Small Extracellular Vesicle Signaling and Mitochondrial Transfer Reprograms T Helper Cell Function in Human Asthma.

Small extracellular vesicles (sEVs) are known to orchestrate cell-cell communication, but the role of sEV signaling via mitochondria in perpetuating asthmatic airway inflammation is unknown. Myeloid-derived regulatory cells (MDRCs) are known to control CD4+ T cell responses in asthma. We demonstrate that airway MDRC-derived sEVs from asthmatics mediate T cell receptor engagement and transfer of mitochondria that induce antigen-specific activation and polarization of Th17 and Th2 cells; these cells are drivers of chronic airway inflammation in asthma. CD4+ T cells internalize sEVs containing mitochondria predominantly by membrane fusion, and blocking mitochondrial oxidant signaling in MDRC-derived sEVs mitigates T cell activation. Reactive oxygen species-mediated signaling that elicits T cell activation in asthmatics is sEV-dependent. Additionally, a Drp1-dependent mechanism in pro-inflammatory MDRCs promotes mitochondrial packaging within sEVs, which then co-localize with the polarized cytoskeleton and mitochondrial networks in recipient T cells. Importantly, intranasal transfer of mitochondria packaged sEVs enhances airway inflammation and Th polarization in vivo in a murine model of asthma. Thus, our studies indicate a previously unrecognized role for mitochondrial fission and sEV-mediated mitochondrial transfer-mediated signaling in dysregulated T cell activation and Th cell polarization in asthma which could constitute a novel therapeutic target.