Endothelial nitric oxide synthase alterations are independent of turbulence in the aorta of patients with a unicuspid aortic valve.

Objectives: Certain aortic valve malformations predispose to ascending aortic aneurysm, although the mechanisms are incompletely understood. The aim of this study was to determine whether turbulence across the unicuspid aortic valve (UAV) contributes to regional differences in endothelial nitric oxide (eNOS) signaling in the ascending aortic wall. Methods: Samples were collected intraoperatively from the convex and concave ascending aortic wall from 64 patients with tricuspid aortic valves (TAVs; 25 nondilated, 17 dilated), or UAVs (9 nondilated, 13 dilated). Results: In normal-sized aortas, eNOS protein was decreased in UAV compared with TAV (P = .02) whereas mRNA was similar (P = .62). eNOS protein was increased in UAV-dilated aortas compared with UAV-nondilated aortas (P = .04), whereas dilatation had no impact on eNOS protein levels in TAV aortas (P = .73). Comparing only aneurysmal aortas, we found no difference in eNOS mRNA or protein between dilated TAV and UAV aortas (P = .26, P = .76). For eNOS mRNA and protein levels in normal and dilated UAV-associated aortas, no differences were found between concavity and convexity (all P > .05). This differed from dilated TAV aortas, which showed decreased eNOS mRNA in the convexity (P = .004) whereas eNOS protein levels were similar (P = .75). Conclusions: eNOS downregulation is observed in the UAV-associated ascending aorta and is apparently independent of dilatation. No regional differences were found, however, which would be expected if eNOS changes occur due to wall shear stress. This implies a congenital defect in eNOS signaling that may be stronger than turbulence-induced expression patterns. Further research should define the role of eNOS in aortopathy associated with aortic valve disease.

Geometry of cusp and root determines aortic valve function.

The aortic valve is the functional unit of cusp and root. Various geometrical and functional analyses for the aortic valve unit have been executed to understand normal valve configuration and improve aortic valve repair. Different concepts and procedures have then been proposed for reparative approach, and aortic valve repair is still not standardized like mitral valve repair. It has become apparent, however, that interpretation of the geometry of the aortic cusp and root and its appropriate application to operative strategy lead to creating a functioning aortic valve. Herein, the aortic valve geometry and its clinical implications are reviewed to provide information for the selection of appropriate operative strategies.

Dysregulation of Endothelial Nitric Oxide Synthase Does Not Depend on Hemodynamic Alterations in Bicuspid Aortic Valve Aortopathy.

Background Bicuspid aortic valves (BAVs) predispose to ascending aortic aneurysm. Turbulent blood flow and genetic factors have been proposed as underlying mechanisms. Endothelial nitric oxide synthase (eNOS) has been implicated in BAV aortopathy, and its expression is regulated by wall shear stress. We hypothesized that if turbulent flow induces aneurysm formation in patients with a BAV, regional differences in eNOS expression would be observed in BAVs. Methods and Results Ascending aortic specimens were harvested intraoperatively from 48 patients with tricuspid aortic valve (19 dilated, 29 nondilated) and 38 with BAV (28 dilated, 10 nondilated) undergoing cardiac surgery. eNOS mRNA and protein concentration were analyzed at the convex and concave aortic wall. In nondilated aortas, eNOS mRNA and protein concentration were decreased in BAV compared with tricuspid aortic valve (all P<0.05). eNOS expression was increased in association with dilation in BAV aortas (P=0.03), but not in tricuspid aortic valve aortas (P=0.63). There were no regional differences in eNOS mRNA or protein concentration in BAV aortas (all P>0.05). However, eNOS expression was increased at the concave wall (versus convexity) in tricuspid aortic valve dilated aortas (all P<0.05). Conclusions Dysregulated eNOS occurs independent of dilation in BAV aortas, suggesting a potential role for aberrantly regulated eNOS expression in the development of BAV-associated aneurysms. The absence of regional variations of eNOS expression suggests that eNOS dysregulation in BAV aortas is the result of underlying genetic factors associated with BAV disease, rather than changes stimulated by hemodynamic alterations. These findings provide insight into the underlying mechanisms of aortic dilation in patients with a BAV.

GATA5 and endothelial nitric oxide synthase expression in the ascending aorta is related to aortic size and valve morphology.

BACKGROUND: The pathogenesis of aortic dilatation in patients with congenital aortic valve anomalies is poorly understood. Recent studies suggest that alterations of gene expression may be related to ascending aortic aneurysm formation in these patients. Knockout of endothelial nitric oxide synthase (eNOS) and GATA5 is associated with bicuspid aortic valves in mice. To study the role of eNOS and GATA5 in human congenital aortic valve disease and aortic dilatation, we investigated their gene expression in aortic tissue from patients with unicuspid, bicuspid, and tricuspid aortic valves. METHODS: Samples from 84 patients (33 tricuspid, 32 bicuspid, and 19 unicuspid) were harvested intraoperatively from the ascending aorta. GATA5 and eNOS expression was determined by real-time polymerase chain reaction. RESULTS: GATA5 and eNOS expression in the aortic wall from patients with unicuspid aortic valves (GATA5: mean [M], 2.14; standard deviation [SD], 1.72; eNOS: M, 3.40; SD, 3.83) was significantly higher than in tricuspid aortic valves (GATA5: M, 1.12; SD, 0.80; eNOS: M, 1.00; SD, 0.74; each p < 0.05). Patients with bicuspid aortic valves (GATA5: M, 1.29, SD, 1.33; eNOS: M, 1.66; SD, 1.31) had a significantly higher eNOS expression than patients with tricuspid aortic valves (p < 0.05). The expression levels of eNOS and GATA5 correlated positively with each other and negatively with the ascending aortic diameter. CONCLUSIONS: Our data suggest that GATA5, possibly through upregulation of eNOS, plays a role in the development of aortic dilatation in patients with unicuspid and bicuspid aortic valves. The differential gene expression in patients with unicuspid compared with bicuspid aortic valves suggests that the pathogenesis of both aortic valve anomalies may be different.