Gene therapy breakthrough restores hearing ability in deaf children

Several children with genetic hearing disabilities were able to hear after receiving gene therapy, marking a landmark development towards the restoration of hearing for individuals who cannot hear due to hearing disabilities acquired from their parents or their ancestors.

Genetic hearing loss accounts for 50 per cent of all cases of hearing loss. The rest of the hearing losses occur due to causes such as infection or physical trauma. The breakthrough achieved by scientists in China was first reported on November 1 at a meeting in Belgium, the Science magazine reported.

A total of four children in China could very well be the first individuals in the world to have their natural hearing pathway restored through gene therapy.

The feat is remarkable because until now, no drug of any kind has ever been able to improve hearing, MIT Technology Review reported.

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"We were careful, and a little bit nervous, because it was the first in the world," Yilai Shu, a surgeon and scientist at Fudan University in Shanghai who has been leading the experiment, was quoted as saying by the publication.

The treatments began last December. According to Shu, one child, who had never spoken, has started to say "baba" and "mama" after the treatment, an emotive moment for the parents.

"Before the treatment, if you put them in a movie theater with the loudest sound, they wouldn’t hear it," Zheng-Yi Chen, an associate professor at Mass Eye and Ear, a Harvard-affiliated hospital in Boston, who helped design and plan the study told MIT Technology review.

"Now they can hear close to normal speech, and one can hear a whisper."

The process to restore hearing: How was this achieved?

The children who were cured of their hearing disabilities were born that way due to the presence of two defective copies of the gene for a protein that helps the inner ear’s hair cells transmit sound to the brain.

Researchers injected harmless viruses carrying DNA for a working copy of the otoferlin gene into the children’s ears.

Four of five patients treated now have some hearing, the MIT Technology Review reported.

A video shared by the MIT Technology Review showed a 6-year-old child chatting with her mother after her cochlear implant was removed.

Earlier, the New York-headquartered pharmaceutical company Regeneron had claimed similar success for the first patient treated with its otoferlin gene therapy.

Notably, the Otoferlin-related hearing disability is very rare, accounting for only 1 to 3 per cent of cases of inherited deafness.However, the results offer hope for treating other genetic forms of hearing loss.