Bcl-2 expression and apoptosis in human trophoblast

Summary The function of Bcl-2 in the differentiation and proliferation of human trophoblast cells is not yet elucidated. The expression of Bcl-2 in human placenta was examined immunohistochemically using a monoclonal antibody to Bcl-2 and apoptosis of trophoblast cells was investigated by the 3′-end labeling method to detect fragmented DNA. Bcl-2 protein was localized in syncytiotrophoblast and its amount seemed to increase as pregnancy advanced. The proliferation of trophoblast cells decreased by term, and apoptotic cell death was found less frequently in the placenta at term. This suggests that the higher expression of Bcl-2 protein in late pregnancy may prolong the life of trophoblast cells so that the placental mass is maintained although proliferative activity of trophoblast cells has decreased. Combined with our previous result that there is an inverse relation between p53 protein expression and Bcl-2 protein expression, apoptotic death of trophoblast cells may be under the control of p53 and Bcl-2 proteins.