(245) Sexual Dimorphism in Porcine Pre-Implantation Embryos

Sexual Dimorphism in Porcine Pre-Implantation Embryos

Morgan S. Clemens ¹ and Claire Stenhouse ¹

1. Department of Animal Science, The Pennsylvania State University, University Park, United States

Abstract Text:

Sexual dimorphism in utero-placental function has been suggested in several mammalian species. Male piglets have higher morbidity and mortality compared to their female littermates, despite being larger in size from early in gestation. Recently, we demonstrated sex differences in placental and endometrial angiogenesis, apoptosis, proliferation, and extracellular matrix composition from as early as day 30 of gestation that may contribute to the differences in morbidity and mortality observed postnatally. This study aimed to determine whether sexual dimorphism exists in the secretion of estradiol and interleukin-1β (IL1B) by day 11 porcine embryos. These two molecules have essential roles in the establishment and maintenance of pregnancy. We hypothesize that there are differences in conceptus-uterine signaling between male and female embryos during early gestation which may be linked to the sexual dimorphism in endometrial and placental function observed later in gestation. Gilts (n=3) were euthanized and hysterectomized on day 11 of gestation. Embryos were flushed from the uterus using phosphate buffered saline. Embryos were individually cultured in 24 well plates for 24 hours in 750 μL of RPMI-1640 medium containing 5% charcoal-stripped fetal bovine serum and 1% antibiotic antimycotic solution at 38.5°C with 5% CO₂. Following the 24-hour culture period, each embryo was snap frozen in liquid nitrogen and stored at -80^oC until DNA and RNA were extracted. Culture media was frozen and stored at -80^oC. Polymerase chain reaction for SRY (Sex Determining Region Y) was utilized to determine embryonic sex. The concentration of estradiol and IL1B in the media was quantified by ELISA. A total of 42 embryos from three gilts were cultured. Embryo size varied by gilt, with large, spherical embryos in litter 1 (n=25), medium sized, spherical embryos in litter 2 (n=11), and small, spherical embryos in litter 3 (n=6). Estradiol and IL1B secretion were impacted by litter (P< 0.0001) with the largest embryos secreting the greatest amount of estradiol and the smallest embryos secreting the least. Due to limitations in the sex distribution of the embryos in litters two and three it was not possible to perform sex comparisons. Within litter one, embryonic sex affected estradiol secretion (P< 0.05), with male embryos secreting greater amounts of estradiol than female embryos. There was no effect of embryonic sex on interleukin-1β secretion. These data demonstrate that the production of estradiol and IL1B increase exponentially as the embryo increases in size. Interestingly, female embryos secreted less estradiol which may suggest sexual dimorphism in conceptus-uterine interactions during the pre-implantation that warrants further investigation. It is hoped that this, in conjunction with ongoing assessment of sex differences in 1) the expression of candidate mRNAs in the embryos with roles in embryo development and pregnancy establishment and 2) metabolomic profiles of the media, will enhance the understanding of sexual dimorphism in pre-attachment conceptus-uterine interactions. We acknowledge the contributions of the Penn State Swine Barn and the undergraduate and graduate students that contributed to this study. This study was funded by USDA NIFA Multistate/Regional Research Appropriations (Project PEN04775 and Accession number 7001112), and USDA NIFA Hatch Appropriations (Project PEN04995 and Accession number 7007748).