miR-146a-Enriched Extracellular Vesicles Attenuate Neuroinflammation and Promote Recovery After Ischemic Stroke

Background: Ischemic stroke triggers a strong neuroinflammatory response involving cytokines, which are fundamentally involved in tissue damage and repair. Objectives: The present study was designed to investigate the therapeutic potential of miR-146a-enriched extracellular vesicles derived from bone marrow mesenchymal stem cells (BMSC-EVs) in a rat model of middle cerebral artery occlusion (MCAO). Methods: miR-146a was transfected into BMSCs using Lipofectamine 3000. Extracellular vesicles (EVs) were isolated from transfected BMSCs using ultracentrifugation. Thirty rats were randomly assigned to three groups (n = 10 per group): (1) Control (received FBS), (2) miR-control EVs (miR-NC), and (3) miR-146a-enriched EVs, administered intravenously post-ischemia. Neurological deficits were evaluated with the Bederson score, and cytokine levels, including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin (IL)-6, IL-10, as well as transforming growth factor β (TGF-β), were measured in splenocyte culture and brain tissues using enzyme-linked immunoassay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR), respectively. The expression of Interleukin-1 Receptor-Associated Kinase 1 (IRAK1), Tumor Necrosis Factor Receptor-Associated Factor 6 (TRAF6), and nuclear factor kappa B (NF-κB) was also measured using RT-PCR. Results: Results showed that EVs enriched in miR-146a significantly decreased pro-inflammatory cytokines, TNF-α, IFN-γ, and IL-6, and increased anti-inflammatory markers, IL-10 and TGF-β, when compared with miR-control EVs and FBS-treated groups. miR-146a-EV-treated rats also displayed better Bederson scores, which reflected better neurological recovery. Results also demonstrated that miR-146a-enriched EVs downregulated IRAK1, TRAF6, and NF-κB signaling in ischemic brain tissue. Conclusions: These results indicate that miR-146a overexpression in BMSC-EVs can significantly inhibit neuroinflammation and promote functional improvement in ischemic stroke models, supporting its targeted therapeutic potential.