TBI-associated acute lung injury is associated with downregulation of miRNA-362

BACKGROUND: – Traumatic brain injuries (TBIs) are a common cause of morbidity and mortality after major trauma. In addition to local injury effects, TBI is associated with a systemic inflammatory response and acute lung injury (ALI), which increases mortality and worsens neurological outcomes. The exact mechanism of this ALI is not known. Extracellular vesicles (EVs) are small cell–derived particles involved in cell-cell communication that carry a wide variety of payloads, including proteins and microRNAs (miRNAs), which can mediate inflammation. We sought to characterize EV-derived miRNAs associated with TBI-induced ALI. METHODS: – C57BL/6J mice underwent controlled cortical impact as a TBI injury model or sham procedure (anesthesia only). Bronchoalveolar lavage fluid (BALF) was then collected 4 hours postinjury. ALI after injury was determined via BALF protein concentration and H&E lung histology grading. BALF EVs were isolated using size exclusion chromatography, and EV concentration was confirmed via vesicle flow cytometry. EV miRNA sequencing was performed, comparing sham and injured mice. The effect of miR-362-3′ on lung epithelium was evaluated using proteome profiler and western blot analysis. RESULTS: – ALI after TBI injury was demonstrated by increased total protein concentration in BALF (p=0.006) and increased lung histologic injury score (p<0.0001). EVs were isolated using size exclusion chromatography and verified with vesicle flow cytometry. miRNA sequencing of BALF EVs demonstrated downregulation of 17 different miRNAs, most notably miRNA-362-3′. Treatment of MLE-12 with miRNA-362-3′ loaded EVs resulted in the downregulation of the proinflammatory cytokine TIMP-1. CONCLUSIONS: – We successfully identified multiple downregulated miRNAs from BALF in an in vivo model of TBI-induced ALI. Treatment with one of these downregulated miRNAs, miRNA-362-3′, resulted in the downregulation of TIMP-1 in lung epithelial cells. This suggests that the downregulation of miR-362-3′ contributes to TBI-induced ALI. (J Trauma Acute Care Surg. 2026;100:779–786.