Sui Yihong, Lee Jennifer H, DiMicco Michael A, Vanderploeg Eric J, Blake Simon M, Hung Han-Hwa, Plaas Anna H K, James Ian E, Song Xiao-Yu, Lark Michael W, Grodzinsky Alan J
Massachusetts Institute of Technology, Cambridge, MA 01239, USA.
Arthritis Rheum. 2009 Oct;60(10):2985-96. doi: 10.1002/art.24857.
Traumatic joint injury can damage cartilage and release inflammatory cytokines from adjacent joint tissue. The present study was undertaken to study the combined effects of compression injury, tumor necrosis factor alpha (TNFalpha), and interleukin-6 (IL-6) and its soluble receptor (sIL-6R) on immature bovine and adult human knee and ankle cartilage, using an in vitro model, and to test the hypothesis that endogenous IL-6 plays a role in proteoglycan loss caused by a combination of injury and TNFalpha.
Injured or uninjured cartilage disks were incubated with or without TNFalpha and/or IL-6/sIL-6R. Additional samples were preincubated with an IL-6-blocking antibody Fab fragment and subjected to injury and TNFalpha treatment. Treatment effects were assessed by histologic analysis, measurement of glycosaminoglycan (GAG) loss, Western blot to determine proteoglycan degradation, zymography, radiolabeling to determine chondrocyte biosynthesis, and Western blot and enzyme-linked immunosorbent assay to determine chondrocyte production of IL-6.
In bovine cartilage samples, injury combined with TNFalpha and IL-6/sIL-6R exposure caused the most severe GAG loss. Findings in human knee and ankle cartilage were strikingly similar to those in bovine samples, although in human ankle tissue, the GAG loss was less severe than that observed in human knee tissue. Without exogenous IL-6/sIL-6R, injury plus TNFalpha exposure up-regulated chondrocyte production of IL-6, but incubation with the IL-6-blocking Fab significantly reduced proteoglycan degradation.
Our findings indicate that mechanical injury potentiates the catabolic effects of TNFalpha and IL-6/sIL-6R in causing proteoglycan degradation in human and bovine cartilage. The temporal and spatial evolution of degradation suggests the importance of transport of biomolecules, which may be altered by overload injury. The catabolic effects of injury plus TNFalpha appeared partly due to endogenous IL-6, since GAG loss was partially abrogated by an IL-6-blocking Fab.
创伤性关节损伤可损害软骨，并从相邻关节组织释放炎性细胞因子。本研究采用体外模型，研究挤压伤、肿瘤坏死因子α（TNFα）、白细胞介素-6（IL-6）及其可溶性受体（sIL-6R）对未成熟牛和成人膝关节及踝关节软骨的联合作用，并验证内源性IL-6在损伤和TNFα联合导致蛋白聚糖丢失中起作用这一假说。
将损伤或未损伤的软骨盘与TNFα和/或IL-6/sIL-6R一起孵育，或不与它们孵育。另外的样本先用IL-6阻断抗体Fab片段预孵育，然后进行损伤和TNFα处理。通过组织学分析、糖胺聚糖（GAG）丢失测量、蛋白质印迹法测定蛋白聚糖降解、酶谱分析、放射性标记法测定软骨细胞生物合成以及蛋白质印迹法和酶联免疫吸附测定法测定软骨细胞IL-6的产生来评估处理效果。
在牛软骨样本中，损伤与TNFα和IL-6/sIL-6R暴露相结合导致最严重的GAG丢失。人膝关节和踝关节软骨的结果与牛样本中的结果惊人地相似，尽管在人踝关节组织中，GAG丢失不如在人膝关节组织中观察到的严重。在没有外源性IL-6/sIL-6R的情况下，损伤加TNFα暴露上调了软骨细胞IL-6的产生，但与IL-6阻断Fab孵育显著降低了蛋白聚糖降解。
我们的研究结果表明，机械损伤增强了TNFα和IL-6/sIL-6R在导致人和牛软骨中蛋白聚糖降解方面的分解代谢作用。降解的时间和空间演变表明生物分子运输的重要性，而这种运输可能因过载损伤而改变。损伤加TNFα的分解代谢作用部分似乎是由于内源性IL-6，因为IL-6阻断Fab部分消除了GAG丢失。
