As hearing professionals, one of the sometimes frustrating things we encounter in our practice is that the issues that have caused hearing problems in our patients cannot be reversed. For example, one of the extremely common causes of hearing loss is damage to the tiny, 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 impulses which are sent to and interpreted in the brain.
These hair cell structures must be really small and sensitive to do their jobs correctly. It is precisely because they are small and sensitive that they are also readily damaged. The hair cells of the inner ear can become damaged as a result of exposure to loud sounds (causing noise-induced hearing loss, or NIHL), by certain medications, by infections, and by aging. In humans, once these hair cells have become damaged or destroyed, they can’t be regenerated or “fixed.” Instead, hearing professionals and audiologists must use technologies such as hearing aids or cochlear implants to compensate for hearing loss that is in essence irreversible.
This would not be true if humans were more like fish and chickens. That may sound like a peculiar statement, but it’s true, because – unlike humans – some birds and fish can regenerate the hair cells in their inner ears, and thus regain their hearing after it is lost. For reasons that are not fully understood, zebra fish and chickens have the ability to spontaneously duplicate and replace damaged hair cells, and thus achieve full functional recovery from hearing loss.
While it is important to point out at the outset that the following research is in its early stages and that no practical benefits for humans have yet been achieved, sizeable breakthroughs in the treatment of hearing loss may come in the future from the innovative Hearing Restoration Project (HRP). The not-for-profit organization, Hearing Health Foundation, is currently sponsoring research at laboratories in the U.S. and Canada What the HRP researchers are attempting to do is identify the compounds that allow this replication and regeneration in animals, with the purpose of finding some way of enabling similar regeneration of hair cells in humans.
The work is painstaking and difficult, because so many different molecules either help with replication or hinder hair cells from replicating. But their hope is that if they can identify the molecules 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 researchers in the various HRP labs are following different approaches to the problem, some pursuing gene therapies, others working on the use of stem cells, but all share the same objective.
Our entire office extends to them our best wishes and hopes for a great success, because absolutely nothing would thrill us more than being able to fully heal our clients’ hearing loss.
