Inner ear of chicken yields clues to human deafness and balance...( St. Louis May 22 2003 Scientists at ...)

The research provides new clues as to why birds can replace critical cells in the inner ear and humans cannot. Loss of these so-called sensory hair cells in humans is a leading cause of deafness and impaired balance due to aging, infectious disease and exposure to loud noise. The study will be published in the June 1 issue of the journal Human Molecular Genetics and appears online today.

The team measured the activity of more than 1,800 genes in sensory cells from two regions of the chicken inner ear: the cochlea, where sound is converted into nerve impulses, and the utricle, where balance is sensed. The utricle of birds replaces sensory cells regularly, while the cochlea replaces them when they die. The investigators discovered more than 100 significant differences between the two regions.

The findings provide new insights into the causes of deafness due to aging and the loss of these essential cells. They also may help improve knowledge of how the inner ear develops.

Ultimately, we hope our work will lead to some form of therapy that will replace these cells when they are lost, says lead investigator Michael Lovett, Ph.D., professor of genetics and of pediatrics and joint director of the Division of Human Genetics. We are born with only a few thousand sensory hair cells in each ear, and to maintain hearing and balance we have to keep them for our entire lives.

At least 30 million Americans suffer from significant hearing loss and balance disorders, Lovett says. One-third of people above age 65 and half of people above age 75 have significant hearing loss. About 80 percent of these problems result from the loss of, or damage to, sensory hair cells. The cochlea and utricle function nearly identically in birds a
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Contact: Darrell E. Ward
wardd@msnotes.wustl.edu
314-286-0122
Washington University School of Medicine
22-May-2003