X-Linked Inhibitor of Apoptosis Protein Expression and the Regulation of Apoptosis During Human Placental Development1

In this study, we have examined the expression and poten-tial role of X-linked inhibitor of apoptosis protein (XIAP), Fas, and Fas ligand (FasL) in the regulation of apoptosis throughout placental development. Protein expression was determined by Western blot analysis and immunohistochemistry, whereas ap-optotic cell death was assessed by DNA fragmentation analysis and TUNEL. The XIAP was present in trophoblast throughout placental development, but its content significantly decreased during late pregnancy, when apoptosis was maximal. The FasL content was low during early placental development but in-creased coincidentally to the decrease in XIAP during the third trimester. Our data also suggest that placental apoptosis is the culmination of the relative expression of these cell-death and-survival proteins, a phenomenon that is cell type-specific and dependent on cytodifferentiation and the stage of placental de-velopment. Moreover, the induction of syncytiotrophoblast ap-optosis may involve the concomitant up-regulation of FasL for Fas activation and the removal of downstream inhibition of the apoptotic cascade by XIAP. apoptosis, developmental biology, placenta, pregnancy, tropho-blas