Blind Mice No More: Researchers Restore Sight To Mice Using Stem Cells

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Stem cell research could soon restore sight to the blind.

In a study published in Nature Biotechnology, a team of scientists at the University College London's Institute of Ophthalmology and Moorfield's Eye Hospital has successfully restored vision in mice with impaired photoreceptors, the light-sensitive retinal "rods" and "cones" that enable us to see.

The Guardian reports that senior author Dr. Robin Ali and his colleagues were able to integrate into the retinae of mice artificial photoreceptors grown in a laboratory from embryonic stem cells — a breakthrough that built on earlier research, where the team showed that immature rods obtained from young mice could be implanted into adult mice to restore their sight.

An artificial growth medium eliminates the need for a donor, thus providing the framework for a viable treatment method for humans suffering from similar impairments. Today, the loss of photoreceptors is the cause of blindness in a wide variety of conditions, including age-related macular degeneration, diabetes-related blindness, and retinitis pigmentosa.

While the researchers were successful in establishing nerve connections between the artificial photoreceptors and the subject's brain, it will take at least five years before the team can begin running human trials.

"Now that we have proved the proof-of-concept, the road is clear to the first set of clinical trials just to see whether it'll work," Ali told reporters. "It certainly isn't a case of rolling out treatments in five years' time and providing therapies. It's taken us 10 years to get here and it'll take us five years to get started in people."

Over the past decade, Ali and his colleagues have slowly but steadily progressed to the transplant success rate displayed in the study. Since 2006, it has risen from 0.5 percent to about 20 percent; for every 200,000 transplanted cells, 40,000 are now integrated into the subject's retina.

"If we can transplant 20,000 cones in [a person with] macular degeneration, I think there's potential for tremendous clinical benefit because humans don't need very many functioning cones for a really useful function," said Ali. "The foveola, in the centre of the fovea [in the retina], which is responsible for really high visual acuity — things like reading — has only 20,000 cones. That gives you an idea just how few cells you might need."

While some express concern that the mouse model is not an adequate approximation of the human retina's complexity, few are denying the significance of the new method.

"Restoring the sight for the 'three blind mice' may be far easier than for the 'farmer's wife,'" quipped Professor Chris Mason, a stem cell biologist at University College London.

"Before human clinical trials can commence, the mouse model will require significant optimization, for example increasing the efficiency of new photoreceptors to connect with the damaged retina. However, there is no doubt that this breakthrough, either directly as the basis of a future cell therapy, or indirectly by expanding our knowledge, will significantly contribute to the fight against blindness," he said.

Source: Anai Gonzalez-Cordero, Emma L West, Rachael A Pearson, Yanai Duran, Livia S Carvalho,Colin J Chu, Arifa Naeem, Samuel J I Blackford, Anastasios Georgiadis, Jorn Lakowski, Mike Hubank, Alexander J Smith, James W B Bainbridge, Jane C Sowden & Robin R Ali. Photoreceptor precursors derived from three-dimensional embryonic stem cell cultures integrate and mature within adult degenerate retina. in Nature Biotechnology. 2013.

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