Here’s a news piece about an exciting research breakthrough on a possible future stem cell-based cure for deafness: (originally published on 24n.biz):
Researchers at the University of Sheffield have restored hearing in deafened gerbils by transplanting auditory neurons obtained from stem cells into their cochleae – the part of the inner ear that converts sound into electrochemical impulses.
Project leader, Dr Marcelo Rivolta said: “This is an important step forward. We have the proof-of-concept that human stem cells could be used to repair the damaged ear.”
Hair cells in the cochlea have tiny hairs called stereocilia that bend when brushed by a membrane vibrating in response to sound. This activity is passed on at synapses to spiral ganglion neurons (SGNs) in the auditory nerve, generating impulses that travel up the nerve to the brain to create our perception of sound. When SGNs are dead or damaged it results in a form of hearing loss called auditory neuropathy, which accounts for about 10% of deafness. This can’t be corrected by cochlea implants as they effectively replace the function of hair cells and so need a healthy auditory nerve to work.
The team, led by Dr Marcelo Rivolta, reported in Nature on Wednesday that they induced human embryonic stem cells to differentiate into two types of “precursor” cells able to differentiate in vitro into either “hair-cell-like” cells or auditory neurons. They injected the neuron precursors, which they called “otic neural progenitors”, into the cochleae of gerbils whose SGNs had been destroyed with a drug and after ten weeks the cells had differentiated into SGNs and formed connections with the auditory nerve. They also found the gerbils’ hearing had improved by an average of 46 per cent, as measured by responses to sounds of varying loudness, making this the first time transplanted cells have been used to restore hearing in animals.
It is hoped the technique could lead to cell-based therapies for some deafness in humans, although this is likely still some years away.
Dr Ralph Holme, Head of Biomedical Research for Action on Hearing Loss, who part-funded the research, along with the Medical Research Council, said: “[This] gives us real hope that it will be possible to fix the actual cause of some types of hearing loss in the future. For the millions of people for whom hearing loss is eroding their quality of life, this can’t come soon enough.”
He added: “Cochlear implants provide a sensation of hearing, but they need a healthy auditory nerve to stimulate. By combining these devices with a therapy that repairs the auditory nerve many more people might be able to benefit from cochlear implant technology in the future.”
The hair cells obtained were not fully functional, lacking the stereocilia, and transplanting such cells would likely be much more difficult, but if this could be achieved in the future the way would be open for treating the vast majority of deafness.