The Role of Valve Endothelial Cells in Aortic Valve Calcification

Aortic valve calcification (AVC) is a leading cause of cardiovascular disease, affecting 25% of people over 75 years old. Valve interstitial cells (VICs) play a main role in calcification. Experimentally induced calcification in cultured VICs is a standard model to study AVC in vitro. It has been suggested that valve endothelial cells (VECs) may stimulate pro-osteogenic changes in the valve tissue. This study aimed to investigate the role and possible mechanisms of VECs in promoting calcification of VICs. A 2D co-culture system of human aortic VECs and VICs was established to study their interaction. In another model, extracellular vesicles (EVs) from VECs were isolated, characterized, and added to VICs. Proteomic analysis was performed on VECs from healthy and calcified valves to identify differentially expressed proteins. Co-cultivation of VECs with VICs enhanced calcification in vitro compared to VICs monocultures with p value = 0.008. Addition of VEC-derived EVs to VICs undergoing experimentally induced calcification did not promote calcification. Proteomic analysis identified 3378 proteins across all samples, with 3342 proteins present in VECs from both healthy and calcified valves. Nitric oxide synthase 3 and Hedgehog-interacting protein were increased in VECs from calcified valves with p values = 0.005 and 0.002 respectively. Further bioinformatic analysis is ongoing. VECs from calcified valves stimulated calcification of VICs. Extracellular vesicles did not mediate this effect. The proteomic profiles of VECs from healthy and calcified valves showed few differences. VECs may promote calcification in VICs by paracrine factors or direct cell-to-cell interaction.