Müller glia derived EVs promote neurite recovery of an enriched population of retinal ganglion like cells derived from hESC retinal organoids after damage

Membrane-bound extracellular vesicles (EVs) released by Müller glia contain microRNA (miRNA) and proteins with the potential to be beneficial in providing neuroprotection in retinal degenerative conditions. The aim of this study was to examine the neuroprotective effect of Müller glia derived EVs in human ESC-derived neuronal cells containing RGCs. Cells were isolated from 40–50-day-old retinal organoids and cytotoxicity was induced by addition of NMDA (1mM) for 24 h, followed by treatment with a population of Müller cell derived EVs for a further 24 h. Isolated RGC-enriched cultures expressed characteristic RGC markers such as βIII tubulin, Brn3b, RBPMS, γ-synuclein, Thy1 and NMDAR1. Exposure of this cell population to NMDA lead to a significant reduction in the average neurite length which then recovered with exposure to Müller cell-derived EVs. Investigation of kinase activity revealed increased apoptotic signalling via activation of P38 and p53 after NMDA addition to RGC-like cultures and pro-survival signalling by activation of RSK1/2/3 after addition of EV to the NMDA-damaged cells, suggesting EVs derived from Müller glia support the survival of the RGC-enriched cultures. It is hoped that these observations aid future investigations to assess new EV-related therapies to treat neuronal injury occurring in retinal degenerative conditions such as glaucoma.