Gawri Rahul, Rosenzweig Derek H, Krock Emerson, Ouellet Jean A, Stone Laura S, Quinn Thomas M, Haglund Lisbet
Arthritis Res Ther. 2014 Jan 23;16(1):R21. doi: 10.1186/ar4449.
Excessive mechanical loading of intervertebral discs (IVDs) is thought to alter matrix properties and influence disc cell metabolism, contributing to degenerative disc disease and development of discogenic pain. However, little is known about how mechanical strain induces these changes. This study investigated the cellular and molecular changes as well as which inflammatory receptors and cytokines were upregulated in human intervertebral disc cells exposed to high mechanical strain (HMS) at low frequency. The impact of these metabolic changes on neuronal differentiation was also explored to determine a role in the development of disc degeneration and discogenic pain.
Isolated human annulus fibrosus (AF) and nucleus pulposus (NP) cells were exposed to HMS (20% cyclical stretch at 0.001 Hz) on high-extension silicone rubber dishes coupled to a mechanical stretching apparatus and compared to static control cultures. Gene expression of Toll-like receptors (TLRs), neuronal growth factor (NGF) and tumour necrosis factor α (TNFα) was assessed. Collected conditioned media were analysed for cytokine content and applied to rat pheocromocytoma PC12 cells for neuronal differentiation assessment.
HMS caused upregulation of TLR2, TLR4, NGF and TNFα gene expression in IVD cells. Medium from HMS cultures contained elevated levels of growth-related oncogene, interleukin 6 (IL-6), IL-8, IL-15, monocyte chemoattractant protein 1 (MCP-1), MCP-3, monokine induced by γ interferon, transforming growth factor β1, TNFα and NGF. Exposure of PC12 cells to HMS-conditioned media resulted in both increased neurite sprouting and cell death.
HMS culture of IVD cells in vitro drives cytokine and inflammatory responses associated with degenerative disc disease and low-back pain. This study provides evidence for a direct link between cellular strain, secretory factors, neoinnervation and potential degeneration and discogenic pain in vivo.
椎间盘（IVD）的过度机械负荷被认为会改变基质特性并影响椎间盘细胞代谢，从而导致椎间盘退变和椎间盘源性疼痛的发生。然而，关于机械应变如何诱导这些变化，我们知之甚少。本研究调查了在低频下暴露于高机械应变（HMS）的人椎间盘细胞中的细胞和分子变化，以及哪些炎症受体和细胞因子上调。还探讨了这些代谢变化对神经元分化的影响，以确定其在椎间盘退变和椎间盘源性疼痛发展中的作用。
将分离的人纤维环（AF）和髓核（NP）细胞置于与机械拉伸装置相连的高延伸硅橡胶培养皿上，暴露于HMS（0.001Hz下20%的周期性拉伸），并与静态对照培养物进行比较。评估Toll样受体（TLR）、神经生长因子（NGF）和肿瘤坏死因子α（TNFα）的基因表达。分析收集的条件培养基中的细胞因子含量，并将其应用于大鼠嗜铬细胞瘤PC12细胞以评估神经元分化。
HMS导致IVD细胞中TLR2、TLR4、NGF和TNFα基因表达上调。HMS培养物的培养基中生长相关癌基因、白细胞介素6（IL-6）、IL-8、IL-15、单核细胞趋化蛋白1（MCP-1）、MCP-3、γ干扰素诱导的单核因子、转化生长因子β1、TNFα和NGF的水平升高。将PC12细胞暴露于HMS条件培养基中导致神经突萌发增加和细胞死亡。
体外IVD细胞的HMS培养驱动了与椎间盘退变和下腰痛相关的细胞因子和炎症反应。本研究为细胞应变、分泌因子、神经新生与体内潜在退变和椎间盘源性疼痛之间的直接联系提供了证据。
