News that Boston scientists achieved what was once deemed impossible—inducing regrowth of the vital but perishable sensory hair cells in human inner ear tissue—suggests that the door has partially opened to reversing hearing loss in millions of people.
Humans are born with roughly 15 000 hair cells in each ear that are exquisitely sensitive and arranged linearly by the pitch they respond to, somewhat like piano keys, enabling them to pass along complex information about a sound’s frequency, timing, and intensity. But because they are built to sway and vibrate, they are also easily harmed, and, in adult mammals, once dead they do not regenerate.
Lyon J. Hearing Restoration: A Step Closer?. JAMA. 2017;318(4):319–320. doi:10.1001/jama.2017.5820