Bone marrow stromal cells-derived exosomes reduce neurological damage in traumatic brain injury through the miR-124-3p/p38 MAPK/GLT-1 axis

Abstract

Background: Mounting evidence indicates that stem cell-derived exosomal miRNAs have therapeutic effects on traumatic brain injury (TBI). This research is focused on exploring the molecular processes of miR-124-3p obtained from bone marrow stromal cells-derived exosomes (BMSCs-Exos) in attenuating posttraumatic glutamate-mediated excitotoxicity.

Methods: We created a TBI rat model and analyzed the expression profile of miRNA through miRNA microarray. The miR-124-3p and p38 MAPK levels were analyzed utilizing RT-qPCR and western blotting. Dual-luciferase reporter (DLR) assay showed the targeting relationship between miR-124-3p and p38 MAPK. We subsequently conducted a TUNEL assay and flow cytometry to evaluate the neuronal apoptotic rate in an in vitro glutamate-mediated excitotoxicity model treated with BMSCs-Exos enriched with miR-124-3p (BMSCs-Exos^miR-124-3p). Moreover, the levels of p38 MAPK and glutamate transporter-1 (GLT-1) were measured by western blotting. Furthermore, BMSCs-Exos^miR-124-3p were administered to the TBI rats, and their neuroprotective effects were observed using western blotting, immunohistochemistry, histological staining, magnetic resonance imaging (MRI), and Morris water maze (MWM).

Results: The results revealed that the brains of TBI rats exhibited lowered miR-124-3p and enhanced p38 MAPK levels. DLR assay demonstrated miR-124-3p's role in targeting p38 MAPK and negatively regulating its expression. In vitro and in vivo studies confirmed that BMSCs-Exos^miR-124-3p attenuated glutamate-mediated excitotoxicity by downregulating p38 MAPK and upregulating GLT-1 expressions via transferring exosomal miR-124-3p. Moreover, histopathological evaluation and MRI results showed that BMSCs-Exos^miR-124-3p remarkably alleviated neuronal cell death and minimized the lesion volumes post-TBI. MWM outcomes illustrated that BMSCs-Exos^miR-124-3p treatment could substantially improve neurological function post-TBI. Furthermore, the effects of treatment with p38 MAPK inhibitor SB203580 were similar to BMSCs-Exos^miR-124-3p.

Conclusion: Overall, the outcomes of the current report highlighted that BMSCs-Exos^miR-124-3p can lead to the upregulation of GLT-1 in TBI rat models by inhibiting the p38 MAPK signaling pathway, hence alleviating glutamate-mediated excitotoxicity and attenuating neurological damage post-TBI.

Keywords: Bone marrow stromal cells; Exosomes; Glutamate excitotoxicity; Traumatic brain injury; miR-124-3p; p38 MAPK.