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Dihydrotestosterone stimulates branching morphogenesis, cell proliferation, and programmed cell death in mouse
B M Levesque1, R J Vosatka, H C Nielsen
1Division of Newborn Medicine, Floating Hospital for Children at New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Abstract:
Early gestation lung development is characterized by branching morphogenesis of the airways and basic lung structure formation. Androgens delay late-gestation lung development if the androgen exposure begins in early gestation. We hypothesized that there would be effects of early gestation androgens on lung development. Embryonic mouse lungs (d 11.5) were cultured with dihydrotestosterone (DHT), DHT plus flutamide, or with nothing as controls. Branching morphogenesis was significantly increased after 24, 48, and 72 h of culture. This effect was blocked by simultaneous flutamide treatment. Fetal sex did not influence the DHT response. DHT increased cell proliferation as measured by [3H]thymidine incorporation into DNA. Autoradiography showed prominent [3H]thymidine labeling of epithelia and mesenchyme in regions of new bud formation. DHT treatment significantly increased the thymidine-labeling index of fibroblasts and airway epithelial cells. Programmed cell death, which is found in developing organs in association with cell proliferation during structure formation and tissue remodeling, was studied using terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay. In control lungs, programmed cell death occurred in the peripheral mesenchyme surrounding newly forming buds and underlying airway branch points. DHT treatment increased programmed cell death in association with increased branching morphogenesis. Evaluation of near-adjacent sections (control and DHT-treated lungs) showed that apoptotic mesenchymal cells were flanked by [3H]thymidine-labeled fibroblasts and epithelial cells, suggesting a coordination of these processes in the progression of branching morphogenesis. We conclude that androgen enhances the process of early lung morphogenesis by increasing cell proliferation and programmed cell death and by promoting the structural progression of branching morphogenesis.