Increased macrophage infiltration and neovascularization in congenital bicuspid aortic valve stenosis

Abstract

Objectives: Patients with congenital bicuspid aortic valves have aortic valve stenosis at a relatively young age compared with patients with tricuspid aortic valves. We hypothesize that aortic valve stenosis evolves from a more aggressive inflammatory process, with increased macrophage/T-cell and neovessel content in congenital bicuspid aortic valveswhen compared with that seen in tricuspid valves.

Methods: Fifty-one severely stenotic aortic valves were obtained at the time of aortic valve replacement. A total of 17 bicuspid and 34 tricuspid aortic valves were evaluated. Macrophage/T-cell infiltration (CD68 plus CD3) and neovessel density (CD34) were evaluated with immunohistochemical staining. Leaflet calcification and ossification were also quantified. Real-time polymerase chain reaction was used to assess expression of chondromodulin 1 and vascular endothelial growth factor.

Results: The density of macrophages/T cells was greater in congenital bicuspid aortic valves than in tricuspid valves (51 ± 31 vs 23 ± 13 cells/mm(2), P = .002). Neovascularization was more frequently noted in congenital bicuspid aortic valves when compared with tricuspid valves (31 ± 10 vs 21 ± 9 vessels/mm(2), P = .0005), and calcification was more severe (P = .03). Expression of chondromodulin 1 demonstrated a 6-fold downregulation (P = .0003) and expression of vascular endothelial growth factor demonstrated a 2-fold increase (P = .02) in congenital bicuspid aortic valves compared with that seen in tricuspid valves. Multivariable analyses demonstrated significant associations between bicuspid aortic valve anatomy and increased inflammatory cell infiltration (β = 25.8, P = .0007) and neovascularization (β = 9.4, P = .001), despite adjusting for measured covariates.

Conclusions: The pathogenesis of aortic valve stenosis in bicuspid aortic valves is associated with a more aggressive inflammatory process with increased macrophage infiltration and neovascularization when compared with that seen in tricuspid valves.