Israeli scientists at Tel Aviv University have developed a gene therapy for deafness, a breakthrough that may help in the treatment of children with hearing loss.
The innovative therapy, replacing defective genes with healthy genes, may prevent deafness in children born with genetic mutations that cause hearing loss.
The scientists developed a treatment for genetic deafness caused by a specific mutation identified for the first time in Israeli families, and then in the United Kingdom and Turkey.
The therapy was initially tested by injecting a healthy gene into the ears of mice with a mutation for deafness, replacing a defective gene in cells that are crucial for hearing. Newborn mice that received this treatment developed with completely normal hearing.
The scientists believe that their findings can serve as a basis for developing similar treatments for mutations in other genes as well.
The scientists were able to prevent the gradual deterioration of hearing in mice with a genetic mutation for deafness. They maintain that this novel therapy could lead to a breakthrough in treating children born with various mutations that eventually cause deafness.
The study was led by Prof. Karen Avraham and Shahar Taiber, a student in the combined MD-PhD track, from the Department of Human Molecular Genetics and Biochemistry at the Sackler Faculty of Medicine, and the Sagol School of Neuroscience, and Prof. Jeffrey Holt from Boston Children’s Hospital and Harvard Medical School.
Deafness is the most common sensory disability worldwide. According to the World Health Organization, there are about half a billion people with hearing loss around the world today, and this figure is expected to double in the coming decades. One in every 200 children is born with a hearing impairment, and one in every 1,000 is born 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.
Prof. Avraham explained that “in this study we focused on genetic deafness caused by a mutation in the gene SYNE4 – a rare deafness discovered by our lab several years ago in two Israeli families, and since then identified in Turkey and the UK as well.”
Children inheriting the defective gene from both parents are born with normal hearing, but gradually lose their hearing during childhood. This happens because the mutation causes mislocalization of cell nuclei in the hair cells inside the cochlea of the inner ear, which serve as soundwave receptors and are thus essential for hearing. This defect leads to the degeneration and eventual death of hair cells.
Shahar Taiber said that researchers “implemented an innovative gene therapy technology: we 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 the affected human families.”
The team injected the virus into the inner ear of the mice so that it entered the hair cells and released its genetic payload. By so, they repaired the defect in the hair cells and enabled them to mature and function normally.
The treatment was administered soon after birth and the mice’s hearing was then monitored using both physiological and behavioral tests.
Holt noted that “the findings are most promising: Treated mice developed normal hearing, with sensitivity almost identical to that of healthy mice who do not have the mutation.”
Following the successful study, the scientists are currently developing similar therapies for other mutations that cause deafness.
Prof. Wade Chien, MD, from the NIDCD/NIH Inner Ear Gene Therapy Program and Johns Hopkins School of Medicine, said this study “is a part of a growing body of literature showing that gene therapy can be successfully applied to mouse models of hereditary hearing loss, and it illustrates the enormous potential of gene therapy as a treatment for deafness.”