Osteopontin Level in Synovial Fluid is Associated with the Severity of Joint Pain and Cartilage Degeneration After Anterior Cruciate Ligament Rupture

骨桥蛋白（Osteopontin， OPN）是一种o糖基化磷酸化蛋白，可在多种组织和细胞中合成，包括软骨细胞和滑膜细胞。越来越多的数据表明，OPN参与炎症、免疫和骨代谢的过程。OPN敲除小鼠已经被创造出来，并显示在缺乏OPN的情况下软骨降解加速。人体研究显示，骨性关节炎和类风湿性关节炎患者的滑液中OPN蛋白水平升高。这些数据有力地表明，OPN参与关节稳态和关节炎的发病机制。然而，OPN在这些过程中的分子功能尚未得到广泛研究。在这里，我们报告滑液OPN水平与关节疼痛的严重程度有关。本研究经本研究所伦理委员会批准。所有参与这项研究的患者在手术前都给予了完整的、书面的、知情的同意。从2009年1月至2011年10月在我院行前交叉韧带重建术（ACL-R）的患者中获得了更多的样本（滑液和滑膜）。采用RT-QPCR法定量测定滑膜中OPN mRNA的表达（Roche, Light Cycler 480, Germany）。采用日本IBL公司的OPN/OPN N-half ELISA试剂盒定量测定滑膜液中总OPN蛋白水平，并与Lysholm评分、视觉模拟评分（VAS）、血清c反应蛋白（CRP）水平及软骨降解宏观观察等临床参数进行比较。如前所述，OA与ACL-R相比，滑膜中OPN mRNA表达水平和滑膜液中OPN蛋白表达水平显著升高。ACL-R组损伤后滑膜液中OPN蛋白水平逐渐降低。我们发现滑液中OPN蛋白水平与关节疼痛（VAS）的严重程度呈正相关。由于OPN通过促进巨噬细胞的迁移、存活、吞噬和促炎细胞因子的产生而发挥促炎细胞因子的作用，我们假设OPN通过促进关节炎症诱导关节疼痛。为了验证这一假设，我们研究了滑液中OPN蛋白水平与血清CRP水平的相关性。然而，我们没有观察到这两者之间的任何相关性。然而，OPN水平与关节炎症的标志——滑液体积呈正相关。少

Osteopontin (OPN) is an O-glycosylated phosphoprotein which is synthesized in a variety of tissues and cells including chondrocytes and synoviocytes. Accumulating data indicated that OPN is involved in the process of inflammation, immunity, and bone metabolism. OPN knockout mice have already been created and shown that cartilage degradation is accelerated in the absence of OPN. Human studies revealed that OPN protein level increased in the synovial fluid from the patients suffering from OA and RA. These data strongly suggest that OPN is involved in joint homeostasis and in the pathogenesis of arthritis. However, the molecular functions of OPN in these processes are not yet extensively studied. Here we report that synovial fluid OPN level is associated with the severity of joint pain.This study was approved by the Ethics Committee of this institute. All patients included in this study gave their full, written, informed consent for participation prior to the operative procedure. Tissue s … More amples (synovial fluid and synovial membrane) were obtained from the patients who underwent anterior cruciate ligament reconstruction (ACL-R) from January 2009 till October 2011 in our hospital. OPN mRNA expressed in synovial membrane was quantified by RT-QPCR (Roche, Light Cycler 480, Germany). Total OPN protein levels in synovial fluid were quantified using OPN/OPN N-half ELISA kit (IBL, Japan) and compared them with clinical parameters such as Lysholm score, visual analogue scale (VAS), serum C-reactive protein (CRP) level, and macroscopic observation of cartilage degradation.As previously reported, OPN mRNA expression level in synovial membrane and OPNprotein level in synovial fluid were significantly increased in OA if compared with those of ACL-R.In the ACL-R group, OPN protein level in synovial fluid was gradually decreased after the injury. We found that OPN protein level in synovial fluid was POSITIVELY associated with the severity of joint pain (VAS). Since OPN acts as a pro-inflammatory cytokines by enhancing migration, survival, phagocytosis, and pro-inflammatory cytokine production of macrophages, we hypothesized that OPN induces joint pain by promoting inflammation in the joint. To test this hypothesis, we investigated the correlation of OPN protein level in synovial fluid with serum CRP level. However, we did not observe any correlation between these two. However, OPN level was positively correlated with the volume of synovial fluid, a marker for joint inflammation. Less