Decidualization of the human endometrium

The human endometrium: atlases, models, and prospects

Approximately every month, the human endometrium undergoes a cycle of proliferation, differentiation, and, in the absence of pregnancy, shedding and repair. Each cycle relies on intricate interorgan coordination of hormonal secretions. Endometrial dysfunction causes significant health complications, including abnormal menstrual bleeding and endometriosis. However, effective diagnosis and treatments are hampered by understudied aetiology. Recent single-cell profiling has disentangled the diverse and dynamic nature of the endometrium, revealing regulatory roles of WNT, NOTCH, and TGFβ signalling. These insights have informed mechanistic studies enabled by advanced in vitro models that capture endometrial cellular heterogeneity and structure. In this review, we outline key single-cell transcriptomics atlases and models that provided new avenues for studying endometrial biology, discuss their limitations, and propose future directions.

HIV-associated preeclampsia: evaluation of lymphangiogenesis in placental bed samples

The role of angiogenesis in preeclampsia pathogenesis is widely studied; however, despite the lymphatic vessels' complementary role to the blood vascular system, studies on their morphology in the placenta and placental bed are lacking. In total, 87 placental bed specimens were utilized, which were grouped into normotensive pregnant (n = 28), early-onset preeclampsia (n = 31), and late-onset preeclampsia (n = 28), and further stratified by human immunodeficiency virus (HIV) status. Tissue was immunostained with podoplanin antibody to investigate whether HIV infection affects lymphangiogenesis. The lymphatic capillary density and luminal areas within the placental bed were morphometrically assessed. Lymphatic microvessel density and mean area/lumen in the preeclampsia group were higher and larger than in the normotensive group, respectively (p = 0.01 and p = 0.001). A correlation between blood pressure levels and lymphatic microvessel density was observed (r ≥ 0.272; p ≤ 0.032). Significant differences were observed between the mean microvessel density of normotensive HIV-uninfected and HIV-infected groups (5.9 ± 2.3 versus 7.5 ± 2.8, p = 0.01) and late-onset preeclampsia HIV-uninfected and HIV-infected groups (7.1 ± 3.9 versus 7.8 ± 2.7, p = 0.01). The mean area/lumen between normotensive HIV-uninfected and HIV-infected, and late-onset preeclampsia HIV-uninfected and HIV-infected groups were significantly different (p = 0.03 and p = 0.001). Small lymphatic capillaries were significantly abundant in late-onset preeclampsia HIV-infected (p = 0.03) and normotensive HIV-infected (p = 0.0001) groups compared with uninfected groups. Lymphatic capillary density and area/lumen upregulation was observed in the placental bed of HIV-infected women, with a positive correlation between maternal blood pressure and lymphatic microvessel density, potentially affecting birth weight in the preeclampsia group.

Lipopolysaccharide alters cell communication at the maternal-fetal interface revealed by single-cell RNA-sequencing

Embryo implantation is a decisive process in pregnancy that highly relies on effective cell communication at the maternal-fetal interface. Embryo implantation failure is frequently caused by gram-negative bacterial infection, therefore, this study aimed to investigate the effect of Lipopolysaccharides (LPS)-induced inflammation on cellular composition, cell-cell interaction and key signaling pathways at the maternal-fetal interface using Single-cell RNA-Sequence (scRNA-Seq). LPS exposure significantly up-regulated the expression of pro-inflammatory cytokines, CCL-2, TNF-α, and IL-1β in maternal-fetal interface tissues as well as triggered the recruitment of neutrophils, monocytes and eosinophils into peripheral blood. scRNA-Seq revealed endometrial epithelial cells (EpCs), stromal cells (ESCs), Fibroblasts (FiCs) and 15 other cell types. LPS administration significantly shifted the cellular proportions, increased populations of immune cells and fibroblasts while decreased ESCs and EpCs. Cellular differentiation indicated that all ESCs originated from ESC8 while ESC2 and 7 were the most differentiated ESC subtypes. Likewise, cellular communication demonstrated notable differences, reversed interactions were observed exclusively on the LPS exposure between luminal epithelial (LE) and glandular epithelial (GE) cells. ESC8 was inactive in the control group but exhibited robust interactions in the LPS group. Furthermore, the communication analysis predicted significant disruptions in the signaling pathways: Embryo-maternal communications (DHEA, BMP, LIFR, EDN, and NEGR pathways). Endometrial stromal-epithelial crosswalks (5αP, CAECAM, DHEAS and HH pathways) and Endometrial stromal-immune cell interactions (EGF and NCAM pathways). Our findings suggest that signaling pathways are essential for maternal-fetal communication. The disruption of the pathways in response to LPS may provide new molecular targets for diagnosing and treating implantation failure and recurrent pregnancy loss.

Endometrial aging is accompanied by H3K27ac and PGR loss

Whether and how endometrial aging affects fertility remains unclear. In our in-house clinical cohort at the Center for Reproductive Medicine of Peking University Third Hospital (n = 1,149), we observed adverse pregnancy outcomes in the middle-aged group after excluding aneuploid embryos, implying the negative impact of endometrial aging on fertility. To understand endometrial aging, we performed comprehensive transcriptomic profiling of the mid-secretory endometrium of young (<35 years) and middle-aged (≥35 years) patients. This analysis revealed that H3K27ac loss is linked to impaired endometrial receptivity in the middle-aged group. We eliminated H3K27ac in young human endometrial stromal cells and observed reduced progesterone receptor (PGR), a critical regulator of endometrial receptivity. Lastly, we validated the association between H3K27ac/PGR loss and uterine aging in a mouse model. Our findings establish H3K27ac as a critical regulator of PGR and demonstrate that endometrial H3K27ac loss is associated with aging-related fertility decline. This work provides valuable insights into enhancing the safety and efficacy of assisted reproductive technologies in future clinical practices.

Endometrial Stromal Senescence Mediates the Progression of Intrauterine Adhesions

Cellular senescence has emerged as a key mediator in organ-specific fibrosis. Here, we have established the role of endometrial stromal senescence in the progression of endometrial fibrosis, termed intrauterine adhesions (IUA). IUA have significant negative effects on women's reproductive health and are associated with infertility. We have generated original gene signatures to identify endometrial stromal senescence in single-cell and bulk RNA-sequencing data. By applying generated gene signatures, we revealed an increased level of stromal senescence during the proliferative phase in the endometrium of patients with IUA. Further comparative analysis of cell-cell communications demonstrated that senescent stromal cells in the IUA endometrium create an immunosuppressive and profibrotic microenvironment through an elevated expression of LGALS9. Endometrial stromal senescence persists during the window of implantation and correlates with impaired embryo receptivity of the IUA endometrium. Therefore, stromal senescence can be regarded as a primary cause of an unresponsive endometrium with decreased receptivity and thickness in IUA patients. A LGALS9 immunotherapy protocol, specifically designed to neutralize LGALS9 immunosuppressive activity of senescent cells, may offer a promising opportunity to restore effective immune clearance of these cells within the IUA stroma. Consequently, an LGALS9-based strategy could emerge as a novel therapeutic avenue in the treatment of IUA.

New approaches in the analysis of spent embryo culture media in the IVF process

PURPOSE

In vitro fertilization occurs in a controlled laboratory setting, where oocytes are fertilized by sperm, and the resulting embryos are cultured to the blastocyst stage before transfer to the uterus. The secreted/consumed substances by the embryo in the extracellular environment (secretome) contain a variety of molecules that may provide insights into embryo quality. This study presents new perspectives on the non-invasive and cost-effective assessment and evaluation of embryos during the IVF process, utilizing a spent embryo culture medium (SECM).

METHODS

The SECM was used from blastocysts prepared for a single blastocyst transfer and was analyzed in two groups-the SECM with successful (F) (n = 30) and unsuccessful (N) (n = 36) embryo implantation in the woman's uterus. Building on our previous next-generation sequencing results, we decided to validate the expression levels of specific miRNAs, particularly hsa-miR-16-5p and hsa-miR-92a-3p, to assess their potential to predict embryo implantation success.

RESULTS

Our results demonstrate different expression levels of miRNA molecules in the monitored groups, which could lead to their use in non-invasive analysis of the implantation potential of embryos in the IVF process. In this study, we employed a metabolomics approach using 3D fluorescence analysis of SECM to identify differences between the studied groups, F and N. Our preliminary results indicate a slightly increased metabolic activity in the group with unsuccessful embryo implantation group.

CONCLUSIONS

This is our pilot study where we demonstrated the use of two approaches in analyzing the SECM to predict the implantation potential of embryos in the IVF process which promises further development.

Effects of Nonablative Er-YAG Laser on Human Endometrial Stromal Cells (hESCs): A Pilot Study

OBJECTIVES

To investigate the thermo-chemical effects of nonablative Er:YAG laser on human endometrial stromal cells (hESCs).

MATERIALS AND METHODS

In this laboratory based study, for the hESCs cultures, endometrial tissue biopsy samples were obtained from three fertile women in the late proliferative phase. In this laboratory-based study, seven experimental groups were created: Estradiol (E2) group, E2 + Sham (S) group, E2 + P4 group, E2 + Laser (L) group, E2 + P4 + L group, hESC group and hESC+L group. Cell cultures reaching confluence on the matrigel-coated petri dishes in all groups were incubated for 12, 24, 48, and 72 h after laser irradiation, respectively. Nonablative Er:YAG laser irradiation was performed to the hESCs culture. The main outcome of this study involves assessing the alterations in MMP-2, TNF-α, IL-6, VEGF-A, and IGFBP-1 levels within conditioned media of hESC cultures subsequent to the Er:YAG laser irradiation.

RESULTS

Median MMP-2 levels significantly differed between groups at the 12th, 24th, 48th, and 72nd hour (p = 0.012, p = 0.045, p = 0.021, and p = 0.032, respectively). All media of hESCs irradiated with Er-YAG laser had higher median MMP-2 values. At the 48th hour, the groups showed significant differences in terms of median TNF-α levels (p = 0.029), which were lower in the groups that received Er-YAG laser. At the 12th hour, median IL-6 levels differed significantly between the groups (p = 0.011), being higher in the groups that received Er-YAG laser. At the 72nd hour, lower median VEGF-A values were observed for the groups that received Er-YAG laser (p = 0.021). A statistically significant difference existed in terms of median IGFBP-1 levels between the groups at the 24th hour, with higher levels in the groups which received Er-YAG laser (p = 0.041).

CONCLUSION

Our findings demonstrated that the non-ablative Er-YAG laser induces tissue remodeling, modulates immune responses by favoring Th2 cell activity and suppresses Th1 cell activity in hESCs. Additionally, it exerts favorable impact on decidualization.

Decidualization-associated recruitment of cytotoxic memory CD8+T cells to the maternal-fetal interface for immune defense

Decidual CD8+T (dCD8+T) cells are pivotal in the maintenance of the delicate balance between immune tolerance towards the fetus and immune resistance against pathogens. The endometrium and decidua represent the uterine environments before and during pregnancy, respectively, yet the composition and phenotypic alterations of uterine CD8+T cells in these tissues remain unclear. Using flow cytometry and analysis of transcriptome profiles, we demonstrated that human dCD8+T and endometrial CD8+T (eCD8+T) cells exhibited similar T cell differentiation statuses and phenotypes of tissue infiltrating or residency, compared to peripheral CD8+T (pCD8+T) cells. However, dCD8+T cells showed decreased expression of coinhibitory marker (PD-1), chemotaxis marker (CXCR3), and tissue-resident markers (CD69 and CD103), along with increased expression of granzyme B and granulysin, compared to eCD8+T cells. In vitro cytotoxicity assays further demonstrated that dCD8+T cells had greater effector functions than eCD8+T cells. Additionally, both in vitro and in vivo chemotaxis assays confirmed the recruitment of non-resident effector memory T cell subsets to the pregnant decidua, contributing to the dCD8+T cell-mediated anti-infection mechanism at the maternal-fetal interface. This work demonstrates dCD8+T cells replenished from the circulation retain their cytotoxic capacity, which may serve as an enhanced defense mechanism against infection during pregnancy.

Revolutionizing Implantation Studies: Uterine-Specific Models and Advanced Technologies

Implantation is a complex and tightly regulated process essential for the establishment of pregnancy. It involves dynamic interactions between a receptive uterus and a competent embryo, orchestrated by ovarian hormones such as estrogen and progesterone. These hormones regulate proliferation, differentiation, and gene expression within the three primary uterine tissue types: myometrium, stroma, and epithelium. Advances in genetic manipulation, particularly the Cre/loxP system, have enabled the in vivo investigation of the role of genes in a uterine compartmental and cell type-specific manner, providing valuable insights into uterine biology during pregnancy and disease. The development of endometrial organoids has further revolutionized implantation research. They mimic the native endometrial structure and function, offering a powerful platform for studying hormonal responses, implantation, and maternal-fetal interactions. Combined with omics technologies, these models have uncovered the molecular mechanisms and signaling pathways that regulate implantation. This review provides a comprehensive overview of uterine-specific genetic tools, endometrial organoids, and omics. We explore how these advancements enhance our understanding of implantation biology, uterine receptivity, and decidualization in reproductive research.

Single-cell atlas of the pregnant equine endometrium before and after implantation†

Embryo implantation in the mare occurs just over one month after fertilization, coinciding with the production of chorionic gonadotropin. The factors that regulate this late implantation in the mare, and whether they are unique to horses or shared with more invasive embryo implantation in other species, remain poorly understood. This study aimed to determine and compare the transcriptome and subpopulations of endometrial cells before and after embryo implantation in the horse. Single-cell RNA sequencing was used to characterize the transcriptome of nearly 97,000 endometrial cells collected from biopsies of the endometrium at the beginning (day 33 of gestation) and after embryo implantation (day 42 of gestation) in mares. Sixteen immune and 24 non-immune cell clusters were identified, representing known major cell populations as well as novel subpopulations of horse immune cells such as resident innate lymphoid cells and mucosal-associated invariant T cells. Contrary to current knowledge, endometrial natural killer (eNK) cells were the most abundant endometrial leukocyte population during implantation in horses. Moreover, eNK cells not only expressed genes that may interact with fetal MHC I, such as LY49F, but also exert immunoregulatory functions independent of MHC I expression, such as CD96/TIGIT. Analogous to other species studied, upregulation of CXCR4 was found in several subpopulations of immune cells. Our results suggest that despite distinctive and later placentation compared with humans, horses share some key similarities in the mechanisms of embryo implantation.

The effect of norethisterone acetate on the uterine telocytes, immune cells and progesterone receptors in albino rats

This study is the first attempt to examine the effects of NETA on immune cells and telocytes. The results of this study form an important knowledge base for the development of new information on the mechanism of contraceptive action of NETA in the uterus. Norethisterone acetate (NETA) is a synthetic progestogen medication commonly utilized in birth control pills, menopausal hormone therapy, and for curing abnormal uterine bleeding and endometriosis. Furthermore NETA has many beneficial uses in veterinary medicine as control and synchronization of estrous cycle. The impact of NETA on the endometrial stromal cells (ESCs), telocytes, and uterine immune cells is not well understood. Therefore, this study focuses on assessing changes in uterine immune cells, ESCs, and telocytes following exposure to NETA in albino rats. To achieve this objective, fourteen adult female albino rats were randomly divided into two groups: a control group and an NETA-treated group. Rats in the control group received daily pelleted food, water, and were oral administered of 2 ml distilled water. In contrast, rats in the NETA-treated group received daily pelleted food, water, and were orally administered 20 µg of NETA dissolved in 2 ml distilled water. The experiment spanned three weeks. The findings of this study revealed that NETA usage increases the infiltration and activity of immune cells (eosinophils, neutrophils, macrophages, lymphocytes, and mast cells). Furthermore, it enhances the vesicular activity of uterine telocytes and their communication with various immune cells. NETA also influences decidualization and the immunoexpression of progesterone receptors in uterine epithelial and immune cells. This study concludes that the primary mechanism by which NETA controls pregnancy is through decidual (pregnancy-like) effects or improper decidualization, which inhibits fertilization and implantation respectively. Our research provides evidence of the contraceptive mechanism of NETA from an immunological perspective in an animal model.

Convergent evolution of complex adaptive traits modulates angiogenesis in high-altitude Andean and Himalayan human populations

Convergent adaptations represent paradigmatic examples of the capacity of natural selection to influence organisms' biology. However, the possibility to investigate the genetic determinants underpinning convergent complex adaptive traits has been offered only recently by methods for inferring polygenic adaptations from genomic data. Relying on this approach, we demonstrate how high-altitude Andean human groups experienced pervasive selective events at angiogenic pathways, which resemble those previously attested for Himalayan populations despite partial convergence at the single-gene level was observed. This provides additional evidence for the drivers of convergent evolution of enhanced blood perfusion in populations exposed to hypobaric hypoxia for thousands of years.

Molecular Basis of Impaired Decidualization in the Eutopic Endometrium of Endometriosis Patients

Endometriosis is a chronic gynecological disorder characterized by the presence of endometrial tissue outside the uterine cavity. A common feature of this pathology is the impaired decidualization of endometrial stromal cells, a critical process that prepares the uterus for embryo implantation. This decidualization defect has been mechanistically linked to progesterone resistance in endometriotic lesions. However, the presence and underlying mechanisms of decidualization defects in the eutopic endometrium of women with endometriosis remain controversial. The aim of the present study is to integrate and discuss molecular evidence from both in vivo and in vitro studies examining decidualization alterations in the eutopic endometrium of patients with endometriosis. Multiple studies have demonstrated impaired decidualization in the eutopic endometrium of women with endometriosis. These alterations have been reported on multiple genes, signaling pathways, and epigenetic processes. However, additional functional studies are warranted to elucidate whether these decidualization defects directly contribute to endometriosis-associated infertility. A better understanding of the decidualization process and its dysregulation in endometriosis will not only advance the development of targeted fertility treatments but also facilitate the design of more effective therapeutic strategies for managing this chronic condition.

Extracellular matrix and pregnancy: functions and opportunities caught in the net

The extracellular matrix is a complex network of macromolecules that support the growth and homeostatic development of organisms. By conveying multiple signaling cascades, it impacts on several biological processes and influences the behaviour of numerous cell types. During the endometrial cycle and the key events necessary for a correct embryo implantation and placentation, this bioactive meshwork is substantially modified to favour endometrial receptivity and vascular adaptation, trophoblast cell migration, and immune activation as well. A correct extracellular remodeling is fundamental for the establishment of a physiological pregnancy; indeed, the occurrence of altered matrix modifications associates with gestational disorders such as preeclampsia. In the present review, we will critically evaluate the role of pivotal matrix constituents in regulating the key steps of embryo implantation and placentation, provide up-to-date information concerning their primary mechanisms of action and discuss on their potential as a novel source of biomarkers and therapeutic targets.

Integral Roles of the TGFβ Signaling Pathway in Uterine Function and Disease

The uterus is a complex organ that requires precise signaling networks to mediate functions necessary for homeostasis and reproductive processes. The transforming growth factor β (TGFβ) superfamily regulates integral signaling pathways throughout many physiological processes, including cell proliferation, differentiation, and development. In this review, we summarize the current understanding of how the TGFβ signaling family controls key uterine functions, with a specific focus on the endometrium. These uterine functions include endometrial receptivity, implantation, decidualization, placentation, remodeling, and regeneration. Improving our understanding of the signaling networks that regulate these processes is integral to identifying, diagnosing, and treating uterine and reproductive diseases such as endometriosis, adenomyosis, recurrent pregnancy loss, and recurrent implantation failure.

Granulocyte Colony Stimulating Factor Enhances Decidualization Process of Endometrial Stromal Cells Through STAT3/HOXA10 Axis

BACKGROUND

Recurrent implantation failure (RIF) is characterized by the repeated failure of implantation, often linked to impaired endometrial receptivity. This study investigates how granulocyte colony-stimulating factor (G-CSF) promotes endometrial stromal cell decidualization.

METHODS

THESCs (human telomerase reverse transcriptase-immortalized endometrial stromal cells) were used as an in vitro cell model to induce decidualization. The effects of G-CSF on the expression of decidualization genes and apoptosis during decidualization were examined. Additionally, a chemical inhibitor of signal transducer and activator of transcription 3 (STAT3) and the small interfering RNA (siRNA) targeting Homeobox A10 (Hoxa10) were employed to explore the involvement of the STAT3/HOXA10 axis in the action of G-CSF.

RESULTS

G-CSF promoted decidualization markers expression and suppressed apoptosis in THESCs Treatment with G-CSF enhanced STAT3 activation during decidualization induction. STAT3 inhibition diminished the effects of G-CSF on decidualization marker expression and apoptosis suppression. Furthermore, it was demonstrated that G-CSF increased Hoxa10 expression in a STAT3-dependent manner. Silencing Hoxa10 abrogated the effects of G-CSF on promoting decidualization.

CONCLUSION

G-CSF enhances decidualization of endometrial stromal cells via STAT3/HOXA10 axis activation. These findings suggest that optimal G-CSF delivery strategies could improve endometrial receptivity in RIF patients.

Blastocyst-Derived Lactate as a Key Facilitator of Implantation

The blastocyst develops a unique metabolism that facilitates the creation of a specialized microenvironment at the site of implantation characterized by high levels of lactate and reduced pH. While historically perceived as a metabolic waste product, lactate serves as a signaling molecule which facilitates the invasion of surrounding tissues by cancers and promotes blood vessel formation during wound healing. However, the role of lactate in reproduction, particularly at the implantation site, is still being considered. Here, we detail the biological significance of the microenvironment created by the blastocyst at implantation, exploring the origin and significance of blastocyst-derived lactate, its functional role at the implantation site and how understanding this mediator of the maternal-fetal dialogue may help to improve implantation in assisted reproduction.

Uterus didelphys: the first case report on molecular profiling of endometrial tissue from both uterine cavities

BACKGROUND

A didelphic uterus represents a unique and infrequent congenital condition in which a woman possesses two distinct uteri, each with its own cervix. This anomaly arises due to partial or incomplete merging of the Müllerian ducts during the developmental stages in the womb. Accounting for uterine malformations, a didelphic uterus is a relatively rare condition, affecting approximately 0.5-2% of the population and is considered one of the more uncommon types of uterine abnormalities.

METHODS

This case report aims to study the physical separation in uterine didelphys and its impact on endometrial microbiome and inflammation, and the patterns of endometrial receptivity observed.

RESULTS

Endometrial receptivity analyses revealed a similar receptive state in both uteri, both in the early receptive phase. Differential markers of chronic endometritis, including CD138, and MUM1-positive cells, were observed when comparing endometrial biopsies from both uteri. The right uterus exhibited a higher prevalence of these positive cells. Regarding the microbiome, significant differences were found between the uteri, notably in the right uterus, a clear non-dominance of lactobacilli and the presence of genera such as Staphylococcus, Streptococcus, and Acinetobacter. Additionally, the right uterus presented a less 'favourable' microenvironment, a characteristic that was also reflected in the right cervix; both sites presenting less lactobacilli than the left side samples. A distinct metabolomic signature associated with the physical separation of the uteri contributed to the differences in endometrial milieu.

CONCLUSIONS

Our study revealed that physical separation, among other factors in uterus didelphys, affects the endometrial microbiome, metabolome, and inflammatory state, with significant microbiome variation observed between the uteri, although similar endometrial receptivity patterns were noted.

The relationship between serum progesterone level on the day of HCG trigger in IVF/ICSI cycles and oocyte maturation and embryo quality: a retrospective observational study

PURPOSE

Previous studies have suggested a link between serum progesterone levels on the day of the HCG trigger in IVF cycles and oocyte and embryo quality. This study aims to explore this relationship more thoroughly.

METHODS

This study included 496 infertility patients at Moloud Infertility Treatment Center, Zahedan, Iran. Statistical methods were used to assess factors such as oocyte maturation and embryo quality, fertilization rate, BMI, and gonadotropin dosage.

RESULTS

While an initial progesterone cutoff of 1.2 ng/ml was used to perform fundamental analysis, a more accurate cutoff of 1.54 ng/ml was identified, beyond which the average number of M1 oocytes significantly declined. A strong relationship was found between higher progesterone levels and a greater number of retrieved oocytes (p = 0.004), with M1 oocytes showing a similar relation. Also, BMI was significantly related to the quality of eight-cell grade B embryos (p = 0.006). However, no significant correlations were found between progesterone levels and other factors, including patient age (p = 0.327), fertilization rate (p = 0.603), or embryo quality at other stages.

CONCLUSIONS

The findings demonstrate that elevated progesterone level, particularly beyond the identified cutoff of 1.54 ng/ml, is a valuable clinical indicator of suboptimal IVF outcomes due to its negative impact on oocyte maturation.

Mitochondria remodeling during endometrial stromal cell decidualization

Upon hormonal stimulation, uterine endometrial stromal cells undergo a dramatic morpho-functional metamorphosis that allows them to secrete large amounts of matrix proteins, cytokines, and growth factors. This step, known as decidualization, is crucial for embryo implantation. We previously demonstrated how the secretory pathway is remodelled during this process. Here we show that hormonal stimulation rapidly induces the expression of many mitochondrial genes, encoded in both the mitochondrial and the nuclear genomes. Altogether, the mitochondrial network quadruples its size and establishes more contacts with the ER. This new organization results in the increased respiratory capacity of decidualized cells. These findings reveal how achieving an efficient secretory phenotype requires a radical metabolic rewiring.

Acyl-CoA long-chain synthetase 1 (ACSL1) protects the endometrium from excess palmitic acid stress during decidualization

Endometrial receptivity relies on the functional and morphological change of endometrium stromal cells (EnSCs) and epithelial cells in the secretory phase. Decidualization of ESCs and transitions in endometrium epithelial cells are crucial for successful uterine implantation and maintaining pregnancy. Accumulated data have demonstrated that decidualization is tightly coordinated by lipid metabolism. However, the lipidomic change and regulatory mechanism in uterine decidualization are still unknown. Our study showed that endometrium stromal cells and decidual stromal cells had different lipidomic profiles. Acyl-CoA long-chain synthetase 1 (ACSL1) which converts fatty acids to acyl-CoA expression was strongly elevated during decidualization. ACSL1 knockdown inhibited stromal-to-decidual cell transition and decreased the decidualization markers prolactin and Insulin-like growth factor-binding protein-1 (IGFBP1) expression through the AKT pathway. Lipid uptake was upregulated in stromal cells while lipid droplet accumulation was downregulated during decidualization. Meanwhile, silencing of ACSL1 led to impaired spare respiratory capacity, and downregulation of TFAM expression, indicating robust lipid metabolism. While palmitic acid addition impeded decidualization, overexpression of ACSL1 could partially reverse its effect. ACSL inhibitor Triacsin C significantly impeded decidualization in a three-dimensional coculture model consisting of endometrial stromal cells and epithelial cells. Knockdown of ACSL1 in stromal cells decreased the expression of the decidualization markers PAEP and SPP1 in epithelial cells. Collectively, ACSL1 is essential for uterine decidualization and protects stromal cells from excess palmitic acid stress.

Regulation of Alternative Splicing by PARP1 in HTR-8/Svneo Cells: Implications for Placental Development and Spontaneous Abortion

OBJECTIVE

Alternative splicing affects gene expression during placental development. The present study aimed to identify poly (ADP-ribose) polymerase 1 (PARP1)-regulated alternative splicing events in HTR-8/Svneo cells.

METHODS

Decidual tissues were collected from women with induced abortion and spontaneous abortion. PARP1 transcription was quantified by RT-qPCR. Small interfering RNA (siRNA) was used to knock down the PARP1 expression in HTR-8/Svneo cells. The transfection efficiency was verified by RT-qPCR and Western blotting. Total RNA was extracted, and the RNA-sequencing approach was used to identify alternative splicing events and transcriptomes. The PARP1 knockdown-induced differentially expressed genes with changes in alternative splicing events were quantified by RT-qPCR. Functional analysis, which included the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways, was performed.

RESULTS

The PARP1 mRNA expression increased in decidual tissues in the spontaneous abortion group, when compared to the induced abortion group. However, the PARP1 knockdown significantly downregulated 1491 genes and upregulated 881 genes in HTR-8/Svneo cells. Furthermore, 227 genes that underwent alternative splicing were identified, and these were differentially expressed in siPARP1 cells, when compared to siNC cells.

CONCLUSION

The functional analysis revealed that these alternative splicing genes affected the functional phenotypes of extravillous cytotrophoblasts. Furthermore, the PARP1 knockdown led to alterations in gene expression and specific alternative splicing patterns in extravillous trophoblasts.

Does Endometrial Thickness or Compaction Impact the Success of Frozen Embryo Transfer? A Cohort Study Analysis

Background: In frozen embryo transfer (FET) cycles, optimal endometrial thickness on ovulation day is typically 7-8 mm before progesterone administration. Recent studies have highlighted the significant inverse correlation between ongoing pregnancy rates and changes in endometrial thickness during the secretory phase after progesterone exposure, particularly by the day of embryo transfer (ET). This study aims to investigate how changes in endometrial thickness from the end of the proliferative phase to ET impact FET outcomes. Methods: We conducted a prospective observational cohort study involving 247 FET cycles, divided into hormonally based (102) and ovulatory-based (145) groups. Patients were monitored through transvaginal ultrasound (TVS) and blood tests. On ET day, we assessed endometrial thickness and changes compared to the last day of the proliferative phase, defining endometrial compaction as a decrease in thickness. We analyzed data to identify factors predicting cycle outcomes. Results: The study reported chemical and clinical pregnancy rates of 47.4% and 38.1%, respectively. Endometrial compaction was observed in 37.2% (92/247) of cycles, with corresponding rates of 48.9%, 32.6%, and 29.5% for chemical, clinical, and ongoing pregnancies, compared to 46.4%, 41.3%, and 28.9% in cycles without compaction. These differences were not statistically significant, and patterns of endometrial thickness change were similar across different FET protocols and progesterone exposure durations. Conclusions: The main factors influencing cycle outcomes were maternal age, embryo transfer protocol, and endometrial thickness on ET day, with endometrial compaction showing no correlation with improved outcomes.

Maternal dietary olive oil protects diabetic rat offspring from impaired uterine decidualization

INTRODUCTION

Maternal diabetes increases the risk of adverse maternal, perinatal and offspring outcomes. This study aimed to address whether alterations in uterine decidualization are programmed in the prepubertal offspring from diabetic rats fed diets enriched or not in extra virgin olive oil (EVOO).

METHODS

Control and mild pregestational diabetic female rats (F0) were mated with control males and fed diets enriched or not with 6 % EVOO during pregnancy. Offspring (F1) were evaluated on postnatal day 30, after induction of uterine decidualization (PMSG 50 IU- hCG 50 IU). Signaling pathways involved in decidualization, including prolactin, PPAR and mTOR pathways as well as microRNAs (miRs) regulating these pathways were evaluated by Western blot or qPCR in the decidualized uteri.

RESULTS

The offspring from diabetic rats evidenced reduced prolactin and prolactin receptor levels in the decidualized uteri. Additionally, these tissues showed increased PPARγ levels and reduced levels of its negative regulators miR-19b and miR-155. MiR-21, a microRNA that targets both PPARα and mTOR pathway regulators was reduced, whereas PPARα, PTEN and FOXO1 mRNA levels were increased in the decidualized uteri of the offspring from diabetic rats. The mTOR pathway activity was reduced in the decidualized uteri of the offspring from diabetic rats. Most of the observed alterations were prevented by the EVOO-enriched maternal diet.

DISCUSSION

Impaired pathways relevant to decidualization are programmed in the uteri of prepubertal offspring from diabetic dams, alterations capable of being prevented by maternal diets enriched in EVOO.

Investigating the Imperative Role of microRNAs Expression in Human Embryo Implantation: A Narrative Review Based on Recent Evidence

BACKGROUND/OBJECTIVES

Embryo implantation is a highly complex process that requires the precise regulation of numerous molecules to be orchestrated successfully. Micro RNAs (miRNAs) are small non-coding RNAs that regulate gene expression and play a crucial role in the regulation of embryo implantation. This article aims to summarize the key findings of the literature regarding the role of miRNAs in human embryo implantation, emphasizing their involvement in critical stages such as decidualization, endometrial receptivity and trophoblast adhesion.

METHODS

This review includes primary research articles from the past decade. The studies utilize a range of experimental methodologies, including gene expression analysis and in vitro studies.

RESULTS

MicroRNAs, like miR-320a, miR-149, and miR30d secreted by preimplantation embryos and blastocysts significantly influence endometrial receptivity by promoting essential cellular processes, such as cell migration and trophoblast cell attachment, while others-miR17-5p, miR-193-3p, miR-372, and miR-542-3p-secreted from the endometrium regulate the decidualization phase. During the apposition and adhesion phases, miRNAs play a complex role by promoting, for example, miR-23b-3p, and inhibiting-as do miR-29c and miR-519d-3p-important biological pathways of these stages. During invasion, miR-26a-5p and miR-125-5p modulate important genes.

CONCLUSIONS

This review underscores the critical impact of miRNAs in the regulation of embryo implantation and early pregnancy. The ability of miRNAs to modulate gene expression at various stages of reproduction presents promising therapeutic avenues for improving assisted reproductive technologies outcomes and addressing infertility. Further research into miRNA-based diagnostic tools and therapeutic strategies is essential to enhance our understanding of their role in reproductive health and to exploit their potential for clinical applications.

Reproductive and developmental implications of micro- and nanoplastic internalization: Recent advances and perspectives

A growing body of evidence exhibits the ubiquitous presence and accumulation of micro- and nanoplastics (MNPs) in the air, drinking water, food, and even inside the body, which has raised concerns about their potential impact on reproductive and developmental health. To comprehensively examine the current state of knowledge regarding MNPs-induced reproductive and developmental toxicity, we conducted this systematic review by focusing on the prevalence of MNPs determined in reproductive tissues and their influences on parental reproduction and offspring development. Our findings demonstrate the detection of MNPs in various human reproductive tissues, including semen, placenta, and ovarian follicular fluid, as well as in reproductive tissues of diverse animal species. We show a potential relationship between MNP exposure and increased prevalence of infertility and adverse pregnancy outcomes based on the fact that MNPs exert detrimental effects on reproductive parameters, including sperm quality, ovarian function, and steroidogenesis. In male reproductive systems, MNPs disrupt testicular tissue structure, impair reproductive endocrinology, and reduce sperm quality. In females, MNPs affect ovarian tissue structure and function, interfere with hormone secretion, and impact the endometrium and embryo implantation. Additionally, MNPs cause developmental toxicity in animal models, affecting embryonic development and offspring health, and produce transgenerational effects. Notably, in-depth literature study suggests a crucial role for oxidative stress, inflammation, and epigenetic modification in MNPs-induced toxicity. In conclusion, we integrated systematic knowledge on MNPs-induced reproductive and developmental toxicity, and the systematic finding underscores future study to fully elucidate the risks posed by MNPs to reproductive and developmental health and to inform policy decisions and public health interventions aimed at mitigating their harmful effects.

Effect of environmental air pollutants on placental function and pregnancy outcomes: a molecular insight

Air pollution has become a major health concern, particularly for vulnerable populations such as the elderly, children, and pregnant women. Studies have reported a strong association between prenatal exposure to air pollutants and adverse pregnancy outcomes, including lower birth weight, reduced fetal growth, and an increased frequency of preterm births. This review summarizes the harmful effects of air pollutants, such as particulate matter, on pregnancy and outlines the mechanistic details associated with these adverse outcomes. Particulate pollutant matter may be able to cross the placenta barrier, and alterations in placental functions are central to the detrimental effects of these pollutants. In addition to associations with preeclampsia and gestational hypertension, air pollutants also induce oxidative stress, inflammation, and epigenetic alteration in the placenta. These pollutants can also affect placental homeostasis and endocrine function, contributing to pregnancy complications and possible transgenerational effects. Prenatal air pollution exposure has been linked to reduced cognitive and motor function in infants and newborns, increasing the predisposition to autism spectrum disorders and other neuropsychiatric disorders. This review also summarizes the use of various animal models to study the harmful effects of air pollution on pregnancy and postnatal outcomes. These findings provide valuable insight into the molecular events associated with the process and can aid in risk mitigation and adopting safety measures. Implementing effective environmental protocols and taking appropriate steps may reduce the global disease burden, particularly for developing nations with poor regulatory compliance and large populations of pregnant women.

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.

In-utero transfer of decidualized endometrial stromal cells increases the frequency of regulatory T cells and normalizes the abortion rate in the CBA/J × DBA/2 abortion model

Introduction

Failure to adequate decidualization leads to adverse pregnancy outcomes including pregnancy loss. Although there are plenty of reports underscoring immune dysfunction as the main cause of abortion in CBA/J females mated with DBA/2 males (CBA/J × DBA/2), little is known about the potential role of impaired endometrial decidualization.

Methods

Endometrial stromal cells (ESCs) from CBA/J mice were in-vitro decidualized, and the proteome profile of the secretome was investigated by membrane-based array. CBA/J mice were perfused In-utero with either decidualized ESCs (C×D/D), undecidualized ESCs (C×D/ND), or PBS (C×D/P) 12 days before mating with DBA/2 males. Control mice were not manipulated and were mated with male DBA/2 (C×D) or Balb/c (C×B) mice. On day 13.5 of pregnancy, reproductive parameters were measured. In-vivo tracking of EdU-labeled ESCs was performed using fluorescence microscopy. The frequency of regulatory T cells (Tregs) in paraaortic/renal and inguinal lymph nodes was measured by flow cytometry. The proliferation of pregnant CBA/J splenocytes in response to stimulation with DBA/2 splenocytes was assessed by 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE) flow cytometry.

Results

In C×D/D mice, the resorption rate was reduced to match that seen in the C×B group. Intrauterine perfused ESCs appeared in uterine stroma after 2 days, which remained there for at least 12 days. There was no difference in the number of implantation sites and embryo weight across all groups. The frequency of Tregs in the inguinal lymph nodes was similar across all groups, but it increased in the paraaortic/renal lymph nodes of C×D/D mice to the level found in C×B mice. No significant changes were observed in the proliferation of splenocytes from pregnant C×D/D compared to those of the C×D group in response to stimulation with DBA/2 splenocytes. Decidualization of ESCs was associated with a profound alteration in ESC secretome exemplified by alteration in proteins involved in extracellular matrix (ECM) remodeling, response to inflammation, senescence, and immune cell trafficking.

Discussion

Our results showed that the deficiency of Tregs is not the primary driver of abortion in the CBA/J × DBA/2 model and provided evidence that impaired endometrial decidualization probably triggers endometrial immune dysfunction and abortion in this model.

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.