PSIII-A-15 Pregnancy Associated Glycoproteins Effects on Placenta Function, Uterine Remodeling and Attachment of Bovine Conceptuses

Abstract The objective of this study was to evaluate transcriptomic differences in reproductive tissues of beef heifers with high vs. low PAG concentrations carrying viable pregnancies during the attachment and early placentation periods. Bos indicus beef heifers (n=25) were subjected to embryo transfer on day 7 with IVP embryos, and pregnancies were confirmed at slaughter. Heifers were harvested on days 25 (n=8) and 36 (n=8), and samples from endometrium (END) and trophectoderm (TE) were collected for RNA isolation using a commercial extraction kit (QIAGEN; Hilden, Germany). Plasma concentrations of PAGs were determined via validated ELISA and the females were classified in groups of high and low PAG (6.8±0.7 (n=4) vs. 0.8±0.7 (n=4) ng/mL on D25 and 15±2.1 (n=5) vs. 4±1.2 (n=3) ng/mL on D36; P< 0.05). An Illumina platform was utilized for RNA sequencing. Differentially expressed genes between groups and by tissue were determined using edge-R package from R. Gene ontology analyses revealed a down regulation of processes associated with embryonic and placenta development on D36 in both TE and END for the low PAG group. On D25 and D36, markers of attachment, ECM remodeling and invasion were significantly upregulated in the TE, but not in the END of the low PAG pregnancies. PAG genes were not differentially expressed between groups. In conclusion, heifers with low PAG in peripheral circulation have significantly different gene expression profiles in the developing conceptus and endometrium. The results suggested abnormal maternal-conceptus interactions initiated on D25, which may have resulted in poor embryonic and placenta development on D36. Disturbances at the maternal-conceptus interface could be impairing PAGs from reaching the maternal peripheral circulation, since no differences in PAG genes were found between PAG groups. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2017-67015-26457 from the USDA National Institute of Food and Agriculture.