Blind mice can see again, after Oxford University researchers transplanted developing cells into their eyes and found they could re-form the entire light-sensitive layer of the retina. Videos show the nocturnal mice, which once didn’t notice the difference between light and dark at all, now run from the light and prefer to be in the dark — just like mice with normal vision. The researchers say the approach has relevance for treating patients with retinitis pigmentosa, a condition in which the light-sensing cells in the retina gradually die leading to progressive blindness.
The study was led by Professor Robert MacLaren in the Nuffield Department of Clinical Neurosciences at the University of Oxford, together with Dr Mandeep Singh, an eye surgeon from the National University Hospital of Singapore who is currently undertaking PhD studies in Oxford. The findings are published online in the Proceedings of the National Academy of Sciences.
Other studies that have tried to regenerate a retina have relied on having a pre-existing outer layer of photoreceptor cells in place at the time of treatment. This study is different because it shows it is possible to regenerate a retina even when that outer layer is lost, say the researchers. “We have recreated the whole structure, basically it’s the first proof that you can take a completely blind mouse, put the cells in and reconstruct the entire light-sensitive layer” said McLaren, who compared it to regenerating a whole computer screen rather than repairing individual pixels. “We found that if enough cells are transplanted together, they not only become light sensing but they also regenerate the connections required for meaningful vision,” says Dr Mandeep Singh
The researchers worked with mice that were blind due to complete loss of the light-sensing photoreceptor cells in their retinas. The researchers injected the mice with “precursor” cells, and then they were observed over time to see if vision was restored. This was tested by observing if their pupils constricted when faced with light, if they fled bright areas, and if brain activity was noted when light was shone on their eyes. It took just two weeks for the transplanted cells to reform a full light-detecting layer on the retina and allow the mice to see.
Pete Coffee, a professor of opthalmology at University College London, says in a BBC News report that the study tackles what you would probably “need to do to restore sight in a patient that has lost their vision”. But he says more needs to be done to determine the quality of the restored vision – for instance, can the treated mice see the difference between food and predators
MacLaren was nonetheless enthusiastic about the potential for the findings to translate into benefits for humans as well as mice. He said: ‘The ability to reconstruct the entire light sensitive layer of the retina using cell transplantation is the ultimate goal of the stem cell treatments for blindness we are all working towards.”