Among the sometimes bothersome things about being a hearing specialist is that a lot of the conditions we encounter that have caused our patients to lose their hearing cannot be reversed. Damage to the very tiny, sensitive hair cells of the inner ear is among the more prevalent reasons for hearing loss. The work of these hair cells is to vibrate in response to sound waves. What we think of as hearing are the translations of these vibrations into electrical energy, which is then sent to the brain.
Sadly, the exact same sensitivity of these hair cells that allows them to react to sounds and translate them into electrical impulses that our brains understand as hearing also makes them fragile, and vulnerable to damage. Aging, certain medications, infections 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 as yet not found a way to repair or “fix” them. Consequently, hearing professionals and audiologists must use technological innovations such as hearing aids or cochlear implants to make up for hearing loss that is essentially irreversible.
Things would be a lot easier if we humans were more like fish and chickens. In contrast to humans, some fish species and birds have the ability to regenerate their damaged inner ear hair cells and recover their lost hearing. Bizarre, 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.
While it is vital to mention at the outset that the following research is in its beginning stages and that no practical benefits for humans have yet been achieved, sizeable advancements in the treatment of hearing loss may come in the future from the groundbreaking Hearing Restoration Project (HRP). The not for profit organization, Hearing Health Foundation, is currently conducting research at laboratories in Canada and the US What the HRP researchers are trying to do is isolate the compounds that allow this replication and regeneration in animals, with the goal of finding some way of stimulating similar regeneration of hair cells in humans.
This research is slow and challenging. Researchers need to sort through the many compounds involved in the regeneration process – some of which support replication while others inhibit it. Scientists are hopeful that what they learn about inner ear hair cell regeneration in fish or avian cochlea can later be applied to humans. The scientists in the various HRP laboratories are following different approaches to the challenge, some pursuing gene therapies, others working on the use of stem cells, but all share the exact same objective.
Although this work is still in it’s preliminary stages, our office wishes them speedy success so that their findings can be extended to humans. Absolutely nothing would be more enjoyable than to be able to provide our hearing loss patients a true cure.
