Molecular Mechanisms of Rankl Activation In Osteoblasts

描述（申请人提供）：NF-？受体激活剂B配体（RANKL）是一种TNF？型细胞因子，由间充质谱系细胞（如软骨细胞、成骨细胞和骨细胞）产生，受多种局部炎症介质（包括TNF？、IL-1和IL-6）和全身性调节因子（如1，25（OH）2D 3和PTH）调节，已知在骨形成和骨骼重塑中发挥重要作用。这种细胞因子还调节免疫系统，并且对于额外生物活性的多效性收集也是必需的。RANKL还在各种病因的骨丢失疾病、慢性炎症和自身免疫综合征以及癌症发展和进展中发挥重要的潜在作用。这些不同的生物学作用支持TNFSF 11（RANKL基因）受到精细调控的观点，事实上，我们最近的工作和其他人的工作强调了这一假设。因此，至少10个上游远端Tnfsf 11增强子的复杂集合整合成骨细胞以及T细胞和可能的B细胞中的因子依赖性和细胞特异性调节。Tnfsf 11基因作为一种基本的调控模式的重要性，再加上其在骨骼和其他地方的重要生物学意义，提示了以下具体目标。目标1：确定Tnfsf 11基因座内重要的表观遗传、结构和功能决定因素，这些决定因素对于骨骼内RANKL的转录因子依赖性和细胞类型特异性表达至关重要。目标二：评估小鼠基因组内单个Tnfsf 11增强子缺失对骨细胞RANKL表达和调节以及对体外和体内与年龄、矿物质稳态改变和生理状态（哺乳）相关的生理扰动后出现的骨骼表型的影响。RANKL在生长过程中的骨形成、成人的骨骼重塑和骨折后的骨修复中发挥核心作用。已知由于内分泌功能紊乱、慢性炎性疾病（如关节炎或肿瘤进展）导致RANKL异常表达可导致部位特异性骨丢失和/或骨质疏松症或产生其他异常组织/疾病表型。我们目前的研究旨在确定在体外和体内骨骼和免疫细胞中RANKL因子特异性和细胞类型选择性表达的成分和机制。这些见解可以确定有用的治疗策略，用于控制RANKL表达，从而改善骨质疏松症，自身免疫综合征或其他相关疾病相关的骨丢失。

DESCRIPTION (provided by applicant): Receptor activator of NF-?B ligand (RANKL) is a TNF¿-type cytokine that is produced by mesenchymal lineage cells such as chondrocytes, osteoblasts and osteocytes, regulated by a number of local inflammatory mediators including TNF¿, IL-1 and IL-6 and systemic regulators exemplified by 1,25(OH)2D3 and PTH, and known to play an essential role in bone formation and skeletal remodeling. This cytokine also modulates the immune system and is essential for a pleiotropic collection of additional biologic activities as well. RANKL also plays important underlying roles in bone loss diseases of various etiologies, in chronic inflammatory and autoimmune syndromes and in cancer development and progression. These diverse biological roles support the idea that TNFSF11 (the RANKL gene) is exquisitely regulated, and indeed, our recent work and that of others highlights this hypothesis. Accordingly, a complex set of at least ten upstream distal Tnfsf11 enhancers integrates both factor dependent and cell-specific regulation in osteoblasts as well as T and perhaps B cells. The importance of the Tnfsf11 gene as a basic regulatory paradigm coupled with its significant biological importance in the skeleton and elsewhere prompts the following specific aims. Aim 1: To define important epigenetic, structural and functional determinants within the Tnfsf11 locus which are essential for both transcription factor-dependent and cell type-specific expression of RANKL within the skeleton. Aim 2: To assess the consequence of individual Tnfsf11 enhancer deletions within the mouse genome on bone cell RANKL expression and regulation and on the skeletal phenotypes that emerge following physiological perturbations associated with age, altered mineral homeostasis, and physiologic state (lactation) in vitro and in vivo. RANKL plays a central role in bone formation during growth, in skeletal remodeling in the adult and in bone repair following fracture. Aberrant expression of RANKL as a result of disturbances in endocrine function, chronic inflammatory diseases such as arthritis or tumor progression are known to result in site-specific bone loss and/or osteoporosis or to produce other aberrant tissue/disease phenotypes. Our present studies are designed to determine components and mechanisms responsible for factor-specific and cell typeselective expression of RANKL in the skeleton and in immune cells in vitro and in vivo. These insights may identify useful therapeutic strategies for controlling RANKL expression, thus ameliorating the bone loss associated with osteoporosis, autoimmune syndromes or other related diseases.