title: Aromatase is required for female abdominal aortic aneurysm protection.
abstract: OBJECTIVE
  The protective effects of female gender on the development of abdominal aortic aneurysms (AAAs) have been attributed to anti-inflammatory effects of estrogen. Estrogen synthesis is dependent on the enzyme aromatase, which is located both centrally in the ovaries and peripherally in adipose tissue, bone, and vascular smooth muscle cells. It is hypothesized that deletion of aromatase in both ovarian and peripheral tissues would diminish the protective effect of female gender and would be associated with increased aortic diameter in female mice.
  
  
  METHODS
  Male and female 8- to 10-week-old mice with aromatase (wild type: WT) and without aromatase (ArKO) underwent elastase aortic perfusion with aortic harvest 14 days following. For the contribution of central and peripheral estrogen conversion to be evaluated, female WT mice were compared with female WT and ArKO mice that had undergone ovariectomy (ovx) at 6 weeks followed by elastase perfusion at 8 to 10 weeks. At aortic harvest, maximal aortic dilation was measured and samples were collected for immunohistochemistry and protein analysis. Serum was collected for serum estradiol concentrations. Groups were compared with analysis of variance. Human and mouse AAA cross sections were analyzed with confocal immunohistochemistry for aromatase, smooth muscle markers, and macrophage markers.
  
  
  RESULTS
  Female WT mice had significant reduction in aortic dilation compared with male WT mice (F WT, 51.5% ± 15.1% vs M WT, 78.7% ± 14.9%; P < .005). The protective effects of female gender were completely eliminated with deletion of aromatase (F ArKO, 82.6% ± 13.8%; P < .05 vs F WT). Ovariectomy increased aortic dilation in WT mice (F WT ovx, 70.6% ± 11.7%; P < .05 vs F WT). Aromatase deletion with ovariectomy further increased aortic dilation compared with WT ovx mice (F ArKO ovx, 87.3% ± 14.7%, P < .001 vs F WT and P < .05 vs F WT ovx). Accordingly, female ArKO ovx mice had significantly higher levels of the proinflammatory cytokines monocyte chemoattractant protein 1 and interleukin-1β and were associated with increased macrophage staining and decreased elastin staining. Regarding serum hormone levels, decreasing estradiol levels correlated with increasing aortic diameter (R = -0.565; P < .01). By confocal immunohistochemistry, both human and mouse AAA smooth muscle cells (smooth muscle α-actin positive) and macrophages (CD68 positive or Mac-2 positive) expressed aromatase.
  
  
  CONCLUSIONS
  The protective effect of female gender on AAAs is due to estrogen synthesis and requires the presence of both ovarian and extragonadal/peripheral aromatase. Peripheral estrogen synthesis accounts for roughly half of the protective effect of female gender. If peripheral aromatase could be targeted, high levels of local estrogen could be produced and may avoid the side effects of systemic estrogen.
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
authors.forename: William F
authors.initials: WF
authors.lastname: Johnston
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
authors.forename: Morgan
authors.initials: M
authors.lastname: Salmon
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
authors.forename: Gang
authors.initials: G
authors.lastname: Su
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va.
authors.forename: Guanyi
authors.initials: G
authors.lastname: Lu
authors.affiliation: Division of Cardiothoracic Surgery, Department of Surgery, University of Virginia, Charlottesville, Va; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Va.
authors.forename: Gorav
authors.initials: G
authors.lastname: Ailawadi
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, University of Virginia, Charlottesville, Va; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Va; Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Va. Electronic address: gru6n@virginia.edu.
authors.forename: Gilbert R
authors.initials: GR
authors.lastname: Upchurch
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000201:enzymology* / Q000473:pathology; D017544:Aortic Aneurysm, Abdominal / Q000097:blood / Q000139:chemically induced / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000517:prevention & control*; D001141:Aromatase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004108:Dilatation, Pathologic; D004195:Disease Models, Animal; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D008264:Macrophages / Q000201:enzymology; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000201:enzymology; D032389:Myocytes, Smooth Muscle / Q000201:enzymology; D010052:Ovariectomy; D010053:Ovary / Q000201:enzymology / Q000601:surgery; D010196:Pancreatic Elastase; D012737:Sex Factors; D013997:Time Factors
chemical_list: D004958:Estradiol; D001141:Aromatase; C561410:CYP19A1 protein, human; D010196:Pancreatic Elastase