Osteocyte control of bone formation via Sost

骨细胞通过Sost控制骨形成

• 批准号: 8003291
• 负责人: Teresita M. Bellido
• 金额: $ 7.67万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-03-01 至 2010-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8003291
• 关键词: Adult; Affect; Anabolism; Antibodies; Apoptosis; Attenuated; Calvaria; Catabolism; Cell Culture Techniques; Cell Lineage; Cells; Chronic; Development; Dietary Calcium; Disease; Event; Exhibits; Gene Expression; Genes; Genetic; Hormonal; Hormones; Human; Hyperparathyroidism; In Vitro; Infusion procedures; Inherited; Injection of therapeutic agent; Knock-out; Knockout Mice; Mechanical Stimulation; Mechanics; Mediating; Mediator of activation protein; Mesenchymal Stem Cells; Messenger RNA; Modeling; Molecular; Mus; Osteoblasts; Osteocytes; Osteogenesis; Parathyroid Hormone Receptor; Parathyroid Hormones; Phenotype; Regulation; Research Personnel; Signal Pathway; Signal Transduction; Stimulus; Stretching; Testing; Transgenes; Transgenic Mice; Transgenic Organisms; Van Buchem disease; Work; base; bone; bone mass; bone strength; fluid flow; human PTH protein; in vivo; novel; novel therapeutic intervention; osteogenic; overexpression; parathyroid hormone-related protein; prevent; response; skeletal; spatial relationship; transcription factor; ulna

DESCRIPTION (provided by applicant): Recent compelling evidence demonstrates that sclerostin - the product of the Sost gene exclusively expressed by osteocytes in bone - antagonizes the pro-osteoblastogenic actions of Wnts and BMPs; providing a long-sought molecular means by which osteocytes regulate bone formation. Work leading to this application by the PI and collaborators demonstrated that chronic elevation of parathyroid hormone (PTH) potently decreases Sost/sclerostin expression in osteocytes in vivo and in vitro, suggesting a novel mechanism for PTH-dependent osteoblastogenesis mediated by osteocytes. Mechanical loading also increases osteoblast number; and a potential mediator of this anabolic effect is PTH related peptide (PTHrP), as its expression is increased by mechanical stimulation. Notably, Sost expression in inhibited by mechanical stimuli in vitro and by bone loading in vivo. Moreover, transgenic mice overexpressing a constitutively active PTH 1 receptor (PTHR1) exclusively in osteocytes (DMP1-caPTHR1) exhibit decreased Sost expression and a remarkable increase in bone mass. Based on these lines of evidence, it is hypothesized that activation of PTHR1 signaling in osteocytes leads to a rapid and direct inhibition of Sost gene expression, which, in turn, is responsible for increased bone formation in response to systemic elevation of PTH as well as to bone loading through local increase in PTHrP. This hypothesis will be tested by a combination of in vitro studies using osteocytes generated in vitro and authentic osteocytes, and in vivo approaches using transgenic and knock out mice. Studies in Aim 1 will elucidate the signaling pathways responsible by the rapid inhibition of Sost expression by PTH and PTHrP. In Aim 2, it will be determined whether suppression of Sost expression in vitro by mechanical stimulation induced by stretching or oscillating fluid flow requires PTHR1 signaling and PTHrP; and whether the decreased sclerostin expression by bone loading is spatially related to increased PTHrP and increased bone formation using the model of ulna loading in mice. In Aim 3, the consequences of PTHR1 activation or deletion in osteocytes in vivo will be established by complementary transgenic and knock out approaches. It will be also examined whether the osteogenic response induced by PTH elevation or loading, or the high bone mass phenotype of DMP1- caPTHRI mice are reversed, or at least ameliorated, by Sost overexpression or by blocking the Wnt signaling pathway. Furthermore, it will be established whether the reduction in Sost expression and the osteoblastogenic response to PTH or mechanical loading are abrogated in mice in which the PTHR1 is knocked out specifically in osteocytes (DMP1-10kb-Cre/PTHR1 mice). These studies will advance understanding of the control of bone formation by osteocytes and will elucidate the contribution of these cells to the osteoblastogenic actions of PTH, PTHrP, and mechanical stimuli. We expect that this work will provide opportunities for the development of novel therapeutic approaches leading to bone anabolism through actions on osteocytes.

描述（由申请人提供）：最近令人信服的证据表明，硬化素（骨骼中骨细胞专门表达的 Sost 基因的产物）可拮抗 Wnt 和 BMP 的促成骨细胞作用；提供了一种长期寻求的骨细胞调节骨形成的分子手段。 PI 和合作者进行这项应用的工作表明，甲状旁腺激素 (PTH) 的慢性升高可有效降低体内和体外骨细胞中 Sost/硬化蛋白的表达，这表明骨细胞介导的 PTH 依赖性成骨细胞生成的新机制。机械负荷也会增加成骨细胞数量；这种合成代谢作用的潜在调节剂是 PTH 相关肽 (PTHrP)，因为机械刺激会增加其表达。值得注意的是，Sost 表达受到体外机械刺激和体内骨负荷的抑制。此外，仅在骨细胞（DMP1-caPTHR1）中过表达组成型活性 PTH 1 受体（PTHR1）的转基因小鼠表现出 Sost 表达降低和骨量显着增加。基于这些证据，推测骨细胞中 PTHR1 信号的激活会导致 Sost 基因表达的快速和直接抑制，这反过来又导致骨形成增加，以响应 PTH 的全身升高以及通过 PTHrP 的局部增加来增加骨负荷。这一假设将通过使用体外产生的骨细胞和真实骨细胞的体外研究以及使用转基因和基因敲除小鼠的体内方法的组合来检验。目标 1 的研究将阐明 PTH 和 PTHrP 快速抑制 Sost 表达的信号传导途径。在目标 2 中，将确定拉伸或振荡流体流诱导的机械刺激在体外抑制 Sost 表达是否需要 PTHR1 信号传导和 PTHrP；以及使用小鼠尺骨负荷模型，骨负荷导致的硬化素表达减少是否与 PTHrP 增加和骨形成增加在空间上相关。在目标 3 中，将通过互补的转基因和敲除方法确定体内骨细胞中 PTHR1 激活或缺失的后果。还将检查由 PTH 升高或负载诱导的成骨反应，或 DMP1-caPTHRI 小鼠的高骨量表型是否通过 Sost 过表达或通过阻断 Wnt 信号通路而逆转或至少改善。此外，将确定在骨细胞中特异性敲除 PTHR1 的小鼠（DMP1-10kb-Cre/PTHR1 小鼠）中，Sost 表达的减少以及对 PTH 或机械负荷的成骨细胞反应是否被消除。这些研究将增进对骨细胞控制骨形成的理解，并将阐明这些细胞对 PTH、PTHrP 和机械刺激的成骨作用的贡献。我们期望这项工作将为开发新的治疗方法提供机会，通过对骨细胞的作用导致骨合成代谢。

项目成果

Bisphosphonate binding affinity affects drug distribution in both intracortical and trabecular bone of rabbits.

双膦酸盐结合亲和力影响药物在兔子皮质内和小梁骨中的分布。

• DOI: 10.1007/s00223-012-9570-0
• 发表时间: 2012
• 期刊: Calcified tissue international
• 影响因子: 4.2
• 作者: Turek,John;Ebetino,FHal;Lundy,MarkW;Sun,Shuting;Kashemirov,BorisA;McKenna,CharlesE;Gallant,MaximeA;Plotkin,LilianI;Bellido,Teresita;Duan,Xuchen;Triffitt,JamesT;Russell,RGrahamG;Burr,DavidB;Allen,MatthewR
• 通讯作者: Allen,MatthewR