Molecular and cellular determinants of enthesopathy in X-linked hypophosphatemia

X连锁低磷血症中附着点病变的分子和细胞决定因素

• 批准号: 8867825
• 负责人: Eva S. Liu
• 金额: $ 13.1万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8867825
• 关键词: Ablation; Abnormal Cell; Address; Advisory Committees; Affect; Age; Antibodies; Award; Basic Science; Biology; Birth; Blocking Antibodies; Bone Diseases; Calcitonin; Cell Lineage; Cells; Characteristics; Chondrocytes; Chondrogenesis; Clinical; Clinical Endocrinology; Communities; Complex; Complication; Comprehension; Data; Development; Development Plans; Dihydroxycholecalciferols; Disease; Embryo; Endopeptidases; Enthesopathies; Erinaceidae; Exhibits; Experimental Designs; Fibroblast Growth Factor; Fibrocartilages; Functional disorder; Goals; Grant; Growth; Hindlimb Suspension; Homeostasis; Hypophosphatemia; In Situ Hybridization; Inherited; Institution; Investigation; Ions; Journals; Kidney; Knock-out; Knockout Mice; Knowledge; Laboratories; Lead; Link; Manuscripts; Mechanical Stress; Mechanics; Medicine; Mentors; Mentorship; Minerals; Modality; Modeling; Molecular; Morbidity - disease rate; Mus; Muscle strain; Musculoskeletal; Musculoskeletal Diseases; Mutation; National Research Service Awards; New England; Pain; Pathologic; Pathway interactions; Patients; Phenotype; Physicians; Play; Production; Publications; Relative (related person); Reporting; Research; Research Personnel; Rickets; Role; Scientist; Serum; Signal Pathway; Signal Transduction; Site; Sodium; Supplementation; Tendon structure; Therapeutic Agents; Training; Transgenic Organisms; Vitamin D3 Receptor; Work; Writing; abstracting; achilles tendon; base; bone; bone morphogenic protein; career; career development; dentin matrix protein 1; design; experience; human SMO protein; improved; inorganic phosphate; insight; interest; meetings; mineralization; motor impairment; mouse model; novel therapeutics; progenitor; programs; public health relevance; research study; scleraxis; skeletal; skills; smoothened signaling pathway; sodium phosphate; symporter; symposium; tendon development; transcription factor

 DESCRIPTION (provided by applicant): Project Summary/Abstract X-linked hypophosphatemia (XLH) is the most common form of inheritable rickets, characterized by elevated FGF23 levels leading to low serum phosphate and impaired production of 1,25 dihydroxyvitamin D (1,25(OH)2D). Mutations in the endopeptidase PHEX are responsible for the XLH phenotype. While it is known that increases in FGF23 result from PHEX mutations, the molecular basis for this remains unknown. Pathologic mineralization of the enthesis (tendon-bone attachment site), referred to as enthesopathy, is a complication of XLH. Common sites of involvement include the Achilles and patellar entheses. Although it causes significant morbidity in patients, the molecular mechanisms responsible for the enthesopathy and impact of currently available modalities of treatment on the development of enthesopathy are poorly understood. Murine models of hypophosphatemia, including the vitamin D receptor knockout (VDR KO) and the renal type II sodium dependent phosphate co-transporter (Npt2a) KO do not have enthesopathy. In contrast, mice with hypophosphatemia and elevated serum FGF23 levels, including the Hyp mouse (murine model of XLH) and the dentin matrix protein 1 (DMP1) KO, do develop enthesopathy, suggesting FGF23 and not serum phosphate could have a pathogenic role in enthesopathy development. However, VDR KO mice do not develop rickets until 3 weeks of age, while the rickets in Npt2aKO mice reverses by 4 weeks due to increased 1,25(OH)2D levels. Since both the Hyp and DMP1 KO mice have progressive rickets from birth, the impaired skeletal mineralization may alter mechanical forces in the maturing enthesis, contributing to the development of enthesopathy in XLH and DMP1 inactivation. The studies proposed are focused on elucidating the molecular and cellular basis for this enthesopathy in a murine model of XLH (Hyp mice). Investigations proposed in Aim I will provide a molecular characterization of the abnormal cells in the entheses of Hyp mice and identify signaling pathways implicated in the development of enthesopathy. The lineage tracing studies in Aim II will identify the origin of these cells in the Hyp enthesis and the pathophysiologic basis for their aberrant differentiation. The studies proposed in Aim III will identify the relative contributions of FGF23, impaired mineralization and mechanical strain on enthesopathy development and progression. The molecular pathophysiology underlying this aberrant mineralization will also provide insight into enthesis abnormalities associated with other musculoskeletal disorders. Prior studies have focused on embryonic tendon development, thus these experiments will contribute to our understanding of normal post-natal enthesis maturation. The PI, Dr. Liu, is a physician-scientist whose long-term goal is to lead an independent basic science laboratory with a focus on musculoskeletal biology. She developed a strong interest in rare bone diseases while examining the effect of calcitonin on serum FGF23 levels in patients with XLH. She designed, executed and performed analyses for this study, which led to a first author publication in the New England Journal of Medicine. This study combined with her rigorous training in clinical endocrinology allowed Dr. Liu to recognize how clinical experiences can inform her research hypotheses. Her passion for studying the molecular pathophysiology underlying XLH led her to join the laboratory of Dr. Marie Demay, a senior investigator in skeletal biology. Dr. Liu was awarded a F32/NRSA grant to investigate how different treatment modalities, including daily 1,25(OH)2D and FGF23 blocking antibody, affect growth, mineral ion homeostasis, chondrocyte differentiation, and skeletal mineralization. A K08 award will allow Dr. Liu to take advantage of the rich mentorship available in the Harvard skeletal biology community. Her co-mentor Dr. Vicki Rosen, advisory committee, and collaborators, all renowned investigators in musculoskeletal biology, will provide her with valuable advice on experimental design and analyses, as well as career guidance. The career plan, consisting of regular meetings with mentors, course work, didactic conferences, research seminars and journal clubs is designed to enhance her research experience. Dr. Liu will develop expertise in the design, execution and interpretation of studies aimed at dissecting complex skeletal phenotypes at the molecular and cellular levels. She will refine her grant and manuscript writing skills and immerse herself in the field of skeletal and tendon biology. The carefully designed career development plan, combined with a rigorous laboratory experience will provide her with the skills necessary for her to establish her independent research program in an academic institution.

 描述（由申请人提供）：项目摘要/摘要 X 连锁低磷血症 (XLH) 是遗传性佝偻病的最常见形式，其特征是 FGF23 水平升高，导致血清磷酸盐水平降低以及 1,25 二羟基维生素 D 的产生受损（1,25 (OH)2D) 内肽酶 PHEX 的突变是导致 XLH 表型增加的原因。 FGF23 是 PHEX 突变的结果，其分子基础仍不清楚，称为附着点病变，是 XLH 的并发症，常见的受累部位包括跟腱和髌骨附着点。导致患者显着发病，但目前对附着点病的分子机制以及目前可用的治疗方式对鼠科动物模型的影响知之甚少。低磷血症，包括维生素 D 受体敲除 (VDR KO) 和肾 II 型钠依赖性磷酸盐协同转运蛋白 (Npt2a) KO 小鼠，不会出现附着病；相比之下，患有低磷血症和血清 FGF23 水平升高的小鼠，包括 Hyp 小鼠（鼠）。 XLH 模型）和牙本质基质蛋白 1 (DMP1) KO 确实会发生附着点病变，这表明 FGF23 而不是血清磷酸盐可能具有然而，VDR KO 小鼠直到 3 周龄才会出现佝偻病，而 Npt2aKO 小鼠中的佝偻病由于 Hyp 和 DMP1 KO 后 1,25(OH)2D 水平增加而在 4 周后逆转。小鼠从出生起就患有进行性佝偻病，骨骼矿化受损可能会改变成熟附着点的机械力，导致 XLH 和 XLH 中附着点病的发生DMP1 失活的研究重点是阐明 XLH（Hyp 小鼠）小鼠模型中这种附着点病变的分子和细胞基础。Aim I 中提出的研究将提供 Hyp 小鼠附着点异常细胞的分子特征。确定与附着点病变发展有关的信号通路 Aim II 中的谱系追踪研究将确定这些细胞在附着点中的起源及其病理生理学基础。 Aim III 中提出的研究将确定 FGF23、矿化受损和机械应变对附着点病变发展和进展的相对影响，这种异常矿化的分子病理生理学也将提供与其他肌肉骨骼疾病相关的附着点异常的见解。我们专注于胚胎肌腱的发育，因此这些实验将有助于我们了解正常的产后附着点成熟。首席研究员刘博士是一位医师兼科学家。她的长期目标是领导一个专注于肌肉骨骼生物学的独立基础科学实验室，她在研究降钙素对 XLH 患者血清 FGF23 水平的影响时产生了浓厚的兴趣。这项研究的第一作者发表在《新英格兰医学杂志》上。这项研究结合她在临床内分泌学方面的严格培训，使刘博士认识到临床经验如何影响她的研究假设。分子XLH 的病理生理学促使她加入了骨骼生物学高级研究员 Marie Demay 博士的实验室，并获得了 F32/NRSA 资助，以研究不同的治疗方式（包括每日 1,25(OH)2D 和 FGF23）的效果。 K08 奖将使刘博士能够利用丰富的指导。她在哈佛骨骼生物学界的合作导师 Vicki Rosen 博士、顾问委员会以及肌肉骨骼生物学领域的所有著名研究人员将为她提供有关实验设计和分析以及职业规划的宝贵合作者建议，包括与导师的定期会议、课程作业、教学会议、研究研讨会和期刊俱乐部，旨在增强她的研究经验。刘博士将发展旨在解剖复杂骨骼的研究的设计、执行和解释方面的专业知识。她将完善她的资助和手稿写作技巧，并沉浸在骨骼和肌腱生物学领域。精心设计的职业发展计划，加上严格的实验室经验，将为她提供所需的技能。她在学术机构建立了自己的独立研究项目。