These results and previous studies (8) demonstrate that two pathways present during valvulogenesis are also active in post-natal heart valves. In this study, we show that a VEGF-mediated pathway, signaling through KDR/VEGF-R2, results in intranuclear NFATc1 and valvular endothelial cell proliferation. A TGF-β-mediated pathway induces differentiation to a mesenchymal phenotype (8). Whether or not cross-talk between these two pathways, as has been shown in the mouse (27), occurs in post-natal valves and affects post-natal valve function or repair warrants investigation.