In vivo nano-scale vibrometry in apical-basal ends of contractile outer hair cells in the mammalian cochlea by supercontinuum source spectral-domain OCT

摘要

The cochlea of the inner ear transduces sound energy into electrical signals that are essential for audition. Thistransduction is processed in nano-scale vibration of the cochlear sensory epithelia. In mammals, the epithelia containvarious cells and structures: inner hair cells, outer hair cells (OHCs), Deiters’ cells, basilar membrane, reticular lamina,etc. The sound elicits vibration in all these constituents. Among them, only OHCs cell body actively and periodicallychanges in length in association with the vibration. The unique mechanical activity of OHCs modifies the sound elicitedvibration in the epithelia with a feedback mechanism. Although the modification is considered to critically contribute tothe high sensitivity and sharp tuning in hearing through sensory IHCs, the real motion of OHCs remains uncertain.Vibrometrical studies of cochlear mechanics has revealed important vibration of the cell bodies involving the epithelia.However, difference in vibration pattern of the apical and basal ends of the cell has remain uncertain due to low spatialresolution of the system and low reflectivity of the cells. We performed a spectral domain OCT (SD-OCT) vibrometryby using the modified commercial SD-OCT system. Because the broad spectral bandwidth and strong power of the lightsource improve a performance of OCT systems in both of imaging and vibrometry, we introduced a supercontinuumlight source into the commercial system. Our system achieved cellular-level tomographic imaging and subnano-scalevibration measurement in the transparent epithelia with the recording time of 100 ms in in vivo animal.