Uterine expression of leukemia inhibitory factor coincides with the onset of blastocyst implantation

Differential expression of bovine milk-derived exosomal miRNAs and their role in modulating endometrial receptivity during early pregnancy

Endometrial receptivity is critical for successful implantation of bovine embryos. MicroRNA (miRNA), as a key regulator of uterine receptivity, is involved in physiological processes such as cell differentiation, proliferation, and apoptosis. The aim of this study was to identify pregnancy-specific miRNAs derived from milk exosomes of non-pregnant and early pregnant cows. In addition, bioinformatics analysis was used to assess the differential expression, target genes, and functions of these miRNAs in order to examine their significance in endometrial cell regulation. Exosomes were isolated from milk using an exosome extraction kit and then identified by Western blotting and transmission electron microscopy. We used Illumina high-throughput sequencing to profile miRNAs and identify differentially expressed miRNAs in bovine milk-derived exosomes at different stages of pregnancy (days 15, 25 and 30) and in non-pregnant cows (day 0). The sequencing data revealed a significant upregulation of bta-miR-125b in pregnant cows at days 15 and 25 compared to non-pregnant cows. Bta-miR-125b targets the Leukemia inhibitory factor (LIF), which is thought to play a critical role in the development of endometrial receptivity by regulating gene expression. KEGG pathway enrichment and Gene Ontology analysis indicated that the target genes of the differential miRNAs were significantly enriched in the key signaling pathways, including the MAPK, phosphatidylinositol signaling system and PI3K-Akt signaling pathways, as well as physiological activities such as RNA polymerase II transcriptional regulation, protein phosphorylation, apoptosis control and cell proliferation regulation. These signaling pathways and physiological activities are all indispensable parts during the process of pregnancy. These findings emphasize bta-miR-125b critical function in regulating endometrial receptivity via important signaling pathways, providing potential indicators for early pregnancy detection and insights into enhancing reproductive efficiency in dairy cows.

Understanding epigenetic regulation in the endometrium - lessons from mouse models with implantation defects

Endometrial function, crucial for successful embryo implantation, is significantly influenced by epigenetic regulation. This review investigates the crucial roles of DNA methylation, histone modifications, chromatin remodeling, and RNA methylation in endometrial receptivity and implantation, based on a survey of recent literature on knockout mouse models with implantation defects. These models illuminate how epigenetic disruptions contribute to implantation failure, a significant human reproductive health concern. DNA methylation and histone modifications modulate endometrial receptivity by affecting gene silencing and chromatin structure, respectively. Chromatin remodeling factors also play a critical role in endometrial dynamics, influencing gene expression. Furthermore, RNA methylation emerges as critical in implantation through transcriptional and translational control. While human studies provide limited epigenetic snapshots, mouse models with suppressed epigenetic regulators reveal direct causal links between epigenetic alterations and implantation failure. Understanding these epigenetic interactions offers potential for novel therapies addressing reproductive disorders.

Progesterone receptor in uterine glands is required for pregnancy establishment in mice

Embryo implantation is a critical event in the establishment of pregnancy, and implantation failure is a major cause of pregnancy loss in women. Coordinated, cell-type specific responses to the ovarian steroid hormones, estrogen, and progesterone, within the endometrium underlie successful embryo implantation and pregnancy establishment. In this study, we utilized a glandular epithelium (GE) specific Cre recombinase mouse line that is only active in the adult (Prss29-Cre) to determine the biological role of progesterone receptor (PGR) in uterine glands during pregnancy. Conditional ablation of PGR specifically in the GE compromised fertility due to defects in uterine receptivity and embryo implantation. Histological and transcriptomic analyses uncovered disruption of multiple PGR-regulated genes in the GE during the window of receptivity, including leukemia inhibitory factor (LIF), a cytokine produced specifically by the GE that is essential for embryo implantation. Interestingly, intraperitoneal injections of recombinant LIF in Pgr conditional knockout mice rescued embryo implantation and supported successful pregnancy to term. These findings underscore the vital role of PGR in regulating Lif expression in the GE, while suggesting that PGR in the glands of the uterus is unessential once pregnancy is established. Overall, these findings reveal a previously unrecognized role of PGR in uterine glands and support the hypothesis that glandular secretions, governed by PGR, are indispensable for pregnancy establishment.

Endometrial scratching before euploid embryo transfer: a case-control study

PURPOSE

To evaluate the effect of endometrial scratching on in vitro fertilization (IVF) success rates in women undergoing frozen embryo transfer with preimplantation genetic testing for aneuploidy (PGT-A).

METHODS

Biopsy was performed at oocyte retrieval in cases and compared to those who did not undergo scratching (controls). Endpoints included pregnancy loss, total pregnancy, clinical pregnancy rate (CPR), ongoing pregnancy rate/live birth rate (OPR), and the incidence of chronic endometritis (CE).

RESULTS

Women in case and control groups had similar characteristics, such as age, body mass index, and parity. Overall total pregnancy rate was 82.43% following single euploid embryo transfer in cases compared to 85.7% in controls (p = 0.57; OR = 1.27; 95% CI = 0.565 to 2.78). CPR was 73.3% and 76.2% (p = 0.62; OR = 1.18; 95% CI = 0.594 to 2.29), and OPR between groups was 64.8% and 72.3% (p = 0.28; OR = 1.42; 95% CI = 0.74 to 2.7). First trimester loss rate was similar at 16.9%% and 15.5%%, respectively (p = 0.82). Subjects who underwent scratching closer to their frozen embryo transfer (≤ 3 months) had a similar overall pregnancy rate to those with a longer delay between retrieval and frozen embryo transfer (> 3 months 81.4% vs.87.5%; p = 0.56). CE incidence was 10.8% (8 out of 74; 95% CI = 5.5% to 19.9%). The odds of having a second trimester loss were significantly higher in the scratch group compared to controls (p = 0.03; OR = infinity; 95% CI = 1.3 to infinity).

CONCLUSIONS

Endometrial scratching before frozen euploid embryo transfer did not influence pregnancy outcome but increased the chances of second trimester loss. CE was a frequent finding in those undergoing endometrial scratching at the time of retrieval.

Spatiotemporal functions of leukemia inhibitory factor in embryo attachment and implantation chamber formation

Embryo implantation is crucial for successful pregnancy, requiring appropriate uterine responses to implantation-competent blastocysts. Molecular communication at the maternal-fetal junction governs this process. Leukemia inhibitory factor (Lif) plays a pivotal role in implantation across species. Lif is abundantly expressed in the glandular epithelium during blastocyst-receptive phase and is induced in the stroma surrounding attached blastocysts. While diminished Lif expression leads to infertility, its influence on peri-implantation uteri remains unclear. Therefore, we investigated the role of Lif in uterine physiology using its uterine-specific knockout (uKO) and uterine epithelial-specific KO (eKO) in mice. Lif eKO and uKO mice displayed infertility owing to failed embryo attachment. Recombinant Lif supplementation rescued the reproductive phenotype of Lif eKO mice, but not Lif uKO mice; however, recombinant Lif injection rescued embryo attachment in Lif uKO mice. RNA-seq analysis indicated that Lif governs uterine epithelial genes, but not embryonic genes, to facilitate embryo attachment via activating nuclear Stat3. Concordantly, three-dimensional imaging of the uterine epithelium revealed that luminal closure and crypt formation are regulated by the uterine Lif-Stat3 axis as well as the presence of blastocysts. Collectively, our findings shed light on previously unknown mechanism on how Lif influences uterine functions molecularly and physiologically during early pregnancy.

Epigenetic alteration of uterine Leukemia Inhibitory Factor gene after glyphosate or a glyphosate-based herbicide exposure in rats

Glyphosate-based herbicides (GBHs) or its active ingredient, glyphosate (Gly), induce implantation failure in rats. We aimed to elucidate a mechanism of action of these compounds assessing the transcriptional and epigenetic status of the receptivity marker, leukemia inhibitory factor (Lif) gene. F0 rats were orally exposed to GBH or Gly at 3.8 or 3.9 mg Gly/kg/day, respectively, from gestational day (GD) 9 until weaning. F1 females were mated and uterine samples collected at GD5. Methylation-sensitive restriction enzymes (MSRE) sites and transcription factors were in silico predicted in regulatory regions of Lif gene. DNA methylation status and histone modifications (histone 3 and 4 acetylation (H3Ac and H4Ac) and H3 lysine-27-trimethylation (H3K27me3)) were assessed. GBH and Gly decreased Lif mRNA levels and caused DNA hypermethylation. GBH increased H3Ac levels, whereas Gly reduced them; both compounds enhanced H3K27me3 levels. Finally, both GBH and Gly induced similar epigenetic alterations in the regulatory regions of Lif.

CRISPR-Cpf1 system and its applications in animal genome editing

The clustered regularly interspaced short palindromic repeats (CRISPR) and their associated protein (Cas) system is a gene editing technology guided by RNA endonuclease. The CRISPR-Cas12a (also known as CRISPR-Cpf1) system is extensively utilized in genome editing research due to its accuracy and high efficiency. In this paper, we primarily focus on the application of CRISPR-Cpf1 technology in the construction of disease models and gene therapy. Firstly, the structure and mechanism of the CRISPR-Cas system are introduced. Secondly, the similarities and differences between CRISPR-Cpf1 and CRISPR-Cas9 technologies are compared. Thirdly, the main focus is on the application of the CRISPR-Cpf1 system in cell and animal genome editing. Finally, the challenges faced by CRISPR-Cpf1 technology and corresponding strategies are analyzed. Although CRISPR-Cpf1 technology has certain off-target effects, it can effectively and accurately edit cell and animal genomes, and has significant advantages in the preclinical research.

Revealing the mechanism of fiber promoting sow embryo implantation by altering the abundance of uterine fluid proteins: A proteomic perspective

Many studies have shown that fiber in the diet plays an important role in improving the reproductive performance of sows, but there is rarely research on the impact of fiber on early embryo implantation. This study used 4D-Label free technology to identify and analyze the effect of the fiber composition in the diet on the protein in the early pregnancy uterine fluid (UF) of sows. The results indicate that ratio of insoluble fibers to soluble fibers (ISF/SF) 4.89 can increase the concentration of progesterone (PROG) and reduce tumor necrosis factorα (TNF-α) concentration in sow UF. In addition, through 4D-Label free, we identified a total of 4248 proteins, 38 proteins abundance upregulated and 283 proteins abundance downregulated in UF. Through enrichment analysis of these differential abundance proteins (DAPs), it was found that these differential proteins are mainly related to the docking of extracellular vesicles, vesicular transport, inflammatory response, and insulin resistance. Therefore, the results of this study reveal the possible mechanism by which fiber improves the reproductive performance of sows, laying a theoretical foundation for future research on the effects of diet on reproduction. SIGNIFICANCE: This study demonstrates the importance of dietary fiber for early embryo implantation in sows. The effect of dietary ISF/SF on early embryo implantation in sows was elucidated from a proteomic perspective through 4D-Label free technology. This study not only has significant implications for improving sow reproductive efficiency, but also provides important theoretical references for studying early miscarriage and reproductive nutrition in human pregnancy.

The presence of blastocyst within the uteri facilitates lumenal epithelium transformation for implantation via upregulating lysosome proteostasis activity

ABBREVIATIONS

ACTB: actin beta; AREG: amphiregulin; ATP6V0A4: ATPase, H+ transporting, lysosomal V0 subunit A4; Baf A1: bafilomycin A1; BSA: bovine serum albumin; CLDN1: claudin 1; CTSB: cathepsin B; DEGs: differentially expressed genes; E2: 17β-estradiol; ESR: estrogen receptor; GATA2: GATA binding protein 2; GLA: galactosidase, alpha; GO: gene ontology; HBEGF: heparin-binding EGF-like growth factor; IGF1R: insulin-like growth factor 1 receptor; Ihh: Indian hedgehog; ISH: in situ hybridization; LAMP1: lysosomal-associated membrane protein 1; LCM: laser capture microdissection; Le: lumenal epithelium; LGMN: legumain; LIF: leukemia inhibitory factor; LIFR: LIF receptor alpha; MSX1: msh homeobox 1; MUC1: mucin 1, transmembrane; P4: progesterone; PBS: phosphate-buffered saline; PCA: principal component analysis; PPT1: palmitoyl-protein thioesterase 1; PGR: progesterone receptor; PSP: pseudopregnancy; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; qPCR: quantitative real-time polymerase chain reaction; SP: pregnancy; TFEB: transcription factor EB.

Non-human primate models for understanding the impact of the microbiome on pregnancy and the female reproductive tract†

The microbiome has been shown, or implicated to be involved, in multiple facets of human health and disease, including not only gastrointestinal health but also metabolism, immunity, and neurology. Although the predominant focus of microbiome research has been on the gut, other microbial communities such as the vaginal or cervical microbiome are likely involved in physiological homeostasis. Emerging studies also aim to understand the role of different microbial niches, such as the endometrial or placental microbial communities, on the physiology and pathophysiology of reproduction, including their impact on reproductive success and the etiology of adverse pregnancy outcomes (APOs). The study of the microbiome during pregnancy, specifically how changes in maternal microbial communities can lead to dysfunction and disease, can advance the understanding of reproductive health and the etiology of APOs. In this review, we will discuss the current state of non-human primate (NHP) reproductive microbiome research, highlight the progress with NHP models of reproduction, and the diagnostic potential of microbial alterations in a clinical setting to promote pregnancy health. NHP reproductive biology studies have the potential to expand the knowledge and understanding of female reproductive tract microbial communities and host-microbe or microbe-microbe interactions associated with reproductive health through sequencing and analysis. Furthermore, in this review, we aim to demonstrate that macaques are uniquely suited as high-fidelity models of human female reproductive pathology.

Estrogen signaling encourages blastocyst development and implantation potential

PURPOSE

Estrogen is well-known for preparing uterine receptivity. However, its roles in regulating embryo development and implantation are unclear. Our objective was to characterize estrogen receptor 1 (ESR1) in human and mouse embryos and determine the effect of estradiol (E2) supplementation on pre- and peri-implantation blastocyst development.

METHODS

Mouse embryos, 8-cell through hatched blastocyst stages, and human embryonic days 5-7 blastocysts were stained for ESR1 and imaged using confocal microscopy. We then treated 8-cell mouse embryos with 8 nM E2 during in vitro culture (IVC) and examined embryo morphokinetics, blastocyst development, and cell allocation into the inner cell mass (ICM) and trophectoderm (TE). Finally, we disrupted ESR1, using ICI 182,780, and evaluated peri-implantation development.

RESULTS

ESR1 exhibits nuclear localization in early blastocysts followed by aggregation, predominantly in the TE of hatching and hatched blastocysts, in human and mouse embryos. During IVC, most E2 was absorbed by the mineral oil, and no effect on embryo development was found. When IVC was performed without an oil overlay, embryos treated with E2 exhibited increased blastocyst development and ICM:TE ratio. Additionally, embryos treated with ICI 182,780 had significantly decreased trophoblast outgrowth during extended embryo culture.

CONCLUSION

Similar ESR1 localization in mouse and human blastocysts suggests a conserved role in blastocyst development. These mechanisms may be underappreciated due to the use of mineral oil during conventional IVC. This work provides important context for how estrogenic toxicants may impact reproductive health and offers an avenue to further optimize human-assisted reproductive technology (ART) to treat infertility.

IL-10: A bridge between immune cells and metabolism during pregnancy

Energy metabolism plays a crucial role in the immune system. In addition to providing vital energy for cell growth, reproduction and other cell activities, the metabolism of nutrients such as glucose and lipids also have significant effects on cell function through metabolites, metabolic enzymes, and changing metabolic status. Interleukin-10 (IL-10), as a pleiotropic regulator, can be secreted by a diverse set of cells and can also participate in regulating the functions of various cells, thereby playing an essential role in the formation and maintenance of immune tolerance in pregnancy. Studies on the regulatory effects and mechanisms of IL-10 on immune cells are extensive; however, research from a metabolic perspective is relatively negligible. Here, we have discussed old and new data on the relationship between IL-10 and metabolism. The data show that alterations in cellular metabolism and specific metabolites regulate IL-10 production of immune cells. Moreover, IL-10 regulates immune cell phenotypes and functions by modulating oxidative phosphorylation and glycolysis. This review summarizes some earlier observations regarding IL-10 and its relationship with immune cells in pregnancy, and also presents recent research on the link between IL-10 and metabolism, highlighting the potential relationship between IL-10, immune cells, and energy metabolism during pregnancy.

Prss29 Cre recombinase mice are useful to study adult uterine gland function

All mammalian uteri contain glands in their endometrium that develop only or primarily after birth. In mice, those endometrial glands govern post implantation pregnancy establishment via regulation of blastocyst implantation, stromal cell decidualization, and placental development. Here, we describe a new uterine glandular epithelium (GE) specific Cre recombinase mouse line that is useful for the study of uterine gland function during pregnancy. Utilizing CRISPR-Cas9 genome editing, Cre recombinase was inserted into the endogenous serine protease 29 precursor (Prss29) gene. Both Prss29 mRNA and Cre recombinase activity was specific to the GE of the mouse uterus following implantation, but was absent from other areas of the female reproductive tract. Next, Prss29-Cre mice were crossed with floxed forkhead box A2 (Foxa2) mice to conditionally delete Foxa2 specifically in the endometrial glands. Foxa2 was absent in the glands of the post-implantation uterus, and Foxa2 deleted mice exhibited complete infertility after their first pregnancy. These results establish that Prss29-Cre mice are a valuable resource to elucidate and explore the functions of glands in the adult uterus.

Investigation of the endometrial receptivity status in experimental hypothyroid-induced female rats

OBJECTIVES

This study aimed to investigate hypothyroidism's effects on endometrial receptivity, creating an experimental hypothyroidism model in female rats.

MATERIALS AND METHODS

To induce hypothyroidism in rats of Hipotiroid-ER and Treatment-ER groups, 0.05% 6-propyl-2-thiouracil was freshly added to their drinking water for 8 weeks and then the endometrial receptivity model was applied and sacrificed on the fifth day. In the Treatment-ER group, after sc-administration of 0.8 µg/100 g L-thyroxine for 10 days, the endometrial receptivity model was applied to the rats and sacrificed on the fifth day.

RESULTS

In the histopathological evaluation, epithelial degeneration, vacuolization, enlargement of the uterine glands, and morphological disorders were observed in the endometrial layer of the Hypothyroid-ER group. However, these pathologies were significantly alleviated in the Treatment-ER group. Integrin β3, integrin αvβ3, LIF, and HOXA10 immune reaction intensities were high in the Control-ER and Treatment-ER groups, while in the Hypothyroid-ER group, integrin β3, integrin αvβ3, LIF, and HOXA10 immunoreactivity intensities were low. Also, while MUC1 immunoreactivity was high in the Hypothyroid-ER group, it was low in the other groups. In biochemical analysis, a significant increase in the TSH and progesterone levels and a significant decrease in the FT4, E2, FSH, and LH levels in the Hypothyroid-ER group compared with the Control-ER group were observed. Also, all hormone levels were significantly ameliorated in the rats of the Treatment-ER group compared with the Hypothyroid-ER group.

CONCLUSION

The results obtained showed that hypothyroidism had a significant effect on endometrial receptivity-the histopathological and biochemical changes caused by hypothyroidism in the experimental rat model were ameliorated with L-thyroxine treatment.

Role of SIRT1 and Progesterone Resistance in Normal and Abnormal Endometrium

CONTEXT

Progesterone resistance, a known pathologic condition associated with a reduced cellular response to progesterone and heightened estrogen responses, appears to have a normal physiologic role in mammalian reproduction. The molecular mechanism responsible for progesterone resistance in normal and abnormal endometrium remains unclear.

OBJECTIVE

To examine the roles of sirtuin-1 (SIRT1) in normal endometrium as well as endometrium associated with infertility and endometriosis, as an epigenetic modulator associated with progesterone resistance.

METHODS

SIRT1 expression was examined by Western blot, quantitative real-time polymerase chain reaction, and immunohistochemistry in mouse uterus and human endometrium. Mice with uterine specific Sirt1 overexpression were developed to examine SIRT1's role in endometrial function and endometriosis development. EX-527, a SIRT1 inhibitor, and SRT1720, a SIRT1 agonist, were also used to evaluate SIRT1 effect on endometriosis.

RESULTS

In normal healthy women, endometrial SIRT1 is expressed only during menses. SIRT1 was dramatically overexpressed in the endometrium from women with endometriosis in both the epithelium and stroma. In mice, SIRT1 is expressed at the time of implantation between day 4.5 and 5.5 of pregnancy. Overexpression of SIRT1 in the mouse uterus leads to subfertility due to implantation failure, decidualization defects and progesterone resistance. SIRT1 overexpression in endometriotic lesions promotes worsening endometriosis development. EX-527 significantly reduced the number of endometriotic lesions in the mouse endometriosis model.

CONCLUSIONS

SIRT1 expression and progesterone resistance appears to play roles in normal endometrial functions. Aberrant SIRT1 expression contributes to progesterone resistance and may participate in the pathophysiology of endometriosis. SIRT1 is a novel and targetable protein for the diagnosis as well as treatment of endometriosis and the associated infertility seen in this disease.

Annexin A2 acts as an adherent molecule under the regulation of steroids during embryo implantation

We previously showed that annexin A2 (Axna2) was transiently expressed at the embryo-uterine luminal epithelium interface during the window of implantation and was involved in mouse embryo implantation. At the same time, Axna2 was reported to be upregulated in human receptive endometrium, which was critical for embryo attachment as an intracellular molecule. Here, we identified Axna2 as a membrane-bound molecule on human endometrial epithelial cells and trophoblast cells, and the outer surface membrane-bound Axna2 was involved in human embryo attachment. In addition, physiological levels of estrogen and progesterone increased the expression of overall Axna2 as well as that in the extracellular surface membrane protein fraction in human endometrial cells. Furthermore, p11 (or S100A10, a member of the S100 EF-hand family protein, molecular weight 11 kDa) was involved in the translocation of Axna2 to the outer surface membrane of endometrial epithelial cells without affecting its overall expression. Finally, the surface relocation of Axna2 was also dependent on cell-cell contact and calcium binding. A better understanding of the function and regulation of Axna2 in human endometrium may help us to identify a potential therapeutic target for subfertile and infertile patients.

Generation and analysis of Prss28 and Prss29 deficient mice using CRISPR-Cas9 genome-editing

Glands of the uterus are essential for the establishment of pregnancy in mice and their products regulate embryo implantation and stromal cell decidualization critical for pregnancy establishment. Forkhead box A2 (FOXA2) is expressed specifically in the glands and a critical regulator of their differentiation, development and function. Progesterone and FOXA2 regulate members of a serine proteinase gene family (Prss28 and Prss29). Here, CRISPR-Cas9 genome-editing was used to create mice with a heterozygous or homozygous deletion of Prss28 or/and Prss29 to determine their biological roles in uterine function. Female mice lacking Prss28 and Prss29 or both developed normally and were fertile without alterations in uterine histoarchitecture, uterine gland number, or and gene expression. Thus, Prss28 and Prss29 are dispensable for female fertility and do not impact endometrial gland development or uterine function mice.

The Disorders of Endometrial Receptivity in PCOS and Its Mechanisms

Polycystic ovary syndrome (PCOS) is a mysterious and complicated endocrine disease with the combination of metabolic, reproductive, psychological dysfunctions. Impaired endometrial receptivity and ovulation disorders/anovulation are both important causes of PCOS-related infertility. However, change in endometrium has never received the same attention as ovulatory dysfunction. Besides, putting emphasis on endometrial function may be more realistic for PCOS-related infertility, given the wide use of assisted reproductive technology. The present review focuses on the disorders of endometrial receptivity of patients with PCOS, summarizes the changes of the indicators of endometrial receptivity including leukemia inhibitory factor, homeobox genes A, pinopodes, αvβ3-integrin, and intercellular junctions and also analyzes the possible mechanisms of decreased endometrial receptivity and its relationship with the main endocrine and metabolic disorders of PCOS such as hyperandrogenism, inflammation, insulin resistance, and obesity. Despite several biomarkers have been found to be associated with decreased endometrial receptivity in PCOS, the clinical relevance of these findings still awaits future clarification.

High, not low-dose of stanozolol (Anabolic - androgenic steroid) impedes embryo implantation by attenuating endometrial receptivity in the mouse, Mus musculus

The present investigation is aimed at evaluating the efficacy of one of the anabolic -androgenic steroids, stanozolol (ST), on establishment and maintenance of pregnancy in mice. A total of 40 female mice were assigned to three experimental groups. Stanozolol was dosed subcutaneously (low-dose, 0.5 mg/kg bwt; high-dose, 5.0 mg/kg bwt or 1% alcohol-baseline control) for 30 consecutive days. On the 31st day, treatment was withdrawn. The estrous cycle was disrupted in both treatment groups and its resumption was dose dependent. Following estrous resumption, mice were allowed to mate. Results reveal that the low-dose ST-treated mice maintained gestation until term with reduced litter size, while high-dose-treated mice divulged vaginal plug at frequent intervals, indicating conception failure. Because pregnancy failure was noticed in high-dose-treated mice, they were autopsied on GD1.5 and 4.5. Interestingly, neither dose of stanozolol affected early embryonic development or blastocyst hatching. A decrease in the number of corpora lutea in both treated groups suggests it affects either ovulation or recruitment of follicles that occurs in each cycle for maturation. In high-dose-treated mice, decreased serum levels of estradiol, progesterone and increased testosterone along with downregulated endometrial expression of ERα and PR suggest the deficiency of steroid hormones and their respective receptors. Decreased ovarian expression of ERα, hyperexpression of PRLR, AR and abated progesterone secretion led to luteal dysfunction, consequently attenuating endometrial receptivity. Therefore, in high-dose-treated mice, decreased maternal estradiol and progesterone levels and their receptors during implantation hindered signaling to LIF and Hoxa-10, resulting in pragmatic implantation failure.

The Complicated Effects of Extracellular Vesicles and Their Cargos on Embryo Implantation

As a rate-limiting step in pregnancy, embryo implantation is highly dependent on intercellular communication. Extracellular vesicles (EVs) are newly identified to be important in the course of intercellular communication. EVs have been isolated from a wide variety of biofluids and tissues, including plasma, liver, uterine, semen, embryo, etc. The present and future use of EVs not only as biomarkers, but also as targeting drug delivery system, is promisingly pave the way for advanced comprehension of implantation failure in reproductive diseases. However, as the precise mechanisms of EVs in embryo implantation has not been elucidated yet. Herein, we summarize the current knowledge on the diverse effects of EVs from various sources and their cargos such as microRNA, long non-coding RNA, protein, etc. on embryo implantation, and the potential mechanisms of EVs in reproductive diseases such as recurrent implantation failure, polycystic ovary syndrome and endometriosis. It is essential to note that many of the biologically plausible functions of EVs in embryo implantation discussed in present literatures still need further research in vivo.

Allogeneic Embryos Disregulate Leukemia Inhibitory Factor (LIF) and Its Receptor in the Porcine Endometrium During Implantation

Despite its advantages for pig breeding, embryo transfer (ET) has a major handicap: high embryo mortality during the pre- and implantation period, probably caused by divergent phenomena of tolerance between the immunologically unrelated (i.e., allogeneic) embryos and the recipient sow. Thus, to reach a similar maternal tolerance as in conventional breeding by artificial insemination (AI) would be the key to ET-success. For this reason, we studied the expression of the leukemia inhibitory factor (LIF) cytokine and its receptor in the pig endometrium during the implantation period (days 18 and 24) in sows subjected to ET (AL group) vs. post-cervical-AI controls (Hemi-AL group). Quantification of expression was performed at both mRNA (rt-qPCR) and protein (WB) levels. The expression of endometrial LIF on day 24 was considerably lower in ET than in AI pregnancies. Correlations between endometrial mRNA levels of LIF and LIF-R showed that, contrary to early AI-pregnancies, ET-pregnancies lack an inverse relation between cytokine and receptor levels. In conclusion, ET-pregnancies lack sufficient endometrial levels of LIF to develop adequate immunotolerance mechanisms to prevent the rejection of allogeneic ET-embryos.

Differential roles of uterine epithelial and stromal STAT3 coordinate uterine receptivity and embryo attachment

Although it has been reported that uterine signal transducer and activator of transcription 3 (STAT3) is essential for embryo implantation, the exact roles of uterine epithelial and stromal STAT3 on embryo implantation have not been elucidated. To address this issue, we generated Stat3-floxed/Ltf-iCre (Stat3-eKO), Stat3-floxed/Amhr2-Cre (Stat3-sKO), and Stat3-floxed/Pgr-Cre (Stat3-uKO) mice to delete Stat3 in uterine epithelium, uterine stroma, and whole uterine layers, respectively. We found that both epithelial and stromal STAT3 have critical roles in embryo attachment because all the Stat3-eKO and Stat3-sKO female mice were infertile due to implantation failure without any embryo attachment sites. Stat3-eKO uteri showed indented structure of uterine lumen, indicating the role of epithelial STAT3 in slit-like lumen formation in the peri-implantation uterus. Stat3-sKO uteri exhibited hyper-estrogenic responses and persistent cell proliferation of the epithelium in the peri-implantation uterus, suggesting the role of stromal STAT3 in uterine receptivity. In addition, Stat3-uKO female mice possessed not only the characteristic of persistent epithelial proliferation but also that of indented structure of uterine lumen. These findings indicate that epithelial STAT3 controls the formation of slit-like structure in uterine lumen and stromal STAT3 suppresses epithelial estrogenic responses and cell proliferation. Thus, epithelial and stromal STAT3 cooperatively controls uterine receptivity and embryo attachment through their different pathways.

The therapeutic effects and underlying mechanisms of the intrauterine perfusion of granulocyte colony-stimulating factor on a thin-endometrium rat model

AIMS

This study aims to investigate the effects of intrauterine perfusion of granulocyte colony-stimulating factor (G-CSF) on a thin-endometrium rat model.

MAIN METHODS

Twenty rats in two groups of 10 were used. Group I was perfused with normal saline (NS) in the right uterine horn and 95% ethanol in the left one. Group II was bilaterally perfused with 95% ethanol into the uterine horns. After three estrous cycles, Group II was perfused with NS in the right uterine horn and G-CSF (30 μg/kg) in the left one. Hematoxylin-eosin (HE) and immunohistochemistry (IHC) staining were used to detect changes in endometrial thickness and expression of cytokeratin 19 (CK19) and vimentin (Vim). The relative expression levels of vascular endothelial growth factor (Vegf) and leukemia inhibitory factor (Lif) were also tested via reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) and Western-blot analyses.

KEY FINDINGS

G-CSF treatment significantly increased the thickness of the endometrium in the 95% ethanol-induced thin-endometrium rat model. The expression levels of endometrial glandular epithelial cell marker for CK19 and stromal cell marker Vim were augmented in the G-CSF-treated group compared with the control group. Moreover, G-CSF treatment stimulated the expression of VEGF and LIF in the 95% ethanol-induced thin-endometrium rat model.

SIGNIFICANCE

G-CSF intrauterine perfusion improved endometrial receptivity in the thin-endometrium rat model by stimulating endometrial proliferation and angiogenesis.

Sexually dimorphic effects of forkhead box a2 (FOXA2) and uterine glands on decidualization and fetoplacental development

Glands of the uterus are essential for pregnancy establishment. Forkhead box A2 (FOXA2) is expressed specifically in the glands of the uterus and a critical regulator of glandular epithelium (GE) differentiation, development, and function. Mice with a conditional deletion of FOXA2 in the adult uterus, created using the lactotransferrin iCre (Ltf-iCre) model, have a morphologically normal uterus with glands, but lack FOXA2-dependent GE-expressed genes, such as leukemia inhibitory factor (LIF). Adult FOXA2 conditional knockout (cKO; Ltf ^iCre/+ Foxa2 ^f/f ) mice are infertile due to defective embryo implantation arising from a lack of LIF, a critical implantation factor of uterine gland origin. However, intraperitoneal injections of LIF can initiate embryo implantation in the uterus of adult FOXA2 cKO mice with pregnancies maintained to term. Here, we tested the hypothesis that FOXA2-regulated genes in the uterine glands impact development of the decidua, placenta, and fetus. On gestational day 8.5, the antimesometrial and mesometrial decidua transcriptome was noticeably altered in LIF-replaced FOXA2 cKO mice. Viable fetuses were reduced in FOXA2 cKO mice on gestational days 12.5 and 17.5. Sex-dependent differences in fetal weight, placenta histoarchitecture, and the placenta and metrial gland transcriptome were observed between control and FOXA2 cKO mice. The transcriptome of the placenta with a female fetus was considerably more altered than the placenta with a male fetus in FOXA2 cKO dams. These studies reveal previously unrecognized sexually dimorphic effects of FOXA2 and uterine glands on fetoplacental development with potential impacts on offspring health into adulthood.

Adrenomedullin insufficiency alters macrophage activities in fallopian tube: a pathophysiologic explanation of tubal ectopic pregnancy

Ectopic pregnancy is the major cause of maternal morbidity and mortality in the first trimester of pregnancy. Tubal ectopic pregnancy (TEP) accounts for nearly 98% of all ectopic pregnancies. TEP is usually associated with salpingitis but the underlying mechanism in salpingitis leading to TEP remains unclear. Adrenomedullin (ADM) is a peptide hormone abundantly expressed in the fallopian tube with potent anti-inflammatory activities. Its expression peaks at the early luteal phase when the developing embryo is being transported through the fallopian tube. In the present study, we demonstrated reduced expression of ADM in fallopian tubes of patients with salpingitis and TEP. Using macrophages isolated from the fallopian tubes of these women, our data revealed that the salpingistis-associated ADM reduction contributed to aggravated pro-inflammatory responses of the tubal macrophages resulting in production of pro-inflammatory and pro-implantation cytokines IL-6 and IL-8. These cytokines activated the expression of implantation-associated molecules and Wnt signaling pathway predisposing the tubal epithelium to an adhesive and receptive state for embryo implantation. In conclusion, this study provided evidence for the role of ADM in the pathogenesis of TEP through regulating the functions of tubal macrophages.

Potential roles for the kisspeptin/kisspeptin receptor system in implantation and placentation

BACKGROUND

Initially identified as suppressors of metastasis in various types of cancer, kisspeptins are a family of neuropeptides that are key regulators of the mammalian reproductive axis. Accumulating evidence has shown that kisspeptin is able to control both the pulsatile and surge GnRH release, playing fundamental roles in female reproduction, which include the secretion of gonadotropins, puberty onset, brain sex differentiation, ovulation and the metabolic regulation of fertility. Furthermore, recent studies have demonstrated the involvement of the kisspeptin system in the processes of implantation and placentation. This review summarizes the current knowledge of the pathophysiological role and utility of these local placental regulatory factors as potential biomarkers during the early human gestation.

OBJECTIVE AND RATIONALE

A successful pregnancy, from the initiation of embryo implantation to parturition, is a complex process that requires the orchestration of a series of events. This review aims to concisely summarize what is known about the role of the kisspeptin system in implantation, placentation, early human pregnancy and pregnancy-related disorders, and to develop strategies for predicting, diagnosing and treating these abnormalities.

SEARCH METHODS

Using the PubMed and Google Scholar databases, we performed comprehensive literature searches in the English language describing the advancement of kisspeptins and the kisspeptin receptor (KISS1R) in implantation, placentation and early pregnancy in humans, since its initial identification in 1996 and ending in July 2018.

OUTCOMES

Recent studies have shown the coordinated spatial and temporal expression patterns of kisspeptins and KISS1R during human pregnancy. The experimental data gathered recently suggest putative roles of kisspeptin signaling in the regulation of trophoblast invasion, embryo implantation, placentation and early pregnancy. Dysregulation of the kisspeptin system may negatively affect the processes of implantation as well as placentation. Clinical studies indicate that the circulating levels of kisspeptins or the expression levels of kisspeptin/KISS1R in the placental tissues may be used as potential diagnostic markers for women with miscarriage and gestational trophoblastic neoplasia.

WIDER IMPLICATIONS

Comprehensive research on the pathophysiological role of the kisspeptin/KISS1R system in implantation and placentation will provide a dynamic and powerful approach to understanding the processes of early pregnancy, with potential applications in observational and analytic screening as well as the diagnosis, prognosis and treatment of implantation failure and early pregnancy-related disorders.

Electroporation of AsCpf1/RNP at the Zygote Stage is an Efficient Genome Editing Method to Generate Knock-Out Mice Deficient in Leukemia Inhibitory Factor

BACKROUND

CRISPR/Cpf1 is a class II, type V RNA-guided endonuclease that is distinct from the type II CRISPR/Cas9 nuclease, widely used for genome editing. Cpf1 is a smaller and simpler endonuclease than Cas9, overcoming some limitations of the CRISPR/Cas9 system. The applications of CRISPR to rodent embryos for the production of knock-out (KO) mice have been achieved mainly by microinjection, which requires heavily-equipped instruments with skillful hands. Here, we evaluated the genome editing efficiency between Cpf1/mRNA and Cpf1/ribonuclear protein (RNP) in mouse embryos, and established an easy, fast, and technically less demanding method to produce KO mice using electroporation of the Cfp1/RNP system.

METHODS

The efficiency of electroporation-based delivery of AsCpf1/mRNA and AsCpf1/RNP to target exon 3 of leukemia inhibitory factor (Lif) into mouse zygotes was evaluated. Embryos that developed to the two-cell stage after zygote electroporation were transferred into the oviducts of surrogate mothers to produce AsCpf1-mediated LIF KO mice. The genome editing efficiency of blastocysts and pups was tested using the T7E1 assay and/or DNA sequencing. Congenital abnormalities and reproductive phenotypes in LIF KO mice produced by electroporation with AsCpf1/RNP were examined.

RESULTS

Survival and two-cell development of electroporated zygotes were comparable between the AsCpf1/mRNA and AsCpf1/RNP groups, whereas genome editing efficiency was relatively higher in the AsCpf1/RNP group (13.3% vs 18.1% at blastocyst and 33.3% vs 45.5% at offspring), respectively. Two mouse lines with a frameshift mutation in exon 3 of the Lif gene were established from the AsCpf1/RNP group. All congenital abnormalities of LIF KO mice produced by AsCpf1/RNP electroporation were observed. AsCpf1-mediated LIF KO mice showed postnatal growth retardation and implantation failure, both of which are major phenotypes of LIF KO mice generated by conventional gene targeting.

CONCLUSION

Electroporation of AsCpf1/RNP at the zygote stage is an efficient genome editing method to produce KO mice.

Hashimoto's thyroiditis impairs embryo implantation by compromising endometrial morphology and receptivity markers in euthyroid mice

BACKGROUND

Although thyroid dysfunction caused by Hashimoto's thyroiditis (HT) is believed to be related to implantation failure due to the underdevelopment of the receptive uterus, it is unknown whether HT itself, even in the euthyroid state, impairs embryo implantation associated with endometrial receptivity defects. To address whether HT itself can affect endometrial receptivity accompanied by implantation alterations, a euthyroid HT model was established in mice.

METHODS

Female NOD mice were immunized twice with thyroglobulin and adjuvant to induce the experimental HT model. Four weeks after the second treatment, the mice were normally mated, and pregnant ones were sacrificed in implantation window for thyroid-related parameter and steroid hormones measurements by electrochemiluminescence immunoassay and enzyme-linked immunosorbent assay and implantation site number calculation by uptake of Chicago Blue dye. In addition, certain morphological features of endometrial receptivity were observed by hematoxylin-eosin staining and scanning electron microscopy, and the expression of other receptivity markers were analyzed by immunohistochemistry, RT-qPCR or Western Blot.

RESULTS

HT mice displayed intrathyroidal monocyte infiltration and elevated serum thyroid autoantibody levels without thyroid dysfunction, defined as euthyroid HT in humans. Euthyroid HT resulted in implantation failure, fewer pinopodes, retarded pinopode maturation, and inhibited expression of receptivity markers: estrogen receptor α (ERα), integrin β3, leukemia inhibitory factor (LIF), and cell adhesion molecule-1 (ICAM-1). Interestingly, despite this compromised endometrial receptivity response, no statistical differences in serum estradiol or progesterone level between groups were found.

CONCLUSIONS

These findings are the first to indicate that HT induces a nonreceptive endometrial milieu in the euthyroid state, which may underlie the detrimental effects of HT itself on embryo implantation.

Uterine Glands: Developmental Biology and Functional Roles in Pregnancy

All mammalian uteri contain glands in the endometrium that develop only or primarily after birth. Gland development or adenogenesis in the postnatal uterus is intrinsically regulated by proliferation, cell-cell interactions, growth factors and their inhibitors, as well as transcription factors, including forkhead box A2 (FOXA2) and estrogen receptor α (ESR1). Extrinsic factors regulating adenogenesis originate from other organs, including the ovary, pituitary, and mammary gland. The infertility and recurrent pregnancy loss observed in uterine gland knockout sheep and mouse models support a primary role for secretions and products of the glands in pregnancy success. Recent studies in mice revealed that uterine glandular epithelia govern postimplantation pregnancy establishment through effects on stromal cell decidualization and placental development. In humans, uterine glands and, by inference, their secretions and products are hypothesized to be critical for blastocyst survival and implantation as well as embryo and placental development during the first trimester before the onset of fetal-maternal circulation. A variety of hormones and other factors from the ovary, placenta, and stromal cells impact secretory function of the uterine glands during pregnancy. This review summarizes new information related to the developmental biology of uterine glands and discusses novel perspectives on their functional roles in pregnancy establishment and success.

Evaluation of Endometrial Receptivity by Measuring HOXA-10, HOXA-11, and Leukemia Inhibitory Factor Expression in Patients with Polycystic Ovary Syndrome

Context:

Polycystic ovary syndrome (PCOS) is an important cause of infertility. In women with PCOS have increased rate of spontaneous abortion and reduced rate of conception. HOXA–10 and HOXA–11 are proteinous products of homeobox gene group and play an important role during implantation.

Aims:

The aim of this study was to evaluate endometrial receptivity by measuring HOXA–10, HOXA–11, and leukemia inhibitory factor (LIF) gene expressions in women with PCOS.

Settings and Design:

A tertiary referral center.

Materials and Methods:

This study was conducted on reproductive age women with abnormal uterine bleeding without sonographically proven anatomical reason. Endometrial sampling procedures were done in proliferative phase using low-pressure endometrial suction device to exclude endometrial pathology. HOXA–10, HOXA–11, and LIF gene expressions were measured from endometrial sampling material. Blood sample was taken to measure serum estradiol level on the day of endometrial sampling.

Statistical Analysis Used:

Statistical analysis was performed using SPSS software version 17 (SPSS Inc., Chicago, IL, USA). Mann–Whitney U-test was used to compare the variables.

Results:

A total of 53 patients were included in this study. Study group consisted of 33 patients with PCOS. Gene expressions of HOXA–10, HOXA–11, and LIF were significantly lower in patients with PCOS (P < 0.05).

Conclusions:

This study results showed that in patients with PCOS have decreased gene expression of HOXA-10, HOXA-11, and LIF which might contribute PCOS-related infertility.

Uterine Gαq/11 signaling, in a progesterone-dependent manner, critically regulates the acquisition of uterine receptivity in the female mouse

A nonreceptive uterus is a major cause of embryo implantation failure. This study examined the importance of the Gαq/11-coupled class of GPCRs as regulators of uterine receptivity. Mice were created lacking uterine Gαq and Gα11; as a result, signaling by all uterine Gαq/11-coupled receptors was disrupted. Reproductive profiling of the knockout females revealed that on d 4 of pregnancy, despite adequate serum progesterone (P4) levels and normal P4 receptor (PR) expression, there was no evidence of PR signaling. This resulted in the down-regulation of heart and neural crest derivatives expressed 2, Kruppel-like factor 15, and cyclin G1 and the subsequent persistent proliferation of the luminal epithelium. Aquaporin (Aqp) 11 was also potently down-regulated, whereas Aqp5/AQP5 expression persisted, resulting in the inhibition of luminal closure. Hypertrophy of the myometrial longitudinal muscle was also dramatically diminished, likely contributing to the observed implantation failure. Further analyses revealed that a major mechanism via which uterine Gαq/11 signaling induces PR signaling is through the transcriptional up-regulation of leucine-rich repeat-containing GPCR 4 (Lgr4). LGR4 was previously identified as a trigger of PR activation and signaling. Overall, this study establishes that Gαq/11 signaling, in a P4-dependent manner, critically regulates the acquisition of uterine receptivity in the female mouse, and disruption of such signaling results in P4 resistance.-de Oliveira, V., Schaefer, J., Calder, M., Lydon, J. P., DeMayo, F. J., Bhattacharya, M., Radovick, S., Babwah, A. V. Uterine Gαq/11 signaling, in a progesterone-dependent manner, critically regulates the acquisition of uterine receptivity in the female mouse.

New Insights into the Process of Placentation and the Role of Oxidative Uterine Microenvironment

For a successful pregnancy to occur, a predecidualized receptive endometrium must be invaded by placental differentiated cells (extravillous trophoblast cells (EVTs)) and, at the same time, continue decidualization. EVT invasion is aimed at anchoring the placenta to the maternal uterus and ensuring local blood supply increase necessary to provide normal placental and foetal development. The first is achieved by migrating through the maternal endometrium and deeper into the myometrium, while the second by transforming uterine spiral arteries into large vessels. This process is a tightly regulated battle comprising interests of both the mother and the foetus. Invading EVTs are required to perform a scope of functions: move, adhere, proliferate, differentiate, interact, and digest the extracellular matrix (ECM); tolerate hypoxia; transform the maternal spiral arteries; and die by apoptosis. All these functions are modulated by their surrounding microenvironment: oxygen, soluble factors (e.g., cytokines, growth factors, and hormones), ECM proteins, and reactive oxygen species. A deeper comprehension of oxidative uterine microenvironment contribution to trophoblast function will be addressed in this review.

Cigarette smoke exposure reduces leukemia inhibitory factor levels during respiratory syncytial viral infection

Background: Viral infections are considered a major driving factor of chronic obstructive pulmonary disease (COPD) exacerbations and thus contribute to disease morbidity and mortality. Respiratory syncytial virus (RSV) is a frequently detected pathogen in the respiratory tract of COPD patients during an exacerbation. We previously demonstrated in a murine model that leukemia inhibitory factor (LIF) expression was increased in the lungs during RSV infection. Subduing LIF signaling in this model enhanced lung injury and airway hypersensitivity. In this study, we investigated lung LIF levels in COPD patient samples to determine the impact of disease status and cigarette smoke exposure on LIF expression. Materials and methods: Bronchoalveolar lavage fluid (BALF) was obtained from healthy never smokers, smokers, and COPD patients, by written informed consent. Human bronchial epithelial (HBE) cells were isolated from healthy never smokers and COPD patients, grown at the air-liquid interface and infected with RSV or stimulated with polyinosinic:polycytidylic acid (poly (i:c)). Mice were exposed to cigarette smoke daily for 6 months and were subsequently infected with RSV. LIF expression was profiled in all samples. Results: In human BALF, LIF protein was significantly reduced in both smokers and COPD patients compared to healthy never smokers. HBE cells isolated from COPD patients produced less LIF compared to never smokers during RSV infection or poly (i:c) stimulation. Animals exposed to cigarette smoke had reduced lung levels of LIF and its corresponding receptor, LIFR. Smoke-exposed animals had reduced LIF expression during RSV infection. Two possible factors for reduced LIF levels were increased LIF mRNA instability in COPD epithelia and proteolytic degradation of LIF protein by serine proteases. Conclusions: Cigarette smoke is an important modulator for LIF expression in the lungs. Loss of LIF expression in COPD could contribute to a higher degree of lung injury during virus-associated exacerbations.

Similarities Between Embryo Development and Cancer Process Suggest New Strategies for Research and Therapy of Tumors: A New Point of View

Here, I propose that cancer stem cells (CSCs) would be equivalent to para-embryonic stem cells (p-ESCs), derived from adult cells de-re-programmed to a ground state. p-ESCs would differ from ESCs by the absence of genomic homeostasis. A p-ESC would constitute the cancer cell of origin (i-CSC or CSC0), capable of generating an initial tumor, corresponding to a pre-implantation blastocyst. In a niche with proper signals, it would engraft as a primary tumor, corresponding to a post-implantation blastocyst. i-CSC progeny would form primary pluripotent and slow self-renewing CSCs (CSC1s), blocked in an undifferentiated state, corresponding to epiblast cells; CSC1s would be tumor-initiating cells (TICs). CSC1s would generate secondary CSCs (CSC2s), corresponding to hypoblast cells; CSC2s would be tumor growth cells (TGCs). CSC1s/CSC2s would generate tertiary CSCs (CSC3s), with a mesenchymal phenotype; CSC3s would be tumor migrating cells (TMCs), corresponding to mesodermal precursors at primitive streak. CSC3s with more favorable conditions (normoxia), by asymmetrical division, would differentiate into cancer progenitor cells (CPCs), and these into cancer differentiated cells (CDCs), thus generating a defined cell hierarchy and tumor progression, mimicking somito-histo-organogenesis. CSC3s with less favorable conditions (hypoxia) would delaminate and migrate as quiescent circulating micro-metastases, mimicking mesenchymal cells in gastrula morphogenetic movements. In metastatic niches, these CSC3s would install and remain dormant in the presence of epithelial/mesenchymal transition (EMT) signals and hypoxia. But, in the presence of mesenchymal/epithelial transition (MET) signals and normoxia, they would revert to self-renewing CSC1s, reproducing the same cell hierarchy of the primary tumor as macro-metastases. Further similarities between ontogenesis and oncogenesis involving crucial factors, such as ID, HSP70, HLA-G, CD44, LIF, and STAT3, are strongly evident at molecular, physiological and immunological levels. Much experimental data about these factors led to considering the cancer process as ectopic rudimentary ontogenesis, where CSCs have privileged immunological conditions. These would consent to CSC development in an adverse environment, just like an embryo, which is tolerated, accepted and favored by the maternal organism in spite of its paternal semi-allogeneicity. From all these considerations, novel research directions, potential innovative tumor therapy and prophylaxis strategies might, theoretically, result.

Novel 3D in vitro models to evaluate trophoblast migration and invasion

PROBLEM

Embryo implantation depends on the interactions between the developing embryo and the maternal endometrium. Signals originating from the decidua play a critical role in the process of implantation and trophoblast invasion; however, the molecular mechanisms mediating this interaction are poorly understood. The objective of this study was to develop in vitro models that would mimic the processes of attachment, migration, and early invasion of the trophoblast.

METHODS OF STUDY

First trimester trophoblast cells (Sw.71 cells) were cultured in low attachment plates to form blastocyst-like spheroids (BLS). Epithelial-mesenchymal transition (EMT) characterization during BLS formation was determined by RT-PCR and Western Blot. The two 3D in vitro culture models consist of (a) trophoblast migration: BLS cultured in suspension (b) trophoblast invasion: human endometrium stromal cells (HESC) plated in the bottom of a 96-well plate, covered by Matrigel and BLS transferred on top. Matrigel was used to mimic the human endometrial extracellular matrix.

RESULTS

Using 3D cell culture systems and real-time imaging, we are able to determine the impact of endometrial factors on trophoblast cell function. Endometrial stromal cells promote blastocyst-like spheroid migration of trophoblast cells and invasion of the extracellular matrix.

CONCLUSION

We report the characterization of 3D in vitro models to evaluate the interaction between endometrial cells and trophoblast during the process of migration and invasion. The models are useful tools in order to further study the molecular mechanism of embryo-maternal uterine cells interactions.

Targeted ablation of Wnt4 and Wnt5a in Müllerian duct mesenchyme impedes endometrial gland development and causes partial Müllerian agenesis

Wnt4 and Wnt5a have well-established roles in the embryonic development of the female reproductive tract, as well as in implantation, decidualization, and ovarian function in adult mice. Although these roles appear to overlap, whether Wnt5a and Wnt4 are functionally redundant in these tissues has not been determined. We addressed this by concomitantly inactivating Wnt4 and Wnt5a in the Müllerian mesenchyme and in ovarian granulosa cells by crossing mice bearing floxed alleles to the Amhr2cre strain. Whereas fertility was reduced by ∼50% in Wnt4flox/flox; Amhr2cre/+ and Wnt5aflox/flox; Amhr2cre/+ females, Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice were either nearly or completely sterile. Loss of fertility was not due to an ovarian defect, as serum ovarian hormone levels, follicle counts, and ovulation rates were comparable to controls. Conversely, the uterus was abnormal in Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice, with thin myometrial and stromal layers, frequent fibrosis and a >90% reduction in numbers of uterine glands, suggesting redundant or additive roles of Wnt4 and Wnt5a in uterine adenogenesis. Loss of fertility in Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice was attributed to defects in decidualization, implantation, and placental development, the severity of which were proportional to the extent of gland loss. Furthermore, a third of Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ females had a partial agenesis of Müllerian duct-derived structures, but with normal oviducts and ovaries. Together, our results suggest that Wnt4 and Wnt5a play redundant roles in the development of the female reproductive tract, and may provide insight into the etiology of certain cases of Müllerian agenesis in women.

Leukemia inhibitory factor and its receptor: expression and regulation in the porcine endometrium throughout the estrous cycle and pregnancy

Objective

Leukemia inhibitory factor (LIF) binds to a heterodimeric receptor composed of LIF receptor (LIFR) and glycoprotein 130 (GP130) to transmit signals into the cell. LIF plays an important role in reproduction by regulating immune response, decidualization, and implantation in several species. However, the expression of LIF and LIFR in the endometrium throughout the estrous cycle and pregnancy in pigs is not fully understood.

Methods

We analyzed the expression of LIF and LIFR in the endometrium on days 0 (estrus), 3, 6, 9, 12, 15, and 18 of the estrous cycle, and days 12, 15, 30, 60, 90, and 114 of pregnancy, in conceptuses on days 12 and 15, and in chorioallantoic tissues on days 30, 60, 90, and 114 of pregnancy in pigs. We also determined the effects of estrogen and progesterone on the expression of LIF and LIFR in endometrial tissues.

Results

The expression of LIF increased in the endometrium during the late diestrus phase of the estrous cycle and during mid- to late- pregnancy, while the expression of LIFR increased during early pregnancy. The expression of LIF was induced by increasing doses of estrogen, whereas the expression of LIFR was induced by increasing doses of progesterone.

Conclusion

These results indicate that the expression of LIF and its receptor LIFR in the endometrium is regulated in a stage-specific manner during the estrous cycle and pregnancy, suggesting that LIF and its receptor signaling system may play critical roles in regulating endometrial function in pigs.

A historical review of blastocyst implantation research

Research development on blastocyst implantation was reviewed in three sections: primate implantation, ungulate farm animal implantation, and the general process of blastocyst implantation in small rodents. Future research directions of this area are suggested.

The critical role of uterine CD31 as a post-progesterone signal in early pregnancy

CD31 has been shown to play a role in endothelial cell migration and angiogenesis, which are critical to the formation and function of the endometrium and myometrium in uterine development during early pregnancy. However, the role of CD31 in uterine receptivity during blastocyst implantation is poorly understood. The pregnancy rate in CD31−/− female mice mated with CD31+/+ male mice was higher than that observed in CD31+/+ female mice mated with CD31+/+ male mice. During the receptive phase of implantation, uterine glands were more developed in CD31−/− mice than in CD31+/+ mice, and the uterine weights of CD31−/− mice were increased. Leukemia inhibitory factor (LIF) was highly expressed in the CD31−/− mice during implantation and the expression of LIF was up-regulated by estradiol-17β (E2) + progesterone (P4) in ovariectomized CD31−/− mice, compared with CD31+/+ mice at 8 h after hormone treatment. E2-induced protein synthesis was inhibited by P4 in the CD31+/+ uterus, but not in the uterus of CD31−/− mice. Also, STAT3, HAND2, LIF, and mTOR signals were enhanced in CD31−/− mice. Stromal DNA replication was highly activated in the uterus of CD31−/− mice, manifested by upregulated cyclin series signaling and PCNA expression after E2 + P4treatment. Collectively, CD31 inhibits E2-mediated epithelial proliferation via recruitment and phosphorylation of SHP-2 upon receiving P4signal in early pregnancy.

Loss of Endometrial Sodium Glucose Cotransporter SGLT1 is Detrimental to Embryo Survival and Fetal Growth in Pregnancy

Embryo implantation requires a hospitable uterine environment. A key metabolic change that occurs during the peri-implantation period, and throughout early pregnancy, is the rise in endometrial glycogen content. Glycogen accumulation requires prior cellular uptake of glucose. Here we show that both human and murine endometrial epithelial cells express the high affinity Na⁺-coupled glucose carrier SGLT1. Ussing chamber experiments revealed electrogenic glucose transport across the endometrium in wild type (Slc5a1^+/+) but not in SGLT1 deficient (Slc5a1^−/−) mice. Endometrial glycogen content, litter size and weight of offspring at birth were significantly lower in Slc5a1^−/− mice. In humans, SLC5A1 expression was upregulated upon decidualization of primary endometrial stromal cells. Endometrial SLC5A1 expression during the implantation window was attenuated in patients with recurrent pregnancy loss when compared with control subjects. Our findings reveal a novel mechanism establishing adequate endometrial glycogen stores for pregnancy. Disruption of this histiotrophic pathway leads to adverse pregnancy outcome.

The enigma of embryonic diapause

Embryonic diapause – a period of embryonic suspension at the blastocyst stage – is a fascinating phenomenon that occurs in over 130 species of mammals, ranging from bears and badgers to mice and marsupials. It might even occur in humans. During diapause, there is minimal cell division and greatly reduced metabolism, and development is put on hold. Yet there are no ill effects for the pregnancy when it eventually continues. Multiple factors can induce diapause, including seasonal supplies of food, temperature, photoperiod and lactation. The successful reactivation and continuation of pregnancy then requires a viable embryo, a receptive uterus and effective molecular communication between the two. But how do the blastocysts survive and remain viable during this period of time, which can be up to a year in some cases? And what are the signals that bring it out of suspended animation? Here, we provide an overview of the process of diapause and address these questions, focussing on recent molecular data.

Embryo implantation evolved from an ancestral inflammatory attachment reaction

The molecular changes that support implantation in eutherian mammals are necessary to establish pregnancy. In marsupials, pregnancy is relatively short, and although a placenta does form, it is present for only a few days before parturition. However, morphological changes in the uterus of marsupials at term mimic those that occur during implantation in humans and mice. We investigated the molecular similarity between term pregnancy in the marsupials and implantation in eutherian mammals using the gray short-tailed opossum (Monodelphis domestica) as a model. Transcriptomic analysis shows that term pregnancy in the opossum is characterized by an inflammatory response consistent with implantation in humans and mice. This immune response is temporally correlated with the loss of the eggshell, and we used immunohistochemistry to report that this reaction occurs at the materno-fetal interface. We demonstrate that key markers of implantation, including Heparin binding EGF-like growth factor and Mucin 1, exhibit expression and localization profiles consistent with the pattern observed during implantation in eutherian mammals. Finally, we show that there are transcriptome-wide similarities between the opossum attachment reaction and implantation in rabbits and humans. Our data suggest that the implantation reaction that occurs in eutherians is derived from an attachment reaction in the ancestral therian mammal which, in the opossum, leads directly to parturition. Finally, we argue that the ability to shift from an inflammatory attachment reaction to a noninflammatory period of pregnancy was a key innovation in eutherian mammals that allowed an extended period of intimate placentation.

Endometrial receptivity in the eutopic endometrium of women with endometriosis: it is affected, and let me show you why

The endometrium maintains complex controls on proliferation and apoptosis as part of repetitive menstrual cycles that prepare the endometrium for the window of implantation and pregnancy. The reliance on inflammatory mechanisms for both implantation and menstruation creates the opportunity in the setting of endometriosis for establishment of chronic inflammation that is disruptive to endometrial receptivity, causing both infertility and abnormal bleeding. Clinically, there can be little doubt that the endometrium of women with endometriosis is less receptive to embryo implantation, and strong evidence exists to suggest that endometrial changes are associated with decreased cycle fecundity as a result of this disease. Here we provide unifying concepts regarding those changes and how they are coordinated to promote progesterone resistance and estrogen dominance through aberrant cell signaling pathways and reduced expression of key homeostatic proteins in eutopic endometrium of women with endometriosis.

Tissue-Specific Ablation of the LIF Receptor in the Murine Uterine Epithelium Results in Implantation Failure

The cytokine leukemia inhibitory factor (LIF) is essential for rendering the uterus receptive for blastocyst implantation. In mice, LIF receptor expression (LIFR) is largely restricted to the uterine luminal epithelium (LE). LIF, secreted from the endometrial glands (GEs), binds to the LIFR, activating the Janus kinase-signal transducer and activation of transcription (STAT) 3 (Jak-Stat3) signaling pathway in the LE. JAK-STAT activation converts the LE to a receptive state so that juxtaposed blastocysts begin to implant. To specifically delete the LIFR in the LE, we derived a line of mice in which Cre recombinase was inserted into the endogenous lactoferrin gene (Ltf-Cre). Lactoferrin expression in the LE is induced by E2, and we demonstrate that Cre recombinase activity is restricted to the LE and GE. To determine the requirement of the LIFR in implantation, we derived an additional mouse line carrying a conditional (floxed) Lifrflx/flx gene. Crossing Ltf-Cre mice with Lifrflx/flx mice generated Lifrflx/Δ:LtfCre/+ females that were overtly normal but infertile. Many of these females, despite repeated matings, did not become pregnant. Unimplanted blastocysts were recovered from the Lifrflx/Δ:LtfCre/+ uteri and, when transferred to wild-type recipients, implanted normally, indicating that uterine receptivity rather than the embryo's competency is compromised. The loss of Lifr results in both the failure for STAT3 to translocate to the LE nuclei and a reduction in the expression of the LIF regulated gene Msx1 that regulates uterine receptivity. These results reveal that uterine expression of the LIFR is essential for embryo implantation and further define the components of the LIF signaling pathway necessary for effective implantation.

Immunohistochemical and ultrastructural analysis of the effect of omega-3 on embryonic implantation in an experimental mouse model

OBJECTIVE

Implantation is the first step to a healthy pregnancy. Omega-3 supplementation is common to use during pregnancy, for its antioxidant and membrane stabilising effect. In this study we have aimed to study the effect of Omega-3 supplementation on implantation in a mouse model by immunohistochemical methods and electron microscopic evaluation.

MATERIALS AND METHODS

Mice were randomized into three groups to receive standard food, Omega-3 400 mg/kg and Omega-3 1000 mg/kg one menstrual cycle before mating. Mice were sacrificed on third day of estimated implantation and uterine horns were evaluated immunohistochemically for staining of Laminin and Leukemia Inhibitory Factor (LIF) and ultrastructural morphology.

RESULTS

Laminin and LIF immunoreactivity were increased signifcantly in the high dose group when compared to the control and low-dose groups in lumen epithelium basal membrane, gland epithelium basal membrane and endometrial stroma. Electron-microscopic evaluation showed a decrease in epithelial height and microvilli loss in the high dose groups.

CONCLUSION

Omega-3 supplementation increased implantation markers Laminin and LIF and decreased epithelial height and microvilli thus seems to prepare the endometrium for a favorable environment of implantation.