Research on Mysterious Inner Hair Cells, New Hearing Drug Funded by NIH Grants to UB Center for Hearing and Deafness

BUFFALO, N.Y. -- Diagnosing damage to a special group of sensory cells in the ear that affects hearing and determining whether a new pharmaceutical compound can protect the inner ear against hearing loss will be the focus of two grants awarded by the National Institutes of Health to the Center for Hearing and Deafness at the University at Buffalo.

A $1.7 million, 5-year grant will allow center researchers to conduct behavioral and anatomical studies of the inner ear's inner hair cells, a crucial sensory component of hearing about which little is known.

Inner hair cells in the cochlea transfer sound stimuli, which have been amplified by the outer hair cells, to the brain's auditory center. Loss of these inner hair cells causes a hearing disorder that appears to be similar to a human hearing disorder referred to as auditory neuropathy.

"In auditory neuropathy, the brain is getting only a small amount of information and consequently it can't process sounds very effectively," said Richard Salvi, Ph.D., director of the Center for Hearing and Deafness and primary researcher on the study.

"With this new grant we are trying to study what's going on in the brain's auditory processing center when it is getting substantially less information that it normally receives. Almost nothing is known about functional deficits associated with inner hair cell damage. Using an animal model, we've found a compound that selectively destroys inner hair cells without damaging outer hair cells.

"These animals (rats) have been trained to report to us through their behavior how and what they can hear," he said. "This model and the new grant give us the opportunity to study this condition in depth. We do not have any definitive tests that tell us when the inner hair cells are malfunctioning. Our findings could lead to better methods for diagnosing when the inner hair cells are damaged."

The second grant, a one-year small business technology transfer grant for $145,000, will be used to test the potential of a newly formulated protease inhibitor to prevent the death of auditory neurons. Previous work with animals at the center has shown that infusing the compound directly into the cochlea prevents destruction of sensory hair cells in the inner ear caused by exposure to loud noise or certain medications that are toxic to the auditory system.

The new study will test the protective potential of a new preparation of the compound, developed by CepTor Corp., that can be placed under the skin or taken orally rather than being delivered to the inner ear, a method that would not be practical for use in humans.

The preparation will be tested for protection against damage from both noise and ototoxic medications in an animal model in three concentrations and compared to controls.

"If this preparation provides significant protection from both these insults in animals, then limited phase II trials could conceivably be initiated in patients if the drug has no negative side effects," Salvi said. "Protection from noise-induced hearing loss and ototoxicity would address a major health problem."