hybridization for leptin and leptin receptor in the inter-placental uterus and utero-placental compartments during pregnancy. Localization of leptin (Lep) and leptin receptor (LepR) mRNA by in situ hybridization in inter-placental sections (Ut) at post-implantation (A, B), and in the utero-placental compartments (Ut/Pl) at prepartum luteolysis (C, D). (A) Lep mRNA expression is evident in the surface epithelium (solid arrows) and superficial glandular epithelium (open arrows) with weak sub-epithelial stromal signals (solid arrowheads). Deep uterine glands and the myometrium also stain positively for Lep (inset upper right). A negative control is shown in the lower left inset. (B) LepR mRNA is expressed in the luminal epithelium (solid arrows) and superficial glandular epithelial cells (open arrows). Note the prominent stromal signals (solid arrowheads) close to the lumen. The upper right inset is positive staining for LepR in the deep uterine glands and myometrium, and the lower left inset shows a negative control. (C) Intense Lep expression is noted in the fetal trophoblast cells (open arrowheads) of the placental labyrinth at prepartum luteolysis, in contrast to weak staining in maternal decidual cells (solid arrowheads) and sporadic signals in blood vessel endothelium (thin arrows); the upper right inset shows positive reaction in the myometrium, and the lower left inset is the negative control sense probe for Lep. (D) LepR mRNA expression is strong in the placental labyrinth at prepartum luteolysis within fetal trophoblast cells (open arrowheads), while decidual cells have less intense signals (solid arrowheads) and endothelial cells (thin arrows) stain occasionally; the upper right inset shows LepR mRNA in the myometrium, and the lower left inset presents the negative control sense probe for LepR. DG: Deep uterine glands, MY: Myometrium, MV: maternal vessel.