DEVELOPMENT OF PULMONARY NEUROENDOCRINE CELLS OF FETAL HAMSTER IN EXPLANT CULTURE

Fetal hamster lung explant was cultured in serum-free medium on gestat ional Day 11-2 days before the appearance of pulmonary neuroendocrine cells (PNEC)-and the development and differentiation of PNEC from imma ture fetal lung epithelium was examined through immunostaining for neu ral cell adhesion molecule (NCAM) to establish an in vitro system to s tudy the mechanisms involved. PNEC were present in the main bronchus a fter 2 days of culture. Thereafter, NCAM-positive clusters of PNEC inc reased and were distributed from the large bronchus to the terminal br onchiole with a proximal-to-distal wave. To elucidate the role of NCAM in the fetal development of PNEC, whole fetal lung was cultured on ge stational Day 11 with an anti-NCAM antibody. This antibody slightly in hibited the growth and branching morphogenesis of the lung and disturb ed the formation of PNEC clusters. NCAM may function to form clusters of PNEC known as neuroepithelial bodies. We cultured fetal lung epithe lial explant at gestational Day 11 after removing mesenchyme, includin g nerve tissue, with dispase digestion. Immunohistochemical staining f or NCAM revealed that PNEC were induced in cultured fetal epithelium w ithout mesenchymal tissue, but basement membrane Matrigel was necessar y to maintain cultured epithelium. In conclusion, PNEC derive from imm ature airway epithelial cells. This organ culture system, therefore, i s a useful experimental model and should facilitate further investigat ions of the development and differentiation of PNEC. Mesenchymal and n eural tissues are not always necessary for the development of PNEC, bu t matrix substance and/or growth factors may be required to induce or maintain PNEC.