Scientists have used gene therapy to reverse one of the most common causes of blindness.
A single gene injected into the back of the eye restores vision, by fixing a problem which stops the retina detecting light.
The breakthrough, in mice experiments, saw the animals’ blindness cured so that they again responded to beams of light and could see objects placed in their cage. Crucially, the eye continued to make a vital protein which restores sight for 15 months after the initial injection.
Researchers at the University of Oxford says the gene therapy goes further than other work on retinitis pigmentosa, which affects more than 20,000 people in Britain.
Single gene injected into the back of the eye found to restore vision in mice with retinitis pigmentosa (stock photo)
WHAT IS RETINITIS PIGMENTOSA
Retinitis Pigmentosa (RP) is the name given to a group of inherited eye conditions that affect the retina at the back of the eye.
RP causes permanent changes to your vision, but how much and how quickly varies from person-to-person.
Almost all types are inherited, caused by a fault in the genetic information passed down to you from a parent.
The faulty genes cause your retinal cells to stop working and eventually die. This affects your eye’s ability to process the light that enters it.
For most people with RP, the early symptoms include:
- Difficulty seeing in poor light such as outdoors at dusk or in a dimly lit room.
- Loss of peripheral vision – this can lead to ‘tunnel vision’
Previous attempts focused on correcting the genetic mutations which cause blindness by killing off the cells we need to detect light.
However the new technique provides a single fix, by drafting in completely different cells to do their job. It could be available for patients in five to 10 years.
Samantha de Silva, the study’s lead author from the Nuffield Laboratory of Opthalmology at the University of Oxford, 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.’
The rod cells in the eye allow us to see in dim light and provide peripheral vision, so that we can see to the side when staring straight ahead. The cone cells work best in bright light and help us read and recognise colours.
Eventually both are lost in retinitis pigmentosa, the inherited disease which is the most common cause of blindness in young people.
But another type of cell in the retina which is not normally light-sensitive can be drafted in to do the same job as the rod and cone cells, if encouraged to make a light-sensitive protein called melanopsin.
The scientists did this in mice which have a similar natural genetic fault to the one which causes retinitis pigmentosa in humans – who are also blind.
They injected a virus engineered to be harmless into the animals’ eyes, ‘infecting’ the cells with a gene which causes the retina to produce melanopsin.
Within just three weeks, the previously blind mice reacted to plastic objects placed in their cage, while their eyes responded when they were exposed to light. The changes in their behaviour made it clear they could see for the first time.
Potential treatment for humans
The results lasted into old age, although trials on humans are needed to ensure the results are permanent, and are hoped to go ahead within five years.
The new research is published in the journal Proceedings of the National Academy of Sciences.
Professor Alan Boyd, President of the Faculty of Pharmaceutical Medicine, said: ‘These results are very encouraging and could lead to a potential treatment for end-stage blindness in humans.’
It comes as scientists at the University of Iowa have used gene editing to fix a mutation involved in causing glaucoma. They were able to prevent eye damage in mice, as well as the build-up of pressure which leads to glaucoma, and say the results could translate to humans.