The DNA methylation drift of the atherosclerotic aorta increases with lesion progression

Background: Atherosclerosis severity-independent alterations in DNA methylation, a reversible and highly regulated DNA modification, have been detected in aortic atheromas, thus supporting the hypothesis that epigenetic mechanisms participate in the pathogenesis of atherosclerosis. One yet unaddressed issue is whether the progression of atherosclerosis is associated with an increase in DNA methylation drift in the vascular tissue. The purpose of the study was to identify CpG methylation profiles that vary with the progression of atherosclerosis in the human aorta. Methods: We interrogated a set of donor-matched atherosclerotic and normal aortic samples ranging from histological grade III to VII, with a high-density (> 450,000 CpG sites) DNA methylation microarray. Results: We detected a correlation between histological grade and intra-pair differential methylation for 1,985 autosomal CpGs, the vast majority of which drifted towards hypermethylation with lesion progression. The identified CpG loci map to genes that are regulated by known critical transcription factors involved in atherosclerosis and participate in inflammatory and immune responses. Functional relevance was corroborated by crossing the DNA methylation profiles with expression data obtained in the same human aorta sample set, by a transcriptome-wide analysis of murine atherosclerotic aortas and from available public databases. Conclusions: Our work identifies for the first time atherosclerosis progression-specific DNA methylation profiles in the vascular tissue. These findings provide potential novel markers of lesion severity and targets to counteract the progression of the atheroma.