Transcriptional profiling of equine endometrium before, during and after capsule disintegration during normal pregnancy and after oxytocin-induced luteostasis in non-pregnant mares

Abstract

The current study used RNA sequencing to determine transcriptional profiles of equine endometrium collected 14, 22, and 28 days after ovulation from pregnant mares. In addition, the transcriptomes of endometrial samples obtained 20 days after ovulation from pregnant mares, and from non-pregnant mares which displayed and failed to display extended luteal function following the administration of oxytocin, were determined and compared in order to delineate genes whose expressions depend on the presence of the conceptus as opposed to elevated progesterone alone. A mere fifty-five transcripts were differentially expressed between samples collected from mares at Day 22 and Day 28 of pregnancy. This likely reflects the longer-term exposure to a relatively constant, progesterone-dominated environment with little change in factors secreted by the conceptus that would affect endometrial gene expression. The complement system was amongst the canonical pathways significantly enriched in transcripts differentially expressed between Day 14 and Day 22/28 of pregnancy. The expression of complement components 7 and 8 was confirmed using in situ hybridization. The expression of SERPING1, an inhibitor of the complement system, was confirmed by immunohistochemistry. In line with the resumed capacity of the endometrium to produce prostaglandin, prostaglandin G/H synthase 1 was expressed at higher levels at Days 22 and 28 than at Day 14 of pregnancy. Our data suggest that this up-regulation is enhanced by the presence of the conceptus; samples obtained from mares at Day 20 of pregnancy had significantly higher levels of prostaglandin G/H synthase 1 transcript than mares with extended luteal function.

Uterine extracellular vesicles as multi-signal messengers during maternal recognition of pregnancy in the mare

“…In contrast, Smits et al (2018) 9 reported P19 protein downregulation in UF samples of pregnant mares compared to cyclic controls on day 13, suggesting that P19 was mostly taken up by the conceptus and not present in the UF. At transcript level, Klein et al (2021) 79 reported also a downregulation of P19 in the endometrium during pregnancy on days 14, 22, and 28. In our parallel studies, we found P19 mRNA with highest expression in GE 12 without differences between P and C and with low expression in the embryo (Rudolf Vegas et al 2021, unpublished data).…”

Embryo-endometrial interaction associated with the location of the embryo during the mobility phase in mares

“…The Ingenuity Pathway Analysis (IPA) software (Qiagen) was employed to identify canonical pathways and upstream regulatory elements 26 . The Z-scores were used to predict the activation state (activation or inhibition) of each upstream regulator.…”

“…Several studies investigated the transcriptomic profile of the endometrium to gain further insight into the molecular events underlying embryo-maternal interactions during early pregnancy in mares 20 – 28 . The differentially expressed genes (DEGs) between pregnant and nonbred mares during early pregnancy were mainly associated with pathways related to the immune system, angiogenesis 21 , cell-to-cell interaction 26 , and prostaglandin regulation 23 . These studies advanced our understanding of the molecular pathway associated with embryo-maternal interaction in mares.…”