Human Placental Trophoblast Cells Express α-Tocopherol Transfer Protein

α-Tocopherol transfer protein (α-TTP), a 30 kDa cytosolic protein first described to be present in the liver and important for α-tocopherol trafficking, plays a major role in maintaining α-tocopherol levels in plasma, while α-tocopherol is known as the major lipid-soluble antioxidant. Expression of α-TTP has not only been described in animal model liver, but also in diverse other tissues such as rat brain or pregnant mouse uterus, the latter finding stressing the importance of α-TTP for embryogenesis and foetal development. In this study, we report the identification of α-TTP in human liver by anti-human α-TTP monoclonal antibodies made in rat and the cellular localization of α-TTP in term human placenta. By immunohistochemistry, intense staining of α-TTP was seen in syncytiotrophoblast as well as in villous and invading extravillous cytotrophoblast, while basal decidual cells showed slighter, but present staining of α-TTP. Foetal vessel endothelium remained unstained. It is therefore suggested that α-TTP may play a major role in supplying α-tocopherol to the foetus prior to delivery and is likely involved in maintaining adequate α-tocopherol levels in the foetus.