Deiters Cells Act as Mechanical Equalizers for Outer Hair Cells

The outer hair cells in the mammalian cochlea are cellular actuators essential for sensitive hearing. The geometry and stiff-ness of the structural scaffold surrounding the outer hair cells will determine how the active cells shape mammalian hearing by modulating the organ of Corti (OoC) vibrations. Specifically, the tectorial membrane and the Deiters cell are mechanically in series with the hair bundle and soma, respectively, of the outer hair cell. Their mechanical properties and anatomic arrangement must determine the relative motion among different OoC structures. We measured the OoC mechanics in the cochleas acutely excised from young gerbils of both sexes at a resolution fine enough to distinguish the displacement of indi-vidual cells. A three-dimensional finite element model of fully deformable OoC was exploited to analyze the measured data in detail. As a means to verify the computer model, the basilar membrane deformations because of static and dynamic stimu-lations were measured and simulated. Two stiffness ratios have been identified that are critical to understand cochlear physics, which are the stiffness of the tectorial membrane with respect to the hair bundle and the stiffness of the Deiters cell with respect to the outer hair cell body. Our measurements suggest that the Deiters cells act like a mechanical equalizer so that the outer hair cells are constrained neither too rigidly nor too weakly.

Automated summary

This article focuses on the mechanical properties of outer hair cells and the surrounding structures in the mammalian cochlea, as well as their impact on mammalian hearing. The study finds that the stiffness of the tectorial membrane and the Deiters cell play a critical role in determining the relative motion among different structures in the organ of Corti. The Deiters cells act as a mechanical equalizer to ensure that the outer hair cells are neither too rigid nor too weak.