Efficient detection of differentially methylated regions in the genome of patients with thoracic aortic dissection and association with MMP2 hypermethylation

DNA methylation is known to regulate the expression of numerous genes but its role in the pathogenesis of thoracic aortic dissection (TAD) has remained largely elusive. In the present study, the DNA methylome of patients with TAD was analyzed using a methylation microarray and bisulfite pyrosequencing was used to determine whether the hypermethylation of matrix metalloproteinase 2 (MMP2) specifically is associated with TAD. Chip-based whole-DNA methylome analysis was performed on 4 male patients with TAD and 4 male healthy controls using an Illumina HumanMethylation EPIC 850K BeadChip. The resulting data were analyzed by clustering and principal component analysis, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed on the differentially methylated genes to interrogate their biological functions. Compared to the healthy controls, 3,362 loci were differentially methylated in the patients with TAD with a statistical significance of P<0.05, while 1,223 loci had a significance of P<0.01. Among these loci, 2,019 were hypermethylated and 1,343 were hypomethylated. From GO analysis within the biological process category, the MMP2, MMP14 and WNT2B genes were identified. enrichment was observed for loci involved in cellular component organization, enzyme-linked receptor protein signaling pathways (potentially having a key role in the development of cardiopulmonary function disorders) and vascular reconstruction. Bisulfite pyrosequencing of plasma samples indicated significantly increased methylation (P<0.01) of the CpG site at position 2 in the promoter of MMP2 in the TAD group relative to the healthy controls, and the mean methylation level of four CpG sites on the MMP2 gene in the TAD group was slightly higher than that in the control group, but not significantly. Hypermethylation of the MMP2 promoter may be a promising novel diagnostic and prognostic biomarker for TAD. Future studies on the epigenetics of biomarkers linked to vascular reconstruction and immune function may provide further insight into the pathogenesis and progression of TAD.