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Gene therapy partially restores sight in mice and dogs

15 December 2014

By Dr Rosie Gilchrist

Appeared in BioNews 784

Scientists have used gene therapy to restore some sight to animals with visual impairment similar to retinitis pigmentosa, a type of human blindness. The findings relate to restored light sensitivity, but may hold promise for restoring vision in the future.

Retinitis pigmentosa is a genetic disorder affecting approximately 1 in 4,000 people, in which retinal light-sensing cells degenerate, resulting in tunnel vision and eventually total sight loss.

Researchers at UC Berkeley, USA, performed experiments on mice with blindness caused by a genetic defect similar to retinitis pigmentosa. By inserting a gene followed by an injection of a chemical 'photoswitch', the authors of this study were able to genetically engineer nerve cells in mouse retinas at the back of the eye to become light-sensitive. Mice treated in this way were able to navigate a water maze like sighted mice.

The nerve cells targeted by the gene therapy, retinal ganglion cells, are not normally responsive to light, but are connected to the underlying nerves that relay visual information to the brain, and which remain functional in retinitis pigmentosa.

Following the success of experiments in mice, the researchers moved on to test the treatment in dogs with a genetic form of blindness.

'The dog has a retina very similar to ours, much more so than mice, so when you want to bring a visual therapy to the clinic, you want to first show that it works in a large animal model of the disease', said lead researcher Ehud Isacoff, professor of molecular and cell biology at UC Berkeley.

Early experiments showed that the treated dog retinas responded to light in a similar way to the mouse retinas, although no experiments were conducted to establish if the dogs could see again, explains NHS Choices.

'Use of such a clinically relevant large animal model allows us to begin tackling the next challenges on the road to translating this novel therapeutic strategy to human patients', said William Beltran, an author on the paper and associate professor of ophthalmology at the UPenn School of Veterinary Medicine.

If this therapy could be shown to work in people, it could help patients with forms of blindness where there is degeneration of light-sensitive cells but the underlying nerve cells remain intact, such as retinitis pigmentosa. However, patients with blindness due to other causes, such as age-related macular degeneration, would not be candidates for treatment.


16 October 2017 - by Rikita Patel 
The US Food Drug and Administration advisory committee has backed the use of gene therapy to treat a hereditary disease for the first time...
09 October 2017 - by Dr Kimberley Bryon-Dodd 
Gene therapy has restored some vision in mice blinded by retinitis pigmentosa, an inherited degenerative eye disease...
21 November 2016 - by Paul Waldron 
Scientists in the US have used a genome-editing technique to partially restore vision in blind rats...
03 May 2016 - by Sarah Gregory 
A trial of gene therapy for choroideremia, a rare form of inherited blindness, has partially restored the vision of several patients...
01 February 2016 - by Kulraj Singh Bhangra 
Researchers have used the CRISPR/Cas9 genome-editing technique to correct a genetic mutation that causes blindness...

06 October 2014 - by Dr Greg Ball 
A pool of stem cells found on the surface of the eye can be used to form light-sensitive cells that could one day treat blindness, researchers have reported...
07 July 2014 - by Dr Daniel Grimes 
In one of the first experiments to grow tissue from adult stem cells, scientists have grown corneas in the lab...
16 June 2014 - by Alice Plein 
In a research first, a section of light-sensing tissue, closely resembling the human retina, has been grown in the laboratory from human stem cells...
16 January 2014 - by Siobhan Chan 
Gene therapy for an eye condition called choroideremia is safe and has improved the vision of six patients, says a study in the Lancet...

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