Role of IGF-1 and Estrogen in Skeletal Anabolic Response to Loading

IGF-1 和雌激素在骨骼合成代谢反应中的作用

基本信息

批准号：
7576072
负责人：
Chandrasekhar Kesavan
金额：
$ 7.7万
依托单位：
LOMA LINDA VETERANS ASSN RESEARCH & EDUC
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-08-07 至 2011-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7576072
关键词：
Affect Age Animals Antibodies Architecture Asthma Attention Bone Density Candidate Disease Gene Cells Collagen Type I Congestive Heart Failure Data Development Disease Economic Burden Estrogen Receptors Estrogens Europe Exercise Forelimb Fracture Future Gene Expression Genes Genetic Enhancer Element Goals Grant Growth Growth Factor Hip region structure Histology Human In Vitro Incidence Insulin-Like Growth Factor I Insulin-Like-Growth Factor I Receptor Japan Knock-out Knockout Mice Label Lead Maintenance Measures Mechanical Stimulation Mechanics Mediating Mediator of activation protein Minerals Modeling Molecular Mus Osteoblasts Osteogenesis Osteoporosis Ovariectomy Pathway interactions Phase Phosphorylation Play Population Production Property Receptor Signaling Reporting Research Resistance Reverse Transcriptase Polymerase Chain Reaction Risk Role Signal Pathway Signal Transduction Skeletal Development Skeleton Skin Steam Stream Techniques Testing Time Transactivation Transgenic Mice Transgenic Organisms Vertebral column Western Blotting Woman Wrist alpha2 Chain Collagen Type I base bone bone cell bone loss bone mass bone quality bone strength clinically significant cost fluorexon in vivo indexing malignant breast neoplasm mouse model prevent promoter receptor expression response skeletal tibia transcription factor

项目摘要

DESCRIPTION (provided by applicant): Title: IGF-I as a mediator of skeletal anabolic response to loading It is well known that the development of skeletal architecture and maintenance of bone mass are dependent on mechanical stimulation. Although gene expression studies have revealed evidence for the involvement of several potential candidate genes as mediators of mechanical loading (ML) response, direct evidence for the involvement of these genes in mediating bone anabolic response to ML is lacking. In terms of potential mediators of ML response in the skeleton, Insulin like growth factor-I (IGF-I) has received considerable attention since IGF-I expression has been shown to increase rapidly in response to mechanical strain in bones in vivo and bone cells in vitro and since transgenic studies involving disruption of IGF-I gene have shown that IGF-I is a key bone formation regulator. Based on past findings and our preliminary data, we propose the hypothesis that ML induced increase in IGF-I expression interacts with estrogen to determine the amount of new bone formed in response to mechanical strain. To evaluate this hypothesis, we have proposed cause and effect relationship studies between IGF-I, estrogen and bone formation response to ML utilizing IGF-I conditional knockout (KO) mice in which IGF-I gene is disrupted using Cre/LoxP approach. We will generate IGF-I KO mice by crossing loxP IGF-I mice with transgenic Cre mice in which Cre expression is driven by promoter and enhancer elements of alpha2 chain of type I collagen promoter. ML will be induced by four-point bending in the tibia or axial compression of forelimb. In vivo pQCT and Real time RT-PCR will be used to quantitate changes in bone parameters (loaded and non-loaded bones) and gene expression, respectively. Three-point bending and micro-CT will be used to measure changes in the mechanical properties, and architecture in response to loading in both the KO and the control mice. Histology will be carried out using calcein-double labeling in order to measure bone formation rate, osteoblast cell population, mineral apposition rate, and osteoblast activity resulting from ML. To determine if estrogen interacts with IGF-I to regulate skeletal anabolic response to loading, control and IGF-I conditional KO mice will be ovariectomized and skeletal response to ML determined. Our understanding of the role of IGF-I and estrogen in mediating bone formation response to loading will lead to development of strategies to increase bone anabolic response to ML by modulating local IGF-I actions in bone.

描述（由申请人提供）：标题：IGF-I 作为骨骼合成代谢对负荷反应的调节剂众所周知，骨骼结构的发育和骨量的维持依赖于机械刺激。尽管基因表达研究已经揭示了一些潜在候选基因作为机械负荷（ML）反应介导者的证据，但缺乏这些基因参与介导机械负荷的骨合成代谢反应的直接证据。就骨骼中 ML 反应的潜在介质而言，胰岛素样生长因子-I (IGF-I) 受到了相当多的关注，因为 IGF-I 的表达已被证明会响应体内骨骼和骨细胞的机械应变而迅速增加体外和自从涉及 IGF-I 基因破坏的转基因研究表明 IGF-I 是关键的骨形成调节剂。根据过去的发现和我们的初步数据，我们提出了这样的假设：ML 诱导 IGF-I 表达增加与雌激素相互作用，以确定响应机械应变而形成的新骨量。为了评估这一假设，我们提出了利用 IGF-I 条件敲除 (KO) 小鼠（其中使用 Cre/LoxP 方法破坏 IGF-I 基因）对 IGF-I、雌激素和对 ML 的骨形成反应之间的因果关系进行研究。我们将通过将loxP IGF-I小鼠与转基因Cre小鼠杂交来产生IGF-I KO小鼠，其中Cre表达由I型胶原启动子的α2链的启动子和增强子元件驱动。 ML 将由胫骨四点弯曲或前肢轴向压缩引起。体内 pQCT 和实时 RT-PCR 将分别用于定量骨骼参数（负载和非负载骨骼）和基因表达的变化。三点弯曲和微型 CT 将用于测量 KO 小鼠和对照小鼠的机械性能和结构对负载的响应变化。将使用钙黄绿素双标记进行组织学检查，以测量 ML 产生的骨形成率、成骨细胞数量、矿物质沉积率和成骨细胞活性。为了确定雌激素是否与 IGF-I 相互作用来调节骨骼对负荷的合成代谢反应，将对照小鼠和 IGF-I 条件 KO 小鼠切除卵巢并确定对 ML 的骨骼反应。我们对 IGF-I 和雌激素在介导骨形成对负荷反应中的作用的理解将导致开发通过调节骨中局部 IGF-I 作用来增加对 ML 的骨合成代谢反应的策略。