GLAUCOMA PATIENT PLURIPOTENT STEM CELL-DERIVED ASTROCYTES CONTRIBUTE TO RETINAL GANGLION CELL NEURODEGENERATION

Abstract

Purpose : Retinal ganglion cell (RGC) degeneration is a primary characteristic of glaucoma, although non-cell autonomous mechanisms have been implicated in RGC dysfunction. Astrocytes associate with RGCs in the nerve fiber layer of the retina and optic nerve, where they can contribute to RGC neurodegeneration. However, the mechanisms by which astrocytes promote neurotoxicity and contribute to glaucoma remain unknown.

Methods : Human pluripotent stem cells (hPSCs) can serve as powerful tools for the in vitro study of neurodegenerative diseases, including neuron-glia interactions. Using hPSC-derived cells from a glaucoma patient with an Optineurin (OPTN) E50K mutation (linked to inherited forms of glaucoma) as well as isogenic control cells obtained by CRISPR/Cas9 gene editing, we explored how the OPTN(E50K) mutation affects RGC-astrocyte interactions leading to neurodegeneration.

Results : hPSC-derived OPTN(E50K) astrocytes exhibited a hypertrophic shape and increased branching, as well as autophagy dysfunction and altered mitochondrial dynamics. Transcriptional analysis showed upregulation of the inflammatory pathway and downregulated axonal guidance in OPTN(E50K) astrocytes, suggesting they confer neurotoxicity and/or a lack of neurosupportive roles. Therefore, the contribution of astrocytes to RGC neurodegeneration was determined through co-cultures. Importantly, compared to the effect promoted by isogenic control astrocytes, OPTN(E50K)-astrocytes induced degenerative phenotypes in RGCs, including decreased neurite length and complexity, together with increased excitability, in both OPTN(E50K) and isogenic control RGCs. Conversely, isogenic control astrocytes were capable of rescuing degenerative phenotypes observed in OPTN(E50K) RGCs. Glaucomatous astrocytes secrete reduced levels of certain growth factors, suggesting a deficit in their neurosupportive role. In accordance, the incubation of OPTN(E50K) RGCs with these factors increased neurite branching and synaptic protein expression, highlighting the role of astrocyte-derived factors in RGC support.

Conclusions : These results are the first of its kind to identify a neurotoxic phenotype in hPSC-derived astrocytes from a glaucomatous source, as well as to identify a role for astrocytes in the neurodegenerative process through non-cell autonomous mechanisms, highlighting these glial cells as novel potential therapeutic targets in glaucoma.

This is a 2021 ARVO Annual Meeting abstract.