Currently, around half a billion people suffer from hearing loss around the world. In about half of these cases, genetic mutations of one or more of around 100 different genes are thought to be the cause. Gene therapies thus hold obvious potential as a cure. And now, researchers from Tel Aviv University in Israel have successfully completed animal studies on a novel genetic-based treatment for the condition.
For the study, the researchers focused on genetic deafness caused by a mutation of the gene SYNE4. A rare condition, children who inherit the gene from both parents are born with normal hearing that gradually becomes weaker over the course of their childhood. This happens as the mutation causes mislocalization of cell nuclei in the hair cells inside the inner ear's cochlea (used to detect sound), and eventually leads to their degeneration and death.
To see whether they could stop this process in its tracks, the researchers created a harmless synthetic virus capable of delivering a normal version of the SYNE4 gene to cells. They then injected this variant into the inner ear of mice carrying the mutated version soon after birth so it could enter their hair cells.
As the mice grew older, the researchers monitored their hearing with physiological and behavioral tests. In the end, they found that mice treated soon after birth developed normal hearing with a sensitivity practically the same as that of healthy mice born without the mutation. Given this success, the researchers are now developing similar therapies that may be used for other mutations that cause deafness.
"This is an important study that shows that inner ear gene therapy can be effectively applied to a mouse model of SYNE4 deafness to rescue hearing. The magnitude of hearing recovery is impressive.” says Professor Wade Chien from Johns Hopkins School of Medicine.
“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."