Ontogeny of Clara cell-specific protein and its mRNA: Their association with neuroepithelial bodies in human fetal lung and in bronchopulmonary dysplasia

Clara cell-specific 10-KD protein (CCSP) is an abundant product of nonciliated bronchiolar epithelial (Clara) ails in the lung, We have determined the temporal-spatial distribution of CCSP and its mRNA in developing human lung and in neonatal lung disease, using immunohistochemistry and in situ hybridization. CCSP immunoreactivity was found in nonciliated bronchiolar epithelial ails from 12 weeks of gestation onward. Tracheal and bronchial epithelia showed positive immunoreactivity at each gestational week after 15 weeks and 14 creeks, respectively. CCSP mRNA was seen in the bronchial and bronchiolar epithelia from 16 weeks on; ward and was detected in the trachea from 19 through 23 weeks of gestation. CCSP immunoreactivity and mRNA were present in nonciliated single cells of bronchial and bronchiolar epithelia in fetuses and in infants with and without lung disease. CCSP and CCSP mRNA-containing epithelial cells also formed clusters around neuroepithelial bodies (NEBs), especially at airway branch points, suggesting that NEBs and Clara cells might interact during development and during pulmonary regeneration. Femme of evidence of overlapping of some but not all cells expressing CCSP, SF-A, and pro-SP-B during lung development, a common cell lineage is proposed, with subsequent divergence of phenotypes.