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
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.