British scientists have successfully restored the sight of blind mice, bringing us a step closer to new treatment for patients with degenerative eye disease.
Scientists are developing a treatment for macular degeneration, or age related blindness
There are two types of photoreceptor cells in the eyes- rods and cones. In mice and humans more than 95% are rods. These work well in the dark and are good at spotting movement, but see the world in black and white. Cones are far less numerous, but give a sharp, colour view of the world in good lighting conditions.
Scientists at University College London Institute of Opthalmology injected immature rod-photoreceptor cells from healthy young mice directly into the retinas of adult mice that had night blindness.
Each jab delivered around 200,000 rod photoreceptor cells, of which 20,000 to 30,000 attached to the animals' retinas and made working neural connections. The scientists used only rods in the latest experiments, as they are easier to transplant.
After four to six weeks, researchers tested the vision of the treated mice in a dimly lit water maze. Writing in the journal Nature, they found that the mice with transplanted rod cells were able to see a visual cue to find a hidden platform to enable them to get out of the water. The untreated mice found the platform only by chance.
Professor Robin Ali, at UCL Institute of Ophthalmology and Moorfields Eye Hospital, who led the research, said: "We've shown for the first time that transplanted photoreceptor cells can integrate successfully with the existing retinal circuitry and truly improve vision.”
Loss of photoreceptor cells is the cause of blindness in many human eye diseases, including age-related macular degeneration (AMD). Macular degeneration is a painless eye condition that leads to the gradual loss of central vision, and is the most common cause of blindness, which affects up to 15% of people over 75.
Although the results of this study are promising, there is still a way to go before this treatment might be suitable for humans.
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