An experimental form of gene therapy to treat blindness has been showed to restore some vision in mice.
Researchers from the University of Manchester were able to generate a response to visual stimuli in mice with advanced retinal degeneration by enabling other cells in the eye to capture light.
They used a virus to insert a gene that produces the light-sensing pigment, rhodopsin, into the ganglion and bipolar cells in the eye, usually responsible for transmitting electronic signals from the rods and cones to the brain.
After treatment, the mice were reported to react when shown a video of an owl swooping. 'You could say they were trying to escape, but we don't know for sure', said Professor Rob Lucas of the University of Manchester and co-author of the study. 'What we can say is that they react to the owl in the same way as sighted mice, whereas the untreated mice didn't do anything.'
The mice were observed to see real objects again, although not so well as sighted mice. 'The treated mice could discriminate black and white bars, but only ones that were 10 times thicker than what sighted mice could see,' Professor Lucas said.
Previous studies have focused on replacing or repairing genes in rods and cones, but the new research attempts to allow other cells in the retina to capture light, compensating for lost light receptors, and could be used to treat certain types of blindness.
Lucas adds that the virus used is already approved for treatment in humans and hopes to start conducting clinical trials in humans in five years' time.
'This is the most effective example yet of the use of genetic therapy to treat advanced retinal degeneration,' Professor Robin Ali of University College London, told New Scientist. Professor Ali was involved in the gene therapy trial for Leber congenital amaurosis, an inherited condition, but was not involved in the new study.
The long-term effects of the treatment are unknown, however. Robert Lanza, chief scientific officer at Ocata Therapeutics, told New Scientist there is some evidence that improvements made in the vision of people with Leber congenital amaurosis treated with gene therapy between one and three years ago has begun to wane.