Dr. Zhou-Hua Pan

Detroit, Mich. Wayne State University researchers and colleagues, led by Zhuo-Hua Pan, Ph.D., associate professor of Anatomy and Cell Biology in the School of Medicine, reports a new way to restore visual responses in blind mice. This National Eye Institute of the NIH supported research is published in today’s issue of Neuron, a highly regarded journal which publishes reports of novel results in any area   of the neurosciences.

Vision normally begins when rods and cones, also called photoreceptors, respond to light and send signals through other retinal neurons, called inner retinal neurons (interneurons), and the optic nerve to the visual cortex of the brain where visual images are formed. Unfortunately, in some genetic diseases such as retinitis pigmentosa, rods and cones degenerate and die, leading to blindness. At present, no treatment is available for restoring vision once rods and cones, the normally light-sensitive cells in the retina, have been lost. 

Dr. Pan and his colleagues took an unprecedented approach. Using a harmless virus, they introduced a gene encoding a light-sensitive protein, called channelrhodopsin-2 (ChR2), from green algae into surviving inner retinal neurons in mice that were genetically bred to lose rods and cones, a condition similar to the blinding disease retinitis pigmentosa in humans. They found that the introduced ChR2 protein made the inner retinal neurons become light sensitive. What’s more, they found, the ChR2 protein persisted for long periods in these neurons, and the neurons generated signals that were transmitted to the visual cortex of the animals’ brains.

“Our study demonstrates the feasibility of restoring visual responses in mice after they lose the light-sensitive photoreceptor cells,” said Dr. Pan. “It raises the possibility that this approach may be a potential strategy for the treatment of blindness caused by rod and cone degeneration in humans.”

“With this strategy, the investigators have made a paradigm shift in the field and opened the possibility of genetically modifying the surviving retinal interneurons to function as a replacement light-sensing receptor,” wrote John Flannery and Kenneth Greenberg of University of California, Berkeley, in a preview of the paper in the same issue of Neuron. “This publication is clearly a significant first step into this new field of re-engineering retinal interneurons as genetically modified ‘prosthetic’ cells,” they wrote.

“This innovative gene-transfer approach is certainly compelling,” said Paul A. Sieving, M.D., Ph.D., director of vision research at the National Institutes of Health. “This is a clever approach that offers the possibility of some extent of vision restoration at some time in the future.”

According to Dr. John P. Oliver, WSU’s vice president for Research, “Other forms of retinal degenerative eye diseases may possibly be treated by gene-based therapies in the future. Dr. Pan’s exciting research may improve the lives of many in the future.”

Dr. Pan and his colleagues said that further studies are needed to determine whether the light signals reaching the visual cortex can be perceived by the brain as usable vision. Also, they stated, a number of technical improvements will be required to better fit the need for vision restoration.

Dr. Pan of Troy, Michigan received his B.S. degree from the University of Science & Technology of China, his M.S. from the Institute of Biophysics at the Chinese Academy of Science, and his Ph.D. from the State University of New York at Buffalo.

Wayne State University is one of the nation’s pre-eminent public research universities in an urban setting. Through its multidisciplinary approach to research and education, and its ongoing collaboration with government, industry and other institutions, the university seeks to enhance economic growth and improve the quality of life in the city of Detroit, state of Michigan and throughout the world.