Scientists from Uppsala University in Sweden are studying crocodile ears in search of new treatments for human sensorineural deafness.
Crocodiles are known for their acute hearing and ability to restore it. However, the mechanism by which they do this has remained a mystery.
According to the World Health Organization, over 1.2 billion people worldwide suffer from hearing impairments. Hearing restoration methods are limited, and in cases of sensorineural deafness or hearing loss, only two options are available: wearing a hearing aid or implanting a device that replaces the cochlea of the inner ear.
One of the main causes of deafness in humans is the deterioration of receptors, which do not regenerate in humans but have this ability in some animals.
Scientists became interested in crocodiles, which can live for over 70 years and maintain good hearing throughout their lives. Their hearing functions both on land and underwater: receptors respond to the surrounding temperature and adjust sensitivity to sounds depending on the situation.
Swedish researchers analyzed tissue samples from Cuban crocodiles and the African slender-snouted crocodile, which is one of the smallest representatives of its species.
Using an electron microscope and molecular methods, the scientists discovered small cellular particles in the inner ear resembling exosomes—microscopic extracellular vesicles. In crocodiles, they form alveoli that help the cilia of hair cells bend. Additionally, exosomes release enzymes capable of breaking down and restoring the membrane that cilia rub against when capturing sound vibrations.
The authors of the study suggest that this feature makes crocodile hearing particularly acute and regulates sensitivity in various environments, as well as participates in the process of inner ear restoration.
“New hair cells in crocodiles are formed as a result of the activation of supporting cells. According to our hypothesis, this process is triggered by efferent nerves that transmit impulses from the brain,” says Helge Rask-Andersen, a professor of experimental zoology at Uppsala University.
Although scientists have not yet uncovered all the details, they hope to soon reveal the mechanism of hair cell regeneration in reptiles.
This knowledge from the world of crocodiles could have a significant impact on millions of people with hearing impairments, reports Phys.org.
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