One of the sometimes frustrating things about being a hearing care specialist
is that a lot of the circumstances we deal with which have caused our clients to lose their hearing can’t be reversed. For example, one of the extremely 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 call hearing are the translations of these vibrations into electrical impulses which are 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 perceive as hearing also makes them fragile, and vulnerable to damage. This damage may occur due to aging, certain medications, infections, and by extended exposure to high-volume noises, leading to noise-induced hearing loss, or NIHL. The hair cells in human ears cannot be regenerated or “fixed” once they have become damaged or destroyed. Instead, hearing instrument specialists and hearing instrument specialists must use technological innovations such as hearing aids or cochlear implants to compensate for hearing loss that is in essence irreversible.
If humans were more like fish or chickens, we’d have other options. Although this might sound odd, it’s true, because unlike humans, some species of birds and fish can regenerate their inner ear hair cells if they become damaged, and thus get back their normal hearing. To name a couple such species, chickens and zebra fish have been proven to have the capacity to spontaneously replicate and replace hair cells that have become damaged, thereby regaining their full functional hearing.
Bearing in mind that this research is preliminary and has as yet produced no proven benefits for humans, some hope for the treatment of hearing loss comes from research called the Hearing Restoration Project (HRP). This research, financed by the not for profit Hearing Health Foundation, is currently being conducted in 14 laboratories in the United States and Canada. Researchers included in the HRP are working to isolate the compounds that allow the hair cells in certain animals to replicate themselves, with the future goal of finding some way to enable human inner ear hair cells to do the same thing.
This research is painstaking and challenging. Researchers need to sift through the many compounds active in the regeneration process – some of which support replication while others impede it. By determining which of the compounds regulate this process in avian or fish cochlea, the scientists are hoping to pinpoint which molecules promote hair cell growth. The HRP researchers are taking a divide and conquer approach to achieve their collective goal. While some labs work on gene therapies others work on approaches using stem cells.
Our entire office extends to them our well wishes and hopes for a great success, because absolutely nothing would delight us more than being able to completely reverse our clients’ hearing loss.