Objective

Although cartilage degeneration and invasion of the subchondral bone plate in entheseal lesion has been considered to consequently lead bony ankylosis in ankylosing spondylitis (AS), no evident mechanisms are known.

Design

To identify histopathological and physiological changes in enthesitis-related ankylosis in AS, we performed molecular characterization of transcription factors and surface markers, and transcriptome analysis with human tissues. Entheseal tissue containing subchondral bone was obtained from the facet joints of 9 patients with AS and 10 disease controls, and assessed by using differential staining techniques. Enthesis cells were isolated, characterized, stimulated with TNF and/or IL-17A, and analysed by cell-based experimental tools.

Results

We found diffusely distributed granular tissue and cartilage in the subchondral bone in AS. Co-expression of SOX9, a specific transcription factor in cartilage, and matrix metalloproteinase 13 (MMP13) was found in the granular tissues within the subchondral bone from AS patients. Intriguingly, SOX9 expression was significantly higher in AS enthesis cells than controls and correlated with TNFR1 and IL-17RA expressions, which is important for high reactivity to TNF and IL-17A cytokines. Co-stimulation by TNF and IL-17A resulted in accelerated mineralization/calcification features, and increased OCN expression in AS enthesis cells. Furthermore, SOX9 overexpression in enthesis leads to promoting mineralization feature by TNF and IL-17A stimuli. Finally, OCN expression is elevated in the destructive enthesis of advanced AS.

Conclusion

These findings provide insight into the links between inflammation and the mineralization of entheseal tissue as the initiation of spinal ankylosis, emphasizing the importance of SOX9⁺ enthesis cells.

中文翻译：

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SOX9+ 附着细胞与强直性脊柱炎中的脊柱强直有关

客观的

尽管已认为附着点病变中的软骨退化和软骨下骨板的侵袭因此导致强直性脊柱炎（AS）中的骨强直，但尚无明显的机制。

设计

为了确定 AS 中肌腱端炎相关强直的组织病理学和生理变化，我们对转录因子和表面标志物进行了分子表征，并对人体组织进行了转录组分析。从 9 名 AS 患者和 10 名疾病对照者的小关节获得含有软骨下骨的附着组织，并使用差异染色技术进行评估。分离、表征、用 TNF 和/或 IL-17A 刺激，并通过基于细胞的实验工具进行分析。

结果

我们在 AS 的软骨下骨中发现了弥漫性分布的颗粒组织和软骨。在来自 AS 患者的软骨下骨内的颗粒组织中发现了 SOX9（一种软骨中的特异性转录因子）和基质金属蛋白酶 13 (MMP13) 的共表达。有趣的是，AS enthesis 细胞中 SOX9 的表达明显高于对照组，并且与 TNFR1 和 IL-17RA 表达相关，这对于对 TNF 和 IL-17A 细胞因子的高反应性很重要。TNF 和 IL-17A 的共同刺激导致加速矿化/钙化特征，并增加 AS 附着细胞中的 OCN 表达。此外，附着体中的 SOX9 过表达导致 TNF 和 IL-17A 刺激促进矿化特征。最后，OCN 表达在晚期 AS 的破坏性插入中升高。

结论

这些发现提供了对炎症和附着点组织矿化作为脊柱强直起始的联系的见解，强调了 SOX9 ⁺附着点细胞的重要性。