Scientists regenerate cochlear hair cells

Photo credit: Karolina Grabowska

by Daniel Fink, MD, Chair, The Quiet Coalition

Mammals hear through a complex mechanism whereby sound pressure waves are transmitted from the tympanic membrane, or ear drum, through the small bones in the middle ear to the cochlea, where the pressure waves are transmitted to cochlear hair cells, distorting them to create ion flows that create electrical impulses transmitted to the brain where they are perceived as sound. Noise damages or destroys cochlear hair cells, causing noise-induced hearing loss. The only current treatment for all types of hearing loss, including noise-induced hearing loss, is amplification, with cochlear implantation reserved for congenital hearing loss and recently approved by Medicare for treatment of profound hearing loss.

Regeneration of dead or damaged cochlear hair cells has been the Holy Grail of hearing restoration research. This report from Harvard Medical School discusses recently published research published April 17 in PNAS documenting regrowth of cochlear hair cells through gene therapy in a mouse model. What makes this study significant is that the researchers injected novel chemical compounds directly into mouse cochleas after inducing hair cell loss with ototoxic drugs, and the cochlear hair cells regenerated. Other research has used actual gene therapy, but this study used chemicals to induce gene changes.

I hope this new treatment eventually works. It would appear to be far safer and potentially less expensive than actual gene therapy, which is currently approved for a limited number of conditions by the Food and Drug Administration’s Office of Tissues and Advanced Therapies.

As I have written before, while I hope hearing restoration research eventually works, I remain a skeptic. The human cochlea is a tiny structure about the size of a pea, deeply embedded in the hard temporal bone of the skull. The cochlea is additionally protected by a blood-labyrinth barrier that makes blood-borne delivery of drugs to the cochlea difficult.

And what makes me sad is that noise-induced hearing loss is the only type of hearing loss that is 100% preventable. Prevention is almost always better than treatment and prevention of noise-induced hearing loss is cheap and easy: Avoid loud noise exposure, leave the noisy environment, or use hearing protection devices.

Because if it sounds loud, it’s too loud, and your auditory health is at risk.

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