Trophoblast Cell Proliferation and Apoptosis in Placental Development During Early Gestation Period in Rats.

OBJECTIVE To show apoptotic and mitotic activities in differentiation and proliferation of the trophoblast through the techniques of immunohistochemistry and terminal deoxynucleotidyl transferase-mediated deoxy-uridine triphosphate-biotin nick end labeling (TUNEL), apart from achieving a morphological examination of placental development during early gestation in rats. STUDY DESIGN Animals were sacrificed on days 7, 9, 11, and 13 of pregnancy. The samples removed from those rats were processed for purposes of microscopic analysis. The decidual structure resulting from the differentiation of the endometrial stromal cells in the uterus on days 7, 9, and 11 of pregnancy was determined. RESULTS It was observed that the placenta, with an increasing trophoblast proliferation and differentiation, matures on day 13 of pregnancy, after which time the growth seems to be continuous. Density of PCNA-positive cells and PCNA immunostaining was observed to decrease in parallel with the age of pregnancy. The excessive number of apoptotic cells seen in the early periods of pregnancy decreased as the placenta matured. CONCLUSION We speculate that the rat placenta grows to maturity by day 13 of pregnancy along with increased proliferation and apoptosis in the early days of pregnancy. In addition, a significant decrease of proliferation and apoptosis was observed in the placenta with increasing age of the pregnancy.