▎ WuXi AppTec content team editor
Aging, noise, and certain cancer treatment drugs and antibiotics can cause irreversible hearing loss. If scientists can reprogram existing cells, they can also re-develop into hearing-critical outer and inner ear sensory cells after death, promising to restore hearing.
In a recent issue in the journal Nature, scientists at Northwestern University discovered a single master gene that can program ear hair cells into outer or inner hair cells, respectively, overcoming an important obstacle that hinders the development of these cells to restore hearing.
Lead author, Professor Jaime García-A overos of Northwestern University, said: "We have found for the first time a clear cell conversion mechanism that can be switched from one cell type to another. We overcame a major obstacle by providing a previously unavailable tool to make inner or outer hair cells. ”
According to the Centers for Disease Control and Prevention, approximately 8.5 percent of people aged 55 to 64 years in the United States have disabling hearing loss. This increases to nearly 25% in people aged 65 to 74 years, and to 50% at ages 75 and older.
Previously, scientists could artificially create ear hair cells, but they did not differentiate into inner or outer hair cells that have different functions during hearing generation. The new findings are an important step toward mining these specific cells.
Death of external hair cells produced by the cochlea is usually the cause of deafness and hearing loss. The outer hair cells expand and contract in response to the pressure of sound waves and amplify the sound for the inner hair cells. Internal cells transmit these vibrations to neurons, producing the sounds we hear.
"It's like a ballet," Professor Jaime García-A overos said in awe as he described the coordinated movement of the inner and outer hair cells, "the outer cells crouch down and jump up, lifting the inner cells further into the ear." The ear is a beautiful organ. No other organ in mammals can locate cells so precisely, it has super high measurement accuracy, otherwise hearing would not occur. ”
They found that the main gene switch that programmed the ear hair cells was TBX2. When the TBX2 gene is expressed, the cell becomes an inner hair cell; when the TBX2 gene is blocked, the cell becomes an external hair cell. Producing any of these cells requires a mixture of genes. To create cochlear hair cells from non-hairy cells, the two genes ATOH1 and GF1 are required, and then the TBX2 gene is turned on or off to produce the desired inner or outer hair cells.
Ectopic expression of TBX2 genes in outer hair cells causes them to be converted into inner hair cells (Image source: Reference[2])
The researchers' goal is to reprogram non-hairy cells, which are support cells, arrange them between hair cells, and provide them with structural support, which eventually forms outer or inner hair cells.
While still in the experimental phase, researchers have figured out how to make specific inner or outer hair cells and found what causes outer hair cells are more likely to die and cause deafness. These new breakthroughs will bring new hope for hearing restoration to those elderly who face hearing loss.
Resources:
[1] New tool to create hearing cells lost in aging. Retrieved May 4, 2022 from https://www.eurekalert.org/news-releases/951729
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