EGFR signaling in growth plate development

描述(由申请人提供)：生长板的发育对纵向骨生长至关重要。这一过程包括软骨细胞的增殖、成熟和肥大、矿化、基质重塑和从软骨向骨的过渡，受到循环中的全身激素和局部产生的生长因子的严格控制。然而，其调控机制尚未完全阐明。以前的研究注意到改变表皮生长因子受体(EGFR)的活性会导致生长板结构异常，但具体的分子机制还没有研究。我们最近发现，用EGFR特异性抑制剂治疗的幼年大鼠生长板软骨出现了严重的缺陷，其特征是生长板增厚和大量肥大的软骨细胞聚集。进一步的研究表明，EGFR抑制剂抑制了基质金属蛋白酶(MMP9和13)的表达，增加了胶原纤维的数量，并减少了生长板中软骨细胞外基质的降解。在原代培养的软骨细胞中，EGFR配体转化生长因子β强烈刺激MMP9和MMP13的表达。因此，我们假设EGFR信号通过促进生长板中基质金属蛋白酶的表达来调节细胞外基质的降解和肥大软骨的骨替代。我们提出以下目的来验证这一假说：1)确定软骨源性EGFR信号在软骨降解和生长板发育中是否需要~2)研究EGFR信号刺激软骨源性MMP9和13表达的分子机制。特别是，我们将利用药理学大鼠模型、软骨细胞特异性EGFR基因敲除小鼠模型和原代软骨细胞培养来检测生长板的表型并分析其潜在机制。我们的长期目标是研究EGFR信号在软骨功能中的作用。该项目的研究结果将表明，EGFR信号通路是一种调节软骨内成骨的新途径，并可能成为治疗骨骼疾病的潜在药物靶点，这些疾病包括儿童生长板疾病和骨关节炎。此外，作为一名新的调查员，我将从 该奖项通过生成用于竞争未来研究支持的初步数据来实现。 与公共健康相关：生长板的发育对骨骼的形成和生长是必不可少的，这一过程受到生长因子的严格控制。这项建议将研究一种新的生长因子信号在调节生长板发育中的作用，并成功实现它将实现对与生长缺陷相关的疾病的更好管理，如软骨发育不良、生长迟缓和最终身高降低、骨折愈合和退行性软骨疾病，如骨关节炎。

DESCRIPTION (provided by applicant): Growth plate development is critical for longitudinal bone growth. This process, including chondrocyte proliferation, maturation and hypertrophy, mineralization, matrix remodeling and transition from cartilage to bone, is tightly controlled by circulating systemic hormones and locally produced growth factors. However, the regulatory mechanisms have not been fully elucidated. Previous studies noticed that altering epidermal growth factor receptor (EGFR) activity resulted in abnormal growth plate structures but the detailed molecular mechanisms have not been studied yet. We recently found that young growing rats treated with EGFR-specific inhibitors developed profound defects in growth plate cartilage characterized by epiphyseal growth plate thickening and massive accumulation of hypertrophic chondrocytes. Further studies demonstrate that EGFR inhibitors suppressed the expression of matrix metalloproteinases (MMP9 and 13), increased the amount of collagen fibrils, and decreased cartilage ECM degradation in the growth plate. Consistently, TGF¿, an EGFR ligand, strongly stimulated the expression of MMP9 and 13 in primary chondrocytes. Hence, we hypothesize that EGFR signaling regulates ECM degradation and replacement of hypertrophic cartilage with bone by promoting MMP expression in the growth plate. We propose the following aims to test this hypothesis: 1) determine whether chondrogenic EGFR signaling is required for cartilage degradation and growth plate development~ 2) investigate the molecular mechanisms by which EGFR signaling stimulates chondrogenic expression of MMP9 and 13. In particular, we will utilize a pharmacological rat model, a chondrocyte-specific EGFR knockout mouse model, and primary chondrocyte cultures to examine the growth plate phenotypes and analyze the underlying mechanisms. Our long-term goal is to study the role of EGFR signaling in cartilage function. Findings from this project will suggest EGFR signaling as a novel pathway regulating endochondral ossification and a potential pharmaceutical target for skeletal disorders that have abnormal cartilage degradation, including childhood growth plate disorders and osteoarthritis. In addition, as a new investigator, I will be greatly benefited from this award by generating preliminary data to be used for competing future research supports. PUBLIC HEALTH RELEVANCE: Growth plate development is essential in formation and growth of the skeleton and this process is tightly controlled by growth factors. This proposal wil investigate the role of a novel growth factor signaling in regulating growth plate development and successfully accomplishing it will achieve a better management of diseases associated with growth defects, such as chondrodysplasia, retarded growth and reduced final height, fracture healing, and degenerative cartilage diseases, such as osteoarthritis.