Genes and Deafness: What's Next

Listen: <b>Web Extra</b>: Dr. Battey on Hearing

Host Jennifer Ludden discusses the new research breakthrough on hearing loss with Dr. James Battey, who directs the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health.

Battey explains what research remains to be done, before gene therapy can be tested on humans.

 

Transcript of This Story

JENNIFER LUDDEN, host:

To get a better sense of what this research might mean, we've invited in Dr. James Battey. He's the director of the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health.

Dr. Battey, welcome.

Dr. JAMES BATTEY (Director, National Institute on Deafness and Other Communication Disorders, National Institutes of Health): It's a pleasure to be with you today.

LUDDEN: How significant is this development of having restored hearing in a guinea pig?

Dr. BATTEY: First of all, it was not believed that a single gene could direct the production of hair cells in the inner ear of a mammal, and Dr. Raphael's work has shown us this. The work is also remarkable in that it emphasizes the importance of using different animal models to uncover important things for biomedical research. For example, this gene was initially discovered in the fruit fly drosophila, its importance in the hearing organ established in a mouse model. And now Dr. Rafael is using a guinea pig model to show that by introducing this gene back into cells in the inner ear, he can restore hair cells that had been lost as a consequence of administration of a drug that's toxic to these cells.

LUDDEN: Can this be translated into help for humans, and what kind of time frame, do you think?

Dr. BATTEY: Often there are species differences in the ability to take single genes like this and use them to push cells to become very interesting, specialized type of cells. We'll have to do lots more work in animal models to establish both the efficacy and the safety of this technique, determine that it restores function for a prolonged period of time and that the hair cells are stable and continue to function well in animal models besides the guinea pig; maybe moving next into non-human primates and then, finally, into the first phase I clinical trials when all the safety and efficacy issues have been established.

LUDDEN: How many people potentially in the United States, do you think, could be affected by this kind of research, should it prove successful?

Dr. BATTEY: The institute does estimate that roughly 28 million Americans suffer from significant loss of hearing. And as the population ages, that number is almost certainly going to be greater. In addition, many individuals also suffer from balance disorders. And the balance organ, which is located right next to the hearing organ, also uses hair cells as its signal detection mechanism.

LUDDEN: What kind of deafness could be best helped by this new method of regrowing these hair cells?

Dr. BATTEY: Perhaps the most promising situation would be a situation where an individual loses their hearing rapidly or is born without the ability to hear. In those two scenarios, reintroduction of the gene into the inner ear may result in the restoration of hair cells. So I would think that those would be the two scenarios in which one might first think about trying this particular application in humans should it survive all of the trials and tests in the variety of animal models that we talked about earlier.

LUDDEN: Of the people who suffer from some type of deafness in the U.S., do you know what percentage are deaf because of damage to these hair cells?

Dr. BATTEY: The overwhelming majority is a result of hair cell loss. Now once the hair cells are lost, if they're gone for a prolonged period of time, then the nerves that connect to these hair cells also begin to die and go away. So one big question as to how effective regrowing hair cells will be is that in a human, who may lose their hearing over decades as they age, there may be loss of the nerves that connect to these hair cells. This is a very different scenario than the one in Dr. Raphael's experimental paradigm where all the hair cells go away acutely over a short period of time and the intervention takes place right away.

LUDDEN: Dr. James Battey is director of the National Institute on Deafness and Other Communication Disorders at the NIH.

Dr. Battey, thank you very much.

Dr. BATTEY: It's been a pleasure. Thank you.

LUDDEN: For a longer version of our interview with Dr. Battey or to learn more about how the ear hears, go to npr.org.

 

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