Intranasal delivery of hypoxia-preconditioned extracellular vesicles derived from BMSCs alleviates neuroinflammation and brain dysfunction in TBI.

Traumatic brain injury (TBI) leads to secondary injuries, such as neuroinflammation and brain dysfunction, which is a critical challenge in clinical treatment. The use of bone marrow mesenchymal stem cells (BMSCs) is one of the potential strategies to treat TBI by alleviating inflammation, reducing neuronal loss, and promoting brain function recovery. Extracellular vesicles (EVs) released by BMSCs are regarded as an ideal alternative to cell therapy. This study showed that hypoxia significantly enhanced the release of EVs from BMSCs, and hypoxia- preconditioning (H-EVs) treatment significant effects on promoting microglial M2 polarization, improving endothelial cell activity, and inhibiting the formation of neutrophil extracellular traps, ultimately accelerating brain function recovery. Mechanistically, single-cell sequencing revealed a significant reduction in specificity protein 1 (SP1) expression and a change in the proportion of infiltrating inflammatory cell subsets in brain tissues after the H-EVs treatment. Hypoxia-preconditioning changed the miRNA microarray analysis results in H-EVs, such that miR-145-5p negatively regulated nuclear factor kappa-B (NF-κB) by targeting SP1, induced microglial M2 polarization, alleviated endothelial cell dysfunction, and promoted brain function recovery. Intranasal delivery of hypoxia-induced BMSC-EVs showed great potential in the treatment of secondary TBI and revealed a novel mechanism by which miR-145-5p regulates inflammatory response and intercellular communication by inhibiting the SP1/NF-κB axis.