Scientists develop new gene therapies to treat genetic hearing loss

The Salk Institute has made a breakthrough that may lead to new treatments for genetical hearing loss. Gene therapy in which a specific protein is delivered can help hair cells that were damaged grow properly, allowing for enhanced hearing.

Sensory hair cells are an essential component of our auditory system. They line the cochlea's surface with long structures called stereocilia, which vibrate in response to sound waves and produce electrical signals that are then sent to the brain. However, a lack of protein EPS8, which regulates the length of these hair cells, causes one form of genetic deafness. They're too short without it.

In a new research, the researchers looked into whether restoring EPS8 might help hair cells grow to their normal length and restore hearing. Working in mice that had been genetically engineered to lack EPS8 and were therefore deaf, the team tested whether an adeno-associated virus might be used as a transport mechanism for the protein to reach the animals' inner ears.

They found that the added EPS8 stimulated the stereocilia to grow longer, allowing more function to the cells that receive lower-frequency sounds.

However, there are a few drawbacks. The treatment did not work in mice after a certain age, suggesting that it's critical to intervene early before the hair cells develop. In humans, applying prenatal gene therapy would be required since by birth it would already be too late. However, with further research, the team aims to extend the timeframe for application.

“EPS8 is a protein with many different functions, and we still have a lot more to uncover about it,” said Uri Manor, co-senior author of the study. “I am committed to continuing to study hearing loss and am optimistic that our work can help lead to gene therapies that restore hearing.”

Some teams have discovered success in repairing hearing using gene therapy by targeting other genes. This can include regrowing either inner or outer hair cells, correcting genetic abnormalities that cause them to become disordered, or treating age-related damage to other structures.