Dog Vision: Gene Therapy For X-Linked Retinitis Pigmentosa

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Gene expression pattern of the RPGR gene: Image by AndrewGNF

Dog Vision Treatment: Treating XLRP With Viral Vector Gene Therapy

One of the important aspects of the trial conducted at the University of Pennsylvania’s School of Veterinary Medicine was that both types of photoreceptor cells in the retina were treated, while in previous work, only rods or cones were targeted, but not both.  In order to restore vision, the researchers used a single subretinal injection of healthy Retinitis Pigmentosa GTPase Regulator (RPGR) gene, which is generally the damaged one in XLRP.

To ensure that the RPGR was delivered to the diseased rods and cones, a viral vector which targets rods and cones and not other cells was used. In addition, a bit of genetic code, or “promotor,” was attached to the healthy RPGR gene ensuring the gene would only activate if the virus entered the appropriate cells.

The Future of Retinal Disease Treatment in Both Dogs and Humans

If the results of this trial can be repeated, it will mean that it is possible to prevent the development of XLRP in dogs and people with the genetic mutation. What is even more exciting is that the treatment appears to restore damaged rods and cones in cases where the disease has progressed. Drs. Beltran and Aguirre were also able to show that the treatment repaired connections to other neurons which send signals from the retina to the brain, which makes it promising for other types of RP where changes in the retinal neurons are a factor.

It is important to remember, however, that this is a preliminary study, using a small number of animals. Longer term clinical trials will be needed to ensure the treatment is safe and effective under a variety of circumstances. Decoded Science spoke to Dr. Diederik Lagerwerff, owner of The Animal Doctors veterinary clinic, to discuss this research. According to Dr. Lagerwerff,  ophthalmologists to whom he refers patients suggest that access to this and similar gene therapy-based treatments is, at a minimum, ten years down the road. In the meantime, dog breeders can use the information gained about how the disease is genetically transmitted to reduce the number of dogs born with RP and other genetically linked retinal disease.

Sources:

Beltran, W.A. et al. 2012. Gene therapy rescues photoreceptor blindness in dogs and paves the way for treating human X-linked retinitis pigmentosa. (2012). doi: 10.1073/pnas.1118847109 PNAS. Accessed May 11, 2012.

AKC Canine Health Foundation. Progressive Retinal Atrophy. Accessed online 1.23.2012

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