αvß3 Integrin and fibronectin expressions and their relation to estrogen and progesterone during placentation in swine.

Mammalian pregnancy requires specific interactions between the conceptus and its mother that involve the endocrine system and adhesion molecules. The relation between adhesion molecules and their ligands at the fetal-maternal interface is crucial for developing a successful implantation. Progesterone (P4) and estrogen (E2) secreted by the porcine conceptus are required for the relation to be established. We investigated the expression of αvß3 integrin and its ligand, fibronectin (FN), at the placental interface, and E2 and P4 concentrations in both serum and maternal and fetal placental extracts during placentation in swine. Placental and serum samples of crossbred sows at 17, 30, 60, 70, and 114 days gestation and no pregnant uteri were used. The presence of αvß3 and FN were determined by immunohistochemistry, and E2 and P4 by chemiluminescence in homogenates of nonpregnant uterus (HoU), swine maternal placenta (HoPM), swine fetal placenta (HoPF) and serum. The expression of αvß3 and FN increased at the interface at 17, 30 and 60 days gestation. Immunostaining decreased by 70 days. Serum E2 levels peaked at 17 days, then decreased, then increased again near term. The highest concentration of P4 occurred in HoPF at 70 days gestation, then decreased coincident with a decline in integrin and FN expression at the placental interface. High P4 levels during swine gestation may regulate the expression of αvß3 integrin and FN at the placental interface for up to 70 days gestation. Other adhesion molecules and their ligands likely maintain the fetal-placental interface after 70 days.