New therapy holds promise for restoring vision

PUBLIC RELEASE DATE:

8-Dec-2014

Contact: Robert Sanders rlsanders@berkeley.edu 510-643-6998 University of California - Berkeley @UCBerkeleyNews

A new genetic therapy not only helped blind mice regain enough light sensitivity to distinguish flashing from non-flashing lights, but also restored light response to the retinas of dogs, setting the stage for future clinical trials of the therapy in humans.

The therapy employs a virus to insert a gene for a common ion channel into normally blind cells of the retina that survive after the light-responsive rod and cone photoreceptor cells die as a result of diseases such as retinitis pigmentosa. Photoswitches - chemicals that change shape when hit with light -are then attached to the ion channels to make them open in response to light, activating the retinal cells and restoring light sensitivity.

Afflicting people of all ages, retinitis pigmentosa causes a gradual loss of vision, akin to losing pixels in a digital camera. Sight is lost from the periphery to the center, usually leaving people with the inability to navigate their surroundings. Some 100,000 Americans suffer from this group of inherited retinal diseases.

In a paper appearing online this week in the early edition of the journal Proceedings of the National Academy of Sciences, University of California, Berkeley, scientists who invented the photoswitch therapy and veterinary colleagues at the School of Veterinary Medicine of the University of Pennsylvania (UPenn) report that blind mice regained the ability to navigate a water maze as well as normal mice.

The treatment worked equally well to restore light responses to the degenerated retinas of mice and dogs, indicating that it may be feasible to restore some light sensitivity in blind humans.

"The dog has a retina very similar to ours, much more so than mice, so when you want to bring a visual therapy to the clinic, you want to first show that it works in a large animal model of the disease," said lead researcher Ehud Isacoff, professor of molecular and cell biology at UC Berkeley. "We've now showed that we can deliver the photoswitch and restore light response to the blind retina in the dog as well as in the mouse, and that the treatment has the same sensitivity and speed of response. We can reanimate the dog retina."

Advantages over other gene therapies

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New therapy holds promise for restoring vision