Optical coherence tomography for 3D measures of cochlear mechanics in vivo

 说明书(申请人提供)：耳蜗的功能是将复杂的声压波转换为电信号。Corti振动器官是基于被动机械结构和基于OHC的主动过程之间的复杂相互作用。虽然激光多普勒测振法极大地增加了我们对耳蜗生理学的了解，但这项技术是有限的。只能测量基底膜上一点的运动，这只能替代听觉的测量：IHC立体纤毛束的偏转。因此，仅靠这些测量不能解释Corti器官内的细胞和组织如何协同工作来发展耳蜗放大。为了理解这一过程，需要对完整的Corti器官内的所有结构进行振动测量。我们开发了一种新的技术，体积光学相干断层扫描振动测量(VOCTV)，它克服了这些限制，因为它可以直接通过小鼠的耳囊骨成像，并同时分辨每个体素的振动。因此，我们正处于理解耳蜗的主动和被动机制如何驱动IHC刺激的尖端，即大脑接收的输入。我们的初步数据表明，在Corti器官内存在频率相关的差异运动。我们假设这些运动与OHC-Deiter细胞结的倾斜是机械耦合的，倾斜随着HC的被动刚度而变化，并且倾斜被OHC电动增强。这一假说很重要，因为如果是真的，这意味着OHC电动并不是通过增加Corti器官的垂直位移来改善听力，而是通过将基底膜的垂直位移转换为能够刺激IHC的径向流体运动来改善听力。我们的研究将通过比较野生型小鼠(OHC僵硬正常，电动正常)、Prestin 499小鼠(OHC僵硬正常，没有电动)和prestin基因缺失小鼠(OHC僵硬减少，没有电动)的活体振动模式来明确地衡量OHC的作用。第一个目标是使用我们现有的一维VOCTV系统来研究两个不同角度放置的小鼠，以测量整个Corti器官的垂直和径向位移。目标2是开发光学技术和软件，以便同时对每个体素进行3D振动测量(3D-VOCTV)。目标3是在活体小鼠身上使用3D-VOCTV来测量横向、径向和纵向运动。如果我们的假设是正确的，与死亡的野生型、活的prestin 499和活的prestin缺失的小鼠相比，野生型小鼠将表现出显著更大的OHC-Deiter细胞连接的径向和/或纵向位移。此外，与prestin 499小鼠相比，prestin缺失小鼠的这些位移的频率调谐应该不那么尖锐。用这笔赠款获得的数据可能会解释独特和高度结构化的解剖结构的基础 科尔蒂器官内的细胞。用这笔赠款开发的最先进的技术很可能成为在体振动测量的新标准。

 DESCRIPTION (provided by applicant): The function of the cochlea is to transduce complex sound pressure waves into electrical signals. Organ of Corti vibration is based upon a complex interplay between passive mechanical structures and active OHC- based processes. While laser Doppler vibrometry has added tremendously to our understanding of cochlear physiology, this technique is limited. Only motion from one point on the basilar membrane can be measured, and this provides only a surrogate measure for what is actually responsible for the sense of hearing: deflection of the IHC stereociliary bundle. Thus, these measurements alone cannot explain how the cells and tissues within the organ of Corti work collaboratively to develop cochlear amplification. Vibratory measurements of all of the structures within the intact organ of Corti are needed to understand this process. We have developed a novel technique, volumetric optical coherence tomography vibrometry (VOCTV, pronounced "voctive") that overcomes these limitations because it can image directly through the mouse otic capsule bone and simultaneously resolve vibrations at every voxel. Thus, we are at the cusp of understanding how the active and passive mechanics of the cochlea drive IHC stimulation, i.e. the input received by the brain. Our preliminary data demonstrate that frequency-dependent differential motion within the organ of Corti exists. We hypothesize that these movements are mechanically coupled to tilting of the OHC-Deiter cell junction, that the tilting varies with the passive stiffness of the HC, and that the tilting is enhanced by OHC electromotility. This hypothesis is important because, if true, it means that OHC electromotility improves hearing not by increasing vertical displacements of the organ of Corti, but by converting vertical displacement of the basilar membrane into radial fluid movement that can stimulate IHCs. Our studies will explicitly measure the role of the OHC by comparing the in vivo vibratory patterns of wild-type mice (normal OHC stiffness, normal electromotility), prestin 499 mice (normal OHC stiffness, no electromotility), and prestin null mice (decreased OHC stiffness, no electromotility). Aim 1 is to use our existing 1D-VOCTV system to study mice positioned at two different angles to measure both vertical and radial displacements throughout the organ of Corti. Aim 2 is to develop the optical technology and software to perform simultaneous 3D vibratory measurements for every voxel (3D-VOCTV). Aim 3 is use 3D-VOCTV in living mice to measure transverse, radial, and longitudinal motion. If our hypothesis is true, wild- type mice will demonstrate significantly largr radial and/or longitudinal displacements of the OHC-Deiter cell junction compared to dead wild-type, live prestin 499, and live prestin null mice. In addition, the frequency tuning of these displacements should be less sharp in prestin null mice compared to prestin 499 mice. The data obtained with this grant will likely explain the basis for the unique and highly structured anatomy of cells within the organ of Corti. The state-of-the-art technology developed with this grant is likely to become the new standard for making in vivo vibratory measurements.