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Scientists say they've successfully reversed hearing loss in mice, suggesting that certain forms of deafness caused by faulty genetic activity could not only be avoided, but outright reversed in humans, too.

As detailed in a study published in the journal Proceedings of the National Academy of Sciences, the researchers were able to restore the hearing of some mice in the low to mid-frequency ranges to near normal levels.

"Degenerative diseases such as progressive hearing loss are often believed to be irreversible, but we have shown that at least one type of inner ear dysfunction can be reversed," said study author Karen Steel, a professor of sensory function at King's College London, in a statement.

Most treatments for hearing loss such as hearing aids and cochlear implants, the researchers said, do not actually restore hearing or prevent it from worsening.

"Seeing the once-deaf mice respond to sounds after treatment was truly thrilling," said study lead author Elisa Martelletti, a professor at King's College, in the statement. "It was a pivotal moment, demonstrating the tangible potential to reverse hearing loss caused by defective genes."

The researchers made their breakthrough by focusing on a gene called Spns2. In the study, mice bred with defective Spns2 genes showed rapidly worsening hearing loss, implicating its role in the condition.

Using a specialized enzyme, the researchers essentially reactivated these dud genes in the mice at different ages, and then evaluated the rodents' hearing using what's known as an auditory brainstem response test.

Young mice, they found, had their hearing loss almost completely reversed once the gene was activated. However, the older a mouse was when it received the treatment, the less hearing it regained. And, past a certain age, the treatment was not effective at restoring hearing above 18 kHz — a pretty high frequency, to be fair.

Furthermore, the researchers found that by activating the Spns2 gene early on, the treatment also protected the cells of sensory hairs — which are essential for hearing — from future degeneration. In effect: a true and long-lasting reversal, that crucially must be administered at as young an age as possible for the best results.

It's worth noting, however, that this treatment was only effective at reversing hearing loss caused by this form of reduced gene activity, but the researchers believe their genetic approach will prove useful at reversing other diseases, not just deafness.

More on hearing: Scientists May Have Figured Out How to Regenerate Lost Hearing

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