Novel roles for articular cartilage vesicles in osteoarthritis

描述（由申请人提供）： 关节软骨基质囊泡（ACV）是在正常软骨和软骨细胞培养中发现的小的膜结合细胞外细胞器。迄今为止，它们几乎完全是在关节软骨中的病理基质矿化中的作用。然而，它们在正常软骨中的存在以及ACV的作用而不是矿物质形成仍然未被探索。我们最近证明ACV含有功能性RNA，并且能够将标记的RNA和蛋白质转移到nove软骨细胞。在正常软骨细胞单层中加入1-10 5 μ g/ml的正常ACV可增加骨关节炎（OA）软骨中肥大软骨细胞的标志物。这些令人兴奋的发现表明，ACV直接与软骨细胞相互作用，并可能参与OA中观察到的细胞变化。初步数据表明，蛋白多糖在无环鸟苷与细胞周围基质结合中发挥重要作用。我们推测早期OA中蛋白多糖降解酶活性的增加促进了ACV的“流动性”，并促进了软骨中ACV-软骨细胞的相互作用。然而，ACV与基质成分结合的机制以及调节基质结合的因素的特性尚未研究。同样，对ACV细胞效应的介导因素也知之甚少。正常关节软骨细胞暴露于外源性转氨酶（TGase）酶以整合素依赖性方式促进软骨细胞肥大。由于TGAs在ACV中的含量很高，我们推测ACV中或ACV上的TGAs是诱导暴露于ACV的软骨细胞肥大表型的原因，并且这种作用是整合素依赖性的。使用猪ACV和软骨细胞，并使用来自购买的人软骨细胞的ACV复制关键实验，我们将研究以下假设：具体目的1：研究ACV与基质中的蛋白聚糖结合，ADAMTS 4和5从软骨基质释放ACV的假设。具体目标2：研究ACV中的Tgas是导致ACV暴露后软骨细胞肥大表型诱导的原因，并且这是整合素依赖性的假设。这项工作的最终目标是了解ACV在软骨中的作用，希望操纵这些细胞器的内容物或可用性可能有助于OA的治疗。

DESCRIPTION (provided by applicant): Articular cartilage matrix vesicles (ACVs) are small membrane-bound extracellular organelles found in normal cartilage and chondrocyte cultures. To date, they have almost exclusively been described in reference to their role in pathologic matrix mineralization in articular cartilage. Yet, their presence in normal cartilage and roles for ACVs other than mineral formation remain unexplored. We recently demonstrated that ACVs contain functional RNA and are able to transfer labeled RNA and protein to naove chondrocytes. The addition of 1-10 5g/ml normal ACVs to normal chondrocyte monolayers increased markers characteristic of the hypertrophic chondrocytes seen in osteoarthritic (OA) cartilage. These exciting findings suggest that ACVs directly interact with chondrocytes and may participate in the cellular changes seen in OA. Preliminary data suggest an important role for proteoglycans in binding ACVs to pericellular matrix. We hypothesize that increased activity of proteoglycan-degrading enzymes in early OA promotes ACV "mobility" and fosters ACV-chondrocyte interactions in cartilage. However, the mechanisms through which ACVs bind to matrix components and the identity of the factors modulating matrix binding are unstudied. Similarly, little is known about the factors that mediate the cellular effects of ACVs. Exposure of normal articular chondrocytes to exogenous transglutaminase (Tgase) enzymes promotes chondrocyte hypertrophy in an integrin-dependent manner. As Tgases are present in high levels in ACVs, we hypothesize that Tgases in or on ACVs are responsible for inducing the hypertrophic phenotype in chondrocytes exposed to ACVs and that this effect is integrin-dependent. Using porcine ACV and chondrocytes, and replicating key experiments with ACVs from purchased human chondrocytes, we will investigate the following hypotheses: Specific aim 1: To investigate the hypothesis that ACVs bind to proteoglycans in matrix and ADAMTS4 and 5 release ACVs from cartilage matrix. Specific aim 2: To investigate the hypothesis that Tgases in ACVs are responsible for induction of the hypertrophic phenotype seen in chondrocytes after ACV exposure and that this is integrin-dependent. The ultimate goal of this work is to understand the role of ACVs in cartilage in the hope that manipulating the contents or availability of these organelles might contribute to the treatment of OA.