Prostaglandin Signaling in Wear Debris-induced Osteolysis

描述(由申请人提供)：这是一项赠款提案的竞争性更新，该提案在最初的资助期确定了RANKL在全关节置换周围骨溶解中的重要性。目前，美国每年有超过40万例关节成形术用于治疗这种疾病。由于多达20%的关节成形术由于无菌性松动而需要翻修手术，这种关节炎治疗的并发症构成了发病率的主要来源，并代表了数十亿美元的医疗费用。在上一次资助期间，我们的工作确定筋膜间滑膜成纤维细胞是RANKL的主要来源。初步数据表明，RANKL的表达依赖于钛颗粒对COX-2和PGE2产生的刺激。此外，我们的研究结果表明，EP4受体参与了滑膜成纤维细胞RANKL的诱导。目的1明确微粒颗粒刺激滑膜成纤维细胞COX-2、启动细胞内信号转导导致RANKL表达的信号机制。我们的假设是，转录因子NFicB启动滑膜成纤维细胞对颗粒的反应，是诱导COX-2所必需的。目的2评估缺乏不同EP受体的小鼠滑膜成纤维细胞对颗粒的体外反应，并检测这些细胞与破骨细胞前体共培养时刺激破骨细胞生成的能力。我们预计，经钛处理的滑膜成纤维细胞将需要EP4受体来诱导RANKL和形成破骨细胞。最后，Aim 3使用缺乏EP受体信号的小鼠颅骨丢失的体内模型来明确定位与RANKL诱导、破骨细胞形成、基因表达和骨溶解有关的信号。滑膜成纤维细胞的作用将通过有条件地删除成纤维细胞中的EP4受体来证实。因此，通过一系列高度整合的体外和体内实验，竞争性更新推进了最初资助期的发现。利用转基因模型和最先进的方法将SF中NFicB激活、COX-2和PGES1表达、PGE2分泌、EP4受体结合和RANKL表达的一系列事件表征为骨溶解的关键事件。

DESCRIPTION (provided by applicant): This is a competitive renewal of a grant proposal that during the initial funding period defined the importance of RANKL in the osteolysis that occurs around total joint replacements. There are currently more than 400,000 arthroplasties performed annually in the U.S. to treat this condition. Since up to 20% of arthroplasties require revision surgery due to aseptic loosening, this complication of arthritic treatment constitutes a major source of the morbidity, and represents billions of dollars in health care costs. During the last funding period, our work defined the interfascial membrane synovial fibroblast as a major source of RANKL. Preliminary data show that RANKL expression is dependent upon the stimulation of COX-2 and PGE2 production by Ti particles. Moreover, our findings suggest that the EP4 receptor is involved in the induction of RANKL in synovial fibroblasts. Aim 1 defines the signaling mechanisms through which particulate debris stimulate COX-2 in synovial fibroblasts and initiates intracellular signals leading to the expression of RANKL. Our hypothesis is that the transcription factor NFicB initiates the synovial fibroblast response to particles and is necessary for COX-2 induction. Aim 2 assesses in vitro responses to particles in synovial fibroblast from mice lacking the various EP receptors and examines the ability of these cells to stimulate osteoclastogenesis in co-cultures with osteoclast precursors. We anticipate that the EP4 receptor will be required for RANKL induction and osteoclast formation by Ti treated synovial fibroblasts. Finally, Aim 3 uses an in vivo model of calvarial bone loss in mice lacking EP receptor signaling to definitively address signals involved in RANKL induction, osteoclast formation, gene expression, and osteolysis. The role of the synovial fibroblast will be confirmed by conditional deletion of the EP4 receptor in fibroblasts. Thus through a series of highly integrated in vitro and in vivo experiments, the competitive renewal advances the findings of the initial funding period. The use of transgenic models and state of the art methods will characterize the sequential events of NFicB activation, COX-2 and PGES1 expression, PGE2 secretion, EP4 receptor binding, and RANKL expression in SF as a critical event in osteolysis.