Exosomal miR-148a-3p from adipose derived stem cells promotes microglial M2 polarization and alleviates traumatic brain injury via the TMEM9B/NF-κB axis

BACKGROUND Traumatic brain injury (TBI) remains a leading cause of death and disability worldwide, with no effective pharmacological therapy currently available.Adipose-derived stem cell exosomes (ADSC-Exos) have emerged as a promising cell-free therapeutic strategy, but the underlying molecular mechanisms, particularly the role of exosomal microRNAs (miRNAs) in regulating microglial polarization, are not fully understood.AIM To investigate whether ADSC-Exos alleviate TBI-induced neuroinflammation by delivering miR-148a-3p to microglia and promoting M2 polarization through the transmembrane protein 9B (TMEM9B)/nuclear factor-kappa B (NF-κB) pathway.METHODS ADSC-Exos were characterized by transmission electron microscopy, nanoparticle tracking analysis, and Western blot.A rat TBI model was established by the weight-drop method, and neurological recovery was assessed by the modified neurological severity score and Morris water maze.BV2 and primary microglial cells were stimulated with lipopolysaccharide to induce M1 polarization and then treated with ADSC-Exos or engineered exosomes.Subsequently, miRNA sequencing, quantitative reverse transcription polymerase chain reaction, Western blot, immunofluorescence, flow cytometry, dual-luciferase reporter assays, and functional rescue experiments were performed. RESULTSADSC-Exos significantly improved neurological function in TBI rats, reducing the Day 28 modified neurological severity score from 7.8 ± 1.2 (TBI) to 4.3 ± 0.9 (P < 0.001).In vitro, 4 / 42 ADSC-Exos were internalized by microglia and promoted a shift from M1 to M2 polarization, increasing the proportion of CD11b⁺CD206⁺ cells from 5.8% ± 0.6% to 32.5% ± 2.8% (P < 0.001).miRNA profiling identified miR-148a-3p as highly enriched in ADSC-Exos (4.8-fold vs ADSCs, P < 0.001).miR-148a-3p-mimic-exosomes recapitulated the antiinflammatory effects, and dual-luciferase reporter assay confirmed that miR-148a-3p directly targeted TMEM9B, reducing luciferase activity by 62% (P < 0.01).Overexpression of TMEM9B in the rescue experiment largely abrogated ADSC-Exo-induced M2 polarization.Mechanistically, ADSC-Exos suppressed the NF-κB pathway by reducing phosphorylated p65 and IκBα levels.CONCLUSION ADSC-Exo miR-148a-3p promotes microglial M2 polarization and attenuates TBI via specific inhibition of the TMEM9B/NF-κB signaling axis, highlighting this pathway as a novel therapeutic target for neuroinflammatory disorders.