A number of the problems that cause hearing problems in our patients cannot be reversed which is frustrating for our hearing professionals. Damage to the very tiny, very sensitive hair cells of the inner ear is one of the more prevalent reasons for hearing loss. The work of these hair cells is to vibrate in response to sound waves. These vibrations are then interpreted by the brain into what we think of as hearing.
These hair cell structures have to be very small and sensitive to do their jobs correctly. It is precisely because they are small and sensitive that they are also readily damaged. Aging, infections, certain medications or prolonged exposure to loud sounds (resulting in noise-induced hearing loss/NIHL) are all potential sources of damage. The hair cells in human ears cannot be regenerated or “fixed” after they are damaged or destroyed. Instead, hearing professionals and audiologists must use technological innovations such as hearing aids or cochlear implants to make up for hearing loss that is in essence irreversible.
Things would be a lot simpler if we humans were more like chickens and fish. That may sound like a peculiar statement, but it’s true, because – unlike humans – some fish and birds can regenerate inner ear hair cells, thereby regaining their hearing after it is lost. To name two 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, thereby regaining their full functional hearing.
Could hearing loss in humans be reversed? Glimmers of hope are emerging from the groundbreaking research of the Hearing Restoration Project (HRP), but the research is preliminary and no practical benefits for humans have yet been achieved. Funded by a non-profit organization called the Hearing Health Foundation, this research is presently being conducted in 14 unique labs in Canada and the United States.What the HRP researchers are trying to do is isolate the molecules that allow this replication and regeneration in animals, with the goal of finding some way of enabling similar regeneration of inner ear hair cells in humans.
Because there are so many distinct compounds involved in the regeneration process – some that facilitate replication, some that hinder it – the researchers’ work is slow-moving and challenging. Scientists are hoping that what they learn about 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 stimulate such regrowth, while others are working on stem cell-based approaches.
Although this research is still in the preliminary 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.