Department of Rheumatology & Clinical Immunology and Department of Experimental Immunology, Amsterdam UMC Location University of Amsterdam, Amsterdam, the Netherlands; Amsterdam Infection and Immunity Institute, Amsterdam, the Netherlands; Amsterdam Rheumatology & Immunology Center (ARC), Academic Medical Center, Amsterdam, the Netherlands.
Laboratory Genetic Metabolic Diseases, Amsterdam UMC Location University of Amsterdam, Amsterdam, the Netherlands.
J Autoimmun. 2023 Jan;134:102974. doi: 10.1016/j.jaut.2022.102974. Epub 2022 Dec 10.
Fibroblast-like synoviocytes (FLS) can augment the inflammatory process observed in synovium of patients with rheumatoid arthritis (RA). A recent transcriptomic study in synovial biopsies revealed changes in metabolic pathways before disease onset in absence of synovial tissue inflammation. This raises the question whether alterations in cellular metabolism in tissue resident FLS underlie disease pathogenesis.
To study this, we compared the metabolic profile of FLS isolated from synovial biopsies from individuals with arthralgia who were autoantibody positive but without any evidence of arthritis (RA-risk individuals, n = 6) with FLS from patients with RA (n = 6), osteoarthritis (OA, n = 6) and seronegative controls (n = 6). After synovial digestion, FLS were cultured in vitro and cellular metabolism was assessed using quantitative PCR, flow cytometry, XFe96 Seahorse Analyzer and tritium-labelled oleate oxidation assays.
Real-time metabolic profiling revealed that basal (p < 0.0001) and maximum mitochondrial respiration (p = 0.0024) were significantly lower in RA FLS compared with control FLS. In all donors, basal respiration was largely dependent on fatty acid oxidation while glucose was only highly used by FLS from RA patients. Moreover, we showed that RA-risk and RA FLS are less metabolically flexible. Strikingly, mitochondrial fatty acid β-oxidation was significantly impaired in RA-risk (p = 0.001) and RA FLS (p < 0.0001) compared with control FLS.
Overall, this study showed several metabolic alterations in FLS even in absence of synovial inflammation, suggesting that these alterations already start before clinical manifestation of disease and may drive disease pathogenesis.
成纤维样滑膜细胞（FLS）可增强类风湿关节炎（RA）患者滑膜中观察到的炎症过程。最近对滑膜活检的转录组学研究显示，在没有滑膜组织炎症的情况下，疾病发病前代谢途径发生了变化。这就提出了一个问题，即在组织驻留的 FLS 中细胞代谢的改变是否是疾病发病机制的基础。
为了研究这一点，我们比较了来自关节痛患者的滑膜活检中分离的 FLS 的代谢谱，这些患者自身抗体阳性但没有任何关节炎证据（RA 风险个体，n=6）与来自 RA（n=6）、骨关节炎（OA，n=6）和血清阴性对照者（n=6）的 FLS。在滑膜消化后，将 FLS 在体外培养，并使用定量 PCR、流式细胞术、XFe96 Seahorse 分析仪和氚标记的油酸盐氧化测定法评估细胞代谢。
实时代谢谱分析显示，与对照 FLS 相比，RA FLS 的基础（p<0.0001）和最大线粒体呼吸（p=0.0024）显著降低。在所有供体中，基础呼吸主要依赖于脂肪酸氧化，而葡萄糖仅被 RA 患者的 FLS 高度利用。此外，我们表明 RA 风险和 RA FLS 的代谢灵活性较低。引人注目的是，与对照 FLS 相比，RA 风险（p=0.001）和 RA FLS（p<0.0001）的线粒体脂肪酸β氧化明显受损。
总的来说，这项研究显示了 FLS 中的几种代谢改变，即使在没有滑膜炎症的情况下也是如此，这表明这些改变甚至在疾病的临床症状出现之前就已经开始了，并且可能驱动疾病的发病机制。
