The distribution and frequency of pulmonary neuroendocrine cells in Down syndrome fetal lungs

The pulmonary neuroendocrine cells (PNEC) are located in the epithelial lining of the airways and consist of solitary neuroendocrine cells (NEC) and NEC clusters, the neuroepithelial bodies (NEB). During fetal life, PNEC are the first to differentiate within the primitive airway epithelium, and bombesin expression favors branching of the respiratory tree. We investigated PNEC in Down syndrome (DS), where the lungs often show enlarged and reduced number of alveoli. Immunohistochemistry for bombesin and synaptophysin, PNEC markers, was evaluated in fetal lungs from 15 cases of DS and 11 age-matched controls from the 17th to 23rd week of gestation. Morphometric analysis assessed PNEC in the mucosal lining of each lung, expressed as number/mm. Nonparametric Mann-Whitney U test showed no statistical difference in frequency of PNEC in DS and controls. Our findings suggest that, at least in late second trimester, the distribution and frequency of PNEC in DS fetuses is not altered.