New Approach Tried for Diabetic Blindness
Antibody Injections Block Abnormal Blood Vessel Formation
Jan. 10, 2005 -- It may be possible to prevent blindness caused by diabetes, say University of Florida researchers.
Their strategy - which involves injections of an antibody into the eye -- has worked on lab mice. If it also helps humans, it could help millions of people with diabetes avoid a complication called diabetic retinopathy.
Diabetic retinopathy can devastate the eye, and it's a common problem. The disease is the leading cause of vision loss in people aged 20-74. It's responsible for 12,000 to 24,000 new cases of blindness per year in the U.S.
Nearly 8 million diabetic Americans have some form of diabetic retinopathy. That's about half of all U.S. diabetes patients, say Edward Scott and colleagues from the university's stem cell biology and regenerative medicine program.
Diabetic retinopathy unfolds in two stages. First, high blood sugar and high blood pressure weaken tiny blood vessels in the eye. As a result, those vessels can bulge and burst, leaking into the eye's retina, the back lining of the eye where electrical impulses are converted to images that are sent to the brain.
Matters can worsen after that. The second, more serious stage is called proliferative retinopathy. It occurs when new blood vessels form on the retina. Those delicate, abnormal new vessels can break easily. The bleeding vessels can also cause scar tissue to form, burdening or even detaching the retina.
Diabetic retinopathy has no cure. Laser treatment can prevent further damage if performed before the retina is ravaged. The researchers also say there are negative side effects from using steroids to decrease swelling seen in some cases of retinopathy that don't respond to laser treatment.
Seeking a New Solution
The researchers took samples from the eyes of 46 people with diabetes, 24 of whom had retinopathy. That revealed an important clue. All the samples contained a protein, SDF-1. The worst cases of retinopathy had the highest concentrations of SDF-1.
SDF-1 is no stranger to scientists. It works all over the body, serving as a traffic cop for new blood cells. "SDF-1 is the main thing that tells blood stem cells where to go," says Scott in a news release.
That can be a problem in the eye, where SDF-1 doesn't break down. "It continues to call the new blood vessels to come that way, causing all the problems," explains Scott.
The researchers counteracted SDF-1 in mice. First, they used lasers to give the mice a condition like diabetic retinopathy. Next, they injected an SDF-1 antibody into the mice's eyes. The antibody disables the action of SDF-1 in the eye.
No Blind Mice
None of the injected mice went blind. They didn't produce the abnormal new blood vessels.
"This suggests that easily achievable SDF-1 antibody concentrations may provide effective preventative treatment for diseases such as proliferative retinopathy," write the researchers in The Journal of Clinical Investigation's January edition.
The next step is testing the method on monkeys. If that goes well, human tests will follow.
The scientists are still seeking a way to anchor the antibody without letting it get into the retina, says a news release. If they figure that out, patients could get routine eye injections. Meanwhile, Scott has co-founded a company that plans to market stem-cell based therapies.