Visual activity helps regenerate optic nerves
Combination approach observed to partially restore sight in mice with optic nerve damage
A number of optic neuropathies, including relatively common conditions such as glaucoma, can lead to vision loss when they destroy or damage retinal ganglion cell axons. In adults, these axons are unable to regrow, meaning such vision loss is usually permanent.
In a study funded by the US National Institutes of Health, researchers examined stimulation strategies to improve optic nerve fiber regrowth. Optic nerve damage was induced in mice through the crushing of one optic nerve behind the eyeball. Mice were then exposed to high-contrast images for several hours a day over a three week period. Exposed mice were observed to have significant axonal regrowth versus control animals that had not received visual stimulation.
Prior research has demonstrated that increasing mTOR activity can promote optic nerve regeneration, thus it was decided to examine the potential for synergistic effects when combined with visual stimulation. Gene therapy was used to induce mTOR overexpression in mice retinal ganglion cells. Two weeks later, nerve crush was performed as before. Following three weeks of visual stimulation, more extensive regeneration was observed versus the population exposed to visual stimulation alone. Axon regrowth was observed through the optic nerve as far as the optic chiasm, about 6mm from the eye. Results were further improved when mice were forced to use only the injured eye during visual stimulation.
Assessing four types of visual perception, visual function was deemed to have been partially restored in animals receiving combination visual and mTOR a therapy. This performance was significantly improved when compared with untreated mice.
“This study’s striking finding that activity promotes nerve regrowth holds great promise for therapies aimed at degenerative retinal diseases,” explained National Eye Institute Program Director Thomas Greenwell. The investigators are now examining the effects of visual stimulation in a mouse model of glaucoma and looking to further examine the specific qualities of visual stimulation capable of driving regeneration.
Written by Hannah Wilson