Apoptosis occurs in implantation site of the rhesus monkey during early stage of pregnancy

The exact role of apoptosis that occurs in human placenta during the early stage of pregnancy remains unknown because of the difficulty in obtaining t he intact implantation site. In this study, we used rhesus monkey as an ani mal model to examine apoptosis occurring in the implantation site at variou s stages of early pregnancy. It was shown that Fas and FasL mRNA and protei n were localized in both the chorionic villi and glandular epithelium from day 15 to day 30 of pregnancy. Fas and FasL protein were also expressed in the epithelial plaque on day 15 of pregnancy. In situ 3'-end-labeling resul ts showed that glandular epithelial cells underwent extensive apoptosis wit h obvious morphological degradation during the early stage of pregnancy. It was found that the cells that were 3'-end-labeled in the chorionic villi a nd anchoring villi were mainly localized in cytotrophoblast and cytotrophob last column. It is therefore suggested that in primates apoptosis, which ma y be involved in the regulation of proliferation of trophoblast villi and d egradation of epithelial plaque, as well as remodeling of the glands in the maternal decidua, may play an important role during the early stage of imp lantation and placentation. (C) 2001 Elsevier Science Inc. All rights reser ved.