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

• 批准号: 7687721
• 负责人: Shiva Prasad Kotha
• 金额: $ 4.39万
• 依托单位: UNIVERSITY OF CONNECTICUT STORRS
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7687721
• 关键词: Adult; Affect; Biochemical; Biological; Bone Matrix; Bone Resorption; Bone Surface; Cell Nucleus; Cells; Daily; Data; Dimensions; Dinoprostone; Disease; Down-Regulation; Enzymes; Exhibits; Failure; Figs - dietary; Finite Element Analysis; Forearm; Foundations; Fracture; Galactosidase; Gene Expression; Gene Proteins; Genes; Glycogen Synthase Kinase 3; Health Care Costs; Homeostasis; Immunohistochemistry; Individual; Knock-out; Knockout Mice; Laboratories; Lead; Lithium Chloride; Location; Mechanical Stress; Mechanics; Mediating; Modeling; Molecular; Mus; Mutation; Numbers; Oranges; Osteoblasts; Osteocytes; Osteogenesis; Osteoporosis; Pathway interactions; Pattern; Phosphorylation; Physical activity; Play; Population; Prostaglandins; Proteins; Public Health; Regulation; Reporter; Research; Risk; Role; Signal Transduction; Signaling Molecule; Site; Skeleton; Stimulus; Structure; Surface; Testing; Thinking; Transcriptional Activation; Transgenic Organisms; Translating; Up-Regulation; Work; base; beta catenin; bone; bone cell; cell type; dosage; experience; fluid flow; follow-up; in vivo; in vivo Model; inhibitor/antagonist; insight; novel; prevent; protein expression; response; shear stress; three-dimensional modeling

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）：骨质疏松症是一种令人衰弱的疾病，影响了全球7500万人，估计有480亿美元的医疗保健费用。骨骼质量的主要决定因素是在日常活动中对骨骼进行的机械载荷，从而刺激自适应建模。骨基质中嵌入骨基质中的细胞，被认为是造成骨骼中适应性反应的原因。为了响应机械载荷，在高机械刺激的位点的骨细胞似乎是施加载荷的初始感知器，并将这种力转化为早期的生化信号，导致骨形成。但是，目前，对于这些细胞如何单独和集体地感知和整合整个骨骼的菌株以启动特定地点的自适应建模响应，几乎没有知之甚少。由硬化蛋白和B-catenin介导的Wnt信号传导，对Wnt/B-catenin途径产生负面和积极影响的分子显然在骨形成中显然起着重要作用。我们的初步数据表明，在机械载荷后，B-catenin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的细胞，以及调节硬化蛋白表达的位点。基于这一点，我们的总体假设是，在骨细胞的一部分中，B-catenin信号传导受到机械刺激的大小控制，这些骨细胞激活了途径，随后在SOST下降时，其随后向相邻区域传播。在此应用中，我们建议使用B-catenin信号传导和SOST表达作为读数，以确定骨形成的驱动器（B-catenin）及其阴性调节剂（SOST，SOST，骨细胞特异性分子）如何通过机械载荷在三维机械响应的机械响应效果骨模型中的机械负载来控制。该体内模型将应变或流体流动剪切应力幅度整合为具有报告基因活性或基因表达的机械刺激（原因）（一种机制（一种机制），具有骨形成，一种生物学反应（效应）。提出了以下特定目标，目标1）。确定B-catenin途径的时间和空间激活响应合成代谢负载，AIM 2）。确定响应合成代谢负载的时间和空间降低表达的速度表达，然后AIM 3）。确定增加或减少B-catenin信号传导对诱导骨形成所需的SOST/硬化蛋白表达和机械刺激阈值的影响。我们建议，增加B-catenin活性的基础水平会降低引起骨骼形成载荷所需的机械刺激的阈值，反之亦然。 B-catenin活性的变化和SOST/硬化蛋白表达的变化将与3维中的应变或流体流动剪切应力幅度相关。思考和可视化对机械负荷的骨头反应在3个维度而不是2个维度上将提供有关骨骼如何响应负载的新见解，并将有助于我们对菌株和骨细胞反应之间的基本关系的理解。公共卫生相关性。骨质疏松症是一种低骨肿块的疾病，是一种使人衰弱的疾病，在全球范围内遭受了7500万人的疾病，估计有480亿美元的医疗保健费用。骨骼质量的主要决定因素是在日常活动中对骨骼进行的机械载荷，从而刺激自适应建模。骨基质中嵌入骨基质中的细胞，被认为是造成骨骼中适应性反应的原因。在此应用中，我们评估了可以与机械负载协同作用的药理学剂（氯化锂）的剂量，以激活骨细胞中强大的途径（Wnt/B-catenin信号传导），从而导致在峰值机械应力的位点会导致骨形成。值得注意的是，无法在这些部位增强骨形成会导致骨折。我们还评估了参与途径中涉及的分子的激活，并显示了这些分子和骨形成与三维峰值机械刺激部位的激活。因此，这项研究对于通过机械载荷和评估分子途径来降低断裂风险的分子途径来为骨量调节的洞察力很重要。