Intranasal delivery of BDNF-loaded small extracellular vesicles for cerebral ischemia therapy

Mesenchymal stem cells (MSCs) have shown promise for the therapy of cerebral ischemia in animal studies and clinical trials, yet their clinical application still faces many challenges. Utilizing small extracellular vesicles (sEVs) may overcome these challenges. In the study, we overexpressed brain-derived neurotrophic factor (BDNF) in cultured MSCs and purified sEVs using anion exchange chromatography. In an ischemic stroke mouse model, sEVs selectively targeted the peri-infarct region after intranasal administration, and BDNF loading enhanced the efficacy of sEVs in improved functional behavior, neural repair indicated by infarct volume reduction, increased neurogenesis, angiogenesis, synaptic plasticity, and fiber preservation, as well as decreased inflammatory-cytokine expression and glial response. Intranasal administration of sEVs and BDNF-sEVs resulted in upregulation of neuroprotection-related genes and downregulation of inflammation-related genes, and BDNF-sEVs treatment activated the BDNF/TrkB signaling in the ischemic brain. Transcriptomic and proteomic analysis of sEVs and BDNF-sEVs disclosed abundant proteins and miRNAs involved in neuroprotection and anti-inflammation, and BDNF-sEVs showed different characteristics from sEVs. In conclusion, intranasal delivery of sEVs-loaded BDNF is a promising alternative strategy for the therapy of cerebral ischemia.