Histological evaluation of H&E-stained sections in the labyrinth zone of murine Cdkn2a-/- (n=5 placentas), Cdkn2a-/-;p53-/- (n=5), p53-/- (n=4), and Cdkn1a-/- (n=3) placentas on day E14.5, compared to WT placentas (n=6). (A−E) The labyrinth zone of the WT (A) differs from those of Cdkn2a-/- (B) and Cdkn2a-/-;p53-/- (C) placentas. Black arrows indicate regular-sized nuclei in the WT placenta and polyploidy in the Cdkn2a-/- and Cdkn2a-/-;p53-/- placentas. Blue arrows indicate normal vasculature in the WT placenta and collapsed vasculature in the Cdkn2a-/- and Cdkn2a-/-;p53-/- placentas. Labyrinths of p53-/- (D) and Cdkn1a-/- (E) placentas did not differ from that of the WT placenta. L, labyrinth. Staining for each placenta was performed in triplicates. 