Two studies, published in Nature Biotechnology, explored the possibility of using gene therapy in restoring hearing and balance.
made use of viruses that can be altered in a laboratory to provide a "vector". Vectors, then, can carry the corrected therapeutic DNA into the cells. This technique alters the abnormal gene expression to correct the genetic disease.
Unaffected mice, at left, have sensory hair bundles organized in 'V' formations with three rows of cilia (bottom left). The abnormality is restored after gene therapy treatment (c) Gwenaelle Géléoc and Artur Indzkykulian
The first study was led by Harvard Medical School senior researchers. They developed a new synthetic vector called, Anc80, in 2015 at Massachusetts Eye and Ear's Grousbeck Gene Therapy Center.
The Anc80, developed by Jeffrey R. Holt, Ph.D., of Boston's Children's Hospital in Massachusetts, Konstantina Stankovic, Ph.D., of Massachusetts Eye and Ear, and Luk H. Vandenberghe, Ph.D., could successfully transfer genes to the harder-to-reach areas of the outer hair cells when introduced into the cochlea.
"We have shown that Anc80 works remarkably well in terms of infecting cells of interest in the inner ear," Stankovic told the Medical News Today
. "With more than 100 genes already known to cause deafness in humans, there are many patients who may eventually benefit from this technology."
The second study led by Gwenaëlle Géléoc, Ph.D., of the department of Otolaryngology and F.M. Kirby Neurobiology Center at Boston's Children's Hospital, used Anc80 in mice with Usher syndrome. Usher syndrome causes abnormalities of the inner ear, which leads to partial or total hearing and vision loss, eventually resulting to impaired balance.
Results showed that 9 out of 25 mice heard sounds below 80 decibels. While some of the mice could hear sounds as quiet as 25-30 decibels.
"Now, you can whisper, and they can hear you," says Géléoc.
Mice that were treated soon after birth had improved hearing and balance. However, the mice that were treated 10-12 days after birth didn't get their hearing and balance restored.
"Anything that could stabilize or improve native hearing at an early age would give a huge boost to a child's ability to learn and use spoken language," notes Margaret Kenna, a specialist in genetic hearing loss at Boston's Children's Hospital who conducts research into Usher syndrome.