Extracellular vesicles from adipose-derived mesenchymal stem cells prevent high glucose-induced retinal ganglion cell pyroptosis through a microRNA-26a-5p-dependent mechanism.

OBJECTIVE: Mesenchymal stromal/stem cells have neuroprotective effects that limit damage to the retina, which is predominantly mediated by the released extracellular vesicles (EVs). This study aims to investigate the protective effect of adipose-derived mesenchymal stem cell-derived EVs (ADSC-EVs) against pyroptosis of retinal ganglion cells (RGCs). METHODS: ADSC-EVs were isolated and then characterized. Mouse primary RGCs exposed to high glucose (HG) were applied for in vitro experiments. miR-26a-5p expression in RGCs after ADSC-EV treatment was determined by RT-qPCR. Target relation between miR-26a-5p and histone deacetylase 4 (HDAC4) was identified by luciferase reporter assay. miR-26a-5p blockad and HDAC4 ectopic expression experiments were conducted to clarify their functions in the pyroptosis of RGCs. The pyroptosis-associated protein GSDMD-N, inflammatory factors, and cell death were further evaluated by western blot, ELISA, and LDH assays, respectively. RESULTS: Exposure to HG reduced RGC viability and increased cell death, GSDMD-N protein level, and IL-1β and IL-18 levels, indicating pyroptosis induction. However, these HG-caused alterations could be reversed by ADSC-EVs. ADSC-EVs transferred miR-26a-5p into RGCs where miR-26a-5p targeted HDAC4 to limit its expression and enhance histone H3 lysine 27 acetylation (H3K27ac) modification at the nuclear factor erythroid 2-related factor 2 (Nrf2) promoter region. This effect contributed to increases in Nrf2 protein level and nuclear translocation. Importantly, decreased H3K27ac modification at the Nrf2 promoter region could partially abrogate the inhibiting effect of ADSC-EVs on HG-induced RGC pyroptosis. CONCLUSION: Overall, our findings reveal the beneficial effects of ADSC-EVs shuttling miR-26a-5p on HG-induced RGCs and determine a potential mechanism responsible for pyroptosis.