When it comes to the eyes, pharmaceuticals either alleviate systems, such as eye drops for dry eye, or they keep conditions from getting worse, such as eye drops which regulate pressure in the eye. Drops don’t improve vision. That is, until recently, when research at Children’s Hospital of Boston showed some promise.
Investigators were able to restore vision in mice with optic nerve injury by adding a channel blocking drug to help the nerves conduct impulses from the eye to the brain. Gene therapy was used to regenerate the optic nerve. Specifically, a gene therapy virus, known as AAV, was used to deliver the genetic materials that lead to regeneration. Previous methods of vision restoration in laboratory animals involved deleting or blocking tumor suppressor genes. This encourages regeneration but it can also lead to cancer. It is hoped that in the future, drugs alone can lead to restored vision.
The mice in this study were able to turn their heads to follow patterns of moving bars. (The technicians doing the testing didn’t know which mice received the treatment and which ones didn’t.) In addition, it was found that the mice didn’t just have functional vision. This drug cocktail improved their vision so that the mice could follow thinner and thinner bars.
What makes this research interesting was the focus on regenerating optic nerve fibers. The complicated procedures which were employed to accomplish this feat, however, are not without flaws: “We found that the regenerated axons are not myelinated and have very poor conduction — the travel speed is not high enough to support vision,” says co-senior investigator Zhigang He, PhD. “We needed some way to overcome this issue.”
That’s where a channel blocking drug comes in. The researchers discovered that a potassium channel blocker, known as 4-aminopyridine (4-AP) can help to strengthen nerve signals when the myelin sheath isn’t present. This drug is used for multiple sclerosis, which involves myelin loss. So, adding it helped the signals travel at faster, more desirable, speeds.
As great as 4-AP is, however, the side effects of this drug include seizures, so researchers are testing similar drugs to see if they can get the same results without the side effects. Investigators are working to get a better understanding of the extent of the mice’s visual recovery and whether drugs alone can convince the myelin to grow again.
The idea of restoring sight to the blind is something we can all raise our glasses to. So here’s to drug cocktails for vision!