Intra-arterial delivery of MSC-derived extracellular vesicles in the post-thrombectomy setting attenuates ischemic brain injury

Background Ischemic stroke remains a major global cause of mortality and disability. Although the development of recombinant tissue plasminogen activator (rt-PA) and endovascular thrombectomy has improved clinical outcomes, nearly half of patients still experience unfavorable outcomes, underscoring the need for innovative therapeutic strategies. In the present study, we investigated intra-arterially administered human amniotic mesenchymal stromal cells (MSCs)–derived extracellular vesicles (EVs) immediately after ischemic stroke, mimicking successful recanalization following thrombectomy, and evaluated their neuroprotective effects. Methods EVs were isolated from the conditioned media of amnion-derived MSCs. Middle cerebral artery occlusion was induced in 8-week-old Sprague–Dawley rats using an intraluminal filament model, followed by complete recanalization 2 h after ischemia. A total of 5 × 10 9 EV particles suspended in 500 µL of phosphate-buffered saline (PBS), or PBS alone as a control, were administered intra-arterially through the same artery immediately after reperfusion. Neurological function was assessed for up to 7 days after MCAO, followed by histological analyses of inflammatory responses and neutrophil extracellular traps (NETs) formation. Biodistribution of EVs was evaluated using positron emission tomography/computed tomography (PET/CT) imaging with 64 Cu-labeled EVs. Blood–brain barrier (BBB) integrity was assessed using Evans blue extravasation, and quantitative proteomic analyses were performed using both brain capillary–enriched fractions and whole-brain tissue to characterize changes in the host brain microenvironment. Results The EV group demonstrated significantly improved neurological recovery and a lower mortality rate compared with controls, whereas body weight recovery and infarct volume did not reach statistical significance. Histological analyses revealed significant reductions in inflammation (Iba1, CD68) and apoptosis (TUNEL) in the EV-treated group. EV group further demonstrated preserved BBB function, and suppressed intraparenchymal NETs formation. Biodistribution analysis showed that the majority of EVs accumulated in the liver as early as 1 h after administration, although signals were also detected in the ipsilateral brain hemisphere. Proteomic analyses demonstrated upregulation of endopeptidase inhibition cascades and mitochondrial activities, suggesting a mechanistic link to the inhibition of NETs formation, and preservation of cell functions respectively. Conclusions MSC-derived EVs were successfully delivered to the brain via intra-arterial administration and attenuated ischemic brain injury, at least in part, through preservation of BBB integrity and inhibition of NET formation.