Influence of Maternal Nutrient Restriction and Realimentation on Vascularity of Bovine Placentomes
To investigate maternal global nutrient restriction and realimentation impacts on placentome vascularity and mRNA expression for angiogenic and vasoactive factors in cotyledonary (COT) and caruncular (CAR) tissues, multiparous beef cows were randomly assigned to either 100% (CON; n = 18) or 60% NRC requirements for all nutrients (RES; n = 28) on d 30 of gestation. On d 85, tissues were collected, or cows remained on CON or RES diets, or were realimented to CON. On d 140, tissues were collected and all remaining cows were placed on CON diets until d 254 where all remaining cows were slaughtered to collect tissues. At tissue collection, placentomes were separated and portions snap frozen until qPCR analyses for mRNA expression of platelet endothelial cell adhesion molecule-1 (PECAM-1), soluble guanylate cyclase-β, endothelial nitric oxide synthase, vascular endothelial growth factor, fms-like tyrosine kinase, and kinase insert domain containing receptor were performed with all normalized to 18S. Vascularity measurements in CAR and COT were stained for PECAM-1, Rhodamine labeled lectin, and DAPI, and micrographs analyzed with Image-Pro Premiere. Treatment did not affect (P ≥ 0.06) mRNA expression in any tissue on any day. Data from d 85 was presented previously where COT capillary size was smaller in RES vs. CON (465 vs. 764 ± 91 µm2). Treatment did not affect any CAR or COT measurements d 140 or 254. In CON cows, CAR tissue area decreased (P = 0.02) and capillary number density increased (P < 0.01) from d 85 to 254 (0.76 vs. 0.59 ± 0.05 mm2; 114 vs. 301 ± 26 number/µm2). In COT, tissue area increased (P = 0.02) from d 85 to 254 (2.66 vs. 2.84 ± 0.05 mm2). Capillary area and surface densities were similar (P ≥ 0.19) on d 85 and 140 and increased (P ≤ 0.04) by d 254. Capillary size decreased (P < 0.01) from d 85 to 140 and were similar (P = 0.14) from d 140 to 254. Capillary number density increased (P < 0.03) throughout gestation (45.6, 66.6, vs. 162.6 ± 6.5 number/µm2). Capillary changes throughout gestation are more prevalent in COT vs. CAR. While we have previously reported that realimentation can augment uterine blood flow and placental arteriole vasoreactivity, the histologic and mRNA expression for angiogenic/vasoactive factors do not appear to be altered by maternal dietary intake. Supported partly by AFRI Competitive Grant no. 2009-65203-05812 from the USDA-NIFA.
Keywords: cow, placenta, vascularity