Humans are unable to reverse the effects of hearing loss and according to WHO hearing loss affects more than 400 million people around the world.
Hearing is a complex process that involves the brain interpreting sounds that fall on the eardrum from soundwaves that enter the ear. The eardrum then vibrates and transmits these vibrations to bones in the middle ear that serves as a booster to the sound signal. Eventually, hair-like cells in the inner ear or cochlea pick up these vibrations and transform them into electrical signals that the brain can process.
Age or excessive exposure to loud noise can damage the cochlea, resulting in permanent hearing loss. Traditional treatment involves devices such as hearing aids, the effectiveness of which depends on the individual and their level of hearing loss.
Scientists have long known that fishes and birds are able to keep their hearing intact throughout life by regenerating the sensory hair cells found in the cochlea.
Research done earlier had identified a group of receptors, called epidermal growth factor (EGF) responsible for this regeneration process. The EGF was found to switch on support cells in the auditory system of birds that then sparked the production of new sensory hair cells.
For their new study, researchers at the University of Rochester and the Massachusetts Ear and Eye Infirmary have tried to recreate this process in mammals. They homed in on a specific receptor called ERBB2, found in support cells inside the cochlea, and trialed different methods that could use these receptors to activate the pathway.
By activating ERBB2 the study team was able to start a process that led to the production of cochlear support cells, which then resulted in stem cells transforming into the sensory hair cells. These cells also integrated with nerve cells, which is necessary for hearing. This was the first time that scientists were able to regrow sensory hair cells in ears of mammals.
More studies would be needed into the use and process of EGF receptors in order to carry out any kind of human trial. However, this new discovery could be the start of an improvement to millions of lives, said the researchers.