A report in the journal Proceedings of the National Academy of Sciences (PNAS) titled “Long-term restoration of visual function in end-stage retinal degeneration using subretinal human melanopsin gene therapy” says that Scientists have cured blindness in mice with ‘simple’ genetic procedure that could work on humans. The most common form of blindness in young people could be at least partially cured using gene therapy, the new study in mice suggests.
The report said the results of the mice trials “suggest that this approach may be clinically useful in vision restoration in patients with end-stage” retinitis pigmentosa. “We demonstrate … restoration of visual function, indicating that this therapy could be stable and efficacious in the treatment of patients with end-stage retinal degenerations,” it added.
Researchers managed to restore sight to mice affected by retinitis pigmentosa after reprogramming their remaining retinal nerve cells. These were not light-sensitive but were altered by the technique to give the mice a degree of vision.
Most causes of untreatable blindness occur due to loss of the millions of light sensitive photoreceptor cells that line the retina, similar to the pixels in a digital camera. The remaining retinal nerve cells which are not light sensitive however remain in the eye. Samantha de Silva and colleagues (University of Oxford) used a viral vector to express a light sensitive protein, melanopsin, in the residual retinal cells in mice which were blind from retinitis pigmentosa, the most common cause of blindness in young people.
The mice were monitored for over a year and they maintained vision during this time, being able to recognise objects in their environment which indicated a high level of visual perception. The cells expressing melanopsin were able to respond to light and send visual signals to the brain. The Oxford team has also been trialling an electronic retina successfully in blind patients, but the genetic approach may have advantages in being simpler to administer.
The research was led by Professors Robert MacLaren and Mark Hankins at the Nuffield Laboratory of Ophthalmology in Oxford. Samantha de Silva, the lead author of the study said: “There are many blind patients in our clinics and the ability to give them some sight back with a relatively simple genetic procedure is very exciting. Our next step will be to start a clinical trial to assess this in patients.”
One of the researchers in the retinitis pigmentosa study, Dr Samantha de Silva, of Oxford University, expressed optimism about the implications of their work.
“There are many blind patients in our clinics and the ability to give them some sight back with a relatively simple genetic procedure is very exciting,” she said.
“Our next step will be to start a clinical trial to assess this in patients.”
Retinitis Pigmentosa (RP) is a genetic disease that results in significant vision impairment due to loss of photoreceptors in our retina. Photoreceptors are cells that are able to transmit visual information to our brain. There are two main classes of photoreceptors – cones which are used in color vision and bright light while rods are for dim light conditions. In terms of location, the cones are located in the central part of the retina while the rods are in the periphery.
During the RP disease process, damage to rod cells cause a loss in peripheral and low light vision. However, the debilitating effects of RP occur during the later stages when cones deteriorate and patients have difficulties in activities like facial recognition, reading, driving and mobility.
A separate study, also in mice, found gene editing could be used to stop the progress of glaucoma and the scientists said the same technique might work in humans.