Oxford University researchers who have transplanted cells capable of reforming the light-sensitive part of the retina in the eyes of blind mice believe the approach has relevance for treating patients with retinitis pigmentosa.The project, part funded by Oxford Stem Cell Institute and the Oxford Martin School, used mice that were blind due to complete loss of the light-sensing photoreceptor cells in their retinas. After two weeks the transplanted cells had reformed a full light-detecting layer on the retina and the mice could see, with 10 of the 12 showing improved pupil constriction in response to light.The study, published in PNAS, was led by Professor Robert MacLaren in the Nuffield Department of Clinical Neurosciences, with Dr Mandeep Singh an eye surgeon and PhD student. Dr Singh said: 'We found that if enough cells are transplanted together, they not only become light sensing but the also regenerate the connections required for meaningful vision.'Professor MacLaren added: 'Stem cells have been trialled in patients to replace the pigmented lining of the retina, but this new research shows that the light-sensing layer might also be replaced in a similar way. The light-sensing cells have a highly complex structure and we observed that they can resume function as a layer and restore connections after transplantation into the completely blind retina.'