Embryonic regulation of endometrial epithelial apoptosis during human implantation

Apoptosis is a mechanism of cell death in which cells undergo a genetically determined programme. The implanting blastocyst has to appose and adhere t o the endometrial epithelium and subsequently invade it. Locally regulated uterine epithelial apoptosis induced by the embryo is a crucial step in epi thelial invasion in rodents. To address the physiological relevance of this process in humans, we have investigated the effect of single human blastoc ysts on the regulation of apoptosis in cultured human endometrial epithelia l cells (EEC) in the apposition and adhesion phases of implantation, We rep ort a co-ordinated embryonic regulation of EEC apoptosis, In the apposition phase, the presence of a blastocyst rescues EEC from the apoptotic pathway . However, when the blastocyst adheres to the EEC monolayer it induces a pa racrine apoptotic reaction.