Transcriptome of early embryonic invasion at implantation sites in a murine model

Metabolic reprogramming and heterogeneity during the decidualization process of endometrial stromal cells

The human endometrial decidualization is a transformative event in the pregnant uterus that involves the differentiation of stromal cells into decidual cells. While crucial to the establishment of a successful pregnancy, the metabolic characteristics of decidual cells in vivo remain largely unexplored. Here, we integrated the single-cell RNA sequencing (scRNA-seq) datasets on the endometrium of the menstrual cycle and the maternal-fetal interface in the first trimester to comprehensively decrypt the metabolic characteristics of stromal fibroblast cells. Our results revealed that the differentiation of stromal cells into decidual cells is accompanied by increased amino acid and sphingolipid metabolism. Furthermore, metabolic heterogeneity exists in decidual cells with differentiation maturity disparities. Decidual cells with high metabolism exhibit higher cellular activity and show a strong propensity for signaling. In addition, significant metabolic reprogramming in amino acids and lipids also occurs during the transition from non-pregnancy to pregnancy in the uteri of pigs, cattle, and mice. Our analysis provides comprehensive insights into the dynamic landscape of stromal fibroblast cell metabolism, contributing to our understanding of the metabolism at the molecular dynamics underlying the decidualization process in the human endometrium.

IGF2BP2 regulates the proliferation and migration of endometrial stromal cells through the PI3K/AKT/mTOR signaling pathway in Hu sheep

Insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2), a significant member of the conserved RNA-binding protein family, plays various roles in numerous physiological and pathological processes. However, the specific function of IGF2BP2 in regulating endometrial function in sheep remains largely unknown. In this study, we observed a significant upregulation in IGF2BP2 mRNA abundance in the endometrium during the luteal phase compared to the follicular phase in Hu sheep. The knockdown of IGF2BP2 resulted in accelerated cell proliferation and migration of Hu sheep endometrial stromal cells (ESCs). Moreover, RNA sequencing analysis revealed that genes with significantly altered expression in IGF2BP2 knockdown cells were predominantly enriched in endometrial receptivity-related signaling pathways, such as cytokine-cytokine receptor interaction, NOD-like receptor, PI3K-AKT, and JAK-STAT signaling pathway. Additionally, the knockdown of IGF2BP2 significantly increased the expression of matrix metalloprotein 9 (MMP9), vascular endothelial growth factor, and prolactin (PRL) in ESCs. The knockdown of IGF2BP2 was also observed to stimulate the PI3K/AKT/mTOR pathway by upregulating integrin β4 (ITGB4) expression. Notably, the downregulation of ITGB4 attenuates IGF2BP2 knockdown-induced facilitation of proliferation and migration of Hu sheep ESCs by inhibiting the PI3K/AKT/mTOR pathway. Collectively, these findings highlight the important role of IGF2BP2 in regulating endometrial function, particularly through the modulation of ESC proliferation and migration via the PI3K/AKT/mTOR pathway.

The endometrial transcriptome transition preceding receptivity to embryo implantation in mice

BACKGROUND

Receptivity of the uterus is essential for embryo implantation and progression of mammalian pregnancy. Acquisition of receptivity involves major molecular and cellular changes in the endometrial lining of the uterus from a non-receptive state at ovulation, to a receptive state several days later. The precise molecular mechanisms underlying this transition and their upstream regulators remain to be fully characterized. Here, we aimed to generate a comprehensive profile of the endometrial transcriptome in the peri-ovulatory and peri-implantation states, to define the genes and gene pathways that are different between these states, and to identify new candidate upstream regulators of this transition, in the mouse.

RESULTS

High throughput RNA-sequencing was utilized to identify genes and pathways expressed in the endometrium of female C57Bl/6 mice at estrus and on day 3.5 post-coitum (pc) after mating with BALB/c males (n = 3-4 biological replicates). Compared to the endometrium at estrus, 388 genes were considered differentially expressed in the endometrium on day 3.5 post-coitum. The transcriptional changes indicated substantial modulation of uterine immune and vascular systems during the pre-implantation phase, with the functional terms Angiogenesis, Chemotaxis, and Lymphangiogenesis predominating. Ingenuity Pathway Analysis software predicted the activation of several upstream regulators previously shown to be involved in the transition to receptivity including various cytokines, ovarian steroid hormones, prostaglandin E2, and vascular endothelial growth factor A. Our analysis also revealed four candidate upstream regulators that have not previously been implicated in the acquisition of uterine receptivity, with growth differentiation factor 2, lysine acetyltransferase 6 A, and N-6 adenine-specific DNA methyltransferase 1 predicted to be activated, and peptidylprolyl isomerase F predicted to be inhibited.

CONCLUSIONS

This study confirms that the transcriptome of a receptive uterus is vastly different to the non-receptive uterus and identifies several genes, regulatory pathways, and upstream drivers not previously associated with implantation. The findings will inform further research to investigate the molecular mechanisms of uterine receptivity.

Impact of endometrial claudin-3 deletion on murine implantation, decidualization and embryo development

The composition of cell contacts in the endometrium plays an important role in the process of embryo implantation and the establishment of pregnancy. In previous studies, we showed an induction of the tight junction protein claudin-3 in the developing decidua from 6.5 dpc onwards. To evaluate the role if this specific claudin-3 distribution, we here evaluated the effect of an endometrial claudin-3 deletion in implantation and embryo development in claudin-3 knockout mice. Claudin-3 KO mice were fertile but revealed a slightly reduced amount of implantation sites as well as of litter size. Though implantation sites showed morphologically regularly developed embryos and deciduas, depth of ectoplacental cone invasion was reduced in tendency compared to controls. The weight of the implantation sites on 6.5 and 8.5 dpc as well as the weight of the embryos on 17.5 dpc, but not of the placentas, was significantly reduced in claudin-3 KO mice due to a maternal effect. This could be due to an impairment of decidualization as substantiated by a downregulation of the transcription of various decidua-associated genes in the early implantation sites of claudin-3 KO mice. The fact that claudin-3 KO mice are nevertheless fertile possibly may be compensated by the presence of other claudins like claudin-4 and claudin-10.

Comparative transcriptome analysis of embryo invasion in the mink uterus

INTRODUCTION

In mink, as many as 65% of embryos die during gestation. The causes and the mechanisms of embryonic mortality remain unclear. The purpose of our study was to examine global gene expression changes during embryo invasion in mink, and thereby to identify potential signaling pathways involved in implantation failure and early pregnancy loss.

METHODS

Illumina's next-generation sequencing technology (RNA-Seq) was used to analyze the differentially expressed genes (DEGs) in implantation (IMs) and inter-implantation sites (inter-IMs) of uterine tissue.

RESULTS

We identified a total of 606 DEGs, including 420 up- and 186 down-regulated genes in IMs compared to inter-IMs. Gene annotation analysis indicated multiple biological pathways to be significantly enriched for DEGs, including immune response, ECM complex, cytokine activity, chemokine activity and protein binding. The KEGG pathway including cytokine-cytokine receptor interaction, Jak-STAT, TNF and the chemokine signaling pathway were the most enriched. A gene network was constructed, and hub nodes such as CSF3, ICAM1, FOS, IL1B, IL8, CD14 and MYC were found through network analysis.

DISCUSSION

This report provides a valuable resource for understanding the mechanisms of embryo implantation in mink.

Proteomics study reveals that the dysregulation of focal adhesion and ribosome contribute to early pregnancy loss

Purpose

Early pregnancy loss (EPL) affects 50–70% pregnant women in first trimester. The precise molecular mechanisms underlying EPL are far from being fully understood. Therefore, we aim to identify the molecular signaling pathways relating to EPL.

Experimental design

We performed proteomics and bioinformatics analysis of the placental villi in women who have undergone EPL and in normal pregnant women. The proteomics data were validated by Western blot analysis.

Results

We identified a total of 5952 proteins in placental villi, of which 588 proteins were differentially expressed in the EPL women. Bioinformatics analysis revealed that these differentially expressed proteins participated in a variety of signaling pathways, including the focal adhesion pathway and ribosome pathway. Moreover, results of the Western blot confirmed that Desmin, Lamin A/C, MMP‐9, and histone H4 were upregulated in EPL and the Lamin C/ Lamin A ratio decreased obviously in EPL. These proteins could be associated with the pathophysiology of EPL. The data have been deposited to the ProteomeXchange with identifier PXD002391.

Conclusion and clinical relevance

Our study demonstrated that the focal adhesion pathway and ribosome pathway are involved in EPL, and these findings might contribute to unveil the pathophysiology of EPL.

Genome-Wide Association Mapping for Female Infertility in Inbred Mice

The genetic factors underlying female infertility in humans are only partially understood. Here, we performed a genome-wide association study of female infertility in 25 inbred mouse strains by using publicly available SNP data. As a result, a total of four SNPs were identified after chromosome-wise multiple test correction. The first SNP rs29972765 is located in a gene desert on chromosome 18, about 72 kb upstream of Skor2 (SKI family transcriptional corepressor 2). The second SNP rs30415957 resides in the intron of Plce1 (phospholipase C epsilon 1). The remaining two SNPs (rs30768258 and rs31216810) are close to each other on chromosome 19, in the vicinity of Sorbs1 (sorbin and SH3 domain containing 1). Using quantitative RT-PCR, we found that Sorbs1 is highly expressed in the mouse uterus during embryo implantation. Knockdown of Sorbs1 by siRNA attenuates the induction of differentiation marker gene Prl8a2 (decidual prolactin-related protein) in an in vitro model of decidualization using mouse endometrial stromal cells, suggesting that Sorbs1 may be a potential candidate gene for female infertility in mice. Our results may represent an opportunity to further understand female infertility in humans.