PATHOGENESIS OF BONE EROSION IN RHEUMATOID ARTHRITIS

类风湿性关节炎(RA)是一种慢性炎症性疾病，通常会造成严重的 关节软骨和骨。大量证据表明，类风湿性关节炎的骨质侵蚀是由 破骨细胞(OC)。破骨细胞分化和激活的关键因素是受体激活剂 核因子-kB配体(RANKL)通过一种特定的细胞表面受体、受体-激活剂 核因子-KB(等级)。最近发现了一种新的分泌型RANKL(SecRANKL)，它似乎可以 由一个独特的推动者进行监管。这项提案中概述的研究旨在检验这一假设 RANKL在RA骨侵蚀部位局部表达增强及其调控 RANKL在骨侵蚀部位细胞中的表达是局灶性骨丢失的关键决定因素。 特定目标1将检验这样一个假设，即来自RA滑膜的细胞产生RANKL是 在破骨细胞性骨侵蚀的发病机制中起关键作用。这一目标将解决以下问题： RA骨侵蚀部位RANKL的确切细胞来源是什么？RANKL在哪里表示 与OPG表达的关系以及与阳性OC前体的关系？取回的人体组织将被利用 初步回答这些问题。细胞表达谱将得到确认，时间表达 其中的这些因素将在两种炎性关节炎小鼠模型中确定，胶原性关节炎 (CIA)和KJBxN模型。分散的RA滑膜细胞将被用来确定 RANKL在相关细胞类型中的异构体。最后，secRANKL亚型在破骨细胞形成中的活性 将在破骨细胞生成的体外共培养模型中确定。《特定目标2》将测试 假设T细胞来源的RANKL是RA骨侵蚀所必需的。关节炎会在 T细胞提供RANKL唯一来源的小鼠，以及缺乏RANKL的基因工程小鼠品系 T细胞，以确定T细胞来源的RANKL在骨侵蚀中的作用。具体目标3 将确定负责构成和诱导表达的调控元件 膜结合的RANKL亚型存在于类风湿关节炎的细胞类型中，并将检验这一假设 NFAT转录因子家族在emRANKL基因的诱导调控中起着关键作用。 RT-PCR分析RANKL在RA局灶性骨侵蚀中的表达细胞类型 已知的两种RANKL亚型的差异构成和诱导表达。初步数据还 证明NFATs在T细胞RANKL调节中的潜在作用。这一目标将提供有关 RANKL GONE在RA骨侵蚀细胞类型中的表达调节可能导致新的 预防该病骨质破坏的治疗策略。

Rheumatoid arthritis (RA) is a chronic inflammatory disease that often produces severe destruction of articular cartilage and bone. Considerable evidence indicates that bone erosions in RA are produced by osteoclasts (OC). An essential factor for the differentiation and activation of osteoclasts is receptor-activator of NF-KB ligand (RANKL) which mediates its effects via a specific cell surface receptor, receptor-activator of NF-KB (RANK). Recently a novel secreted form of RANKL (secRANKL) has been identified which appears to be regulated by a unique promoter. The studies outlined in this proposal are designed to test the hypothesis that that there is enhanced local expression of RANKL at sites of bone erosion in RA and that regulation of RANKL expression in cells at sites of bone erosion is a critical determinant of focal bone loss. Specific Aim 1 will test the hypothesis that RANKL production by cells derived from RA synovium is critical in the pathogenesis of osteoclastic bone erosion. This aim will address the following questions: What are the exact cellular sources of RANKL at sites of bone erosion in RA? Where is RANKL expressed in relation to OPG expression and to RANK positive OC precursors? Retrieved human tissues will be utilized initially to answer these questions. Cellular expression profiles will be confirmed and the temporal expression of these factors will be determined in two murine models of inflammatory arthritis, collagen induced arthritis (CIA) and the KJBxN model. Dispersed cells from RA synovium will be used to determine the expression of RANKL isoforms in relevant cell types. Finally, the activity of the secRANKL isoform in osteoclastogenesis will be determined in an in vitro co-culture model of osteoclastogenesis. Specific Aim 2 will test the hypothesis that T cell derived RANKL is required for bone erosion in RA. Arthritis will be generated in mice in which T cells provide the only source of RANKL, and in genetically engineered mouse strains lacking T cells, in order to definitively determine the role of T cell-derived RANKL in bone erosion. Specific Aim 3 will identify regulatory elements responsible for the constitutive and inducible expression of the membrane-bound RANKL isoform in cell types present in RA, and will test the hypothesis that the NFAT family of transcription factors is critical in the inducible regulation of the memRANKL gene. RT-PCR analysis of RANKL expressing cell-types present in focal RA bone erosions demonstrates differential constitutive and inducible expression of the two known RANKL isoforms. Preliminary data also demonstrate a potential role of NFATs in RANKL regulation in T cells. This Aim will provide data on the regulation of RANKL gone expression in cell types present in bone erosion in RA and may lead to new therapeutic strate0ies for preventing bone destruction in this disease.