Cartilage Degeneration and Repair By ADAMTSs and Hyaluronan Binding Proteins

描述(申请人提供)：骨关节炎的风险因素包括关节损伤、肥胖、衰老和遗传。标志性症状是关节僵硬和肿胀并伴随疼痛，并伴有进行性组织变化，包括软骨侵蚀、滑膜纤维化、半月板撕裂和骨骼重塑。临床上似乎已经达成共识，任何可以预防或逆转软骨丢失的治疗方法都最有可能为患者提供长期的结构性和症状性益处。在寻找骨性关节炎的中枢疾病途径的过程中，软骨细胞异常肥大已成为可能的候选因素之一。在这个范例中，骨性关节炎是由于关节软骨细胞的“激活”而形成肥大和自溶的表型，从而使软骨退化。然而，最近对正常和骨性关节炎软骨中基因表达的多项研究有力地支持了这一观点，即软骨破坏是由于转化生长因子β1诱导的促纤维化基因表达增强而不是细胞分化为肥大表型所致。我们的研究正在解决一个中心问题：转化生长因子？1信号一方面导致纤维化，另一方面导致软骨修复的机制是什么？如果详细了解这一机制，它似乎提供了一个独特的机会，通过治疗干预骨性关节炎的启动和进展。我们最近对小鼠骨性关节炎模型的研究表明，ADAMTS5的基因敲除非常有效地防止了关节周围组织的纤维化和软骨侵蚀。ADAMTS5的致病作用似乎主要是由于其在间充质软骨前体细胞周围的活性，在那里它切割聚集素并促进其向肌成纤维细胞而不是软骨细胞分化。为了研究这一途径，我们使用ADAMTS5的条件消融，特别是在间充质祖细胞中，来确定这种方法是否会保护小鼠免受生物力学诱导的骨关节炎的影响。我们还比较了目前临床使用的关节内注射剂(BMP7和HA)在小鼠骨关节炎模型中阻止纤维化和增强软骨生成的能力。为了实现这些目标，我们使用了成纤维和成软骨基因的定量聚合酶链式反应，基因表达的siRNA沉默，细胞的共聚焦和双光子显微镜，以及定量软骨深度和表面分析的CT。

DESCRIPTION (provided by applicant): Risk factors for osteoarthritis (OA) include joint injury, obesity, aging and heredity. Hallmark symptoms are joint stiffness and swelling with associated pain, and these are accompanied by progressive tissue changes which include cartilage erosion, synovial fibrosis, meniscal tears and bony remodeling. There appears to be a clinical consensus that any treatment which can prevent or reverse cartilage loss is most likely to provide long-term structural and symptomatic benefit for the patient. In the search for a central disease pathway for OA, abnormal chondrocyte hypertrophy has emerged as one possible candidate. In this paradigm, OA results from an "activation" of articular chondrocytes to the hypertrophic and autolytic phenotype which degrades the cartilage. However, multiple recent studies of gene expression in normal and OA cartilages strongly support the contention that the cartilage destruction results from an enhanced TGF?1-induced profibrotic gene expression rather than from differentiation of cells to a hypertrophic phenotype. Our research is addressing the central question: What is the mechanism by which TGF?1 signaling leads to fibrosis on the one hand and cartilage repair on the other?" If this mechanism was understood in detail, it would seem to offer a unique opportunity to intervene therapeutically in OA initiation and progression. Our recent studies with murine OA models, have illustrated that gene knockout of ADAMTS5 very effectively prevents fibrosis of periarticular joint tissues and cartilage erosion. The pathogenic role of ADAMTS5 appears to be primarily due to its activity around mesenchymal chondroprogenitors, where it cleaves aggrecan and promotes their differentiation to myofibroblasts rather than chondrocytes. To investigate this pathway we are using conditional ablation of ADAMTS5, specifically in mesenchymal progenitor cells, to determine if this approach will protect mice from biomechanically-induced OA. We are also comparing the capacity of intra-articular injectables (BMP7 and HA), which are currently in clinical use, to block fibrosis and enhance chondrogenesis in murine OA models. To achieve these objectives we are using QPCR of fibrogenic and chondrogenic genes, siRNA silencing of gene expression, confocal and 2-photon microscopy of cells and ?CT for quantitative cartilage depth and surface analysis.