By Yishane Lee
We have the ability to hear, thanks to the sensitive hair cells located in our ears. They are called hair cells because of their hair-like shape, long and thin (resembling the hairs on your head yet having nothing to do with them). When these hair cells die or are damaged, it is permanent. And so is the resulting loss of hearing. Unlike in other species—such as birds, fish, and amphibians—in mammals including humans, once these cells die, they don’t grow back or repair themselves, which makes it even more critical to keep them alive.
Supporting cells, as their name suggests, support hair cells both structurally and nutritionally. But a new study of supporting cells in the inner ears of mice reveals yet another role—one that is hugely important for researchers working to restore hearing in mammals.
Writing in July in an online edition of the Journal of Clinical Investigation, scientists at the National Institute on Deafness and Other Communication Disorders (NIDCD), found that supporting cells can actually actively help repair damaged sensory hair cells.
Supporting cells and a chemical they produce called heat shock protein 70 (HSP70) appear to play a critical role in protecting damaged hair cells from death in the ears of mice. Senior study author Lisa Cunningham, Ph.D., said, “Our study indicates that when the inner ear is under stress, the cell that responds by generating protective proteins is not a hair cell, but a supporting cell.” Cunningham and her team are collaborating with a clinical team at the NIDCD to design a clinical trial. It will look at ways to induce the production of HSP70 in the inner ear.
Further, our Hearing Restoration Project consortium members Albert Edge, Ph.D. of Harvard Medical School, Stefan Heller, Ph.D. of Stanford University, and Elizabeth Oesterle, Ph.D. of University of Washington are trying to figure out what happens to supporting cells after hair cells die or are damaged. Their project, “Supporting Cell Fate Mapping,” has so far found that some promising news regarding supporting cells and their function. In “Making a Map,” an article in the Fall issue of Hearing Health, Dr. Oesterle writes:
“After some severe insults (damage), the nonsensory supporting cells in the [auditory] epithelium [the organ of Corti] can retain some normal cellular identity for long periods of time. This is encouraging because in non-mammals it is the supporting cells that give rise to new replacement hair cells after hair cells are lost. After various severe insults, our data suggest that the supporting cells die and neighboring cells—cells that are normally abutting the sensory epithelium—move in.”
Both recent research results show that while we still have more to learn about the roles of supporting cells, their support they provide may be crucial to the search for a cure for hearing loss and tinnitus.