Hearing loss is something that affect tens of millions of Americans. Usually people notice those changes as they get older but the damage can be done years before that through the use of some prescription drugs or exposure to loud noise (I knew I shouldn’t have sat in the 6th row of that Led Zeppelin concert!)
Now researchers at the University of Southern California (USC) have identified the mechanism that appears to stop cells that are crucial to hearing from regenerating.
In a news release Dr. Neil Segil says this could, in theory, help reverse some hearing loss. “Permanent hearing loss affects more than 60 percent of the population that reaches retirement age. Our study suggests new gene engineering approaches that could be used to channel some of the same regenerative capability present in embryonic inner ear cells.”
The inner ear has two types of cells that are crucial for hearing; “hair cells” are sensory receptors and these help the brain detect sounds, and support cells that play, as the name implies, an important structural and supporting role for the hair cells.
In people, once the hair cells are damaged that’s it, you can’t repair or replace them and the resulting hearing loss is permanent. But mice, in the first few days of life, have ability to turn some of their support cells into hair cells, thus repairing any damage. So Segil and the team set out to identify how mice were able to do that and see if those lessons could be applied to people.
They identified specific proteins that played a key role in turning genes on and off, regulating if and when the support cells could turn into hair cells. They found that one molecule, H3K4mel, was particularly important in activating the correct genetic changes need to turn the support cells into hair cells. But in mice, levels of H3K4mel disappeared quickly after birth, so the team found a drug that helped preserve the molecule, meaning the support cells retained the ability to turn into hair cells.
Now, obviously because this was just done in mice there’s a lot more work that needs to be done to see if it can also work in people, but Segil says it’s certainly an encouraging and intriguing start.
“Our study raises the possibility of using therapeutic drugs, gene editing, or other strategies to make epigenetic modifications that tap into the latent regenerative capacity of inner ear cells as a way to restore hearing. Similar epigenetic modifications may also prove useful in other non-regenerating tissues, such as the retina, kidney, lung, and heart.”
The study is published in the journal Developmental Cell
CIRM has funded several projects targeting hearing loss. You can find them here.