Second Sight: Research Breakthrough Offers Hope To Millions With Retinitis Pigmentosa

EU-funded scientists have succeeded in awakening dormant vision cones, an achievement that may lead to saving millions of people from going blind. The dormant cones, which normally remain in the eye even after blindness has occurred, were successfully reactivated by an international team of scientists led by the Friedrich Miescher Institute in Switzerland and the Institut de la vision in France. The findings are published in the journal Science.

The study was funded in part by two EU projects: RETICIRC (‘Circuit specific approaches to retinal diseases’), financed with EUR 2.25 million under the Health Theme of the Seventh Framework Programme (FP7); and NEURAL CIRCUIT (‘Combining genetic, physiological and viral tracing methods to understand the structure and function of neural circuits’), supported as a Marie Curie Excellence Grant under the Sixth Framework Programme (FP6). 

More than 2 million people worldwide suffer from a diverse group of diseases referred to as retinitis pigmentosa. Retinitis pigmentosa is an inherited form of retinal degeneration, characterised by progressive sight loss eventually leading to blindness. 

The disease affects photoreceptors, cells that convert light into impulses. These impulses are processed by the retina and sent to the brain via nerve fibres. 

There are two types of photoreceptor: rods and cones. Rods allow us to see at night. As the disease advances, rods are the first to become affected, and eventually destroyed. Cones are responsible for colour and high-acuity daytime vision. They are the next to be impacted by the disease but, unlike rods, cones remain in the organism even when they cease to work. 

Even though they can no longer respond to luminous stimulation, cones still retain some electrical properties as well as links to some of the retina’s neurons that send visual information to the brain. Until now, it was unclear whether these cones were accessible for therapeutic intervention. 

Dr Botond Roska of the Friedrich Miescher Institute and his team of neurobiologists have pioneered a gene therapy using archaebacterial halorhodopsin, a light-sensitive protein that restores the functionality of the damaged cone cells. Their study showed that the existing cell network was able to reproduce many of the complicated functions that convert light into a neuronal signal. According to the team, the dormant cells represent an important gateway for therapeutic intervention in certain diseases where photoreceptor function is lost. 

‘We believe that with our gene therapeutic method we have found a powerful approach that could eventually help a subset of retinitis pigmentosa patients,’ said Dr Roska. He added that the team is currently screening patients to determine who might benefit the most from their new therapy.

Source: Cordis News Release
For more information, please visit: 
Friedrich Miescher Institute (FMI) 
Institut de la vision
Research publication: Busskamp, V., et al. (2010) Genetic reactivation of cone photoreceptors restores complex visual responses in Retinitis pigmentosa. Science (in press). Published online 24 June; DOI: 10.1126/science.1190897.