Gene therapy restores vision in blind mice

Gene therapy has restored some vision in mice blinded by retinitis pigmentosa, an inherited degenerative eye disease.

Retinitis pigmentosa is the most common cause of blindness in young people, and no effective treatments currently exist for patients with little sight left.

'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,' said Dr Samantha de Silva at the University of Oxford, the lead author of the study.

Diseases like retinitis pigmentosa cause gradual loss of light-sensitive cells in the eye's retina, eventually leading to blindness. Rather than trying to restore these cells, researchers used a viral vector to introduce a gene for melanopsin, a light-sensitive protein naturally found in the eye, into the remaining retinal cells.

The cells then produced melanopsin and became able to sense and respond to light, and send visual signals to the brain. The changes lasted longer than a year, around the lifetime of the mice used in the study.

'Our next step will be to start a clinical trial to assess this in patients,' said Dr de Silva.

The authors are hopeful that this common form of blindness may be able to at least be partially restored in the future by using this gene therapy technique.

'The effect of retinitis pigmentosa on families with the disease is devastating and we have spent many years working out new ways to slow the loss of sight and to begin restoring it,' said Professor Robert MacLaren also at the University of Oxford, whose group led the research. 'This new approach is exciting because by using a human protein that is already present in the eye we reduce the chances of causing an immune response.'

Professor Alan Boyd, President of the Faculty of Pharmaceutical Medicine of the Royal College of Physicians, who was not involved in the study, said that no satisfactory treatments currently exist for patients with end-stage retinal degeneration, who have little sight left. Although human clinical trials could be a minimum of two to three years away, he said: 'These results are very encouraging and could lead to a potential treatment for end-stage blindness in humans.'

The study was published in the journal PNAS.