Gene therapy could solve hereditary deafness in children

A cure for hereditary deafness could be on the horizon after scientists used gene therapy to successfully treat the condition in mice.

In a new study, researchers provided healthy copies of the gene causing deafness in mice by injecting a harmless virus loaded with the healthy gene into the mice's ears.

The result was that the healthy gene was successfully loaded into the mice's DNA and the animals were once again able to detect noise.

The researchers noted that the gene responsible for hereditary deafness in mice is very similar to the corresponding gene in human DNA and hope for clinical trials to commence in five years.

According to the World Health Organisation, 360 million people suffer from disabling hearing loss due to both biological and environmental causes. Hereditary conditions account for at least half of all childhood deafness.

Currently, treatment for hearing loss involves the use of hearing devices, such as hearing aids and cochlear implants. While these devices can assist with hearing and reduce the level of deafness, there is no known method of restoring hearing completely.

The study, published in the Science Translational Medicine journal, focused on TMC1, one of the 70-plus genes responsible for hereditary deafness. Mutations to TMC1 cause deafness by blocking tiny channels in the inner ear which open to receive sound waves.

The researchers attached healthy copies of the gene to a harmless virus, which was injected into the inner ears of the mice and 'infected' hair cells in the ears of the deaf mice.

Within one month, about 50% of the mice recorded brainwave activity consistent with hearing and jumped when exposed to loud noises, indicating a restoration of hearing.

Next steps in the research include making the procedure more efficient and ensuring that hearing restoration is maintained for a lifetime, rather than just a few months as found in the mice.

The research team, which included scientists from the Swiss Federal Institute of Technology and Harvard Medical School in Boston, also found that gene therapy may be a viable means of treating hereditary blindness. Certain mutations in the TMC1 gene are responsible for Usher Syndrome, where hereditary deafness and blindness occur together.

Gene therapy involves the use of healthy genes as 'drugs' to combat or prevent diseases caused by genetic mutations.

Recent research has found that the technique could be used to treat cystic fibrosis, the most common life-shortening disease in the UK, within a timespan of five years.