Thoracic aortic dissection (TAD) is a severe disease with limited understandings in its pathogenesis. Altered DNA methylation has been revealed to be involved in many diseases etiology. Few studies have examined the role of DNA methylation in the development of TAD. This study explored alterations of the DNA methylation landscape in TAD and examined the potential role of cell-free DNA (cfDNA) methylation as a biomarker in TAD diagnosis. Ascending aortic tissues from TAD patients (Stanford type A; n = 6) and healthy controls (n = 6) were first examined via whole-genome bisulfite sequencing (WGBS). While no obvious global methylation shift was observed, numerous differentially methylated regions (DMRs) were identified, with associated genes enriched in the areas of vasculature and heart development. We further confirmed the methylation and expression changes in homeobox (Hox) clusters with 10 independent samples using bisulfite pyrosequencing and quantitative real-time PCR (qPCR). Among these, HOXA5, HOXB6 and HOXC6 were significantly down-regulated in TAD samples relative to controls. To evaluate cfDNA methylation pattern as a biomarker in TAD diagnosis, cfDNA from TAD patients (Stanford type A; n = 7) and healthy controls (n = 4) were examined by WGBS. A prediction model was built using DMRs identified previously from aortic tissues on methylation data from cfDNA. Both high sensitivity (86%) and specificity (75%) were achieved in patient classification (AUC = 0.96). These findings showed an altered epigenetic regulation in TAD patients. This altered epigenetic regulation and subsequent altered expression of genes associated with vasculature and heart development, such as Hox family genes, may contribute to the loss of aortic integrity and TAD pathogenesis. Additionally, the cfDNA methylation in TAD was highly disease specific, which can be used as a non-invasive biomarker for disease prediction.

中文翻译：

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改变的 DNA 甲基化模式揭示了 Hox 基因在胸主动脉夹层中的表观遗传调控，并作为疾病诊断的生物标志物

胸主动脉夹层（TAD）是一种严重的疾病，对其发病机制的了解有限。已发现改变的 DNA 甲基化与许多疾病的病因有关。很少有研究检查 DNA 甲基化在 TAD 发展中的作用。本研究探讨了 TAD 中 DNA 甲基化景观的变化，并检查了游离 DNA (cfDNA) 甲基化作为生物标志物在 TAD 诊断中的潜在作用。首先通过全基因组亚硫酸氢盐测序 (WGBS) 检查来自 TAD 患者（斯坦福 A 型；n = 6）和健康对照（n = 6）的升主动脉组织。虽然没有观察到明显的全球甲基化转变，但发现了许多差异甲基化区域 (DMR)，相关基因在脉管系统和心脏发育区域富集。我们使用亚硫酸氢盐焦磷酸测序和定量实时 PCR (qPCR) 进一步证实了同源框 (Hox) 簇中的甲基化和表达变化，其中包含 10 个独立样本。其中，与对照相比，TAD 样品中的 HOXA5、HOXB6 和 HOXC6 显着下调。为了评估 cfDNA 甲基化模式作为 TAD 诊断中的生物标志物，WGBS 检查了来自 TAD 患者（斯坦福 A 型；n = 7）和健康对照（n = 4）的 cfDNA。使用先前从主动脉组织中鉴定的 DMR 基于 cfDNA 的甲基化数据建立了一个预测模型。在患者分类中实现了高灵敏度 (86%) 和特异度 (75%) (AUC = 0.96)。这些发现表明 TAD 患者的表观遗传调控发生了改变。这种改变的表观遗传调控和随后改变的与脉管系统和心脏发育相关的基因（例如 Hox 家族基因）的表达可能导致主动脉完整性和 TAD 发病机制的丧失。此外，TAD 中的 cfDNA 甲基化具有高度的疾病特异性，可用作疾病预测的非侵入性生物标志物。