Vascular endothelial growth factor: a regulator of vascular morphogenesis in the Japanese quail embryo

Experiments in mouse embryos indicate that a critical level of VEGF is required for normal vascular development, as mice lacking a single VEGF allele die at midgestation. Thus VEGF concentration may be a determinant of the size and location of major blood vessels during formation of the primary capillary plexus. Ectopic VEGF delivery was used to examine the effect of VEGF concentration on early vascular patterning in the quail embryo. VEGF was delivered by implanting VEGF-soaked heparin chromatography beads at three rostral-caudal locations in embryos with six somite pairs, which allowed us to study the effect of VEGF on different cellular activities. Ectopic VEGF resulted in significant changes in the vascular pattern at three rostral-caudal levels. Quantitation demonstrated an increased vascularity in the area of the implanted VEGF bead compared to the vascular pattern of embryos with control beads. Areas lateral to the dorsal aortae that are normally avascular became vascularized, and there was an apparent fusion between the dorsal aorta and lateral capillary plexus.