After the impact: extracellular vesicles and the opportunity to limit secondary brain injury.

Traumatic brain injury triggers inflammatory processes that can persist long after the mechanical insult. This commentary examines the award-winning study by Kodali and colleagues, in which a single intranasal dose of human mesenchymal stromal cell-derived extracellular vesicles 90 min after controlled cortical impact suppressed NLRP3-p38/MAPK signalling and prevented chronic cognitive and affective dysfunction in mice. The study combines a clinically attractive administration route with durable functional effects, helping to explain its rapid influence. Translation will nevertheless depend on establishing human intranasal delivery, defining active cargo and mechanisms, and developing reproducible potency and release assays for a heterogeneous biological product. The work is important because it suggests that early modulation of post-traumatic inflammation may alter the long-term course of brain injury.