Healthy hair cells are vital to the ability to hear, but aging, infection, certain medications and exposure to loud noises can damage or destroy hair cells causing sensorineural hearing loss a condition affecting over 30 million Americans. Since the discovery, in the late 1980s, that birds can spontaneously regenerate damaged hair cells, scientists have been trying to find a way to induce the replacement of lost hair cells in mammals.
U-M scientists have now accomplished this goal by inserting a gene called Math1 into non-sensory epithelial cells lining the inner ear. Results from the study will be published in the June 1 issue of the Journal of Neuroscience.
"We found that non-sensory epithelial cells in adult guinea pig cochlea can generate new sensory hair cells following the expression of Math1," says Yehoash Raphael, Ph.D., an associate professor of otolaryngology in the U-M Medical School, who directed the study. "We also found that some of these hair cells can attract the growth of new fibers from auditory neurons."
In a normal ear, vibrations from sound waves striking the eardrum are transferred to fluid inside a snail-shaped bony organ called the cochlea, which is the auditory component of the inner ear. When cochlear fluid moves, it stimulates movement in thousands of tiny projections on hair cells lining the inside of the cochlea. Moving hair cells initiate electrical signals, which are picked up by auditory nerve fibers and carried to an area of the brain called the auditory cortex. If hair cells are damaged or missing, electrical signals are not generated and hearing is impaired.
"During the embryonic stage of an animal's development, hair cells and supporting cells have a common origin. Cell
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Contact: Sally Pobojewski
pobo@umich.edu
734-615-6912
University of Michigan Health System
31-May-2003