Proliferation and Apoptosis in the Human Adrenal Cortex during the Fetal and Perinatal Periods: Implications for Growth and Remodeling1

After 10–15 weeks of gestation, the human fetal adrenal cortex undergoes rapid growth due to enlargement of a specialized cortical compartment known as the fetal zone (FZ). Soon after birth, the FZ regresses and the adult zonation pattern develops at least in part from cells derived from the persistent definitive zone (DZ), a thin layer of tightly packed cells surrounding the FZ. We postulated that growth of the fetal adrenal cortex involves zone-specific cellular hyperplasia, whereas the postnatal involution of the FZ is due to apoptosis. Therefore, we investigated the pattern of cellular proliferation and death in the FZ and DZ of the human fetal and postnatal adrenal cortex using immunohistochemical staining for proliferating cell nuclear antigen as a marker of mitosis and in situ detection of DNA fragmentation as a marker of apoptosis. Between 10–14 weeks’ gestation, the mitotic indexes (percentage of proliferating cell nuclear antigen-positive cells) in the DZ (26.46 ± 2.95%) and in the FZ (21.26 ± 2...