BACKGROUND Intervertebral disc degeneration (IDD) is a major contributor to lower back pain, however, the molecular and pathogenetic mechanisms underlying IDD are poorly understood. As a high-risk factor for IDD, compression stress was reported to induce apoptosis of nucleus pulposus (NP) cells and extracellular matrix (ECM) degradation during IDD progression. Circular RNA (circRNA) is a class of endogenous non-coding RNA (ncRNA) and has been reported to function in several diseases. However, whether and how circRNA regulates compression-induced damage of NP cells remains vague. Here, we aimed to investigate the key role of circRNA in compression loading-induced IDD. METHODS We analysed the circRNA expression of three samples from compression-treated NP cells and three control samples using circRNA microarray assays and further investigated the circRNA involved in compression-induced damage of NP cells (circRNA-CIDN). We investigated the effects of circRNA-CIDN on compression-induced cell apoptosis and NP ECM degradation in vitro and ex vivo. We observed that circRNA-CIDN bound to miRNAs as a miRNA sponge based on luciferase and RNA immunoprecipitation (RIP) assays. FINDINGS CircRNA-CIDN was significantly downregulated in compression-treated human NP cells, as validated by circRNA microarray and qRT-PCR analysis, and overexpressing circRNA-CIDN inhibited compression-induced apoptosis and NP ECM degradation. Further studies demonstrated that circRNA-CIDN served as a sponge for miR-34a-5p, an important miRNA that enhanced compression-induced damage of NP cells via repressing the silent mating type information regulation 2 homolog 1 (SIRT1). CircRNA-CIDN was also verified to contain IDD development in an ex vivo IDD model. INTERPRETATION Our results revealed that circRNA-CIDN binding to miR-34a-5p played an important role in mitigating compression loading-induced nucleus pulposus cell damage via targeting SIRT1, providing a potential therapeutic strategy for IDD treatment. FUNDING National Natural Science Foundation of China (81772391, 81974348), Fundamental Research Funds for the Central Universities (2017KFYXJJ248).

中文翻译：

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CircRNA-CIDN通过miR-34a-5p / SIRT1轴减轻了人类髓核细胞中压缩负荷诱导的损伤。

背景技术椎间盘退变（IDD）是引起下腰痛的主要因素，但是，对IDD的分子和致病机理了解甚少。作为IDD的高危因素，据报道，压迫应力会导致IDD进展过程中髓核（NP）细胞凋亡和细胞外基质（ECM）降解。环状RNA（circRNA）是一类内源性非编码RNA（ncRNA），据报道可在多种疾病中发挥作用。然而，circRNA是否以及如何调节受压诱导的NP细胞损伤仍不清楚。在这里，我们旨在研究circRNA在压缩负荷诱导的IDD中的关键作用。方法我们使用circRNA微阵列分析法分析了压缩处理后的NP细胞中三个样品和三个对照样品中circRNA的表达，并进一步研究了circRNA参与压缩诱导的NP细胞损伤（circRNA-CIDN）。我们研究了circRNA-CIDN在体外和离体对压缩诱导的细胞凋亡和NP ECM降解的影响。我们观察到，基于荧光素酶和RNA免疫沉淀（RIP）分析，circRNA-CIDN作为miRNA海绵与miRNA结合。研究结果通过circRNA微阵列和qRT-PCR分析证实，在压缩处理的人NP细胞中CircRNA-CIDN显着下调，并且过表达circRNA-CIDN抑制了压缩诱导的细胞凋亡和NP ECM降解。进一步的研究表明，circRNA-CIDN充当miR-34a-5p的海绵，一个重要的miRNA，通过抑制沉默的交配类型信息调节2同源物1（SIRT1）来增强NP压缩诱导的损伤。还证实了CircRNA-CIDN在离体IDD模型中包含IDD发育。解释我们的结果表明，circRNA-CIDN与miR-34a-5p的结合在通过靶向SIRT1减轻压缩负荷诱导的髓核细胞损伤中发挥了重要作用，为IDD治疗提供了潜在的治疗策略。国家自然科学基金资助（81772391，81974348），中央大学基础研究基金（2017KFYXJJ248）。解释我们的结果表明，circRNA-CIDN与miR-34a-5p的结合在通过靶向SIRT1减轻压缩负荷诱导的髓核细胞损伤中发挥了重要作用，为IDD治疗提供了潜在的治疗策略。国家自然科学基金资助（81772391，81974348），中央大学基础研究基金（2017KFYXJJ248）。解释我们的结果表明，circRNA-CIDN与miR-34a-5p的结合在通过靶向SIRT1减轻压缩负荷诱导的髓核细胞损伤中发挥了重要作用，为IDD治疗提供了潜在的治疗策略。国家自然科学基金资助（81772391，81974348），中央大学基础研究基金（2017KFYXJJ248）。