Deletion of fetoplacental Fshr inhibits fetal vessel angiogenesis in the mouse placenta

Abstract

It has been shown in both human and mouse placentas that follicle stimulating hormone receptor (FSHR) is expressed in fetal vascular endothelium. There are conflicting reports, however, on the role of FSH to stimulate angiogenesis in vitro in cultured endothelial cells from umbilical veins. Therefore, in this study we undertook an in vivo approach utilizing Fshr null mice to definitively address this question. In the context where all pregnant dams have identical Fshr genotypes, we generated fetuses and associated fetal portions of placenta that were Fshr wt or Fshr null and analyzed angiogenesis within the placental labyrinths. Quantitative morphometric analyses of placentas obtained at mid-gestation revealed that the percentage of the placenta composed of labyrinth is significantly decreased in Fshr null placentas relative to wt placentas. Furthermore, data presented demonstrate that within the Fshr null labyrinths, fetal vessel angiogenesis was significantly reduced relative to wt labyrinths. The results obtained with this combination of in vivo and genetic approaches conclusively demonstrate that signaling through endothelial FSHR does indeed stimulate angiogenesis and that placental Fshr is essential for normal angiogenesis of the fetal placental vasculature.

Keywords: Angiogenesis; FSH receptor; Follicle stimulating hormone; Placenta.

Figure 1. Quantification of labyrinth size in placentas of wild-type (Fshr^+/+) and null (Fshr^-/-) fetuses, expressed as a percentage of the area of the entire placenta

Data shown are mean ± SEM of quantifications of 3 Fshr^+/+ and 6 Fshr^-/- placentas. Asterisk denotes statistically significant difference, P<0.05.

Figure 2. Fetal and maternal sinuses in the labyrinth of placentas of wild-type (Fshr^+/+) and null (Fshr^-/-) fetuses

Tracings of sinuses in the placental labyrinth are shown, with fetal and maternal sinuses identified based on the presence of nucleated and non-nucleated blood cells, respectively. Blue pseudo-coloring indicates fetal sinuses, and red indicates maternal sinuses. Top: Images shown are placentas of fetuses 3 and 5 of Fig 1 and they are representative of 3 Fshr^+/+ and 6 Fshr^-/- 15 dpc placentas. Each image was tiled at 200× magnification. Bottom: Enlargement of the portion of each labyrinth that is highlighted by a green box in the image above.

Figure 3. Quantification of angiogenesis in the placental labyrinth of wild-type (Fshr^+/+) and null (Fshr^-/-) fetuses

The A number and B size of fetal sinuses, and the C number and D size of maternal sinuses in Fshr^+/+ and Fshr^-/- labyrinths of 15 dpc placentas, with number of sinuses normalized to overall labyrinth size. Data shown are the mean ± SEM of sinus quantifications of 3 Fshr^+/+ and 6 Fshr^-/- placentas. Asterisks denote statistically significant differences, P<0.05.