Blindness cure step closer after scientists replace lost light-sensitive cells in back of the eye
22:34 GMT, 18 April 2012
A treatment that has helped mice see in the dark could one day restore sight to the blind.
British doctors used injections of healthy cells to repair the damaged eyes of rodents.
The results were dramatic, with small numbers of cells restoring vision up to half of normal levels.
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The normal mouse swims towards the light in the test at Moorfields Eye Hospital
The work is at an early stage but if successful hundreds of thousands of Britons could benefit, such as those with age-related macular degeneration – one of the most common forms of blindness.
University College London researchers took healthy rods – tiny structures in the back of the eye essential for seeing in dim light – from young mice and injected them into the eyes of adult mice whose rods didn’t work.
After four to six weeks, the new rods appeared to be working almost normally and had formed the connections needed to transmit information to the brain.
When the treated mice were put in a dimly-lit pool, they headed straight for the exit.
Untreated mice swam in circles, proving the treated ones could see the way out, the journal Nature reports.
Lead researcher Professor Robin Ali said: ‘Patients who have lost all vision tell me that what they’d really appreciate is a treatment that gives them the ability to see light, to be able to navigate to see the door.’
The British and American scientists say much more work is needed before the technique can be attempted on human patients. The first clinical trials might be five or 10 years away.
The mice who had a transplant of photo receptors were able to follow the light (above). The untreated mice swam in circles (below)
But the researchers wrote in the journal Nature: 'The results presented here demonstrate for the first time that transplanted rod-photoreceptor precursors can integrate into a dysfunctional adult retina, and, by directly connecting with the host retinal circuitry, truly improve vision.'
The undeveloped precursor cells used in the study were taken from week-old mice. Up to 32,000 of the cells were integrated into the retinas of recipient animals.
Tests showed that visual responses in the brains of the mice were enhanced after the procedure.
To see how the transplants affected
behaviour, mice were placed in a dimly lit Y-shaped water maze in which
one of two routes led to escape. This required swimming towards a visual
cue, a grating pattern.
treatment, four of nine night-blind mice completed the task in 70 per
cent of trials. Untreated mice, and those given “sham” treatments,
performed no better than by chance.
integration in animals that performed best tended to be clustered,
rather than spread widely across the retina. This suggested that besides
the number of cells, the closeness of the cells to one another might be
Professor Phil Luthert, director of the UCL Institute of Ophthalmology, said: 'This is a landmark paper and the techniques used here are part of a pretty big push in regenerative medicine.
'It was only a few years ago that we wouldn't have thought repairing adult systems in this way would be possible – it was assumed to be a bridge too far, but with retinas at least, it seems entirely feasible.
'It is still going to be another five or ten years at least before we think about doing anything with patients, though we are now making significant progress along the way.
'What is truly remarkable about this field is how well transplanted cells seem to be accepted by the retina where they move into the right place and effectively wire themselves up.
'The next challenges faced by scientists in this area concern how many cells can be got into the retina, how well they can be made to connect and then to see just how effectively they will work.
'We also do not know how long-term any effects will be, whilst we have good reason to believe that any procedures would be long-lasting, at this stage we are only speculating.'
The research offers new hope for patients with diseases such as the genetic disorder retinitis pigmentosa (RP). The disease destroys retinal cells, especially the rods, leading to progressive loss of vision.
Around 25,000 people in the UK are affected by the disorder.
David Head, chief executive at the retinitis pigmentosa charity RP Fighting Blindness, which part-funded the research, said: 'This is fantastic progress and exciting for patients faced with sight loss as a result of retinitis pigmentosa.
'To read that cells appeared to be functioning almost as well as normal rod-photoreceptor cells and had formed the connections needed to transmit visual information to the brain is truly amazing. This is a great step forward.'