Over‐expression of hypoxia inducible factor‐1 alpha correlates with major coronary artery anomalies

Previously we showed that the outflow tract myocardium and other regions corresponding to the location of the major coronary vessels of the developing chicken heart, display a high level of hypoxia as assessed by the hypoxia indicator EF5. The EF5 positive tissues were also specifically positive for nuclear‐localized hypoxia inducible factor‐1 alpha (HIF‐1α), the oxygen‐sensitive component of the hypoxia inducible factor‐1 (HIF‐1) heterodimer. In this study we altered ambient oxygen levels (hypoxia 15%; hyperoxia 75–40%) during developmental stages (ED 4.5–9, HH 25–35) critical to avian coronary vessel development in order to alter tissue hypoxia, HIF‐1α protein expression and its downstream targets. We also altered gene expression by injecting an adenovirus containing a constitutively active form of HIF‐1α (AdcaHIF‐1α). We assayed for coronary anomalies using anti‐alpha‐smooth muscle actin immunohistology of sections transverse to the heart and by using 3D reconstruction. When incubated for 4.5 days under abnormal oxygen levels or injected with the AdcaHIF‐1α, coronary arteries displayed deviations from their normal proximal connections to the aorta. These deviations were similar to known clinical anomalies of coronary arteries and were verified using 3D reconstructions. These findings indicate that developing coronary vessels may be subject to a level of regulation that is dependent on differential oxygen tension within cardiac tissues and subsequent HIF‐1 regulation of gene expression.