PDGFRa Expression in the IPY
Sectioned and sliced specimens of 14.5- or 15.5-dpc placental discs were immunostained with anti-PDGFRa monoclonal antibody, APA5. As shown in Figure 1, С and D, and Figure 2, К and L, strong APA5 staining was observed in the epithelial cells lining sinusoidal structures that extend to the chorioallantoic placenta and communicate with the yolk sac cavity through pits on the surface of the chorioallantoic disc. Moreover, the APA5-positive epithelium was found to be composed of two distinct types, columnar and squamous, the basement membranes of which faced the fetal blood vessels and maternal blood sinuses, respectively (Fig. 1, С and D). From these morphological features, this APA5-positive epithelium was proven to be the IPY. Since ISH using antisense probe for mouse PDGFRa mRNA also detected signals from these cells (Fig. 1, E and F), while sense primer did not (data not shown), we concluded that both types of epithelial cells of the IPY expressed PDGFRa.
In addition to the IPY, APA5 signals were detected in the junctional zone and decidual layer (Fig. 2, К and L). buy asthma inhalers
FIG. 1. Intraplacental yolk sac or sinus of Duval in 15.5-dpc murine placentas. A, B) Hemotoxylin and eosin (HE) staining of sectioned specimens of placenta. В is a magnified view of the IPY/sinus of Duval of A. Note that the sinus of Duval (*) is lined by columnar and squamous epithelium, and the basement membrane faces fetal blood vessels (f) and maternal blood sinuses (m), respectively. C, D) Immuno-staining of PDGFRct with APA5. E, F) ISH detecting mRNA of PDGFRa. C-F demonstrated that both the columnar and squamous epithelium of the IPY express PDGFRa. G, H) ISH with the probe of our cloned putative cDNA of calbindin-D9k. Strong signals were detected in the columnar epithelium of the IPY and weak signals in visceral endoderm. D, F, and H are differential interference contrast (DIC) images. Scale bar, 100 ц,т (А, С, E, G), 20 ц.т (В, D, F, H). vy, visceral yolk sac; py, parietal yolk sac; f, fetal blood vessels; m, maternal blood sinuses.
FIG. 2. Development of the IPY was traced by APAS-immunostaining of sliced specimens. Cross images of placentas at 8.5 (A), 9.5 (C), 10.5 (E), 11.5 (C), 12.5 (I), 14.5 (K), 16.5 (M), and 18.5 dpc (O) are shown in the left column, and magnified views of the junctional region of visceral and parietal yolk sac of each placenta are shown in the right column. After 8.5 dpc, visceral endoderm ceased to express PDGFRa, while parietal endoderm continued to do so. From 9.5 to 10.5 dpc, APA5-strongly positive endoderm located at the border of visceral and parietal endoderm made pits on the fetal surface of chorioallantoic placenta, and after 11.5 dpc these cells started to invaginate, expanding into the border of the chorion and labyrinthine layer.