Mechanisms of bone fragility in Autosomal Dominant Osteopetrosis type II: from human to mouse and back

常染色体显性骨硬化症 II 型骨脆性机制：从人到小鼠再到背部

• 批准号: 10366576
• 负责人: Thomas Levin Geiser Andersen
• 金额: $ 49.48万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2027-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10366576
• 关键词: Affect; Age; Albers-Schonberg disease; Antibody Therapy; Automobile Driving; Back; Biomechanics; Biopsy Specimen; Bone Diseases; Bone Marrow Transplantation; Bone Resorption; Bone remodeling; Bone structure; CD14 gene; Caring; Cell Nucleus; Cells; Characteristics; Coculture Techniques; Communication; Complement; Computer Assisted; Coupling; Data; Development; Disease; Elderly; Endosteal Cell; Family; Future; Genes; Genetic Transcription; Goals; Human; Image; In Situ Hybridization; In Vitro; Inherited; Investigation; Knowledge; Mature Bone; Mediating; Molecular; Mus; Mutation; Osteoblasts; Osteoclasts; Osteogenesis; Osteoporosis; Pathologic; Patients; Peripheral; Phenotype; Physiological; Physiology; Process; Resources; Sampling; Scallop; Skeletal bone; TNFSF11 gene; Testing; Withdrawal; Work; base; bone; bone fragility; bone loss; bone mass; cell type; cost; human model; in vivo; innovation; insight; lens; monocyte; mouse model; multimodality; novel; novel therapeutics; overexpression; progenitor; programs; sex; skeletal; therapeutic target; tool; transcriptome sequencing; transcriptomics; translational impact; treatment strategy

SUMMARY Coupling, or communication between the bone-resorbing osteoclasts and bone-forming osteoblasts during bone remodeling, is a key step in the bone remodeling cycle. While compelling evidence shows that bone loss and fragility with age and osteoporosis result from corrupted coupling, the precise mechanism of osteoclast- osteoblast communication remains unclear. Thus, although stimulating coupling is a theoretically attractive therapeutic target, current treatments for osteoporosis, a common disorder affecting 54 million of the elderly in the US alone, are limited to either inhibiting osteoclastic bone resorption or stimulating osteoblastic bone formation. Our long-term goal is to determine the mechanism of osteoclast-osteoblast communication critical for coupling of bone formation to resorption during physiological bone remodeling, using rare osteopetrotic diseases as a tool. Rare bone diseases provide important insights into typical bone physiology and knowledge gained from these diseases has already led to new therapies for osteoporosis. In this proposal, we utilize samples from patients with autosomal dominant osteopetrosis type II (ADOII), a rare inheritable osteopetrosis characterized by high bone mass and skeletal fragility and complement human studies with mouse models. ADOII results from heterozygous mutations in the CLCN7 gene, which encodes the ClC-7 Cl-/H+ exchanger essential for osteoclastic bone-resorption. While the lack of osteoclastic resorption clearly contributes to bone phenotype, bone formation is also inappropriately high. In preliminary data investigating the bone structural unit (BSU) composition of ADOII bones, we found bone formation is primarily remodeling based, with excess bone formation called overflow remodeling. Osteoclasts are abundant and scalloped cement lines suggest an intermittent pit-like resorption mode, which in combination with overflow remodeling results in a characteristic puzzle-like bone structure. We hypothesize that the anabolically active but poorly resorptive osteoclasts in ADOII overexpress anabolic coupling factors, inappropriately stimulating bone formation to overfill the resorbed cavities and leading to disorganized puzzle-like bone and fragility. We will test this hypothesis by combining in vivo and in vitro studies of ADOII patients and mouse models, multimodal and multiscale imaging, biomechanics and spatial/single-nuclei transcriptomics. Specifically, we will: 1) test if the high bone mass and fragility in human and mouse ADOII is osteoclast-mediated; and 2) investigate the mechanism of inappropriately high bone formation in ADOII by single nuclei transcriptomic analysis of physically adjacent osteoclasts and osteoblasts. The proposed studies take advantage of the unique resource of extant iliac crest bone biopsy specimens from 15 ADOII patients from a Danish family carrying the CLCN7 (G215R) mutation and age and sex matched controls, and two mouse models of ADOII, including the analogous Clcn7G213R/+ mutation. Through the lens of ADOII, these studies will provide unique insights into osteoclast-osteoblast communication.

总结 骨吸收破骨细胞和骨形成成骨细胞之间的偶联或通讯 在骨重建过程中，是骨重建周期中的关键步骤。尽管有令人信服的证据表明 随着年龄的增长和骨质疏松症的损失和脆弱性是由于破坏耦合，破骨细胞的精确机制， 成骨细胞通讯仍不清楚。因此，虽然刺激耦合在理论上是一个有吸引力的 治疗目标，目前治疗骨质疏松症，一种常见的疾病，影响5400万老年人， 仅限于抑制成骨细胞骨吸收或刺激成骨细胞骨 阵我们的长期目标是确定破骨细胞-成骨细胞通讯的机制， 利用罕见的骨硬化疾病，在生理性骨重建期间将骨形成与再吸收偶联 作为一种工具罕见骨疾病提供了重要的见解，典型的骨生理学和知识获得 已经导致了骨质疏松症的新疗法。 在这个提议中，我们利用来自常染色体显性遗传性石骨症II型（ADOII）患者的样本， 一种罕见的遗传性骨硬化症，以高骨量和骨骼脆弱为特征， 用小鼠模型进行研究。ADOII由CLCN 7基因中的杂合突变引起，该基因编码ADOII。 ClC-7 Cl-/H+交换剂，骨吸收所必需。虽然缺乏骨吸收 尽管骨形成明显有助于骨表型，但骨形成也不适当地高。初步数据显示， 研究ADOII骨的骨结构单位（BSU）组成，我们发现骨形成主要是 重建为基础的，与过量的骨形成称为溢出重建。破骨细胞丰富， 扇形骨水泥线提示间歇性坑状吸收模式， 重塑导致特征性的拼图状骨结构。我们假设合成代谢活跃但 ADOII中吸收不良的破骨细胞过度表达合成代谢偶联因子，不适当地刺激骨 形成过度填充再吸收的空腔，并导致混乱的拼图样骨和脆性。 我们将通过结合ADOII患者和小鼠模型的体内和体外研究来验证这一假设， 多模式和多尺度成像、生物力学和空间/单核转录组学。具体而言，我们将： 1)测试人和小鼠ADOII中的高骨量和脆性是否是破骨细胞介导的;以及2） 探讨单个核在ADOII中不适当的高骨形成的机制 物理上相邻的破骨细胞和成骨细胞的转录组学分析。 拟议的研究利用了现存髂嵴骨活检标本的独特资源 来自15名来自丹麦家族的携带CLCN 7（G215 R）突变的ADOII患者，年龄和性别匹配 对照组和两种ADOII小鼠模型，包括类似的Clcn 7 G213 R/+突变。通过的透镜 这些研究将为破骨细胞-成骨细胞通讯提供独特的见解。