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: 8699764
• 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/8699764
• 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.

描述（申请人提供）：间歇性甲状旁腺激素（PTH）注射由于其对骨形成的显着作用，是治疗骨质疏松症最有效的合成代谢疗法之一。成骨细胞源自间充质祖细胞，包括间充质干细胞（MSC）和定向骨祖细胞。已提出多种机制来解释 PTH 如何发挥其有益作用，但这些作用是否包括或由骨髓间充质祖细胞活性刺激介导尚不清楚。我们的新数据通过证明小梁骨内存在功能独特的间充质祖细胞群来支持这一机制，这些细胞对 PTH 非常敏感。 PTH 强烈刺激成骨细胞和骨细胞中双调蛋白（一种表皮生长因子受体 (EGFR) 配体）的表达。 EGFR 在间充质祖细胞中高度表达，其激活可刺激这些细胞的增殖、存活和迁移。我们的初步数据表明，阻断小鼠的 EGFR 活性会导致骨形成缺陷和骨质减少表型，并伴有间充质祖细胞数量的减少。有趣的是，来自 PTH 处理的成骨细胞的条件培养基以双调蛋白-EGFR 依赖性方式趋化间充质祖细胞。此外，成骨细胞谱系细胞中EGFR活性缺陷的小鼠对PTH注射的合成代谢反应较差。这些和其他数据引出了我们的中心假设，即 EGFR 信号传导是骨髓间充质祖细胞的重要调节因子，并且至少部分介导间歇性 PTH 给药的合成代谢作用。我们将测试我们的 通过追求以下目标来提出中心假设：1）通过评估条件性 EGFR 敲除小鼠的骨骼表型，使用巢蛋白启动子驱动的诱导型 Cre（无论有或没有 PTH 治疗），研究 MSC 中 EGFR 失活是否会抑制骨形成和对 PTH 的合成代谢反应； 2）阐明EGFR是否在正常和PTH诱导的骨形成条件下维持骨髓间充质祖细胞群中发挥关键作用。我们将使用处于不同谱系定型阶段的间充质祖细胞中EGFR活性缺陷的动物模型来研究EGFR活性与位于长骨不同区域的间充质祖细胞群之间的关系。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) 通过使用体内移植方法确定由 PTH 注射激活的 EGFR 信号传导是否将间充质祖细胞招募到骨表面，其中 GFP 标记的间充质祖细胞可以被可视化。这三个目标的完成将使我们能够首次确定 EGFR 在骨形成中的作用以及骨对骨质疏松症治疗 PTH 的合成代谢反应。从长远来看，我们寻求确定是否可以将 EGFR 信号作为治疗骨质疏松症和其他骨相关疾病的新型合成代谢策略。