Genetics of Osteoblast Differentiation

描述（由申请人提供）：从间充质干细胞（MSC）适当发育成熟的功能性成骨细胞对数百万患有骨质疏松症的美国人的骨骼健康至关重要。成骨细胞在骨稳态中起关键作用，因为它们负责新骨组织的形成和矿化。骨质疏松症的一种潜在治疗方法是促进成骨细胞活性，以对抗许多患者中发生的骨材料丢失。然而，成骨细胞的发育进程和分化在分子水平上的特征不足以识别潜在的新药物靶点。在这项研究中，我们建议使用RNA-seq技术测量全基因组转录动力学在整个分化过程中从MSC成熟成骨细胞在纯化的细胞培养物来自5个不同品系的实验室小鼠。同时，我们将测量我们的培养物的体外矿化动力学，以及相同品系小鼠体内骨形成的组织形态计量学测量。我们将分析这些RNA-seq数据，以确定成骨细胞发生的关键转录事件，包括所有受检菌株共同的显著表达变化和不同遗传背景的独特变化。通过将这些表达数据与现有的体内表型数据以及本项目将测量的体外和体内表型整合，我们将把转录变化与临床重要表型关联起来。通过这一过程确定的基因和蛋白质将包括潜在的药物靶点，可以在未来的项目中进一步评估和研究。 公共卫生相关性：据预测，目前有4370万50岁以上的美国人已经患有骨质疏松症或处于严重的骨质疏松症风险中。根据最近的外科医生报告，在美国每年有超过150万例骨折，包括28万例髋部骨折和50万例椎骨骨折。每10名女性中有2名和每10名男性中有3名髋部骨折患者将在骨折后1年内死亡，一半人将永远无法恢复以前的生活状况，70-80%的人将永远无法独立行走。在美国，每年用于治疗骨质疏松症的直接卫生保健费用超过183亿美元。越来越多的证据表明，间充质干细胞（MSCs）向功能性成骨细胞的适当分化在骨健康和体内平衡中起着关键作用。对小鼠和人类的研究表明，随着年龄的增长，骨髓中的成骨细胞数量减少，骨髓肥胖程度增加。治疗骨质疏松症的最有希望的治疗途径之一是开发促进成骨细胞功能的合成代谢剂。目前，只有一种促进成骨细胞的药物被FDA批准（特立哌齐），但这种化合物具有显著的风险，因此适用于不超过两年。为了更好地了解骨质疏松症的遗传基础并开发新的治疗方法，我们必须从分子和遗传学的角度了解成骨细胞分化的过程，这是本提案的目标。

DESCRIPTION (provided by applicant): The proper development of mature, functional osteoblasts from mesenchymal stem cells (MSCs) is critical to the bone health of millions of Americans suffering from osteoporosis. Osteoblasts play a key role in bone homeostasis as they are responsible for the formation and mineralization of new bone tissue. A potential treatment for osteoporosis is to promote osteoblast activity in order to combat the loss of bone material that occurs in many patients. However, the developmental progression and differentiation of osteoblasts is inadequately characterized at a molecular level to identify potential new drug targets. In this study, we propose to measure whole genome transcriptional dynamics using RNA-seq technology throughout the differentiation process from MSC to mature osteoblast in purified cell cultures derived from 5 diverse strains of laboratory mouse. In parallel, we will measure in vitro mineralization dynamics of our cultures, as well as in vivo histomorphometric measures of bone formation in mice of the same strains. We will analyze these RNA-seq data to indentify the key transcriptional events of osteoblastogenesis, including significant expression changes common to all examined strains and unique to different genetic backgrounds. By integrating these expression data with existing in vivo phenotypic data as well as the in vitro and in vivo phenotypes that will be measured in this project, we will correlate transcriptional changes with clinically important phenotypes. The genes and proteins identified through this process will include potential drug targets that can be further evaluated and studied in future projects. PUBLIC HEALTH RELEVANCE: It is predicted that currently 43.7 million Americans over the age of 50 already have or are at serious risk of developing osteoporosis. Based on a recent surgeon general's report, in the United States there are over 1.5 million osteoporotic fractures each year, including 280,000 hip fractures and 500,000 vertebral fractures. Two out of every 10 women and 3 out of every 10 men who suffer a fracture of the hip will die within 1 year of that fracture, half will never return to their previous living situation, and 70-80% will never walk again unaided. The annual direct health care costs for treatment of osteoporosis in the United States is over $18.3 billion. Increasing evidence shows that proper differentiation of mesenchymal stem cells (MSCs) into functional osteoblasts plays a key role in bone health and homeostasis. Studies in both mouse and human have shown that with age, the number of osteoblasts in marrow decreases and the degree of marrow adiposity increases. One of the most promising therapeutic avenues for the treatment of osteoporosis is the development of anabolic agents which promote osteoblast function. Currently, only a single osteoblast promoting drug is approved by the FDA (teriparatide), but this compound carries significant risks and is thus indicated for use for no more than two years. In order to better understand the genetic bases of osteoporosis and to develop new treatments, we must understand the process of osteoblast differentiation from both a molecular and genetic perspective, which is the goal of this proposal.