HEARING research will be revolutionised by the discovery that inner ear cells
of mice can be grown in culture, say researchers in Britain.
The finding will help scientists pinpoint the genes responsible for ear
development, and allow them to test drugs that could treat hearing loss. If the
technique can be extended to human cells, such transplants could be used to
improve the performance of cochlear implants and perhaps even to replace damaged
cells in the ear.
Matthew Holley, now at the University of Bristol, and his colleagues isolated
cells from embryonic mouse cochleae鈥攖he parts of the inner ear that detect
sound. The mice are genetically engineered so that cell division can be switched
on or off at will, allowing the cells to be grown indefinitely. When the
researchers allowed the cells to stop dividing and specialise, they found that
they looked and behaved like 鈥渉air cells鈥�.
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Hair cells detect sounds and relay the information to the neighbouring
auditory nerve, which in turn transmits the signal to the brain. Damaged cells
are not replaced, and if there are no hair cells around, the auditory nerve
degenerates. Cochlear implants work by directly stimulating the auditory nerve
in people whose hair cells are damaged. They can鈥檛 help people whose auditory
nerves have deteriorated too far.
Holley hopes that implanting human hair cells will make failing auditory
nerves grow back. This would improve the electrical contact between cochlear
implants and the brain, he told the Genetics and Deafness conference in London
this week. 鈥淭his opens up the prospect of making implants more effective and
using them on a much wider scale,鈥� he says. Only about 3000 people in Britain
currently have implants.
Holley has yet to try the transplants in mice, or to culture human hair
cells. But he is applying gene-chip technology to find out which genes are
active in development and how the cells respond to different drugs. 鈥淭his is
going to be one of the most important outcomes of the research,鈥� says Karen
Steel, a geneticist at the Medical Research Council鈥檚 Institute of Hearing
Research. 鈥淚t鈥檚 a very useful model system for studying development.鈥�
Restoring hearing with transplants is still a long way off鈥攁nd is not
welcomed by all deaf people. But it may at least become an option in the future.
鈥淚鈥檓 pretty sure that in five years鈥� time we鈥檒l be in a very different
position,鈥� says Holley.