Graded levels of p53 activation modulate endothelial cell fate and specification during angiogenesis

The cell cycle is a key regulator of endothelial cell specification into tip and stalk cell phenotypes, which are essential for angiogenesis in both normal development and pathological conditions. While the tumor suppressor p53 is known to regulate the cell cycle and influence cell fate, its role in the specification of endothelial cell phenotypes remains unclear. Using non-genotoxic small molecule and stapled peptide compounds to activate p53, we demonstrate that graded levels of p53 activation induce distinct cellular fates in normal endothelial cells. Low levels of p53 activation induce reversible cell cycle arrest by reducing DNA replication, while high levels induce senescence and cell death through disruptions in ribosome assembly. Surprisingly, all tested levels of p53 activation reduced the growth of venous blood vessels in vitro and in zebrafish embryo models. This reduction likely stems from distinct cellular responses in tip and stalk cells in response to p53 activation: low p53 levels primarily impaired stalk cell proliferation and elongation, whereas high levels impaired both tip and stalk cell specification. Our findings show for the first time that graded levels of p53 modulate endothelial cell fate and specification, providing new insights into the ways in which p53 regulates angiogenesis. These findings highlight the potential of using p53 modulation as a therapeutic strategy to target abnormal tip or stalk cell specification in vascular diseases, such as cancer.