Newly developed chemical restores light perception to blind mice

Progressive degeneration of photoreceptors—the rods and cones of the eyes—causes blinding diseases such as retinitis pigmentosa and age-related macular degeneration. While there are currently no available treatments to reverse this degeneration, a newly developed compound allows other cells in the eye to act like photoreceptors. As described in a study appearing in the February 19 issue of the Cell Press journal Neuron, the compound may be a potential drug candidate for treating patients suffering from degenerative retinal disorders.

The retina has three layers of , but only the outer layer contains the rod and that respond to light, enabling us to see the world. When the rods and cones die during the course of degenerative blinding diseases, the rest of the retina remains intact but unable to respond to light. Even though the innermost layer's nerve cells, called ganglion cells, remain connected to the brain, they no longer transmit information useful for vision.

Dr. Richard Kramer of the University of California, Berkeley and his colleagues have invented "photoswitch" chemicals that confer light sensitivity on these normally light-insensitive ganglion cells, restoring light perception in blind mice. An earlier photoswitch required very bright ultraviolet light, making it unsuitable for medical use. However, a new chemical, named DENAQ, responds to ordinary daylight. Just one injection of DENAQ into the eye confers light sensitivity for several days.

Experiments on mice with functional, nonfunctional, or degenerated rods and cones showed that DENAQ only impacts if the rods and cones have already died. It appears that degeneration in the outer retina leads to changes in the electrophysiology in the inner retina that enables DENAQ photosensitization, while the presence of intact photoreceptors prevents DENAQ action.

The selective action of DENAQ on diseased tissue may reduce side effects on healthy retina, exactly what is desired from a vision-restoring drug. "Further testing on larger mammals is needed to assess the short- and long-term safety of DENAQ and related chemicals," says Dr. Kramer. "It will take several more years, but if safety can be established, these compounds might ultimately be useful for restoring to blind humans. How close they can come to re-establishing normal vision remains to be seen."

More information: Neuron, Tochitsky et al.: "Restoring visual function to blind mice with a photoswitch that exploits electrophysiological remodeling of retinal ganglion cells." dx.doi.org/10.1016/j.neuron.2014.01.003

add to favorites email to friend print save as pdf

Related Stories

Altering eye cells may one day restore vision

Jan 25, 2013

(Medical Xpress)—Doctors may one day treat some forms of blindness by altering the genetic program of the light-sensing cells of the eye, according to scientists at Washington University School of Medicine ...

Exercise may slow progression of retinal degeneration

Feb 10, 2014

Moderate aerobic exercise helps to preserve the structure and function of nerve cells in the retina after damage, according to an animal study appearing February 12 in The Journal of Neuroscience. The fi ...

Recommended for you

New learning mechanism for individual nerve cells

2 hours ago

The traditional view is that learning is based on the strengthening or weakening of the contacts between the nerve cells in the brain. However, this has been challenged by new research findings from Lund University in Sweden. ...

USC memory scientist Richard Thompson dies at 84

18 hours ago

Richard F. Thompson, the University of Southern California neuroscientist whose experiments with rabbits led to breakthrough discoveries on how memories are physically stored in the brain, has died. He was 84.

Modeling shockwaves through the brain

19 hours ago

Since the start of the military conflicts in Iraq and Afghanistan, more than 300,000 soldiers have returned to the United States with traumatic brain injury caused by exposure to bomb blasts—and in particular, ...

User comments