Background: The family of mammalian aquaporins (AQP) consists of 12 known members, each with a specific tissue distribution and membrane localization pattern. AQP4 is the first member of this family identified in biological membranes. This water channel protein is primarily expressed in astrocytes but is also localized in ependymocytes and endothelial cells, suggesting its involvement in the movement of water between the blood and brain, and between the brain and cerebrospinal fluid (CSF). To date, the regulation of AQP4 expression in the human placenta has not been studied. The purpose of this work was to investigate AQP4 localization and expression in the human placenta during gestation.
Materials and methods: A total of 30 samples, 15 full-term placentae and 15 chorionic villous samples from first trimester, for the immunohistochemical analysis of AQP4 expression were used. The gestation period ranged from 5 to 40 weeks.
Results: A decrease of AQP4 expression in the syncytiotiophoblast from the first to the third trimester of gestation, in contrast with an increased expression shown by endothelial cells and stroma of placental villi was found.
Conclusion: Our results may suggest that AQP4-mediated maternal-fetal fluid exchange could play an important role in the control of ion homeostasis and water balance in the human placenta throughout pregnancy.