Cytoskeletal Strain Amplification due to Bone Fluid Flow

描述（由申请人提供）：骨易于适应其机械 加载环境这种适应的“机械传感器”被广泛认为是 尽管实际的过程是未知的， 了解新骨形成的过程。然而，有一种新兴的 一致认为，应变诱导的组织液流动在这一过程中起着关键作用， 机械信号在这一建议中，我们提出了一个新的问题： 骨细胞对流体流动的“感知”受到 细胞周基质，具有横向细丝，既束缚细胞突起 并将流体动力学拖曳力传递到系绳上 纤维到细胞内肌动蛋白细胞骨架在细胞过程中？我们 试点研究揭示了这种横向的第一个明确的识别 桥接纤维和新的理论模型（You等人，（2001） 旨在定量探索这一假设。该模型使 值得注意的预测是，活骨中非常小的机械应变可以 在细胞水平上被放大100倍。如果验证通过，模型将解析 基本悖论这解释了为什么整个骨骼的组织水平应变可以 远小于所需的体外动态底物应变 引发细胞内的生化反应在建议的研究中，我们会 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 将细胞突起拴系到细胞突起的横向元件的分布 小管壁;（2）使用免疫组织化学染色技术， 填充细胞周围空间的蛋白多糖;（3）阐明结构 （4）在细胞的突起处形成肌动蛋白纤维束;（5）在细胞的突起处形成肌动蛋白纤维束。 用于预测细胞水平应变放大的理论模型， 由于细胞周围基质上的流体阻力，在细胞过程中发生。

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.