There are around 11 million people in the UK, or one in six members of the population, who suffer with hearing loss, and nearly half of all these cases have a genetic cause.
Treatment has long been limited because scientists didn’t have the right technology at their disposal to treat the underlying problem, but a new study has found gene editing could provide the solution.
Investigator David Liu, who worked on the study, said: “[It] could make a major difference in hearing-loss patients’ quality of life.”
The work, which is among the first to apply genome editing to deafness in animals, looked at one mutation in a gene called Tmc1 – a single spelling error in this gene causes the loss of inner ear hair cells over time.
These delicate bristles detect sound and then convert this information into nerve signals to travel to the brain. The loss of these bristles causes profound deafness in both humans and mice.
Liu, said: “The conventional thinking in the field is that once you’ve lost your hair cells, it’s difficult to get them back.”
So the team looked at what would happen if they administered a single injection of the CRISPR-Cas9 genome editing cocktail to the inner ear on infant mice.
They hoped that the technology would be able to remove the mutation and stop the bristles from dying.
What is CRISPR?
CRISPR-Cas9 technology is an enzyme that acts as an injectable ‘molecular scissor’ and can be used by scientists to edit DNA strands.
For example, in an embryo found to have a problem, the tool can ‘snip’ out the offending DNA. It has already been used to remove hereditary heart conditions, potentially stop HIV in its tracks, and create low-fat pigs.
Embryos modified by CRISPR are not permitted to carry children to term, it is only for purposes of “better understanding” human development. In the UK, the UK Human Fertilisation and Embryology Authority (HFEA) 2016 licensing, says embryos must be destroyed within 14 days.
After eight weeks, hair cells in treated ears resembled those in healthy animals, meaning it was densely packed and tufted with hairlike bundles. While the hair cells of untreated mice, in contrast, looked damaged and sparse.
Even just one shot was found to prevent progressive hearing loss in young animals that would have otherwise gone deaf. The regrowth of these hairs allowed them to hear sounds about 15 decibels lower than untreated ears.
“That’s roughly the difference between a quiet conversation and a garbage disposal,” Liu said.
Because the study was performed in mice, the implications for treating humans are still unclear, but they did say they hoped it would work in the same way in humans.