Hormonal control of ovoimplantation

Transcriptomic changes in eutopic endometrium and ectopic lesions during endometriosis progression in a mouse model

OBJECTIVE

To identify the transcriptomic changes of ectopic lesions and eutopic endometrial tissues during the progression of endometriosis, we performed transcriptomic analysis in the eutopic endometrium and ectopic lesions.

DESIGN

Laboratory study.

SETTING

Academic medical center.

ANIMALS

Four fertile and 4 subfertile Pgrcre/+Rosa26mTmG/+ mice with endometriosis, and 4 sham mice for each group of endometriosis mice as control. These mice underwent either surgery to induce endometriosis or sham surgery. Fertile sham and mice with endometriosis were used 1 month after surgery, whereas subfertile ones were used 3 months after surgery.

INTERVENTIONS

Early and chronic effects of endometriosis on transcriptomics of ectopic lesions and eutopic endometrium.

MAIN OUTCOME MEASURES

RNA-sequencing analysis and identification of differentially expressed genes and pathways in the ectopic lesions and eutopic uteri from mice with endometriosis and sham mice at day 3.5 of pregnancy.

RESULTS

Our mouse model recapitulates the transcriptomic changes of ectopic lesions in humans. RNA-sequencing analysis was performed in ectopic lesions and eutopic uteri from mice with or without endometriosis during the progression of the disease. Estrogen activity, inflammation, angiogenesis, and fibrosis pathways were consistently elevated in all the ectopic lesions compared with eutopic endometrium. Cholesterol/glucose synthesis and stem cell pluripotency pathways were more enhanced in ectopic lesions from subfertile mice compared with their eutopic endometrium. Dysregulation of infiltration of macrophage, dendritic, T and B cells was validated with the use of immunohistochemistry in ectopic lesions. Multiple ligand-receptor pairs between the ectopic and eutopic endometrium were altered compared with the sham endometrium. Suppressed WNT and EGF pathways were only found in the eutopic endometrium from subfertile not fertile mice compared with sham.

CONCLUSIONS

Our mouse endometriosis model recapitulates the transcriptomics of ectopic lesions in humans. Our transcriptomic analysis during endometriosis progression in our mouse model will help us understand the pathophysiology of endometriosis.

A Potential Role of CD82/KAI1 during Uterine Decidualization in Mice

The tumor metastasis suppressor gene CD82/KAI1 has been demonstrated to impact human trophoblast invasion and migration. Communication between trophoblasts and decidual stromal cells plays a crucial role in controlling the normal invasiveness of trophoblasts. However, whether CD82/KAI1 is involved in decidualization and what role it plays remain unclear. CD82/KAI1 demonstrates specific spatiotemporal expression patterns in stromal cells undergoing decidualization during pregnancy. This is observed in both naturally pregnant females post-implantation and pseudopregnant mice undergoing induced decidualization, as detected through in situ hybridization and immunofluorescence. CD82/KAI1 expression showed a significant time-dependent increase in cultured stromal cells after 24 and 48 h of progesterone (P4) and estrogen (E2) treatment. This was accompanied by a notable upregulation of decidualization markers, including cyclin D3 and PR. After transducing stromal cells with the adenovirus-overexpressing CD82/KAI1 for 48 h, the expression of cyclin D3 protein increased. Meanwhile, there was an attenuated expression of CD82/KAI1 due to an adenovirus siRNA knockdown, whereas cyclin D3 and PR expressions were not affected. Our findings suggest a potential role of CD82/KAI1 in regulating the process of decidualization, providing insights into stromal cell differentiation.

Endometrial biopsy performed before the first in vitro fertilization does not impact the early pregnancy rate

Endometrial biopsy (EB) has been showed to increase the rate of clinical pregnancy in patients who underwent in vitro fertilization (IVF) failures. The purpose of this work was to assess the impact of an EB performed before the first in IVF on the early pregnancy rate. Be One study is a prospective, single-centre, randomized, open-label study. In this parallel study, patients were evenly split into two groups. In one group, patients underwent an EB between days 17 and 22 of the menstrual cycle that precedes the ovarian stimulation. In the other group (control), no EB was performed. The hCG-positive rate (early pregnancy rate) was evaluated on day 14 after the ovarian puncture. In total, 157 patients were randomized in the EB group and 154 patients were in the control group. The early pregnancy rate was 33.1% (52/157) in the EB group and 29.9% (46/154) in the control group (p = 0.54). Other parameters, including perforation, endometritis, or pain level were reassuring. An EB performed during the luteal phase of the menstrual cycle preceding the stimulation of the first IVF did not increase early pregnancy rate.

Yueliang Yin Ameliorates Endometrial Receptivity in Mice with Embryo Implantation Failure by Reducing Pyroptosis and Activating BDNF/TrkB Pathway

SCOPE

Endometrial receptivity plays a vital role in embryonic implantation. Yueliang Yin is a marketed solid drink in China, also known as Bushen Cuyun Recipe (BCR), that is, assumed to have a therapeutic effect on infertility by improving endometrial receptivity. This study investigates the effects and mechanisms of BCR in protecting the endometrium.

METHODS AND RESULTS

Mice with mifepristone-induced embryo implantation failure that exhibited a decreased implantation sites number, thinner endometrium, reduced endometrial glands number, and poor pinopode expression levels are treated with BCR, and these mentioned conditions significantly improves afterward. Molecular docking shows that the main active components kaempferol, quercetin, and hesperetin of BCR stably bound to gasdermin D (GSDMD). Experimental results demonstrate that levels of GSDMD, cleaved caspase-1 and leucine-rich repeat, and pyrin domain-containing 3 and IL-1β levels in model mice are significantly decreased and expressions of brain-derived neurotrophic factor (BDNF) and tyrosine protein kinase B (TrkB) expression levels are significantly elevated after BCR treatments, and that the DNA damage is significantly reversed in BCR-treated mice.

CONCLUSIONS

BCR is potent and effective in ameliorating endometrial receptivity. The potential mechanisms of BCR on endometrial receptivity may mediate by activating BDNF/TrkB pathway activation and protecting endometrial cells' protection against pyroptosis.

Endometrial Receptivity During the Preimplantation Period: A Narrative Review

Endometrial receptivity is a complex and critical process fundamental to achieving a successful pregnancy. While researchers have made significant strides in understanding the underlying mechanisms governing endometrial receptivity, effective diagnostic and therapeutic strategies remain scarce. This review article aims to elucidate the various factors that contribute to endometrial receptivity, including the hormonal regulation and molecular mechanisms that govern this process, as well as potential biomarkers for assessing endometrial receptivity. One of the major challenges in identifying reliable biomarkers for endometrial receptivity is the intricate nature of the process itself. Nonetheless, recent advances in transcriptomic and proteomic technologies have identified several candidate biomarkers that could potentially enhance our ability to predict endometrial receptivity. Furthermore, emerging technologies such as single-cell RNA sequencing and mass spectrometry-based proteomics hold great promise for providing novel insights into the molecular mechanisms underlying endometrial receptivity. Despite the lack of reliable biomarkers, various therapeutic strategies have been proposed to improve endometrial receptivity. One promising approach involves the transplantation of mesenchymal stem cells (MSCs), which have been shown to increase endometrial thickness and receptivity in both animal models and clinical trials. Growth factors, cytokines, and exosomes derived from MSCs and other cell types may also have therapeutic potential for addressing endometrial dysfunction.

Pre-implantation mouse embryo movement under hormonally altered conditions

Pre-implantation embryo movement is crucial to pregnancy success, but the role of ovarian hormones in modulating embryo movement is not understood. We ascertain the effects of altered hormonal environment on embryo location using two delayed implantation mouse models: natural lactational diapause (ND); and artificially induced diapause (AD), a laboratory version of ND generated by ovary removal and provision of supplemental progesterone (P4). Previously, we showed that embryos in a natural pregnancy (NP) first display unidirectional clustered movement, followed by bidirectional scattering and spacing movement. In the ND model, we discovered that embryos are present as clusters near the oviductal-uterine junction for ∼24 h longer than NP, followed by locations consistent with a unidirectional scattering and spacing movement. Intriguingly, the AD model resembles embryo location in NP and not ND. When measuring serum hormone levels, unlike the popular paradigm of reduced estrogen (E2) levels in diapause, we observed that E2 levels are comparable across NP, ND and AD. P4 levels are reduced in ND and highly increased in AD when compared to NP. Further, exogenous administration of E2 or P4 modifies embryo location during the unidirectional phase, while E2 treatment also affects embryo location in the bidirectional phase. Taken together, our data suggest that embryo movement can be modulated by both P4 and E2. Understanding natural hormonal adaptation in diapause provides an opportunity to determine key players that regulate embryo location, thus impacting implantation success. This knowledge can be leveraged to understand pregnancy survival and implantation success in hormonally altered conditions in the clinic.

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.

New Roles for EVs, miRNA and lncRNA in Bovine Embryo Implantation

The sine qua non of new life is fertilization. However, approximately 50% of fertilized eggs/blastocysts in cattle and up to 75% of those from human assisted reproductive procedures fail during the first 3 to 4 weeks of pregnancy, including peri-implantation periods. In these periods, blastocyst hatching and implantation to the maternal endometrium proceeds, during which physiological events such as epithelial-mesenchymal transition (EMT) and trophoblast cell fusion occur. Quite recently, extracellular vesicles (EVs) with micro RNAs (miRNAs) and long non-coding RNAs (lncRNAs) have been found to play a pivotal role for the establishment of the proper uterine environment required for peri-implantation processes to proceed. New findings of EVs, miRNA, and lncRNAs will be described and discussed to elucidate their connections with conceptus implantation to the maternal endometrium.

Podocalyxin molecular characteristics and endometrial expression: high conservation between humans and macaques but divergence in mice†

Podocalyxin (PODXL) is a newly identified key negative regulator of human endometrial receptivity, specifically down-regulated in the luminal epithelium at receptivity to permit embryo implantation. Here, we bioinformatically compared the molecular characteristics of PODXL among the human, rhesus macaque and mouse, determined by immunohistochemistry and in situ hybridization (mouse tissues) whether endometrial PODXL expression is conserved across the three species, and examined if PODXL inhibits mouse embryo attachment in vitro. The PODXL gene, mRNA and protein sequences showed greater similarities between humans and macaques than with mice. In all species, PODXL was expressed in endometrial luminal/glandular epithelia and endothelia. In macaques (n = 9), luminal PODXL was significantly down-regulated when receptivity is developed, consistent with the pattern found in women. At receptivity PODXL was also reduced in shallow glands, whereas endothelial expression was unchanged across the menstrual cycle. In mice, endometrial PODXL did not vary considerably across the estrous cycle (n = 16); however, around embryo attachment on d4.5 of pregnancy (n = 4), luminal PODXL was greatly reduced especially near the site of embryo attachment. Mouse embryos failed to attach or thrive when co-cultured on a monolayer of Ishikawa cells overexpressing PODXL. Thus, endometrial luminal PODXL expression is down-regulated for embryo implantation in all species examined, and PODXL inhibits mouse embryo implantation. Rhesus macaques share greater conservations with humans than mice in PODXL molecular characteristics and regulation, thus represent a better animal model for functional studies of endometrial PODXL for treatment of human fertility.

Use of 'omics for endometrial timing: the cycle moves on

For some years, the prospect of precise and personalized timing of the endometrial cycle for optimal embryo replacement has been held out as a potential solution to low implantation rates. It is envisaged that a receptive state can be defined and reached at a predictable time, and embryo replacement performed in synchrony. In the last century, morphological changes characteristic of the mid secretory phase were defined in precisely timed cycles in women of proven fertility, but when deviations from this standardized schedule occur, their significance for implantation has remained uncertain. ‘Omics technologies have been widely advocated for staging the endometrial cycle and defining a set of biochemical requirements for implantation, but after two decades of research, improvements to pregnancy rates have not followed, and there is a striking lack of agreement regarding the molecular characterization of the receptive state. Some of the rationale underlying these problems is now emerging with the application of higher-level computational and biological methodology. Here, we consider the challenges of defining an endometrial phenotype that can support implantation and continuing pregnancy. Receptivity may be an emergent trait depending on contributions from multiple proteins that have low pathway connectivity. We recommend that authors choose language which rigorously avoids the implication that protocols for molecular staging of the mid secretory phase inherently identify a state of receptivity to the implanting blastocyst.

Kruppel-like factor 5 (Klf5) in fetal-maternal tissue during periimplantation and effects of ovarian steroid hormone antagonist on its expression during uterine receptivity of albino mice

Background

Embryo implantation is a tightly regulated sequence of events regulated by ovarian steroids, estrogen and progesterone, and their downstream targets. Ovarian steroids regulate most of the genes involved in embryo implantation and pregnancy. However, some factors are not regulated by ovarian steroids, estrogen, progesterone, or both. Kruppel-like factor 5 (Klf5) is an example of an ovarian steroid–independent factor having a role in cellular proliferation, differentiation. The detailed expression profile of Klf5 during uterine receptivity and periimplantation has not been studied till now. In the present research work, an attempt was made to investigate the expression pattern of Klf5 in mice fetal-maternal tissue during periimplantation (day 4–day 8). The expressional and functional independence of Klf5 on the ovarian steroids was studied using estrogen and progesterone antagonist. The study was carried out in female Swiss albino mice of LACA strain during the periimplantation period. KLF5 was localized in the fetal-maternal tissues using the immunofluorescence technique in paraffin-embedded tissues. Ovarian steroid antagonists were administered subcutaneously from day 1 to day 3 of gestation, and the uterus was collected on the morning of day 4. Klf5 protein and mRNA levels were studied by western blot and quantitative real-time PCR (qPCR), respectively.

Results

KLF5 was localized in the embryo, uterine luminal epithelium, glandular epithelium, and proliferating stromal cells during periimplantation. In ovarian steroid antagonist–treated groups, KLF5 was localized in the luminal and glandular epithelium and stroma. Western blot and qPCR confirmed translation and transcription of KLF5 during the experimental period. The KLF5 protein level significantly increased on day 6, day 7, and day 8 when compared with day 4 (P < 0.05). The mRNA level of Klf5 increased significantly on day 7 and day 8 when compared with day 4 (P < 0.05). In ovarian steroid antagonist–treated groups, protein and mRNA corresponding to Klf5 were observed. From this finding, it can be assumed that Klf5 may be a steroid-independent factor expressed during uterine receptivity.

Conclusion

Spatiotemporal KLF5 expression in fetal-maternal tissue was observed during the experimental period. The results suggest that Klf5 is an ovarian steroid–independent factor that may play a pivotal role in implantation, decidualization, and embryogenesis.

Ovarian Folliculogenesis and Uterine Endometrial Receptivity after Intermittent Vaginal Injection of Recombinant Human Follicle-Stimulating Hormone in Infertile Women Receiving In Vitro Fertilization and in Immature Female Rats

The uterine first-pass effect occurs when drugs are delivered vaginally. However, the effect of vaginally administered recombinant human follicle-stimulating hormone (rhFSH) on ovarian folliculogenesis and endometrial receptivity is not well established. We aimed to compare the efficacy of rhFSH administered vaginally and abdominally in clinical in vitro fertilization (IVF) treatment, pharmacokinetic study, and animal study. In IVF treatment, the number of oocytes retrieved, endometrial thickness and uterine artery blood perfusion were not different between women who received the rhFSH either vaginally or abdominally. For serum pharmacokinetic parameters, significantly lower Tmax, clearance, and higher AUC and T_1/2_elimination of rhFSH were observed in women who received rhFSH vaginally, but urine parameters were not different. Immature female rats that received daily abdominal or vaginal injections (1 IU twice daily for 4 days) or intermittent vaginal injections (4 IU every other day for two doses) of rhFSH had more total follicles than the control group. In addition, the serum progesterone and progesterone receptors in the local endometrium were significantly higher in the groups treated with intermittent abdominal or vaginal injection of rhFSH, compared with those who recieved daily injection. In summary, vaginal administration of rhFSH may provide an alternative treatment regimen in women receiving IVF.

The effect of LH rise during artificial frozen-thawed embryo transfer (FET) cycles

PURPOSE

To evaluate the association between a rise in serum luteinizing hormone (LH) levels during artificial frozen-thawed embryo transfer (FET) cycles and clinical pregnancy rate.

METHODS

A retrospective cohort study of women undergoing artificial FET cycles. We compared cycles in which LH double itself from the early follicular phase and further (group A) to cycles without a rise in LH (group B). Endometrium preparation was achieved by administration of 2 mg three times per day estradiol valerate tablets. Embryo transfer (ET) was conducted after achieving endometrial thickness > 7 mm and vaginal progesterone was added according to the embryo's age. A beta-hCG was measured 13-14 days after ET. Clinical pregnancy was diagnosed on transvaginal ultrasound.

RESULTS

Data from 984-FET cycles were retrieved. LH, exogenous estradiol (E2), progesterone values, endometrial thickness, and pregnancy outcomes were available in all patients. From 984-FET cycles, 629 (63.9%) had a doubling, and 355 (36.07%) had no rise in LH. Patients mean age was 30 years, similar in both groups. A multivariable logistic regression analysis was calculated to assess the effect of LH rise and pregnancy outcomes, after adjusting for confounders including a rise in E2 level and endometrial thickness. In this model, there was no association between doubling LH values and pregnancy rates (adjusted odds ratio: 1.06, 95% CI: 0.75-1.5, P = 0.74).

CONCLUSION

LH rise during artificial FET cycles does not alter pregnancy rates. Apparently, hormonal monitoring of LH levels may not yield useful information in the artificial FET cycle and may be omitted.

LAY SUMMARY

Supplementation of estradiol, a hormone produced by the ovaries, starting at the beginning of the menstrual cycle of an artificially frozen embryo transfer (FET) can lead to a rise in luteinizing hormone (LH), the hormone that induces ovulation. Such a rise in LH may interfere with embryo implantation, the process where the embryo attaches to the inner lining of the uterus and, therefore, could affect the chances of pregnancy. The current study is the first to assess the effect of a dynamic rise in LH levels during FET cycles on pregnancy rates. This study found no difference in pregnancy rates between FET cycles where the LH doubled compared to cycles without such a rise in LH. Larger, prospective studies should be conducted to assess the impact of LH elevation on pregnancy outcomes.

Transcriptomic analysis and competing endogenous RNA network in the human endometrium between proliferative and mid-secretory phases

Successful embryo implantation is the first step for establishing natural pregnancy and is dependent on the crosstalk between the embryo and a receptive endometrium. However, the molecular signaling events for successful embryo implantation are not entirely understood. To identify differentially expressed transcripts [long-noncoding RNAs (lncRNAs), microRNAs (miRNAs) and mRNAs] and competing endogenous RNA (ceRNA) networks associated with endometrial receptivity, the current study analyzed gene expression profiles between proliferative and mid-secretory endometria in fertile women. A total of 247 lncRNAs, 67 miRNAs and 2,154 mRNAs were identified as differentially expressed between proliferative and mid-secretory endometria. Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that these differentially expressed genes were significantly enriched for 'cell adhesion molecules.' Additionally, 98 common mRNAs were significantly involved in tryptophan metabolism, metabolic pathways and FoxO signaling. From the differentially expressed lncRNA/miRNA/mRNA ceRNA network, hub RNAs that formed three axes were identified: The DLX6-AS1/miR-141 or miR-200a/OLFM1 axis, the WDFY3-AS2/miR-135a or miR-183/STC1 axis, and the LINC00240/miR-182/NDRG1 axis. These may serve important roles in the regulation of endometrial receptivity. The hub network of the current study may be developed as a candidate marker for endometrial receptivity.

CXCL12 enhances pregnancy outcome via improvement of endometrial receptivity in mice

Successful pregnancy inevitably depends on the implantation of a competent embryo into a receptive endometrium. Although many substances have been suggested to improve the rate of embryo implantation targeting enhancement of endometrial receptivity, currently there rarely are effective evidence-based treatments to prevent or cure this condition. Here we strongly suggest minimally-invasive intra-uterine administration of embryo-secreted chemokine CXCL12 as an effective therapeutic intervention. Chemokine CXCL12 derived from pre- and peri-implanting embryos significantly enhances the rates of embryo attachment and promoted endothelial vessel formation and sprouting in vitro. Consistently, intra-uterine CXCL12 administration in C57BL/6 mice improved endometrial receptivity showing increased integrin β3 and its ligand osteopontin, and induced endometrial angiogenesis displaying increased numbers of vessel formation near the lining of endometrial epithelial layer with higher CD31 and CD34 expression. Furthermore, intra-uterine CXCL12 application dramatically promoted the rates of embryo implantation with no morphologically retarded embryos. Thus, our present study provides a novel evidence that improved uterine endometrial receptivity and enhanced angiogenesis induced by embryo-derived chemokine CXCL12 may aid to develop a minimally-invasive therapeutic strategy for clinical treatment or supplement for the patients with repeated implantation failure with less risk.

Non-invasive Intrauterine Administration of Botulinum Toxin A Enhances Endometrial Angiogenesis and Improves the Rates of Embryo Implantation

Endometrial angiogenesis plays crucial roles in determining the endometrial receptivity. Defects in endometrial receptivity often cause repeated implantation failure, which is one of the major unmet needs for infertility and contributes a major barrier to the assisted reproductive technology. Despite the numerous extensive research work, there are currently no effective evidence-based treatments to prevent or cure this condition. As a non-invasive treatment strategy, botulinum toxin A (BoTA) was administered into one side of mouse uterine horns, and saline was infused into the other side of horns for the control. Impact of BoTA was assessed in the endometrium at 3 or 8 days after infusion. We demonstrated that BoTA administration enhances the capacity of endothelial cell tube formation and sprouting. The intrauterine BoTA administration significantly induced endometrial angiogenesis displaying increased numbers of vessel formation and expression levels of related marker genes. Moreover, BoTA intrauterine application promoted the endometrial receptivity, and the rates of embryo implantation were improved with BoTA treatment with no morphologically retarded embryos. Intrauterine BoTA treatment has a beneficial effect on vascular reconstruction of functional endometrium prior to embryo implantation by increasing endometrial blood flow near the uterine cavity suggesting BoTA treatment as a potential therapeutic strategy for patients who are suffering from repeated implantation failure with the problems with endometrial receptivity.

Preparation of Fibroblast Suppressive Poly(ethylene glycol)-b-poly(l-phenylalanine)/Poly(ethylene glycol) Hydrogel and Its Application in Intrauterine Fibrosis Prevention

Intrauterine adhesions (IUA) often occur as a result of trauma to the basal layer after curettage, postpartum hemorrhage, or surgical miscarriage. Endometrial fibrosis is the primary pathological feature of IUA. The characteristic features of IUA include excessive deposition and reorganization of the extracellular matrix, replacing the normal endometrium. To prevent uterine fibrosis after injury, we prepared and evaluated a type of fibroblast suppressive hydrogel. Poly(ethylene glycol)-b-poly(l-phenylalanine) (PEBP) copolymers were successfully synthesized by ring opening polymerization of l-Phenylalanine N-carboxyanhydride, initiated by methoxy-poly(ethylene glycol)-amine. Injectable PEBP/PEG hydrogels were subsequently formed through π-π accumulations between PEBP macromolecules and hydrogen bonds among PEBP, PEG, and H₂O molecules. PEBP/PEG hydrogel could suppress the proliferation of fibroblasts due to the action of l-Phe, released sustainably from PEBP/PEG gels. Lastly, the in vivo preventive effect of PEBP/PEG hydrogel on fibrosis was evaluated in a rat uterine curettage model. It was found that PEBP/PEG hydrogel suppressed uterine fibrosis caused by curettage and promoted embryo implantation in injured uterine by regulating the expression and interactions of transforming growth factor beta 1 (TGF-β1) and Muc-4. PEBP/PEG hydrogels have the potential for application in uterine adhesion prevention owing to their fibrosis preventive and pregnancy promotiing effects on uterine tissue after injury.

Pleiotropic role of prokineticin 1 in the porcine endometrium during pregnancy establishment and embryo implantation †

Acquisition of endometrial receptivity for embryo implantation is one of the crucial processes during pregnancy and is induced mainly by progesterone and enhanced by conceptus signals. Prokineticin 1 (PROK1) is characterized as a secretory protein with diverse functions in various tissues, including the reproductive tract. PROK1, with its receptor PROKR1, are up-regulated in the porcine endometrium during implantation and in women's receptive endometrium and decidua. However, the function of PROK1 in embryo-maternal communication has still not been fully elucidated. Hence, we hypothesize that PROK1 is involved in endometrial receptivity development and implantation in pigs. In this study, using the porcine in vivo model of intrauterine infusions of estradiol-17β (E2) and prostaglandin E2 (PGE2), we revealed that these hormones elevated endometrial expression of PROK1 and PROKR1 mRNA, respectively. Moreover, E2, acting synergistically with PGE2, increased PROKR1 protein expression. We also evidenced that PROK1-PROKR1 signaling induced expression of following genes and/or proteins CCN2, CDH13, FGF2, NFATC2, ANGPT1, ANGPT2, CDH1, MUC4, SPP1, IFNG, IL6, LIF, LIFR, TNF, TGFB3, and FGF9, as well as phosphorylation of PTK2 and secretion of IL6 and IL11 by endometrial explants in vitro. Ingenuity pathway analysis revealed that functions associated with the PROK1-regulated genes/proteins include cell-to-cell contact, cell attachment, migration and viability, differentiation of epithelial tissue, leukocyte migration, inflammatory response, angiogenesis, and vasculogenesis. Summarizing, our study suggests that PROK1 acts pleiotropically as an embryonic signal mediator that regulates endometrial receptivity by increasing the expression of the genes and proteins involved in implantation and pregnancy establishment in pigs.

Emerging Role of Extracellular Vesicles in Embryo-Maternal Communication throughout Implantation Processes

In ruminants, the establishment of proper conceptus–endometrial communication is essential for conceptus implantation and subsequent successful placentation. Accumulated evidence supports the idea that extracellular vesicles (EVs) present in uterine lumen are involved in conceptus–endometrial interactions during the preimplantation period. EVs make up a new field of intercellular communicators, which transport a variety of bioactive molecules, including soluble and membrane-bound proteins, lipids, DNA, and RNAs. EVs thus regulate gene expression and elicit biological effects including increased cell proliferation, migration, and adhesion in recipient cells. Uterine EVs are interactive and coordinate with ovarian progesterone (P4), trophectoderm-derived interferon tau (IFNT) and/or prostaglandins (PGs) in the physiological or pathological microenvironment. In this review, we will focus on intrauterine EVs in embryo–maternal interactions during the early stage of pregnancy, especially the implantation period in ruminant ungulates.

90 YEARS OF PROGESTERONE: New insights into progesterone receptor signaling in the endometrium required for embryo implantation

Progesterone's ability to maintain pregnancy in eutherian mammals highlighted this steroid as the 'hormone of pregnancy'. It was the unique 'pro-gestational' bioactivity of progesterone that enabled eventual purification of this ovarian steroid to crystalline form by Willard Myron Allen in the early 1930s. While a functional connection between normal progesterone responses ('progestational proliferation') of the uterus with the maintenance of pregnancy was quickly appreciated, an understanding of progesterone's involvement in the early stages of pregnancy establishment was comparatively less well understood. With the aforementioned as historical backdrop, this review focuses on a selection of key advances in our understanding of the molecular mechanisms by which progesterone, through its nuclear receptor (the progesterone receptor), drives the development of endometrial receptivity, a transient uterine state that allows for embryo implantation and the establishment of pregnancy. Highlighted in this review are the significant contributions of advanced mouse engineering and genome-wide transcriptomic and cistromic analytics which reveal the pivotal molecular mediators and modifiers that are essential to progesterone-dependent endometrial receptivity and decidualization. With a clearer understanding of the molecular landscape that underpins uterine responsiveness to progesterone during the periimplantation period, we predict that common gynecologic morbidities due to abnormal progesterone responsiveness will be more effectively diagnosed and/or treated in the future.

The ART of frozen embryo transfer: back to nature!

The implementation of cryopreservation-techniques in the IVF laboratory and the improved survival rates of oocytes, cleavage and blastocyst stage embryos have led to a significant increase in the number of frozen-thawed embryo transfer cycles (FET). FETs can be planned either in a 'pure' natural cycle, a modified natural cycle, a stimulated cycle or a hormonal replacement therapy cycle and the optimal means to prepare the endometrium for frozen embryo transfer is a topic of ongoing controversy. Recent findings report an increased risk of hypertensive disorders if pregnancy is achieved in a frozen embryo transfer cycle without an existing corpus luteum. Therefore, the question of how to prepare the endometrium has gained even more importance and taken on a new dimension as it should not simply be reduced to the basic question of 'which approach will result in superior pregnancy rates?' but instead 'which approach will result in the best pregnancy rates and the safest outcome for mother and baby?'. The aim of this review is to summarize and critically appraise the existing data on the different approaches of endometrial preparation for frozen embryo transfer with a special focus on the 'pure' natural cycle.

Endometrial profilin 1: a key player in embryo-endometrial crosstalk

Objective

Despite extensive research on implantation failure, little is known about the molecular mechanisms underlying the crosstalk between the embryo and the maternal endometrium, which is critical for successful pregnancy. Profilin 1 (PFN1), which is expressed both in the embryo and in the endometrial epithelium, acts as a potent regulator of actin polymerization and the cytoskeletal network. In this study, we identified the specific role of endometrial PFN1 during embryo implantation.

Methods

Morphological alterations depending on the status of PFN1 expression were assessed in PFN1-depleted or control cells grown on Matrigel-coated cover glass. Day-5 mouse embryos were cocultured with Ishikawa cells. Comparisons of the rates of F-actin formation and embryo attachment were performed by measuring the stability of the attached embryo onto PFN1-depleted or control cells.

Results

Depletion of PFN1 in endometrial epithelial cells induced a significant reduction in cell-cell adhesion displaying less formation of colonies and a more circular cell shape. Mouse embryos co-cultured with PFN1-depleted cells failed to form actin cytoskeletal networks, whereas more F-actin formation in the direction of surrounding PFN1-intact endometrial epithelial cells was detected. Furthermore, significantly lower embryo attachment stability was observed in PFN1-depleted cells than in control cells. This may have been due to reduced endometrial receptivity caused by impaired actin cytoskeletal networks associated with PFN1 deficiency.

Conclusion

These observations definitively demonstrate an important role of PFN1 in mediating cell-cell adhesion during the initial stage of embryo implantation and suggest a potential therapeutic target or novel biomarker for patients suffering from implantation failure.

Early Progesterone Change Associated With Pregnancy Outcome After Fresh Embryo Transfer in Assisted Reproduction Technology Cycles With Progesterone Level of >1.5 ng/ml on Human Chorionic Gonadotropin Trigger Day

Several studies have reported a poor implantation rate for assisted reproduction technology (ART) cycles with elevated progesterone (P4) at the end of the follicular phase. Whether all women with increased P4 on the human chorionic gonadotropin(hCG) trigger day should undergo fresh or frozen embryo transfer (ET) remains to be explored. This study attempted to determine that the P4 level on 2 days before hCG administration and P4 ratio can serve as indicators for fresh ET in normal responders with an elevated P4 level of >1.5 ng/ml on the hCG administration day. This was a retrospective cohort study involving 337 ART cycles with fresh ET for normal responders. Serum P4 levels were measured 2 days prior to hCG day (P4 level I) and on the hCG administration day (P4 level II). The P4 ratio was calculated as follows: P4 ratio = P4 level II / P4 level I. The primary outcome is live birth rate of fresh ET cycles. The ROC curves established that the optimal P4 level I and P4 ratio for pregnancy in ART cycles with high P4 level II were 0.975 ng/ml and 1.62, respectively. Patients with a P4 level I of ≤0.975 ng/ml and P4 ratio of >1.62 were associated with a significantly higher implantation (30.8%, 61/198 vs. 10.3%, 19/184, p < 0.001) and live birth rates (51.6%, 33/64 vs. 15.0%, 9/60, p < 0.001) compared with those with a P4 level I of >0.975 ng/ml and P4 ratio of ≤1.62. A combination of P4 level I and P4 ratio cutoff values of 0.975 ng/ml and 1.62, respectively, had a positive predictive value (PPV) of 82.5% for pregnancy. In conclusion, fresh ET can be an option for women with an early P4 level I under 0.975 ng/ml and a P4 ratio higher than 1.62, especially for those normal responders with an elevated P4 level II >1.5 ng/ml on the hCG administration day. This approach may shorten the time to pregnancy and reduce the cost of ART cycles.

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.

Pregnancy rates from natural and artificial cycles of women submitted to frozen embryo transfers: a metanalysis

Objective:

To compare pregnancy rates from natural and artificial cycles of women submitted to frozen embryo transfers.

Methods:

A systematic review was performed by PubMed search using the following algorithm: (endometrial [All Fields] AND preparation [All Fields]) AND (("freezing"[MeSH Terms] OR "freezing"[All Fields] OR "frozen"[All Fields]) AND thawed [All Fields]) and (natural cycles) AND (artificial cycle). Inclusion criteria: prospective and retrospective cohort studies. Exclusion criteria: use of hCG in the natural cycle, oocyte donors, and use of disused freezing techniques. Data were analyzed with the SPSS v.23 software and with a significance level of 5%. The meta-analysis was performed with RevMan 5.3 software. I² was calculated.

Results:

709 papers were retrieved. Five studies fulfilled the inclusion and exclusion criteria. From these studies, we analyzed 8,968 natural or artificial cycles. A contingency table compared the results of the natural and artificial cycles and the number of clinical pregnancies obtained in each selected paper. The I² test resulted in high statistical heterogeneity (I²=77%). Studies by Morozov et al. (2007) and Zheng et al. (2015) obtained statistically significant results (p<0.03 and p<0.001): Morozov et al. (2007) found a higher pregnancy rate within natural cycles, and Zheng et al. (2015) found more positive outcomes when analyzing artificial cycles. The remaining selected studies did not show any statistical significance.

Conclusion

There is insufficient scientific evidence to state that the artificial cycle yields better pregnancy rates than the natural cycle in women submitted to frozen embryo transfer. Limitations of this study include a small number of papers and heterogeneity among the studies.

miR-29c overexpression and COL4A1 downregulation in infertile human endometrium reduces endometrial epithelial cell adhesive capacity in vitro implying roles in receptivity

The endometrium is a highly complex tissue that is vulnerable to subtle gene expression changes and is the first point of contact for an implanting blastocyst. Successful blastocyst implantation can only occur when the endometrium is receptive during a short window with each menstrual cycle. microRNAs are small, non-coding RNAs that negatively regulate their gene targets. miR-29c has previously been identified to be differentially regulated across the fertile menstrual cycle, however it has not been investigated in association with infertility. We hypothesised that miR-29c dysregulation in the infertile endometrium would negatively influence endometrial adhesion and blastocyst implantation outcomes during the mid-secretory, receptive phase. miR-29c expression was elevated in early and mid-secretory phase infertile endometrium and localised to the epithelial compartments of endometrial tissue. Overexpression of miR-29c in vitro impaired endometrial epithelial adhesion, and reduced collagen type IV alpha 1 (COL4A1) mRNA expression. COL4A1 was immunolocalised to the luminal and glandular epithelial basement membranes in early and mid-secretory phase fertile and infertile endometrium for the first time. Knockdown of COL4A1 impaired endometrial epithelial adhesion suggesting a role in endometrial receptivity and implantation. Our data suggests miR-29c overexpression with infertility may impair the adhesive capacity of the endometrium, potentially contributing to implantation failure and infertility.

Distinct dormancy progression depending on embryonic regions during mouse embryonic diapause†

Many mammalian species undergo embryonic diapause and suspend development at the blastocyst stage before implantation, which is also known as delayed implantation. We studied the process of how mouse embryos enter a dormancy status at a cellular level. Immunofluorescent analysis of differentiation markers for epiblast, primitive endoderm, and trophectoderm suggested that cell differentiation status was maintained during 7 days in diapause. To understand the progression of cellular dormancy during diapause, we examined the expression of a transgenic cell cycle marker Fucci2 and Ki67 by antibody staining, in addition to direct counting of nuclei in embryos. From these analyses, embryos during diapause were categorized into four stages by cell number and cell cycle. Cell cycle arrest occurred from the ab-embryonic region and from the trophectoderm to the ICM in the embryonic side. We also observed cell cycle transition by live imaging of Fucci2 embryos during the reactivation in culture from dormant status. Cell cycle was initially recovered from the embryonic side of embryos and eventually spread throughout the whole embryo. We also found that embryos in later stages of diapause required a longer period of time for reactivation. From these observations, it was shown that entrance into and exit from dormant status varied depending on cell types and location of cells in an embryo. These results suggest that embryonic diapause includes multiple steps and the mechanisms involved in cellular dormancy may be distinct between embryonic regions.

Molecular mechanisms of embryonic implantation in mammals: Lessons from the gene manipulation of mice

BACKGROUND

Human infertility has become a serious and social issue all over the world, especially in developed countries. Numerous types of assisted reproductive technology have been developed and are widely used to treat infertility. However, pregnancy outcomes require further improvement. It is essential to understand the cross-talk between the uterus (mother) and the embryo (fetus) in pregnancy, which is a very complicated event.

METHODS

The mammalian uterus requires many physiological and morphological changes for pregnancy-associated events, including implantation, decidualization, placentation, and parturition, to occur. Here is discussed recent advances in the knowledge of the molecular mechanisms underlying these reproductive events - in particular, embryonic implantation and decidualization - based on original and review articles.

MAIN FINDINGS RESULTS

In mice, embryonic implantation and decidualization are regulated by two steroid hormones: estrogen and progesterone. Along with these hormones, cytokines, cell-cycle regulators, growth factors, and transcription factors have essential roles in implantation and decidualization in mice.

CONCLUSION

Recent studies using the gene manipulation of mice have given considerable insight into the molecular mechanisms underlying embryonic implantation and decidualization. However, as most of the findings are based on mice, comparative research using different mammalian species will be useful for a better understanding of the species-dependent differences that are associated with reproductive events, including embryonic implantation.

Prominin-1 glycosylation changes throughout early pregnancy in uterine epithelial cells under the influence of maternal ovarian hormones

In preparation for uterine receptivity, the uterine epithelial cells (UECs) exhibit a loss of microvilli and glycocalyx and a restructuring of the actin cytoskeleton. The prominin-1 protein contains large, heavily glycosylated extracellular loops and is usually restricted to apical plasma membrane (APM) protrusions. The present study examined rat UECs during early pregnancy using immunofluorescence, western blotting and deglycosylation analyses. Ovariectomised rats were injected with oestrogen and progesterone to examine how these hormones affect prominin-1. At the time of fertilisation, prominin-1 was located diffusely in the apical domain of UECs and 147- and 120-kDa glycoforms of prominin-1 were identified, along with the 97-kDa core protein. At the time of implantation, prominin-1 concentrates towards the APM and densitometry revealed that the 120-kDa glycoform decreased (P<0.05), but there was an increase in the 97-kDa core protein (P<0.05). Progesterone treatment of ovariectomised rats resulted in prominin-1 becoming concentrated towards the APM. The 120-kDa glycoform was increased after oestrogen treatment (P<0.0001), whereas the 97-kDa core protein was increased after progesterone treatment (P<0.05). Endoglycosidase H analysis demonstrated that the 120-kDa glycoform is in the endoplasmic reticulum, undergoing protein synthesis. These results indicate that oestrogen stimulates prominin-1 production, whereas progesterone stimulates the deglycosylation and concentration of prominin-1 to the apical region of the UECs. This likely presents the deglycosylated extracellular loops of prominin-1 to the extracellular space, where they may interact with the implanting blastocyst.

High Level of APOA1 in Blood and Maternal Fetal Interface Is Associated With Early Miscarriage

Early miscarriage (EM) is one of the most devastating obstetrical complications globally affecting the quality of women's life. In the present study, we aimed to identify proteins that correlate with and could act as biomarkers for EM. We performed 2-dimensional gel electrophoresis in chorionic villi samples followed by mass spectrometry for identification of differential protein expression with EM. Proteomic studies detected a total 124 protein spots, out of which 83 spots were differentially expressed between EM and controls in chorionic villi samples. Matrix assisted laser desorbtion/ionization-time of flight (MALDI-TOF) mass spectrometry analysis revealed Apolipoprotein A1 (APOA1) to be the most upregulated protein in the EM group that was validated by Western blotting and Enzyme-linked immunosorbent assay (ELISA) . We found low but not statistically significant level of APOA1 on 21st day of menstruation in comparison to the 7th day. APOA1 level was observed to be the lowest in the first trimester. Hence, this study suggests that low APOA1 expression is critical in establishing pregnancy and elevated APOA1 expression in chorionic villi correlates with EM. Similar observation in serum samples suggests its potential as a marker for the risk of EM.

Soluble Delta-like ligand 1 alters human endometrial epithelial cell adhesive capacity

The endometrium undergoes substantial morphological and functional changes to become receptive to embryo implantation and to enable establishment of a successful pregnancy. Reduced Delta-like ligand 1 (DLL1, Notch ligand) in the endometrium is associated with infertility. DLL1 can be cleaved by 'a disintegrin and metalloprotease' (ADAM) proteases to produce a soluble ligand that may act to inhibit Notch signalling. We used an enzyme-linked immunosorbent assay to quantify soluble DLL1 in uterine lavages from fertile and infertile women in the secretory phase of the menstrual cycle. We also determined the cellular location and immunostaining intensity of ADAM12 and 17 in human endometrium throughout the cycle. Functional effects of soluble DLL1 in receptivity were analysed using in vitro adhesion and proliferation assays and gene expression analysis of Notch signalling targets. Soluble DLL1 was significantly increased in uterine lavage samples of infertile women compared with fertile women in the secretory phase of the menstrual cycle. This coincided with significantly increased ADAM17 immunostaining detected in the endometrial luminal epithelium in the mid-secretory phase in infertile women. Soluble DLL1 significantly inhibited the adhesive capacity of endometrial epithelial cells via downregulation of helix-loop-helix and hairy/enhancer of split family member HES1 mRNA. Thus, soluble DLL1 may serve as a suitable target or potential biomarker for receptivity.

Decreased MUC1 in endometrium is an independent receptivity marker in recurrent implantation failure during implantation window

BACKGROUND

It is postulated that women suffered from recurrent implantation failure (RIF) have different endometrial receptivity compared to those who experienced with idiopathic recurrent miscarriage (RM). In this study, expression of common endometrial markers Leukemia inhibitor factor (LIF), mucin 1 (MUC1) and integrin β3 were studied and compared.

METHODS

Fourteen women with RIF, 25 with RM and 20 fertile controls were recruited for endometrial biopsy during implantation window on day LH +  7. Spatial and temporal expression of MUC1, LIF and Integrin β3 were compared using semi-quantitative immunohistochemistry. Association of MUC1, LIF and integrin β3 expression levels with demographic and clinical characteristics were determined.

RESULTS

MUC1 expression in both luminal and glandular epithelium in women with RIF were significantly lower than that in women with RM and fertile controls. There were no differences in LIF and Integrin β3 expression in endometrial epithelium among three groups. Decreased MUC1 expression were not significantly associated with age, BMI, gravidity, parity, cycle length, progesterone level and previous miscarriage.

CONCLUSIONS

Deceased expression of MUC1 is an independent marker for endometrial receptivity in RIF women, suggesting MUC1 may contribute to the reproductive failure in RIF women.

The study of blood transcriptome profiles in Holstein cows with miscarriage during peri-implantation

Objective

In this study, the transcriptome profile of cow experiencing miscarriage during peri-implantation was investigated.

Methods

Total transcriptomes were checked by RNA sequencing, and the analyzed by bioinformatics methods, the differentially expressed genes (DEGs) were analysed with hierarchical clustering and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis.

Results

The results suggested that serum progesterone levels were significantly decreased in cows that miscarried as compared to the pregnant cows at 18, 21, 33, 39, and 51 days after artificial insemination. The RNA sequencing results suggested that 32, 176, 5, 10, and 2 DEGs were identified in the pregnant cows and miscarried cows at 18, 21, 33, 39, and 51 d after artificial insemination. And 15, 101, 1, 2, and 2 DEGs were upregulated, and 17, 74, 4, and 8 DEGs were downregulated in the cows in the pregnant and miscarriage groups, respectively at 18, 21, 33, and 39, but no gene was downregulated at 51 d after artificial insemination. These DEGs were distributed to 13, 20, 3, 6, and 20 pathways, and some pathway essential for pregnancy, such as cell adhesion molecules, tumor necrosis factor signaling pathway and PI3K-Akt signaling pathway.

Conclusion

This analysis has identified several genes and related pathways crucial for pregnancy and miscarriage in cows, as well as these genes supply molecular markers to predict the miscarriage in cows.

Prevalence of HHV-6 in endometrium from women with recurrent implantation failure

PROBLEM

To study the prevalence of HHV-6 in endometrial biopsies among women experiencing recurrent implantation failure (RIF) after IVF/ET compared with controls.

METHOD OF STUDY

Thirty women experiencing RIF after IVF/ET and 10 fertile women participated in the study. All women had endometrial biopsies taken in the luteal phase of their menstrual cycle for an endometrial immune profile (EIP) and HHV-6 mRNA as well as lymphocyte and granulocyte populations. The prevalence of HHV-6 in endometrial biopsies was determined, and biopsies for positive and negative expression of HHV-6 were compared with the results of their EIP and lymphocyte and granulocyte populations.

RESULTS

Thirty-seven percentage of women with a history of RIF and 0% of controls demonstrated the presence of HHV-6 in their endometrial biopsies. No associations were found when the results of the endometrial immune profile were compared with the presence or absence of HHV-6. Significant increase in neutrophil-specific CD16b mRNA was found in HHV-6-positive samples, and the levels of B cells-related CD19 mRNA were lower in biopsies from women with RIF in comparison with normal controls.

CONCLUSION

HHV-6 infection is an important factor in RIF.

The functional expression of transient receptor potential channels in the mouse endometrium

STUDY QUESTION

Does mouse endometrial epithelial cells and stromal cells have a similar transient receptor potential (TRP)-channel expression profile and to that found in the human endometrium?

SUMMARY ANSWER

Mouse endometrial epithelial and stromal cells have a distinct TRP channel expression profile analogous to what has been found in human endometrium, and hence suggests the mouse a good model to investigate the role of TRP channels in reproduction.

WHAT IS KNOWN ALREADY

An optimal intercellular communication between epithelial and stromal endometrial cells is crucial for successful reproduction. Members of the TRP family were recently described in the human endometrial stroma; however their functional expression in murine endometrium remains unspecified. Furthermore, epithelial and stromal cells have distinct functions in the reproductive process, implying the possibility for a different expression profile. However, knowledge about the functional expression pattern of TRP channels in either epithelial or stromal cells is not available.

STUDY DESIGN, SIZE, DURATION

In this study, the expression pattern of TRP channels in the murine (C57BL/6 J strain) endometrium was investigated and compared to the human expression pattern. Therefore, expression was examined in uterine tissue isolated during the natural estrous cycle (n = 16) or during an induced menstrual cycle using the menstruating mouse model (n = 28). Next, the functional expression of TRP channels was assessed separately in endometrial epithelial and stromal cell populations.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Quantitative RT-PCR was used to evaluate the relative mRNA expression of TRP channels in murine uterine tissue and cells. To further assess the functional expression in epithelial or stromal cells, primary endometrial cell cultures and Fura2-based calcium-microfluorimetry experiments were performed.

MAIN RESULTS AND THE ROLE OF CHANCE

The expression pattern of TRP channels during the natural estrous cycle or the induced menstrual cycle is analog to what has been shown in human samples. Furthermore, a very distinct expression pattern was observed in epithelial cells compared to stromal cells. Expression of TRPV4, TRPV6 and TRPM6 was significantly higher in epithelial cells whereas TRPV2, TRPC1/4 and TRPC6 were almost exclusively expressed in stromal cells.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Although relevant mRNA levels are detected for TRPV6 and TRPM6, and TRPM4, lack of selective, available pharmacology restricted functional analysis of these ion channels.

WIDER IMPLICATIONS OF THE FINDINGS

Successful reproduction, and more specifically embryo implantation, is a dynamic developmental process that integrates many signaling molecules into a precisely orchestrated program. Here, we describe the expression pattern of TRP channels in mouse endometrium that is similar to human tissue and their restricted functionality in either stromal cells or epithelial cells, suggesting a role in the epithelial-stromal crosstalk. These results will be very helpful to identify key players involved in the signaling cascades required for successful embryo implantation. In addition, these results illustrate that mouse endometrium is a valid representative for human endometrium to investigate TRP channels in the field of reproduction.

STUDY FUNDING/COMPETING INTEREST(S)

The Research Foundation-Flanders (G.0856.13 N to J.V.); the Research Council of the Katholieke Universiteit Leuven (OT/13/113 to J.V. and PF-TRPLe to T.V.); the Planckaert-De Waele fund (to J.V.);  Fonds Wetenschappelijk Onderzoek Belgium (to K.D.C. and A.H.). None of the authors have a conflict of interest.

The Endometrial Polarity Paradox: Differential Regulation of Polarity Within Secretory-Phase Human Endometrium

A major cause of infertility in normal and assisted reproduction cycles is failure of the endometrium to undergo appropriate changes during the secretory phase of the menstrual cycle as it acquires receptivity for an implanting blastocyst. Current dogma states that loss of epithelial polarity in the luminal epithelial cells, the point of first contact between maternal endometrium and blastocyst, may facilitate embryo implantation. Loss of polarity is likely an important change during the secretory phase to overcome mutual repulsion between otherwise polarized epithelial surfaces. Although "plasma membrane transformation" describes morphological/molecular alterations associated with loss of polarity, direct measures of polarity have not been investigated. Transepithelial resistance, a proxy measure of polarity, was downregulated in endometrial epithelial (ECC-1) cells by combined estrogen/progestin, mimicking the hormonal milieu of the secretory phase. Examination of defined polarity markers within human endometrium throughout the menstrual cycle identified downregulation of atypical protein kinase C, Stardust, Crumbs, and Scribble within the luminal-epithelial layer, with upregulation of Scribble within the stromal compartment as the menstrual cycle progressed from the estrogen-dominated proliferative to progesterone-dominated secretory phase. Epithelial (ECC-1) Scribble expression was downregulated in vitro by combined estrogen/progestin and estrogen/progestin/human chorionic gonadotropin treatment, whereas knockdown of Scribble in these cells enhanced "embryo" (trophectodermal spheroid) adhesion. In contrast, Scribble was upregulated within decidualized primary human endometrial stromal cells, with decidualization downregulated upon Scribble knockdown. These data highlight an important contribution of polarity modulation within the human endometrium, likely important for receptivity. Clinical investigations examining how polarity may be modulated in the infertile endometrium may facilitate fertility.

Prominin-2 Prevents the Formation of Caveolae in Normal and Ovarian Hyperstimulated Pregnancy

During early pregnancy, uterine epithelial cells (UECs) become less adherent to the underlying basal lamina and are subsequently removed so the blastocyst can invade the underlying stroma. This process involves the removal of focal adhesions from the basal plasma membrane of UECs. These focal adhesions are thought to be internalized by caveolae, which significantly increase in abundance at the time of blastocyst implantation. A recent in vitro study indicated that prominin-2 prevents the formation of caveolae by sequestering membrane cholesterol. The present study examines whether prominin-2 affects the formation of caveolae and loss of focal adhesions in UECs during normal and ovarian hyperstimulation (OH) pregnancy in the rat. At the time of fertilization during normal pregnancy, prominin-2 is distributed throughout the basolateral plasma membrane. However, at the time of implantation and coincident with an increase in caveolae, prominin-2 is lost from the basal plasma membrane. In contrast, prominin-2 remains in the basolateral plasma membrane throughout OH pregnancy. Transmission electron microscopy showed that this membrane contained few caveolae throughout OH pregnancy. Our results indicate that prominin-2 prevents the formation of caveolae. We suggest the retention of prominin-2 in the basal plasma membrane during OH pregnancy prevents the formation of caveolae and is responsible for the retention of focal adhesions in this membrane, thereby contributing to the reduced implantation rate observed after such treatments.

Novel Non-steroidal Progesterone Receptor Ligands Based on m-Carborane Containing a Secondary Alcohol: Effect of Chirality on Ligand Activity

The progesterone receptor (PR) controls various physiological processes, including the female reproductive system, and nonsteroidal PR ligands are considered to be drug candidates for treatment of various diseases without significant adverse effects. Here, we designed and synthesized m-carborane-based secondary alcohols and investigated their PR-ligand activity. All the synthesized alcohols exhibited PR-antagonistic activity at subnanomolar concentration. Among them, alcohols having a small alkyl side chain and a 4-cyanophenyl group also exhibited PR-agonistic activity in a relatively high concentration range. Optical resolution of secondary alcohols having a methyl side chain was performed, and the PR-ligand activity and PR-binding affinity of the purified enantiomers were examined. The chirality of the secondary alcohol appears to have a more significant influence on PR-agonistic activity than on antagonistic activity.

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.

Novel function of pregnancy-associated plasma protein A: promotes endometrium receptivity by up-regulating N-fucosylation

Glycosylation of uterine endometrial cells plays important roles to determine their receptive function to blastocysts. Trophoblast-derived pregnancy-associated plasma protein A (PAPPA) is specifically elevated in pregnant women serum, and is known to promote trophoblast cell proliferation and adhesion. However, the relationship between PAPPA and endometrium receptivity, as well as the regulation of N-fucosylation remains unclear. We found that rhPAPPA and PAPPA in the serum samples from pregnant women or conditioned medium of trophoblast cells promoted endometrium receptivity in vitro. Moreover, rhPAPPA increased α1,2-, α1,3- and α1,6-fucosylation levels by up-regulating N-fucosyltransferases FUT1, FUT4 and FUT8 expression, respectively, through IGF-1R/PI3K/Akt signaling pathway in human endometrial cells. Additionally, α1,2-, α1,3- and α1,6-fucosylation of integrin αVβ3, a critical endometrium receptivity biomarker, was up-regulated by PAPPA, thereby enhanced its adhesive functions. Furthermore, PAPPA blockage with antibody inhibited embryo implantation in vivo, mouse embryo adhesion and spreading in vitro, as well as N-fucosylation level of the endometrium in pregnant mice. In summary, this study suggests that PAPPA is essential to maintain a receptive endometrium by up-regulating N-fucosylation, which is a potential useful biomarker to evaluate the receptive functions of the endometrium.

Knockdown of regulator of G-protein signalling 2 (Rgs2) leads to abnormal early mouse embryo development in vitro

Regulator of G-protein signalling 2 (Rgs2) is involved in G-protein-mediated signalling by negatively regulating the activity of the G-protein α-subunit. In the present study, the expression patterns of Rgs2 in mouse ovarian tissues and early embryos were determined by semiquantitative reverse transcription-polymerase chain reaction, immunohistochemistry and immunofluorescent analyses. Rgs2 expression was observed in the ovarian tissues of adult female mice, with an almost equal expression levels during different stages of the oestrous cycle. Rgs2 was abundant in the cytoplasm, membrane, nuclei and spindles of intact polar bodies in mouse early embryos at different developmental stages from the zygote to blastocyst. The effect of Rgs2 knockdown on early embryonic development in vitro was examined by microinjecting Rgs2-specific short interfering (si) RNAs into mouse zygotes. Knockdown of endogenous Rgs2 expression led to abnormal embryonic development in vitro, with a considerable number of early embryos arrested at the 2- or 4-cell stage. Moreover, mRNA expression of three zygotic gene activation-related genes (i.e. Zscan4, Tcstv1 and MuERV-L) was decreased significantly in 2-cell arrested embryos. These results suggest that Rgs2 plays a critical role in early embryo development.

Continuous model of conceptus implantation to the maternal endometrium

As placental morphology as well as trophoblast characteristics exhibit wide diversity across mammalian species, underling molecules were also thought to vary greatly. In the majority of cases, however, regardless of the mode of implantation, physiological and biochemical processes in conceptus implantation to the maternal endometrium including the kinds of gene expression and their products are now considered to share many similarities. In fact, recent progress has identified that in addition to the hormones, cytokines, proteases and cell adhesion molecules classically characterized, molecules related to lymphocyte homing and epithelial-mesenchymal transition (EMT) are all required for the progression of conceptus implantation to placentation. In this review, therefore, the newest findings are all incorporated into the molecular and cellular events related to conceptus implantation to the maternal endometrium; primarily from non-invasive bovine placentation and also from invasive human implantation.

Cigarette Smoking Affects Uterine Receptivity Markers

OBJECTIVE

Smoking negatively affects fertility and the rate of other endometrial diseases. To determine the effect of smoking on endometrial physiology, we evaluated 2 endometrial regulatory cytokines and receptivity markers, C-X-C motif chemokine ligand 12 (CXCL12) and fibroblast growth factor 2 (FGF2), both in vitro and in vivo.

STUDY DESIGN

The human endometrial stromal cell line (HESC) and primary human endometrial stromal cells were treated with cigarette smoking extract (CSE) or with vehicle control. Twenty female mice were randomly assigned to either cigarette smoke (CS) exposure for 8 weeks or to a nonsmoke (NS) group that received room air. Immunohistochemical analysis of CXCL12 and FGF2 expression was performed in mouse uterine tissue. Human endometrial samples were obtained from both nonsmokers and smokers. Real-time reverse transcription-polymerase chain reaction was performed for all cell cultures and human samples.

RESULTS

Compared to controls, CXCL12 and FGF2 mRNA expression were significantly decreased in CSE-exposed HESC and primary cells. In mice, immunohistochemical analysis showed that both CXCL12 and FGF2 protein expression was lower in the CS group compared to controls. Similarly, both CXCL12 and FGF2 expression were decreased in women who smoke compared to nonsmokers.

CONCLUSION

Decreased endometrial CXCL12 and FGF2 expression contribute to the impaired endometrial receptivity in women who smoke. Smoking is also associated with decreased rates of endometrial cancer and endometriosis; increased CXCL12 and FGF2 are implicated in both conditions. The changes in the expression of cytokines described here may explain the impact of smoking on all of these diseases. Tobacco has direct effects on normal endometrium that impacts endometrial health and disease.

Roles of Grp78 in Female Mammalian Reproduction

The glucose-regulated protein (GRP78) also referred to as immunoglobulin heavy chain binding protein (Bip) is one of the best characterized endoplasmic reticulum (ER) chaperone proteins, which belongs to the heat-shock protein (HSP) family. GRP78 as a central regulator of ER stress (ERS) plays many important roles in cell survival and apoptosis through controlling the activation of transmembrane ERS sensors: PKR-like ER-associated kinase (PERK), inositol requiring kinase 1 (IRE1), and activating transcription factor 6 (ATF6). Many studies have reported that GRP78 is involved in the physiological and pathological process in female reproduction, including follicular development, corpus luteum (CL), oviduct, uterus, embryo, preimplantation development, implantation/decidualization, and the placenta. The present review summarizes the biological or pathological roles and signaling mechanisms of GRP78 during the reproductive processes. Further study on the functions and mechanisms of GRP78 may provide new insight into mammalian reproduction, which not only enhance the understanding of the physiological roles but also support therapy target against infertility.