Science has taken a promising step toward curing the nearly 50 million people who suffer from hearing loss.
In the latest issue of Neuron, researchers from the Massachusetts Eye and Ear Infirmary and the Harvard Medical School demonstrated that they can regenerate the tiny hairs in mammalian ears, thus helping to restore hearing damaged by noise. This is the first time auditory hair cells have been regenerated in an adult mammal.
Inside your ears, thousands of these sensory hairs are attached to the cochlea, a snail-shaped structure sound waves travel through. These hairs help to convert the sound vibrations you hear into electrical signals to be sent to your brain.
Unlike in birds and fish, when these cells are damaged in mammals they cannot regenerate on their own.
“Hair cells are the primary receptor cells for sound and are responsible for the sense of hearing,” senior author, Dr. Albert Edge, of Harvard Medical School and Massachusetts Eye and Ear, said in a news release. “We show that hair cells can be generated in a damaged cochlea and that hair cell replacement leads to an improvement in hearing.”
The Science Behind the Breakthrough
Researchers selected a drug that had previously been shown to regenerate hair cells when isolated from the ear and added to stem cells. The drug inhibits an enzyme, gamma-secretase, from performing chain reactions in cells. Importantly, it also inhibits the expression of a protein called Notch, which allows adjacent cells to communicate with one another.
Researchers applied the drug to the cochleas of deaf mice, which caused the supporting cells surrounding their hair cells to turn into hair cells themselves. The new hair cells improved the animals' hearing in the area directly treated with the drug.
“We’re excited about these results because they are a step forward in the biology of regeneration and prove that mammalian hair cells have the capacity to regenerate,” Edge said. “With more research, we think that regeneration of hair cells opens the door to potential therapeutic applications in deafness.”
Causes of Hearing Loss
Hearing loss can be caused by numerous factors, including exposure to loud noises, age, infection, toxins, and some anti-cancer drugs.
Hearing loss caused by loud noises is a growing concern in industrialized countries, namely in large cities where excessive noise from a variety of sources is a constant issue. The regular use of personal media devices—iPods, cell phones, and anything else you plug headphones into—turned up beyond reasonable volume levels also increases your risk of ear damage and hearing loss.