One of the sometimes bothersome things about being a hearing care specialist
is that many of the circumstances we deal with which have caused our patients to lose their hearing cannot be reversed. For example, one of the extremely common reasons for hearing loss is damage to the tiny, sensitive hair cells that line the inner ear and vibrate in response to sound. These vibrations are then interpreted by the brain into what we think of as hearing.
These hair cell structures must be very small and sensitive to do their jobs correctly. It is precisely because they are very small and sensitive that they are also easily damaged. This damage may occur due to aging, certain medications, infections, and by prolonged exposure to high-volume noises, leading to noise-induced hearing loss, or NIHL. In humans, once these hair cells are damaged or destroyed, they cannot be regenerated or “fixed.” Since we cannot reverse the damage, hearing professionals and audiologists look to technology instead. We compensate 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. In contrast to humans, some fish species and birds actually have the ability to regenerate their damaged inner ear hair cells and regain their lost hearing. Bizarre, but true. 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
While it is important 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, significant advancements in the treatment of hearing loss may come in the future as the result of the innovative Hearing Restoration Project (HRP). Financed by a nonprofit organization called the Hearing Health Foundation, this research is presently being conducted in 14 unique laboratories in the United States and Canada.What the HRP scientists are attempting to do is isolate the compounds that allow this replication and regeneration in animals, with the purpose of finding some way of stimulating similar regeneration of inner ear hair cells in humans.
This research is slow and demanding. Researchers need to sift through the many molecules active in the regeneration process – some of which support replication while others impede 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. Some of the HRP researchers are pursuing gene therapies as a way to promote such regrowth, while others are working on using stem cells to accomplish the same goal.
Although this work is still in it’s early stages, our team wishes them speedy success so that their results can be extended to humans. Absolutely nothing would be more thrilling than to be able to offer our hearing loss patients a true cure.