Medical

Atomic-level maps of fine ear filaments shine a light on hearing loss

Atomic-level maps of fine ear ...
Scientists have gained a new, atomic-level understanding of ear filaments that are key to turning vibrations into signals that we interpret as sound
Scientists have gained a new, atomic-level understanding of ear filaments that are key to turning vibrations into signals that we interpret as sound
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Scientists have gained a new, atomic-level understanding of ear filaments that are key to turning vibrations into signals that we interpret as sound
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Scientists have gained a new, atomic-level understanding of ear filaments that are key to turning vibrations into signals that we interpret as sound

Much mystery surrounds the biological processes behind the human sense of hearing, but with cutting-edge scientific tools researchers are starting to unravel its secrets. A team at Ohio State University has now produced the first ever atomic-level mapping of tiny filaments inside our ears, offering unprecedented insights into a key mechanism of the organ and how hearing loss can result when things go awry.

Last month, we looked at research from a group of US scientists who pinpointed a single protein that can determine whether a type of embryonic hair cell matures into healthy sensory cells that line the inner ear. Known as hair cells, these play an important role in our sense of hearing, and the discovery opened up some promising new pathways when it comes to regenerative treatments for hearing loss.

The new study, from Ohio State University researchers, builds on this in a way. It focuses on microscopic hairs that sit on top of these hair cells inside the inner ear – more specifically, very fine filaments attached to the top of those microscopic hairs called tip links. As sound vibrations make their way through the ear, these tip links stretch and open up small channels for positively charged ions to carry electrical signals between the ear and the brain, enabling us to hear. It is a similar process that enables us to balance.

“If you don’t have the tip link, you can’t hear, and you can’t balance,” says lead author of the study Marcos Sotomayor. “They are essential.”

Scientists have previously produced low-resolution images of tip links, and know that they are made of a pair of proteins called cadherin-23 and protocadherin-15, which are linked to inherited deafness. Now, the Ohio State University team has isolated parts of these proteins and used X-ray crystallography to produce maps of tip link structures at an atomic level.

“Now, we can see down to the atom, and we can create physics-based movies of how these tip links respond to sound-generated forces,” Sotomayor says. “That can tell us a great deal more about how these work and what happens when they stop working.”

One of the key insights gleaned from these high-resolution images of tip links was a new understanding of how the cadherin-23 and protocadherin-15 proteins interact. The scientists learned that they forge a type of connection they describe as a “molecular handshake,” which is key to the filaments' strength and considered essential for hearing and balance.

The team was also able to carry out simulations of the complex dynamics of tip links as sound vibrations wash over them, observing the way they stretch and deform as they open up the ion channels. Ultimately, these new insights could help scientists and doctors learn more about why tip links fail, and investigate ways to prevent that from happening.

“The structures also reveal tip-link sites that are mutated in inherited deafness,” Sotomayor says. “So we can try to understand what is happening with the tip links when you have these sites modified by mutations, not only by looking at the static structures but also at the simulated trajectories of tip links responding to sound.”

The research was published in the journal Proceedings of the National Academy of Sciences.

Source: Ohio State University

5 comments
Andy Aitken
It would be interesting one day, if science could replace the hair cells in the ear. I have tinnitus related hearing loss, which I believe was caused by my ping golf driver. Sometimes its safer to be at work...
1stClassOPP
I woke up one day with sudden hearing loss in my left ear, years ago. I suspect it was caused by a radar set Used to check vehicle speed Hanging out the left rear window of a police car. So, after many hearing tests the technicians determined nerve damage. Some suggest that the cochleae is flooded,in technical terms, but no remedy has ever been offered. Hearing aids will no work to fix this problem, so I’m excited more research is being done on the ear. LookIng forward to potential fix.
Signguy
I awoke one day to have no hearing below 120 hz. in one ear only! No injury or reason. Eventually came back! Weird to have a specific tone "sing" in my ear, then after a minute just goes away...happens a few times a year.
Michele Johnson
I spent 8 days in the hospital with Covid-19. When I was discharged I was deaf in my right ear. Some say it could be from IV Antibiotics. Others, the codeine in my cough syrup. Is this article part of a study that could provide a solution to my deafness??? Help! I don't want to be permanently deaf in one ear!!!!
Eggster
A few years ago, I experienced acute hearing loss in my left ear. Like Signguy, a hearing test revealed that I couldn't hear anything under 120 decibels. It all started with what appeared to be water in the ear following a shower - my hearing was muffled. When the symptoms remained the next day, I called my provider and they squeezed in for an appointment to see my NP that afternoon. After checking my ear and finding no signs of a conventional infection, she referred me to an ENT the next morning ... after trying to get me in the same day. (An admirable sense of urgency!)

The ENT diagnosed it as a viral infection of the cochlea. This can only be determined by a process of elimination as the cochlea is impossible to observe directly. In a nutshell, the infection causes inflammation of the tissue inside the cochlea which in turn causes the hairs mentioned in the article to press against each other. I was prescribed prednisolone and recovered over the next week.

That's my experience. Now, here's my PSA: From the time that the symptoms begin, YOU HAVE 72 HOURS TO BEGIN TREATMENT, after that time the hearing loss begins to become permanent, so contact your provider and make sure you get seen ASAP.