Localization and expression of prostaglandin E₂ receptors in human placenta and corresponding fetal membranes with labor

Objective: The effects of prostaglandin E₂ (PGE₂) are mediated through G-protein coupled receptors, acting via different second messengers. The aim of this study was to characterize the temporal and tissue specific localization and expression of the PGE₂ receptor subtypes (EP1-4) in uteroplacental tissues during human pregnancy. Study design: Placenta and fetal membranes were collected after delivery at preterm or term, each with or without labor. The localization and expression of the PGE₂ receptor subtypes were determined by immunohistochemistry and Western blot. Results: All 4 receptors were expressed in the placenta and fetal membranes; only EP3 was present in the syncytiotrophoblast layer. EP1 to EP4 were consistently expressed across gestation in the fetal membranes; however, a different cellular localization with labor was observed in the amnion for EP1, EP2, and EP4. Conclusion: The presence of these receptors in the placenta and fetal membranes may indicate autocrine roles for PGE₂ in the signaling pathways associated with placental function and parturition.