Fig. 3. Analysis of placental expression of CAR and of overall placenta organization of CAR-deficient embryos. (A) Paraffin sections of wild type (+/+) and CAR-deficient (–/–) placentae (E11.5) were stained with antibodies against the endothelial marker endomucin and counterstained with hematoxylin. Since maternal vessels are devoid of endothelial cells the endothelial staining shows selectively only blood vessels of the fetus. The different zones of the placenta are marked: gl, giant layer; s, spongiotrophoblast layer; l, labyrinthine layer; cp, chorionic plate. Note: the extension of the labyrinthine layer was not altered in CAR^-/- embryos. Bar, 100 µm. (B) Cryostate section of a placenta of E11.5 wild-type embryo double stained with anti-CAR polyclonal antibodies (red) and an anti-PECAM-1 mAb (green) visualized by indirect immunofluorescence. Nuclei were visualized with Systox (blue). CAR was found on trophoblast cells of the labyrinth zone, but not on endothelial cells. Bar, 20 µm.