CARDIAC NEURAL CREST CELLS PROVIDE NEW INSIGHT INTO SEPTATION OF THE CARDIAC OUTFLOW TRACT - AORTIC SAC TO VENTRICULAR SEPTAL CLOSURE

A great deal is unclear about the process of cardiac outflow septation . Much controversy exists regarding the precise details of tissue orig ins and movements of various components. The contribution of the cardi ac neural crest to aorticopulmonary and distal truncal septation has b een described; however, the distribution of the neural crest in the pr oximal outflow and heart is unknown. The present study describes the m ovement of cardiac neural crest cells from the caudal pharyngeal arche s into the outflow tract and base of the heart during the period of ou tflow septation. Using quail-chick chimeras we found that the cardiac neural crest was distributed to all levels of the outflow tract and in to the base of the heart. Septation of the outflow tract lumen occurre d by two different processes that involved the cardiac neural crest di rectly. Cardiac neural crest cells were also distributed to regions of the outflow tract that correlated with sites of remodeling, such as t he aortic sac as it was remodeled into the base of the ascending aorta and pulmonary trunk, the distal truncus that was patterned into the t wo semilunar valves and in the proximal conotruncus where muscularizat ion of the ridges and septum occurred. Additionally, cardiac neural cr est cells were found at the site of closure of the ventricular septum, in the wall of the pulmonary infundibulum, and transiently in the wal l of the aortic vestibule. Contrary to current thinking, not all of th e condensed mesenchyme in the outflow tract during septation was deriv ed from neural crest. (C) 1998 Academic Press.