May 6 - Transplanting light-sensitive photoreceptors into the eyes of visually impaired mice has helped them see again in groundbreaking experiments conducted by British scientists. The researchers hope that a similar procedure can be applied to humans to restore sight to those with degenerative eye diseases. Jim Drury reports.
It looks like a private rodent cinema......in fact it's a machine to test a mouse's eyesight. Visually impaired mice are being monitored here after receiving groundbreaking cell transplantation treatment which scientists hope will eventually cure degenerative eye diseases in humans. For the first time light-sensitive photoreceptors have been successfully transplanted into mice's eyes... allowing them to see. Robin Ali, Professor of Molecular Genetics at University College London, heads the team behind the research. SOUNDBITE (English) ROBIN ALI, PROFESSOR OF MOLECULAR GENETICS AT UNIVERSITY COLLEGE LONDON (UCL), SAYING: "We've previously shown that we could transplant photoreceptor cells and they would integrate within the retina, and now we're able to show that these integrated photoreceptor cells make functional connections, not only within the retina, but that they make appropriate connections to the visual centres in the brain and as a result of this we can improve vision." Photoreceptors consist of rods and cones. The rods are particularly sensitive to low-light, so healthy rod cells of young mice were injected into the retinas of older mice whose rods had degenerated, causing a condition called 'night blindness'. Loss of photoreceptors is central to human eye diseases like age-related macular degeneration, retinitis pigmentosa and diabetes-related blindness. But for the mice, it took just weeks before the transplanted cells functioned almost as well as normal rod-photoreceptor cells, forming the connections needed to transmit visual information to the brain. In a comparative test, run by Ali's colleague Dr Racheal Pearson, mice whose rods had been disabled were challenged to escape from a dimly lit maze. SOUNDBITE (English) DR RACHEAL PEARSON, ROYAL SOCIETY UNIVERSITY RESEARCH FELLOW AT THE INSTITUTE OF OPHTHALMOLOGY, SAYING: "Those mice are unable to complete the task, so they just swim around in the water and they use physical cues, like the sides of the water maze to actually swim around and eventually find the escape from the water by chance." The team now plan similar experiments with cone cells, which function best in bright light and are responsible for colour vision. They say the research could be useful in other forms of cell transplantation. SOUNDBITE (English) ROBIN ALI, PROFESSOR OF MOLECULAR GENETICS AT UNIVERSITY COLLEGE LONDON (UCL), SAYING: "What we've shown is that we can transplant nerves and have them make appropriate connections and that may have some far-reaching implications, that it might be possible eventually, it's going to be much more complicated, but it might be possible to transplant other types of nerves and perhaps repair other parts of the brain." Ali says human clinical trials are probably five years away but he believes that for millions of visually-impaired people across the globe, relief is in sight. Jim Drury, Reuters