Researchers are actively tackling the possibility of implementing cochlear hair cell regeneration. Some species have the ability to regenerate inner hair cells, protecting these creatures’ ability to hear. A new and exciting study, conducted by Echeverri (2022) on the use of Zebrafishing in enhancing hearing regeneration, has been published by Cell Genomics.
The Role of Hair Cells in the Inner Ear
Before diving into the study, let’s address the role of hair cells in the ear. Hidden deep in the skull is the snail-shaped, bony cochlea. The cochlea is often considered the powerhouse of hearing. It is lined with specialized hair cells that transmit sound to the brain. These seemingly tiny structures have the vital job of comprehending the spectrum of low to high pitch sounds. When these hair cells get damaged, this results in irreversible hearing loss. While hearing aids and cochlear implants work to overcome hair cell damage, the sound is not quite the same as natural sound received by intact, functioning hair cells.
Why the Zebrafish Model?
In research, the best animal model used is one that responds similarly to the human on the cellular level. On the outside, a Zebrafish doesn’t look like a human. However, If you look more closely, there is a likeness to the human inner ear. Both the Zebrafish and human hair cells have similar gene regeneration. As one could imagine, it would be difficult to study tiny fish ears. However, found on the surface of the Zebrafish, there is an organ where hair cells are found clustered inside. This makes studying regeneration of hair cells in the Zebrafish more popular due to its accessibility. It only takes 48 hours for the hair cells to be completely restored in both structure and function.
Both the Zebrafish and human hair cells have similar gene regeneration.
Results: Zebrafish and Regeneration of Hair Cells
In this study, Echeverri found that the Sox2, a gene that works to enhance the genetic sequence, works similarly in both the Zebrafish and adult human. When the researchers stopped part of this gene from functioning properly, the regeneration capability was lost. This study shows that mammals, such as humans, could have lost their regeneration capacity due to the injury in the Sox2 gene. However, more research is needed to confirm and correlate the data. You may also be wondering what exactly causes hearing damage. The study presents four factors that are known to cause hearing damage: Traumatic injury, infection, loud noise, and age.
Other researchers such as Corwin & Oberholtzer have added in the same variables of hearing loss, such as infection and loud noise, to destroy the Zebrafish hair cells. Unlike placental mammals, the Zebrafish is able to recreate the inner hair cells and supporting cells. This study found that the Sox2 gene may have been partially or fully inhibited in the human ear, stopping potential regeneration. This discovery is exciting as researchers will hopefully be to able to one day induce cochlea hair cell regeneration in humans.
Abigail Russell is a second-year medical school student at Indiana University School of Medicine. She is a bilateral hearing technology user, utilizing both a Phonak Naída and Cochlear Implant. Ever since she was diagnosed as a little girl, she has been an advocate for those with hearing loss. She loves spending time with people, enjoys coffee, and cuddles with her puppy, Rosie!
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