BELANGER, C.A.*; DZIALOWSKI, E.M.; University of North Texas, Denton: Morphological Changes of the Avian Ductus Arteriosi During Hatching

The ductus arteriosi (DA) are two blood vessels connecting the pulmonary arteries to the aorta in the developing avian embryo. These vessels allow for the shunting of deoxygenated blood away from the lungs and to the chorioallantoic membrane (CAM) for gas exchange. Following hatching, the DA closes and the tissue is remodeled, bringing about the separation of the systemic and pulmonary circulations. Here we present the histomorphological changes that occur in the chicken DA during prepipping, internal pipping, external pipping, and hatching. The avian DA consists of two morphologically distinct tissue types, the proximal and distal portions. Histological examination shows developmental differences between the proximal and distal portions of the DA with regard to lumen occlusion, as well as differences in endothelial cell, smooth muscle and elastin thickness. Tissue remodeling and endothelial cell proliferation begins to occur as early as internal pipping, with the lumen almost completely occluded by the 3rd day of post-hatching life. Expression of vascular endothelial growth factor (VEGF), a hypoxia-induced molecule that plays a key role in endothelial cell proliferation and migration during the closure of the mammalian DA, increases in avian endothelial cells during the hatching process. Since relatively little is known about avian DA closure, we provide a histomorphological timeline of changes in the DA as the chicken develops from embryo to hatchling and we characterize the expression of VEGF in avian DA closure. This study was funded by NSF operating grant IOB0417205.