Gene therapy improves hearing aid performance

Gene therapy improves hearing prostheses

04/26/2014

Tens of thousands of Germans have a cochlear implant. This hearing prosthesis helps deaf people whose auditory nerve is still functioning. As scientists have discovered in Sydney, Australia, gene therapy could further improve these devices.

Hearing loss is one of the most common sensory loss
Hearing loss, due to age, noise or genetic causes, is one of the most common sensory loss. According to figures from the World Health Organization (WHO), around 360 million people worldwide are affected. If the auditory nerve is still intact, an implant for the cochlea, the cochlea, can help. In this case, an electrode carrier is inserted into the inner ear behind the auricle. The technique, which has been used for more than three decades, converts sound into electrical impulses that the auditory nerve transmits to the brain. This allows the wearer to hear sounds and above all to understand speech. However, they are denied acoustic subtleties. This should now change a new gene therapy.

Ear prosthesis wearers escapes the joy of music
As Gary Housley from the University of New South Wales, Sydney, explained, people with cochlear implants „Understand speech well, but their perception of pitch can be so bad that they miss the pleasure of music.“ It was previously known that the growth factor BDNF (brain-derived neurotrophic factor) stimulates nerve cells to grow towards the cochlear implant. The wearer of the hearing prostheses could perceive acoustic stimuli more sensitively in the future, for example in music. This was reported by the researchers in a study in the journal „Science Translational Medicine“, co-funded by the implant manufacturer Cochlear Limited.

Guinea pigs were sensitive to noise after treatment
However, researchers have so far been unable to introduce the gene for the formation of BDNF into the tissue. Housley and his colleagues used to do so in guinea pigs so-called electroporation, with electrical impulses make the cell membrane permeable, so that the tissue can absorb new DNA parts. According to the scientists, the animals were particularly sensitive to sounds after treatment. Although BDNF production has slowed after three to six weeks, Housley believes that it could be maintained by the activity of the cochlear implant. As the researchers emphasized, electroporation itself is easy. „We think it is possible that this gene therapy will only prolong transplantation by a few minutes in the future“, so first author Jeremy Pinyon. „The surgeon using the device injects the DNA solution into the cochlea and fires electrical impulses after insertion to trigger the DNA transfer.“

Many questions left
However, other scientists believe that there are still many ambiguities. For example, Robert Shepherd and Andrew Wise of the University of Melbourne write in a comment that there are still questions about the duration of the effect or the optimal electroporation. In principle, however, the method can also be used for other applications, for example to stimulate damaged nerves, in the case of retinal prostheses or in deep brain stimulation, which is primarily used against Parkinson's disease. In a certain brain region, electrical impulses are supposed to prevent cell aggregates from burning in a morbid state, triggering symptoms such as stiffness or tremors. However, it must first be ensured to what extent the method works in humans.

Listening is an essential part of a person's social relationships
Millions of people worldwide suffer from hearing loss. More than 320,000 children and adults with inner ear hearing loss owe it to a cochlear implant that allows them to perceive the outside world acoustically. Some ten thousand of them in Germany. How important this is becomes clear when you realize that listening is a significant part of a person's social relationships. The deaf and the deaf often suffer from loneliness and depression, because they lack an essential means of communication. (Ad)