Endothelial Sprout Formation Is Regulated by Substrate Stiffness and Notch Signaling

Angiogenesis, the process of vessel formation from pre-existing ones, is modulated by the local stiffness of the extracelluar matrix. We have previously shown that Notch signaling, a key pathway in angiogenesis, responds to substrate stiffness in endothelial cells. In the current work, we investigate the contribution of Notch signaling in angiogenesis-related in vitro assays by using VEGF and Notch inhibitors as perturbations. In addition, we investigate Notch signaling in relation to the stiffness of the respective endothelial microenvironment. While the tube formation assay on Matrigel is clearly influenced by substrate stiffness, Notch signaling seems to play no major role in this context. In contrast, spheroid sprouting is influenced by stiffness as well as Notch signaling; with decreasing stiffness, both sprouting and Notch signaling are increased. This finding adds a functional aspect to the mechanosensitivity of Notch signaling.