Conceptus-Maternal Interactions in Parthenogenetic Cattle Pregnancies

Abstract

Molecular mechanisms governing conceptus elongation and placentation remain relatively elusive, but previous studies suggest the paternal genome has a vital role in placental development. Osteopontin (OPN), an extracellular matrix adhesion molecule, was previously postulated to have promotive effects on elongation and attachment during early pregnancy in ovine and porcine. Parthenogenetic embryos (PAR; lacking paternal genetic contribution) were previously created and transferred. PAR conceptuses appeared to elongate and showed primitive attachment profiles compared to conventional (CON) pregnancies. PAR pregnancies showed decreased pregnancy-associated glycoprotein (PAG) profiles in maternal circulation, suggesting increased likelihood of pregnancy failure. Low maternally circulating PAG pregnancies have previously shown increased prostaglandin E2 (PGE2) circulating concentrations. The objectives of this study were to compare transcriptomic profiles and localize resulting molecules of interest in PAR (n=3) and CON (n=3) pregnancies during the placental attachment period for further insight into conceptus attachment/pregnancy maintenance. Trophectoderm (TE), endometrium (EM), and corpora lutea (CL) sampling was performed for gestational day (GD) 31 PAR and CON bovine pregnancies. The resulting transcriptomes were compared and analyzed with FDR≤0.05 considered statistically significant. OPN was increased in the PAR pregnancies’ EM (FDR from both groups. This study revealed a potential shift in the prostaglandin biosynthesis pathway towards increased active PGE2 production in PAR pregnancies. In bovine pregnancies, we propose carbonyl reductase 1 (CBR1) may be important for placentation given it was observed localized in trophoblast giant cells (TGC) and at attachment regions in GD31 CON pregnancies, but this was not observed in PAR tissues which failed to successfully attach. No significant elevation in PAG levels were observed in maternal circulation for PAR pregnancies. Moreover, PAR TGC were observed at comparable levels to CON (P>0.05) but were limited to the apical boarder of the uterine LE. The sire genome’s role in embryogenesis remains remarkably unknown, but these data suggest a vital paternal role in mediating conceptus growth, advanced placental development, and successful fetal-maternal attachment in bovine.