A number of the conditions that cause hearing loss for our patients can’t be reversed which is frustrating for our hearing specialists. Damage to the 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 sounds. Our sense of hearing is the result of these vibrations being translated into electrical energy and transmitted to the brain for decoding.
The sensitivity of these tiny hair cells allows them to vibrate in such a manner, and thus enables us to hear, but their very sensitivity makes them very fragile, and at risk of damage. The hair cells of the inner ear can become damaged as a result of exposure to high decibel sounds (causing noise-induced hearing loss, or NIHL), by specific drugs, by infections, and by aging. In humans, once these hair cells have become damaged or destroyed, they can’t be regenerated or “fixed.” Since we can’t reverse the damage, hearing specialists and audiologists look to technology instead. We compensate for hearing loss due to inner ear hair cell damage with hearing aids and cochlear implants.
Things would be a lot simpler if we humans were more like chickens and fish. Though this may sound odd, it’s true, because unlike humans, some species of fish and birds have the ability to regenerate their inner ear hair cells if they become damaged, and thus regain their normal hearing. To name a couple such species, chickens and zebra fish have been shown to have the capacity to spontaneously replicate and replace hair cells that have become damaged, and as a result regain their full functional hearing.
While it is important to state at the outset that the following research is in its beginning stages and that no practical benefits for humans have yet been achieved, considerable advancements in the treatment of hearing loss may come in the future from the innovative Hearing Restoration Project (HRP). Funded by a not for profit organization called the Hearing Health Foundation, this research is currently being conducted in 14 different labs in the United States and Canada.Working to isolate the compounds that allow the replication and regeneration in some animals, HRP researchers hope to find a way to enable human hair cells to do the same.
This research is slow and challenging. Scientists need to sort through the many compounds involved in the regeneration process – some of which support replication while others hinder it. But their hope is that if they can identify the compounds that enable this regeneration process to happen in avian and fish cochlea, they can find a way to enable it to happen in human cochlea. The HRP researchers are taking a divide and conquer approach to attain their collective goal. While some labs work on gene therapies others work on approaches using stem cells.
Although this research is still in the preliminary stages, our office wishes them speedy success so that their findings can be extended to humans. Nothing would be more thrilling than to be able to provide our hearing loss patients a true cure.