Levonorgestrel Inhibits Embryo Attachment by Eliminating Uterine Induction of Leukemia Inhibitory Factor

Unraveling the H19/GAS1 axis in recurrent implantation failure: A potential biomarker for diagnosis and insight into immune microenvironment alteration

Recurrent implantation failure (RIF) presents a significant clinical challenge due to the lack of established diagnostic and therapeutic guidelines. Emerging evidence underscores the crucial role of competitive endogenous RNA (ceRNA) regulatory networks in non-cancerous female reproductive disorders, yet the intricacies and operational characteristics of these networks in RIF are not fully understood. This study aims to demystify the ceRNA regulatory network and identify potential biomarkers for its diagnosis. We analyzed expression profiles of three RNA types (long noncoding RNAs [lncRNAs], microRNAs [miRNAs], and mRNAs) sourced from the GEO database, leading to the identification of the H19-hsa-miR-301a-3p-GAS1 ceRNA network. This network demonstrates significant diagnostic relevance for RIF. Notably, the H19/GAS1 axis within this ceRNA network, identified through correlation analysis, emerged as a promising diagnostic marker, as evidenced by operating receiver operator characteristic (ROC) curve analysis. Further investigation into the binding potential of miR-301a-3p with H19 and GAS1 revealed a close association of these genes with endometrial disorders and embryo loss, as per the Comparative Toxicogenomics Database. Additionally, our immune infiltration analysis revealed a lower proportion of T cells gamma delta (γδ) in RIF, along with distinct differences in the expression of immune cell type-specific markers between fertile patients and those with RIF. We also observed a correlation between aberrant expression of H19/GAS1 and these immune markers, suggesting that the H19/GAS1 axis might play a role in modifying the immune microenvironment, contributing to the pathogenesis of RIF. In conclusion, the ceRNA-based H19/GAS1 axis holds promise as a novel diagnostic biomarker for RIF, potentially enhancing our understanding of its underlying mechanisms and improving the success rates of implantation.

Current perspectives on endometrial receptivity: A comprehensive overview of etiology and treatment

Recurrent implantation failure (RIF) remains a challenging problem in assisted reproductive technology (ART). Further insights into uterine abnormalities that can disturb embryo implantation should be obtained. This review provides an overview of the effects of organic and non-organic uterine disorders on endometrial receptivity. The results suggest that various uterine pathologies can lead to defective embryo implantation via multiple mechanisms. In particular, uterine adenomyosis dysregulates molecular and cellular interactions that are vital for successful embryo implantation with a background of chronic inflammation, which may be alleviated by pretreatment with a gonadotropin-releasing hormone agonist. Uterine myomas can cause endometrial deformation and adverse alterations in uterine contractility. Nonetheless, the effectiveness of myomectomy remains debated, and endometrial polyp removal may be considered, particularly in patients with RIF. Chronic endometritis abrogates the appropriate uterine immunological environment critical for embryo implantation. Abnormal endometrial microbiota have been suggested to influence endometrial receptivity; however, supporting evidence is currently scarce. Platelet-rich plasma therapy may be a potential treatment for thin endometria; nevertheless, further validation is required. Endometrial receptivity analysis can detect dysregulation of the window of implantation, and new non-invasive methods for predicting endometrial receptivity have recently been proposed. However, numerous issues still need to be fully clarified. Further clinical and basic studies are necessary to investigate the pathophysiology of defective endometrial receptivity and identify optimal treatments for patients undergoing ART, especially those with RIF.

Using organoids to investigate human endometrial receptivity

The human endometrium is only receptive to an implanting blastocyst in the mid-secretory phase of each menstrual cycle. Such time-dependent alterations in function require intricate interplay of various factors, largely coordinated by estrogen and progesterone. Abnormal endometrial receptivity is thought to contribute to two-thirds of the implantation failure in humans and therefore significantly hindering IVF success. Despite the incontrovertible importance of endometrial receptivity in implantation, the precise mechanisms involved in the regulation of endometrial receptivity remain poorly defined. This is mainly due to a lack of proper in vitro models that recapitulate the in vivo environment of the receptive human endometrium. Organoids were recently established from human endometrium with promising features to better mimic the receptive phase. Endometrial organoids show long-term expandability and the capability to preserve the structural and functional characteristics of the endometrial tissue of origin. This three-dimensional model maintains a good responsiveness to steroid hormones in vitro and replicates key morphological features of the receptive endometrium in vivo, including pinopodes and pseudostratified epithelium. Here, we review the current findings of endometrial organoid studies that have been focused on investigating endometrial receptivity and place an emphasis on methods to further refine and improve this model.

Potential biomarkers to predict return to fertility after discontinuation of female contraceptives-looking to the future

Nowadays there are multiple types of contraceptive methods, from reversible to permanent, for those choosing to delay pregnancy. Misconceptions about contraception and infertility are a key factor for discontinuation or the uptake of family planning methods. Regaining fertility (the ability to conceive) after contraceptive discontinuation is therefore pivotal. Technical studies to date have evaluated return to fertility by assessing pregnancy as an outcome, with variable results, or return to ovulation as a surrogate measure by assessing hormone levels (such as progesterone, LH, FSH) with or without transvaginal ultrasound. In general, relying on time to pregnancy as an indicator of return to fertility following contraceptive method discontinuation can be problematic due to variable factors independent of contraceptive effects on fertility, hormone clearance, and fertility recovery. Since the ability to conceive after contraceptive method discontinuation is a critical factor influencing product uptake, it is important to have robust biomarkers that easily and accurately predict the timing of fertility return following contraception and isolate that recovery from extrinsic and circumstantial factors. The main aim of this review is to summarize the current approaches, existing knowledge, and gaps in methods of evaluating return-to-fertility as well as to provide insights into the potential of new biomarkers to more accurately predict fertility restoration after contraceptive discontinuation. Biomarker candidates proposed in this document include those associated with folliculogenesis, cumulus cell expansion, follicular rupture and ovulation, and endometrial transport and receptivity which have been selected and scored on predefined criteria meant to evaluate their probable viability for advancement. The review also describes limitations, regulatory requirements, and a potential path to clinically testing these selected biomarkers. It is important to understand fertility restoration after contraceptive method discontinuation to provide users and health providers with accurate evidence-based information. Predictive biomarkers, if easy and low-cost, have the potential to enable robust evaluation of RTF, and provide potential users the information they desire when selecting a contraceptive method. This could lead to expanded uptake and continuation of modern contraception and inform the development of new contraceptive methods to widen user's family planning choices.

An In Vivo Screening Model for Investigation of Pathophysiology of Human Implantation Failure

To improve current infertility treatments, it is important to understand the pathophysiology of implantation failure. However, many molecules are involved in the normal biological process of implantation and the roles of each molecule and the molecular mechanism are not fully understood. This review highlights the hemagglutinating virus of Japan (HVJ; Sendai virus) envelope (HVJ-E) vector, which uses inactivated viral particles as a local and transient gene transfer system to the murine uterus during the implantation period in order to investigate the molecular mechanism of implantation. In vivo screening in mice using the HVJ-E vector system suggests that signal transducer and activator of transcription-3 (Stat-3) could be a diagnostic and therapeutic target for women with a history of implantation failure. The HVJ-E vector system hardly induces complete defects in genes; however, it not only suppresses but also transiently overexpresses some genes in the murine uterus. These features may be useful in investigating the pathophysiology of implantation failure in women.

Progesterone as an Anti-Inflammatory Drug and Immunomodulator: New Aspects in Hormonal Regulation of the Inflammation

The specific regulation of inflammatory processes by steroid hormones has been actively studied in recent years, especially by progesterone (P₄) and progestins. The mechanisms of the anti-inflammatory and immunomodulatory P₄ action are not fully clear. The anti-inflammatory effects of P₄ can be defined as nonspecific, associated with the inhibition of NF-κB and COX, as well as the inhibition of prostaglandin synthesis, or as specific, associated with the regulation of T-cell activation, the regulation of the production of pro- and anti-inflammatory cytokines, and the phenomenon of immune tolerance. The specific anti-inflammatory effects of P₄ and its derivatives (progestins) can also include the inhibition of proliferative signaling pathways and the antagonistic action against estrogen receptor beta-mediated signaling as a proinflammatory and mitogenic factor. The anti-inflammatory action of P₄ is accomplished through the participation of progesterone receptor (PR) chaperones HSP90, as well as immunophilins FKBP51 and FKBP52, which are the validated targets of clinically approved immunosuppressive drugs. The immunomodulatory and anti-inflammatory effects of HSP90 inhibitors, tacrolimus and cyclosporine, are manifested, among other factors, due to their participation in the formation of an active ligand–receptor complex of P₄ and their interaction with its constituent immunophilins. Pharmacological agents such as HSP90 inhibitors can restore the lost anti-inflammatory effect of glucocorticoids and P₄ in chronic inflammatory and autoimmune diseases. By regulating the activity of FKBP51 and FKBP52, it is possible to increase or decrease hormonal signaling, as well as restore it during the development of hormone resistance. The combined action of immunophilin suppressors with steroid hormones may be a promising strategy in the treatment of chronic inflammatory and autoimmune diseases, including endometriosis, stress-related disorders, rheumatoid arthritis, and miscarriages. Presumably, the hormone receptor- and immunophilin-targeted drugs may act synergistically, allowing for a lower dose of each.

Constant Activation of STAT3 Contributes to the Development of Adenomyosis in Females

Adenomyosis is a benign uterine disease that causes dysmenorrhea, heavy menstrual bleeding, and infertility; however, its pathophysiology remains unclear. Since signal transducer and activator of transcription 3 (STAT3) is crucial for endometrial regeneration, we hypothesized that STAT3 participates in adenomyosis pathophysiology. To investigate the influence of STAT3 on adenomyosis development, this study was performed using a novel mouse model of adenomyosis and human specimens of eutopic endometria and adenomyosis lesions. We established a novel mouse model of adenomyosis by puncturing entire mouse uterine layers with a thin needle. Mouse eutopic and ectopic endometria showed a positive immunoreactivity for phosphorylated STAT3 (pSTAT3), the active form of STAT3. Decreased numbers of adenomyotic lesions and reduced expression of Cxcl1, Icam1, and Spp1, which are associated with immune cell chemotaxis and tissue regeneration, were observed in uterine Stat3-deficient mice compared with the controls. In humans, pSTAT3 was intensely expressed at both the eutopic endometrium and the adenomyotic lesions regardless of the menstrual cycle phases. Conversely, it was limitedly expressed in the eutopic endometrium during the menstrual and proliferative phases in women without adenomyosis. Our findings indicate that continuous STAT3 activation promotes adenomyosis development. STAT3 inhibition can be a promising treatment strategy in patients with adenomyosis.

Human blastoids model blastocyst development and implantation

One week after fertilization, human embryos implant into the uterus. This event requires the embryo to form a blastocyst consisting of a sphere encircling a cavity lodging the embryo proper. Stem cells can form a blastocyst model that we called a blastoid¹. Here we show that naive human pluripotent stem cells cultured in PXGL medium² and triply inhibited for the Hippo, TGF-β and ERK pathways efficiently (with more than 70% efficiency) form blastoids generating blastocyst-stage analogues of the three founding lineages (more than 97% trophectoderm, epiblast and primitive endoderm) according to the sequence and timing of blastocyst development. Blastoids spontaneously form the first axis, and we observe that the epiblast induces the local maturation of the polar trophectoderm, thereby endowing blastoids with the capacity to directionally attach to hormonally stimulated endometrial cells, as during implantation. Thus, we propose that such a human blastoid is a faithful, scalable and ethical model for investigating human implantation and development^3,4.

Uterine Receptivity is Reflected by LIF Expression in the Cervix

Recurrent implantation failure is a major problem in assisted reproductive technology (ART). Although ART systems have evolved rapidly over the decades, it is still difficult to diagnose uterine conditions suitable for embryo transfer (ET) without the use of invasive endometrial procedures. Previous studies in mice showed that leukemia inhibitory factor (LIF) is a well-known endometrial biomarker for uterine implantation capacity, also known as uterine receptivity. This study focused on LIF in the mouse and human cervix as a possible biomarker of implantation capacity. We found that high expression of LIF in the cervical epithelium is strongly correlated with that of the uterine epithelium during the peri-implantation period in mice. Likewise, human cervical epithelia also exhibit elevated levels of LIF in the peri-implantation period. In addition, cervical LIF is downregulated in mice with defective implantation caused by pharmacological treatments. These results indicated that cervical LIF is a possible biomarker that detected uterine receptivity without invasive endometrial damage.

Whole-exome sequencing reveals novel candidate single nucleotide variations for preventing adverse effects of levonorgestrel implantation

Aim: To identify novel genes associated with adverse effects of levonorgestrel (LNG) implants based on comparative whole-exome sequencing. Materials & methods: A cohort comprising 104 participants, including 52 controls and 52 women with LNG-related adverse effects, was recruited. Seven cases and eight controls were selected for whole-exome sequencing. We verified 13 single nucleotide variations (SNVs) related with integrin-mediated signaling pathway and cell proliferation using the MassARRAY platform. Results: Finally, we screened 49 cases and 52 controls for analyses. Two SNVs (rs7255721 and rs1042522) were located in ADAMTS10 and TP53, respectively, and significantly different between two groups. These two SNVs lead to changes in protein structure and physicochemical parameters. Conclusion: Here, we defined two pathogenic mutations related to adverse LNG effects.

Uterine Epithelial LIF Receptors Contribute to Implantation Chamber Formation in Blastocyst Attachment

Recent studies have demonstrated that the formation of an implantation chamber composed of a uterine crypt, an implantation-competent blastocyst, and uterine glands is a critical step in blastocyst implantation in mice. Leukemia inhibitory factor (LIF) activates signal transducer and activator of transcription 3 (STAT3) precursors via uterine LIF receptors (LIFRs), allowing successful blastocyst implantation. Our recent study revealed that the role of epithelial STAT3 is different from that of stromal STAT3. However, both are essential for blastocyst attachment, suggesting the different roles of epithelial and stromal LIFR in blastocyst implantation. However, how epithelial and stromal LIFR regulate the blastocyst implantation process remains unclear. To investigate the roles of LIFR in the uterine epithelium and stroma, we generated Lifr-floxed/lactoferrin (Ltf)-iCre (Lifr eKO) and Lifr-floxed/antimüllerian hormone receptor type 2 (Amhr2)-Cre (Lifr sKO) mice with deleted epithelial and stromal LIFR, respectively. Surprisingly, fertility and blastocyst implantation in the Lifr sKO mice were normal despite stromal STAT3 inactivation. In contrast, blastocyst attachment failed, and no implantation chambers were formed in the Lifr eKO mice with epithelial inactivation of STAT3. In addition, normal responsiveness to ovarian hormones was observed in the peri-implantation uteri of the Lifr eKO mice. These results indicate that the epithelial LIFR-STAT3 pathway initiates the formation of implantation chambers, leading to complete blastocyst attachment, and that stromal STAT3 regulates blastocyst attachment without stromal LIFR control. Thus, uterine epithelial LIFR is critical to implantation chamber formation and blastocyst attachment.

Bio-modulated mice epithelial endometrial organoids by low-level laser therapy serves as an invitro model for endometrial regeneration

Endometrial regeneration is a dynamic process that is not well understood. The destruction of the endometrium with the formation of intrauterine adhesions is known as Asherman's syndrome. The lesions range from minor to severe adhesions and their impact on pregnancy is well documented. Operative hysteroscopy is the mainstay of diagnosis and treatment of intrauterine adhesions. Nevertheless, the recurrence rates remain high. It was recorded that low-level laser therapy in low doses has a stimulatory effect on different tissues while the high dose produces a suppressive effect. Organoid is a three-dimensional assembly that displays architectures and functionalities similar to in vivo organs that are being developed from human or animal stem cells or organ-specific progenitors through a self-organization process. Our prospective was to study the effect of Low-Level Laser Therapy (LLLT) on mouse epithelial endometrial organoids regarding cell proliferation and endometrial regeneration as a new modality of treatment. An in vitro clinical trial to generate mouse epithelial organoid model and testing LLLT using He:Ne 632.8 nm device on organoids proliferation, function, and their response to ovarian hormones was performed. Trying endometrial regeneration by culturing organoids with decellularized uterine matrix (DUM) and studying the LLLT effect on the regeneration process. LLLT produced a proliferative effect on the epithelial mouse organoids confirmed by Ki67 and PCNA IHC. The organoids could regenerate the epithelial layer of the endometrium in vitro on DUM and LLLT could help in this process. In conclusion, organoids whether control or bio-stimulated proved a new modality to regenerate the endometrium.

Biomolecular Markers of Recurrent Implantation Failure-A Review

Currently, infertility affects 8–12% of reproductive age couples worldwide, a problem that also affects women suffering from recurrent implantation failure (RIF). RIF is a complex condition resulting from many physiological and molecular mechanisms involving dynamic endometrium–blastocyst interaction. The most important are the endometrial receptivity process, decidualization, trophoblast invasion, and blastocyst nesting. Although the exact multifactorial pathogenesis of RIF remains unclear, many studies have suggested the association between hormone level imbalance, disturbances of angiogenic and immunomodulatory factors, certain genetic polymorphisms, and occurrence of RIF. These studies were performed in quite small groups. Additionally, the results are inconsistent between ethnicities. The present review briefly summarizes the importance of factors involved in RIF development that could also serve as diagnostic determinants. Moreover, our review could constitute part of a new platform for discovery of novel diagnostic and therapeutic solutions for RIF.

Dicalcin suppresses in vitro trophoblast attachment in human cell lines

Implantation is a highly organized process that involves an interaction between a competent blastocyst and a receptive uterus. Despite significant research efforts, the molecular mechanisms governing this complex process remain elusive. Here, we investigated the effect of dicalcin, an S100-like Ca²⁺-binding protein, on the attachment of choriocarcinoma cells (BeWo cells) onto a monolayer of endometrial carcinoma cells (Ishikawa cells). Extracellularly administered dicalcin bound to both BeWo and Ishikawa cells. Pretreatment of BeWo spheroids with dicalcin reduced the attachment ratio of the spheroids onto the monolayer, whereas that of Ishikawa cells showed no apparent change. We identified the partial amino acid sequence of human dicalcin that exhibited maximum suppression for BeWo spheroid attachment. Transmission electron microscopy analysis revealed that the dicalcin-derived peptide caused a dilation of the intercellular junction between BeWo and ISK cells. Peptide treatment of BeWo spheroids downregulated the expression of integrinαvβ3 in BeWo cells, and induced alterations in their phalloidin-staining pattern, as measured by the length of each F-actin fiber and the thickness of the cortical stress fiber. Thus, dicalcin affects reorganization of the intracellular actin meshwork and subsequently the intensity of attachment, functioning as a novel suppressor of implantation.

Retinoblastoma protein promotes uterine epithelial cell cycle arrest and necroptosis for embryo invasion

Retinoblastoma protein (RB) encoded by Rb1 is a prominent inducer of cell cycle arrest (CCA). The hormone progesterone (P₄ ) promotes CCA in the uterine epithelium and previous studies indicated that P₄ activates RB by reducing the phosphorylated, inactive form of RB. Here, we show that embryo implantation is impaired in uterine-specific Rb1 knockout mice. We observe persistent cell proliferation of the Rb1-deficient uterine epithelium until embryo attachment, loss of epithelial necroptosis, and trophoblast phagocytosis, which correlates with subsequent embryo invasion failure, indicating that Rb1-induced CCA and necroptosis of uterine epithelium are involved in embryo invasion. Pre-implantation P₄ supplementation is sufficient to restore these defects and embryo invasion. In Rb1-deficient uterine epithelial cells, TNFα-primed necroptosis is impaired, which is rescued by the treatment with a CCA inducer thymidine or P₄ through the upregulation of TNF receptor type 2. TNFα is expressed in the luminal epithelium and the embryo at the embryo attachment site. These results provide evidence that uterine Rb1-induced CCA is involved in TNFα-primed epithelial necroptosis at the implantation site for successful embryo invasion.

Uterine Epithelial Progesterone Receptor Governs Uterine Receptivity Through Epithelial Cell Differentiation

Progesterone receptor (PGR) is indispensable for pregnancy in mammals. Uterine PGR responds to the heightened levels of ovarian progesterone (P4) after ovulation and regulates uterine gene transcription for successful embryo implantation. Although epithelial and stromal P4-PGR signaling may interact with each other to form appropriate endometrial milieu for uterine receptivity and the subsequent embryo attachment, it remains unclear what the specific roles of epithelial P4-PGR signaling in the adult uterus are. Here we generated mice with epithelial deletion of Pgr in the adult uterus (Pgrfl/flLtfCre/+ mice) by crossing Pgr-floxed and Ltf-Cre mice. Pgrfl/flLtfCre/+ mice are infertile due to the impairment of embryo attachment. Pgrfl/flLtfCre/+ uteri did not exhibit epithelial growth arrest, suggesting compromised uterine receptivity. Both epithelial and stromal expressions of P4-responsive genes decreased in Pgrfl/flLtfCre/+ mice during the peri-implantation period, indicating that epithelial Pgr deletion affects not only epithelial but stromal P4 responsiveness. In addition, uterine LIF, an inducer of embryo attachment, was decreased in Pgrfl/flLtfCre/+ mice. The RNA-seq analysis using luminal epithelial specimens dissected out by laser capture microdissection revealed that the signaling pathways related to extracellular matrix, cell adhesion, and cell proliferation are altered in Pgr fl/flLtf Cre/+ mice. These findings suggest that epithelial PGR controls both epithelial and stromal P4 responsiveness and epithelial cell differentiation, which provides normal uterine receptivity and subsequent embryo attachment.

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 detrimental effects of stress-induced glucocorticoid exposure on mouse uterine receptivity and decidualization

Glucocorticoids (GCs), stress-induced steroid hormones, are released by adrenal cortex and essential for stress adaptation. Recently, there has been renewed interest in the relationship between GCs and pregnancy following the discovery that glucocorticoid receptor is necessary for implantation. It has been widely recognized that stress is detrimental to pregnancy. However, effects of stress-induced GC exposure on uterine receptivity and decidualization are still poorly understood. This study aims to explore the effects of GCs exposure on uterine receptivity, decidualization, and their underlying mechanisms in mice. Single prolonged stress (SPS) and corticosterone (Cort) injection models were used to analyze effects of GC exposure on early pregnancy, respectively. SPS or Cort injection inhibits embryo implantation by interfering Lif signaling and stimulating the uterine deposition of collagen types I, III, and IV on day 4 of pregnancy. Uterine decidualization is also attenuated by SPS or Cort injection through suppressing Cox-2 expression. Cort-induced collagen disorder also suppresses decidualization through regulating mesenchymal-epithelial transition. Our data should shed lights for a better understanding for the effects of GCs on embryo implantation for clinical research.