Periconceptional Nutrient Restriction in the Ewe Alters MAPK/ERK1/2 and PI3K/Akt Growth Signaling Pathways and Vascularity in the Placentome

This study evaluated the role of MAPK/ERK1/2 and/or PI3K/Akt signaling pathways in modulating ovine placentomal vascularity in response to periconceptional maternal nutrient restriction. Ewes were randomly assigned to be nutrient restricted (NR, 50% NRC recommendation, N = 7) or control fed (CF, 100% NRC recommendation, N = 7) from 60 ± 2 days before to 30 days after conception (day 0). From day 31 of gestation, all ewes (CF and NR) were fed the control diet until necropsy on day 78. On day 78 of gestation, NR ewes exhibited greater vascularity in both caruncular (CAR) and cotyledon (COT) tissues than CF ewes. Akt or ERK1/2 content in CAR and COT arterial tissue did not differ across dietary treatment. The activated forms, phosphorylated Akt and phosphorylated ERK1/2, were significantly increased in COT but not CAR arterial tissues of NR ewes compared to those of CF ewes (P < 0.05). For both CF and NR ewes, phosphorylated Akt and phosphorylated ERK1/2 content in COT are higher (P < 0.05) than those in CAR arterial tissues. Immunohistochemical staining revealed cytoplasmic and nuclear localization of Akt, phosphorylated Akt, ERK1/2 and phosphorylated ERK1/2, with phosphorylated Akt and phosphorylated-ERK1/2 specifically localized in trophoblast cells, while binucleate cells remained unstained. In placentomal blood vessels, Akt, phosphorylated Akt, ERK1/2 and phosphorylated ERK1/2 were localized to both endothelium and smooth muscle cells. These findings demonstrate for the first time that periconceptional NR increases vascular density in both COT than CAR tissues of the ovine placentome, and that the MAPK/ERK1/2 and/or PI3K/Akt signaling pathways are increased in NR COT but not NR CAR arterial tissues.