Project Summary To date, no therapy exists to restore vision to the over 64 million people worldwide who are legally blind from diseases that damage the optic nerve. Neuro-protective strategies aimed at preventing damaged retinal ganglion cells (RGCs) from degenerating and neuro-regenerative strategies aimed at promoting axon growth confer modest gains in vision after optic nerve crush injury when applied alone. Moreover, these approaches appear to be lacking in guidance cues as regenerating RGC axons have been reported to have circuitous projections, with 10-20% of axons exhibiting premature branching and 40% of axons having regenerated aberrantly, making u-turns and extending back towards the eye or growing into the opposite optic nerve. We have shown that exogenously applied electric fields (EFs) not only promote RGC axon growth but appear to also be able to control the direction of axon growth. This suggests that EFs may be exploited to not only “drive” axon growth but also “steer” axons to grow towards intended targets. Indeed, in vivo stimulation with asymmetric waveforms was found to be effective at directing full-length optic nerve regeneration, without evidence of aberrant targeting, and restoring partial visual function (local field potential recordings in the superior colliculus and pattern electroretinogram) after crush injury. Given this, we hypothesized that combining EF stimulation with other neuro-regenerative strategies would have synergistic effects on promoting optic nerve regeneration. More targeted regeneration could confer increased gains in visual function. Our multi-disciplinary consortium between neuro-ophthalmologists, developmental biologists, neuro-anatomists, neurosurgeons, electrophysiologists, and electrical engineers proposes to test the efficacy of combining neuro-protective and neuro- regenerative strategies with EF application to direct RGC axon regeneration and restore visual function to adult rats after optic nerve crush injury. Additionally, we will map and characterize the morphology and trajectory of regenerated axons in whole rat brains using 3D light sheet microscopy and SHIELD tissue clearing histology and assess whether EFs direct target specific regeneration.

Current neuro-protective and neuro-regenerative strategies to restore vision to the over 64 million people worldwide who are legally blind from diseases that damage the optic nerve are successful at promoting survival of damaged retinal ganglion cells (RGCs) and promoting long distance RGC axon regeneration but are lacking in cues to guide axons towards appropriate targets in the brain. We have shown that exogenously applied electric fields (EFs) not only promote RGC axon growth but appear to also be able to control the direction of axon growth. In this project, we propose to develop EF application into a technology that will synergize that with current strategies for optic nerve regeneration by providing directional cues for regenerating axons, leading to more targeted growth and increased recovery of visual function.