GENE THERAPY HEALS MALFUNCTIONING CELLS IN EAR
The findings could offer hope to people with hearing loss
“I am optimistic that our work can help lead to gene therapies that restore hearing”
Tiny sensory hair cells called stereocilia, located in your inner ear, are responsible for detecting sound. When these become damaged, either by genetic disorders, loud sounds or old age, it can lead to hearing difficulties and even deafness.
Now, in a series of experiments on mice, researchers based at the Salk Institute and the University of Sheffield have identified a protein that can be delivered to these hair cells via gene therapy in order to trigger their growth.
“Our discovery shows that hair cell function can be restored in certain cells,” said co-author Dr Uri Manor, assistant research professor and director of the Waitt Advanced Biophotonics Core at Salk.
“I was born with severe to profound hearing loss and feel it would be a wonderful gift to be able to provide people with the option to have hearing.”
Deafness that occurs in children before they are able to speak is commonly due to genetic factors. One such factor can lead to the stereocilia being underdeveloped, resulting in deafness.
Stereocilia hair cells are found throughout the cochlea, the spiral tube-like structure found within the inner ear. Regions of the cochlea that sense low frequencies have longer stereocilia, while regions that sense high frequencies have shorter stereocilia. When sounds enter the ear, they cause fluid within the cochlea to vibrate, which in turn causes the stereocilia to move. These hair cells then send signals to neurons, which pass on information about the sounds that we are hearing to the brain.
In a previous study, Manor found that the protein EPS8 was involved in determining the length of stereocilia. Without the protein, the growth of the hairs is stunted, and they remain very short.
In another earlier piece of research, co-author Prof Walter Marcotti, of the University of Sheffield, also discovered the link between EPS8 and stereocilia development.
For this latest study, the two researchers teamed up to design an experiment to see if adding EPS8 to stereocilia hair cells could trigger their regrowth and improve hearing in mice. They used a common gene therapy technique to deliver the protein to the hair cells on the back of a virus. They then investigated the effects using imaging techniques.
The team found that EPS8 increased the length of the stereocilia and restored their function in low-frequency cells, although not enough to restore the hearing of the mice.
However, they also found that the cells seemed to lose their ability to regenerate as they aged.
“EPS8 is a protein with many different functions, and we still have a lot more to uncover about it,” said Manor.
“I am committed to continuing to study hearing loss and am optimistic that our work can help lead to gene therapies that restore hearing.”
The researchers now plan to investigate the action of EPS8 further, with the hope of extending the age range over which it is effective.