Association of the cardiac neural crest with development of the coronary arteries in the chick embryo

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Abstract
Background: Chick coronary arteries orginate as penetrating channels from a subepithelial peritruncal ring into the wall of all three aortic coronary sinuses. Two of these capillaries develop a muscular wall and become the definitive coronary arteries. Since cardiac neural crest (CNC) contributes ectomesenchyme to the tunica media (TM) of the aortic arch vessels, we wished to learn if the CNC also contributes to the media of the coronary arteries and if CNC plays an inductive role in determining the site of aortic penetrations and influences which channels persist to hatching. Methods: Quail-to-chick chimeras were made by bilaterally removing the chick CNC and replacing it with quail CNC. The chimeras and unoperated controls were collected on embryonic days (ED) 7–18, fixed in Carnoy's fixative, serially sectioned, stained with Feulgen-Rossenbeck stain, and analyzed. Several ED 18 controls and chimeras were also stained with Gomori's trichrome stain, or labeled with antineurofilament or antivascular smooth muscle alpha actin. Results: The TM of the coronary arteries and the aortic coronary sinuses did not consist of CNC cells. The media of the surviving coronary arteries was disrupted by clusters of CNC cells scattered in the wall of the base of the coronary artery on ED 14 and 18. Persisting coronary arteries were always associated with large neural crest-derived parasympathetic ganglia near their origin. Branches from parasympathetic nerves entered the base of the coronary arteries where the clusters of neural crest cells were located. Quail cells were also associated with tiny vessels exiting the ostia of the coronary arteries and traveling in the outer aortic wall. Labeling with antibodies confirmed a disruption of the TM at the base of the coronary arteries, and showed innervated clusters of quail cells in the disrupted part of the TM. Conclusion: Although the TM of the coronary arteries and the aortic coronary sinuses contained no CNC cells, clusters of innervated quail cells disrupted the TM at the base of the coronary arteries. CNC does not appear to induce capillary penetration direclty; however, the exclusive association of CNC-derived parasympathetic ganglia and nerves with persisting coronary arteries suggests that the presence of parasympathetic ganglia is essential to the survival of the definitive coronary arteries. CNC cells may also be associated with the development of the aortic vasa vasorum.