Objectives
Thoracic aortic aneurysm (TAA) is typically asymptomatic but carries a high risk of fatal complications, including aortic dissections and rupture. Computed tomography angiography (CTA), the current diagnostic gold standard, is unsuitable for screening due to its unfavorable risk-benefit profile. Thus, minimally invasive biomarkers for early detection and monitoring are urgently needed. Long non-coding RNAs (lncRNAs), key regulators in cardiovascular disease, represent promising biomarker candidates. This study explores lncRNAs as potential novel biomarkers for TAA.
Methods
Our approach began with the identification of candidate lncRNAs using bulk RNA sequencing to detect altered lncRNA expression in TAA tissue compared with healthy aortic tissue, followed by single-cell RNA sequencing to determine which lncRNAs were specifically altered in vascular smooth muscle cells (VSMCs). Promising lncRNA candidates were subsequently validated by qPCR in matched tissue and blood samples from 52 TAA patients and 10 healthy controls, including region-specific analysis comparing dilated and non-dilated areas within the same TAA tissue samples. Diagnostic performance was assessed using receiver operating characteristic (ROC) curve analysis, and subgroup analyses were conducted based on aortic diameter, valve phenotype and pathology, and demographic variables.
Results
Bulk RNA sequencing identified multiple lncRNAs upregulated in TAA tissue compared with healthy controls, and single-cell RNA sequencing revealed that four of these (CASC15, MIR99AHG, NBAT1, and ADAMTS9-AS1) were predominantly expressed in VSMC subtypes. qPCR validation confirmed significant upregulation of CASC15 and MIR99AHG in TAA tissue, with higher expression in dilated versus non-dilated regions. Subgroup analyses in tissue samples showed CASC15 downregulation in aneurysms ≥52 mm and upregulation in obese patients, whereas MIR99AHG expression was higher in males, obese patients, and individuals >50 years. In contrast, both lncRNAs were downregulated in blood samples from TAA patients compared with controls. ROC analysis based on blood expression levels yielded AUC values of 0.89 for CASC15 and 0.75 for MIR99AHG.
Conclusions
Our findings identify CASC15 and MIR99AHG as TAA-associated lncRNAs mainly expressed in VSMCs, with expression patterns linked to disease progression and patient characteristics. The contrasting upregulation in aortic tissue and downregulation in blood suggests tissue-specific regulation, indicating that these lncRNAs may play distinct roles in the vascular wall remodeling. Their diagnostic performance indicates a potential role as minimally invasive biomarkers for TAA detection and monitoring. Future studies should explore the molecular mechanisms underlying their regulation and evaluate their predictive value in larger, independent cohorts to determine whether they actively contribute to aneurysm progression, exert protective effects, or primarily serve as indicators of disease state.
