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Rebecca M. Lewis
Postal:
Department of Otolaryngology/ Head and Neck Surgery Virginia Merrill Bloedel Hearing Research Center CHDD CD176 Box 357923 University of Washington Seattle, Washington 98195 USA
Email:
becky103@uw.edu
Edwin W Rubel
Postal:
Department of Otolaryngology/ Head and Neck Surgery Virginia Merrill Bloedel Hearing Research Center CHDD CD176 Box 357923 University of Washington Seattle, Washington 98195 USA
Email:
rubel@uw.edu
Jennifer S. Stone
Postal:
Department of Otolaryngology/ Head and Neck Surgery Virginia Merrill Bloedel Hearing Research Center CHDD CD176 Box 357923 University of Washington Seattle, Washington 98195 USA
Email:
stoner@uw.edu
Regeneration of Auditory Hair Cells: A Potential Treatment for Hearing Loss on the Horizon
Regeneration of cochlear hair cells is being investigated as a potential therapy for hearing impairments.
Introduction
The process of hearing involves a complex chain of events, and each one is impor- tant to ensure the proper detection and processing of sounds. In the first step, sound waves traveling through the environment enter the ear canal and vibrate the ear- drum. This energy is transmitted through the three bones of the middle ear to the inner ear. Within the inner ear, the energy derived from the sound waves is trans-
Figure 1. Schematic diagrams principal structures of the inner ear tissues (A), a slice through one turn of the cochlea (B) and the organ of Corti (C). Note that in the organ of Corti a single inner hair cell and three outer hair cells are shown along with the sup- porting cells. This pattern is repeated about 3,000 times along the spiraled cochlea in humans.
mitted to the basilar membrane of the co- chlea, on which lies the sensory organ for hearing, the organ of Corti (Figures 1 and 2A).
The organ of Corti is composed of sen- sory hair cells as well as a group of special- ized cell types, col- lectively called sup- porting cells, and the peripheral processes of auditory neurons. Hair cells are sensory receptors. Respond- ing to the mechani- cal signals derived from sound waves, hair cells transduce this energy into elec- trical signals that are transmitted via the auditory nerve to the brain. In the normal human ear, there are
about 3,000 inner hair cells and 12,000 outer hair cells (Bredberg, 1967). Inner hair cells (Figure 2B) are the true sensory receptors. On stimulation, the inner hair cells activate auditory nerve fibers that in turn activate auditory brainstem nuclei. The major function of the outer hair cells (Figure 2C) is to modulate the func- tion of the organ of Corti by enhancing signal processing of low-ntensity auditory signals. These two types of hair cells work together such that the auditory nerve
40 | Acoustics Today | Summer 2016 | volume 12, issue 2 ©2016 Acoustical Society of America. All rights reserved.