A new study from the University of Tel Aviv (TAU) represents an innovative treatment for deafness, based on the introduction of genetic material into the cells of the inner ear. Genetic material “replaces” a genetic defect and allows cells to continue to function normally.
The scientists were able to prevent a gradual deterioration in hearing in mice that had a genetic deafness mutation. They believe that this new therapy could lead to advances in the treatment of children born with various mutations that eventually cause deafness.
The study was led by Professor Karen Avraham of the Department of Human Molecular Genetics and Biochemistry at TAU’s Sackler School of Medicine and the Sagol School of Neuroscience. The paper was published in EMBO Molecular Medicine December 22, 2020
Deafness is the most common sensory disability in the world. According to the World Health Organization, there are about half a billion people with hearing impairments worldwide today, and that number is expected to double in the coming decades. Every 200 children are born with a hearing impairment, and every 1000 is deaf. In about half of these cases, deafness is caused by a genetic mutation. There are currently about 100 different genes associated with hereditary deafness.
“In this study, we focused on genetic deafness caused by a mutation in the SYNE4 gene – a rare deafness that our lab discovered a few years ago in two Israeli families and has since been identified in Turkey and the UK,” Professor Avraham reports. “Children who inherit a defective gene from both parents are born with normal hearing but gradually lose hearing during childhood. The mutation causes mislocation of cell nuclei in hair cells within the cochlea of the inner ear, which serve as sound wave receptors and necessary for hearing. This deficiency leads to hearing. to the degeneration and eventual death of hair cells. “
“We implemented an innovative gene therapy technology: we created a harmless synthetic virus and used it to deliver genetic material – a normal version of a gene that is defective in both mouse models and affected human families,” said Shahar Taiber, a professor at Professor Abraham’s Combined Pathway. “We injected the virus into the inner ear of the mice, so that it entered the hair cells and released its genetic burden. This fixed the defect in the hair cells and allowed them to mature and function normally.”
The treatment was applied shortly after birth, and the mice’s hearing was then monitored using physiological and behavioral tests. “The findings are the most promising,” says Professor Jeffrey Holt of Boston Children’s Hospital and Harvard Medical School, a collaborator in the study. “In treated mice, normal hearing developed, with a sensitivity almost identical to that of healthy mice without the mutation.”
Scientists are now developing similar therapies for other mutations that cause deafness.
“This is important research showing that inner ear gene therapy can be effectively applied to the SYNE4 mouse model of deafness to save hearing,” says prof. Dr. Wade Chien of the NIDCD / NIH Ear Gene Therapy Program and Johns Hopkins School of Medicine, who was not included in the study. “The magnitude of hearing recovery is impressive. This study is part of a growing literature showing that gene therapy can be successfully applied to mouse models of hereditary hearing loss and illustrates the enormous potential of gene therapy as a treatment for deafness.”
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