Figure 4.

Expansion of spongiotrophoblast in Ipl-null placentas. (A) Midline placental sections (hematoxylin/eosin) from the Ipl^loxP line at 16.5 dpc. There is a global increase in placental size with deletion of Ipl, but the spongiotrophoblast (sp) is expanded disproportionately. la, labyrinthine trophoblast. (B) Ratios of the area of spongiotrophoblast to labyrinth (Spong/Lab) in midline sections of placentas from heterozygous crosses (16.5 dpc). Data from single crosses are shown. In data from four heterozygous crosses with the Ipl^loxP line, combined after normalization to the mean value for each cross, the ratio was 1.22 ± 0.20 and 0.78 ± 0.13 for the Ipl-null (Neg) and Ipl-positive (Pos) placentas, respectively (n = 34). (C) High-power fields of Ipl-positive and Ipl-negative placentas. The panels on the left are from the Ipl^neo line at 12.5 dpc (PAS). Lines indicate the giant cell layer (gc) adjacent to maternal decidua (ma). The panels on the right are at 16.5 dpc (hematoxylin/eosin) centered on the spongiotrophoblast. There is expansion of this layer with an increase of glycogen-containing cells (arrow).