With treatment based on the genetic input into inner ear cells, children born with a genetic mutation causing deafness could see their lives dramatically improved.
- Scientists created a harmless synthetic virus and used it to deliver genetic material.
- The treated mice developed normal hearing, with almost the same sensitivity as healthy mice that do not have the mutation.
Deafness is the most common sensory disability on the planet. Indeed, according to the World Health Organization, about half a billion people suffer from hearing loss. Even more worryingly, this figure is expected to double over the next few decades. In almost half of the cases, it is due to a genetic mutation. But according to a new study published in the journal EMBO Molecular Medicine on December 22, researchers reportedly developed a life-changing therapy for children born with one of these terrible variants. The treatment is based on the genetic input into the cells of the inner ear.
In this study, scientists from Tel Aviv University (TAU) focused on genetic deafness caused by a mutation in the SYNE4 gene, “a rare deafness discovered by our lab several years ago in two Israeli families, and since then identified in Turkey and the UK as wellthey explain. Children who inherit the defective gene from both parents are born with normal hearing, but gradually lose their hearing during childhood. The mutation causes cell nuclei to mislocate to the hair cells inside the cochlea of the inner ear, which serve as receptors for sound waves and are essential for hearing. This defect leads to the degeneration and eventual death of hair cells.details Professor Karen Avraham of the Department of Human Molecular Genetics and Biochemistry at Sackler School of Medicine and Sagol School of Neuroscience at TAU.
Here, scientists have created a “harmless synthetic virus and used it to deliver genetic material – a normal version of the gene that is defective in both the mouse model and affected human families”, explains Shahar Taiber, one of Prof. Avraham’s students. They then injected it into the inner ear of mice with a genetic mutation for deafness shortly after birth, so that “enters the hair cells and releases its genetic load. By doing so, we repaired the defect in the hair cells and allowed them to mature and function normally.”, details Taiber.
“The extent of hearing restoration is impressive”
Results: “the treated mice developed normal hearing, with almost the same sensitivity as healthy mice that lack the mutation” enthuses Professor Jeffrey Holt of Boston Children’s Hospital and Harvard Medical School, who was involved in the work.
“This is an important study that shows that inner ear gene therapy can be effectively applied to a mouse model of SYNE4 deafness to save hearingcomments Professor Wade Chien, of the NIDCD / NIH inner ear gene therapy program and the Johns Hopkins School of Medicine, outside this research. The extent of hearing restoration is impressive. This study is part of a growing body of publications showing that gene therapy can be successfully applied to mouse models of inherited hearing loss, and it illustrates the enormous potential of gene therapy as a treatment for deafness.”, they conclude.
Currently, scientists are developing similar therapies for other mutations that cause deafness. Because nowadays, a hundred different genes are associated with hereditary deafness.
Sensorineural and conductive hearing loss
The latter belongs to the family of sensorineural hearing loss. In this case, the patient suffers from anomalies in the transformation of the sound signal into nerve impulses and in the interpretation of this signal by the brain. Besides the genetic cause, this deafness can be due to Ménière’s disease (increased pressure in the labyrinth), certain drugs toxic to the inner ear, exposure to loud noises, trauma or infection of the inner ear, to a cardiovascular problem, to damage to the auditory nerve, or, more rarely, to the auditory pathways of the brain.
A distinction is made between sensorineural deafness and conductive deafness. This comes from a problem of transmission of the sound signal in the outer ear (visible part of the ear) or middle (part located between the outer and inner ear). Its main causes are: a congenital malformation of the ear, a mechanical blockage, sequelae of trauma to the middle ear or degeneration of the ossicles of the middle ear (ostopongiosis).
In France, the overall level of deafness is calculated on the ear that hears the best. A distinction is made between people with mild (20 to 39 decibels of hearing loss), moderate (40 to 69 decibels of loss), severe (70 to 89 decibels of loss) and profound (more than 90 decibels of loss) deafness. , where the patient no longer hears speech at all. According to social security website, one child in a thousand is born profoundly deaf. At 3 years old, three out of 1000 children suffer from severe or profound deafness. Finally, more than 10% of the French population would be confronted with hearing loss or reduced hearing.
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