Regulation of osteoblast number by PTH

PTH 对成骨细胞数量的调节

• 批准号: 8445150
• 负责人: Robert L Jilka
• 金额: --
• 依托单位: CENTRAL ARKANSAS VETERANS HLTHCARE SYS
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8445150
• 关键词: Adult; Affect; Age-Related Bone Loss; Angiogenic Factor; Antibodies; Blood Vessels; Bone Matrix; Bone Resorption; Bone remodeling; Calcium; Cells; Development; Endothelial Cells; Equilibrium; Fracture; Funding; Future; Galactosidase; Gene Targeting; Genes; Goals; Growth Factor; Histologic; Hormonal; Hormones; Hyperparathyroidism; Hypoparathyroidism; Infusion procedures; Investigation; Kidney Diseases; Kidney Failure; Knockout Mice; Ligands; Link; Longevity; Longitudinal Studies; Marrow; Measurement; Measures; Mediating; Mesenchymal; Mesenchymal Stem Cells; Metabolism; Methodology; Methods; Minerals; Mission; Mus; Osteoblasts; Osteoclasts; Osteocytes; Osteogenesis; Osteoporosis; Parathyroid Hormone Receptor; Parathyroid gland; Pathway interactions; Patient Care; Patients; Peptides; Pericytes; Physiological; Postmenopause; Process; Production; Regulation; Research Design; Risk; Role; Secondary Hyperparathyroidism; Signal Pathway; Signal Transduction; Site; Stimulus; Surface; TNFSF11 gene; Transgenes; Vascular Endothelial Growth Factors; Veterans; Work; angiogenesis; base; bevacizumab; bone; bone loss; bone mass; calcification; cell motility; cytokine; dimer; mortality; mutant; neovascularization; osteoblast differentiation; osteogenic; overexpression; progenitor; promoter; public health relevance; receptor; receptor expression; red fluorescent protein; repaired; research study; response

DESCRIPTION (provided by applicant): Project Summary Parathyroid hormone (PTH) is the principal hormonal determinant of the rate of bone remodeling. The long term goal of this proposal is to determine the mechanism by which PTH stimulates the production of the appropriate number of osteoblasts needed to completely refill the resorption cavities created by osteoclasts during the remodeling process. PTH increases the formation of osteoclasts by stimulating the expression of receptor-activator of NFkB-ligand (RANKL). However, the PTH-generated signals stimulating the development of osteoblasts are poorly understood. During the previous funding period, we determined in mice that infusion of either PTH or soluble RANKL (sRANKL) for 5 days increases both osteoclast and osteoblast number, but the osteoblastogenic response to sRANKL is less than that of PTH. Whereas cancellous bone volume is maintained in mice receiving PTH, reflecting balanced remodeling, infusion of sRANKL causes a decrease in cancellous bone volume, indicating that remodeling was unbalanced in favor of resorption due to inadequate numbers of osteoblasts. The greater effect of PTH on osteoblastogenesis indicates that besides the PTH-stimulated RANKL-dependent stimulus, the hormone must activate additional pro-osteoblastogenic pathways. Importantly, we have also demonstrated that PTH acts directly on osteocytes to rapidly suppress the expression of sclerostin, a potent antagonist of pro-osteogenic Wnt signaling. Gene profiling revealed that PTH, but not sRANKL, affects the expression of several components of the Wnt signaling pathway as well as pro-angiogenic cytokines. Accordingly, PTH increased marrow vascularity, but sRANKL did not. Based on these studies, and the increasingly appreciated link between the vasculature and bone formation, we hypothesize that PTH increases osteoblastogenesis via three inter-related mechanisms. One depends on the RANKL-induced increase in osteoclast number and bone resorption, which in turn increases osteoblast number via release of pro-osteogenic growth factors from the bone matrix, or via secretion of growth factors from osteoclasts themselves, or both. The second mechanism involves PTH-induced activation of pro-osteoblastogenic Wnt signaling, caused at least in part by suppression of sclerostin. Third, PTH- stimulates an increase in pro-angiogenic factors and Wnt signaling, both of which are needed for the increased development of vessels necessary for the delivery of osteoclast and osteoblast progenitors to the bone remodeling site. The experiments of Specific Objective 1 will investigate the role of Wnt signaling in the increased osteoblast number and vascularity caused by infusion of PTH. These studies will be done using DMP1-Sost mice that overexpress sclerostin, mice lacking sclerostin, and mice expressing a constitutively active mutant of the PTH receptor specifically in osteocytes. Wnt signaling will be measured by quantification of known Wnt target genes. Detailed histologic measurement of Wnt signaling will also be done in mice expressing 2- galactosidase under the control of 2-catenin (BATgal mice), as well as in BATgal mice also expressing the DMP1-Sost transgene, or lacking Sost. To facilitate future investigations, a long-term effort will be launched to develop methodology for the isolation of the pre-osteoblast targets of PTH from adult bone. Specific objective 2 will investigate the role of neovascularization in the regulation of bone remodeling. The effect of an anti- vascular endothelial growth factor antibody (Bevacizumab), or a peptide (Anginex) that blocks endothelial cell migration on bone remodeling, will be quantified under normal physiologic conditions, and following stimulation of remodeling by administration of PTH or sRANKL.

描述（由申请人提供）： 项目摘要甲状旁腺激素（PTH）是骨重塑速率的主要激素决定因素。 该建议的长期目标是确定PTH刺激在重塑过程中完全补充破骨细胞产生的吸收腔所需的适当成骨细胞产生的机制。 PTH通过刺激NFKB配体（RANKL）的受体激活剂的表达来增加破骨细胞的形成。 但是，刺激成骨细胞发展的PTH生成的信号知之甚少。 在上一个资金期间，我们在小鼠中确定了5天的pth或可溶性RANKL（Srankl）的输注增加了成骨细胞和成骨细胞的数量，但对Srankl的成骨细胞源性反应小于PTH。 尽管在接收PTH的小鼠中保持了取消骨体积，反映了平衡的重塑，但Srankl的输注会导致取消骨体积的减少，这表明重塑是由于成骨细胞数量不足而导致的吸收不平衡的。 PTH对成骨细胞生成的影响更大，表明除了刺激了PTH刺激的RANKL依赖性刺激外，激素还必须激活其他促肌细胞基本生成途径。 重要的是，我们还证明了PTH直接作用于骨细胞上，以迅速抑制硬化蛋白的表达，这是促稳态Wnt信号传导的有效拮抗剂。 基因分析表明，PTH而不是Srankl会影响Wnt信号通路的几个组成部分以及促血管生成细胞因子的表达。 因此，PTH增加了骨髓的血管性，但Srankl并没有增加。 基于这些研究，以及脉管系统与骨形成之间越来越多的联系，我们假设PTH通过三种相关机制增加了成骨细胞生成。 一种取决于RANKL诱导的破骨细胞数量和骨吸收的增加，这又通过释放骨基质中的促稳态生长因子或通过分泌骨细胞本身或两者兼而有之增加了成骨细胞数量。 第二种机制涉及PTH诱导的促稳态Wnt信号的激活，至少部分是由于硬化蛋白的抑制作用而引起的。 第三，PTH-刺激促血管生成因子和Wnt信号的增加，这两种信号是增加了将整骨细胞和成骨细胞祖细胞递送到骨骼重塑位点所需的血管发展所需的。 特定目标1的实验将研究Wnt信号传导在由PTH输注引起的成骨细胞数和血管性增加中的作用。 这些研究将使用DMP1-SOST的小鼠进行过表达的硬化素，缺乏硬化蛋白的小鼠以及表达PTH受体组成型活性突变体的小鼠，该突变体在骨细胞中特别是在骨细胞中。 Wnt信号将通过定量已知Wnt靶基因来测量。 Wnt信号传导的详细组织学测量也将在2-catenin（Batgal小鼠）以及BATGAL小鼠的控制下表达2-半乳糖苷酶的小鼠以及表达DMP1-SOST转基因或缺乏SOST的BATGAL小鼠。 为了促进未来的研究，将发起长期的努力，以开发将PTH前骨细胞靶标与成人骨骼隔离的方法。 具体目标2将研究新血管形成在调节骨重塑调节中的作用。 在正常的生理条件下，将对抗血管内皮生长因子抗体（贝伐单抗）或阻断内皮细胞迁移的肽（Anginex）的作用，并在正常的生理条件下进行量化，并通过给药PTH或Srankl刺激重塑后。