Hosting the preimplantation embryo: potentials and limitations of different approaches for analysing embryo - endometrium interactions in cattle

Abstract

Ongoing detailed investigations into embryo-maternal communication before implantation reveal that during early embryonic development a plethora of events are taking place. During the sexual cycle, remodelling and differentiation processes in the endometrium are controlled by ovarian hormones, mainly progesterone, to provide a suitable environment for establishment of pregnancy. In addition, embryonic signalling molecules initiate further sequences of events; of these molecules, prostaglandins are discussed herein as specifically important. Inadequate receptivity may impede preimplantation development and implantation, leading to embryonic losses. Because there are multiple factors affecting fertility, receptivity is difficult to comprehend. This review addresses different models and methods that are currently used and discusses their respective potentials and limitations in distinguishing key messages out of molecular twitter. Transcriptome, proteome and metabolome analyses generate comprehensive information and provide starting points for hypotheses, which need to be substantiated using further confirmatory methods. Appropriate in vivo and in vitro models are needed to disentangle the effects of participating factors in the embryo-maternal dialogue and to help distinguish associations from causalities. One interesting model is the study of somatic cell nuclear transfer embryos in normal recipient heifers. A multidisciplinary approach is needed to properly assess the importance of the uterine milieu for embryonic development and to use the large number of new findings to solve long-standing issues regarding fertility.

Differences in progesterone concentrations and mRNA expressions of progesterone receptors in bovine endometrial tissue between the uterine horns ipsilateral and contralateral to the corpus luteum

“…P4 action provides an intrauterine environment that is suitable for pregnancy succession in cattle [ 29 ]. In cattle, P4 receptor expression was recognized as an important regulatory factor for pregnancy establishment [ 3 ].…”

A mathematical model of the interaction between bovine blastocyst developmental stage and progesterone-stimulated uterine factors on differential embryonic development observed on Day 15 of gestation

“…However, the embryo also contributes to the complexity of events that occur during preimplantation and this ultimately affects pregnancy outcome (Ulbrich et al, 2012). Approximately 5% of embryos die because of gross chromosomal abnormalities that prevent development (Peters, 1996), and oocyte developmental competence varies depending on which category of follicular environment they have been derived from (Pavlok et al, 1992;Lonergan et al, 1994).…”

Basic and practical aspects of pregnancy establishment in cattle

“…Oestrup et al, 2011;Alminana et al, 2012;Forde et al, 2012a;SalilewWondim et al, 2012;Ulbrich et al, 2013;Fazelli and Holt, 2016;Klein, 2016). This cross-talking reflects quality at several points with some species differences, but the overall pattern is the same.…”