Hearing loss affects approximately 11 million people in the UK (roughly 1 in 7 or 19% of the total population), which means that finding a permanent solution would be life-changing for lots of people.
Although scientists already know that injecting ear stem cells into the inner ear can reverse deafness, they have been cautious as this process can be a double-edged sword, making cells divide too quickly and causing cancer.
But now, a new study led by Rutgers University, New Brunswick, has found that this rapid division of cells could be controlled - well, at least in a petri dish.
Hearing loss, whether occurring over time or suddenly, is primarily caused by damage to the hair cells in the inner ear, which convert sounds into neural signals that are relayed to the brain by spiral ganglion neurons.
“Over the years, you don’t realise that you’re not hearing well until you get tested. We’re one of the few labs trying to figure out how to address the hearing loss issue,” said Kelvin Y. Kwan, senior author of the paper published in Stem Cell Reports
And once the neurons are lost, they do not regenerate.
Injecting inner ear stem cells, which can be converted to auditory neurons by the overexpression of a gene called NEUROG1, has long been cited as a potential method, but Kwan notes it is a “cautionary tale”.
“People say, ‘we’ll just put stem cells in and we’re going to replace lost neurons’. We’re saying that ‘yes, we can make neurons,’ but you have other side effects that are unanticipated, such as increased proliferation of stem cells.”
In order to counteract this, Kwan’s team used chromatin - a DNA studded with histone proteins - to influence how NEUROG1 functions.
“Changes in chromatin may help reduce unwanted stem cell proliferation and can be achieved by adding drugs to experimental cultures,” he said.
This development doesn’t just apply to hearing loss therapies, Kwan says that scientists in other fields should be aware that when using this factor, they’ll probably also increase cell proliferation.