Studies on rodent endometrial tissue in vitro and in vivo
A system for culturing endometrial cells was developed and used to study the growth curves and morphology of cells from various stages of gestation. The density of cultured cells derived from tissue explanted on days 4 and 5 of pregnancy showed an exponential increase in culture, while the density of cells from tissue explanted on day 10 remained steady and from day 15 declined exponentially. Cells from days 5 and 10 survived for prolonged periods in culture indicating that decidual tissue is not controlled solely by a 'programmed lifespan'. Cells from days 10 and 15 had a similar morphology, while that of cells from day 5 initially differed, but came to resemble cells from the other days over the course of the culture period, indicating that some differentiation occurred in vitro. The distribution of lipid and carbohydrate in the cells was found to alter both over the culture period and with the stage of gestation. The changes loosely reflected the distribution of the substances in decidual tissue in vivo. The effects of progesterone and oestrogen on the morphology of cells from day 4 of pregnancy were examined by scanning electron microscopy. In physiological concentrations, neither steroid had any discernible effect. Studies by other authors have shown the progestrone withdrawal leads to decidual regression but the in vitro results indicate that this is not due to a direct dependence on progesterone. The morphology of the endometrium and stroma during the first 24 hours following oil instillation into the mouse uterus in vivo were followed by light and electron microscopy: epithelial degeneration and stromal decidualization were observed. When indomethacin (an inhibitor of prostaglandin synthesis) was given before, or at various stages after, oil instillation, the rate of epithelial breakdown was decreased and decidualization was inhibited. The combined actions of indomethacin and oil, however, resulted in considerable stromal cell damage.