Different Notch signaling in cells from calcified bicuspid and tricuspid aortic valves.

AIMS: Calcific aortic valve disease is the most common heart valve disease in the Western world. Bicuspid and tricuspid aortic valve calcifications are traditionally considered together although the dynamics of the disease progression is different between the two groups of patients. Notch signaling is critical for bicuspid valve development and NOTCH1 mutations are associated with bicuspid valve and calcification. We hypothesized that Notch-dependent mechanisms of valve mineralization might be different in the two groups. METHODS AND RESULTS: We used aortic valve interstitial cells and valve endothelial cells from patients with calcific aortic stenosis with bicuspid or tricuspid aortic valve. Expression of Notch-related genes in valve interstitial cells by qPCR was different between bicuspid and tricuspid groups. Discriminant analysis of gene expression pattern in the interstitial cells revealed that the cells from calcified bicuspid valves formed a separate group from calcified tricuspid and control cells. Interstitial cells from bicuspid calcified valves demonstrated significantly higher sensitivity to stimuli at early stages of induced proosteogenic differentiation and were significantly more sensitive to the activation of proosteogenic OPN, ALP and POSTIN expression by Notch activation. Notch-activated endothelial-to-mesenchymal transition and the corresponding expression of HEY1 and SLUG were also more prominent in bicuspid valve derived endothelial cells compared to the cells from calcified tricuspid and healthy valves. CONCLUSION: Early signaling events including Notch-dependent mechanisms that are responsible for the initiation of aortic valve calcification are different between the patients with bicuspid and tricuspid aortic valves.

Cellular Mechanisms of Aortic Valve Calcification.

Comparative in vitro study examined the osteogenic potential of interstitial cells of aortic valve obtained from the patients with aortic stenosis and from control recipients of orthotopic heart transplantation with intact aortic valve. The osteogenic inductors augmented mineralization of aortic valve interstitial cells (AVIC) in patients with aortic stenosis in comparison with the control level. Native AVIC culture of aortic stenosis patients demonstrated overexpression of osteopontin gene (OPN) and underexpression of osteoprotegerin gene (OPG) in comparison with control levels. In both groups, AVIC differentiation was associated with overexpression of RUNX2 and SPRY1 genes. In AVIC of aortic stenosis patients, expression of BMP2 gene was significantly greater than the control level. The study revealed an enhanced sensitivity of AVIC to osteogenic inductors in aortic stenosis patients, which indicates probable implication of OPN, OPG, and BMP2 genes in pathogenesis of aortic valve calcification.

[Concentration of osteoprotegerin and RANKL in blood serum of patients with aortic stenosis].

PURPOSE: to compare blood serum levels of osteoprotegerin (OPG) and soluble receptor activator of nuclear factor B ligand (sRANKL) in patients with different morphological variants of stenosis. MATERIAL AND METHODS: We included in this study 57 patients with aortic stenosis: 29 with bicuspid aortic valve (BAV) and 28 with tricuspid aortic valve (TAV). Subjects without heart diseases (n=32) were also examined. In all patients we determined lipid profile and measured serum levels of C-reactive protein, OPG and sRANKL. RESULTS: OPG levels were evaluated in all patients with aortic stenosis while evaluated sRANKL was found only in patients with BAV. Age and arterial hypertension were key risk factors for OPG/RANKL/RANK system activation. CONCLUSION: Despite differences in pathogenesis of aortic stenosis in patients with BAV and TAV processes of calcification may have common mechanisms. The data obtained correspond to the conception of importance of OPG/RANKL/RANK system activation for development and progression of degenerative aortic stenosis.

[Expression of osteoprotegerin and soluble ligand of receptor of kappa-B transcription factor activator in the calcification of aortic valve]. / Ékspressiia osteoprotegerina i rastvorimogo liganda retseptora aktivatora faktora transkriptsii kappa-B pri kal'tsifikatsii aortal'nogo klapana.

The mechanism of valve calcification that is the main cause of aortic stenosis formation and progression is not yet clear. In recent years, the role of the OPG/RANKL/RANK system is considered as one of possible variants of pathogenesis of valve calcification. In presented work the differences in OPG and sRANKL levels involved in the calcification processes in tissues of patients with severe aortic stenosis have been examined. The study was performed using three groups of patients: group 1 - patients with aortic stenosis, group 2 - patients with aortic aneurysm, and group 3 - patients with aortic stenosis and aortic dilatation. In patients with aortic stenosis, the level of RANKL was significantly higher, and the level of RANKL was higher in valve than in tissue. The negative correlation between aortic dilatation and RANKL level indicated the lack of RANKL influence on pathogenesis of aortic dilatation. The obtained data confirm the increased expression of RANKL in patients with aortic valve calcification. The results of this study confirm importance of the OPG/RANKL/RANK system in calcification in patients with aortic stenosis. Athough patients of all groups had comparable values of OPG (including patients with aortic dilatation), the RANKL level increased only in patients with aortic stenosis. This suggest involvement of some additional mechanisms influencing the increase of RANKL expression.