For some two million people in the UK, hearing aids are a vital lifeline, allowing them to stay in touch with the world around them.
But they cannot restore hearing – the devices work by amplifying sounds – and despite modern, sleek designs, for many people there is still a stigma attached to wearing them.
Now a UK clinical trial, the first of its kind in the world, is about to test a groundbreaking new treatment that could, if successful, banish the need for hearing aids altogether in some people.
It involves stem cells (immature cells which can develop into new nerves and tissue) that have been grown in the lab from donor cells being injected deep inside the damaged ear.
Once there, the hope is these stem cells will grow into healthy new auditory nerve cells – which transmit sounds from the inner ear to the brain – replacing those irreversibly damaged by the ageing process, faulty genes or infections such as measles or mumps. There are currently no treatments for this type of nerve damage.
In animal tests, the stem-cell jab not only proved safe but also significantly improved hearing.
Now scientists at Rinri Therapeutics, a spin-out company from Sheffield University – where the treatment was developed – have been given the go-ahead to test the jab on 20 patients with severe hearing loss to see if they can achieve the same results in humans.
An estimated 1.2 million adults in the UK have severe hearing loss that means they cannot hear most conversational speech, according to the Royal National Institute for Deaf People.
Doug Hartley, professor of otology at Nottingham University, says the otic neural progenitor cells are injected ‘into the tiny space between the inner ear and the brain, and tests show they… crucially don’t turn into any other type of cell’
Some 12,000 are so profoundly deaf they have been fitted with cochlear implants – tiny electronic devices, costing around £20,000 each, surgically implanted deep inside the cochlea (a snail-shaped compartment inside the ear) to do the job of delicate hair cells destroyed by ageing, loud noise or infection.
In a healthy ear, these hair cells convert sounds into electrical impulses that travel along the auditory nerve to the brain. But once destroyed they do not regenerate.
It was once thought the loss of these hair cells was the chief cause of age-related hearing loss. However, it’s now believed it may be more to do with auditory nerve cell damage.
The hope is that a single dose of the stem-cell injection –called Rincell-1 – will completely reverse hearing loss in people who are deaf because of damage to their auditory nerves.
The clinical trial will take place at three NHS sites – University Hospitals Birmingham, Cambridge University Hospitals, and Guy’s and St Thomas’ NHS Trusts.
The stem-cell treatment will be given under general anaesthetic to 20 profoundly deaf patients as they undergo cochlear implant surgery. In future, it might be possible to inject it without surgery.
Key to the process is the type of stem cells used. Called otic neural progenitor cells, these are just one developmental stage away from being fully mature auditory nerve cells. Once inside the inner ear, they make that final leap to fully matured, working cells.
‘They have already decided they are going to become auditory nerve cells,’ says Doug Hartley, chief medical officer of Rinri Therapeutics and a professor of otology at Nottingham University. ‘We inject them into the tiny space between the inner ear and the brain, and tests show they stay where we put them and, crucially, don’t turn into any other type of cell.’
Professor Nish Mehta, a consultant ear, nose and throat surgeon at University College London Hospitals, agrees the test results are ‘really promising’ but warns there are risks involved
This is important as a long-running concern about all stem-cell treatments, for any condition, is whether injected cells could turn cancerous, as they have the capacity to become any type of cell, including – theoretically – cancer cells.
Professor Hartley says the first results are due in 2027 and, if all goes well, the treatment could be used on patients with mild to moderate age-related hearing loss who don’t need cochlear implants.
Kevin Munro, a professor of audiology at Manchester University, says: ‘This is exciting. Hearing aids and cochlear implants are helpful but you still get a lot of background noise and they’re not always that effective.
‘If they’re successful, it has the potential to transform the lives of thousands with hearing loss due to nerve damage.’
However, he warned that there is currently no easy way to determine if someone’s deafness is due to nerve damage or the destruction of hair cells in the cochlea. And it’s not guaranteed that fixing the nerve damage will translate to better hearing.
Professor Nish Mehta, a consultant ear, nose and throat surgeon at University College London Hospitals, agrees it’s ‘really promising’.
He told Good Health: ‘Tests on mice found that after the treatment the brain was receiving sound information, where it wasn’t before.’
But he warns there are risks involved – opening up the inner ear to inject stem cells, or put in cochlear implants, can destroy remaining healthy hair cells, damaging any remaining ‘natural’ hearing a patient may have.
He says: ‘About a third of people undergoing cochlear implants lose all their remaining hearing.’
