A biphasic endothelial stress-survival mechanism regulates the cellular response to vascular endothelial growth factor A

In Vitro Co-culture of Fibroblast and Endothelial Cells to Assess Angiogenesis

Angiogenesis relies on the spatial and temporal coordination of endothelial migration and proliferation to form new blood vessels. This occurs through synchronous activation of multiple downstream pathways which facilitate vascular development. Proangiogenic growth factors and supporting extracellular matrix allow the formation of capillary-like tubules, reminiscent of microvascular beds, in vitro. In this chapter, we describe a methodology for the establishment of vascular networks by co-culture of endothelial cells and fibroblasts to facilitate the study of tubulogenic and angiogenic potential. We detail the use of siRNA mediated knockdown to deplete target genes of interest, in either the endothelial or fibroblast cells, to allow the assessment of their role in angiogenesis. Finally, we detail how these vascular networks may be stained using immunofluorescence to allow quantification of angiogenic potential in vitro.

Effect of recombinant vascular endothelial growth factor and translationally controlled tumor protein on 2‑hydroxyethyl methacrylate‑treated pulp cells

Vascular endothelial growth factor (VEGF)-A is a potential signaling protein that may promote angiogenesis. VEGF also helps cells survive in stressfull or hazardous conditions. The present study aimed to compare the effect of VEGF with translationally controlled tumor protein (TCTP), an anti‑apoptotic protein in human dental pulp cells (HDPCs), following exposure to 2‑hydroxyethyl methacrylate (HEMA), which is a major residual monomer from resin restorative dental materials. Cell viability, alkaline phosphatase (ALP) activity, mineralization and gene expressions for odontogenic and osteogenic differentiation markers of HDPCs were investigated, following exposure to HEMA and in combination with TCTP and VEGF. The results revealed that TCTP at 1 ng/ml and VEGF at 10 ng/ml significantly promoted the proliferation of HDPCs (P<0.05). TCTP (1 ng/ml) and VEGF (10 ng/ml) maintained the cell viability of 4 mM HEMA‑treated cells at the same percentage as the control. However, cells treated with HEMA+TCTP+VEGF had a lower cell viability than the groups treated with HEMA and TCTP or VEGF alone. TCTP and VEGF promoted cell proliferation, ALP activity and mineralization, and upregulated of DSPP, DMP‑1, BMP‑2, and ALP mRNA expression compared with the control. Furthermore, the HEMA+TCTP and HEMA+VEGF groups had significantly higher percentages of calcium deposition than HEMA‑treated cells (P<0.001). HEMA was cytotoxic to HDPCs, reduced ALP activity and caused the significant downregulation of odontogenic and osteogenic gene expressions (P<0.05). It was concluded that VEGF and TCTP promoted pulp cell growth and the survival of HEMA‑treated cells without synergistic effects. TCTP was required in lower concentrations for these effects. VEGF and TCTP enhanced cell differentiation and mineralization.

Detection and Quantification of Vascular Endothelial Growth Factor Receptor Tyrosine Kinases in Primary Human Endothelial Cells

Proteins differ widely in their pattern of expression depending on organism, tissue, and regulation in response to changing conditions. In the mammalian vasculature, the endothelium responds to vascular endothelial growth factors (VEGFs) via membrane-bound receptor tyrosine kinases (VEGFRs) to modulate many aspects of vascular physiology including vasculogenesis, angiogenesis, and blood pressure. Studies on VEGFR biology are thus dependent on detecting expression levels in different cell types and evaluating how changes in protein levels correlate with changing conditions including circulating VEGF levels. Here, we present a robust immunoblot-based protocol for detecting and quantifying VEGFRs in human endothelial cells. Using internal and external standards, we can rapidly evaluate receptor copy number and assess how this is altered in response to the cellular environment.

Identification of Receptor Tyrosine Kinase Inhibitors Using Cell Surface Biotinylation and Affinity Isolation

The mammalian vascular endothelial growth factor receptor tyrosine kinases (VEGFRs) bind circulating growth factors and regulate the process of angiogenesis. The discovery of new small molecules that target the enzymatic activity of the VEGFR family as potential antiangiogenic drugs is of much commercial interest in the pharmaceutical sector. Here, we describe the use of a combined cell surface biotinylation and affinity isolation procedure to monitor ligand-stimulated VEGFR trafficking in endothelial cells, in which novel VEGFR inhibitors from chemical libraries can be identified by their ability to inhibit receptor internalization. Unlike a traditional cell-free enzyme activity assay, such a cell-based approach provides a physiologically relevant readout of inhibitor activity. In this example, we use the VEGF-A-VEGFR-2 axis and the well-characterized tyrosine kinase inhibitor sunitinib as a working model; however this technique is highly applicable for the identification of inhibitors to other receptor tyrosine kinases.

Canonical and noncanonical vascular endothelial growth factor pathways: new developments in biology and signal transduction

The past 5 years have witnessed a significant expansion in our understanding of vascular endothelial growth factor (VEGF) signaling. In particular, the process of canonical activation of VEGF receptor tyrosine kinases by homodimeric VEGF molecules has now been broadened by the realization that heterodimeric ligands and receptors are also active participants in the signaling process. Although heterodimer receptors were described 2 decades ago, their impact, along with the effect of additional cell surface partners and novel autocrine VEGF signaling pathways, are only now starting to be clarified. Furthermore, ligand-independent signaling (noncanonical) has been identified through galectin and gremlin binding and upon rise of intracellular levels of reactive oxygen species. Activation of the VEGF receptors in the absence of ligand holds immediate implications for therapeutic approaches that exclusively target VEGF. The present review provides a concise summary of the recent developments in both canonical and noncanonical VEGF signaling and places these findings in perspective to their potential clinical and biological ramifications.