Division for Biochemistry of Joint and Connective Tissue Diseases, Department of Orthopedics, Ulm University, 89081 Ulm, Germany.
Institute of Orthopedic Research and Biomechanics, Trauma Research Centre, Ulm University, 89081 Ulm, Germany.
Cells. 2023 Mar 13;12(6):887. doi: 10.3390/cells12060887.
Terminal complement complex (TCC) deposition was identified in human degenerated discs. To clarify the role of terminal complement activation in disc degeneration (DD), we investigated respective activating mechanisms and cellular effects in annulus fibrosus (AF) cells. Isolated cells from human AF, nucleus pulposus (NP), and endplate (EP) were stimulated with human serum alone or with zymosan and treated with either the C3 inhibitor Cp40 or the C5 antibody eculizumab. Complement activation was determined via anaphylatoxin generation and TCC deposition detection. Thereby, induced catabolic effects were evaluated in cultured AF cells. Moreover, C5 cleavage under degenerative conditions in the presence of AF cells was assessed. Zymosan-induced anaphylatoxin generation and TCC deposition was significantly suppressed by both complement inhibitors. Zymosan induced gene expression of ADAMTS4, MMP1, and COX2. Whereas the C3 blockade attenuated the expression of ADAMTS4, the C5 blockade reduced the expression of ADAMTS4, MMP1, and COX2. Direct C5 cleavage was significantly enhanced by EP conditioned medium from DD patients and CTSD. These results indicate that terminal complement activation might be functionally involved in the progression of DD. Moreover, we found evidence that soluble factors secreted by degenerated EP tissue can mediate direct C5 cleavage, thereby contributing to complement activation in degenerated discs.
末端补体复合物（TCC）在人类退变椎间盘中有沉积。为了阐明末端补体激活在椎间盘退变（DD）中的作用，我们研究了纤维环（AF）细胞中各自的激活机制和细胞效应。从人 AF、NP 和终板（EP）中分离出的细胞，分别用人血清或酵母聚糖刺激，并分别用 C3 抑制剂 CP40 或 C5 抗体 eculizumab 处理。通过检测过敏毒素的产生和 TCC 的沉积来确定补体的激活。从而，在培养的 AF 细胞中评估诱导的分解代谢效应。此外，还评估了在存在 AF 细胞的情况下，退变条件下 C5 的切割。两种补体抑制剂均显著抑制酵母聚糖诱导的过敏毒素产生和 TCC 沉积。酵母聚糖诱导 ADAMTS4、MMP1 和 COX2 的基因表达。虽然 C3 阻断减弱了 ADAMTS4 的表达，但 C5 阻断减少了 ADAMTS4、MMP1 和 COX2 的表达。DD 患者和 CTSD 的 EP 条件培养基显著增强了直接 C5 的切割。这些结果表明末端补体激活可能在 DD 的进展中具有功能作用。此外，我们发现有证据表明，退变 EP 组织分泌的可溶性因子可介导直接 C5 的切割，从而有助于退变椎间盘中的补体激活。
