Department of Pathology, Duke University, School of Medicine, Durham, NC 27710, USA; Duke Molecular Physiology Institute and Division of Rheumatology, Department of Medicine, Duke University School of Medicine, Durham, NC 27701, USA.
Department of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC 27710, USA.
Osteoarthritis Cartilage. 2018 Feb;26(2):245-254. doi: 10.1016/j.joca.2017.10.019. Epub 2017 Nov 9.
To explore mechanisms underlying the association of TSG-6 with osteoarthritis (OA) progression.
TSG-6-mediated heavy chain (HC) transfer (TSG-6 activity) and its association with inflammatory mediators were quantified in knee OA (n=25) synovial fluids (SFs). Paired intact and damaged cartilages from the same individuals (20 tibial and 12 meniscal) were analyzed by qRT-PCR and immunohistochemistry (IHC) for gene and protein expression of TSG-6 and components of Inter-alpha-Inhibitor (IαI) and TSG-6 activity ± spiked in IαI. Primary chondrocyte cultures (n=5) ± IL1β or TNFα were evaluated for gene expression. The effects of TSG-6 activity on cartilage extracellular matrix (ECM) assembly were explored using quantitative hyaluronan (HA)-aggrecan binding assays.
TSG-6 activity was significantly associated (R > 0.683, P < 0.0002) with inflammatory mediators including TIMP-1, A2M, MMP3, VEGF, VCAM-1, ICAM-1 and IL-6. Although TSG-6 protein and mRNA were highly expressed in damaged articular and meniscal cartilage and cytokine-treated chondrocytes, there was little or no cartilage expression of components of the IαI complex (containing HC1). By IHC, TSG-6 was present throughout lesioned cartilage but HC1 only at lesioned surfaces. TSG-6 impaired HA-aggrecan assembly, but TSG-6 mediated HA-HC formation reduced this negative effect.
TSG-6 activity is a global inflammatory biomarker in knee OA SF. IαI, supplied from outside cartilage, only penetrates the cartilage surface, restricting TSG-6 activity (HC transfer) to this region. Therefore, unopposed TSG-6 in intermediate and deep regions of OA cartilage could possibly block matrix assembly, leading to futile synthesis and account for increased risk of OA progression.
探究 TSG-6 与骨关节炎（OA）进展相关的作用机制。
在膝关节 OA（n=25）滑液中定量检测 TSG-6 介导的重链（HC）转移（TSG-6 活性）及其与炎症介质的关联。对来自同一患者的完整和受损软骨（20 个胫骨和 12 个半月板）进行配对分析，通过 qRT-PCR 和免疫组化（IHC）检测 TSG-6 及其组成成分（Inter-alpha-Inhibitor，IαI）和 TSG-6 活性的基因和蛋白表达，同时评估 IαI 中 TSG-6 活性是否存在外加尖峰。对 5 例原发性软骨细胞培养物（n=5）±IL1β 或 TNFα 进行基因表达评估。通过定量透明质酸（HA）-聚集蛋白聚糖结合试验探讨 TSG-6 活性对软骨细胞外基质（ECM）组装的影响。
TSG-6 活性与炎症介质显著相关（R > 0.683，P < 0.0002），包括 TIMP-1、A2M、MMP3、VEGF、VCAM-1、ICAM-1 和 IL-6。尽管 TSG-6 蛋白和 mRNA 在受损关节软骨和半月板软骨以及细胞因子处理的软骨细胞中高度表达，但 IαI 复合物的组成成分（包含 HC1）在软骨中表达很少或没有。通过 IHC，TSG-6 存在于整个病变软骨中，但 HC1 仅存在于病变表面。TSG-6 损害了 HA-聚集蛋白聚糖的组装，但 TSG-6 介导的 HA-HC 形成减少了这种负面影响。
TSG-6 活性是膝关节 OA SF 中的一种全身性炎症生物标志物。IαI 来自软骨外，仅穿透软骨表面，从而限制了 TSG-6 活性（HC 转移）在该区域的作用。因此，OA 软骨中间和深层区域未受抑制的 TSG-6 可能会阻止基质组装，导致无效合成，并解释了 OA 进展风险增加的原因。
