Gene Therapy May Enhance Cochlear Implants, Animal Study Finds

By Steven Reinberg HealthDay Reporter

WEDNESDAY, April 23, 2014 (HealthDay News) -- Australian researchers say that gene therapy may one day improve the hearing of people with cochlear implants, allowing them to appreciate music and hear in noisy environments.

In experiments with deaf guinea pigs, senior study author Gary Housley and colleagues found that inserting genes in the area of the cochlear implant and passing an electric charge through the implant stimulated the growth of cochlear cells.

"Our study found a [new] way to provide safe localized delivery of a gene to the cochlea, using the cochlear implant device itself. The gene acts as a nerve growth factor, which stimulates repair of the cochlear nerve," said Housley, a professor and director of the Translational Neuroscience Facility at the University of New South Wales, in Sydney.

The cochlear implant is surgically placed in the cochlea, in the inner ear. The implant works by using a line of small electrodes within the cochlea to selectively stimulate cochlear nerve fibers at different positions and enhancing different sounds, or frequencies, Housley explained.

"In the cochlea of a person with good hearing, sound vibrations are encoded by sensory cells, called 'hair cells,' which stimulate the cochlear nerve fibers," he said. "With hearing loss, the hair cells are lost, and without them the cochlear nerve fibers die and retract into the bone within the core of the cochlea."

This makes the job of the cochlear implant difficult as the amount of electrical current needed to stimulate the nerves is quite high, Housley added.

The gene therapy, which makes the cells close to the electrode produce the nerve growth factor, causes the nerve fibers to grow out to those cells -- and therefore to the electrodes, he explained. This means that much less current is needed, so more selective groups of nerve fibers can be stimulated.

"In the future, people with cochlear implants may get this gene therapy at the time of their implant, and the computer system -- which is part of the cochlea implant that converts sound to electrical pulses along the array of electrodes -- should be able to provide a better sound perception," Housley said.

Scientists note, however, that research with animals often fails to provide similar results in humans.

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Gene Therapy May Enhance Cochlear Implants, Animal Study Finds