Center of Experimental Rheumatology, Department of Rheumatology, University Hospital, University of Zurich, 8008 Zurich, Switzerland.
Department of Physical Medicine and Rheumatology, Balgrist University Hospital, University of Zurich, 8008 Zurich, Switzerland.
Cells. 2024 Aug 23;13(17):1402. doi: 10.3390/cells13171402.
The vertebral cartilage endplate (CEP), crucial for intervertebral disc health, is prone to degeneration linked to chronic low back pain, disc degeneration, and Modic changes (MC). While it is known that disc cells express toll-like receptors (TLRs) that recognize pathogen- and damage-associated molecular patterns (PAMPs and DAMPs), it is unclear if CEP cells (CEPCs) share this trait. The CEP has a higher cell density than the disc, making CEPCs an important contributor. This study aimed to identify TLRs on CEPCs and their role in pro-inflammatory and catabolic gene expression.
Gene expression of TLR1-10 was measured in human CEPs and expanded CEPCs using quantitative polymerase chain reaction. Additionally, surface TLR expression was measured in CEPs grouped into non-MC and MC. CEPCs were stimulated with tumor necrosis factor alpha, interleukin 1 beta, small-molecule TLR agonists, or the 30 kDa N-terminal fibronectin fragment. TLR2 signaling was inhibited with TL2-C29, and TLR2 protein expression was measured with flow cytometry.
Ex vivo analysis found all 10 TLRs expressed, while cultured CEPCs lost TLR8 and TLR9 expression. TLR2 expression was significantly increased in MC1 CEPCs, and its expression increased significantly after pro-inflammatory stimulation. Stimulation of the TLR2/6 heterodimer upregulated TLR2 protein expression. The TLR2/1 and TLR2/6 ligands upregulated pro-inflammatory genes and matrix metalloproteases (MMP1, MMP3, and MMP13), and TLR2 inhibition inhibited their upregulation. Endplate resorptive capacity of TLR2 activation was confirmed in a CEP explant model.
The expression of TLR1-10 in CEPCs suggests that the CEP is susceptible to PAMP and DAMP stimulation. Enhanced TLR2 expression in MC1, and generally in CEPCs under inflammatory conditions, has pro-inflammatory and pro-catabolic effects, suggesting a potential role in disc degeneration and MC.
椎体软骨终板 (CEP) 对椎间盘健康至关重要，易发生与慢性下腰痛、椎间盘退变和 Modic 改变 (MC) 相关的退行性变。虽然已知椎间盘细胞表达识别病原体和损伤相关分子模式 (PAMPs 和 DAMPs) 的 toll 样受体 (TLR)，但尚不清楚 CEP 细胞 (CEPCs) 是否具有此特性。CEP 的细胞密度高于椎间盘，因此 CEPCs 是一个重要的贡献者。本研究旨在确定 CEPCs 上的 TLR 及其在促炎和分解代谢基因表达中的作用。
使用定量聚合酶链反应测量人 CEP 和扩增的 CEPC 中 TLR1-10 的基因表达。此外，还测量了分为非 MC 和 MC 的 CEP 表面 TLR 表达。用肿瘤坏死因子-α、白细胞介素 1β、小分子 TLR 激动剂或 30 kDa 氨基端纤维连接蛋白片段刺激 CEPCs。用 TL2-C29 抑制 TLR2 信号通路，并通过流式细胞术测量 TLR2 蛋白表达。
体外分析发现所有 10 种 TLR 均有表达，而培养的 CEPC 则失去了 TLR8 和 TLR9 的表达。MC1 CEPC 中 TLR2 表达显著增加，促炎刺激后其表达显著增加。TLR2/6 异二聚体的刺激上调了 TLR2 蛋白表达。TLR2/1 和 TLR2/6 配体上调了促炎基因和基质金属蛋白酶 (MMP1、MMP3 和 MMP13)，TLR2 抑制抑制了它们的上调。在 CEP 外植体模型中证实了 TLR2 激活的 CEP 吸收能力。
CEPCs 中 TLR1-10 的表达表明 CEP 易受 PAMP 和 DAMP 刺激。MC1 中 TLR2 表达增强，以及一般在炎症条件下的 CEPCs 中，具有促炎和促分解代谢作用，提示其在椎间盘退变和 MC 中可能具有潜在作用。
