Estrogen Receptor Control of Atherosclerotic Calcification and Smooth Muscle Cell Osteogenic Differentiation.
OBJECTIVE
Vascular calcification is associated with increased risk of myocardial infarction and stroke. The objective of this work was to examine the ability of 17β-estradiol (E2) to stimulate calcification of vascular smooth muscle cells (VSMC) in vivo, using aged apolipoprotein E-null mice with advanced atherosclerotic lesions, and subsequently to explore underlying mechanisms in vitro.


APPROACH AND RESULTS
Silastic E2 capsules were implanted into male and female apolipoprotein E-null mice aged 34 weeks. Plaque and calcified area were measured in the aortic sinus and innominate artery after 8 weeks. Immunohistochemical analysis examined expression of the estrogen receptors (estrogen receptor alpha and estrogen receptor beta [ERβ]). VSMC expression of osteogenic markers was examined using digital polymerase chain reaction. Advanced atherosclerotic lesions were present in all mice at the end of 8 weeks. In both male and female mice, E2 increased calcified area in a site-specific manner in the aortic sinus independently of plaque growth or lipid levels and occurred in association with a site-specific decrease in the proportion of ERβ-positive intimal cells. Calcified lesions expressed collagen I and bone sialoprotein, with decreased matrix Gla protein. In vitro, E2 suppressed ERβ expression and increased VSMC mineralization, demonstrating increased collagen I and II, osteocalcin and bone sialoprotein, and reduced matrix Gla protein and osteopontin. Antagonism or RNA silencing of estrogen receptor alpha, ERβ, or both further increased VSMC mineralization.


CONCLUSIONS
We have demonstrated that E2 can drive calcification in advanced atherosclerotic lesions by promoting the differentiation of VSMC to osteoblast-like cells, a process which is augmented by inhibition of estrogen receptor alpha or ERβ activity.
['McRobb|Lucinda S|LS|', 'McGrath|Kristine C Y|KCY|', 'Tsatralis|Tania|T|', 'Liong|Eleanore C|EC|', 'Tan|Joanne T M|JTM|', 'Hughes|Gillian|G|', 'Handelsman|David J|DJ|', 'Heather|Alison K|AK|']
D000818:Animals D001057:Apolipoproteins E D050197:Atherosclerosis D002135:Calcium-Binding Proteins D002417:Cattle D002454:Cell Differentiation D002478:Cells, Cultured D003094:Collagen D004195:Disease Models, Animal D004343:Drug Implants D004958:Estradiol D065171:Estrogen Receptor Antagonists D047628:Estrogen Receptor alpha D047629:Estrogen Receptor beta D016326:Extracellular Matrix Proteins D005260:Female D020022:Genetic Predisposition to Disease D006801:Humans D058574:Integrin-Binding Sialoprotein D008297:Male D018345:Mice, Knockout D009131:Muscle, Smooth, Vascular D032389:Myocytes, Smooth Muscle D058426:Neointima D015675:Osteocalcin D010012:Osteogenesis D053495:Osteopontin D010641:Phenotype D058226:Plaque, Atherosclerotic D034622:RNA Interference D015398:Signal Transduction D014162:Transfection D061205:Vascular Calcification
vascular calcification atherosclerosis cell differentiation estradiol receptors, estrogen