Mechanical Signaling through Osteoblast Focal Adhesions

这项建议的总体目标是了解细胞机制，调解合成代谢反应 骨骼承受机械负荷的能力骨的机械负荷诱导骨内的间质液运动， 骨头内部的空间。流体对成骨细胞和骨细胞的机械刺激 剪切应力（FSS）被假设在骨对机械载荷的响应中起作用。支持 这一假说来自于观察到成骨细胞和骨细胞在FSS刺激下， 与保持在静态培养下的细胞相比， 条件本申请的中心焦点是确定介导细胞凋亡的细胞机制。 骨细胞对局部环境的机械敏感性。具体而言，我们建议研究 成骨细胞和成骨细胞之间的粘连部位（通常称为病灶接触或病灶粘连） 骨细胞与细胞外基质的结合是由整合素介导的细胞粘附分子调节的， 骨细胞对FSS的反应。这项研究的结果应该提供一个更好的理解， 介导骨细胞对机械力的反应的基本细胞和分子机制 通过测试局灶性粘连作为机械感受器通过协调 与整合素相互作用的细胞质信号分子的活性。生理相关反应， 骨细胞对单向和振荡流体流动的反应包括改变的增殖活性和增强的 向合成代谢或成骨细胞表型分化，改变基因表达，增加 前列腺素的产生、促分裂原活化蛋白激酶（MAPK）和粘着斑激酶的活化 (FAK)和胰岛素样生长因子受体（IGF-1 R）对IGF-1刺激的敏感性。三 提出了具体目标。在目标1中，我们将确定破坏焦点的结构完整性的影响。 粘附对成骨细胞对FSS生化反应的影响。在目标2中，我们将确定焦点的作用 粘着激酶（FAK）介导的信号转导途径激活的FSS的机械转导。在 目的3探讨转录因子NMP 4/CIZ在细胞信号转导中的作用 在流体剪切应力作用下，通过局部粘连激活的通路。这些研究应 提供了新的信息的细胞机制，介导骨mechanotransduction。

The overall goal of this proposal is understand the cellular mechanisms that mediate the anabolic response of bone to mechanical loading. Mechanical loading of bone induces the movement of interstitial fluid within the spaces inside bone. The resulting mechanical stimulation of osteoblasts and osteocytes caused by fluid shear stress (FSS) is hypothesized to play a role in the response of bone to mechanical loading. Support for this hypothesis comes from the observation that osteoblasts and osteocytes that are stimulated by FSS in vitro exhibit increased metabolic activity compared to cells that are maintained under static culture conditions. The central focus of this application is to determine the cellular mechanisms that mediate the mechanical sensitivity of bone cells to their local environment. Specifically, we propose to examine the role of adhesion sites (commonly referred to as focal contacts or focal adhesions) between osteoblasts and osteocytes to the extracellular matrix that are mediated by integrin cell adhesion molecules in regulating the response of bone cells to FSS. The results of this study should provide an improved understanding of the fundamental cellular and molecular mechanisms that mediate the response of bone cells to mechanical loading by testing the hypothesis that focal adhesions function as mechanoreceptors by coordinating the activity of cytoplasmic signaling molecules that interact with integrins. Physiologically relevant responses by bone cells to unidirectional and oscillatory fluid flow include altered proliferative activity and enhanced differentiation toward an anabolic or osteoblastic phenotype, altered gene expression, increased prostaglandin production, activation of mitogen activated protein kinases (MAPK) and focal adhesion kinase (FAK) and sensitization of the insulin-like growth factor receptor (IGF-1R) to stimulation by IGF-1. Three specific aims are proposed. In Aim 1 we will determine the effect of disrupting the structural integrity of focal adhesions on biochemical response of osteoblasts to FSS. In Aim 2 we will determine the role of focal adhesion kinase (FAK) mediated signal transduction pathways activated by FSS in mechanotransduction. In Aim 3 we will determine the role of the transcription factor NMP4/CIZ in mediating signal transduction pathways activated through focal adhesions in response to fluid shear stress. Together these studies should provide novel information on the cellular mechanisms that mediate mechanotransduction in bone.