New Lead on Hearing Loss

Gene Found That Could Help Restore Hearing

From the WebMD Archives

Jan. 13, 2005 -- There's new hope that irreversible hearing loss may one day be reversible.

Tweaking a single gene holds promise that one day this may happen, evidence shows.

The gene -- called Rb1 (retinoblastoma) -- has a vital job. In this case it determines whether tiny hair cells tucked deep inside the ear can be replaced.

Ordinarily the hair cells, found in the ear's cochlea, are only made once in a lifetime. When they die, they're gone for good; no new hair cells can be produced. The sure but steady loss of inner ear hair cells can result in hearing loss that accompanies normal aging.

Humans are born with about 50,000 of the hair cells. But a third of 70-year-olds have significant hearing loss due to death of the ear's hair cells. Hearing loss is irreversible because hair cells don't regenerate.

That's because of the Rb1 gene. It makes retinoblastoma protein, which blocks the ear's new hair cell production.

That could change with a little genetic coaxing. That theory was recently tested by researchers, including Cyrille Sage of Massachusetts General Hospital and Harvard Medical School. The results appear in the online edition of Science.

The researchers and their colleagues developed mice lacking the Rb1 gene. The study showed that mice without the Rb1 gene had more hair cells than normal mice. These mice were actively producing new hair cells.

The strategy may ultimately allow the regeneration of hair cells in mammals, say the researchers. They want to see if the Rb1 gene can be temporarily turned off to let new hair cells form, instead of deleting the gene completely. That could help prevent the cells from growing unchecked, which could cause tumors to form in the inner ear.

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SOURCES: Sage, S. Sciencexpress, Jan. 13, 2005. News release, Howard Hughes Medical Institute.
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