By Adrian Galbreth
Thousands of people across the world begin to lose their sight when they reach middle age due to a condition called retinitis pigmentosa, which slowly robs people of their vision and severely impairs their way of life.
However, a new study carried out by experts at the University of Pennsylvania has suggested that they can prevent, or even reverse, a blinding retinal disease.
The study involved testing the treatment on dogs, as there are similarities between humans and dogs, in terms of both eye anatomy, physiology and disease characteristics.
Led by William Beltran, assistant professor of ophthalmology at Penn's School of Veterinary Medicine, the experts claim that the positive response to gene therapy raises hope for a clear path to human therapies.
Researchers working on the gene therapy approach took advantage of a viral vector to deliver the therapeutic RPGR gene specifically to diseased rods and cones, which normally malfunction and progressively die in the absence of treatment.
The research team had previously successfully applied a similar approach to two other heritable vision disorders that occur in both humans and dogs, including Leber congenital amaurosis and achromatopsia, though this study was more challenging, as it was necessary to target both main classes of photoreceptor cells.
Professor Beltran said this is the first proof that the condition is treatable in an animal model, as a single subretinal injection administered to the diseased dogs led to functional and structural recovery.
The dogs' recovery was assessed using a variety of methods that are used clinically in patients, such as electroretinography and optical coherence tomography, with scientists concluding that the results are promising and relevant for translation to the clinic.
"We are intervening to treat both classes of photoreceptor cells, rods and cones, and that has never been done before in a large animal model. And not only can we prevent the disease onset but also restore the remaining photoreceptors cells to normal once the disease is ongoing," the expert commented.
While there is much work to do to assess long-term efficiency and safety with this approach, the experts hope that the vector and knowledge could be used in a few years to treat the many patients losing vision from retinitis pigmentosa.
by Martin Burns