© 2000 by European Society of Cardiology
Copyright © 2000, European Society of Cardiology
Methylation of the estrogen receptor-
gene promoter is selectively increased in proliferating human aortic smooth muscle cells
aHeart and Lung Institute, 514 Medical Research Facility, 420 W. 12th Street, Columbus, OH 43210, USA
bComprehensive Cancer Center, College of Medicine and Public Health, The Ohio State University, Columbus, OH, USA
cCancer Biology, Johns Hopkins University, Baltimore, MD, USA
* Corresponding author. Fax: +1-614-688-5779 goldschmidt-1{at}medctr.osu.edu
Objective: Atherosclerosis is a multigenic process leading to the progressive occlusion of arteries of mid to large caliber. A key step of the atherogenic process is the proliferation and migration of vascular smooth muscle cells into the intimal layer of the arterial conduit. The phenotype of smooth muscle cells, once within the intima, is known to switch from contractile to de-differentiated, yet the regulation of this switch at the genomic level is unknown. Estrogen has been shown to regulate cell proliferation both for cancer cells and for vascular cells. However, methylation of the estrogen receptor-
gene (ER) promoter blocks the expression of ER, and thereby can antagonize the regulatory effect of estrogen on cell proliferation. We sought to determine whether methylation of the ER is differentially and selectively regulated in contractile versus de-differentiated arterial smooth muscle cells. Methods: We used Southern blot assay, combined bisulfite restriction analysis (Cobra) and restriction landmark genome scanning (RLGS-M) to determine the methylation status of ER in human aortic smooth muscle cells, either in situ (normal aortic tissue, contractile phenotype), or the same cells explanted from the aorta and cultured in vitro (de-differentiated phenotype). Results: We provide evidence that methylation of the ER in smooth muscle cells that display a proliferative phenotype is altered relative to the same cells studied within the media of non-atherosclerotic aortas. Thus, the ER promoter does not appear to be methylated in situ (normal aorta), but becomes methylated in proliferating aortic smooth muscle cells. Using a screening technique, RLGS-M, we show that alteration in methylation associated with the smooth muscle cell phenotypic switch does not seem to require heightened activity of the methyltransferase enzyme, and appears to be selective for the ER and a limited pool of genes whose CpG island becomes either demethylated or de novo methylated. Conclusions: Our data support the concept that the genome of aortic smooth muscle cells is responsive to environmental conditions, and that DNA methylation, in particular methylation of the ER, could contribute to the switch in phenotype observed in these cells.
KEYWORDS Artherosclerosis; Receptors; Smooth muscle
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  V. M. Miller and S. P. Duckles Vascular Actions of Estrogens: Functional Implications Pharmacol. Rev., June 1, 2008; 60(2): 210 - 241. [Abstract] [Full Text] [PDF]
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