London:
Coming soon is a single shot that may keep blindness at bay. Yes, sight-saving drugs could one day be given without repeated injections into the eye, by temporarily breaching the blood-retina barrier, say scientists.
At present, drugs to treat age-related muscular degeneration, the leading cause of blindness, are injected in to the eyeball once a month. They cannot be injected into the blood partly because an eye lining normally prevents molecules in the blood from reaching the retina.
Now, a team led by Trinity College Dublin has restored the vision of mice by temporarily weakening this lining to let drug molecules injected into the blood slip through, the 'New Scientist' reported.
The scientists used a technique, RNA interference, to block the production of claudin-5, a protein that makes the blood-retina barrier impermeable. "It's proof of principle," lead scientist Matthew Campbell said.
In fact, RNAi therapy is not yet safe enough for use in people, however, as it would breach the blood-brain barrier as well as the blood-retina barrier.
The scientists are already working on a way to block claudin-5 production in the eye only. The method involves gene therapy using a modified virus that makes the RNA only in the presence of an antibiotic called doxycycline.
With this approach, patients would need only one initial injection into their eye to deliver the virus. Then once a month they would take the antibiotic orally, and two days later the drug to treat blindness would be injected in their blood, the scientists said.
By then the blood-retina barrier would be sufficiently weakened to allow the drug to pass through. Although the existing drugs to treat age-related mascular degeneration would be too big to pass through the barrier, there are other molecules in development that are small enough.
"Some of these could be taken orally when the barrier goes down. The approach might also be useful for getting certain drugs past the blood-brain barrier," Campbell said. The findings are published in the 'Proceedings of the National Academy of Sciences' journal.
At present, drugs to treat age-related muscular degeneration, the leading cause of blindness, are injected in to the eyeball once a month. They cannot be injected into the blood partly because an eye lining normally prevents molecules in the blood from reaching the retina.
Now, a team led by Trinity College Dublin has restored the vision of mice by temporarily weakening this lining to let drug molecules injected into the blood slip through, the 'New Scientist' reported.
The scientists used a technique, RNA interference, to block the production of claudin-5, a protein that makes the blood-retina barrier impermeable. "It's proof of principle," lead scientist Matthew Campbell said.
In fact, RNAi therapy is not yet safe enough for use in people, however, as it would breach the blood-brain barrier as well as the blood-retina barrier.
The scientists are already working on a way to block claudin-5 production in the eye only. The method involves gene therapy using a modified virus that makes the RNA only in the presence of an antibiotic called doxycycline.
With this approach, patients would need only one initial injection into their eye to deliver the virus. Then once a month they would take the antibiotic orally, and two days later the drug to treat blindness would be injected in their blood, the scientists said.
By then the blood-retina barrier would be sufficiently weakened to allow the drug to pass through. Although the existing drugs to treat age-related mascular degeneration would be too big to pass through the barrier, there are other molecules in development that are small enough.
"Some of these could be taken orally when the barrier goes down. The approach might also be useful for getting certain drugs past the blood-brain barrier," Campbell said. The findings are published in the 'Proceedings of the National Academy of Sciences' journal.
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