Restoring vision in night blindness: Mice point way to stem cell therapy

Impaired vision and blindness are leading causes of disability, affecting over 3 million people in the USA today, so it’s no surprise that biomedical scientists are working hard to develop therapies to improve and restore vision.  Over the past few years we have discussed several therapies that have been developed to treat different types of vision loss, including anti-angiogenic therapies to treat wet age related macular degeneration, a leading cause of severe, irreversible vision loss in the elderly,  and gene therapy to treat Leber congenital amaurosis, an inherited disease characterised by progressive degeneration of the retina. Speaking of Research committee member Dario Ringach has also written on the Opposing Views website on the very promising research now underway to develop electronic prosthesis to restore vision in blind people.

In another important development in this field Professor Robin Ali* and his team at the UCL Institute of Ophthalmology have announced the first demonstration that transplanted retinal rod cells can improve vision in mice with night-blindness, publishing the results of their study in the prestigious science journal Nature1. Rod cells are photoreceptor cells in the retina of the eye that function well in low light conditions, and an absence of rod cells leads to night blindness. Mutations in the gene GNAT1 cause congenital night blindness in humans, and mice in which the Gnat1 gene has been knocked out are night blind.  In the video below Professor Ali show that by transplanting rod cell precursors into the retina of Gnat1 knockout mice his team was able to restore vision – albeit  not fully.

It’s a fascinating piece of work, though as Professor Ali makes clear in comments to the Guardian newspaper last week there is still a lot of work to do before this can be evaluated in humans.

Now we’ve discovered we can restore vision, it gives us impetus to go on and make the process better”

As both the video and Guardian article indicate an important step will be identifying suitable sources of cells for transplantation, with both embryonic stem cells and induced pluripotent stem (iPS) cells under consideration.  This may not take as long as one might think, as we discussed last November a clinical trial was recently launched to assess the potential for transplantation of another retinal cell type, retinal epithelial cells derived from human embryonic stem cells , to improve vision in patients with  Stargart’s Macular Dystrophy, an inherited form of blindness.

The work of Professor Ali and his colleagues at UCL is moving us closer to an effective treatment – and perhaps it is not unrealistic to talk about a cure – for night blindness. Their work will also no doubt drive research on protoreceptor cell transplantation in other forms of blindness, such as dry age related macular degeneration – the most common cause of vision loss in people aged over 50 – which is characterised by loss of both rod and cone photoreceptor cells.

Paul Browne

*        Professor Ali also played a leading role in the development of gene therapy for Leber congenital amaurosis, and led the first clinical trial of this technique.

1)      Pearson RA, Barber AC, Rizzi M, Hippert C, Xue T, West EL, Duran Y, Smith AJ, Chuang JZ, Azam SA, Luhmann UF, Benucci A, Sung CH, Bainbridge JW, Carandini M, Yau KW, Sowden JC, Ali RR. “Restoration of vision after transplantation of photoreceptors.Nature. 2012 Apr 18. doi: 10.1038/nature10997.

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