Genetically deaf mice showed signs of much-improved hearing in a new study conducted by researchers from the Boston Children's Hospital and Harvard Medical School.

According to a report from Eurekalert, a previous team from the two organizations already used gene therapy to restore hearing in deaf mice back in 2015. However, this new study makes use of an improved gene therapy vector that offers even better results. The mice were shown to have ended up with a higher level of hearing, capable of detecting down to 25 decibels, which is equal to a whisper.

The findings were published in two separate papers published in the journal Nature Biotechnology.

Central to the results is a new synthetic vector, dubbed Anc80, that's able to get genes to the outer hair cells, which are typically more difficult to reach than the inner hair cells that previous studies targeted.

"We have shown that Anc80 works remarkably well in terms of infecting cells of interest in the inner ear," senior investigator of the first paper Konstantina Stankovic, an otologic surgeon at Mass. Eye and Ear and associate professor of otolaryngology at Harvard Medical School, explained. "With more than 100 genes already known to cause deafness in humans, there are many patients who may eventually benefit from this technology."

In the second paper, another team of researchers tested Anc80 in a mouse model of Usher syndrome, which is the most common genetic form of deaf-blindness. Study leader Gwenaëlle Géléoc, PhD., of the Department of Otolaryngology said that it proved to be the most effective strategy they've encountered.

"Outer hair cells amplify sound, allowing inner hair cells to send a stronger signal to the brain," she added. "We now have a system that works well and rescues auditory and vestibular function to a level that's never been achieved before."

It will take a while for humans to benefit from this technology, although it gets the scientists on the right track. One of the problems is that the mice were treated from birth and their hearing and balance failed to get restored if gene therapy is 10 to 12 days delayed.