Aspects of embryo-maternal communication in establishment of pregnancy in cattle

Abstract

Establishment of pregnancy in mammals requires reciprocal molecular communication between the conceptus and endometrium that modifies the endometrial transcriptome and uterine luminal milieu to support pregnancy. Due to the small size of the early embryo and elongating conceptus relative to the volume of the uterine lumen, collection of endometrium adjacent to the developing conceptus is difficult following conventional uterine flushing methods in cattle. Use of endometrial explants in culture can overcome this challenge and reveal information about the dialogue between the developing embryo and the uterus. The aim of this short review is to summarize some of our recent findings in relation to embryo maternal interaction during bovine pregnancy establishment and to put them in the wider context of fertility in cattle.

Embryonic maternal interaction in cattle and its relationship with fertility

“…A total of 348 genes were differentially expressed (221 genes upregulated and 127 downregulated in long compared to short conceptuses) suggesting inherent differences exist between such conceptuses and not just differences in the ability of the conceptus to produce IFNT. This is consistent with our own recent data which have identified conceptus‐induced transcriptomic changes in the bovine endometrium which are IFNT‐dependent and independent (Mathew et al., ; Sánchez et al., ). The underlying factors that regulate conceptus‐maternal crosstalk between advanced (long) or retarded (short) conceptuses and the endometrium are unknown.…”

“…However, the underlying factors that regulate conceptus‐maternal crosstalk and how these differ between “good” and “poor” quality conceptuses and endometria are unknown. Numerous studies from our group have reported a wide variation in length amongst conceptuses recovered on the same day, even from the same uterine environment (Clemente et al., ; O'Hara et al., ; Sánchez et al., ). Such variation in trophoblast length amongst age‐matched conceptuses is likely to reflect differences in developmental competence, although this has yet to be formally tested by retransferring such conceptuses to examine pregnancy rates.…”

“…Following on from the study of Barnwell et al. (), we have recently demonstrated, using an ex vivo endometrial explant model, that the endometrial transcriptome is differentially affected by short and long conceptuses (Sánchez et al., ; Figure ). Such conceptuses were individually placed on endometrial explants alongside explants cultured with media alone (Control) or media containing 100 ng/ml IFNT.…”

“…Only six of 108 conceptus‐induced differentially expressed genes were shared between small and large conceptuses. Interestingly, 101 transcripts were exclusively regulated by large conceptuses; of these, PCSK1 , TNNI3K , MPV17L and IL17 were the most upregulated and TEPP , CACNA1L , AQP1 and HIP1 were the most downregulated (Sánchez et al., ; Figure ). These and similar data may allow a better understanding of the underlying molecular pathways involved in embryo survival and maternal recognition of pregnancy in cattle.…”

“…Use of an ex vivo uterine endometrial explant–conceptus coculture system to elucidate conceptus‐induced effects on the endometrium both dependent and independent of interferon‐tau ( IFNT ; Mathew et al., ; Sánchez et al., ). Uterine explants taken from the same uterus were exposed to (a) medium alone (Control), (b) 100 ng/ml recombinant ovine IFNT , (c) a long Day 15 conceptus, or (d) a short Day 15 conceptus.…”