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Importance of Beta-Catenin Signaling in Osteocytes Associated with Anabolic Load

与合成代谢负荷相关的骨细胞中 β-连环蛋白信号传导的重要性

基本信息

批准号：
8311674
负责人：
Shiva Prasad Kotha
金额：
$ 29.73万
依托单位：
RENSSELAER POLYTECHNIC INSTITUTE
依托单位国家：
美国
项目类别：
财政年份：
2008
资助国家：
美国
起止时间：
2008-09-01 至 2015-05-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8311674
关键词：
Adult Affect Biochemical Biological Bone Matrix Bone Resorption Bone Surface Cell Nucleus Cells Data Dimensions Dinoprostone Disease Down-Regulation Enzymes Exhibits Failure Finite Element Analysis Forearm Foundations Fracture Galactosidase Gene Expression Gene Proteins Genes Glycogen Synthase Kinase 3 Health Health Care Costs Homeostasis Immunohistochemistry Individual Knock-out Knockout Mice Laboratories Lead Lithium Chloride Location Mechanical Stress Mechanics Mediating Modeling Molecular Mus Mutation Oranges Osteoblasts Osteocytes Osteogenesis Osteoporosis Pathway interactions Pattern Phosphorylation Physical activity Play Population Prostaglandins Proteins Regulation Reporter Research Risk Role Signal Transduction Signaling Molecule Site Skeleton Stimulus Structure Surface Testing Thinking Transgenic Organisms Translating Up-Regulation Work base beta catenin bone bone cell bone mass cell type dosage experience fluid flow in vivo in vivo Model inhibitor/antagonist insight novel prevent protein expression response shear stress three-dimensional modeling

项目摘要

DESCRIPTION (provided by applicant): Osteoporosis is a debilitating disease that affects 75 million people worldwide with an estimated $48 billion in healthcare costs. A major determinant of bone mass is the mechanical loading to which the skeleton is subjected during daily activity, which stimulates adaptive modeling. Osteocytes, cells embedded in the bone matrix, are thought to be responsible for sensing and coordinating adaptive responses in the skeleton. In response to mechanical loading, osteocytes at sites experiencing high mechanical stimulus appear to be the initial perceivers of applied load and to translate this force into early biochemical signals that lead to bone formation. However, little is currently known about how these cells individually and collectively sense and integrate strains perceived over the entire bone in order to initiate site-specific adaptive modeling responses. Wnt signaling mediated by sclerostin and b-catenin, molecules that negatively and positively influence the Wnt/b-catenin pathway, clearly plays an important role in bone formation. Our preliminary data suggests that b-catenin is rapidly activated in osteocytes following mechanical loading. Our data also suggests that the load signal is propagated to adjacent cells, to sites where sclerostin protein expression is down regulated. Based on this, our overall hypothesis is that b-catenin signaling is controlled by magnitude of mechanical stimulus in a subset of osteocytes that activate the pathway followed by its subsequent propagation to adjacent regions when Sost becomes down regulated. In this application, we propose to use b-catenin signaling and Sost expression as readouts to determine how a driver of bone formation (b-catenin) and its negative regulator (Sost, an osteocyte specific molecule) are controlled by mechanical loading in osteocytes within a three dimensional mechanically responsive bone model. This in vivo model integrates strain or fluid flow shear stress magnitudes as the mechanical stimulus (a cause) with reporter activity or gene expression (a mechanism) with bone formation, a biological response (an effect). The following specific aims are proposed, Aim 1). Determine the temporal and spatial activation of the b-catenin pathway in response to anabolic load, Aim 2). Determine the temporal and spatial down regulation of Sost expression in response to anabolic load, and Aim 3). Determine the effects of increasing or decreasing b-catenin signaling on Sost/sclerostin expression and mechanical stimulus thresholds required to induce bone formation. We propose that increasing the basal level of b-catenin activity decreases the threshold of mechanical stimulus required to elicit bone formation in response to load and vice versa. Changes in b-catenin activity and Sost/sclerostin expression will be correlated with strain or fluid flow shear stress magnitudes in 3 dimensions. Thinking and visualizing bone responses to mechanical load in 3 dimensions instead of 2 dimensions will provide novel insights into how bone responds to load and will contribute to our understanding of the fundamental relationship between strain and bone cell responses. PUBLIC HEALTH RELEVANCE. Osteoporosis, a disease of low bone mass, is a debilitating disease that afflicts 75 million people worldwide with an estimated $48 billion in healthcare costs. A major determinant of bone mass is the mechanical loading to which the skeleton is subjected during daily activity, which stimulates adaptive modeling. Osteocytes, cells embedded in the bone matrix, are thought to be responsible for sensing and coordinating adaptive responses in the skeleton. In this application, we evaluate the dosage of a pharmacological agent (lithium chloride) that can synergize with mechanical loading to activate a powerful pathway (the Wnt/b-catenin signaling) in osteocytes such that it leads to bone formation occurring at sites of peak mechanical stresses. It is noted that failure to enhance bone formation at these sites can result in bone fractures. We also evaluate the activation of molecules that are involved in the pathway and show the activation of these molecules and bone formation in relationship to sites of peak mechanical stimuli in three dimensions. Therefore, this research is important in building an insightful foundation for regulation of bone mass by mechanical loading and in evaluating molecular pathways to reduce fracture risk.

描述（由申请人提供）：骨质疏松症是一种使人衰弱的疾病，影响着全世界 7500 万人，估计造成 480 亿美元的医疗费用。骨量的一个主要决定因素是骨骼在日常活动中承受的机械负荷，这会刺激适应性建模。骨细胞是嵌入骨基质中的细胞，被认为负责感知和协调骨骼中的适应性反应。为了响应机械负荷，经历高机械刺激部位的骨细胞似乎是施加负荷的最初感知者，并将这种力转化为导致骨形成的早期生化信号。然而，目前人们对这些细胞如何单独和集体感知和整合整个骨骼感知的应变以启动特定部位的适应性建模反应知之甚少。由硬化素和β-连环蛋白介导的Wnt信号传导，对Wnt/b-连环蛋白途径产生负面和正面影响的分子，显然在骨形成中发挥着重要作用。我们的初步数据表明，机械负荷后，b-连环蛋白在骨细胞中迅速激活。我们的数据还表明，负载信号传播到相邻细胞，传播到硬化素蛋白表达下调的位点。基于此，我们的总体假设是，b-连环蛋白信号传导受骨细胞子集中机械刺激强度的控制，当 Sost 下调时，骨细胞激活该通路，随后传播到邻近区域。在此应用中，我们建议使用b-连环蛋白信号传导和Sost表达作为读数，以确定骨形成驱动因素（b-连环蛋白）及其负调节剂（Sost，一种骨细胞特异性分子）如何通过三维机械响应骨模型中骨细胞的机械负载来控制。该体内模型将应变或流体流动剪切应力大小作为机械刺激（原因）与报告活性或基因表达（机制）与骨形成（生物反应（效果））相结合。提出以下具体目标：目标 1)。确定 β-连环蛋白途径响应合成代谢负荷的时间和空间激活，目标 2)。确定 Sost 表达响应合成代谢负荷的时间和空间下调，以及目标 3)。确定增加或减少 β-连环蛋白信号传导对 Sost/sclerostin 表达和诱导骨形成所需的机械刺激阈值的影响。我们建议增加β-连环蛋白活性的基础水平会降低响应负载而引发骨形成所需的机械刺激的阈值，反之亦然。 b-连环蛋白活性和 Sost/硬化蛋白表达的变化将与 3 维应变或流体流动剪切应力大小相关。在 3 维而不是 2 维中思考和可视化骨骼对机械负载的反应将为骨骼如何响应负载提供新的见解，并将有助于我们理解应变和骨细胞反应之间的基本关系。公共卫生相关性。骨质疏松症是一种骨量低的疾病，是一种使人衰弱的疾病，困扰着全世界 7500 万人，估计造成 480 亿美元的医疗费用。骨量的一个主要决定因素是骨骼在日常活动中承受的机械负荷，这会刺激适应性建模。骨细胞是嵌入骨基质中的细胞，被认为负责感知和协调骨骼中的适应性反应。在此应用中，我们评估了一种药物（氯化锂）的剂量，该药物可以与机械负荷协同作用，激活骨细胞中的强大途径（Wnt/b-连环蛋白信号传导），从而导致在峰值机械应力部位发生骨形成。值得注意的是，如果不能增强这些部位的骨形成，可能会导致骨折。我们还评估了参与该途径的分子的激活，并显示了这些分子的激活和骨形成与三维峰值机械刺激位点的关系。因此，这项研究对于为机械负荷调节骨量奠定深入的基础以及评估降低骨折风险的分子途径具有重要意义。