Have you noticed that you are not able to hear as well as you did a few years ago? Most people will not notice that they are indeed losing their hearing since losing hearing is a process and will happen gradually. The people that will be subjected to hearing loss the most are the elderly. One in every three adults over the age of sixty-five suffers from hearing loss, and as we age, some of us will lose our hearing partially as well.
Although the loss of hearing with age has become normal in life, it does not have to be anymore.
Before explaining how that is possible, we need to understand the basics of hearing first. The visible outer part of the ears called the pinna, collects sound waves and directs them into the ear canal. The ear canal directs the sound waves into the eardrum; the eardrum vibrates as it sends those vibrations to the ossicles. The help of the smallest bones in the human body — ossicles — amplifies the sound energy with a lever action. The reason for that is the ear canal then transfers the vibrations to the oval window, and the oval window will lead it to the cochlea — a fluid-filled, snail-shaped structure in the inner ear.
The ossicles transfer the sound from air to the liquid medium in the cochlea which contains the basilar membrane. The ripples in the fluid inside the cochlea travel through the basilar membrane, which works as a base for key hearing structures and ergo named so. The sensory receptor cells in the inner ear — hair cells — are located on the basilar membrane and move up and down as the waves pass through them. The movement of the hair cells makes the stereocilia — protrusions on sensory cells that are used in hearing and balance — on top of the hair cells create bends. This, in return, causes the tips of the stereocilia to open and allow chemicals to enter to create electrical signals. And with those signals being transmitted to the brain, we can recognize the sound and noise around us.
Most hearing loss happens because of the damage to the sensory hair cells in the ear, either caused by aging, certain drugs or antibiotics, noise, etc. And the pressing issue with that is that the hair cells do not have the ability to regenerate. Thus, damage in those cells will cause hearing loss, which has no cure even though there are a variety of treatments.
Scientists are able to produce artificial hair cells. However, they are not able to differentiate into an inner or outer cell and create specific cells. Because the inner and outer cells have distinct roles, scientists have been facing an ordeal. While outer hair cells deal with the amplification of the vibrations, inner hair cells are the ones transmitting signals to the brain. In addition to that, most hearing loss occurs because of the death of outer hair cells.
Recently, Northwestern Medicine scientists have discovered a single master gene that differentiates and programs hair cells into either outer or inner hair cells. The finding is able to switch cells to make either inner hair cells or outer hair cells. Creating a significant breakthrough in overcoming the hurdles means curing hearing loss and being one step closer to finding a solution to hearing loss.
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“Inner and Outer Hair Cells.” Baylor College of Medicine, https://www.bcm.edu/healthcare/specialties/ear-nose-and-throat-otolaryngology/for-patients/how-ear-works/inner-and-outer-hair-cells.
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