Key Role of Estrogens and Endothelial Estrogen Receptor α in Blood Flow–Mediated Remodeling of Resistance Arteries
Objective—Flow- (shear stress–)mediated outward remodeling of resistance arteries is involved in collateral growth during postischemic revascularization. As this remodeling is especially important during pregnancy, we hypothesized that estrogens may be involved. A surgical model eliciting a local increase in blood flow in 1 mesenteric resistance artery was used in 3-month-old ovariectomized female rats either treated with 17-β-estradiol (E2) or left untreated.
Methods and Results—After 14 days, arterial diameter was greater in high-flow arteries than in normal-flow vessels. An ovariectomy suppressed high-flow remodeling, while E2 restored it. High-flow remodeling was absent in mice lacking the estrogen receptor α but not estrogen receptor β. The kinetics of inflammatory marker expression, macrophage infiltration, oxidative stress, and MMP expression were not altered by the absence of E2 after 2 and 4 days, that is, during remodeling. Nevertheless, E2 was required for the increase in endothelial NOS expression and activation at day 4 when diameter expansion occurs. Finally, the impact of E2 on the endothelium appeared crucial for high-flow remodeling, as this E2 action was abrogated in mice lacking endothelial NOS, as well as in Tie2-Cre(+) ERαf/f mice.
Conclusion—We demonstrate the essential role of E2 and endothelial estrogen receptor α in flow-mediated remodeling of resistance arteries in vivo.
- Received January 18, 2012.
- Accepted December 17, 2012.
- © 2013 American Heart Association, Inc.