Research in vision-challenged pooches might pave the way to helping humans battle similar problems, new research suggests.
A team at Michigan State University (MSU) believes insights into an inherited condition that affects humans and dogs in similar ways could help reverse vision loss in both species.
In 2010, research led by MSU veterinary ophthalmologist Dr Andras Komaromy showed that vision in dogs suffering from achromatopsia, an inherited form of total colour blindness, could be restored by replacing the gene associated with the condition. This treatment, however, was not effective for dogs older than one year..
Building on his earlier research, Komaromy theorised that certain photoreceptor cells in the eyes called "cones" - which process light and colour - were simply too worn out in older dogs. "Gene therapy only works if the nonfunctional cell that is primarily affected by the disease is not too degenerated," he said. "That's how we came up with the idea for this new study. How about if we selectively destroy the light-sensitive part of the cones and let it grow back before performing gene therapy? Then you'd have a younger, less degenerated cell that may be more responsive to therapy."
Affects are similar
The latest study involved dogs between one and three years old with achromatopsia. Before replacing the mutant gene, the researchers treated some of the dogs with a protein called CNTF that is used by the central nervous system to keep cells healthy. The dogs were given a dose high enough to partially destroy photoreceptors and enable new growth.
"We were just amazed at what we found," Komaromy said. "All seven dogs that got the combination treatment responded, regardless of age."
Although achromatopsia is a rare condition in humans, the study's authors pointed out that other disorders involving the photoreceptors affect humans and dogs in similar ways. They suggested that this combination treatment model also holds promise for people with these conditions, although it should be noted that success in animal research often does not translate to success in humans.
"Based on our results, we are proposing a new concept of retinal therapy," Komaromy said. "One treatment option alone might not be enough to reverse vision loss, but a combination therapy can maximise success."
The US National Institutes of Health provides more information on blindness and vision loss.