Nutritional Restriction Prior to Conception in the Sow Alters Embryonic Development and Candidate Gene Expression in the Placenta and Endometrium.

Abstract

The extent to which maternal nutrition alters placental and fetal development through epigenetic mechanisms, is still uncertain. In an established experimental model using the catabolic primiparous sow, feed restriction during lactation affects embryonic survival and development during the subsequent gestation. In a continuation of these studies, primiparous sows (n=34) were either fully fed (Control:C) or restricted to 60% of voluntary feed intake (Restrict:R) during the third week of a 21-d lactation and re-bred after weaning. Sows were euthanized at d 30 of gestation and reproductive and litter characteristics were recorded. Embryos and placentae (n=488 of each) were collected for each sow, and a sample of endometrium (n=68) was taken from the left and right horn from each sow, frozen immediately in liquid nitrogen and stored at -80°C. Total RNA was extracted from placental, endometrial and embryonic samples collected, DNAse-treated, reverse transcribed, and real-time PCR was used to determine transcript abundance of candidate genes involved in regulating endometrial and placental vascularity and embryonic muscle development. The relative deltaCt values were calculated using cyclophilin as an internal control, and data were analyzed using mixed models analysis with treatment and sex of embryo as independent variables and sow as a random variable. There were no differences in ovulation rate, embryonic survival or number of embryos in utero between C and R sows. However, litter sex ratio was different with more males in the R sows (P<0.05) and embryo weight was reduced (P<0.05) in R compared to C sows. Embryo weight and litter sex ratio were also related to sow weight loss in the previous lactation. When genes regulating vascular development were considered, FGF2 and VEGFA mRNA expression was lower in the endometrium, while ANGPT2 was lower (P<0.05) in the placenta, recovered from R sows. Expression of myogenic regulatory factors analyzed (MYF5, MYF6, MYOG, MYOD1, PAX3, GLI1 and WNT10b) was not different between C and R sows at d 30 of gestation. In addition, the expression of some imprinted genes were examined, and IGF2 expression tended to be higher (P=0.059) and INSR expression was higher (P=0.049) in the R embryos, and IGF2R demonstrated a tendency for a sex by treatment interaction (P=0.066) in the placenta. These results confirm that maternal metabolic state prior to conception can adversely affect embryonic size and sex ratio in the next litter. These effects involved expression of genes related to vascular development in the uterus and placenta, and were consistent with the concept of epigenetic regulation of developmentally important genes. (platform)