Estradiol accelerates endothelial healing through the retrograde commitment of uninjured endothelium

Abstract

Although the accelerative effect of 17␤-estradiol (E2) on endothelial regrowth has been clearly demonstrated, the local cellular events accounting for this beneficial vascular action are still uncertain. In the present work, we compared the kinetics of endothelial healing of mouse carotid arteries after endovascular and perivascular injury. Both basal reendothelialization as well as the accelerative effect of E 2 were similar in the two models. Three days after endothelial denudation, a regenerative area was observed in both models, characterized by similar changes in gene expression after injury, visualized by en face confocal microscopy (EFCM). A precise definition of the injury limits was only possible with the perivascular model, since it causes a complete and lasting decellularization of the media. Using this model, we demonstrated that the migration of uninjured endothelial cells precedes proliferation (bromodeoxyuridine incorporation) and that these events occur at earlier time points with E2 treatment. We have also identified an uninjured retrograde zone as an intimate component of the endothelial regeneration process. Thus, in the perivascular model, the regenerative area can be subdivided into a retrograde zone and a reendothelialized area. Importantly, both areas are significantly enlarged by E2. In conclusion, the combination of the electric perivascular injury model and EFCM is well adapted to the visualization of the endothelial monolayer and to investigate cellular events involved in reendothelialization. This process is accelerated by E2 as a consequence of the retrograde commitment of an uninjured endothelial zone to migrate and proliferate, contributing to an enlargement of the regenerative area. endothelial regeneration; arterial injury; estrogen; carotid injury model; en face confocal microscopy THE INTEGRITY AND FUNCTIONALITY of the arterial endothelium, the very thin cell monolayer positioned at the interface between the blood and the vessel wall, play a crucial role in the physiology of circulation. Deendothelialization is the consequence of the treatment of coronary atherosclerosis disease by percutaneous transluminal coronary angioplasty, most often associated with intracoronary stents. One major drawback of this therapeutic approach is the residual in-stent restenosis, due to smooth muscle cell proliferation and intimal extracellular matrix accumulation. Drug-eluting stents releasing antimitotics (sirolimus and paclitaxel) efficiently prevent smooth muscle cell proliferation and, thereby, in-stent restenosis but increase the risk of late-stent thrombosis. This very serious event, commonly associated with sudden death or acute myocardial infarction, is at least partly the consequence of the inhibition of the reendothelialization of the stent struts by the antimitotics (13, 25).The endothelial healing after the injury process has previously and mostly been studied in larger animals. More than 20 years ago, a series of pioneer studies unraveled several cellular mechanisms involved in endot...

Activation function 2 (AF2) of estrogen receptor-α is required for the atheroprotective action of estradiol but not to accelerate endothelial healing

“…thelial cells that have maximal migration from the line of injury spanning the carotid obtained with the software ZEISS LSM image Borswer v.3.1 (48).…”

Estrogen Receptor α Expression in Both Endothelium and Hematopoietic Cells Is Required for the Accelerative Effect of Estradiol on Reendothelialization

“…The perivascular carotid electric injury was performed as previously described. 11,14 Briefly, surgery was carried out with a stereomicroscope (Nikon A, Mice were ovariectomized at 4 weeks of age and implanted or not with a pellet releasing E2. Carotid injury was performed at 6 weeks of age.…”

“…17␤-estradiol (E2), the main endogenous estrogen, exerts many vascular protective effects by increasing basal production of endothelial nitric oxide (NO), 13 accelerating reendothelialization 12,14 or inhibiting neointima formation. 15 We previously demonstrated that E2 accelerates reendothelialization in a mouse model of perivascular carotid injury, through estrogen receptor (ER) ␣ but not ER␤.…”

“…11 E2 increases both migration and proliferation of cultured endothelial cells in vitro, 16 and these direct actions contribute to accelerate reendothelialization in vivo. 14 In addition, E2 exerts major effects on hematopoietic cells, as mobilization of EPCs, actions on inflammatory immune cells and platelets, that could contribute to endothelial repair. 15,17 However, the respective contributions of E2 on endothelium and BM cells in this enhancing effect on the healing process have not been directly addressed.…”

Estradiol Regulation of Prostanoids Production in Endothelium

“…The endothelium exerts these actions through the release of such vasoactive compounds as prostacyclin, thromboxane A 2 , nitric oxide (NO), bradykinin, endothelin, angiotensin, and free radicals that control the functions of vascular smooth muscle cells and of circulating blood cells (Ross, 1999;Vapaatalo & Mervaala, 2001). The integrity and functionality of the arterial endothelium play a crucial role in the physiology of circulation (Filipe et al, 2008) and, as a consequence, in preventing the development of cardiovascular diseases, whose genesis is currently considered a consequence of the anatomical and functional disruption of the endothelium (Spyridopoulos et al, 1997). When the ability of the endothelial cells to release relaxing is reduced, and in particular if the propensity to produce contractile factors is enhanced, endothelial dysfunction appears as a first step in the sequence of events that leads to atherosclerosis and coronary disease.…”