Development of the conducting airway epithelium in fetal Syrian golden hamsters during normal and diabetic pregnancies

Abstract

The conducting airway epithelium of fetal Syrian golden hamsters was studied from gestational day 12 to day 15, during normal and uncontrolled diabetic pregnancies. Diabetes was induced in the pregnant hamsters by injecting streptozotocin at 60 mg/kg body weight, subcutaneously, early on gestational day 10. Cells in S-phase were labelled immunochemically with bromodeoxyuridine (BrdU), and the day on which endocrine cells and ciliated cells first appeared was determined. In control fetuses, the BrdU-labelling indices (LI's) of different anatomical airway levels were significantly different from one gestational day to the next. For example, the LI of the lobar bronchus was significantly different on each gestational day (P less than .0001), and the same was true of the bronchioles. Moreover, the difference between LI's of the lobar bronchus and bronchioles-terminal buds was highly significant on day 12 (P less than .0001), and on day 13 the differences between lobar bronchus and bronchioles, lobar bronchus and terminal buds, and bronchioles and terminal buds were also highly significant (P less than .0001). However, on gestational days 14 and 15, the LI's were reduced and were comparable at different airway levels. The BrdU-labelling indices were very consistent among fetuses of the same age, and the differences between the average LI's for pups of different litters was numerically very small. Hyperglycemia (mild, moderate, severe) did not alter LI's in the fetal airway epithelial cells. Furthermore, although glycogen was not depleted from the airway epithelium of the hyperglycemic fetuses as it was in the controls, the endocrine cells first appeared on gestational days 12, 13, and 14, respectively, in the trachea, lobar bronchus and bronchioles, followed 1 day later by the ciliated cells, in the fetuses of control and diabetic mothers. In our experimental model, induction of diabetes in the pregnant hamsters on gestational day 10 did not appear to alter development or differentiation of the fetal conducting airway epithelium.