GENE therapy has partially restored hearing in deafened guinea pigs, raising hopes that the approach might work in people.
鈥淚t鈥檚 the first time anyone has biologically repaired the hearing of animals,鈥� says Yehoash Raphael of the University of Michigan in Ann Arbor, head of the US-Japanese team that is developing the therapy.
Millions of people each year go deaf when the sound-detecting hair cells in the inner ear are destroyed by certain antibiotics, old age or loud noise. These cells do not normally regrow in mammals, but two years ago Raphael鈥檚 team managed to grow new hair cells in deaf guinea pigs using gene therapy (New 杏吧原创, 7 June 2003, p 15).
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However, the presence of new hair cells alone was not enough prove that the guinea pigs could hear again. So in their latest experiments, the team measured the animals鈥� auditory brainstem response. This test, sometimes used to assess hearing in people, involves recording brain waves using electrodes to find out if the brain is responding to sounds.
The results exceeded the team鈥檚 expectations. 鈥淭he recovery of hair cells brought the treated ears to between 50 and 80 per cent of the hearing thresholds they鈥檇 had originally,鈥� says Raphael, whose results appear in Nature Medicine (DOI: 10.1038/nm1193).
But human trials are still some way off. The gene that stimulates hair cell growth is added to cells using modified cold viruses, and there is a risk people could react badly. Injecting the virus is also more difficult in humans.
