A number of the problems that cause hearing loss in our patients can’t be reversed which can be frustrating for our hearing specialists. For example, one of the most 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. These vibrations are translated by the brain into what we call hearing.
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 extremely fragile, and prone to damage. Aging, infections, certain medications or exposure to loud sounds (resulting in noise-induced hearing loss/NIHL) are all potential sources of damage. Once these hair cells are damaged in human ears, science has as yet not found any way to repair or “fix” them. Instead, hearing professionals and audiologists 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 chickens or fish, we’d have other options available. That may sound like an odd statement, however it is true, because – unlike humans – some fish and birds can regenerate the hair cells in their inner ears, thereby regaining their hearing once it has become lost. To name 2 such species, zebra fish and chickens have been shown to have the ability to spontaneously replicate and replace inner ear hair cells that have become damaged, and as a result regain their full functional hearing.
Could hearing loss in humans be reversed? Flickers of hope are emerging from the groundbreaking research of the Hearing Restoration Project (HRP), but the research is preliminary and no useful benefits for humans have yet been achieved. The not for profit organization, Hearing Health Foundation, is currently sponsoring research at laboratories in Canada and the US Working to isolate the molecules that allow the replication and regeneration in some animals, HRP scientists hope to find some way to stimulate human inner ear hair cells to do the same.
Because there are so many different compounds mixed up in regeneration process – some that assist in replication, some that hinder it – the scientists’ work is slow and difficult. By determining which of the compounds regulate this process in avian or fish cochlea, the scientists are hoping to establish which molecules promote hair cell growth. The researchers in the various HRP laboratories are following different approaches to the challenge, some pursuing gene therapies, others working on the use of stem cells, nevertheless all share the exact same objective.
Although this research is still in it’s early stages, our team wishes them speedy success so that their results can be extended to humans. Nothing would be more satisfying than to be able to offer our hearing loss patients a true cure.