Mechanically-facilitated Cochlear Fluid Homeostasis

University Of Rochester, Rochester NY

Investigators

Abstract

Different types of hearing loss/difficulty are ascribed to imbalance of two lymphatic fluids in the cochlea. Operating like an electrochemical battery, the cochlea is partitioned into three compartments filled with the lymphatic fluids. The separation of the two fluids provides an electric potential of approximately 80 mV that is crucial for hearing. To transduce sounds into neural impulses, there exists constant leaking (depolarizing) currents between the two fluid spaces through the sensory epithelium called the organ of Corti. Supporting cells in the organ of Corti must transport ions to maintain the electric potential. According to current theory, cochlear fluid homeostasis is responsible for the loss of auditory receptor cells (hair cells). The PIs test the converse of the current theory: they hypothesize that the mechanical feedback of auditory receptor cells facilitates the maintenance of cochlear fluid homeostasis. Successful demonstration of the research hypothesis will significantly increase our understanding of the mechanics of hearing. The investigators will include undergraduate students in their research project, teaching how engineering principles are applied to biological systems. Course projects for experimental fluid dynamics and a series of summer research projects for undergraduates will be based on the work. This research challenges the assumption of diffusion-limited ionic transport in the cochlear fluid. Recent observations show unique deformation patterns of the organ of Corti due to active mechanical feedback of the hair cells. This project aims to connect the active organ of Corti mechanics with cochlear fluid homeostasis by demonstrating a different mode of ion transport?peristaltic fluid mixing. Specifically, it will be shown that: 1) the electromotility of outer hair cells generates peristaltic fluid motions in the organ of Corti, and 2) the peristaltic fluid motions help to homogenize cochlear fluids. The results could transform hearing science by integrating two research domains that have not been considered together: mechanics and ion homeostasis of the cochlea. The investigators will include undergraduate students in their research project, teaching how engineering principles are applied to biological systems. Course projects for experimental fluid dynamics and a series of summer research projects for undergraduates will be based on the work.