LOS ANGELES, CALIFORNIA –Dr. James Dewey, a researcher at the University of Southern California (USC), has been awarded a grant from the National Institutes of Health (NIH) to further investigate the function of outer hair cells in the inner ear of mammals. With a better understanding of the function of these cells, the research could potentially help lead to future treatments for hearing loss.
Outer hair cells are one of two types of sensory cells in the inner ear. They are much more numerous than inner hair cells, yet fewer auditory nerve fibers connect to them. Scientists have long thought outer hair cells act as a mechanical amplifier to improve hearing sensitivity. But their exact role has been unclear.
“The outer hair cells’ function has been speculated about for a long time. We’ve known that they’re important for hearing sensitivity… It’s long been thought that they are serving as a mechanical amplifier”
–James Dewey, PhD, USC Caruso Dept of Otolaryngology-Head & Neck Surgery
With the new NIH grant, Dewey will expand his research on outer hair cells using a technique called optical coherence tomography (OCT). OCT uses lasers to take detailed 3D images of the inner ear structures in mice. This allows Dewey to see how the cells move and vibrate when exposed to sound, without invasive surgery.
Using Lasers to Explore the Inner Ear
“For the first time, we can start to put together a clearer picture of what’s happening in a living animal and not just in a dish,” Dewey said.
Earlier work by Dewey provided evidence that outer hair cells change length in response to sound. The new research will further characterize these movements. It will also examine how outer hair cell motions affect overall vibration of the inner ear. This could reveal how the cells amplify hearing.
Photo Credit: James Dewey. PhD; USC
The findings will increase basic knowledge of how outer hair cells enable sensitive hearing in mammals. In the future, this could guide therapies targeting these cells to treat hearing loss.
“We know that outer hair cell damage is actually one of the most common causes of hearing loss…especially age-related hearing loss. We know that they’re important, but we don’t know what we need to actually restore in order to ameliorate the hearing loss.”
While other researchers look at regenerating damaged outer hair cells, Dewey’s lab focuses on how the cells function mechanically.
“These hair cells, you’re born with them and you’re stuck with them. So if they die, you lose them; they don’t regenerate in mammals,” he explained. “Even if we can regenerate the cells, whether or not they’re working properly or they’re working in the way that we need them to, to restore hearing remains an open question.”
Source: Mollie Barnes, USC
