X-linked inhibitor of apoptosis protein expression and the regulation of apoptosis during human placental development

In this study, we have examined the expression and potential role of X-link ed inhibitor of apoptosis protein (XIAP), Pas, and Fas ligand (FasL) in the regulation of apoptosis throughout placental development. Protein expressi on was determined by Western blot analysis and immunohistochemistry, wherea s apoptotic 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 bu t increased coincidentally to the decrease in XIAP during the third trimest er. Our data also suggest that placental apoptosis is the culmination of th e relative expression of these cell-death and -survival proteins, a phenome non that is cell type-specific and dependent on cytodifferentiation and the stage of placental development. Moreover, the induction of syncytiotrophob last apoptosis may involve the concomitant up-regulation of FasL for Pas ac tivation and the removal of downstream inhibition of the apoptotic cascade by XIAP.