Researchers offer hearing hope for the profoundly deaf

Stimulation of inner-ear hair growth in guinea pigs found to improve cochlear implant results

PUBLISHED : Thursday, 24 April, 2014, 9:55pm
UPDATED : Thursday, 24 April, 2014, 9:55pm


A procedure that uses a series of electric jolts to inject laboratory-designed DNA molecules into cells of the inner ear may help to regrow auditory nerves in people with profound hearing loss, according to researchers.

In a paper published on Wednesday in Science Translational Medicine, a team of Australian researchers said they had used tiny electrodes and gene therapy to regenerate the nerve cells in a group of chemically deafened guinea pigs.

They said the procedure may one day improve the functioning of human cochlear implants, which are electronic devices that provide hearing sensations to the deaf.

"People with cochlear implants do well with understanding speech, but their perception of pitch can be poor, so they often miss out on the joy of music," said senior author Gary Housley, a professor of neuroscience at the University of South Wales in Sydney, Australia. "Ultimately we hope that after further research, people who depend on cochlear implant devices will be able to enjoy a broader dynamic and tonal range of sound." Housley and his colleagues studied the procedure on guinea pigs because the structure of the animals' inner ear was remarkably similar to that of humans.

The cochlea is shaped like a snail's shell and filled with a multitude of tiny hair cells that move in response to sound vibrations. Those vibrations are then converted into electrical nerve impulses that are carried to the brain.

If the hair cells are lost or damaged due to age, genetics, chemical poisoning or loud noise, they will not grow back. In some people who are profoundly deaf, an electrode may be implanted within the cochlea that can stimulate some nerve cells.

While cochlear implants help about 300,000 patients throughout the world to detect and interpret speech, researchers believe the hearing can be improved if nerve cells are encouraged to grow closer to the electrode.

"The development of electrode array-based CFE gene delivery may not only improve the hearing of cochlear implant recipients but also find broader therapeutic applications, such as in conjunction with deep brain stimulation, which uses electrode arrays similar to cochlear implant, to treat a range of neurological disorders, including Parkinson's disease," the study said.