Chondrocytes are exposed to an inflammatory micro-environment in the extracellular matrix (ECM) of articular cartilage in joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). In OA, degenerative changes and low-grade inflammation within the joint transform the behaviour and metabolism of chondrocytes, disturb the balance between ECM synthesis and degradation, and alter the osmolality and ionic composition of the micro-environment. We hypothesize that chondrocytes adjust their physiology to the inflammatory microenvironment by modulating the expression of cell surface proteins, collectively referred to as the ‘surfaceome’. Therefore, the aim of this study was to characterize the surfaceome of primary equine chondrocytes isolated from healthy joints following exposure to the pro-inflammatory cytokines interleukin-1-beta (IL-1β) and tumour necrosis factor-alpha (TNF-α). We employed combined methodology that we recently developed for investigating the surfaceome in stem cells. Membrane proteins were isolated using an aminooxy-biotinylation technique and analysed by mass spectrometry using high throughput shotgun proteomics. Selected proteins were validated by western blotting. Amongst the 431 unique cell surface proteins identified, a high percentage of low-abundance proteins, such as ion channels, receptors and transporter molecules were detected. Data are available via ProteomeXchange with identifier PXD014773. A high number of proteins exhibited different expression patterns following chondrocyte stimulation with pro-inflammatory cytokines. Low density lipoprotein related protein 1 (LPR-1), thrombospondin-1 (TSP-1), voltage dependent anion channel (VDAC) 1–2 and annexin A1 were considered to be of special interest and were analysed further by western blotting. Our results provide, for the first time, a repository for proteomic data on differentially expressed low-abundance membrane proteins on the surface of chondrocytes in response to pro-inflammatory stimuli.

中文翻译：

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响应促炎性细胞因子的软骨细胞表面组改变。

软骨细胞暴露于关节疾病（如骨关节炎（OA）和类风湿关节炎（RA））的关节软骨细胞外基质（ECM）中的炎症微环境中。在OA中，关节内的变性变化和低度炎症改变了软骨细胞的行为和代谢，扰乱了ECM合成与降解之间的平衡，并改变了微环境的重量克分子渗透压浓度和离子组成。我们假设软骨细胞通过调节细胞表面蛋白（统称为“表面组”）的表达来调节其对炎症性微环境的生理。因此，这项研究的目的是表征暴露于促炎细胞因子白介素-1-β（IL-1β）和肿瘤坏死因子-α（TNF-α）后从健康关节分离的初级马软骨细胞的表面组。我们采用了我们最近开发的用于研究干细胞表面组的组合方法。使用氨氧基生物素化技术分离膜蛋白，并使用高通量shot弹枪蛋白质组学通过质谱分析。所选蛋白质通过蛋白质印迹验证。在鉴定出的431种独特的细胞表面蛋白中，检测到高百分比的低丰度蛋白，例如离子通道，受体和转运蛋白分子。数据可通过ProteomeXchange获得，其标识符为PXD014773。在用促炎性细胞因子刺激软骨细胞后，大量蛋白质表现出不同的表达模式。低密度脂蛋白相关蛋白1（LPR-1），血小板反应蛋白1（TSP-1），电压依赖性阴离子通道（VDAC）1-2和膜联蛋白A1被认为具有特殊意义，并通过蛋白质印迹进一步分析。我们的结果首次为软骨细胞表面响应促炎性刺激的差异表达的低丰度膜蛋白的蛋白质组学数据提供了一个信息库。