Role of EGFR signaling in bone formation and the anabolic actions of PTH

EGFR 信号传导在骨形成中的作用和 PTH 的合成代谢作用

• 批准号: 8580029
• 负责人: Ling Qin
• 金额: $ 34.8万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-10 至 2018-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8580029
• 关键词: Adult; Age-Related Bone Loss; Amphiregulin; Animal Model; Biological Assay; Bone Diseases; Bone Marrow; Bone Regeneration; Bone Surface; Cell Culture Techniques; Cell Lineage; Cells; Chemotactic Factors; Clinical; Commit; Conditioned Culture Media; Data; Defect; Development; Disease; EGF gene; Economic Burden; Epidermal Growth Factor Receptor; Fracture; Fracture Healing; Genes; Growth; Healthcare Systems; Hormones; In Vitro; Injection of therapeutic agent; Knockout Mice; Knowledge; Label; Lead; Ligands; Measurement; Mechanics; Mediating; Mesenchymal; Mesenchymal Stem Cells; Mus; Osteoblasts; Osteocytes; Osteogenesis; Osteoporosis; Parathyroid gland; Phenotype; Physiological; Play; Population; Proteins; Public Health; Receptor Signaling; Recruitment Activity; Research; Role; Signal Pathway; Signal Transduction; Staging; Stem cells; Testing; Therapeutic; Time; Transplantation; X-Ray Computed Tomography; bone; bone mass; bone turnover; cell motility; gene therapy; in vivo; interest; long bone; migration; nestin protein; novel; novel therapeutics; osteoblast differentiation; osteogenic; osteoprogenitor cell; prevent; progenitor; promoter; public health relevance; response; skeletal; stem cell biology; substantia spongiosa; therapy design; tissue regeneration; tool; transcription factor; translational medicine; trend

DESCRIPTION (provided by applicant): Intermittent parathyroid hormone (PTH) injection is one of the most effective anabolic treatments for osteoporosis because of its remarkable actions on bone formation. Osteoblasts are derived from mesenchymal progenitors, including mesenchymal stem cells (MSCs) and committed osteoprogenitors. Multiple mechanisms have been proposed to explain how PTH exerts its beneficial effects, but whether these effects include, or are mediated by, a stimulation of bone marrow mesenchymal progenitor activities, is not clear. Our new data support this mechanism by demonstrating the presence of a functionally distinct population of mesenchymal progenitors within the trabecular bone that are very responsive to PTH. PTH strongly stimulates the expression of amphiregulin, an epidermal growth factor receptor (EGFR) ligand, in osteoblasts and osteocytes. EGFR is highly expressed in mesenchymal progenitors and its activation stimulates proliferation, survival, and migration of these cells. Our preliminary data show that blocking EGFR activity in mice leads to defective bone formation and an osteopenic phenotype which are accompanied by a reduction in the number of mesenchymal progenitors. Interestingly, conditioned media from PTH-treated osteoblastic cells chemoattract mesenchymal progenitors in an amphiregulin-EGFR-dependent manner. Moreover, mice with deficient EGFR activity in osteoblast lineage cells have a poor anabolic response to PTH injection. These and other data lead to our central hypothesis that EGFR signaling is an essential regulator of bone marrow mesenchymal progenitors and mediates at least in part the anabolic effects of intermittent PTH administration. We will test our central hypothesis by pursuing the following aims: 1) investigate whether EGFR inactivation in MSCs inhibits bone formation and the anabolic response to PTH by assessing skeletal phenotypes of conditional EGFR knockout mice with a nestin promoter-driven inducible Cre with or without PTH treatment; 2) elucidate whether EGFR plays a critical role in maintaining the bone marrow mesenchymal progenitor population under conditions of normal and PTH-induced bone formation. We will use animal models with deficient EGFR activity in mesenchymal progenitors at different stages of lineage commitment to investigate the relationship between EGFR activity and mesenchymal progenitor populations residing in different regions of the long bone. We will also use cell culture approaches to determine whether a group of transcription factors, Egrs, mediates and regulates EGFR-stimulated proliferation and survival of mesenchymal progenitors; 3) determine whether EGFR signaling activated by PTH injection recruits mesenchymal progenitors toward the bone surface by using an in vivo transplantation approach, in which GFP-labeled mesenchymal progenitors can be visualized. Completion of these three aims will enable us to determine for the first time the role of EGFR in bone formation and the anabolic response of bone to the osteoporosis therapy PTH. Long-term, we seek to determine whether we can target EGFR signaling as a novel anabolic strategy to treat osteoporosis and other bone-related diseases.

说明(申请人提供)：间歇性甲状旁腺激素(PTH)注射是治疗骨质疏松症最有效的合成代谢疗法之一，因为它对骨形成有显著作用。成骨细胞来源于间充质祖细胞，包括间充质干细胞(MSCs)和定向成骨前体细胞。已经提出了多种机制来解释甲状旁腺素是如何发挥其有益作用的，但这些作用是否包括或由刺激骨髓间充质祖细胞活性介导，尚不清楚。我们的新数据支持这一机制，通过证明在小梁骨中存在功能不同的对甲状旁腺激素非常敏感的间充质祖细胞。甲状旁腺激素强烈刺激成骨细胞和成骨细胞的表皮生长因子受体(EGFR)配体--双调蛋白的表达。EGFR在间充质祖细胞中高表达，它的激活刺激这些细胞的增殖、存活和迁移。我们的初步数据显示，阻断小鼠的EGFR活性会导致骨形成缺陷和骨量减少，并伴随着间充质祖细胞数量的减少。有趣的是，PTH处理的成骨细胞的条件培养液以一种双调节蛋白-EGFR依赖的方式吸引间充质祖细胞。此外，成骨细胞系细胞中EGFR活性不足的小鼠对甲状旁腺素注射的合成代谢反应较差。这些数据和其他数据导致了我们的中心假设，即EGFR信号是骨髓间充质祖细胞的重要调节因子，并至少部分介导了间歇性甲状旁腺素给药的合成代谢效应。我们将测试我们的 研究目的：1)通过评估带有Nestin启动子驱动的可诱导CRE的条件性EGFR基因敲除小鼠的骨骼表型，探讨骨髓间充质干细胞中的EGFR失活是否抑制了骨形成和PTH的合成代谢反应；2)阐明在正常和PTH诱导的成骨条件下，EGFR是否在维持骨髓间充质祖细胞数量方面发挥了关键作用。我们将使用不同世系承诺阶段间充质祖细胞EGFR活性低下的动物模型来研究EGFR活性与居住在长骨不同区域的间充质祖细胞群体之间的关系。我们还将使用细胞培养方法来确定一组转录因子EGRs是否介导和调节EGFR刺激的间充质祖细胞的增殖和存活；3)确定PTH注射激活的EGFR信号是否通过体内移植方法向骨表面招募间充质祖细胞，在体内可以看到GFP标记的间充质祖细胞。这三个目标的完成将使我们能够第一次确定EGFR在骨形成中的作用以及骨对骨质疏松治疗PTH的合成代谢反应。从长远来看，我们试图确定是否可以将EGFR信号作为治疗骨质疏松症和其他骨相关疾病的一种新的合成代谢策略。