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Hearing loss affects millions of people around the world, and in around half of those cases the root cause is genetic. Now, medical researchers have been able to restore the hearing and balance in mice by inserting mutated genes into their bodies. Two papers published in the Nature Biotechnology journal describe the results.
"We demonstrate recovery of gene and protein expression, restoration of sensory cell function, rescue of complex auditory function and recovery of hearing and balance behaviour to near wild-type levels," otolaryngologists from the Harvard Medical School say in the research paper.
It says the work shows an "unprecedented recovery of inner ear function" and claims the "biological therapies to treat deafness may be suitable for translation to humans".
During the work, young mice were used to prove the method works. The mice had been artificially administered with Usher syndrome type IC, which in human children causes deafness, balance dysfunction, and blindness.
Most people born with type I and type II Usher syndrome suffer with severe to profound hearing loss as well as vision problems. Those with type III experience hearing loss later in life. The work from the Harvard medical academics focussed purely on the hearing loss aspect of the syndrome.
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To tackle the deafness, the research team injected a synthetic version of the adeno-associated virus - which has very little impact on humans - into the ears of mice. Within the virus was a normal copy of the mutated Ush1c gene, which causes deafness in the syndrome. It was the first time scientists have been able to find a virus that can enter the inner ear and deliver genes to the inner and outer hair cells needed for normal hearing ability.
"Delivery of a normal copy of the mutated gene, Ush1c, to the cochlea soon after the mice were born led to high levels of Ush1c protein in outer and inner hair cells, repair of damaged hair cell bundles, and a robust improvement in hearing and balance behaviour, enabling profoundly deaf mice to hear sounds at the level of whispers," a statement published alongside the research said.
"They can restore the hearing defect by the gene transfer," Andrew Forge an emeritus professor of auditory cell biology at University College London and author on the first Nature paper, tells WIRED.
Ruth Taylor, another UCL researcher involved in the work, tested the gene transfer method with human tissue. Using vestibular tissue the UCL academics were able to show the virus could transfer the gene to the human tissue in culture. "They did a lot of proof of concept in mice," Forge says. "The bit we did is the extra bit to show this could work in people."
He explains the work - and the field in general - is trying to answer one big question: "Can you manipulate the system to cure things that are wrong?"
Forge adds: "These kinds of therapies, if there is going to be a therapy, will be the way it is going to be working".
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Gene therapy allows 'deaf' mice to hear - Wired.co.uk