ATP binding cassette transporter A1 (ABCA1) is a membrane transporter which performs cellular efflux of cholesterol and phospholipid. ABCA1's cholesterol transporting role in human placenta appears to be crucial for normal fetal development. Despite the critical importance of cholesterol in fetal development, expression of ABCA1 in the human placenta throughout gestation and its specific cellular localization have not been known yet. We therefore investigated ABCA1 expression in human placenta at first trimester and term by western blot and quantitative real-time PCR (qRT-PCR) analysis. Furthermore, its localization was investigated by immunohistochemistry and confocal microscopy. Expression of ABCA1 did not differ significantly between first trimester and term placenta at both protein and mRNA levels. Immunohistochemical data demonstrated that ABCA1 was widely localized in the villous and extra- villous cytotrophoblast as well as in some stromal and endothelial cells. Confocal microscopy imaging data showed that ABCA1 was localized largely at the basolateral and to some extent at the apical side of first trimester villous cytotrophoblast cell membranes. Placental expression of ABCA1 throughout the gestation and its specific cellular localization indicate that this transporter may play an important role in materno-fetal cholesterol transfer.
