Decidualization of the human endometrium

The Role of the Endometrium in Implantation: A Modern View

According to the current data, the endometrium acts as a "sensor" of embryo quality, which promotes the implantation of euploid embryos and prevents the implantation and/or subsequent development of genetically abnormal embryos. The present review addresses the nature of the "sensory function" of the endometrium and highlights the necessity for assessing its functional status. The first section examines the evolutionary origin of the "sensory" ability of the endometrium as a consequence of spontaneous decidualization that occurred in placental animals. The second section details the mechanisms for implementing this function at the cellular level. In particular, the recent findings of the appearance of different cell subpopulations during decidualization are described, and their role in implantation is discussed. The pathological consequences of an imbalance among these subpopulations are also discussed. Finally, the third section summarizes information on currently available clinical tools to assess endometrial functional status. The advantages and disadvantages of the approaches are emphasized, and possible options for developing more advanced technologies for assessing the "sensory" function of the endometrium are proposed.

USP22 is required for human endometrial stromal cell proliferation and decidualization by deubiquitinating FoxM1

Despite significant advances in assisted reproductive technology (ART), recurrent implantation failure (RIF) still occurs in some patients. Poor endometrial receptivity and abnormal human endometrial stromal cell (HESC) proliferation and decidualization have been identified as the major causes. Ubiquitin-specific protease 22 (USP22) has been reported to participate in the decidualization of endometrial stromal cells in mice. However, the role of USP22 in HESC function and RIF development remains unknown. In this study, clinical endometrial tissue samples were gathered to investigate the involvement of USP22 in RIF, and HESCs were utilized to examine the molecular mechanisms of USP22 and Forkhead box M1 (FoxM1). The findings indicated a high expression of USP22 in the secretory phase of the endometrium. Knockdown of USP22 led to a notable reduction in the proliferation and decidualization of HESCs, along with a decrease in FoxM1 expression, while overexpression of USP22 yielded opposite results. Furthermore, USP22 was found to deubiquitinate FoxM1 in HESCs. Moreover, both USP22 and FoxM1 were downregulated in the endometria of patients with RIF. In conclusion, these results suggest that USP22 may have a significant impact on HESCs proliferation and decidualization through its interaction with FoxM1, potentially contributing to the underlying mechanisms of RIF pathogenesis.

Differential expression of ion channel coding genes in the endometrium of women experiencing recurrent implantation failures

Our study probed the differences in ion channel gene expression in the endometrium of women with Recurrent Implantation Failure (RIF) compared to fertile women. We analyzed the relative expression of genes coding for T-type Ca2+, ENaC, CFTR, and KCNQ1 channels in endometrial samples from 20 RIF-affected and 10 control women, aged 22-35, via microarray analysis and quantitative real-time PCR. Additionally, we examined DNA methylation in the regulatory region of KCNQ1 using ChIP real-time PCR. The bioinformatics component of our research included Gene Ontology analysis, protein-protein interaction networks, and signaling pathway mapping to identify key biological processes and pathways implicated in RIF. This led to the discovery of significant alterations in the expression of ion channel genes in RIF women's endometrium, most notably an overexpression of CFTR and reduced expression of SCNN1A, SCNN1B, SCNN1G, CACNA1H, and KCNQ1. A higher DNA methylation level of KCNQ1's regulatory region was also observed in RIF patients. Gene-set enrichment analysis highlighted a significant presence of genes involved with ion transport and membrane potential regulation, particularly in sodium and calcium channel complexes, which are vital for cation movement across cell membranes. Genes were also enriched in broader ion channel and transmembrane transporter complexes, underscoring their potential extensive role in cellular ion homeostasis and signaling. These findings suggest a potential involvement of ion channels in the pathology of implantation failure, offering new insights into the mechanisms behind RIF and possible therapeutic targets.

Monoamine oxidases activity maintains endometrial monoamine homeostasis and participates in embryo implantation and development

BACKGROUND

Monoamine oxidases (MAOs) is an enzyme that catalyzes the deamination of monoamines. The current research on this enzyme is focused on its role in neuropsychiatric, neurodevelopmental, and neurodegenerative diseases. Indeed, MAOs with two isoforms, namely, A and B, are located on the outer mitochondrial membrane and are widely distributed in the central nervous system and peripheral tissues. Several reports have described periodic changes in the levels of this enzyme in the human endometrial tissue.

RESULTS

The novel role of MAOs in endometrial receptivity establishment and embryonic development by maintaining monoamine homeostasis was investigated in this study. MAOs activity was observed to be enhanced during the first trimester in both humans and mice under normal conditions. However, under pathological conditions, MAOs activity was reduced and was linked to early pregnancy failure. During the secretory phase, the endometrial stromal cells differentiated into decidual cells with a stronger metabolism of monoamines by MAOs. Excessive monoamine levels cause monoamine imbalance in decidual cells, which results in the activation of the AKT signal, decreased FOXO1 expression, and decidual dysfunction.

CONCLUSIONS

The findings suggest that endometrial receptivity depends on the maintenance of monoamine homeostasis via MAOs activity and that this enzyme participates in embryo implantation and development.

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

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

Investigating Menstruation and Adverse Pregnancy Outcomes: Oxymoron or New Frontier? A Narrative Review

Not discounting the important foetal or placental contribution, the endometrium is a key determinant of pregnancy outcomes. Given the inherently linked processes of menstruation, pregnancy and parturition with the endometrium, further understanding of menstruation will help to elucidate the maternal contribution to pregnancy. Endometrial health can be assessed via menstrual history and menstrual fluid, a cyclically shed, easily and non-invasively accessible biological sample that represents the distinct, heterogeneous composition of the endometrial environment. Menstrual fluid has been applied to the study of endometriosis, unexplained infertility and early pregnancy loss; however, it is yet to be examined regarding adverse pregnancy outcomes. These adverse outcomes, including preeclampsia, foetal growth restriction (FGR), spontaneous preterm birth and perinatal death (stillbirth and neonatal death), lay on a spectrum of severity and are often attributed to placental dysfunction. The source of this placental dysfunction is largely unknown and may be due to underlying endometrial abnormalities or endometrial interactions during placentation. We present existing evidence for the endometrial contribution to adverse pregnancy outcomes and propose that a more comprehensive understanding of menstruation can provide insight into the endometrial environment, offering great potential value as a diagnostic tool to assess pregnancy risk. As yet, this concept has hardly been explored.

Unraveling the Dynamics of Estrogen and Progesterone Signaling in the Endometrium: An Overview

The endometrium is crucial for the perpetuation of human species. It is a complex and dynamic tissue lining the inner wall of the uterus, regulated throughout a woman's life based on estrogen and progesterone fluctuations. During each menstrual cycle, this multicellular tissue undergoes cyclical changes, including regeneration, differentiation in order to allow egg implantation and embryo development, or shedding of the functional layer in the absence of pregnancy. The biology of the endometrium relies on paracrine interactions between epithelial and stromal cells involving complex signaling pathways that are modulated by the variations of estrogen and progesterone levels across the menstrual cycle. Understanding the complexity of estrogen and progesterone receptor signaling will help elucidate the mechanisms underlying normal reproductive physiology and provide fundamental knowledge contributing to a better understanding of the consequences of hormonal imbalances on gynecological conditions and tumorigenesis. In this narrative review, we delve into the physiology of the endometrium, encompassing the complex signaling pathways of estrogen and progesterone.

Lysosome dynamics during human endometrial stromal cells decidualization: effect of para-nonylphenol

During the process of decidualization, the stromal cells of the endometrium change dynamically to create a favorable environment for embryo implantation. Lysosome activity has often been associated with physiological changes in the endometrium during the preimplantation period and early pregnancy. In this study, the effect of para-nonylphenol (p-NP), an endocrine disruptor, on human immortalized endometrial stromal cells (tHESCs) was investigated. After exposure to p-NP (1 nM and 1 pM), the cells were examined for the decidualization markers connexin-43, insulin like growth factor binding protein 1 (IGFBP1), and prolactin. In addition, the effect of p-NP on lysosome biogenesis and exocytosis was investigated by examining the expression and localization of the transcription factor EB (TFEB) and that of the lysosomal-associated membrane protein 1 (LAMP-1). Finally, we evaluated the effect of p-NP on extracellular matrix (ECM) remodeling using a fibronectin assay. Our results showed that p-NP reduced the expression of prolactin protein, increased the nuclear localization of TFEB, and induced the increase and translocation of the lysosomal protein LAMP-1 to the membrane of tHESCs. The data indicate an impairment of decidualization and suggest an increase in lysosomal biogenesis and exocytosis, which is supported by the higher release of active cathepsin D by tHESCs. Given the importance of cathepsins in the processing and degradation of the ECM during trophoblast invasiveness and migration into the decidua, our results appear to be clear evidence of the negative effects of p-NP on endometrial processes that are fundamental to reproductive success and the establishment of pregnancy.NEW & NOTEWORTHY Endocrine disruptors, such as para-nonylphenol, affect the decidualization of human endometrial stromal cells with an impact on decidualization itself, lysosome biogenesis and exocytosis, and extracellular matrix remodeling. All these alterations may negatively impact embryo implantation with the success of reproduction and the establishment of pregnancy.

Oxidative Stress and the Nrf2/PPARγ Axis in the Endometrium: Insights into Female Fertility

Successful pregnancy depends on precise molecular regulation of uterine physiology, especially during the menstrual cycle. Deregulated oxidative stress (OS), often influenced by inflammatory changes but also by environmental factors, represents a constant threat to this delicate balance. Oxidative stress induces a reciprocally regulated nuclear factor erythroid 2-related factor 2/peroxisome proliferator-activated receptor-gamma (Nrf2/PPARγ) pathway. However, increased PPARγ activity appears to be a double-edged sword in endometrial physiology. Activated PPARγ attenuates inflammation and attenuates OS to restore redox homeostasis. However, it also interferes with physiological processes during the menstrual cycle, such as hormonal signaling and angiogenesis. This review provides an elucidation of the molecular mechanisms that support the interplay between PPARγ and OS. Additionally, it offers fresh perspectives on the Nrf2/PPARγ pathway concerning endometrial receptivity and its potential implications for infertility.

The fusion of physics and biology in early mammalian embryogenesis

Biomechanics in embryogenesis is a dynamic field intertwining the physical forces and biological processes that shape the first days of a mammalian embryo. From the first cell fate bifurcation during blastulation to the complex symmetry breaking and tissue remodeling in gastrulation, mechanical cues appear critical in cell fate decisions and tissue patterning. Recent strides in mouse and human embryo culture, stem cell modeling of mammalian embryos, and biomaterial design have shed light on the role of cellular forces, cell polarization, and the extracellular matrix in influencing cell differentiation and morphogenesis. This chapter highlights the essential functions of biophysical mechanisms in blastocyst formation, embryo implantation, and early gastrulation where the interplay between the cytoskeleton and extracellular matrix stiffness orchestrates the intricacies of embryogenesis and placenta specification. The advancement of in vitro models like blastoids, gastruloids, and other types of embryoids, has begun to faithfully recapitulate human development stages, offering new avenues for exploring the biophysical underpinnings of early development. The integration of synthetic biology and advanced biomaterials is enhancing the precision with which we can mimic and study these processes. Looking ahead, we emphasize the potential of CRISPR-mediated genomic perturbations coupled with live imaging to uncover new mechanosensitive pathways and the application of engineered biomaterials to fine-tune the mechanical conditions conducive to embryonic development. This synthesis not only bridges the gap between experimental models and in vivo conditions to advancing fundamental developmental biology of mammalian embryogenesis, but also sets the stage for leveraging biomechanical insights to inform regenerative medicine.

Restoration of functional endometrium in an intrauterine adhesion rat model with endometrial stromal cells transplantation

BACKGROUND

Intrauterine adhesion (IUA) as a prevalent gynecological disease is developed from infection or trauma. However, therapeutic strategies to repair damaged endometrium are relatively limited. Emerging studies have shed light on the crucial role of endometrial stromal cells (EnSCs) in the process of uterine endometrial regeneration. EnSCs isolated from the uterine endometrium have similar characteristics to mesenchymal stem cells (MSCs). However, it is still unknown whether EnSCs could be used as donor cells to treat IUA. The aim of this study was to evaluate the potential efficacy of EnSCs in treating rat IUA.

METHODS

Human EnSCs were isolated from the endometrial tissue of healthy female donors and subjected to extensive expansion and culture in vitro. Immunofluorescence, flow cytometry, cell proliferation assay, trilineage differentiation experiment, and decidualization assay were used to characterize the biological properties of EnSCs. We evaluated the immunoregulatory potential of EnSCs by analyzing their secreted cytokines and conducting bulk RNA sequencing after IFN-γ treatment. After EnSCs were transplanted into the uterine muscle layer in IUA rats, their therapeutic effects and underlying mechanisms were analyzed using histological analysis, Q-PCR, fertility and pregnancy outcome assay, and transcriptome analysis.

RESULTS

We successfully isolated EnSCs from the endometrium of human donors and largely expanded in vitro. EnSCs exhibited characteristics of mesenchymal stem cells and retained responsiveness to sex hormones. Following IFN-γ stimulation, EnSCs upregulated the anti-inflammatory cytokines and activated immunosuppressive molecules. Xenogeneic transplantation of EnSCs successfully repaired injured endometrium and significantly restored the pregnancy rate in IUA rats. Mechanistically, the therapeutic effects of EnSCs on IUA endometrium functioned through anti-inflammation, anti-fibrosis and the secretion of regeneration factor.

CONCLUSIONS

Due to their large expansion ability, immunoregulatory properties, and great potential in treating IUA, EnSCs, as a valuable source of donor cells, could offer a potential treatment avenue for injury-induced IUA.

Supplementation with vitamin D improves the embryo quality in in vitro fertilization (IVF) programs, independently of the patients' basal vitamin D status

PURPOSE

The study aims to demonstrate the effects of Vitamin D (VD) supplementation, prior to oocyte pick-up within IVF protocols, in women with diverse VD status at the enrollment.

METHODS

A total of 204 women eligible for intra-cytoplasmatic sperm injection (ICSI) cycles were included in the study and two homogeneous groups were selected from the database. Both group of patients with normal VD baseline level (> 40 ng/ml) and patients with low VD baseline level (< 20 ng/ml) were divided into control group and treatment group. The control group followed the standard procedure. The treatment group was supplemented with vitamin D3 as cholecalciferol in combination with Myo-Inositol, folic acid, and melatonin 3 months before standard procedure, once a day in the evening.

RESULTS

VD levels significantly increased in the study group of low baseline VD, both in serum and in the follicular fluid compared to controls. The treatment induced a significant improvement of the embryo quality in both group of patients considered.

CONCLUSION

Supplementation of VD in patients undergoing ICSI procedures significantly improved the number of top-quality embryos compared with the control group, either starting from VD normal baseline values or starting from low values.

TRIAL REGISTRATION NUMBER

07/2018.

Angiogenic factors and the lectin pathway of complement in women with secondary recurrent pregnancy loss

The poor remodeling of placental spiral arteries seen in preeclampsia is also discussed to contribute to recurrent pregnancy loss (RPL) preceded by abnormal angiogenesis and excessive complement activation. Low levels of Mannose-binding-lectin (MBL), a pattern recognition molecule (PRM) of the lectin pathway, have been found in women with RPL. We propose that pregnancy loss is connected to defective angiogenesis with reperfusion damage in the placenta and decreased levels of PRM in the lectin pathway in women with RPL. In this cohort study, we investigate the angiogenic factors and the lectin complement pathway in early pregnancy and their time-dependent relationship with pregnancy outcomes in 76 women with secondary RPL (sRPL) who have at least four prior pregnancy losses and a live birth. We evaluated levels of Angiopoietin-1 (Ang-1), Angiopoietin-2 (Ang-2), Vascular Endothelial Growth Factor (VEGF), soluble fms-like tyrosine kinase-1 (sFlt-1), and the PRMs, MBL, ficolin-1, -2, -3 and an additional soluble PRM, Pentraxin-3, during the 5th, 6th, and 7th gestational weeks. Our results showed that, compared to live births, pregnancies that ended in loss were associated with elevated VEGF levels and decreased levels of the Ang-2/Ang-1 ratio. Also, increasing levels of ficolin-2 were significantly associated with pregnancy loss, with MBL showing no association. Our research suggests that women with sRPL may have inadequate placentation with impaired angiogenesis in pregnancies ending in a loss.

Vanishing pelvic mass: Decidualized endometriosis during pregnancy

A 40-year-old woman without history of endometriosis was found to have 10 cm pelvic mass on the routine first trimester ultrasound. Magnetic resonance imaging (MRI) of the pelvis demonstrated a large solid mass abutting the rectum which raised the concern for malignancy. Transrectal biopsy of the mass was performed with histopathology result of decidualized endometriosis. Patient continued her pregnancy and had cesarean section at 39 weeks. Interestingly, no mass was found when obstetrician performed pelvic examination after delivery in the operative room. This case is a unique presentation of endometriosis during pregnancy in a patient with no prior history of endometriosis. Large size and abutment of the rectum by the decidualized endometriosis on MRI led to misinterpretation as malignancy. Our case highlights complexity of the deep infiltrative endometriosis (DIE) during pregnancy which can misguide the providers, lead to unnecessary procedures and unwanted complications.

Lightsheet microscopy integrates single-cell optical visco-elastography and fluorescence cytometry of 3D live tissues

Most common cytometry methods, including flow cytometry, observe suspended or fixed cells and cannot evaluate their structural roles in 3D tissues. However, cellular physical interactions are critical in physiological, developmental, and pathological processes. Here, we present a novel optical visco-elastography that characterizes single-cellular physical interactions by applying in-situ micro-mechanical perturbation to live microtissues under 3D lightsheet microscopy. The 4D digital image correlation (DIC) analysis of ~20,000 nodes tracked the compressive deformation of 3D tissues containing ~500 cells. The computational 3D image segmentation allowed cell-by-cell qualitative observation and statistical analysis, directly correlating multi-channel fluorescence and viscoelasticity. To represent epithelia-stroma interactions, we used a 3D organoid model of maternal-fetal interface and visualized solid-like, well-aligned displacement and liquid-like random motion between individual cells. The statistical analysis through our unique cytometry confirmed that endometrial stromal fibroblasts stiffen in response to decidualization. Moreover, we demonstrated in the 3D model that interaction with placental extravillous trophoblasts partially reverses the attained stiffness, which was supported by the gene expression analysis. Placentation shares critical cellular and molecular significance with various fundamental biological events such as cancer metastasis, wound healing, and gastrulation. Our analysis confirmed existing beliefs and discovered new insights, proving the broad applicability of our method.

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.

The Efficacy of Vitamin D Supplement in the Expression and Protein Levels of Endometrial Decidualization Factors in Women with Recurrent Implantation Failure

Recurrent implantation failure (RIF) is a challenging situation for infertility specialists, and its treatment is introduced as a difficult case in the field of assisted reproductive technology (ART). Vitamin D (VD) is one of the supplements that have been suggested to improve the implantation process. In the present study, the effect of VD on the expression and protein levels of VD receptor (VDR), progesterone receptor (PR), prolactin (PRL), insulin-like growth factor binding protein-1 (IGFBP-1), and homeobox protein A10 (HOXA10) in the endometrial cells of unknown RIF women with and without VD deficiency were assessed by qRT-PCR and immunohistochemistry. Twelve women with unknown RIF and VD deficiency (≤ 20 ng/ml) and twelve women with unknown RIF without VD deficiency (≥ 30 ng/ml) from 2021 to 2022 were identified. Endometrial specimens were collected in the mid-luteal stage before treatment or pregnancy. In the group with VD deficiency, oral medication of VD 50,000 units was prescribed for 2 to 3 months and their serum levels of VD were re-measured, then an endometrial biopsy at the same stage of the menstrual cycle was performed. The expression and protein levels of VDR, PR, PRL, IGFBP1, and HOXA10 in RIF patients with VD deficiency were lower than the RIF patients without VD deficiency (P value < 0.05). Our findings suggest that VD can play a key role in the pregnancy process, especially during embryo implantation and decidualization of the endometrial cells.IRCT registration number: IRCT20220528055006N1, Registration date: 2022-10-15, Registration timing: retrospective.

Roles of bone morphogenetic proteins in endometrial remodeling during the human menstrual cycle and pregnancy

BACKGROUND

During the human menstrual cycle and pregnancy, the endometrium undergoes a series of dynamic remodeling processes to adapt to physiological changes. Insufficient endometrial remodeling, characterized by inadequate endometrial proliferation, decidualization and spiral artery remodeling, is associated with infertility, endometriosis, dysfunctional uterine bleeding, and pregnancy-related complications such as preeclampsia and miscarriage. Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor-β (TGF-β) superfamily, are multifunctional cytokines that regulate diverse cellular activities, such as differentiation, proliferation, apoptosis, and extracellular matrix synthesis, are now understood as integral to multiple reproductive processes in women. Investigations using human biological samples have shown that BMPs are essential for regulating human endometrial remodeling processes, including endometrial proliferation and decidualization.

OBJECTIVE AND RATIONALE

This review summarizes our current knowledge on the known pathophysiological roles of BMPs and their underlying molecular mechanisms in regulating human endometrial proliferation and decidualization, with the goal of promoting the development of innovative strategies for diagnosing, treating and preventing infertility and adverse pregnancy complications associated with dysregulated human endometrial remodeling.

SEARCH METHODS

A literature search for original articles published up to June 2023 was conducted in the PubMed, MEDLINE, and Google Scholar databases, identifying studies on the roles of BMPs in endometrial remodeling during the human menstrual cycle and pregnancy. Articles identified were restricted to English language full-text papers.

OUTCOMES

BMP ligands and receptors and their transduction molecules are expressed in the endometrium and at the maternal-fetal interface. Along with emerging technologies such as tissue microarrays, 3D organoid cultures and advanced single-cell transcriptomics, and given the clinical availability of recombinant human proteins and ongoing pharmaceutical development, it is now clear that BMPs exert multiple roles in regulating human endometrial remodeling and that these biomolecules (and their receptors) can be targeted for diagnostic and therapeutic purposes. Moreover, dysregulation of these ligands, their receptors, or signaling determinants can impact endometrial remodeling, contributing to infertility or pregnancy-related complications (e.g. preeclampsia and miscarriage).

WIDER IMPLICATIONS

Although further clinical trials are needed, recent advancements in the development of recombinant BMP ligands, synthetic BMP inhibitors, receptor antagonists, BMP ligand sequestration tools, and gene therapies have underscored the BMPs as candidate diagnostic biomarkers and positioned the BMP signaling pathway as a promising therapeutic target for addressing infertility and pregnancy complications related to dysregulated human endometrial remodeling.

Material properties of nonpregnant and pregnant human uterine layers

The uterus has critical biomechanical functions in pregnancy and undergoes dramatic material growth and remodeling from implantation to parturition. The intrinsic material properties of the human uterus and how they evolve in pregnancy are poorly understood. To address this knowledge gap and assess the heterogeneity of these tissues, the time-dependent material properties of all human uterine layers were measured with nanoindentation. The endometrium-decidua layer was found to be the least stiff, most viscous, and least permeable layer of the human uterus in nonpregnant and third-trimester pregnant tissues. In pregnancy, the endometrium-decidua becomes stiffer and less viscous with no material property changes observed in the myometrium or perimetrium. Additionally, uterine material properties did not significantly differ between third-trimester pregnant tissues with and without placenta accreta. The foundational data generated by this study will facilitate the development of physiologically accurate models of the human uterus to investigate gynecologic and obstetric disorders.

cAMP regulates the progesterone receptor gene expression through the protein kinase A pathway during decidualization in human immortalized endometrial stromal cells

Decidualization, a crucial process for successful pregnancy establishment and maintenance, involves endometrial stromal cell differentiation. This process is orchestrated by estradiol (E2), progesterone, and other stimuli that increase intracellular cyclic adenosine monophosphate (cAMP) levels. The intracellular progesterone receptor (PR), encoded by the PGR gene, has a key role in decidualization. This study aimed to understand the role of sex steroids and cAMP in regulating PGR expression during the in vitro decidualization of the human immortalized endometrial stromal cell line, T-HESC. We subjected the cells to individual and combined treatments of E2, medroxyprogesterone (MPA), and cAMP. Additionally, we treated cells with PR and estrogen receptor antagonists and a protein kinase A (PKA) inhibitor. We evaluated the expression of PGR isoforms and decidualization-associated genes by RT-qPCR. Our findings revealed that cAMP induced PGR-B and PGR-AB expression by activating the PKA signaling pathway, while MPA downregulated their expression through the PR. Furthermore, downstream genes involved in decidualization, such as those coding for prolactin (PRL), insulin-like growth factor-binding protein-1 (IGFBP1), and Dickkopf-1 (DKK1), exhibited positive regulation via the cAMP-PKA pathway. Remarkably, MPA-activated PR signaling induced the expression of IGFBP1 and DKK1 but inhibited that of PRL. In conclusion, we have demonstrated that the PKA signaling pathway induces PGR gene expression during in vitro decidualization of the T-HESC human endometrial stromal cell line. This study has unraveled some of the intricate regulatory mechanisms governing PGR expression during this fundamental process for implantation and pregnancy maintenance.

NLRP3 inflammasome pathway, the hidden balance in pregnancy: A comprehensive review

The balance of the inflammatory response is indispensable during pregnancy. Inflammasomes are the cytosolic supramolecular protein complexes activated by pattern recognition receptors. These receptors recognize the pathogen and damage/danger-associated molecular patterns. NLRP3 inflammasome complex consists mainly of NLRP3 (leucine-rich repeat-containing and pyrin domain-containing protein 3), a cytosolic sensor molecule, ASC (apoptosis-associated speck-like protein containing a CARD) protein and a cysteine protease pro-caspase-1 as an effector molecule. This complex has a role in producing inflammatory cytokines, interleukin 1 beta and interleukin 18, and inflammasome-dependent programmed cell death pathway pyroptosis. In this review, we focused on and summarised the NLRP3 inflammasome and its roles in normal and pathological pregnancies. The NLRP3 inflammasome pathway influences endometrial receptivity and embryo invasion by inducing epithelial-mesenchymal transition. Abnormal inflammasome activation in the endometrium may adversely affect endometrial receptivity. In addition, NLRP3 inflammasome pathway overactivation may mediate the abnormal inflammatory response at the maternal-fetal interface and be associated with pregnancy complications, such as recurrent implantation failure, pregnancy loss, pre-term birth and pre-eclampsia. Therefore, targeting the NLRP3 inflammasome pathway could develop a new therapeutic approach to prevent the aforementioned pregnancy pathologies.

Alterations in the pro-resolving lipid mediator machinery within first trimester maternal tissue: Implications in decidualization and miscarriage risk

A pivotal event in uterine receptivity and human reproduction is the differentiation of endometrial stromal cells into decidual cells, known as decidualization. Decidualization is interlinked with its inflammatory environment. Our study aimed to investigate the presence and role of pro-resolving lipid mediators in first trimester maternal tissue. We assessed the levels of LXA4 and RvD1, along with their metabolic LOX enzymes, in elective (control) and sporadic miscarriage samples. We investigated the effects of LXA4 and RvD1 on decidualization using primary endometrial stromal cells and the immortalized endometrial stromal St-T1b cell line. The upregulation of 12- and 15-LOX expression was observed in pregnancy tissue after sporadic miscarriage, suggesting an inflammatory imbalance. Furthermore, incubation with these lipid mediators led to a decrease in decidualization biomarkers PRL and IGFBP-1, accompanied by morphological changes indicative of aberrant differentiation. The expression of LOX enzymes in decidual natural killer cells suggests their involvement in regulating the inflammatory surroundings and the extent of decidualization.

Implantation and Decidualization in PCOS: Unraveling the Complexities of Pregnancy

Polycystic Ovary Syndrome (PCOS) is a prevalent endocrine disorder in women of reproductive age, affecting 5-15% globally with a large proportion undiagnosed. This review explores the multifaceted nature of PCOS and its impact on pregnancy, including challenges in fertility due to hormonal imbalances and insulin resistance. Despite restoring ovulation pharmacologically, women with PCOS face lower pregnancy rates and higher risks of implantation failure and miscarriage. Our review focuses on the complexities of hormonal and metabolic imbalances that impair endometrial receptivity and decidualization in PCOS. Disrupted estrogen signaling, reduced integrity of endometrial epithelial tight junctions, and insulin resistance impair the window of endometrial receptivity. Furthermore, progesterone resistance adversely affects decidualization. Our review also examines the roles of various immune cells and inflammatory processes in the endometrium, contributing to the condition's reproductive challenges. Lastly, we discuss the use of rodent models in understanding PCOS, particularly those induced by hormonal interventions, offering insights into the syndrome's impact on pregnancy and potential treatments. This comprehensive review underscores the need for advanced understanding and treatment strategies to address the reproductive complications associated with PCOS, emphasizing its intricate interplay of hormonal, metabolic, and immune factors.

Paradoxical role of phosphorylated STAT3 in normal fertility and the pathogenesis of adenomyosis and endometriosis†

Signal transducer and activator of transcription 3 (STAT3), when phosphorylated at tyrosine 705, plays an important role in endometrial stromal cell decidualization and the receptivity of the endometrial epithelium during embryo implantation. However, the function of phosphorylated STAT3 (p-STAT3) in normal uterine receptivity is distinct from that in adenomyosis and endometriosis. In normal pregnancy, STAT3 phosphorylation in the endometrial epithelium determines the success of embryo implantation by regulating uterine receptivity. Additionally, p-STAT3 promotes cellular proliferation and differentiation during endometrial decidualization, which is crucial for embryonic development. In contrast, excessive STAT3 phosphorylation occurs in adenomyosis and endometriosis, which may lead to disease progression. Therefore, achieving a delicate balance in STAT3 activation is crucial. This review aimed to focus on the current understanding and knowledge gaps regarding the control of p-STAT3 activity in normal and pathological endometrial processes. This topic is important because precise control of p-STAT3 production could alleviate the symptoms of adenomyosis and endometriosis, improve endometrial receptivity, and potentially mitigate infertility without compromising normal fertility processes.

Polycystic ovary syndrome and adverse pregnancy outcomes: potential role of decidual function

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting fertility and mental health among women of reproductive age. In addition to anovulation and hyperandrogenism, patients also experience metabolic issues, such as insulin resistance, obesity, and dyslipidemia, as well as chronic low-grade inflammation throughout the body. Recent studies have shown that even with assisted reproductive technology to treat anovulatory issues, patients with PCOS still have higher rates of adverse pregnancy outcomes and abortion compared to normal pregnancies. These findings suggest that PCOS may impair the endometrium and disrupt the onset and maintenance of healthy pregnancies. Decidualization is a crucial step in the process of healthy pregnancy, during which endometrial stromal cells (ESCs) differentiate into secretory decidual stromal cells (DSCs) regulated by hormones and local metabolism. This article comprehensively reviews the pathological processes of PCOS and the mechanisms involved in its impaired decidualization. In addition, we explore how PCOS increases the incidence of adverse pregnancy outcomes (APO). By gaining a better understanding of the adverse effects of PCOS on pregnancy and its specific mechanisms, we hope to provide a theoretical basis for reducing APO and improving the live birth rate among women with PCOS.

Progesterone and cAMP synergistically induce SHP2 expression via PGR and CREB1 during uterine stromal decidualization

Decidualization of endometrial stroma is a key step in embryo implantation and its abnormality often leads to pregnancy failure. Stromal decidualization is a very complex process that is co-regulated by estrogen, progesterone and many local factors. The signaling protein SHP2 encoded by PTPN11 is dynamically expressed in decidualized endometrial stroma and mediates and integrates various signals to govern the decidualization. In the present study, we investigate the mechanism of PTPN11 gene transcription. Estrogen, progesterone and cAMP co-induced decidualization of human endometrial stromal cell in vitro, but only progesterone and cAMP induced SHP2 expression. Using the luciferase reporter, we refined a region from -229 bp to +1 bp in the PTPN11 gene promoter comprising the transcriptional core regions that respond to progesterone and cAMP. Progesterone receptor (PGR) and cAMP-responsive element-binding protein 1 (CREB1) were predicted to be transcription factors in this core region by bioinformatic methods. The direct binding of PGR and CREB1 on the PTPN11 promoter was confirmed by electrophoretic mobility and chromatin immunoprecipitation in vitro. Knockdown of PGR and CREB1 protein significantly inhibited the expression of SHP2 induced by medroxyprogesterone acetate and cAMP. These results demonstrate that transcription factors PGR and CREB1 bind to the PTPN11 promoter to regulate the expression of SHP2 in response to decidual signals. Our results explain the transcriptional expression mechanism of SHP2 during decidualization and promote the understanding of the mechanism of decidualization of stromal cells.

Material Properties of Nonpregnant and Pregnant Human Uterine Layers

The uterus has critical biomechanical functions in pregnancy and undergoes dramatic material growth and remodeling from implantation to parturition. The intrinsic material properties of the human uterus and how they evolve in pregnancy are poorly understood. To address this knowledge gap and assess the heterogeneity of these tissues, the time-dependent material properties of all human uterine layers were measured with nanoindentation. The endometrium-decidua layer was found to be the least stiff, most viscous, and least permeable layer of the human uterus in nonpregnant and third-trimester pregnant tissues. In pregnancy, endometrium-decidua becomes stiffer and less viscous with no material property changes observed in the myometrium or perimetrium. Additionally, uterine material properties did not significantly differ between third-trimester pregnant tissues with and without placenta accreta. The foundational data generated by this study will facilitate the development of physiologically accurate models of the human uterus to investigate gynecologic and obstetric disorders.

Cyclical endometrial repair and regeneration: Molecular mechanisms, diseases, and therapeutic interventions

The endometrium is a unique human tissue with an extraordinary ability to undergo a hormone-regulated cycle encompassing shedding, bleeding, scarless repair, and regeneration throughout the female reproductive cycle. The cyclical repair and regeneration of the endometrium manifest as changes in endometrial epithelialization, glandular regeneration, and vascularization. The mechanisms encompass inflammation, coagulation, and fibrinolytic system balance. However, specific conditions such as endometriosis or TCRA treatment can disrupt the process of cyclical endometrial repair and regeneration. There is uncertainty about traditional clinical treatments' efficacy and side effects, and finding new therapeutic interventions is essential. Researchers have made substantial progress in the perspective of regenerative medicine toward maintaining cyclical endometrial repair and regeneration in recent years. Such progress encompasses the integration of biomaterials, tissue-engineered scaffolds, stem cell therapies, and 3D printing. This review analyzes the mechanisms, diseases, and interventions associated with cyclical endometrial repair and regeneration. The review discusses the advantages and disadvantages of the regenerative interventions currently employed in clinical practice. Additionally, it highlights the significant advantages of regenerative medicine in this domain. Finally, we review stem cells and biologics among the available interventions in regenerative medicine, providing insights into future therapeutic strategies.

Role of Endometrial Extracellular Vesicles in Mediating Cell-to-Cell Communication in the Uterus: A Review

There are several critical events that occur in the uterus during early pregnancy which are necessary for the establishment and maintenance of pregnancy. These events include blastocyst implantation, uterine decidualization, uterine neoangiogenesis, differentiation of trophoblast stem cells into different trophoblast cell lineages, and formation of a placenta. These processes involve several different cell types within the pregnant uterus. Communication between these cell types must be intricately coordinated for successful embryo implantation and the formation of a functional maternal-fetal interface in the placenta. Understanding how this intricate coordination transpires has been a focus of researchers in the field for many years. It has long been understood that maternal endometrial tissue plays a key role in intercellular signaling during early pregnancy, sending signals to nearby tissues in a paracrine manner. Recently, insights have been obtained into the mechanisms by which these signaling events occur. Notably, the endometrium has been shown to secrete extracellular vesicles (EVs) that contain crucial cargo (proteins, lipids, RNA, miRNA) that are taken up by recipient cells to initiate a response leading to the occurrence of critical events during implantation and placentation. In this review, we aim to summarize the role that endometrium-derived EVs play in mediating cell-to-cell communications within the pregnant uterus to orchestrate the events that must occur to establish and maintain pregnancy. We will also discuss how aberrant endometrial EV signaling may lead to pathophysiological conditions, such as endometriosis and infertility.

Endometrial receptivity in women of advanced age: an underrated factor in infertility

BACKGROUND

Modern lifestyle has led to an increase in the age at conception. Advanced age is one of the critical risk factors for female-related infertility. It is well known that maternal age positively correlates with the deterioration of oocyte quality and chromosomal abnormalities in oocytes and embryos. The effect of age on endometrial function may be an equally important factor influencing implantation rate, pregnancy rate, and overall female fertility. However, there are only a few published studies on this topic, suggesting that this area has been under-explored. Improving our knowledge of endometrial aging from the biological (cellular, molecular, histological) and clinical perspectives would broaden our understanding of the risks of age-related female infertility.

OBJECTIVE AND RATIONALE

The objective of this narrative review is to critically evaluate the existing literature on endometrial aging with a focus on synthesizing the evidence for the impact of endometrial aging on conception and pregnancy success. This would provide insights into existing gaps in the clinical application of research findings and promote the development of treatment options in this field.

SEARCH METHODS

The review was prepared using PubMed (Medline) until February 2023 with the keywords such as 'endometrial aging', 'receptivity', 'decidualization', 'hormone', 'senescence', 'cellular', 'molecular', 'methylation', 'biological age', 'epigenetic', 'oocyte recipient', 'oocyte donation', 'embryo transfer', and 'pregnancy rate'. Articles in a language other than English were excluded.

OUTCOMES

In the aging endometrium, alterations occur at the molecular, cellular, and histological levels suggesting that aging has a negative effect on endometrial biology and may impair endometrial receptivity. Additionally, advanced age influences cellular senescence, which plays an important role during the initial phase of implantation and is a major obstacle in the development of suitable senolytic agents for endometrial aging. Aging is also accountable for chronic conditions associated with inflammaging, which eventually can lead to increased pro-inflammation and tissue fibrosis. Furthermore, advanced age influences epigenetic regulation in the endometrium, thus altering the relation between its epigenetic and chronological age. The studies in oocyte donation cycles to determine the effect of age on endometrial receptivity with respect to the rates of implantation, clinical pregnancy, miscarriage, and live birth have revealed contradictory inferences indicating the need for future research on the mechanisms and corresponding causal effects of women's age on endometrial receptivity.

WIDER IMPLICATIONS

Increasing age can be accountable for female infertility and IVF failures. Based on the complied observations and synthesized conclusions in this review, advanced age has been shown to have a negative impact on endometrial functioning. This information can provide recommendations for future research focusing on molecular mechanisms of age-related cellular senescence, cellular composition, and transcriptomic changes in relation to endometrial aging. Additionally, further prospective research is needed to explore newly emerging therapeutic options, such as the senolytic agents that can target endometrial aging without affecting decidualization. Moreover, clinical trial protocols, focusing on oocyte donation cycles, would be beneficial in understanding the direct clinical implications of endometrial aging on pregnancy outcomes.

The Role of Dydrogesterone in the Management of Luteal Phase Defect: A Comprehensive Review

The luteal phase of the menstrual cycle is a pivotal period characterized by hormonal intricacies that lay the foundation for successful embryo implantation and early pregnancy development. Luteal phase defect (LPD), marked by abnormalities in luteal function, presents challenges that can impede reproductive outcomes. This comprehensive review article explores the role of dydrogesterone in LPD management, elucidating its mechanisms of action, evidence of efficacy, safety profile, and potential in combination therapies. Dydrogesterone, a synthetic progestogen, closely mirrors natural progesterone's actions, effectively supplementing the luteal phase and enhancing endometrial receptivity. Clinical studies demonstrate improved pregnancy rates, extended luteal phase support, and enhanced reproductive outcomes with dydrogesterone supplementation. Its favorable safety profile, minimal side effects, and reduced risk of unwanted hormonal effects contribute to its appeal. Furthermore, dydrogesterone's inclusion in international guidelines solidifies its importance in LPD management. Combination therapies, leveraging synergistic effects, offer a comprehensive approach. As gaps in knowledge persist, future research directions and personalized treatment strategies pave the way for a future where dydrogesterone stands as a beacon of hope in conquering the challenges of LPD and achieving successful reproductive outcomes.

Circulatory extracellular vesicle derived miR-195-5p promotes cellular apoptosis and suppresses cell proliferation in the buffalo endometrial primary cell culture

In pregnant animals, communication between the mother and conceptus occurs via extracellular vesicles (EVs) that carry several biomolecules such as nucleic acids (miRNAs, mRNAs), proteins, and lipids. At the time of implantation, the endometrium undergoes several morphological and physiological changes, such as angiogenesis, apoptosis, and cell proliferation regulation at the implantation site, to attain a receptive state. This study was conducted to detect pregnancy-specific miRNAs derived from extracellular vesicles in the systemic circulation of Bubalus bubalis (water buffalo) and to assess their functional significance in the modulation of endometrial primary cells. The extracellular vesicles were isolated from the blood plasma using a precipitation-based method and further characterized by various methods such as Differential light scattering, Nanoparticle tracking assay, Western blot, and transmission electron microscopy. The relative expression of the selected extracellular vesicles associated miRNAs (EV-miRNA) at different intervals (days 15, 19, 25, and 30) post artificial insemination (AI) was analyzed using RT-qPCR, and expression of miR-195-5p was found to be significantly higher (P < 0.01) in pregnant animals on day 19 post AI (implantation window) as compared to day 15 post AI. The elevated expression might indicate the involvement of this miRNA in the maternal-conceptus cross-talk occurring during the implantation period. The KEGG pathway enrichment and Gene Ontology analyses of the miR-195-5p target genes revealed that these were mostly involved in the PI3-Akt, MAPK, cell cycle, ubiquitin-mediated proteolysis, and mTOR signaling pathways, which are related to the regulation of cell proliferation. Transfecting the in vitro cultured cells with miR-195-5p mimic significantly suppressed (P < 0.05) the expression of its target genes such as YWHAQ, CDC27, AKT-3, FGF-7, MAPK8, SGK1, VEGFA, CACAND1, CUL2, MKNK1, and CACAN2D1. Furthermore, the downregulation of the miR-195-5p target genes was positively correlated with a significant increase in the apoptotic rate and a decrease in the proliferation. In conclusion, the current findings provide vital information on the presence of EV miR-195-5p in maternal circulation during the implantation window indicating its important role in the modulation of buffalo endometrium epithelial cells via promoting cell death. Altogether, the milieu of miR-195-5p may serve as a novel and potential molecular factor facilitating the implantation of the early embryo during the establishment of pregnancy in buffaloes. Thus, miR-195-5p may be identified as a unique circulatory EV biomarker related to establishing pregnancy in buffaloes as early as day 19 post-AI.

Generation of Human Endometrial Assembloids with a Luminal Epithelium using Air-Liquid Interface Culture Methods

The endometrial lining of the uterus is essential for women's reproductive health and consists of several different types of epithelial and stromal cells. Although models such as gland-like structures (GLSs) and endometrial assembloids (EnAos) are successfully established, they lack an intact luminal epithelium, which makes it difficult to recapitulate endometrial receptivity. Here, a novel EnAo model (ALI-EnAo) is developed by combining endometrial epithelial cells (EnECs) and stromal cells (EnSCs) and using an improved matrix and air-liquid interface (ALI) culture method. ALI-EnAos exhibit intact EnSCs and glandular and luminal epithelia, which recapitulates human endometrium anatomy, cell composition, hormone-induced menstrual cycle changes, gene expression profiles, and dynamic ciliogenesis. The model suggests that EnSCs, together with the extracellular matrix and ALI culture conditions, contribute to EnAo phenotypes and characteristics reflective of the endometrial menstrual cycle. This enables to transcriptionally define endometrial cell subpopulations. It anticipates that ALI-EnAos will facilitate studies on embryo implantation, and endometrial growth, differentiation, and disease.

Signaling Pathways of the Insulin-like Growth Factor Binding Proteins

The 6 high-affinity insulin-like growth factor binding proteins (IGFBPs) are multifunctional proteins that modulate cell signaling through multiple pathways. Their canonical function at the cellular level is to impede access of insulin-like growth factor (IGF)-1 and IGF-2 to their principal receptor IGF1R, but IGFBPs can also inhibit, or sometimes enhance, IGF1R signaling either through their own post-translational modifications, such as phosphorylation or limited proteolysis, or by their interactions with other regulatory proteins. Beyond the regulation of IGF1R activity, IGFBPs have been shown to modulate cell survival, migration, metabolism, and other functions through mechanisms that do not appear to involve the IGF-IGF1R system. This is achieved by interacting directly or functionally with integrins, transforming growth factor β family receptors, and other cell-surface proteins as well as intracellular ligands that are intermediates in a wide range of pathways. Within the nucleus, IGFBPs can regulate the diverse range of functions of class II nuclear hormone receptors and have roles in both cell senescence and DNA damage repair by the nonhomologous end-joining pathway, thus potentially modifying the efficacy of certain cancer therapeutics. They also modulate some immune functions and may have a role in autoimmune conditions such as rheumatoid arthritis. IGFBPs have been proposed as attractive therapeutic targets, but their ubiquity in the circulation and at the cellular level raises many challenges. By understanding the diversity of regulatory pathways with which IGFBPs interact, there may still be therapeutic opportunities based on modulation of IGFBP-dependent signaling.

Closer to the Reality-Proteome Changes Evoked by Endometrial Scratching in Fertile Females

Endometrial scratching (ES) has been widely used in assisted reproductive technology to possibly improve pregnancy rates, but its exact mechanism is still not understood or investigated, and its benefits are controversially discussed. Hypothetically, ES may trigger a local immune response, leading to an improved endometrial receptivity. So far, it has been shown that ES affects the gene expression of cytokines, growth factors, and adhesive proteins, potentially modulating inflammatory pathways and adhesion molecule expression. Our pilot study applying proteomic analysis reveals that ES probably has an impact on the proteins involved in immune response pathways and cytoskeleton formation, which could potentially increase endometrial receptivity. Specifically, proteins that are involved in the immune response and cytoskeleton regulation showed a trend toward higher abundance after the first ES. On the other hand, proteins with a decreasing abundance after the first ES play roles in the regulation of the actin cytoskeleton and cellular processes such as intracellular transport, apoptosis, and autophagy. These trends in protein changes suggest that ES may affect endometrial tissue stiffness and extracellular matrix remodeling, potentially enhancing the embryos' implantation. To our knowledge, this pilot study provides, for the first time, data investigating potential changes in the endometrium due to the scratching procedure that might explain its possible benefit for patients in infertility treatment. Furthermore, the proteome of a group of patients suffering from repeated implantation failure was compared to that of the fertile group in order to transfer the basic science to clinical routine and application.

Decidualization dampens toll-like receptor mediated inflammatory responses in human endometrial stromal cells by upregulating IκBα

Endometrial stromal cells (EnSCs) are the major cell type of the human endometrium and they undergo dramatic differentiation, termed decidualization, every month that enables them to be receptive to implantation. Appropriate decidualization and EnSC function is key for a successful pregnancy. EnSC function may be affected when the uterus is exposed to bacterial and viral infection. However, how human EnSCs respond to viral and bacterial components have not been well-studied and it remains unclear whether uterine innate immune responses change during decidualization. This study demonstrated that viral double-stranded RNA [Poly(I:C)] and bacterial lipopolysaccharide (LPS) upregulated undecidualized human EnSC production of a large array of proinflammatory cytokines and chemokines, and revealed that these immune responses were significantly dampened during decidualization in vitro and in vivo. This dampened response was associated with increased NFKBIA transcription during decidualization that leads to the accumulation of this negative regulator in decidualizing EnSCs that can bind to NFκB p65 and prevents its nuclear translocation and downstream Toll-like receptor signaling. These findings highlight that endometrial responses to infection may vary at different stages of the menstrual cycle which may be important for preparing the endometrium to support the growth of the semi-allogenic blastocyst. This work emphasizes the need to consider menstrual cycle stage, sex hormone levels and the differentiation status of cells when examining inflammatory responses in the future.

Impaired secretion of C-X-C motif chemokine ligand 10 by stimulation with a Toll-like receptor 4 ligand in endometrial epithelium of infertile patients with minimal-to-mild endometriosis

Successful embryo implantation requires transient, well-controlled inflammation in decidualizing cells. In mice, Toll-like receptor (TLR) 4 signaling in endometrial epithelial cells (EECs) by stimulation with factors present in seminal fluids has been shown to be a key upstream driver of a controlled inflammatory response. Clinical evidence supports that exposure of the female reproductive tract to seminal plasma promotes implantation success. We investigated the response of EECs to TLR2 (Pam3Csk4), TLR 3 (Poly I:C), and TLR4 (lipopolysaccharides [LPS]) ligands with respect to secretion of C-X-C motif chemokine ligand (CXCL) 10 (CXCL10) and interleukin-6 (IL-6) in infertile patients with minimal-to-mild endometriosis (EECs-endo) (n = 38) and those of healthy, fertile women (EECs-healthy) (n = 30). Stimulation with either Pam3Csk4, Poly I:C or LPS, significantly induced CXCL10 and IL-6 in EECs-healthy (p < 0.05). In EECs-endo, either Pam3Csk4 or Poly I:C significantly induced CXCL10 (p < 0.05), whereas no significant response was observed after stimulation with LPS. Neither LPS, Poly I:C, nor Pam3Csk4 significantly induced IL-6 secretion in EECs-endo. Secretion of CXCL10 in EECs-healthy after stimulation with LPS was significantly higher (p < 0.05) than that in EECs-endo. CXCL10 decreased cell proliferation of EECs from both groups. Activation of nuclear factor kappa light chain enhancer of activated B cells and signal transducer and activator of transcription 3 signalings was not impaired, but activation of p38 mitogen-activated protein kinases signaling by LPS stimulation was impaired in EECs-endo. The present findings suggested that an insufficient response of EECs to a TLR4 ligand may be involved in molecular mechanisms of endometriosis-associated infertility.

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.

Exploring the presence of markers of decidualization in the fallopian tubes: a systematic review

The fallopian tubes (FTs) are part of the female upper genital tract. The healthy FT provides the biological environment for successful fertilization and facilitates the subsequent movement of the conceptus to the endometrial cavity. However, when the FT is damaged, as with salpingitis, pyosalpinx, and hydrosalpinx, it may increase the risk of an ectopic pregnancy, a life-threatening condition. Decidualization refers to a multifactorial process by which the endometrium changes to permit blastocyst implantation. The decidualization reaction is vital for endometrial receptivity during the window of implantation. To date, no comprehensive review that collates evidence on decidualization in the human FT has been conducted. Therefore, the aim of this review is to compile the current evidence on cellular decidualization occurring in the healthy and pathological FT in women of reproductive age. A literature search was conducted using five databases and identified 746 articles, 24 of which were analyzed based on inclusion and exclusion criteria. The available evidence indicates that the FT are able to undergo decidual changes under specific circumstances; however, the exact mechanism by which this occurs is poorly understood. Further research is needed to elucidate the mechanism by which decidualization can occur in the FT.

Endometrial and placental stem cells in successful and pathological pregnancies

The endometrium is a dynamic tissue that undergoes extensive remodeling during the menstrual cycle and further gets modified during pregnancy. Different kinds of stem cells are reported in the endometrium. These include epithelial stem cells, endometrial mesenchymal stem cells, side population stem cells, and very small embryonic-like stem cells. Stem cells are also reported in the placenta which includes trophoblast stem cells, side population trophoblast stem cells, and placental mesenchymal stem cells. The endometrial and placental stem cells play a pivotal role in endometrial remodeling and placental vasculogenesis during pregnancy. The dysregulation of stem cell function is reported in various pregnancy complications like preeclampsia, fetal growth restriction, and preterm birth. However, the mechanisms by which it does so are yet elusive. Herein, we review the current knowledge of the different type of stem cells involved in pregnancy initiation and also highlight how their improper functionality leads to pathological pregnancy.

The effect of obesity on uterine receptivity is mediated by endometrial extracellular vesicles that control human endometrial stromal cell decidualization and trophoblast invasion

The objectives of the present study were to determine whether obesity impacts human decidualization and the endometrial control of trophoblast invasion (both of which are required for embryo implantation) and evaluate the potential involvement of endometrial extracellular vesicles (EVs) in the regulation of these physiological processes. Using primary human cell cultures, we first demonstrated that obesity is associated with significantly lower in vitro decidualization of endometrial stromal cells (ESCs). We then showed that a trophoblastic cell line's invasive ability was greater in the presence of conditioned media from cultures of ESCs from obese women. The results of functional assays indicated that supplementation of the culture medium with EVs from nonobese women can rescue (at least in part) the defect in in vitro decidualization described in ESCs from obese women. Furthermore, exposure to endometrial EVs from obese women (vs. nonobese women) was associated with significantly greater invasive activity by HTR-8/SVneo cells. Using mass-spectrometry-based quantitative proteomics, we found that EVs isolated from uterine supernatants of biopsies from obese women (vs. nonobese women) presented a molecular signature focused on cell remodelling and angiogenesis. The proteomics analysis revealed two differentially expressed proteins (fibronectin and angiotensin-converting enzyme) that might be involved specifically in the rescue of the decidualization capacity in ESCs from obese women; both of these proteins are abundantly present in endometrial EVs from nonobese women, and both are involved in the decidualization process. In conclusion, our results provided new insights into the endometrial EVs' pivotal role in the poor uterine receptivity observed in obese women.

Study of hydrosalpinx on endometrial growth and expression of HOXA10mRNA and related factors

Objective

The objective of the study is to extract the patient's endometrium at the time of proliferative stage using hydrosalpinx in order to culture the cells and decidualization induction in vitro. Further, the study is also intended at identifying the expression of HOXA10mRNA and related factors and understand the hydrosalpinx's impact upon the working mechanism of endometrial cells.

Methods

Once the extraction of the primary cells is over, the cells are cultured and other activities are performed such as the cell identification, CCK8 assay, cell decidua induction and HE staining. The researchers assessed the expression levels of HOXA10, IGFBP1 and avβ3 in either proliferation or secretion of the endometrium. This was accomplished using Western blot assay and real-time fluorescence quantitative PCR.

Results

The results confirmed that at the time of endometrial proliferation, there was a decline in the expression of HOXA10 as a result of tubal effusion influence. This affected its expression in the secretory stage i.e., corresponding function. Further, a significant decline was observed in the levels of HOXA10mRNA of endometrial cells that were subjected to continuous tubal effusion, post decidualization. It was found that during decidualization, if thetubal effusion is removed, it is possible to restore the expression of HOXA10mRNA to a certain extent, though it is not possible to reach the general endometrial level. So, in terms of clinical aspects, the expression of HOxa10 mRNA by the endometrial cells decreases significantly when blocking the hydrosalpinx.

Conclusions

Among hydrosalpinx patients, one of the major mechanisms that damage the endometrium was found to be the abnormal expression of HOXA10 followed by IGFBP1 and avβ3, its downstream genes. This further results in the implantation of the embryo as well. Though it is possible to gradually repair the damage after the removal of hydrosalpinx, the recovery is a time-consuming process.

Establishment of the fetal-maternal interface: developmental events in human implantation and placentation

Early pregnancy is a complex and well-orchestrated differentiation process that involves all the cellular elements of the fetal-maternal interface. Aberrant trophoblast-decidual interactions can lead to miscarriage and disorders that occur later in pregnancy, including preeclampsia, intrauterine fetal growth restriction, and preterm labor. A great deal of research on the regulation of implantation and placentation has been performed in a wide range of species. However, there is significant species variation regarding trophoblast differentiation as well as decidual-specific gene expression and regulation. Most of the relevant information has been obtained from studies using mouse models. A comprehensive understanding of the physiology and pathology of human implantation and placentation has only recently been obtained because of emerging advanced technologies. With the derivation of human trophoblast stem cells, 3D-organoid cultures, and single-cell analyses of differentiated cells, cell type-specific transcript profiles and functions were generated, and each exhibited a unique signature. Additionally, through integrative transcriptomic information, researchers can uncover the cellular dysfunction of embryonic and placental cells in peri-implantation embryos and the early pathological placenta. In fact, the clinical utility of fetal-maternal cellular trafficking has been applied for the noninvasive prenatal diagnosis of aneuploidies and the prediction of pregnancy complications. Furthermore, recent studies have proposed a viable path toward the development of therapeutic strategies targeting placenta-enriched molecules for placental dysfunction and diseases.

Rational Design of Nanomedicine for Placental Disorders: Birthing a New Era in Women's Reproductive Health

The placenta is a transient organ that forms during pregnancy and acts as a biological barrier, mediating exchange between maternal and fetal circulation. Placental disorders, such as preeclampsia, fetal growth restriction, placenta accreta spectrum, and gestational trophoblastic disease, originate in dysfunctional placental development during pregnancy and can lead to severe complications for both the mother and fetus. Unfortunately, treatment options for these disorders are severely lacking. Challenges in designing therapeutics for use during pregnancy involve selectively delivering payloads to the placenta while protecting the fetus from potential toxic side effects. Nanomedicine holds great promise in overcoming these barriers; the versatile and modular nature of nanocarriers, including prolonged circulation times, intracellular delivery, and organ-specific targeting, can control how therapeutics interact with the placenta. In this review, nanomedicine strategies are discussed to treat and diagnose placental disorders with an emphasis on understanding the unique pathophysiology behind each of these diseases. Finally, prior study of the pathophysiologic mechanisms underlying these placental disorders has revealed novel disease targets. These targets are highlighted here to motivate the rational design of precision nanocarriers to improve therapeutic options for placental disorders.

The Importance of Natural Antioxidants in Female Reproduction

Oxidative stress (OS) has an important role in female reproduction, whether it is ovulation, endometrium decidualization, menstruation, oocyte fertilization, or development andimplantation of an embryo in the uterus. The menstrual cycle is regulated by the physiological concentration of reactive forms of oxygen and nitrogen as redox signal molecules, which trigger and regulate the length of individual phases of the menstrual cycle. It has been suggested that the decline in female fertility is modulated by pathological OS. The pathological excess of OS compared to antioxidants triggers many disorders of female reproduction which could lead to gynecological diseases and to infertility. Therefore, antioxidants are crucial for proper female reproductive function. They play a part in the metabolism of oocytes; in endometrium maturation via the activation of antioxidant signaling pathways Nrf2 and NF-κB; and in the hormonal regulation of vascular action. Antioxidants can directly scavenge radicals and act as a cofactor of highly valuable enzymes of cell differentiation and development, or enhance the activity of antioxidant enzymes. Compensation for low levels of antioxidants through their supplementation can improve fertility. This review considers the role of selected vitamins, flavonoids, peptides, and trace elements with antioxidant effects in female reproduction mechanisms.

E2F2 is upregulated by the ERK pathway and regulates decidualization via MCM4

Cell cycle modulation is an important event during decidualization. E2F2 is a transcription regulator that plays a vital role in cell cycle regulation. However, the biological role of E2F2 in decidualization has not yet been identified. In this study, estrogen (E2) and progestin (P4)-induced in vitro and in vivo decidualization models were applied. Our data showed that the expression levels of E2F2 and its downstream target MCM4 were downregulated in the uterus tissues of E2P4-treated mice compared with control mice. In hESCs, exposure to E2P4 resulted in a significant decrease in E2F2 and MCM4 expression. E2P4 treatment reduced hESC proliferation and ectopic expression of E2F2 or MCM4 elevated the viability of E2P4-treated hESCs. In addition, ectopic expression of E2F2 or MCM4 restored the expression of G1 phase-associated proteins. The ERK pathway was inactivated in E2P4-treated hESCs. Treatment with ERK agonist Ro 67-7476 restored the expression of E2F2, MCM4, and G1 phase-associated proteins that were inhibited by E2P4. Moreover, Ro 67-7476 retracted the levels of IGFBP1 and PRL that were induced by E2P4. Collectively, our results indicate that E2F2 is regulated by ERK signaling and contributes to decidualization via regulation of MCM4. Therefore, E2F2/MCM4 cascade may serve as promising targets for alleviating decidualization dysfunction.

Emerging Roles of Endocannabinoids as Key Lipid Mediators for a Successful Pregnancy

In recent years, Cannabis use/misuse for treating pregnancy-related symptoms and other chronic conditions has increased among pregnant women, favored by decriminalization and/or legalization of its recreational uses in addition to its easy accessibility. However, there is evidence that prenatal Cannabis exposure might have adverse consequences on pregnancy progression and a deleterious impact on proper neurodevelopmental trajectories in the offspring. Maternal Cannabis use could interfere with the complex and finely controlled role performed by the endocannabinoid system in reproductive physiology, impairing multiple gestational processes from blastocyst implantation to parturition, with long-lasting intergenerational effects. In this review, we discuss current clinical and preclinical evidence regarding the role of endocannabinoids in development, function, and immunity of the maternal–fetal interface, focusing on the impact of Cannabis constituents on each of these gestational processes. We also discuss the intrinsic limitations of the available studies and the future perspectives in this challenging research field.

Role of kisspeptin in decidualization and unexplained recurrent spontaneous abortion via the ERK1/2 signalling pathway

INTRODUCTION

This study aimed to study the expression and function of kisspeptin during human uterine decidualization in recurrent spontaneous abortion (RSA) and the underlying mechanism.

METHODS

All patients were recruited from the Clinical Reproductive Center of the Second Affiliated Hospital of Soochow University. Mice models of RSA (CBA/J × DBA/2) and normal pregnancy (CBA/J × BALB/c) were established, respectively. Kisspeptin expression in the serum and decidual tissues of women with RSA were detected. The function of kisspeptin during decidualization in human endometrial stromal cells (HESCs) was assessed by enhancing and silencing kisspeptin expression. CBA/J × DBA/2 pregnant mice were injected with kisspeptin polypeptide, kisspeptin receptor blocker, and expression of decidualization markers was observed. The regulation of ERK1/2 signalling pathway were verified.

RESULTS

Serum kisspeptin levels were significantly lower in patients with RSA than in normal pregnant individuals, as was the expression of kisspeptin, p-ERK, and decidualization indicators in the decidua. Additionally, kisspeptin inhibition downregulated the expression of decidualization markers in HESCs. In mice with RSA, kisspeptin was significantly downregulated, and p-ERK expression at the maternal-foetal interface was significantly decreased. Moreover, exogenous kisspeptin supplementation improved the levels of IGFBP-1 and dPRL, upregulated p-ERK expression, and reduced the abortion rate.

DISCUSSION

Kisspeptin is involved in promoting uterine decidualization via the ERK1/2 signalling pathway.

Histone H4 hyperacetylation but not DNA methylation regulates the expression of decidualization-associated genes during induced human endometrial stromal cells decidualization

The efficiency of endometrial stromal cells (ESC) decidualization is a critical player in successful embryo implantation and further pregnancy development. Epigenetic mechanisms strictly regulate massive changes that affect endometrium in each cycle, so investigating epigenetic patterns could help identify endometrial targets for infertility treatment solutions. The aim of our study was to analyze the changes in epigenetic modulators, histone modifications, and DNA methylation during induced human ESC in vitro decidualization. Decidualization markers and epigenetic factors' gene and protein expression levels were assessed during ESC cells in vitro decidualization, performing RT-qPCR and immunoblot tests. Furthermore, chromatin immunoprecipitation (ChIP) and methylated DNA immunoprecipitation (MeDIP) analysis by the following qPCR were conducted to evaluate the level of H4hyperAc and 5-methylcytosine in the decidualization-associated gene promoter and exon regions accordingly. Our results revealed that ESC decidualization caused the down-regulation of HDAC2 and subunits of PRC2. We observed the increased global level of H4hyperAc and H3K27me3. We also demonstrated that H4hyperAc was specifically enriched in the decidualization-associated genes (WNT4, HAND2, STAT5A) promoter regions during ESC decidualization. In contrast, the DNA methylation level in these promoter regions was relatively low before ESC induction and did not vary through ESC decidualization. Our findings demonstrate that specific gene promoters' histone acetylation increases during the induced ESC decidualization, which indicates the importance of epigenetic regulation in endometrial decidualization.

β-Lactoglobulin affects the oxidative status and viability of equine endometrial progenitor cells via lncRNA-mRNA-miRNA regulatory associations

The β-lactoglobulin (β-LG) was previously characterized as a mild antioxidant modulating cell viability. However, its biological action regarding endometrial stromal cell cytophysiology and function has never been considered. In this study, we investigated the influence of β-LG on the cellular status of equine endometrial progenitor cells under oxidative stress. The study showed that β-LG decreased the intracellular accumulation of reactive oxygen species, simultaneously ameliorating cell viability and exerting an anti-apoptotic effect. However, at the transcriptional level, the reduced mRNA expression of pro-apoptotic factors (i.e. BAX and BAD) was accompanied by decreased expression of mRNA for anti-apoptotic BCL-2 and genes coding antioxidant enzymes (CAT, SOD-1, GPx). Still, we have also noted the positive effect of β-LG on the expression profile of transcripts involved in endometrial viability and receptivity, including ITGB1, ENPP3, TUNAR and miR-19b-3p. Finally, the expression of master factors of endometrial decidualization, namely prolactin and IGFBP1, was increased in response to β-LG, while non-coding RNAs (ncRNAs), that is lncRNA MALAT1 and miR-200b-3p, were upregulated. Our findings indicate a novel potential role of β-LG as a molecule regulating endometrial tissue functionality, promoting viability and normalizing the oxidative status of endometrial progenitor cells. The possible mechanism of β-LG action includes the activation of ncRNAs essential for tissue regeneration, such as lncRNA MALAT-1/TUNAR and miR-19b-3p/miR-200b-3p.