Deafened mice hear again

A drug that can regenerate damaged ear hair cells in mice.

Now, Edge and his colleagues have tested several gamma-secretase inhibitors to find the one with the strongest regenerative effect on inner ear stem cells. They then tested that drug on adult mice that had been deafened after 2 hours in an extremely loud sound chamber. The drug prompted supporting cells in the inner ear to become hair cells, and the treated mice regained some hearing, the group reports online today in Neuron. 

The gamma-secretase inhibitors were originally developed as a potential treatment for Alzheimer's disease, but clinical trials showed little effect on symptoms of dementia and serious side effects in the gut and the immune system. Giving the mice one of the drugs orally triggered similar side effects, the team reports, so they tried applying the compound directly to the membrane between the middle ear and the inner ear. That required minor surgery in the mice, but could be achieved with an injection in humans—a technique already in common use, Edge says. The direct application produced as much hair cell growth as the oral treatment, without significant side effects, the team reports. The drug isn't ready for clinical trials, Edge says, but "it's a foot in the door."

"This is a major step forward," says Yehoash Raphael, an auditory neuroscientist at the University of Michigan, Ann Arbor, who led the gene therapy study in guinea pigs. Although the treatment didn't restore full hearing, the improvement is significant, he says.

This is indeed a major step forward in regenerative medicine for the treatment of sensorineural hearing loss. It'd be a matter of time until clinical trials begin.