Developmental Parallels Between the Human Organs of Zuckerkandl and Adrenal Medulla

The adrenal medulla and organs of Zuckerkandl consist of chromaffin cells that produce, store, and secrete catecholamines. In humans, the adrenal medulla is known to function throughout postnatal life, while the organs of Zuckerkandl degenerate by 2-3 years of postnatal life. Although the history of investigation of chromaffin cells goes back more than a century, little is known about the reciprocal organogenesis of the adrenal glands and organs of Zuckerkandl during human fetal development. In the current study, we compared these two organs using serial sectioning, routine histological staining, and immunohistochemical reactions in human embryos, prefetuses, and fetuses from 8 to 26 gestational weeks. In our study, we used antibodies for tyrosine hydroxylase, dopamine beta-hydroxylase, and phenylethanolamine N-methyltransferase, which are enzymes of catecholamine synthesis, β-III tubulin, and S100. We found two morphological cell types (large and small) in the developing ganglia, organs of Zuckerkandl, and adrenal medulla, and two migration patterns of large cells and small cells. The immunohistochemical characteristics of these cells were determined. We revealed that the number of small cells increased significantly at the ages from 16 to 21-22 gestational weeks, followed by a decrease at 22.5-26 gestational weeks. The presence of two large cell subpopulations was suggested-those that migrate primarily from organs of the Zuckerkandl region and those that differentiate later from the small cells. We also determined that 12 gestational weeks was the age of the first appearance of phenylethanolamine N-methyltransferase reactivity in developing chromaffin cells, temporally correlating with synaptogenesis events. This is important data in the light of the controversial glucocorticoid theory of phenylethanolamine N-methyltransferase induction in humans.