Comparison of Angiogenic and Lymphangiogenic Cell Surface Signals in HUVECs and HLECs
- Thomas Vandergon, Professor of Biology, Pepperdine University
- Donna Nofziger Plank, Associate Professor of Biology, Pepperdine University
Angiogenesis and lymphangiogenesis must occur and be coordinated whenever blood flow demand increases. Both of these processes are regulated via vascular endothelial growth factors (VEGFs) emitted from the source tissue requiring increased blood flow. VEGF signals bind to receptors on target cell surfaces and elicit growth responses including up-regulation and down-regulation of cell surface receptor molecules such as VEGF receptors (2 and 3), Delta-Like Ligand (DLL4) and Notch 1. The current general consensus is that VEGF A signal molecules binding VEGF R2 regulate angiogenesis while VEGF C signal molecules binding VEGF R3 regulate lymphangiogenesis. However, cross talk between both signals and receptors is known to occur. We attempted to characterize the signaling responses in angiogenesis and lymphangiogenesis using angiogenic model cells (HUVECs) and lymphangiogenic model cells (HLECs). We hypothesized that VEGF A would elicit a greater signaling response in HUVECs relative to HLECs and VEGF C would elicit the opposite response. We exposed both cell types at different confluence levels to VEGF A, VEGF C or combined A and C signals, then determined the relative levels of VEGF R2, VEGF R3, DLL4, and Notch1 cell surface expression using flow cytometry. In general, the 80% confluence samples showed a stronger signal both for cell numbers and relative increase in fluorescent intensity. In 80% confluent HUVECs, VEGF R2 levels were lower with VEGF A signaling relative to VEGF C. In 80% confluent HLECs, VEGF R3 levels were lower with VEGF C signaling relative to VEGF A. Delta-Like Ligand and Notch 1 signals did not show a consistent signal response pattern. Our results indicate that cell confluence has an effect on signal strength probably due to increased intercellular communication.