Department of Mechanical Engineering, Howard University, Washington, DC, United States of America.
PLoS One. 2011 Mar 31;6(3):e18161. doi: 10.1371/journal.pone.0018161.
Mammalian hearing relies on a cochlear hydrodynamic sensor embodied in the inner hair cell stereocilia bundle. It is presumed that acoustical stimuli induce a fluid shear-driven motion between the tectorial membrane and the reticular lamina to deflect the bundle. It is hypothesized that ion channels are opened by molecular gates that sense tension in tip-links, which connect adjacent stepped rows of stereocilia. Yet almost nothing is known about how the fluid and bundle interact. Here we show using our microfluidics model how each row of stereocilia and their associated tip links and gates move in response to an acoustical input that induces an orbital motion of the reticular lamina. The model confirms the crucial role of the positioning of the tectorial membrane in hearing, and explains how this membrane amplifies and synchronizes the timing of peak tension in the tip links. Both stereocilia rotation and length change are needed for synchronization of peak tip link tension. Stereocilia length change occurs in response to accelerations perpendicular to the oscillatory fluid shear flow. Simulations indicate that nanovortices form between rows to facilitate diffusion of ions into channels, showing how nature has devised a way to solve the diffusive mixing problem that persists in engineered microfluidic devices.
哺乳动物的听觉依赖于内毛细胞纤毛束中体现的耳蜗流体动力传感器。据推测，声音刺激会引起盖膜和网状层之间的流体剪切驱动运动，从而使纤毛束发生偏转。有人假设，离子通道是由连接相邻阶梯状纤毛列的尖端连接的张力感知分子门打开的。然而，关于流体和纤毛束如何相互作用，人们几乎一无所知。在这里，我们使用我们的微流控模型展示了每一排纤毛及其相关的尖端连接和门在响应诱导网状层轨道运动的声学输入时是如何移动的。该模型证实了盖膜在听力中的重要作用，并解释了它如何放大和同步尖端连接中峰值张力的时间。为了实现尖端连接张力峰值的同步，需要纤毛旋转和长度变化。纤毛长度的变化是对垂直于振荡流体剪切流的加速度的响应。模拟表明，纳米涡旋在各行之间形成，以促进离子扩散到通道中，展示了大自然如何设计出一种方法来解决在工程微流控设备中仍然存在的扩散混合问题。
