Unveiling the Angiogenic Potential and Functional Decline of Valve Interstitial Cells During Calcific Aortic Valve Stenosis Progression

Valve interstitial cells (VICs) play a critical role in aortic valve calcification and angiogenic processes associated with calcific aortic valve stenosis (CAVS). Within the same valve, VICs from differently calcified regions can exhibit diverse phenotypic and functional properties. We hypothesised that VICs isolated from noncalcified (NC-VICs) and calcified (C-VICs) areas of human aortic valves possess distinct angiogenic characteristics. In this study, we isolated C-VICs and NC-VICs from 23 valves obtained after aortic valve replacement due to CAVS. Both VIC types exhibited similar phenotypes in culture, characterised by morphology, expression of mesenchymal/fibroblastic markers, proliferation and osteogenic differentiation. No significant differences were observed in the secretion of angiogenic factors, including VEGF-A, Ang-1, Ang-2, PlGF, bFGF between NC-VICs and C-VICs. However, when co-injected with endothelial colony-forming cells (ECFCs) into Matrigel implants in vivo in mice, implants containing NC-VICs showed significantly higher microvessel density compared to those with C-VICs (p < 0.001). Additionally, NC-VICs co-cultured with ECFCs expressed significantly higher levels of the perivascular markers αSMA and calponin compared to C-VICs (p < 0.001 and p < 0.05, respectively). In conclusion, our study reveals the heterogeneity in VIC plasticity within the aortic valve during CAVS. The diminished capacity of VICs from calcified areas to differentiate into perivascular cells suggests a loss of function as valve disease progresses. Furthermore, the ability of VICs to undergo perivascular differentiation may provide insights into valve homeostasis, angiogenesis and the exacerbation of calcification.