Posted on Feb 08, 2017, 6 a.m.
Harvard Medical School scientists have perfected a form of gene therapy that has enabled genetically deaf mice to hear sounds as quiet as a whisper.
Harvard Medical School scientists have perfected gene therapy to the point that it can restore hearing. Their research and experiments have shown that the hearing of genetically deaf mice can be restored to the point that they hear noises at 25 decibels. This decibel level is equivalent to that of a soft whisper.
The Nuances of Gene Therapy for Improved Hearing
Harvard's gene therapy researchers state the most important aspect of their gene therapy breakthrough is a vector they created known as "Anc80". This vector brings a therapeutic gene to the cells within the cochlea's outer ear that are quite difficult to access. These outer hair cells boost sound, empowering inner hair cells to transmit a much more powerful communication to the brain. Gwenaëlle Géléoc of Boston Children's Hospital's Department of Otolaryngology and F.M. Kirby Neurobiology Center, states the new system functions quite well by “rescuing” vestibular and auditory function to a degree that was not previously achieved in medical history.
Harvard's research team includes scientists employed by Massachusetts Eye and Ear. The group tested its gene therapy technique on mice with Usher Syndrome. This is a genetic disease that harms hearing as well as vision. Humans who are saddled with this disease are afflicted with a gene mutation that makes the protein harmonin ineffective. As a result, the hair cells responsible for accepting auditory signals and transmitting them to the brain are rendered useless.
The research team tapped into the power of its new vector to transmit an improved version of the gene, referred to as Ush1c, directly into the ear. It didn't take long for the ear's outer and inner hair cells to generate effective harmonin. Subsequent hearing tests conducted on mice proved that animals born deaf could hear. Some of these mice could even pick up on uber-soft auditory signals just like their “normal” peers.
The Magic of Gene Therapy
The scientific community is abuzz over gene therapy. Some believe gene therapy will ultimately prove to be the cure for deafness. It was only two years ago when scientists and investigators from Harvard and the University of Michigan's Hearing Research Institute found that the hearing-associated protein, NT3, can be stimulated through gene therapy. Additional approaches are geared toward stimulating the regeneration of hair cells within the ear. As an example, Harvard researchers have found that drugs referred to as “Notch inhibitors” can spur existing ear cells to transition into hair cells that improve hearing in mice.
The Harvard team reports its latest success with gene therapy made use of a similar technique that heightened hearing in 2015. However, these researchers now believe their newly generated vector will restore an even higher level of auditory ability. They also noted that the Ush1c gene applied to deaf mice served to heighten their balance. Mice with Usher Syndrome typically suffer from such poor balance.
The Future of Gene Therapy
The future looks quite bright for those who suffer from hearing deficiencies. The research described above is fantastic news for those who suffer from hearing loss. It is possible that gene therapy will eventually supplant cochlear implants that are currently used to improve hearing in young patients. Though Cochlear implants have served patients quite well, there is still room for improvement.
Patients would like to hear an extended range of frequencies and the direction of a sound's source. They would also like to be able to differentiate between the auditory nuances of background noise, voices, music etc. The added benefit of heightened physical balance will serve to enhance Usher Syndrome patients' balance and mobility.
Gwenaëlle S Géléoc et al. Gene therapy restores auditory and vestibular function in a mouse model of Usher syndrome type 1c. Nature Biotechnology, February 2017 DOI: 10.1038/nbt.3801