VEGF AND BFGF STIMULATE MYOCARDIAL VASCULARIZATION IN EMBRYONIC CHICK

We tested the hypothesis that early vascularization of the embryonic h eart is enhanced after bolus injections of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) into the vite lline vein before the onset of myocardial vasculogenesis (3.5 days, st age 21). Electron and light microscopy were utilized to obtain morphom etric data. At stages 29 and 31, myocardial vessel volume or numerical density were higher in embryos injected with 50 ng bFGF than in the s aline-injected controls. A VEGF injection increased vascular volume de nsity at stage 29 and both volume and numerical density at stage 31. b FGF, but not VEGF, was associated with an enhancement of the sinusoida l system (spongy layer of the ventricle) at stage 29. This effect disa ppeared by stage 31. in conclusion, 1) enhancement of bFGF or VEGF bef ore myocardial vascularization increases vascular growth, but the init ial effect of bFGF is greater; 2) the effects of these growth factors on vascular volume and numerical density are temporally dependent; and 3) bFGF, in addition to its effects on the coronary vasculature, infl uences ventricular modeling by apparently acting on myocytes as well a s endothelial cells.