Deafness could be reversed after scientists ‘overcome major hurdle’
Deafness in old age could be reversed after scientists discovered the master gene needed to regrow lost hearing cells.
Humans are born with sensory cells in the ear known as hair cells, but once these die through age, noise damage or cancer treatment, they cannot grow back, bringing irreversible hearing loss.
It is the death of outer hair cells, made by the spiral cavity of the inner ear, the cochlea, that is most often the cause of deafness and hearing loss, but scientists had never found a way to regrow them.
Now, researchers at Northwestern University in the US have found that a single gene programmes hair cells to become either outer or inner cells in a breakthrough that could open the door to curing deafness in later life.
“We have overcome a major hurdle,” said Jaime Garcia-Anoveros, professor of anaesthesia, neurology and neuroscience at Northwestern University’s Feinberg School of Medicine, and the lead study author.
“We can now figure out how to make specifically inner or outer hair cells and identify why the latter is more prone to dying and cause deafness.”
‘The ear is a beautiful organ’
In Britain, about 40 per cent of people aged 50 years and 71 per cent of people aged 70 years and older have hearing loss. Not only is the condition debilitating, but it has been linked to an increased risk of dementia.
Most people who experience hearing loss as they get older do so because of wear and tear to the hair cells in the inner ear.
Hair cells develop in the embryo and inner and outer cells work together to produce hearing.
The outer hair cells expand and contract in response to the pressure of sound waves and amplify sound for the inner hair cells.
The inner cells transmit those vibrations to the neurons to create sounds.
“It’s like a ballet,” added Prof Garcia-Anoveros. “The outers crouch and jump and lift the inners further into the ear.
“The ear is a beautiful organ. There is no other organ in a mammal where the cells are so precisely positioned. Otherwise, hearing doesn’t occur.”
‘Cocktail of genes’
Hair cells cannot spontaneously regenerate, so once they die they cannot be restored. The team discovered that the production of the hairs is driven by a master gene called TBX2.
When the gene is expressed, the cell becomes an inner hair cell. When the gene is blocked, the cell becomes an outer hair cell.
Scientists can already make a basic hair cell from a non-hair cell using a cocktail of genes, but have never been able to achieve the differentiation needed for hearing until now.
The goal would be to eventually reprogramme cells in the ear so they can reform as hair cells, and restore hearing.
The research was published in the journal Nature.
