Endothelial cell activation in a VEGF-A gradient: Relevance to cell fate decisions

Abstract

Distribution of vascular endothelial cell growth factor A (VEGF-A) as a gradient determines microvascular endothelial cell (EC) fate during organogenesis. While much is understood about mechanisms of differential distribution, less is known about how EC perceive and interpret a graded VEGF-A signal to generate positional target gene activation. Using microvascular EC, we analyzed the effect of time and graded VEGF-A input on VEGFR2 autophosphorylation, signal kinase activation and induction of immediate-early genes. The threshold and time to peak activation of VEGFR2 were dependent on signal strength over a 50-fold range in concentration with 3-fold concentration differences readily distinguished. Longer duration of exposure did not compensate for low concentration of VEGF-A, suggesting intensity and duration of signal were not interpreted equivalently. With the same conditions graded and time-sensitive information was transduced through the PLCγ/p44/p42MAPK signal pathway but not the parallel AKT pathway. Analysis of MAPK-induced angiogenic immediate-early genes determined EGR-1, EGR-3, and NR4A1 were dependent on graded input while NR4A2 and DSCR1 were independent with 'switch-like' induction. These data demonstrate rapid, linear integration of VEGF-A levels but independent interpretation of duration of signal and identify potential nodes for segregation of gradient-dependent andindependent responses. These results describe how microvascular EC fate decisions can be determined by comparatively moderate changes in VEGF signal strength, resulting in combinatorial changes in the repertoire of immediate-early genes for transcription effectors. Keywords morphogen; microvascular; organogenesis; cell fate During organogenesis, important cell fate decisions are dependent upon positional information provided by graded distribution of morphogens. The impact of morphogens during development is well characterized in Drosophila and Xenopus (reviews Ashe and Briscoe, 2006;Gurdon and Bourillot, 2001). In these systems, morphogens are critical for the formation of sharp borders of distinct cell types from common progenitors during tissue and organ development. It is proposed that localized expression of vascular endothelial growth factor A (VEGF-A) provides positional information that determines endothelial cell patterning during

EngineeringDe NovoAssembly of Fetal Pulmonary Organoids

“…25,[52][53][54][55][56][57] The central role of VEGF-A among these signals has been demonstrated in numerous experimental contexts. 21,23,33,34,[58][59][60] In line with findings from embryological studies, endothelial network morphogenesis in our in vitro constructs is critically dependent on VEGF-A, as evidenced by near-complete ablation of network formation with 2 mg/mL of sVEGFR1-Fc (Fig. 2D).…”

Vascular Endothelial Growth Factor Stimulates Endothelial Colony Forming Cells Proliferation and Tubulogenesis by Inducing Oscillations in Intracellular Ca2+ Concentration

“…[25,26], these findings indicate that InsP 3 -dependent Ca 2þ release occurs less frequently at high [VEGF] in ECFCs, likely due to a decrease in InsP 3 production during the Ca 2þ burst. This feature is supported by a recent study of PLC-c phosphorylation by VEGFR-2, according to which signal duration is longer in HMVECs exposed to lower ligand concentrations [51].…”

“…Such variability in the Ca 2þ response to extracellular hormones or growth factors has already been reported in a number of ECs both in vitro [29,38,49] and in situ [50]. Moreover, the differential activation of jagged1 and DII4 in the Notch signaling pathway and of mitogen activated protein kinases has already been described in ECs exposed to the same VEGF concentration [51,52]. The dissimilar response of ECs from the same coverslip to VEGF might be due to the wide variation in VEGFR-2 levels, as only approximately 60% of ECFCs express it [20].…”

Canonical Transient Receptor Potential 3 Channel Triggers Vascular Endothelial Growth Factor-Induced Intracellular Ca2+Oscillations in Endothelial Progenitor Cells Isolated from Umbilical Cord Blood

“…For instance, the differential activation of jagged1 and DII4 in the Notch signaling pathway determines the distinct fate (tip vs. stalk) of two adjacent endothelial cells exposed to a VEGF gradient during the angiogenic process [85]. A recent study has further demonstrated that the mitogen-activated protein kinase pathway is triggered by VEGF in individual microvascular endothelial cells, whereas their adjoining cells are silent [86]. The dissimilar response of neighboring cells to VEGF might be linked to the wide variation in VEGFR-2 levels, as only about 60% of UCB-ECFCs express it (unpublished data from our group).…”