Many of the problems that cause hearing problems for our patients can’t be reversed which can be frustrating for our hearing specialists. Damage to the tiny, very sensitive hair cells of the inner ear is among the more common reasons for hearing loss. The work of these hair cells is to vibrate in response to sound waves. Our sense of hearing is the result of these vibrations being converted into electrical impulses and transmitted to the brain for decoding.
The sensitivity of these tiny hair cells enables them to vibrate in such a manner, and thus enables us to hear, but their very sensitivity makes them very fragile, and at risk of damage. The hair cells of the inner ear can become damaged as a result of exposure to high decibel noises (causing noise-induced hearing loss, or NIHL), by specific drugs, by infections, and by aging. In humans, once these hair cells have become damaged or destroyed, they cannot be regenerated or “fixed.” Since we cannot reverse the damage, hearing specialists and hearing instrument specialists look to technology instead. We make up for hearing loss due to inner ear hair cell damage with hearing aids and cochlear implants.
This would not be the case if humans were more like fish and chickens. That may sound like an odd statement, but it’s true, because – unlike humans – some birds and fish can regenerate inner ear hair cells, and thus regain their hearing once it has become lost. Chickens and zebra fish are just two examples of species that have the ability to spontaneously replicate and replace their damaged inner ear hair cells, thus allowing them to fully recover from hearing loss.
Could hearing loss in humans be reversed? Glimmers of hope are appearing from the groundbreaking research of the Hearing Restoration Project (HRP), but the research is at a very early stage and no practical benefits for humans have yet been achieved. The not for profit organization, Hearing Health Foundation, is currently sponsoring research at laboratories in the United States and Canada What the HRP scientists are attempting to do is identify the molecules that allow this replication and regeneration in animals, with the purpose of discovering some way of enabling similar regeneration of inner ear hair cells in humans.
The work is painstaking and difficult, because so many distinct compounds either help with replication or hinder inner ear hair cells from replicating. Researchers are hoping that what they learn about hair cell regeneration in avian or fish cochlea can later be applied to humans. The HRP researchers are taking a divide and conquer approach to attain their collective goal. While some labs work on gene therapies others work on approaches using stem cells.
As mentioned before, this research is still in its very early stages, but we join with others in wishing that it will be productive, and that one day we will be able to help humans cure their hearing loss as easily as chickens do.