Myocardial vascularization is stimulated by basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) in embryonic chick heart

The roles of bFGF and VEGF in coronary vascularization during embryonic fetal development have not been determined. We tested the hypothesis that early vascularization of the embryonic heart is enhanced by these growth factors by administering them in ovo prior to the onset of myocardial vasculogenesis (3.5 days, stage 21) as a single bolus (50 ng) into the vitelline vein. Another group was injected with PBS buffer (sham). Morphometric methods with electron and light microscopic analyses were employed to obtain quantitative data. Vascular volume percent of the compact region of the left ventricle (mean ± SE) was significantly higher in bFGF (12.9 ± 0.9, p < 0.001) and VEGF (12.6 ± 2.0, p < 0.01) than in shams (5.5 ± 0.4). Similar results were obtained when bFGF was suffused onto the surface of the heart for 24 hours (5 ng/hr). bFGF, but not VEGF increased the depth of the sinusoids (which occur between trabeculae) in the spongy layer of the ventricle and thereby decreased the diffusion distance (μm) between the endocardium and epi-myocardial border: bFGF = 24.0 ± 0.8; sham = 30.8 ± 0.8 (mean ± SE). We conclude that 1) both bFGF and VEGF stimulate neovascularization in the embryonic heart and 2) bFGF also influences the modeling of the sinusoidal system. Both of these effects serve to shorten O₂ distances.