As hearing specialists, one of the frustrations we experience in our practice is that the issues that have caused hearing problems in our patients can’t be reversed. One of the principal reasons for hearing loss, for example, is damage to the tiny hair cells in our inner ears that vibrate in reaction to sounds. Our sense of hearing is the result of these vibrations being translated into electrical impulses and transmitted to the brain for decryption.
Unfortunately, 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. Aging, infections, certain medications or exposure to loud sounds (resulting in noise-induced hearing loss) are all potential sources of damage. Once these hair cells are damaged in human ears, science has to date not found any way to repair or “fix” them. Consequently, hearing specialists and audiologists must use technologies such as hearing aids or cochlear implants to make up for hearing loss that is essentially irreversible.
If humans were more like fish or chickens, we would have other options. Though this may sound bizarre, it’s true, because unlike humans, some species of birds and fish have the ability to regenerate the hair cells in the inner ear if they become damaged, and thus get back their normal hearing. To name two such species, chickens and zebra fish have been proven to have the ability to spontaneously replicate and replace hair cells that have become damaged, and as a result regain their full functional hearing.
While it is crucial to point out at the outset that the following research is in its beginning stages and that no practical benefits for humans have yet been achieved, significant advancements in the treatment of hearing loss may come in the future from the groundbreaking Hearing Restoration Project (HRP). Funded by a not-for-profit organization called the Hearing Health Foundation, this research is presently being carried out in 14 different labs in the U.S. and Canada.What the HRP scientists are trying to do is isolate the molecules that allow this replication and regeneration in animals, with the purpose of discovering some way of stimulating similar regeneration of hair cells in humans.
This work is slow and demanding. Researchers need to sort through the many compounds active in the regeneration process – some of which expedite replication while others hinder it. But their hope is that if they can isolate the compounds that stimulate this regeneration process to happen in fish and avian cochlea, they can find a way to stimulate it to happen in human cochlea. The scientists in the various HRP labs are following different approaches to the challenge, some working on gene therapies, others working on the use of stem cells, nevertheless all share the same goal.
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 someday we will be able to help humans reverse their hearing loss as easily as chickens do.