Endometrial luminal epithelial cells sense embryo elongation in the roe deer independent of interferon-tau†

Abstract

Numerous intrauterine changes take place across species during embryo development. Following fertilization in July/August, the European roe deer (Capreolus capreolus) embryo undergoes diapause until embryonic elongation in December/January. Embryonic elongation prior to implantation is a common feature among ungulates. Unlike many other ruminants, the roe deer embryo does not secrete interferon-tau (IFNτ). This provides the unique opportunity to unravel IFNτ-independent signaling pathways associated with maternal recognition of pregnancy (MRP). This study aimed at identifying the cell-type–specific endometrial gene expression changes associated with the MRP at the time of embryo elongation that are independent of IFNτ in roe deer. The messenger RNA (mRNA) expression of genes known to be involved in embryo–maternal communication in cattle, pig, sheep, and mice was analyzed in laser capture microdissected (LMD) endometrial luminal, glandular epithelial, as well as stromal cells. The mRNA transcript abundances of the estrogen (ESR1), progesterone receptor (PGR), and IFNτ-stimulated genes were lower in the luminal epithelium in the presence of an elongated embryo compared to diapause. Retinol Binding Protein-4 (RBP4), a key factor involved in placentation, was more abundant in the luminal epithelium in the presence of an elongated embryo. The progesterone receptor localization was visualized by immunohistochemistry, showing an absence in the luminal epithelium and an overall lower abundance with time and thus prolonged progesterone exposure. Our data show a developmental stage-specific mRNA expression pattern in the luminal epithelium, indicating that these cells sense the presence of an elongated embryo in an IFNτ-independent manner.

Embryonic diapause in the European roe deer (Capreolus capreolus)

“…The BrdU incorporation in trophoblast cells as measure for cell proliferation increased from 5 % in October/November to 10 % in November/December [29], and there was a 22.5-fold higher protein incorporation at elongation versus diapause [23,24]. By numerous field sample collections, our group substantiated earlier reports [1-3, 25, 28, 29] of a continuous increase in embryonic size with time (Figure 1) (Unpublished data; Rüegg et al 2019 Trophectoderm and Embryoblast of the European Roe Deer (Capreolus capreolus) both proliferate at slow pace during Embryonic Diapause) [4][5][6]. In.…”

“…With developmental progression, there was a decrease in electron-dense droplets and elongation was characterized by the presence of cell organelles, suggesting a higher proliferation rate and increased metabolic demands [28]. While the embryos were not found to secrete interferon tau (IFNT) prior to implantation [6,22], the embryos secreted roe deer-specific pregnancy associated glycoproteins (PAGs) upon implantation [26]. An interspecies embryo transfer experiment with mice, a species with facultative diapause, and sheep, a species without diapause, showed that the mouse uterine environment induced diapause in sheep embryos [15].…”

“…Within the last decades of the 20 th century, a number of studies have emphasized on characterizing the hormonal environment, embryonic and endometrial morphological changes, and the uterine microenvironment to identify the mechanisms that control embryonic diapause in roe deer [3]. Only recently, a new attempt to unravel embryonic diapause in the roe deer was initiated using a novel multi-omics approach that includes a molecular perspective (own unpublished data) [4][5][6].…”

Embryonic diapause in mammals and dormancy in embryonic stem cells with the European roe deer as experimental model

“…Maternal factors involved in governing the cell cycle may be elucidated. They may further our understanding of molecular factors in the uterine microenvironment that play a role in stem cell pluripotency (Drews et al 2019;van der Weijden et al 2019avan der Weijden et al , 2019bvan der Weijden et al , 2019c. The findings may be translatable to other species, including bovine and human.…”

Progestogen Profiling Over the Course of Diapause and Resumption of Embryo Development in the European Roe Deer

“…Thus, the lack of change of the progestogens in roe deer indicates that they are likely not involved reactivation of embryo development. We have previously shown the loss of uterine PR with prolonged P4 exposure [25]. As the progestogens are present in significant amounts, they might play a role in priming the uterus like in mice.…”