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BACKGROUNDRetinal organoids serve as excellent human-specific disease models for conditions affecting otherwise inaccessible retinal tissue from patients. They permit the isolation of key cell types affected in various eye diseases including retinal ganglion cells (RGCs) and Müller glia.AIMTo refine human-induced pluripotent stem cells (hiPSCs) differentiated into three-dimensional (3D) retinal organoids to generate sufficient numbers of RGCs and Müller glia progenitors for downstream analyses.METHODSIn this study we described, evaluated, and refined methods with which to generate Müller glia and RGC progenitors, isolated them via magnetic-activated cell sorting, and assessed their lineage stability after prolonged 2D culture. Putative progenitor populations were characterized via quantitative PCR and immunocytochemistry, and the ultrastructural composition of retinal organoid cells was investigated.RESULTSOur study confirms the feasibility of generating marker-characterized Müller glia and RGC progenitors within retinal organoids. Such retinal organoids can be dissociated and the Müller glia and RGC progenitor-like cells isolated via magnetic-activated cell sorting and propagated as monolayers.CONCLUSIONEnrichment of Müller glia and RGC progenitors from retinal organoids is a feasible method with which to study cell type-specific disease phenotypes and to potentially generate specific retinal populations for cell replacement therapies.

Increasing evidence indicates that changes in the redox system may contribute to the pathogenesis of multiple optic neuropathies. Optic neuropathies are characterized by the neurodegeneration of the inner-most retinal neurons, the retinal ganglion cells (RGCs), and their axons, which form the optic nerve. Often, optic neuropathies are asymptomatic until advanced stages, when visual impairment or blindness is unavoidable despite existing treatments. In this review, we describe systemic and, whenever possible, ocular redox dysregulations observed in patients with glaucoma, ischemic optic neuropathy, optic neuritis, hereditary optic neuropathies (i.e., Leber’s hereditary optic neuropathy and autosomal dominant optic atrophy), nutritional and toxic optic neuropathies, and optic disc drusen. We discuss aspects related to anti/oxidative stress biomarkers that need further investigation and features related to study design that should be optimized to generate more valuable and comparable results. Understanding the role of oxidative stress in optic neuropathies can serve to develop therapeutic strategies directed at the redox system to arrest the neurodegenerative processes in the retina and RGCs and ultimately prevent vision loss.

The main risk factor for primary open-angle glaucoma (POAG) is increased intraocular pressure (IOP). It is of interest that about half of the patients have an IOP within the normal range (normal-tension glaucoma, NTG). Additionally, there is a group of patients with a high IOP but no glaucomatous neurodegeneration (ocular hypertension, OHT). Therefore, risk factors other than IOP are involved in the pathogenesis of glaucoma. Since the retina has a very high oxygen-demand, decreased autoregulation and a fluctuating oxygen supply to the retina have been linked to glaucomatous neurodegeneration. To assess the significance of these mechanisms, we have utilized a human experimental model, in which we stress participants with a fluctuating oxygen supply. Levels of oxidative stress molecules, antioxidants, and lipid mediators were measured in the plasma. Patients with NTG, OHT, and control subjects were found to have similar levels of oxidative stress markers. In contrast, patients with OHT had a higher level of total antioxidant capacity (TAC) and pro-homeostatic lipid mediators. Thus, we suggest that OHT patients manage fluctuating oxygen levels more efficiently and, thus, are less susceptible to glaucomatous neurodegenerations, due to enhanced systemic antioxidant protection.