Adipose stem cells derived extracellular vesicles alleviate retinal excitotoxicity via miR-23a-5p/PLCD1/PKCA/GluA2 axis: a potential therapeutic strategy

BACKGROUND: Despite excitotoxicity being a pivotal pathological mechanism in various retinal diseases, effective clinical interventions remain limited. Previous study has shown that adipose stem cell-derived extracellular vesicles (ADSC-EVs) can alleviate glutamate-induced retinal ganglion cells (RGCs) death by suppressing protein kinase C alpha (PKCA) pathway and increasing the expression of α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptors (AMPARs) subunit 2 (GluA2) on the cell membrane, but the mechanisms remain unexplored. METHODS: To clarify the molecular processes involved in ADSC-EVs-mediated intracellular calcium balance, we isolated ADSC-EVs using ultrafiltration and ultracentrifugation, and characterized these vesicles by transmission electron microscopy, nanoparticle tracking analysis, and flow cytometry. Small RNA sequencing was performed on glutamate-injured rat retinal precursor (R28) cells pre-treated with ADSC-EVs or PBS. Through bioinformatic analysis, we identified candidate microRNAs and predicted their potential target genes. The regulatory effects of microRNA were confirmed using propidium iodide staining, Fluo-4AM staining, western blotting, and immunofluorescence. Additionally, the RGCs counting and visual function tests were employed to evaluate the therapeutic efficacy of the microRNA in the glutamate-induced SD rat - animal model. RESULTS: Our results demonstrated that pre-treatment with ADSC-EVs led to a significant increase in the expression levels of miR-127-3p, miR-181b-1-3p, miR-199a-3p/5p, miR-23a-5p, miR-23b-5p, and miR-486 in R28 cells. Bioinformatic analyses suggest that miR-23a-5p may contribute to regulating the calcium overload by inhibiting the expression of phospholipase C delta 1 (PLCD1). Overexpression of miR-23a-5p or pre-treatment with ADSC-EVs modulated the expression of GluA2 on the cell membrane through inhibiting the PLCD1/PKCA/GluA2 axis, thereby reducing intracellular calcium levels and diminishing R28 cell death. In contrast, inhibition of miR-23a-5p expression partially reversed the regulatory effects of ADSC-EVs on calcium concentration and cell viability. Furthermore, our findings suggest that overexpression of miR-23a-5p in retina alleviated glutamate-induced RGCs death and visual function impairment, whereas suppression of miR-23a-5p exacerbated glutamate-induced RGCs death. CONCLUSION: ADSC-EVs delived miR-23a-5p mitigate glutamate-induced RGCs damage by inhibiting the PLCD1/PKCA/GluA2 axis. Targeting this miR-23a-5p-mediated axis may therefore represent a promising therapeutic approach for excitotoxic RGCs injury.