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Researchers Develop Gene Therapy With Potential To Restore Sight To The Blind

April 22, 2011

Researchers at the Keck School of Medicine of USC have developed a potential therapy for blindness that involves delivering a gene encoding a light-sensitive protein to inner retinal cells, enabling photosensitivity in these cells and restoring visual function in mouse models.

The research, led by senior author Alan Horsager, Ph.D., a neuroscientist at the Keck School, focuses on blindness caused by retinitis pigmentosa and age-related macular degeneration, conditions that lead to gradual loss of photoreceptors in the retina and eventual blindness. Horsager's research targets other cells in the retina called bipolar cells, which are part of the retina's intricate signal processing system. The proof of concept paper was published on April 19 in the journal Molecular Therapy.

“It's a very targeted approach that maintains the natural processing of the retina,” said Horsager. “There is a lot more to understand, but initial indications suggest we have developed something that can have enormous benefit to people. Preclinical studies are the next step to determine the potential therapeutic benefit for humans.”

After the gene encoding the light-sensitive protein is delivered via an adeno-associated virus, the bipolar cells become light sensitive and take over the light-capturing function of the lost photoreceptors.

This effort builds on the research of Ed Boyden, Ph.D., assistant professor at the Massachusetts Institute of Technology (MIT). Horsager and Boyden, together with Ben Matteo, have co-founded Eos Neuroscience, Inc. to help translate this technology into the clinic. Dr. Horsager serves as the chief science officer for Eos Neuroscience, Inc., and has an equity interest in the company.

“This is a massive collaborative effort between USC, MIT, the University of Florida, and Eos Neuroscience, building on a lot of great science,” said Horsager. “We are simply aggregating this science and establishing proof-of-concept for a blindness therapy.”

The research establishes that this therapy works independent of the underlying cause of photoreceptor degeneration, suggesting that people suffering from retinitis pigmentosa or age-related macular degeneration would benefit.

“We conducted multiple studies to establish that this technology is safe and does not appear to generate any immune response or inflammation in the eye,” said Mehdi Doroudchi, Ph.D., the first author and head of cell biology at Eos. The delivery system, an adeno-associated virus, is currently being used in multiple clinical trials of gene therapy throughout the U.S. and abroad.

The technology used to make the bipolar cells light-sensitive, known as optogenetics, had its origins in a collaboration spearheaded by Boyden in 2004, which revealed that a light activated protein from algae known as channelrhodopsin-2, when expressed in neurons, made them activatable by light.Boyden's group has since revealed an entire family of light-sensitive proteins that enable neurons to be switched on and off by different colors of light, which are now in widespread use throughout the field of neuroscience for analyzing how neurons work in brain circuits.

“It's really exciting to think of the clinical applications opened up by the ability to control neurons by light,” said Boyden. “The eye, which can access light from the outside world, is a perfect test bed for the use of optogenetic tools for treating intractable disorders.”

View a video explaining the research.

Adapted from the Keck School of Medicine (University of Southern California)

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