Angiogenic activity in embryonic chick lung

Normal and pathological formation of blood vessels is of considerable interest both in terms of basic scientific processes and clinical applications. The presence of Flk-1 mRNA positive cells has been detected in the embryonic lung in previous studies. Flk-1 mRNA codes for vascular endothelial growth factor (VEGF) receptors. Bioassays offer advantages over molecular localisation techniques in that the presence of active processed forms of the molecules can be revealed, rather than nonprocessed forms, or nontranslated messages. In this study it is shown that developing chick lung tissue from 9 d and 10 d old embryos produces an angiogenic activity when incubated on chick chorioallantoic membrane (CAM). Significant angiogenic activity is not detected when 7 d and 8 d old embryonic lung tissue is assessed by the same bioassay. When angiogenic activity induced by lung grafts taken from distal regions of the 10 d old lung is compared with angiogenic activity induced by lung grafts taken from proximal regions of the10 d old lung, no significant difference is found. The evidence suggests that embryonic chick lung is producing a functional angiogenic endothelial cell growth factor (thought to be VEGF) from at least as early as its 9th day of development.