Scientists believe a transplant of brain cells may one day be able to reverse a common form of hearing loss.
Damage to hair cells in the inner ear due to ageing and overstimulation causes hearing problems in 10% of people worldwide.
The cell loss is irreversible, but US scientists believe it may be possible to replace them with stem cells from a region of the brain.
The study appears in Proceedings of the National Academy of Sciences.
"There might be questions as to whether taking cells from the brain to replace inner ear hair cells would prove clinically acceptable"
The key ependymal cells come from the lining of the lateral ventricle of the brain.
They share characteristics with inner ear hair cells - but crucially, unlike them, they have the ability to reproduce.
The researchers, led by Dr Dongguang Wei, from the University of California at Davis, believe the brain cells could potentially be transplanted from a person's brain into their ear, where they would take on the role of hair cells, and restore hearing.
Nerve cells
Loss of inner ear hair cells often also leads to breakdown of the nerve cells along which the signals they generate are transmitted to the brain.
The researchers believe these spiral ganglion cells can also be replaced - this time by stem cells from another area of the brain's lateral ventricle.
Their conclusions are based on a detailed analysis of the structure, chemistry and role of the brain cells.
Tests of the theory are already underway in the laboratory.
And they believe the cells also hold out hope for use in the treatment of diseases of the nervous system.
Professor Andy Forge, of the University College London Ear Institute, said previous work had suggested that the inner ear might have a small number of stem cells of its own which might be able to replace damaged hair cells.
Others are working on using embryonic stem cells to achieve the same effect.
The latest paper raised the possibility of a third potential source of cells.
Professor Forge said: "The present paper identifies a possible single tissue source for both the elements that may be lost from the damaged sensory tissues of the inner ear.
"However, there might be questions as to whether taking cells from the brain to replace inner ear hair cells would prove clinically acceptable."
Dr Mark Downs, of the charity RNID, said nine million people in the UK alone were deaf or hard of hearing, but much work was underway into developing restorative treatments.
He said: "There is a long way to go. This research is still at a very early stage and but the future looks increasingly brighter for people with hearing loss."
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