Synovial mast cells in inflammatory arthritis

描述（由申请人提供）：20世纪80年代，类风湿关节炎（RA）患者关节中活化肥大细胞（MCs）数量升高，提出了MCs参与炎症、蛋白水解损伤和/或关节炎关节重塑的可能性。我们和其他人随后利用mc缺陷小鼠证明，这些免疫细胞确实在实验性炎症性关节炎中发挥了重要作用。然而，尚未发现滑膜中Fc3RIII-和c5a激活的MCs产生的相关介质对关节产生不利影响。小鼠mcp蛋白酶（mMCP） 6和mMCP-7是染色体17A3.3色氨酸蛋白酶家族的成员，它们作为与含肝素的serglycin蛋白聚糖离子结合的同型和异型四聚体优先储存在MCs的分泌颗粒中。mMCP-6的人类同源基因是htrypase -21。我们生成了酶活性的mMCP-6、mMCP-7和htrypase -21。我们最近还创建了近交转基因C57BL/6小鼠品系，它们在mMCP-6、mMCP-7和肝素的表达上存在差异。使用后者小鼠，我们发现缺乏胰蛋白酶7肝素复合物的C57BL/6小鼠在两种不同的炎症性关节炎小鼠模型中减少了炎症和软骨聚集蛋白多糖的损失。拟议研究的总体目标是使用互补的方法在分子水平上确定小鼠和人类四聚体形成胰蛋白酶在类风湿性关节炎和这种自身免疫性疾病的小鼠模型中的作用。我们的转基因小鼠菌株、重组胰蛋白酶和其他关键蛋白酶特异性试剂将用于拟议的研究，以确定mc限制性四聚体形成的人和小鼠胰蛋白酶如何在不同的体外和体内研究中在多个水平上影响成纤维细胞样滑膜细胞（FLS）和软骨细胞，以及这些间充质细胞如何影响MCs。进一步的研究将确定胞外分泌的mMCP-6和htrypase -21在关节炎关节，甚至在MCs本身中是如何负调控的。控制MCs内酶活性胰蛋白酶表达的因素和机制尚未确定。为此，我们最近发现fls衍生的IL-33诱导MCs在mRNA和蛋白水平上增加胰蛋白酶的表达。因此，我们提出了更多的机制研究，以了解IL-33如何控制mcp -6和htrypase -21基因在MCs中的转录和/或其转录的稳定性。综上所述，这些研究有望为MC和滑膜生理学提供新的见解，并阐明人类炎症性关节炎的新疾病机制。

DESCRIPTION (provided by applicant): The presence of elevated numbers of activated mast cells (MCs) in the joints of patients with rheumatoid arthritis (RA) raised the possibility in the 1980s that MCs participate in the inflammation, proteolytic damage, and/or remodeling of the arthritic joint. Using MC-deficient mice, we and others subsequently demonstrated that these immune cells do indeed contribute substantially to experimental inflammatory arthritis. Nevertheless, the relevant mediators produced by the Fc3RIII- and C5a-activated MCs in the synovium that adversely affect the joint had not been identified. Mouse MC protease (mMCP) 6 and mMCP-7 are members of the chromosome 17A3.3 family of tryptic proteases that are preferentially stored in the secretory granules of MCs as homotypic and heterotypic tetramers ionically bound to heparin-containing serglycin proteoglycans. The human ortholog of mMCP-6 is hTryptase-21. We generated enzymatically active mMCP-6, mMCP-7, and hTryptase-21. We also recently created inbred transgenic C57BL/6 mouse strains that differ in their expression of mMCP-6, mMCP-7, and heparin. Using the latter mice, we showed that C57BL/6 mice that lack tryptase7heparin complexes have reduced inflammation and diminished loss of aggrecan proteoglycans from their cartilage in two different mouse models of inflammatory arthritis. The overall objectives of the proposed studies are to use complementary approaches to determine at the molecular level the roles of mouse and human tetramer-forming tryptases in RA and mouse models of this autoimmune disorder. Our genetically modified mouse strains, recombinant tryptases, and other key protease-specific reagents will be used in the proposed studies to determine how MC-restricted tetramer-forming human and mouse tryptases affect fibroblast-like synoviocytes (FLS) and chondrocytes at multiple levels in varied in vitro and in vivo studies, as well as how these mesenchymal cells affect MCs. Additional studies will be carried out to determine how exocytosed mMCP-6 and hTryptase-21 are negatively regulated in the arthritic joint, and even in MCs themselves. The factors and mechanisms that control the expression of enzymatically active tryptases inside MCs have not been identified. To this end, we recently discovered that FLS-derived IL-33 induces MCs to increase their expression of tryptases at the mRNA and protein levels. Thus, additional mechanistic studies are proposed to understand how IL-33 controls the transcription of the mMCP-6 and hTryptase-21 genes in MCs and/or the stability of their transcripts. In combination, these studies promise to provide novel insights into both MC and synovial physiology, as well as elucidate novel disease mechanisms in human inflammatory arthritis.