Differential promoter DNA methylation of EC-enriched genes in mouse EC and VSMC. Promoter methylation was determined using pyrosequencing of bisulfite-converted DNA. The promoters of (A) eNOS, (B) CD31, (C) VE-cadherin, and (D) vWF are unmethylated in ECs (gray) and densely methylated in VSMCs (black). Data are presented as the mean ± standard error of the mean (n = 3-7 mice studied per gene). *Statistical significance between the 2 cell types (P < .001). Previous studies by us show that the 9 CpG sites in the murine eNOS promoter (−199/−4) are completely unmethylated in ECs, whereas complete methylation was observed in AoVSMCs.⁷