Hearing Loss and Guinea Pigs

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(HOST) If you become hard-of-hearing in the future, commentator Ruth Page says it may be that experiments now being done on deaf guinea pigs will help you to a cure.

(PAGE) Ears, both ours and animals’, are useless without hair cells. Not those on our heads – though that would be handy for those of us who are hard-of-hearing in advanced age – but hair-like cells deep inside the inner ear. They detect sounds. As a sound wave strikes the hairs, they move with the vibrations; they send the electrical signals to the auditory section in the brain.

We may, if we’re lucky, get some help in reducing hearing loss from lessons learned with guinea pigs. Those common pets are being used in experiments to find ways to correct hearing loss in human beings. While we’re far from the old-fashioned ear trumpets of earlier ages, modern hearing aids still leave a lot to be desired. When you buy the latest models with their expensive electronic innards, the first thing doctors tell you is that they won’t return your hearing to its former state.

For two years, a research team at the University of Michigan Medical School succeeded in regrowing ear hair cells in adult guinea pigs. They had rendered the animals profoundly deaf by destroying all the hair cells in their ears. They then inserted a virus to create the new set of hair cells. They used a virus carrying a mouse version of the gene that’s usually expressed in the embryo.Its job is to create hair cells deep in the ear as the embryo develops. Once the cells have accomplished that job, the genes just turn off.

Researchers had a control group of guinea pigs that did not receive the gene, another group that got the gene to build new hair cells in one ear. After eight weeks, there was no change in the control groups’ deafness. Critters that had been treated, however, actually had normal hearing restored. The test they used to learn this was the same one used on people, and it proved the animals had gone from utterly deaf to being able to hear.

At Harvard, another team found that if they eliminated the gene that stops embryonic development of hair cells in mice, researchers could cause the cells to continue producing hair cells even after the mice were born.

Further tests must be done; we always learn of these promising outcomes early, before all the wrinkles have been ironed out. Will gene therapy work when the guinea pigs’ hearing loss comes about naturally, rather than being induced in the lab? Will it work as well when there’s a big time gap between hearing loss and the insertion of the corrective gene?

We don’t know yet, but as a hearing impaired person who’s tired of counting on hearing aids that work far better on mechanical noises like doors slamming or heels clicking than on human voices, I hope the experiment pans out. It may be way too late for me, but I’d like to be confident that our kids and grandkids can be helped if necessary.

This is Ruth Page in Shelburne.

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