Cardiac morphogenesis--recent research advances.

It has been demonstrated recently that a specific region of neural crest contributes cells to the septa of the outflow tract of the heart. Removal of this region of cardiac neural crest prior to migration from the neural fold results in persistent truncus arteriosus in chick embryos. Removal of other regions of cranial neural crest results in double outlet right ventricle. Since double outlet right ventricle is produced by manipulation of noncardiac neural crest, this malformation is thought to be an indirect rather than direct effect of neural crest ablation. The cranial neural crest forms the walls of all of the aortic arch arteries and it is proposed herein that flow abnormalities are produced in the pharyngeal region by injury to the neural crest. These abnormal hemodynamic characteristics influence heart development. Cardiac neural crest seeds the heart with parasympathetic postganglionic neurons as well as ectomesenchyme. Removal of the cardiac neural crest results in cardiac malformations because of the decreased ectomesenchymal cells. However, the neural population undergoes regeneration and so the innervation of malformed hearts is morphologically normal. The mechanism for this regeneration is not understood.