Inhalation of mesenchymal stromal cell-derived extracellular vesicles activates macrophage polarization through the miR-22-3p/NLRP3/IL-1β pathway, ameliorating lung ischemia - reperfusion injury.

BACKGROUND: Lung ischemia-reperfusion injury (IRI) is a major contributor to primary graft dysfunction (PGD) after lung transplantation. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as promising therapeutic agents in inflammatory diseases by ameliorating tissue damage and promoting repair. However, the anti-inflammatory efficacy of these approaches and the underlying mechanisms in lung ischemia-reperfusion injury remain incompletely understood. METHODS: The protective effects of mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) against lung ischemia-reperfusion injury were evaluated using two delivery approaches, inhalation and intravenous injection. Both in vivo and in vitro models were employed to assess the biological activity of MSC-EVs and to elucidate the underlying molecular mechanisms. In addition, a rat orthotopic lung transplantation (OLT) model was established to further examine the translational relevance of MSC-EVs. RESULTS: MSC-EVs treatment significantly ameliorated lung IRI, with inhalation showing superior efficacy over intravenous delivery. Mechanistically, miR-22-3p within MSC-EVs targeted macrophage NLRP3, suppressing activation of the NLRP3/Caspase-1/IL-1β pathway and promoting M2 polarization. The protective efficacy was confirmed in a clinically relevant rat OLT model, underscoring their translational potential CONCLUSIONS: Our findings indicate that inhaled MSC-derived extracellular vesicles attenuate lung ischemia-reperfusion injury by promoting macrophage polarization via the miR-22-3p/NLRP3/IL-1β pathway, supporting their potential as a cell-free therapeutic approach to mitigate primary graft dysfunction after lung transplantation.