Researchers at the University of Pennsylvania recently published a study in Nature Genetics describing how they used genetic therapy to do something straight out of a science fiction story: they restored the sight of three blind dogs.
The dog suffered from a genetic condition similar to one that afflicts more than 10,000 Americans. Due to inbreeding, the dogs have a genetic defect that prevents Vitamin A from being transported to the retina. As a result the retina never develops properly and the dogs — and children who suffer a similar genetic condition — are born with very poor sight which only diminishes as they age.
To treat this condition, the researchers took cells from the retinas of the blind dogs. They then exposed the cells to a specially formulated virus which carried a correct copy of the defective gene. The treated retina cells were then injected back into the dogs.
The results were astounding. The dogs’ left eyes received injections in a part of the eye away from the retina and their vision did not change. The right eyes, however, received injections directly behind the retina. Vision in the right eyes appeared to be completely restored.
Researchers showed a video for the media which showed the animals navigating through a dimly lit, cluttered room and completely avoiding all obstacles within the field of vision of their right eye.
Ophthalmologist Albert Maguire, one of the researchers in the study, said, “We have to be careful not to fill people with false expectations or false hopes. But, that said, it’s hard not to get very excited about this, because it’s a very dramatic result. I mean, basically these dogs were blind and now they are not blind anymore.”
Scientists have been able to restore sight to blinded mice before, but only temporarily. This is the first such success in reversing genetic blindness in a large animal. Moreover, the restored sight lasted at least 9 months after the initial injections, though further observations and research will obviously be required to see if the treatment is permanent or will require additional injections.
If continued studies with dogs finds that the procedure appears safe, initial human clinical trials of a similar technique could begin in three or four years and have implications for a number of genetic vision-related diseases that affect as many 200,000 Americans.
Gene therapy restores dogs’ sight. The BBC, April 27, 2001.
Gene Treatment Restores Vision in Blind Dogs. Rick Weiss, Washington Post, April 28, 2001.
New gene gives some sight to 3 blind dogs. Faye Flam, Philadelphia Inquirer, April 28, 2001.
Gene therapy restores vision in dog. Malcolm Ritter, Associated Press, April 27, 2001.
Gene therapy used to restore sight to blind dogs. Will Dunham, Reuters, April 27, 2001.
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