Pathogenic Mechanisms in Hereditary Multiple Exostoses Syndrome

遗传性多发性外生骨疣综合征的发病机制

• 批准号: 8475565
• 负责人: EIKI KOYAMA
• 金额: $ 48.26万
• 依托单位: CHILDREN'S HOSP OF PHILADELPHIA
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8475565
• 关键词: Adolescent; Adverse effects; Affect; Binding; Biochemical; Biomedical Research; Blood Vessels; Cartilage; Cartilaginous exostosis; Cells; Child; Chondrocytes; Chondrogenesis; Communities; Defect; Deformity; Degenerative polyarthritis; Developmental Process; Disease; EXT1 gene; EXT2 gene; Elements; Epiphysial cartilage; Erinaceidae; Exostoses; Family; Family member; Fatigue; Genes; Genetic; Growth; Heparitin Sulfate; Hereditary Multiple Exostoses; Impairment; Incidence; Infiltration; Life; Malignant - descriptor; Malignant Bone Neoplasm; Mesenchymal; Mesenchymal Differentiation; Methods; Molecular; Motion; Mus; Mutation; Nerve compression syndrome; Operative Surgical Procedures; Organ; Pain; Palliative Care; Pathogenesis; Patients; Physiological Processes; Procedures; Production; Protein Binding; Proteins; Proteoglycan; Reporter; Role; Severities; Signal Pathway; Signal Transduction; Signaling Protein; Stem cells; Structure; Syndrome; Tendon structure; Testing; Therapeutic; Tissues; base; bone; drug candidate; early onset; effective therapy; glycosyltransferase; in vitro Model; in vivo; insight; interest; liquid chromatography mass spectrometry; loss of function mutation; mutant; neglect; prevent; research study; skeletal; skeletal dysplasia; sulfation; translational medicine; tumor

DESCRIPTION (provided by applicant): Hereditary Multiple Exostoses (HME) is an autosomal dominant disorder that affects about 1 in 20,000 children. HME is characterized by cartilage-capped outgrowths that form adjacent to the growth plates, protrude into surrounding tissues and organs, and cause growth retardation, compression of nerves and early onset osteoarthritis. They become malignant in about 5% of the patients. Current therapies are palliative, and patients struggle with pain and limited mobility and undergo multiple surgeries through life. The genes responsible for HME cases are EXT1 and EXT2 that encode glycosyltransferases responsible for heparan sulfate (HS) synthesis. Patients are heterozygous for EXT1 or EXT2 loss-of-function mutations and their cells produce lower HS amounts. HS-rich proteoglycans regulate key physiologic processes by various mechanisms and most notably by restricting the topographical distribution and action of hedgehog, BMPs and other signaling factors within tissues, but it is not known whether defects in these mechanisms subtend HME. In ongoing studies, we found that HS deficiency in growth plate leads to re-distribution of Indian hedgehog (Ihh), its infiltration over the entire perichondrium and formation of exostosis-like cartilaginous masses within perichondrium itself. A similar ectopic action of Ihh was seen in mouse growth plates deficient in HS N- sulfation. We found also that interference with HS function greatly stimulates differentiation of mesenchymal cells into chondrocytes. Thus, our central hypothesis is that the HS deficiency in HME (i) causes re-distribution of hedgehog and other pro-chondrogenic factors from growth plate to perichondrium and (ii) enhances responsiveness of perichondrial cells to these and other local factors. As a result of this combination of mechanisms, growth plate and perichondrium would mis-communicate, and perichondrial cells would lose their normal character, become chondrogenic and give rise to exostoses. To test our hypotheses, we will analyze the mechanisms of exostosis formation by creating conditional Ext-deficient mice in growth plate and/or perichondrium and determining roles of pro-chondrogenic signaling pathways (Aim 1). We will determine the mechanisms for increased chondrogenic capacity of HS-deficient cells will test their responsiveness to signaling factors and assess structure and protein binding capabilities of their HS chains (Aim 2). We will then carry out proof-of-principle experiments to determine whether pharmacologic antagonists of pro-chondrogenic signaling pathways block exostosis formation (Aim 3). The project will provide fundamentally new insights into the cellular and molecular mechanisms of HME pathogenesis and will test possible rational therapies based on those insights. The project thus has significant importance for both basic biomedical research and translational medicine in HME and related growth plate-based skeletal dysplasias. The number of HME patients is small, but the community of their families is large. This project will thus provide a renewed sense of hope to patients and families alike that this neglected disease will actively be studied and a cure may one day be found.

描述（由申请人提供）：遗传多个外遗体（HME）是一种常染色体显性疾病，影响了20,000名儿童中约1个。 HME的特征是软骨封闭的生长，与生长板相邻，突出到周围的组织和器官中，并引起生长迟缓，神经的压缩和早期发作骨关节炎。他们在约5％的患者中变得恶性。当前的疗法是姑息治疗的，患者因疼痛和流动性有限而挣扎，并在生活中进行多次手术。负责HME病例的基因是Ext1和Ext2，编码负责硫酸乙酰肝素（HS）合成的糖基转移酶。患者对于Ext1或Ext2功能丧失突变而杂合子且细胞产生较低的HS量。富含HS的蛋白聚糖通过各种机制来调节关键生理过程，最著名的是限制组织中刺猬，BMP和其他信号传导因素的地形分布和作用，但尚不知道这些机制中的缺陷是否属于HME。在正在进行的研究中，我们发现生长板的HS缺乏会导致印度刺猬（IHH）的重新分布，其对整个perichondrium的渗透以及在perichondrium本身内形成类似库氏菌的软骨块的形成。在缺乏HS N-硫酸化的小鼠生长板中也看到了IHH的类似异位作用。我们还发现，对HS功能的干扰极大地刺激了间充质细胞分化为软骨细胞。因此，我们的中心假设是HME（i）的HS缺乏会导致刺猬和其他促可能因素从生长板到perichondrium的重新分布，并且（ii）增强了围绕这些细胞对这些和其他局部因素的反应性。由于这种机制，生长板和per骨的结合会误导，而围绕骨的细胞会失去其正常特征，变得软骨，并引起外遗体。为了检验我们的假设，我们将通过在生长板和/或perichondrium中创建有条件的伸长小鼠来分析外癌形成的机制，并确定促核能信号传导途径的作用（AIM 1）。我们将确定HS缺陷细胞增加软骨的能力的机制将测试其对信号因子的响应能力，并评估其HS链的结构和蛋白质结合能力（AIM 2）。然后，我们将进行原则证明实验，以确定促可能性信号通路的药理学拮抗剂是否会阻止形成外静病的形成（AIM 3）。该项目将从根本上为HME发病机理的细胞和分子机制提供新的见解，并将基于这些见解测试可能的有理疗法。因此，该项目对于HME和相关生长板的骨骼发育不良的基本生物医学研究和转化医学都具有重要意义。 HME患者的数量很少，但是他们家庭的社区很大。因此，该项目将为患者和家庭提供一种新的希望感，即将积极研究这种被忽视的疾病，并可能有一天可以治愈。