Dynamic changes in AI-based analysis of endometrial cellular composition: Analysis of PCOS and RIF endometrium

Background

The human endometrium undergoes a monthly cycle of tissue growth and degeneration. During the mid-secretory phase, the endometrium establishes an optimal niche for embryo implantation by regulating cellular composition (e.g., epithelial and stromal cells) and differentiation. Impaired endometrial development observed in conditions such as polycystic ovary syndrome (PCOS) and recurrent implantation failure (RIF) contributes to infertility. Surprisingly, despite the importance of the endometrial lining properly developing prior to pregnancy, precise measures of endometrial cellular composition in these two infertility-associated conditions are entirely lacking. Additionally, current methods for measuring the epithelial and stromal area have limitations, including intra- and inter-observer variability and efficiency.

Methods

We utilized a deep-learning artificial intelligence (AI) model, created on a cloud-based platform and developed in our previous study. The AI model underwent training to segment both areas populated by epithelial and stromal endometrial cells. During the training step, a total of 28.36 mm2 areas were annotated, comprising 2.56 mm2 of epithelium and 24.87 mm2 of stroma. Two experienced pathologists validated the performance of the AI model. 73 endometrial samples from healthy control women were included in the sample set to establish cycle phase-dependent dynamics of the endometrial epithelial-to-stroma ratio from the proliferative (PE) to secretory (SE) phases. In addition, 91 samples from PCOS cases, accounting for the presence or absence of ovulation and representing all menstrual cycle phases, and 29 samples from RIF patients on day 5 after progesterone administration in the hormone replacement treatment cycle were also included and analyzed in terms of cellular composition.

Results

Our AI model exhibited reliable and reproducible performance in delineating epithelial and stromal compartments, achieving an accuracy of 92.40% and 99.23%, respectively. Moreover, the performance of the AI model was comparable to the pathologists' assessment, with F1 scores exceeding 82% for the epithelium and >96% for the stroma. Next, we compared the endometrial epithelial-to-stromal ratio during the menstrual cycle in women with PCOS and in relation to endometrial receptivity status in RIF patients. The ovulatory PCOS endometrium exhibited epithelial cell proportions similar to those of control and healthy women's samples in every cycle phase, from the PE to the late SE, correlating with progesterone levels (control SE, r2 = 0.64, FDR < 0.001; PCOS SE, r2 = 0.52, FDR < 0.001). The mid-SE endometrium showed the highest epithelial percentage compared to both the early and late SE endometrium in both healthy women and PCOS patients. Anovulatory PCOS cases showed epithelial cellular fractions comparable to those of PCOS cases in the PE (Anovulatory, 14.54%; PCOS PE, 15.56%, p = 1.00). We did not observe significant differences in the epithelial-to-stroma ratio in the hormone-induced endometrium in RIF patients with different receptivity statuses.

Conclusion

The AI model rapidly and accurately identifies endometrial histology features by calculating areas occupied by epithelial and stromal cells. The AI model demonstrates changes in epithelial cellular proportions according to the menstrual cycle phase and reveals no changes in epithelial cellular proportions based on PCOS and RIF conditions. In conclusion, the AI model can potentially improve endometrial histology assessment by accelerating the analysis of the cellular composition of the tissue and by ensuring maximal objectivity for research and clinical purposes.

Advances in the use of organoids in endometrial diseases

The endometrium undergoes cyclical changes in response to hormones and there is a certain degree of heterogeneity among individuals. In vivo identification of the physiologic changes of the endometrium and the pathologic process of related diseases is challenging. There have been recent advances in the use of organoids that mimic the characteristics of the corresponding organs and the morphologic, functional, and personalized characteristics involved in different stages of diseases. In this paper, we discuss the process of creating endometrial organoids, cell sources, types of extracellular matrices, and their application in the study of physiologic endometrial states and various diseases.

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.

Endometrial Proliferative Phase-Centered View of Transcriptome Dynamics across the Menstrual Cycle

The endometrium, the inner mucosal lining of the uterus, undergoes complex molecular and cellular changes across the menstrual cycle in preparation for embryo implantation. Transcriptome-wide analyses have mainly been utilized to study endometrial receptivity, the prerequisite for successful implantation, with most studies, so far, comparing the endometrial transcriptomes between (i) secretory and proliferative endometrium or (ii) mid-secretory and early secretory endometrium. In the current study, we provide a complete transcriptome description of the endometrium across the entire menstrual cycle and, for the first time, comprehensively characterize the proliferative phase of the endometrium. Our temporal transcriptome analysis includes five time points including the mid-proliferative, late proliferative (peri-ovulatory phase), early secretory, mid-secretory, and late secretory phases. Thus, we unveil exhaustively the transitions between the consecutive proliferative and secretory phases, highlighting their unique gene expression profiles and possible distinct biological functions. The transcriptome analysis reveals many differentially expressed genes (DEGs) across the menstrual cycle, most of which are phase-specific. As an example of coordinated gene activity, the expression profile of histone-encoding genes within the HIST cluster on chromosome 6 shows an increase in cluster activity during the late proliferative and a decline during the mid-secretory phase. Moreover, numerous DEGs are shared among all phases. In conclusion, in the current study, we delineate the endometrial proliferative phase-centered view of transcriptome dynamics across the menstrual cycle. Our data analysis highlights significant transcriptomic and functional changes occurring during the late proliferative phase-an essential transition point from the proliferative phase to the secretory phase. Future studies should explore how the biology of the late proliferative phase endometrium impacts the achievement of mid-secretory endometrial receptivity or contributes to molecular aberrations leading to embryo implantation failure.

The functional roles of protein glycosylation in human maternal-fetal crosstalk

BACKGROUND

The establishment of maternal-fetal crosstalk is vital to a successful pregnancy. Glycosylation is a post-translational modification in which glycans (monosaccharide chains) are attached to an organic molecule. Glycans are involved in many physiological and pathological processes. Human endometrial epithelium, endometrial gland secretions, decidual immune cells, and trophoblasts are highly enriched with glycoconjugates and glycan-binding molecules important for a healthy pregnancy. Aberrant glycosylation in the placenta and uterus has been linked to repeated implantation failure and various pregnancy complications, but there is no recent review summarizing the functional roles of glycosylation at the maternal-fetal interface and their associations with pathological processes.

OBJECTIVE AND RATIONALE

This review aims to summarize recent findings on glycosylation, glycosyltransferases, and glycan-binding receptors at the maternal-fetal interface, and their involvement in regulating the biology and pathological conditions associated with endometrial receptivity, placentation and maternal-fetal immunotolerance. Current knowledge limitations and future insights into the study of glycobiology in reproduction are discussed.

SEARCH METHODS

A comprehensive PubMed search was conducted using the following keywords: glycosylation, glycosyltransferases, glycan-binding proteins, endometrium, trophoblasts, maternal-fetal immunotolerance, siglec, selectin, galectin, repeated implantation failure, early pregnancy loss, recurrent pregnancy loss, preeclampsia, and fetal growth restriction. Relevant reports published between 1980 and 2023 and studies related to these reports were retrieved and reviewed. Only publications written in English were included.

OUTCOMES

The application of ultrasensitive mass spectrometry tools and lectin-based glycan profiling has enabled characterization of glycans present at the maternal-fetal interface and in maternal serum. The endometrial luminal epithelium is covered with highly glycosylated mucin that regulates blastocyst adhesion during implantation. In the placenta, fucose and sialic acid residues are abundantly presented on the villous membrane and are essential for proper placentation and establishment of maternal-fetal immunotolerance. Glycan-binding receptors, including selectins, sialic-acid-binding immunoglobulin-like lectins (siglecs) and galectins, also modulate implantation, trophoblast functions and maternal-fetal immunotolerance. Aberrant glycosylation is associated with repeated implantation failure, early pregnancy loss and various pregnancy complications. The current limitation in the field is that most glycobiological research relies on association studies, with few studies revealing the specific functions of glycans. Technological advancements in analytic, synthetic and functional glycobiology have laid the groundwork for further exploration of glycans in reproductive biology under both physiological and pathological conditions.

WIDER IMPLICATIONS

A deep understanding of the functions of glycan structures would provide insights into the molecular mechanisms underlying their involvement in the physiological and pathological regulation of early pregnancy. Glycans may also potentially serve as novel early predictive markers and therapeutic targets for repeated implantation failure, pregnancy loss, and other pregnancy complications.

Using organoids to investigate human endometrial receptivity

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

Implementing a preimplantation proteomic approach to advance assisted reproduction technologies in the framework of predictive, preventive, and personalized medicine

The evolution of the field of assisted reproduction technology (ART) in the last 40 years has significantly contributed to the management of global infertility. Despite the great numbers of live births that have been achieved through ART, there is still potential for increasing the success rates. As a result, there is a need to create optimum conditions in order to increase ART efficacy. The selection of the best sperm, oocyte, and embryo, as well as the achievement of optimal endometrial receptivity, through the contribution of new diagnostic and treatment methods, based on a personalized proteomic approach, may assist in the attainment of this goal. Proteomics represent a powerful new technological development, which seeks for protein biomarkers in human tissues. These biomarkers may aid to predict the outcome, prevent failure, and monitor in a personalized manner in vitro fertilization (IVF) cycles. In this review, we will present data from studies that have been conducted in the search for such biomarkers in order to identify proteins related to good sperm, oocyte, and embryo quality, as well as optimal endometrial receptivity, which may later lead to greater results and the desirable ART outcome.

Non-Invasive and Mechanism-Based Molecular Assessment of Endometrial Receptivity During the Window of Implantation: Current Concepts and Future Prospective Testing Directions

Suboptimal endometrial receptivity and altered embryo-endometrial crosstalk account for approximately two-thirds of human implantation failures. Current tests of the window of implantation, such as endometrial thickness measurements and the endometrial receptivity assay, do not consistently improve clinical outcomes as measured by live birth rates. Understanding the mechanisms regulating the endometrial receptivity during the window of implantation is a critical step toward developing clinically meaningful tests. In this narrative review, the available literature is evaluated regarding mechanisms that regulate the endometrial receptivity during the window of implantation and the current tests developed. Overall, both animal and human studies point to five possible and interrelated mechanisms regulating the endometrial window of implantation: suitable synchrony between endometrial cells, adequate synchrony between the endometrium and the embryo, standard progesterone signaling and endometrial responses to progesterone, silent genetic variations, and typical morphological characteristics of the endometrial glands. The biological basis of current clinical markers or tests of window of implantation is poor. Future studies to elucidate the mechanisms shaping the window of implantation and to investigate the potential markers based on these mechanisms are required. In addition, molecular testing of the endometrium at single-cell resolution should be an initial step toward developing clinically meaningful tests for the optimal window of implantation. As understanding of the optimal window of implantation continues to evolve, one can envision the future development of non-invasive, mechanism-based testing of the window of implantation.

Combined expression of HOXA11 and CD10 identifies endometriosis versus normal tissue and tumors

The gold standard for diagnosing endometriosis is by laparoscopic visual demonstration of ectopic endometrial lesions outside the uterus, preferably verified by biopsy and microscopical examination. Molecular markers to facilitate the microscopical diagnosis of endometriosis and for distinguishing endometriosis from other benign and malignant lesions are lacking. Our aim was to test and validate an immunohistochemical antibody panel for improved diagnostic accuracy of endometriosis. Both CD10 and HOXA11 have been implicated in regulation of endometrial homeostasis. Here we have analyzed the expression pattern of these two proteins using immunohistochemistry on human tissues in a tissue microarray format. CD10 and HOXA11 expression in endometriosis lesions were compared to expression patterns in a range of normal tissues and in primary- and metastatic lesions of endometrial-, cervical- and ovarian cancer. HOXA11 and CD10 were expressed in 98% and 91% of endometriosis lesions and the combined double-positive expression profile of both HOXA11 and CD10 was highly sensitive for ectopic endometrial tissue (90%). The specificity and sensitivity for this double-positive signature in endometriosis was significantly different from all investigated tissues, cancers and metastases except normal, eutopic endometrial- and cervical mucosa. The combination of HOXA11 and CD10 expression profiles provides a useful tool to identify ectopic endometrial tissue and for distinguishing endometriosis from various types of gynecological malignancies and metastases.

Profound architectural and functional readjustments of the secretory pathway in decidualization of endometrial stromal cells

Certain cell types must expand their exocytic pathway to guarantee efficiency and fidelity of protein secretion. A spectacular case is offered by decidualizing human endometrial stromal cells (EnSCs). In the midluteal phase of the menstrual cycle, progesterone stimulation induces proliferating EnSCs to differentiate into professional secretors releasing proteins essential for efficient blastocyst implantation. Here, we describe the architectural rearrangements of the secretory pathway of a human EnSC line (TERT-immortalized human endometrial stromal cells (T-HESC)). As in primary cells, decidualization entails proliferation arrest and the coordinated expansion of the entire secretory pathway without detectable activation of unfolded protein response (UPR) pathways. Decidualization proceeds also in the absence of ascorbic acid, an essential cofactor for collagen biogenesis, despite also the secretion of some proteins whose folding does not depend on vitamin C is impaired. However, even in these conditions, no overt UPR induction can be detected. Morphometric analyses reveal that the exocytic pathway does not increase relatively to the volume of the cell. Thus, differently from other cell types, abundant production is guaranteed by a coordinated increase of the cell size following arrest of proliferation.

Analysis of the transcriptome of bovine endometrial cells isolated by laser micro-dissection (2): impacts of post-partum negative energy balance on stromal, glandular and luminal epithelial cells

BACKGROUND

In post-partum dairy cows, the energy needs to satisfy high milk production induces a status of more or less pronounced Negative Energy Balance (NEB). NEB associated with fat mobilization impairs reproductive function. In a companion paper, we described constitutive gene expression in the three main endometrial cell types (stromal, glandular and luminal epithelial cells) isolated by laser capture micro-dissection (LCM) showing the specificities of their transcriptomic profiles. This study investigates the specific impact of NEB on gene expression in these cells around 80 days after parturition at day 15 of the oestrus cycle and describes their specific response to NEB.

RESULTS

Following the description of their constitutive expression, the transcriptome profiles obtained by RNA sequencing of the three cells types revealed that differences related to the severity of NEB altered mainly specific patterns of expression related to individual cell types. Number of differentially expressed genes between severe NEB (SNEB) and mild NEB (MNEB) cows was higher in ST than in LE and GE, respectively. SNEB was associated with differential expression of genes coding for proteins involved in metabolic processes and embryo-maternal interactions in ST. Under-expression of genes encoding proteins with functions related to cell structure was found in GE whereas genes encoding proteins participating in pro-inflammatory pathways were over-expressed. Genes associated to adaptive immunity were under-expressed in LE.

CONCLUSION

The severity of NEB after calving is associated with changes in gene expression around 80 days after parturition corresponding to the time of breeding. Specific alterations in GEs are associated with activation of pro-inflammatory mechanisms. Concomitantly, changes in the expression of genes encoding proteins involved in cell interactions and maternal recognition of pregnancy takes place in ST. The combination of these effects possibly altering the uterine environment and embryo maternal interactions may negatively influence the establishment of pregnancy.

Purinergic Signaling in Endometriosis-Associated Pain

Endometriosis is an estrogen-dependent gynecological disease, with an associated chronic inflammatory component, characterized by the presence of endometrial tissue outside the uterine cavity. Its predominant symptom is pain, a condition notably altering the quality of life of women with the disease. This review is intended to exhaustively gather current knowledge on purinergic signaling in endometriosis-associated pain. Altered extracellular ATP hydrolysis, due to changes in ectonucleotidase activity, has been reported in endometriosis; the resulting accumulation of ATP in the endometriotic microenvironment points to sustained activation of nucleotide receptors (P2 receptors) capable of generating a persistent pain message. P2X3 receptor, expressed in sensory neurons, mediates nociceptive, neuropathic, and inflammatory pain, and is enrolled in endometriosis-related pain. Pharmacological inhibition of P2X3 receptor is under evaluation as a pain relief treatment for women with endometriosis. The role of other ATP receptors is also discussed here, e.g., P2X4 and P2X7 receptors, which are involved in inflammatory cell-nerve and microglia-nerve crosstalk, and therefore in inflammatory and neuropathic pain. Adenosine receptors (P1 receptors), by contrast, mainly play antinociceptive and anti-inflammatory roles. Purinome-targeted drugs, including nucleotide receptors and metabolizing enzymes, are potential non-hormonal therapeutic tools for the pharmacological management of endometriosis-related pain.

In vitro models of the human endometrium: evolution and application for women's health

The endometrium is the inner lining of the uterus that undergoes complex regeneration and differentiation during the human menstrual cycle. The process of endometrial shedding, regeneration, and differentiation is driven by ovarian steroid hormones and prepares the endometrium and intrauterine environment for embryo implantation and pregnancy establishment. Endometrial glands and their secretions are essential for pregnancy establishment, and cross talk between the glandular epithelium and stromal cells appears vital for decidualization and placental development. Despite being crucial, the biology of the human endometrium during pregnancy establishment and most of pregnancy is incomplete, given the ethical and practical limitations of obtaining and studying endometrium from pregnant women. As such, in vitro models of the human endometrium are required to fill significant gaps in understanding endometrial biology. This review is focused on the evolution and development of in vitro three-dimensional models of the human endometrium and provides insight into the challenges and promises of those models to improve women's reproductive health.

Single-cell transcriptomic atlas of the human endometrium during the menstrual cycle

In a human menstrual cycle the endometrium undergoes remodeling, shedding and regeneration, all of which are driven by substantial gene expression changes in the underlying cellular hierarchy. Despite its importance in human fertility and regenerative biology, our understanding of this unique type of tissue homeostasis remains rudimentary. We characterized the transcriptomic transformation of human endometrium at single-cell resolution across the menstrual cycle, resolving cellular heterogeneity in multiple dimensions. We profiled the behavior of seven endometrial cell types, including a previously uncharacterized ciliated cell type, during four major phases of endometrial transformation, and found characteristic signatures for each cell type and phase. We discovered that the human window of implantation opens with an abrupt and discontinuous transcriptomic activation in the epithelia, accompanied with a widespread decidualization feature in the stromal fibroblasts. Our study provides a high-resolution molecular and cellular characterization of human endometrial transformation across the menstrual cycle, providing insights into this essential physiological process.

Rab Proteins: Insights into Intracellular Trafficking in Endometrium

Rab proteins belong to the Ras superfamily of small monomeric GTPases. These G proteins are the main controllers of vesicular transport in every tissue, among them, the endometrium. They are in charge of to the functional subcellular compartmentalization and cargo transport between organelles and the plasma membrane. In turn, intracellular trafficking contributes to endometrial changes during the menstrual cycle, secretion to the uterine fluid, and trophoblast implantation; however, few reports analyze the role of Rab proteins in the uterus. In general, Rab proteins control the release of cytokines, growth factors, enzymes, hormones, cell adhesion molecules, and mucus. Further, the secretion of multiple compounds into the uterine cavity is required for successful implantation. Therefore, alterations in Rab-controlled intracellular transport likely impair secretory processes to the uterine fluid that may correlate with abnormal endometrial development and failed reproductive outcomes. Overall, they could explain recurrent miscarriages, female infertility, and/or assisted reproductive failure. Interestingly, estrogen (E2) and progesterone (P) regulate gene expression of Rab proteins involved in secretory pathways. This review aims to gather information regarding the role of Rab proteins and intracellular trafficking in the endometrium during the different menstrual phases, and in the generation of a receptive stage for embryo implantation, modulated by E2 and P. This knowledge might be useful for the development of novel reproductive therapies that overcome low implantation rates of assisted reproductive procedures.

Jupiter microtubule-associated homolog 1 (JPT1): A predictive and pharmacodynamic biomarker of metformin response in endometrial cancers

Preoperative use of metformin in obese women with endometrioid endometrial cancer (EEC) reduces tumor proliferation and inhibits the mammalian target of rapamycin pathway, though is only effective in select cases. This study sought to identify a predictive and/or pharmacodynamic proteomic signature of metformin response to tailor its pharmacologic use. Matched pre‐ and post‐metformin‐treated tumor tissues from a recently completed preoperative window trial of metformin in EEC patients (ClinicalTrials.gov: NCT01911247) were analyzed by mass spectrometry (MS)‐based proteomic and immunohistochemical analyses. Jupiter microtubule‐associated homolog 1 (JPT1) was significantly elevated in metformin responders (n = 13) vs nonresponders (n = 7), and found to decrease in abundance in metformin responders following treatment; observations that were verified by immunohistochemical staining for JPT1. Metformin response and loss of JPT1 were assessed in RL95‐2 and ACI‐181 endometrial cancer (EC) cell lines. We further identified that silencing of JPT1 abundance does not alter cellular response to metformin or basal cell proliferation, but that JPT1 abundance does decrease in response to metformin treatment in RL95‐2 and ACI‐181 EC cell lines. These data suggest that JPT1 represents a predictive and pharmacodynamic biomarker of metformin response that, if validated in larger patient populations, may enable preoperative EEC patient stratification to metformin treatment and the ability to monitor patient response.

Impaired Expression of Ectonucleotidases in Ectopic and Eutopic Endometrial Tissue Is in Favor of ATP Accumulation in the Tissue Microenvironment in Endometriosis

Endometriosis is a prevalent disease defined by the presence of endometrial tissue outside the uterus. Adenosine triphosphate (ATP), as a proinflammatory molecule, promotes and helps maintain the inflammatory state of endometriosis. Moreover, ATP has a direct influence on the two main symptoms of endometriosis: infertility and pain. Purinergic signaling, the group of biological responses to extracellular nucleotides such as ATP and nucleosides such as adenosine, is involved in the biology of reproduction and is impaired in pathologies with an inflammatory component such as endometriosis. We have previously demonstrated that ectonucleotidases, the enzymes regulating extracellular ATP levels, are active in non-pathological endometria, with hormone-dependent changes in expression throughout the cycle. In the present study we have focused on the expression of ectonucleotidases by means of immunohistochemistry and in situ activity in eutopic and ectopic endometrial tissue of women with endometriosis, and we compared the results with endometria of women without the disease. We have demonstrated that the axis CD39-CD73 is altered in endometriosis, with loss of CD39 and CD73 expression in deep infiltrating endometriosis, the most severe, and most recurring, endometriosis subtype. Our results indicate that this altered expression of ectonucleotidases in endometriosis boosts ATP accumulation in the tissue microenvironment. An important finding is the identification of the nucleotide pyrophophatase/phosphodiesterase 3 (NPP3) as a new histopathological marker of the disease since we have demonstrated its expression in the stroma only in endometriosis, in both eutopic and ectopic tissue. Therefore, targeting the proteins directly involved in ATP breakdown could be an appropriate approach to consider in the treatment of endometriosis.

Self-renewing endometrial epithelial organoids of the human uterus

The human endometrium is essential in providing the site for implantation and maintaining the growth and survival of the conceptus. An unreceptive endometrium and disrupted maternal-conceptus interactions can cause infertility due to pregnancy loss or later pregnancy complications. Despite this, the role of uterine glands in first trimester human pregnancy is little understood. An established organoid protocol was used to generate and comprehensively analyze 3-dimensional endometrial epithelial organoid (EEO) cultures from human endometrial biopsies. The derived EEO expand long-term, are genetically stable, and can be cryopreserved. Using endometrium from 2 different donors, EEO were derived and then treated with estrogen (E2) for 2 d or E2 and medroxyprogesterone acetate (MPA) for 6 d. EEO cells were positive for the gland marker, FOXA2, and exhibited appropriate hormonal regulation of steroid hormone receptor expression. Real-time qPCR and bulk RNA-sequencing analysis revealed effects of hormone treatment on gene expression that recapitulated changes in proliferative and secretory phase endometrium. Single-cell RNA sequencing analysis revealed that several different epithelial cell types are present in the EEO whose proportion and gene expression changed with hormone treatment. The EEO model serves as an important platform for studying the physiology and pathology of the human endometrium.

Expression of ENPP3 in human cyclic endometrium: a novel molecule involved in embryo implantation

Ectonucleotide pyrophosphatase-phosphodiesterase 3 (ENPP3), a protein detected in the human uterus, has been found to play an important role in the development and invasion of tumours. It was recently discovered that ENPP3 was upregulated during the window of implantation in the human endometrium but its functional relevance remains elusive. The objective was to determine ENPP3 expression in human endometrium and its roles in endometrial receptivity and embryo implantation. ENPP3 expression was analysed using immunohistochemistry and western blot assay. The effects of ENPP3 on embryo implantation were evaluated using a BeWo cell (a human choriocarcinoma cell line) spheroid attachment assay and BeWo cells were dual cultured with Ishikawa cells transfected with lentiviral vectors (LV5-NC or LV5-ENPP3) to mimic embryo implantation in a Transwell model. The effects of endometrial ENPP3 on factors related to endometrial receptivity were also determined. The results showed that ENPP3 was expressed in human endometrial epithelial cells and its expression levels changed during the menstrual cycle, peaking in the mid-secretory phase, corresponding to the time of embryo implantation. The overexpression of endometrial ENPP3 not only increased the embryo implantation rate but also had positive effects on the expression of factors related to endometrial receptivity in human endometrial cells. The results indicate that ENPP3 levels undergo cyclic changes in the endometrium and affect embryo adhesion and invasion via altering the expression of implantation factors in the human endometrium. Therefore, ENPP3 may play an important role in embryo implantation and may be a unique biomarker of endometrial receptivity.

Discovery of non-invasive biomarkers for the diagnosis of endometriosis

Background

Endometriosis is a common gynaecological disorder affecting 5-10% of women of reproductive age who often experience chronic pelvic pain and infertility. Definitive diagnosis is through laparoscopy, exposing patients to potentially serious complications, and is often delayed. Non-invasive biomarkers are urgently required to accelerate diagnosis and for triaging potential patients for surgery.

Methods

This retrospective case control biomarker discovery and validation study used quantitative 2D-difference gel electrophoresis and tandem mass tagging-liquid chromatography-tandem mass spectrometry for protein expression profiling of eutopic and ectopic endometrial tissue samples collected from 28 cases of endometriosis and 18 control patients undergoing surgery for investigation of chronic pelvic pain without endometriosis or prophylactic surgery. Samples were further sub-grouped by menstrual cycle phase. Selected differentially expressed candidate markers (LUM, CPM, TNC, TPM2 and PAEP) were verified by ELISA in a set of 87 serum samples collected from the same and additional women. Previously reported biomarkers (CA125, sICAM1, FST, VEGF, MCP1, MIF and IL1R2) were also validated and diagnostic performance of markers and combinations established.

Results

Cycle phase and endometriosis-associated proteomic changes were identified in eutopic tissue from over 1400 identified gene products, yielding potential biomarker candidates. Bioinformatics analysis revealed enrichment of adhesion/extracellular matrix proteins and progesterone signalling. The best single marker for discriminating endometriosis from controls remained CA125 (AUC = 0.63), with the best cross-validated multimarker models improving the AUC to 0.71-0.81, depending upon menstrual cycle phase and control group.

Conclusions

We have identified menstrual cycle- and endometriosis-associated protein changes linked to various cellular processes that are potential biomarkers and that provide insight into the biology of endometriosis. Our data indicate that the markers tested, whilst not useful alone, have improved diagnostic accuracy when used in combination and demonstrate menstrual cycle specificity. Tissue heterogeneity and blood contamination is likely to have hindered biomarker discovery, whilst a small sample size precludes accurate determination of performance by cycle phase. Independent validation of these biomarker panels in a larger cohort is however warranted, and if successful, they may have clinical utility in triaging patients for surgery.

Proteomics of reproduction: Prospects and perspectives

In recent years, proteomics has been used widely in reproductive research in order to understand the molecular mechanisms related to gametes at the cellular level and the role of proteins involved in fertilization. Network and pathway analysis using bioinformatic tools have paved way to obtain a wider picture on the possible pathways associated with the key differentially expressed proteins (DEPs) and its implication in various infertility scenarios. A brief overview of advanced techniques and bioinformatic tools used for reproductive proteomics is presented. Key findings of proteomic-based studies on male and female reproduction are also presented. Furthermore, the chapter sheds light on the cellular pathways and potential biomarkers associated with male and female infertility. Proteomics coupled with bioinformatic analysis provides an ideal platform for non-invasive management of infertility in couples.

Race-specific molecular alterations correlate with differential outcomes for black and white endometrioid endometrial cancer patients

BACKGROUND

The objective of this study was to identify molecular alterations associated with disease outcomes for white and black patients with endometrioid endometrial cancer (EEC).

METHODS

EEC samples from black (n = 17) and white patients (n = 13) were analyzed by proteomics (liquid chromatography-tandem mass spectrometry) and transcriptomics (RNA-seq). Coordinate alterations were validated with RNA-seq data from black (n = 49) and white patients (n = 216). Concordantly altered candidates were further tested for associations with race-specific progression-free survival (PFS) in black (n = 64) or white patients (n = 267) via univariate and multivariate Cox regression modeling and log-rank testing.

RESULTS

Discovery analyses revealed significantly altered candidate proteins and transcripts between black and white patients, suggesting modulation of tumor cell viability in black patients and cell death signaling in black and white patients. Eighty-nine candidates were validated as altered between these patient cohorts, and a subset significantly correlated with differential PFS. White-specific PFS candidates included serpin family A member 4 (SERPINA4; hazard ratio [HR], 0.89; Wald P value = .02), integrin subunit α3 (ITGA3; HR, 0.76; P = .03), and Bet1 Golgi vesicular membrane trafficking protein like (BET1L; HR, 0.48; P = .04). Black-specific PFS candidates included family with sequence similarity 228 member B (FAM228B; HR, 0.13; P = .001) and HEAT repeat containing 6 (HEATR6; HR, 4.94; P = .047). Several candidates were also associated with overall survival (SERPINA4 and ITGA3) as well as PFS independent of disease stage, grade and myometrial invasion (SERPINA4, BET1L and FAM228B).

CONCLUSIONS

This study has identified and validated molecular alterations in tumors from black and white EEC patients, including candidates significantly associated with altered disease outcomes within these patient cohorts. Cancer 2017;123:4004-12. © 2017 American Cancer Society.

The Use of Proteomics in Assisted Reproduction

Despite the explosive increase in the use of Assisted Reproductive Technologies (ART) over the last 30 years, their success rates remain suboptimal. Proteomics is a rapidly-evolving technology-driven science that has already been widely applied in the exploration of human reproduction and fertility, providing useful insights into its physiology and leading to the identification of numerous proteins that may be potential biomarkers and/or treatment targets of a successful ART pregnancy. Here we present a brief overview of the techniques used in proteomic analyses and attempt a comprehensive presentation of recent data from mass spectrometry-based proteomic studies in humans, regarding all components of ARTs, including the male and female gamete, the derived zygote and embryo, the endometrium and, finally, the ART offspring both pre- and postnatally.

Pulse of inflammatory proteins in the pregnant uterus of European polecats (Mustela putorius) leading to the time of implantation

Uterine secretory proteins protect the uterus and conceptuses against infection, facilitate implantation, control cellular damage resulting from implantation, and supply pre-implantation embryos with nutrients. Unlike in humans, the early conceptus of the European polecat (Mustela putorius; ferret) grows and develops free in the uterus until implanting at about 12 days after mating. We found that the proteins appearing in polecat uteri changed dramatically with time leading to implantation. Several of these proteins have also been found in pregnant uteri of other eutherian mammals. However, we found a combination of two increasingly abundant proteins that have not been recorded before in pre-placentation uteri. First, the broad-spectrum proteinase inhibitor α₂-macroglobulin rose to dominate the protein profile by the time of implantation. Its functions may be to limit damage caused by the release of proteinases during implantation or infection, and to control other processes around sites of implantation. Second, lipocalin-1 (also known as tear lipocalin) also increased substantially in concentration. This protein has not previously been recorded as a uterine secretion in pregnancy in any species. If polecat lipocalin-1 has similar biological properties to that of humans, then it may have a combined function in antimicrobial protection and transporting or scavenging lipids. The changes in the uterine secretory protein repertoire of European polecats is therefore unusual, and may be representative of pre-placentation supportive uterine secretions in mustelids (otters, weasels, badgers, mink, wolverines) in general.

E-NPP3 controls plasmacytoid dendritic cell numbers in the small intestine

Extracellular adenosine 5'-triphosphate (ATP) performs multiple functions including activation and induction of apoptosis of many cell types. The ATP-hydrolyzing ectoenzyme ecto-nucleotide pyrophosphatase/phosphodiesterase 3 (E-NPP3) regulates ATP-dependent chronic allergic responses by mast cells and basophils. However, E-NPP3 is also highly expressed on epithelial cells of the small intestine. In this study, we showed that E-NPP3 controls plasmacytoid dendritic cell (pDC) numbers in the intestine through regulation of intestinal extracellular ATP. In Enpp3-/- mice, ATP concentrations were increased in the intestinal lumen. pDC numbers were remarkably decreased in the small intestinal lamina propria and Peyer's patches. Intestinal pDCs of Enpp3-/- mice showed enhanced cell death as characterized by increases in annexin V binding and expression of cleaved caspase-3. pDCs were highly sensitive to ATP-induced cell death compared with conventional DCs. ATP-induced cell death was abrogated in P2rx7-/- pDCs. Accordingly, the number of intestinal pDCs was restored in Enpp3-/- P2rx7-/- mice. These findings demonstrate that E-NPP3 regulates ATP concentration and thereby prevents the decrease of pDCs in the small intestine.

Compartmentalized gene expression profiling of receptive endometrium reveals progesterone regulated ENPP3 is differentially expressed and secreted in glycosylated form

The complexity of endometrial receptivity at the molecular level needs to be explored in detail to improve the management of infertility. Here, differential expression of transcriptomes in receptive endometrial glands and stroma revealed Ectonucleotide Pyrophosphatase/Phosphodiesterase 3 (ENPP3) as a progesterone regulated factor and confirmed by various methods, both at mRNA and protein level. The involvement of ENPP3 in embryo attachment was tested in an in vitro model for human embryo implantation. Interestingly, there was high expression of ENPP3 mRNA in stroma but not protein. Presence of N-glycosylated ENPP3 in receptive phase uterine fluid in women confirms its regulation by progesterone and makes it possible to use in a non-invasive test of endometrial receptivity.

Modulating the endometrial epithelial proteome and secretome in preparation for pregnancy: The role of ovarian steroid and pregnancy hormones

Dialogue between an appropriately developed embryo and hormonally-primed endometrium is essential to achieve implantation and establish pregnancy. Importantly, the point-of-first-contact between the embryo and the maternal endometrium occurs at the endometrial luminal epithelium (LE). Implantation events occur within the uterine cavity microenvironment regulated by local factors. Defects in embryo-endometrial communication likely underlie unexplained infertility; enhanced knowledge of this communication, specifically at initial maternal-fetal contact may reveal targets to improve fertility. Using a human endometrial luminal-epithelial (LE) cell line (ECC1), this targeted proteomic study reveals unique protein changes in both cellular (98% unique identifications) and secreted (96% unique identifications) proteins in the transition to the progesterone-dominated secretory (receptive) phase and subsequently to pregnancy, mediated by embryo-derived human chorionic gonadotropin (hCG). This analysis identified 157 progesterone-regulated cellular proteins, with further 193 significantly altered in response to hCG. Cellular changes were associated with metabolism, basement membrane and cell connectivity, proliferation and differentiation. Secretome analysis identified 1059 proteins; 123 significantly altered by progesterone, and 43 proteins altered by hCG, including proteins associated with cellular adhesion, extracellular-matrix organization, developmental growth, growth factor regulation, and cell signaling. Collectively, our findings reveal dynamic intracellular and secreted protein changes in the endometrium that may modulate successful establishment of pregnancy.

BIOLOGICAL SIGNIFICANCE

This study provides unique insights into the developmental biology of embryo implantation using targeted proteomics by identifying endometrial epithelial cellular and secreted protein changes in response to ovarian steroid hormones and pregnancy hormones that are essential for receptivity and implantation.