Researchers use genetic engineering to give hearing to deaf kids

Five children of preschool age, who suffered from congenital deafness due to a hereditary disease, were able to hear normally without a hearing aid thanks to genetic engineering and began to utter their first words.

This revolutionary method of treating hereditary deafness, which was developed by geneticists from Harvard Medical School and Fudan University (China), was tested during clinical experiments, the results of which were published in the journal Science Advances.

Initially, there were six experimental operations, but in one case the experiment was not completed successfully. Researchers have several answers as to why this therapy was ineffective in that case, but it is possible that the innovative methodology did not work and it is necessary to repeat it, BBC reported.

The authors of this work assure that their method of therapy may be approved in the United States in the coming years, after which doctors will have the right to immediately send such children for treatment.

Congenital deafness can be the result of about 150 different mutations, but in this case it is a genetic "disruption" that disrupts the nerve connection between the inner ear and the brain. Scientists know this mutation as DFNB9. As a result of that genetic disruption, the body loses the ability to produce a protein that is needed to transmit nerve impulses from auditory receptors to the brain, where they are perceived as sounds. This disruption was discovered decades ago. But during all that time, such children could only be helped with prosthetics; that is, by placing an implant in the child's head. But even that did not completely solve the problem. Children with an "artificial ear" cannot distinguish tone and catch intonation. Therefore, their listening abilities are quite limited. For example, they are not able to perceive music as normal. Since this disruption is caused by only one long-standing and well-studied mutation, whereas nerve cells are not damaged, the DFNB9 has long been considered an obvious “target” for innovative therapies.

In order to deliver a healthy copy of the damaged gene to the cell, it is "inserted" into the genome of the neutralized virus.

How this relatively new, but already widespread technology works, the BBC had explained in general terms a year or two ago, when its inventors—or rather, its women inventors—were awarded the Nobel Prize.

Having “loaded” the virus with a useful gene, the scientists injected the resulting mixture into each child—and with the help of an injection in the inner ear. Once inside the cell, the virus actually repairs the damaged part of the DNA, replacing the "defective" copy with a normal, healthy gene. And it begins to reproduce normally during each cell division. As a result, the production of the necessary protein begins; and along with it, the transmission of nerve signals to the brain is normalized. Hearing gradually improves.

After a few months, the three children who underwent the aforesaid operation began to respond to speech, and the other two even distinguished it from the sounds of a noisy room, which enabled them to talk on the phone. Their hearing did not return immediately, but improved gradually—and almost imperceptibly.

But the authors of this study note that all treated children began to show obvious results of therapy even after the first test, which was conducted four weeks after the injection. The researchers had learned about the success of this treatment from the parents who came with tears in their eyes to tell the doctors that their child heard them for the first time.

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