Mice are deaf

Medical research Gene therapy makes deaf mice hear

About one in 1,000 children is born deaf, write the researchers at the University Medical Center Göttingen. This means that deafness is the most common congenital impairment of the senses. There are currently more than 140 different genes known to be responsible for poor hearing. If they are damaged, it leads to all sorts of degrees of deafness. Since this is inherited recessively in three quarters of all cases, there is no longer an intact copy of the gene that the cells need as a blueprint for a specific protein. So you just don't know how it should be formed. This protein is called otoferlin.

Too little Otoferlin makes hearing "tired"

If the protein otoferlin is missing, it leads to deafness. The sensory cells of the inner ear can then no longer transmit signals to the auditory nerve. Affected people could often perceive soft sounds almost as well as hearing people, but they could barely understand spoken language. If the tones are consistently loud, they become increasingly quieter for the deaf caused by Otoferlin. Scientists also say that hearing is "tired".

Missing gene smuggled into the inner ear

Because the affected people lack a certain gene, scientists around the world have been trying for some time to combat deafness with the help of gene therapy. The Göttingen doctors have apparently succeeded for the first time - at least with mice. They write that in their publication in the journal "EMBO Molecular Medicine".

The researchers smuggled the missing gene into the deaf mice using viruses. And that actually worked: with the help of fluorescent antibodies, they were able to detect newly formed otoferlin in the sensory cells, they write. The smuggled blueprint was correctly implemented by the body cells and also did not contain any sequences of the virus that transported it to the right place. So the scientists were able to prove that the new protein works. And the deaf mice could actually hear again.

The researchers checked the newly acquired hearing ability of their test mice with a hearing test. For this purpose, click noises were played to the animals, which only trigger electrical signals in the brain in hearing mice. After gene therapy, they could also be detected in the previously deaf mice. For the Göttingen researchers, this is proof that gene therapy restored the hearing of the mice.

Gene therapy for people within reach?

In the next step, the researchers want to try to further improve the viruses - i.e. the transport vehicle for the otoferlin gene.

We are working intensively on a strategy to achieve slightly higher amounts of protein in the sensory cells and thus completely restore hearing.

Priv.-Doz. Dr. Ellen Reisinger, University Medical Center Göttingen

If that succeeds, gene therapy for this form of deafness will also be within reach in humans, according to the researcher. A cooperating US company is already carrying out further experiments such as toxicity tests in order to be able to start clinical studies as soon as possible.

Reisinger also said that the researchers hope that this gene therapy will only have to be carried out once, "since the sensory cells in the inner ear exist our entire life without being exchanged, and the virus DNA typically remains stable in the cell nuclei." The Otoferlin-related deafness thus has a good chance of being the first form of congenital deafness that can be treated with gene therapy, Reisinger continues.

In the future, the researchers also want to develop similar therapies for other forms of deafness. But that is not always possible: Gene therapy only helps with those forms of deafness in which all cells of the inner ear are present. Unfortunately, this is not the case with many deaf people.