unclear. Methods: We isolate 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 moDCs in mouse lung in response to HDM. MSC-sEV also decreased the activation of moDCs induced in vitro including the expression of co-stimulatory molecules and cytokines secretion. Furthermore, we identified that DCs were able to take MSC-sEV in vitro and in vivo. Mechanistically, using bulk RNA-sequencing, we found that MSC-sEV played roles in the metabolic pathway of murine DCs. Using extracellular flux analysis, we found that MSC-sEV increased the requirement of oxidative phosphorylation on moDCs. Importantly, MSC-sEV displayed similar effects on human moDCs including decreased co-stimulatory molecular and cytokine production. 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. To identify how sEV regulated DC activation, the analysis of global genes was applied to understand the mechanism. We compared geomatic profiles of PBS or sEV-treated BMDCs.