New research that appeared in the Proceedings of the National Academy of Sciences has made clear the role of a protein in the inner ear as well as outer hair cells in the hearing of high-frequency sounds.
Hearing Loss
The cochlea, a spiral structure in the inner ear, plays a key role in hearing and auditory transduction. It features two major types of hair cells: inner hair cells and outer hair cells. The latter regulates the ear’s sensitivity to sound.
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Scientists believe that the outer hair cells magnify sounds from the environment. They are sometimes referred to as the cochlear amplifier as a result of this.
Humans and other mammals depend on outer hair cells to hear high-frequency sounds. However, these cells are the most susceptible of all inner-ear cells. Damage to outer hair cells often results in hearing loss in that they cannot be regenerated.
In this study, researchers discovered the critical role of a protein in the inner ear known as prestin (SLC26A5) for the hearing of high-frequency sounds. This protein is so named – after the musical tempo “presto” – because of its fast motor function.
According to scientists, prestin regulates the elongations and contractions of outer hair cells for cochlear sound amplification.
The study
To make their findings, researchers from Northwestern Medicine assessed the hearing of mice having an abnormal genetic variant of prestin. This malformed version was shown in previous research to have a link to deafness in human beings.
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The team found that the animals with abnormal prestin had outer hair cells with slowed movement. As a result, the mice showed reduced sensitivity to higher-frequency sounds.
“We generated this mouse model expressing the human mutation which slowed the motor function of prestin and we found that hearing got worse towards higher frequencies,” said Kazuaki Homma, Ph.D., the study’s senior author. “This is consistent with the idea that prestin’s motor function is important for high-frequency hearing.”
When the researchers introduced an extra functional genetic prestin variant that preserves its speed, they were able to restore hearing in mice fully.
Relevance and future work
This Northwestern Medicine study adds to the knowledge of the role of prestin and how cochlear amplification occurs.
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Given that outer hair cells are fully gone and cannot be regenerated when lost, these researchers hope to further explore how prestin can help to keep these cells. The aim is to find a way to hold off the loss of outer hair cells for as much time as possible and so guard against hearing loss.
“It is important to have these cells around if we want to target them for any therapeutics in the future,” explained Homma.
References
Prestin’s fast motor kinetics is essential for mammalian cochlear amplification
