Same same but different? How blood and lymphatic vessels induce cell contact inhibition.

Endothelial cells (ECs) migrate, sprout, and proliferate in response to (lymph)angiogenic mitogens, such as vascular endothelial growth factors. When ECs reach high confluency and encounter spatial confinement, they establish mature cell-cell junctions, reduce proliferation, and enter a quiescent state through a process known as contact inhibition. However, EC quiescence is modulated not only by spatial confinement but also by other mechano-environmental factors, including blood or lymph flow and extracellular matrix properties. Changes in physical forces and intracellular signaling can disrupt contact inhibition, resulting in aberrant proliferation and vascular dysfunction. Therefore, it is critical to understand the mechanisms by which endothelial cells regulate contact inhibition. While contact inhibition has been well studied in blood endothelial cells (BECs), its regulation in lymphatic endothelial cells (LECs) remains largely unexplored. Here, we review the current knowledge on extrinsic stimuli and intrinsic molecular pathways that govern endothelial contact inhibition and highlight nuanced differences between BECs and LECs. Furthermore, we provide perspectives for future research on lymphatic contact inhibition. A deeper understanding of the BEC and LEC-specific pathways underlying contact inhibition may enable targeted modulation of this process in blood or lymphatic vessels with relevance to lymphatic or blood vascular-specific disorders.