Hearing loss is a disability that is more common than one might believe and has an immense impact on the way the sufferer lives and experiences the world. Approximately two to three out of every one thousand children are born with a detectable level of hearing loss in the United States, and roughly fifteen percent of adults aged eighteen or older report experiencing difficulties regarding hearing. Based on standard testing, one in eight Americans over the age of 11 has a loss of hearing in both ears. Problems with hearing are incredibly common and they can be quite difficult to deal with. A simple conversation can be a harsh experience because a hard of hearing individual has trouble listening to the other speaker. Students may miss out on important information because they could not hear it in class. These are just some examples of the issues that arise due to hearing loss that show why finding ways to improve hearing in hard of hearing individuals is important.
Dr. Yu presented his paper on the role of hepsin in regards to hearing in which he and his collaborators tested the effects varying amounts and types of hepsin had on the tectorial membrane and the hearing threshold of mice. Dr. Yu explained that the tectorial membrane sits above bundles that contain the hair cells responsible for hearing. When the hair cells vibrate, they shift in the tectorial membrane. Dr. Yu and his collaborators found that hepsin deficiency led to a deformed tectorial membrane that contained gaps and was separated from the spiral limbus. These deformations caused the mice to have a worse hearing threshold than the mice that had hepsin. The researchers theorized that the presence of hepsin early in cochlear development was crucial for the proper morphogenesis of the tectorial membrane, and they showed that the addition of human hepsin to mice could improve hearing. This study demonstrated a potential treatment for hearing loss that could improve hearing ability, but it does not directly address one of the biggest concerns regarding hearing loss: cochlear hair cells. Although the tectorial membrane is connected to the hair cells, the hair cells themselves become lost over time and do not regenerate. Furthermore, the study explored the effects of hepsin loss on mice that were genetically designed to express more or less of the protein, meaning they experienced cochlear development with the desired hepsin levels. As such, potential treatments on adults may not be as effective because the patient would already have experienced cochlear development.
In 2023, a group of Harvard researchers expressed the Myc and Notch1 genes in adult mice through an injection in the middle ear. This supported the proliferation of cells that surrounded inner ear hair cells, causing the inner ear of the mouse to “reprogram.” This experiment could potentially lead to more research focused on regeneration of hair cells to improve hearing, helping to address the issue of hair cell loss. Furthermore, the fact that regeneration is possible could be useful when combined with the findings of Dr. Yu’s study, as perhaps exposure of the inner ear to hepsin combined with the activation of Myc and Notch1 could lead to greater improvements in tectorial membrane deformations, as the cells may experience developmental conditions again.
These two studies are examples of promising research into treatments for hearing loss that could help improve the lives of many people throughout the world.
References:
"Restoring Hearing through Cell Reprograming and Regeneration." American Academy of Audiology, August 29, 2023. https://www.audiology.org/restoring-hearing-through-cell-reprogramming-and-regeneration.
"Quick Statistics About Hearing, Balance, & Dizziness." National Institute on Deafness and Other Communication Disorders, September 20, 2024. https://www.nidcd.nih.gov/health/statistics/quick-statistics-hearing.
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