A number of the problems that cause hearing loss for our patients cannot be reversed which can be quite frustrating for our hearing specialists. For example, one of the most common causes of hearing loss is damage to the very small, sensitive hair cells that line the inner ear and vibrate in response to sound. What we think of as hearing are the translations of these vibrations into electrical energy, which is then sent to the brain.
The fact is that, the exact same sensitivity of these hair cells that allows them to respond to sounds and translate them into electrical impulses that our brains perceive as hearing also makes them fragile, and vulnerable to damage. This damage may occur due to aging, infections, medications, and by extended exposure to high-volume noises, resulting in noise-induced hearing loss. Once these hair cells are harmed in human ears, science has to date not found a way to repair or “fix” them. Consequently, hearing specialists and audiologists must use technologies such as hearing aids or cochlear implants to compensate for hearing loss that is essentially irreversible.
This would not be the case if humans were more like chickens and fish. Unlike humans, some fish species and birds actually have the ability to regenerate their damaged inner ear hair cells and regain their lost hearing. Odd, but true. Chickens and zebra fish are just two examples of species that have the capacity 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 innovative 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 funding research at laboratories in the United States and Canada Working to identify the molecules that allow the replication and regeneration in some animals, HRP researchers hope to find a way to stimulate human hair cells to do the same.
The work is painstaking and challenging, because so many distinct compounds either help with replication or hinder inner ear hair cells from replicating. But their hope is that if they can isolate the compounds that enable this regeneration process to happen in avian and fish cochlea, they can find a way to stimulate it to happen in human cochlea. The HRP researchers are taking a divide and conquer approach to attain their joint goal. While some laboratories work on gene therapies others focus on approaches using stem cells.
Although this research is still in the preliminary stages, our office wishes them quick success so that their findings can be extended to humans. Almost nothing would be more thrilling than to be able to provide our hearing loss patients a true cure.