A groundbreaking study by a team of Israeli researchers has raised hopes of a treatment for what has until been thought of as permanent hearing loss.
Scientists from the Tel Aviv University (TAU) Gray Faculty of Medical and Health Sciences have identified a unique biological mechanism that could lead to the regeneration of hair cells in the inner ear.
Hearing loss is often caused by damage to these cells, which are crucial to hearing.
Humans are unable to replace them naturally when damaged, making hearing loss permanent, although artificial treatments – such as hearing aids – can be used to help offset the damage.
Now an Israeli team of experts, led by the dean of the faculty and Dumont Chair for Research of Hearing Disorders, Professor Karen Avraham, has uncovered a rare subset of supporting cells with regenerative potential that seem to act like a built-in backup system.
Researchers found that a small number of these supporting cells can change into new hair cells under the right conditions.
To trigger this, the team blocked a natural signalling system called the Notch pathway, which normally prevents these supporting cells from changing. Once that signal was switched off, the special "reserve" cells began transforming into new hair cells.
The researchers also found that these cells have unique genetic features that make them capable of responding to this trigger. Everyone appears to have these special cells, although some people may naturally have more of them than others.
The therapy to reverse hearing loss could involve an injection made in the inner ear by a surgeon. Even five years ago, Avraham said, “our discovery would not have been possible, because the technology used is new”.
The findings, which were published in the prestigious Science Advances journal, were spearheaded by Lama Khalaily, a TAU doctoral student, in collaboration with Prof. David Sprinzak of TAU’s Wise Faculty of Life Sciences; Shahar Kasirer from Sprinzak’s lab; Dr. Litao Tao of Creighton University in Omaha, Nebraska; and other researchers.
According to the team, the discovery represents a significant step in the field.
Avraham said: “Our study shows that even in tissues long considered incapable of regeneration, such as the cochlea of the inner ear, there is in fact a hidden regenerative capacity, though it is very limited and appears only in a rare subpopulation of cells.
"The major challenge now is to understand how this ability can be expanded and activated in additional cells.
“If we succeed in doing this, we may lay the foundation for the development of innovative biological treatments that restore hearing, rather than merely compensate for its loss.
“This is a first but significant step toward a deeper understanding of regeneration in the auditory system and in neural systems in general.”
She suggested that in the future, one could test every child at birth, therefore predicting the problem and proactive gene therapy could be performed.
“In science, nothing is impossible. We began working on hair-cell regeneration a decade ago, but it’s still a very young field,” she said.
Avraham said she is inundated with emails from individuals and families who are looking for the latest advancements in the field.
“I want to help, but I’m careful not to raise their expectations, because it’s still basic research,” she said. “But nobody else has succeeded doing what we have accomplished.”
The biggest obstacle between this discovery and actual treatment on people are regulation and cost. Deafness, she said, involves many different genes, so diseases are rare and pharmaceutical companies may lack motivation to invest in them.
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