Nuclear factor-κB-hypoxia-inducible factor-2 pathway in aortic valve stenosis

BACKGROUND AND AIM OF THE STUDY: Valvular calcification is a prominent feature of aortic valve stenosis (AS), and calcified aortic valves share several features with bone tissue. Hypoxia-inducible factor-2 (HIF-2) is activated by nuclear factor-κB (NF-κB) and plays a critical role in an osteoblastic differentiation. The study aim was to determine whether the NF-κB-HIF-2 pathway is involved in the pathophysiology of calcified aortic valve disease.

METHODS: A total of 50 specimens of aortic valve leaflets obtained from patients who had undergone aortic valve replacement for AS was examined. The aortic valve leaflets from 10 patients with annulo-aortic ectasia (AAE) served as controls. The stenotic valve leaflets were examined using immunohistochemistry to detect NF-κB, HIF-2α, vascular endothelial growth factor (VEGF), vascular endothelial cells, and collagen X. The calcification area was measured and any correlation between the calcification area and NF-κB-HIF-2 pathway was assessed.

RESULTS: NF-κB and HIF-2α were expressed in the leaflets from patients with AS, but not in those from AAE controls. Both factors were expressed around massive calcified lesions, and HIF-2α was co-localized with NF-κB. VEGF, neoangiogenesis and collagen X were located in the area where HIF-2α was expressed, and correlated positively with HIF-2α expression. The calcification area correlated positively with collagen X expression.

CONCLUSION: The NF-κB-HIF-2 pathway was expressed in calcified aortic valves and associated with an increased expression of VEGF and collagen X. This signaling pathway may play important roles in the pathophysiology of AS.