Over the years, some truly amazing progress has been made when it comes to restoring varying types of hearing impairments. And this is more important than ever with 20% of today’s teenagers having some form of hearing loss — which is 30% higher than it was in the 1980s and 1990s. While 83% of learning occurs visually, 11% happens through hearing. Fortunately, recent research done by an international team has made progress in restoring DFNB9 deafness in mice using gene therapy.

DFNB9 deafness is one of the most common forms of congenital deafness, which is hereditary. Individuals with this type of deadness are lacking in the gene coding for otoferlin. This protein is crucial for people to be able to transmit sound information.

The research team consisted of researchers from Miami University, Columbia University, San Fransisco University, the Institut Pasteau, the University of Clermont Auvergne, Inserm, Sorbonne University, and College de France. The findings were published in the PNAS journal.

Using gene therapy, the scientists were about to carry out and intracochlear injection of otoferlin into an adult mouse with DFNB9 deafness. And in doing this, they were able to reinstate the auditory synapse function to a near-normal level, allowing the mice to hear again.

Unfortunately, even with about 46.5 million surgical procedures occurring in the U.S. every year, placing a cochlear implant is currently the only treatment option for humans with this type of deafness.

The trials consisted of the researchers administering otoferlin to newborn mice’s developing cochlea before the mice were even able to hear. But in humans, hearing is possible well before they’re born, which could pose a problem — there would be a very small window of opportunity to conduct gene therapy in fetuses. So instead, the gene therapy would have to occur after the child was born and the hearing loss was diagnosed.

Mice that did receive the gene therapy showed that their hearing was restored four weeks after the gene was injected. And six months later, the mice still showed signs of near-normal hearing levels. These results were with just one single intracochlear injection.

The scientists are hopeful that these results could lead to human gene therapy trials for patients with DFNB9 deafness.

In the published paper, the researchers stated, “Our results document both the preventive and curative efficacies of local gene therapy in a mouse model of DFNB9, while expanding the scope of potential AAV gene therapy applications for human hereditary deafness forms… We show that local gene therapy in the mutant mice not only prevents deafness when administered to immature hearing organs, but also durably restores hearing when administered at a mature stage, raising hopes for future gene therapy trials in DFNB9 patients.”