Quantification of VEGFRs, NRP1, and PDGFRs on Endothelial Cells and Fibroblasts Reveals Serum, Intra-Family Ligand, and Cross-Family Ligand Regulation

Computational modeling of angiogenesis is limited by a lack of experimental data on angiogenic receptor levels. Recent receptor profiling quantified vascular endothelial growth factor receptors (VEGFRs); however data on other angiogenic receptors, such as platelet derived growth factor receptors (PDGFRs), are also necessary for the development of an accurate angiogenesis model. Here, we establish conditions for membrane PDGFR quantification. Additionally, we determine how several environmental conditions control membrane PDGFR levels on human dermal fibroblasts. We demonstrate that membrane PDGFRβ concentrations are negatively correlated with both media serum concentration and cell growth rate, in vitro. We also show VEGF-A₁₆₅-mediated downregulation of membrane PDGFRα (~25%) and PDGFRβ (~30%), following a 24-h treatment. This supports the idea that VEGF-A₁₆₅ acts independently of VEGFRs to signal through PDGFRα and PDGFRβ. We observe that PDGF-AA and PDGF-AB downregulate membrane PDGFRα by up to 55 and 75%, respectively, while having little to no effect on PDGFRβ or NRP1. We observe that PDGF-BB effects both PDGFRs and NRP1: membrane PDGFRα and PDGFRβ were downregulated by up to 70 and 90%, respectively, whereas membrane NRP1 was upregulated by up to 40%. These data provide the necessary insight to accurately represent PDGFRs in angiogenesis models, while offering new insight into the regulation of membrane PDGFRs.