背景:椎间盘(IVD)变性是导致IVD细胞活性失调的多因素病理过程。在变性期间在IVD细胞中观察到的分解代谢改变导致炎症增加,细胞外基质(ECM)降解,细胞内信号异常和细胞丢失。重要的是,已知这些病理过程是相互关联的,共同促进了疾病的进展。microRNAs(miRNAs)被认为是强大的转录后调节因子,同时靶向多个基因并调节许多细胞内途径。具体来说,miR-155-5p尤其令人感兴趣,因为已知它是促炎介质和诸如癌症和骨关节炎的疾病的促成因子。这项研究调查了miR-155-5p在IVD变性中的作用,特别关注炎症和机械传感。
方法:通过用miR-155-5p模拟物转染从退化的IVD中分离的人髓核(NP)和纤维环(AF)细胞进行功能增益和功能丧失研究。抑制剂或其相应的非靶向对照。然后使转染的细胞经受炎症环境或机械负载。收集条件培养基和细胞裂解物用于磷酸化和细胞因子分泌阵列以及基因表达分析。
结果:miR-155-5p在AF细胞中的表达增加导致在循环拉伸过程中白细胞介素(IL)-8细胞因子分泌的显著上调,在炎症过程中IL-6分泌的趋势相似。此外,miR-155-5p模拟物增加了经历循环拉伸的AF细胞中脑源性神经营养因子(BDNF)的表达。在NP细胞中,miR-155-5p的功能获得通过p38和p53的磷酸化增加导致丝裂原活化蛋白激酶(MAPK)信号通路的激活。最后,miR-155-5p抑制分别引起AF细胞中抗炎细胞因子IL-10和NP细胞中金属蛋白酶组织抑制剂(TIMP)-4的显着增加。
结论:总体而言,这些结果表明,miR-155-5p通过促炎细胞因子和MAPK信号传导增强炎症而促进IVD变性,以及通过促进机械加载过程中AF细胞的分解代谢移位。miR-155-5p的抑制可能构成IVD变性和腰背痛的潜在治疗方法。
BACKGROUND: Intervertebral disc (IVD) degeneration is a multifactorial pathological process resulting in the dysregulation of IVD cell activity. The catabolic shift observed in IVD cells during degeneration leads to increased inflammation, extracellular matrix (ECM) degradation, aberrant intracellular signaling and cell loss. Importantly, these pathological processes are known to be interconnected and to collectively contribute to the progression of the disease. MicroRNAs (miRNAs) are known as strong post-transcriptional regulators, targeting multiple genes simultaneously and regulating numerous intracellular pathways. Specifically, miR-155-5p has been of particular interest since it is known as a pro-inflammatory mediator and contributing factor to diseases like cancer and osteoarthritis. This study investigated the role of miR-155-5p in IVD degeneration with a specific focus on inflammation and mechanosensing.
METHODS: Gain- and loss-of-function studies were performed through transfection of human Nucleus pulposus (NP) and Annulus fibrosus (AF) cells isolated from degenerated IVDs with miR-155-5p mimics, inhibitors or their corresponding non-targeting control. Transfected cells were then subjected to an inflammatory environment or mechanical loading. Conditioned media and cell lysates were collected for phosphorylation and cytokine secretion arrays as well as gene expression analysis.
RESULTS: Increased expression of miR-155-5p in AF cells resulted in significant upregulation of interleukin (IL)-8 cytokine secretion during cyclic stretching and a similar trend in IL-6 secretion during inflammation. Furthermore, miR-155-5p mimics increased the expression of the brain-derived neurotrophic factor (BDNF) in AF cells undergoing cyclic stretching. In NP cells, miR-155-5p gain-of-function resulted in the activation of the mitogen-activated protein kinase (MAPK) signaling pathway through increased phosphorylation of p38 and p53. Lastly, miR-155-5p inhibition caused a significant increase in the anti-inflammatory cytokine IL-10 in AF cells and the tissue inhibitor of metalloproteinases (TIMP)-4 in NP cells respectively.
CONCLUSIONS: Overall, these results show that miR-155-5p contributes to IVD degeneration by enhancing inflammation through pro-inflammatory cytokines and MAPK signaling, as well as by promoting the catabolic shift of AF cells during mechanical loading. The inhibition of miR-155-5p may constitute a potential therapeutic approach for IVD degeneration and low back pain.