Jul 8, 2015, 1:08pm EDT
Jessica Bartlett
Boston Business Journal
​Researchers used gene therapy to restore hearing in mice with a genetic form of deafness.
COURTESY/ POCKAFWYE VIA CREATIVE COMMONS

​Researchers used gene therapy to restore hearing in mice with a genetic form of… more

Researchers at Boston Children’s Hospital and Harvard Medical School have used gene therapy to restore hearing in mice with a genetic form of deafness.
The work, published today in the journal Science Translational Medicine, is a promising start for restoring hearing in humans that have profound hearing loss caused by genetic defects.

“These findings mark a defining moment in the way we understand, and can ultimately challenge, the burden of deafness in humans,” said Ernesto Bertarelli, co-chair of the Bertarelli Foundation, the primary funder of the research, in a release.
Scientists used gene therapy in mice that had mutations to the TMC1 gene, which account for 4 to 8 percent of cases in the common causes of genetic deafness.
Teams inserted the healthy gene using a virus in two types of mutant mice – one that had the gene TMC1 completely deleted, and another that had a mutation in the TMC1 gene.
Using gene therapy on the TMC1 gene, researchers completely restored hearing to the first mouse type, seeing mice jump at the sound of abrupt, loud tones. In the other mouse model, gene therapy in related gene TMC2 was partially successful at restoring hearing.
Scientists are optimistic about using the gene therapy in clinical trials, as the virus is already used in human gene therapy for blindness, heart disease, muscular dystrophy and other conditions.
But that work is still five to 10 years away. Researchers said they want to optimize the protocol and continue the trials in mice to see if mice retain hearing longer than the two months already observed. Other forms of genetic deafness might also be amendable to the same gene therapy strategy.

“Our gene therapy protocol is not yet ready for clinical trials—we need to tweak it a bit more—but in the not-too-distant future we think it could be developed for therapeutic use in humans,” said Jeffrey Holt, a scientist in the Department of Otolaryngology and F.M. Kirby Neurobiology Center at Boston Children’s and an associate professor of Otolaryngology at Harvard Medical School, in a release.
Holt hopes to eventually partner with clinicians at Boston Children’s Department of Otolaryngology on clinical trials.
While cochlear implants are useful for those with TMC1 mutations, clinicians said the findings could be life changing for the profoundly deaf.
“Cochlear implants are great, but your own hearing is better in terms of range of frequencies, nuance for hearing voices, music and background noise, and figuring out which direction a sound is coming from,” said Dr. Margaret Kenna, a specialist in genetic hearing loss at Boston Children’s Hospital. “Anything that could stabilize or improve native hearing at an early age is really exciting and would give a huge boost to a child’s ability to learn and use spoken language.”