Apoptosis in human chorionic villi and decidua in normal and ectopic pregnancy

To investigate possible effects of implantation on apoptosis, we examined the cleavage of DNA in human chorionic villi and decidua in intrauterine and ectopic pregnancy. Very limited but detectable cleavage of DNA was recognized in the chorionic villi and decidua in normal pregnancy. A ladder pattern, characteristic of the apoptotic breakdown of DNA, was present in the villi in tubal pregnancy. High molecular weight DNA was predominant in the decidua in tubal pregnancy. Quantitative analysis of low molecular weight fragments of DNA revealed a significant increase in the villous tissue, together with a significant decrease in the decidual tissue, in tubal pregnancy as compared to those in normal pregnancy. An analysis in situ revealed that apoptotic cells were predominant in the syncytiotrophoblast in tubal pregnancy. In decidual tissue, labelled cells were occasionally seen in normal pregnancy, and their numbers decreased in tubal pregnancy. The present study demonstrates that apoptosis occurs in the villi, but not in the decidua in tubal pregnancy, unlike the situation in normal pregnancy. Our results suggest that the implantation site might affect the occurrence of apoptotic changes in early pregnancy of humans.