In a normal eye, opsins are expressed by the rod and cone photoreceptors in the retina. When activated by light, the photoreceptors pulse and send a signal through other retinal neurons, the optic nerve, and on to neurons in the brain.
A variety of common eye diseases, including age-related macular degeneration and retinitis pigmentosa, damage the photoreceptors, impairing vision. But while the photoreceptors may no longer fully function, other retinal neurons (bipolar cells) remain intact. The team identified a way for bipolar cells to take on some of the work of damaged photoreceptors.
“The beauty of our strategy is its simplicity,” said Samarendra Mohanty, PhD, Nanoscope founder and corresponding author of a report on the mouse study that appears today in Nature Gene Therapy. “Bipolar cells are downstream from the photoreceptors, so when the MCO1 opsin gene is added to bipolar cells in a retina with nonfunctioning photoreceptors, light sensitivity is restored.”
The strategy could overcome challenges plagued by other approaches to retinal regeneration, according to the researchers. Gene replacement therapy has thus far worked principally in rare diseases that leave photoreceptors intact.
Under a best-case scenario, the therapy could help patients achieve 20/60 vision, according to the researchers; however, no one knows how the restored vision will compare to normal vision.