Inverse relationship between apoptosis and Bcl-2 expression in syncytiotrophoblast and fibrin-type fibrinoid in early gestation

The purpose of this study was to assess the role of apoptosis and cell cycle arrest in the trophoblast during early gestation by determining the location of apoptotic cells and examining the expression of Bcl-2 and p21. Using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) method on human chorionic villi, a cluster of apoptotic nuclei was demonstrated in perivillous fibrin-type fibrinoid, but no apoptotic changes were identified in the syncytiotrophoblast or in other subtypes of the trophoblast. The syncytiotrophoblast was diffusely positive for Bcl-2, but fibrin-type fibrinoid was negative for Bcl-2. Hence, there was an inverse relationship between apoptosis and Bcl-2 expression in both fibrin-type fibrinoid and syncytiotrophoblast. Expression of p21 was present to some extent in the syncytiotrophoblast, but not in fibrin-type fibrinoid. These results suggest that Bcl-2 may play an important role in preventing apoptosis in the syncytiotrophoblast; this may be necessary to prevent any DNA degradation from being spread to other nuclei in a multinuclear cell like the syncytiotrophoblast.