Mechanical Loading of Bone and Prostaglandins

骨和前列腺素的机械负荷

• 批准号: 7259333
• 负责人: CAROL C. PILBEAM
• 金额: $ 31.62万
• 依托单位: UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-11 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7259333
• 关键词: Mechanical; Loading; Bone; Prostaglandins

DESCRIPTION (provided by applicant): Mechanical loading of bone maintains bone mass and skeletal integrity. Loading stimulates new bone formation and unloading causes bone loss. Cyclooxygenase (COX)-2, the major enzyme for prostaglandin (PG) responses in bone, can enhance both bone formation and resorption and may mediate some effects of either loading or unloading. Our overall goal is to understand how mechanical signals are transmitted into biochemical signals and the role of COX-2 in these processes. Mechanical strains in bone can generate interstitial fluid flow that exerts fluid shear stress (FSS) on cells and induces COX-2. Because in vivo studies suggest that effects of short duration loading are not improved by longer duration, we believe the signaling cascade after removal of FSS will be important for determining outcomes of loading. In vitro, we will examine responses of COX-2, and selected other genes important for bone turnover, in osteoblastic and osteocytic cells during and after stopping FSS. We will determine if the protein kinase D (PKD) pathway mediates the FSS induction of COX-2 via activation of ERK after stopping FSS; if the transcription factors Cbfa1 (Runx2) and NFAT are mediators of the FSS induction of COX-2 transcription; and if the development of COX-2 expression after FSS also depends on regulation of mRNA stability. We will assess the role of COX-2 produced PGs, induced by FSS, in FSS effects on other genes using nonsteroidal anti-inflammatory drugs (NSAIDs) and cells derived from Cox-2+/+ and Cox-2-/- mice. In vivo, we will study effects of dynamic axial loading of the ulnae and effects of unloading of hind limbs by tail suspension. We will use mice with Cox-2 deletion conditionally targeted to osteoblastic and osteocytic cells with the 2.3-kb Co1a1 promoter driving Cre recombinase (Col1a1-Cre) or the 2.3-kb Col1a1 promoter driving Cre recombinase fused to a mutated ligand binding domain of the estrogen receptor (Col1a1-CreERT2), which becomes active only after administration of the synthetic estrogen antagonist 4-hydroxy-tamoxifen. We will examine potential compensation by cyclooxygenase (COX)-1 for absent COX-2 by comparing targeted Cox-2 deletion in Cox- 1+/+ and Cox-1-/- mice. We will measure bone gain or loss and gene expression at intervals after loading or unloading to determine effects of Cox-2 deletion (+/- Cox-1 deletion) on the response of other genes that may mediate effects of loading and unloading. Public health relevance: Physical activity that mechanically loads bone can increase bone mass and decrease bone loss. Osteoporosis, associated with bone loss and leading to debilitating skeletal fractures, increases with age and physical inactivity. A better understanding of how mechanical loading regulates bone may help us to develop better therapies for prevention and treatment of osteoporosis.

描述(申请人提供)：骨的机械负荷保持骨量和骨骼的完整性。负荷会刺激新骨形成，而卸载会导致骨丢失。环氧合酶-2(COX-2)是骨中前列腺素(PG)反应的主要酶，可促进骨形成和骨吸收，并可能介导负荷或卸载的某些效应。我们的总体目标是了解机械信号是如何传递到生化信号中的，以及COX-2在这些过程中的作用。骨骼中的机械应变可产生间质流体流动，对细胞施加流体剪应力(FSS)，并诱导COX-2。由于体内研究表明，较长的持续时间并不能改善短时间负荷的效果，我们认为去除FSS后的信号级联对于决定负荷的结果将是重要的。在体外，我们将检测COX-2在成骨细胞和成骨细胞中和停止FSS后的反应，并选择其他对骨转换重要的基因。我们将确定蛋白激酶D(PKD)通路是否通过在FSS停止后激活ERK来介导FSS对COX-2的诱导；转录因子Cbfa1(Runx2)和NFAT是否是FSS诱导COX-2转录的中介；以及FSS后COX-2表达的发展是否也依赖于对mRNA稳定性的调节。我们将评估由FSS诱导的COX-2产生的PG在使用非类固醇抗炎药(NSAIDs)的FSS对其他基因以及COX-2+/+和COX-2-/-小鼠来源的细胞的FSS作用中的作用。在体内，我们将研究尺骨的动态轴向载荷和尾部悬吊卸载对后肢的影响。我们将使用COX-2缺失的小鼠，有条件地针对成骨细胞和成骨细胞，其中2.3kb的Co1a1启动子驱动Cre重组酶(Col1a1-Cre)，或2.3kb的Col1a1启动子驱动Cre重组酶与雌激素受体的突变配体结合域(Col1a1-CreERT2)融合，只有在注射合成雌激素拮抗剂4-羟基他莫昔芬后，它才变得活跃。我们将通过比较COX-1+/+和COX-1-/-小鼠中COX-2的靶向缺失来检测COX-1对缺失COX-2的潜在补偿作用。我们将在加载或卸载后每隔一段时间测量骨得失和基因表达，以确定COX-2缺失(+/-COX-1缺失)对可能介导加载和卸载效应的其他基因反应的影响。与公众健康相关：机械负荷骨的体力活动可以增加骨量，减少骨丢失。骨质疏松症与骨丢失相关，并导致衰弱的骨骼骨折，随着年龄和缺乏运动而增加。更好地了解机械负荷如何调节骨骼可能有助于我们开发更好的治疗方法来预防和治疗骨质疏松症。