Endometrial and luteal gene expression of putative gene regulators of the equine maternal recognition of pregnancy

Our understanding of the temporal changes in endometrial and luteal gene transcripts related to the actions of oxytocin and prostaglandin during early equine pregnancy is incomplete. Addi-tionally, the role of oxytocinase, also known as Leucyl-cystinyl aminopeptidase (LNPEP), during early pregnancy in mares has not been previously investigated. Luteal and endometrial biopsies were obtained on Day (D)8, D10, D12 and D15 post-ovulation in pregnant (PREG) and diestrus (DIEST) mares for real-time qPCR. Differences in endometrial gene expression occurred over time in: SLC2A4, SLC2A1, PTGES, OXTR and LNPEP. PTGFR and PLA2G2C had lower relative abun-dance in PREG D15 endometrium compared to D10. OXT and OXTR were increased on D10 and 15 PREG, respectively. Regarding luteal mRNA relative abundance, ESR1, PTGS2, PTGFR, and PTGES had higher relative abundance in D12 of DIEST and PREG. Luteal expression of OXTR and OXT had higher relative abundance in D15 compared to D8, and LNPEP had higher relative abundance in D10 and 12. Endometrial and luteal PTGES had an increased mRNA abundance in both D12 DIEST and PREG mares, which may lead to additional luteoprotective prostaglandin E2 (PGE2) secretion. Furthermore, luteal SLC2A1 had higher relative abundance in pregnancy, and likely supports the high metabolic activity of luteal tissue by increasing glucose uptake. Oxy-tocinase is present in endometrial and luteal tissue and its role in oxytocin induced prostaglandin secretion is uncertain.

Automated summary

Our understanding of the temporal changes in gene transcripts related to oxytocin and prostaglandin actions during early equine pregnancy is incomplete. This study investigates the gene expression differences in endometrium and luteal tissue, as well as the potential role of oxytocinase, during early pregnancy in mares.