Cytoskeletal Strain Amplification due to Bone Fluid Flow

描述（由申请人提供）：骨骼很容易适应其机械性能 加载环境。人们普遍认为这种适应的“机械传感器” 成为骨细胞，尽管实际过程既未知又至关重要 了解新骨形成的过程。然而，有一种新兴的 一致认为应变引起的间质液流动在此过程中起着关键作用 机械信号。在本提案中，我们解决了一个新问题： 骨细胞对流体流动的“感知”受到存在的影响 具有束缚细胞过程的横向丝的细胞周基质 到小管壁并在系绳上传递流体动态阻力 细胞过程中细胞内肌动蛋白细胞骨架的细丝？我们的 试点研究首次明确识别出这种横向 桥接纤维和新的理论模型（You et al., 2001）已被 旨在定量探索这一假设。该模型使得 引人注目的预测是，活骨中非常小的机械应变可以 在细胞水平上放大100倍。如果经过验证，该模型将解决 根本悖论。它解释了为什么整个骨骼的组织水平应变可以 比体外测量的动态底物菌株所需的小得多 引发细胞内生化反应。在拟议的研究中，我们将 实验验证和测量所需的基本生物元素 这个新模型。特别是，我们将：（1）表征间距和 将细胞过程束缚到的横向元件的分布 泪小管壁； (2)利用免疫组织化学染色技术进行鉴定， 充满细胞周围空间的蛋白多糖； (3)阐明结构 填充细胞突起的肌动蛋白丝束； (4) 细化 用于预测细胞水平应变放大的理论模型 由于细胞周基质上的流体阻力而发生在细胞过程中。

DESCRIPTION (provided by applicant): Bone adapts readily to its mechanical loading environment. The "mechanosensor" for this adaptation is widely believed to be the osteocyte, though the actual process is both unknown and critical to understanding the process of new bone formation. However, there is an emerging consensus that strain-induced interstitial fluid flow plays a key role in this mechanical signaling. In this proposal we address a new question: How would the osteocyte "perception" of fluid flow be influenced by the presence of a pericellular matrix with transverse filaments that both tether the cell process to the canalicular wall and transmit fluid dynamic drag forces on the tethering filaments to the intracellular actin cytoskeleton in the cell processes? Our pilot studies have revealed the first clear identification of such transverse bridging fibers and a new theoretical model (You et al., 2001) has been developed to quantitatively explore this hypothesis. This model makes the remarkable prediction that the very small mechanical strains in live bone can be amplified 100-fold at the cellular level. If validated, the model resolves a fundamental paradox. It explains why tissue level strains in whole bone can be so much smaller than that measured in vitro dynamic substrate strains required to elicit intracellular biochemical responses. In the proposed studies, we will experimentally verify and measure the essential biological elements required by this new model. In particular, we will: (1) characterize the spacing and distribution of the transverse elements that tether the cell process to the canalicular wall; (2) identify, using immunohistochemical staining techniques, the proteoglycans that fill the pericellular space; (3) elucidate the structure of the actin filament bundle that fills the cell process; and (4) refine the theoretical model for predicting the cellular level strain amplification that occurs in the cell process due to the fluid drag on the pericellular matrix.