Proteomic characterization of midproliferative and midsecretory human endometrium

HB-EGF-loaded nanovesicles enhance trophectodermal spheroid attachment and invasion

The ability of trophectodermal cells (outer layer of the embryo) to attach to the endometrial cells and subsequently invade the underlying matrix are critical stages of embryo implantation during successful pregnancy establishment. Extracellular vesicles (EVs) have been implicated in embryo-maternal crosstalk, capable of reprogramming endometrial cells towards a pro-implantation signature and phenotype. However, challenges associated with EV yield and direct loading of biomolecules limit their therapeutic potential. We have previously established generation of cell-derived nanovesicles (NVs) from human trophectodermal cells (hTSCs) and their capacity to reprogram endometrial cells to enhance adhesion and blastocyst outgrowth. Here, we employed a rapid NV loading strategy to encapsulate potent implantation molecules such as HB-EGF (NVHBEGF). We show these loaded NVs elicit EGFR-mediated effects in recipient endometrial cells, activating kinase phosphorylation sites that modulate their activity (AKT S124/129, MAPK1 T185/Y187), and downstream signalling pathways and processes (AKT signal transduction, GTPase activity). Importantly, they enhanced target cell attachment and invasion. The phosphoproteomics and proteomics approach highlight NVHBEGF-mediated short-term signalling patterns and long-term reprogramming capabilities on endometrial cells which functionally enhance trophectodermal-endometrial interactions. This proof-of-concept study demonstrates feasibility in enhancing the functional potency of NVs in the context of embryo implantation.

The role of the annexin A protein family at the maternal-fetal interface

Successful pregnancy requires the tolerance of the maternal immune system for the semi-allogeneic embryo, as well as a synchrony between the receptive endometrium and the competent embryo. The annexin family belongs to calcium-regulated phospholipid-binding protein, which functions as a membrane skeleton to stabilize the lipid bilayer and participate in various biological processes in humans. There is an abundance of the annexin family at the maternal-fetal interface, and it exerts a crucial role in embryo implantation and the subsequent development of the placenta. Altered expression of the annexin family and dysfunction of annexin proteins or polymorphisms of the ANXA gene are involved in a range of pregnancy complications. In this review, we summarize the current knowledge of the annexin A protein family at the maternal-fetal interface and its association with female reproductive disorders, suggesting the use of ANXA as the potential therapeutic target in the clinical diagnosis and treatment of pregnancy complications.

Progesterone-induced progesterone receptor membrane component 1 rise-to-decline changes are essential for decidualization

BACKGROUND

Decidualization of endometrial cells is the prerequisite for embryo implantation and subsequent placenta formation and is induced by rising progesterone levels following ovulation. One of the hormone receptors contributing to endometrial homeostasis is Progesterone Receptor Membrane Component 1 (PGRMC1), a non-classical membrane-bound progesterone receptor with yet unclear function. In this study, we aimed to investigate how PGRMC1 contributes to human decidualization.

METHODS

We first analyzed PGRMC1 expression profile during a regular menstrual cycle in RNA-sequencing datasets. To further explore the function of PGRMC1 in human decidualization, we implemented an inducible decidualization system, which is achieved by culturing two human endometrial stromal cell lines in decidualization-inducing medium containing medroxyprogesterone acetate and 8-Br-cAMP. In our system, we measured PGRMC1 expression during hormone induction as well as decidualization status upon PGRMC1 knockdown at different time points. We further conferred proximity ligation assay to identify PGRMC1 interaction partners.

RESULTS

In a regular menstrual cycle, PGRMC1 mRNA expression is gradually decreased from the proliferative phase to the secretory phase. In in vitro experiments, we observed that PGRMC1 expression follows a rise-to-decline pattern, in which its expression level initially increased during the first 6 days after induction (PGRMC1 increasing phase) and decreased in the following days (PGRMC1 decreasing phase). Knockdown of PGRMC1 expression before the induction led to a failed decidualization, while its knockdown after induction did not inhibit decidualization, suggesting that the progestin-induced 'PGRMC1 increasing phase' is essential for normal decidualization. Furthermore, we found that the interactions of prohibitin 1 and prohibitin 2 with PGRMC1 were induced upon progestin treatment. Knocking down each of the prohibitins slowed down the decidualization process compared to the control, suggesting that PGRMC1 cooperates with prohibitins to regulate decidualization.

CONCLUSIONS

According to our findings, PGRMC1 expression followed a progestin-induced rise-to-decline expression pattern during human endometrial decidualization process; and the correct execution of this expression program was crucial for successful decidualization. Thereby, the results of our in vitro model explained how PGRMC1 dysregulation during decidualization may present a new perspective on infertility-related diseases.

Effects of estradiol, progesterone or cAMP on expression of PGRMC1 and progesterone receptor in a xenograft model of human endometrium and in endometrial cell culture

Estradiol and progesterone are key regulators of the menstrual cycle. In the human endometrium, progesterone induces morphological changes required for blastocyst implantation. Dysregulated response to progesterone can lead to endometrial pathologies including uterine bleeding and endometriosis. Besides the canonical nuclear progesterone receptor (encoded by the PGR gene), alternative response pathways include Progesterone Receptor Membrane Component 1 (PGRMC1), suspected to be involved in pathogenesis of endometrial diseases. We previously reported the spatiotemporal profile of PGRMC1 expression in the human endometrium along the menstrual cycle, highlighting progressive increase and decrease during the proliferative and secretory phases, respectively. Here we directly addressed its regulation by estradiol and progesterone, with systematic comparison with regulation of PGR expression. We found a direct correlation between expression of both genes during the proliferative and secretory phases in the cycling endometrium, but not during the menstrual phase. In a xenograft model mimicking the cycle phases, estradiol significantly increased and progesterone significantly decreased PGR expression but changes were not significant for PGRMC1. Finally, we did not find any significant effect of the ovarian steroids on expression of PGR or PGRMC1 in primary culture of endometrial stromal cells, except for a small increase in PGR expression by estradiol. Altogether, our experiments do not allow a major advance in our understanding of the mechanisms of cyclic variation of PGRMC1 expression, in particular regarding potential regulation by the ovarian steroids.

Omics insights into extracellular vesicles in embryo implantation and their therapeutic utility

Implantation success relies on intricate interplay between the developing embryo and the maternal endometrium. Extracellular vesicles (EVs) represent an important player of this intercellular signalling through delivery of functional cargo (proteins and RNAs) that reprogram the target cells protein and RNA landscape. Functionally, the signalling reciprocity of endometrial and embryo EVs regulates the site of implantation, preimplantation embryo development and hatching, antioxidative activity, embryo attachment, trophoblast invasion, arterial remodelling, and immune tolerance. Omics technologies including mass spectrometry have been instrumental in dissecting EV cargo that regulate these processes as well as molecular changes in embryo and endometrium to facilitate implantation. This has also led to discovery of potential cargo in EVs in human uterine fluid (UF) and embryo spent media (ESM) of diagnostic and therapeutic value in implantation success, fertility, and pregnancy outcome. This review discusses the contribution of EVs in functional hallmarks of embryo implantation, and how the integration of various omics technologies is enabling design of EV-based diagnostic and therapeutic platforms in reproductive medicine.

iTRAQ-based Proteomic Analysis Unveils ACSL4 as a Novel Potential Regulator of Human Endometrial Receptivity

Competent endometrial receptivity is a prerequisite for successful embryo implantation. Identification of novel key molecules involved in endometrial receptivity is essential to better interpret human implantation and improve pregnancy rates in assisted reproduction treatment. Isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics was performed to profile the proteomes of the prereceptive (luteinizing hormone [LH] + 2, n = 4) and receptive (LH + 7, n = 4) endometrial tissues. A total of 173 differentially expressed proteins (DEPs) between LH + 2 and LH + 7 endometrial samples were identified. Integrated analysis of the proteomic data and published transcriptomic data was performed to identify the concordant DEPs with differential expression at both the messenger RNA and protein levels. Protein-protein interaction (PPI) network analysis was performed on concordant DEPs. We first identified 63 novel concordant DEPs and 5 hub proteins (ACSL4, ACSL5, COL1A1, PTGS1, and PLA2G4F) between LH + 2 and LH + 7 endometrial samples. ACSL4 was predominantly expressed in endometrial epithelial cells and its expression was significantly upregulated by progesterone in the LH + 7 endometrium and significantly downregulated in repeated implantation failure patients. Knockdown of ACSL4 in endometrial epithelial cells induced the downregulation of endometrial receptivity markers (HOXA10, COX2, and LIF) and the significant decrease of implantation rate during in vitro implantation analysis. This study provides the first gel-independent quantitative proteomes of the LH + 2 and LH + 7 human endometrium using iTRAQ technology. The identified concordant DEPs and hub proteins open a new avenue for future studies aimed at elucidating the underlying mechanisms governing endometrial receptivity. ACSL4 was identified as a novel regulatory molecule in the establishment of endometrial receptivity and might play important roles during implantation.

Spatiotemporal expression pattern of Progesterone Receptor Component (PGRMC) 1 in endometrium from patients with or without endometriosis or adenomyosis

The endometrium plays a crucial role in reproduction and, in humans, is cyclically remodeled under hormonal control. Estradiol favors tissue proliferation whereas progesterone inhibits tissue growth and induces morphological changes. Endometriosis is often associated with fertility issues and with exacerbated estrogen and reduced progesterone concentration or response in the eutopic endometrium. However, underlying mechanisms remain unclear. Progesterone Receptor Membrane Component (PGRMC) 1 is a protein able to modulate progesterone response and its murine knockout reduced fertility. However, the precise spatiotemporal pattern of PGRMC1 expression in the human endometrium is still poorly characterized. We investigated variations of eutopic endometrial PGRMC1 expression by combining RT-qPCR, immunofluorescence and in situ hybridization. We found that PGRMC1 expression progressively increases during the proliferative phase and decreases during the secretory phase. However, immunolabeling and identification of mRNA-containing cells were regularly heterogeneous in samples, according to tissue depth, with a gradient extending from the surface epithelium towards the basalis. There was no significant difference in PGRMC1 mRNA amounts between patients with or without endometriosis or adenomyosis, for any phase of the menstrual cycle, but cells with strong or moderate PGRMC1 immunolabeling were reduced during the proliferative phase in endometriotic patients. In conclusion, although the cyclical variation of PGRMC1 expression globally follows fluctuation of ovarian steroids, further work is required to precisely characterize hormonal control and identify the additional levels of regulation responsible for local adjustment of PGRMC1 concentration. This is particularly important in the light of recent studies emphasizing the correlation between adequate PGRMC1 amounts and fertility.

Current Biomarkers for Endometrial Receptivity

Implantation and the continuation of pregnancy occur through a complicated and sophisticated dialogue, called “cross-talk,” which starts between the embryo and the endometrium in the early stages of oocyte maturation. This dialogue provides synchronization of the journey of the embryo to be implanted with the receptive endometrium. Understanding the activity and function of the hormones and factors involved in this dialogue will provide an understanding of endometrial receptivity, which plays a key role in implantation, and the determination of biomarkers specific for this period. As a result of the development of omics technology, it has become possible to identify biomarkers specific to endometrial receptivity by performing genomic, proteomic, and lipidomic analyses of these hormones and factors. The determination of these biomarkers, their optimization, and making them usable in the clinic will allow increased success in ART.

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.

Comparative Proteomic Analysis Reveals Metformin Improves the Expression of Biomarkers of Endometrial Receptivity in Infertile Women with Minimal/Mild Endometriosis

The prevalence of endometriosis is approximately 10% in women of reproductive age, and 30-50% of women with endometriosis are infertile. Metformin has been reported to inhibit the growth of ectopic lesions in endometriosis. However, its effect on the eutopic endometrium of endometriosis is unknown. This study aimed to identify whether metformin affects endometrial receptivity in infertile women with minimal/mild endometriosis. We enrolled 10 infertile women who were diagnosed with minimal/mild endometriosis through laparoscopy. Paired endometrial tissues of the secretory phase from participants were collected during surgery and after 2 months of metformin treatment (n = 5) or no medical treatment (n = 5). Protein expression profiles of the paired endometrium were detected by proteomics and compared using the self-control method (2 months later vs. in surgery). Proteomics data revealed six proteins associated with endometrial receptivity among the significantly upregulated proteins after metformin treatment (fold change > 1.5, P < 0.05). Insulin-like growth factor binding protein 7 (IGFBP-7) showed the most robust increase in these six endometrial receptivity-related proteins (fold change: 8.668, P < 0.05), while there was no significant change in the controls (fold change: 1.906, P > 0.05). The upregulation of IGFBP-7 has been validated through target proteomics, immunohistochemistry, and further demonstrated in endometriosis mouse models induced by autotransplantation. This study revealed that metformin upregulated the expression of IGFBP-7 in the endometrium of human and mouse models of endometriosis. Metformin potentially affects endometrial receptivity of minimal/mild endometriosis by improving the expression of the endometrial receptivity marker IGFBP-7.

Progesterone Receptor Membrane Component (PGRMC)1 and PGRMC2 and Their Roles in Ovarian and Endometrial Cancer

Cancers of the female reproductive tract are both lethal and highly prevalent. For example, the five-year survival rate of women diagnosed with ovarian cancer is still less than 50%, and endometrial cancer is the fourth most common cancer in women with > 65,000 new cases in the United States in 2020. Among the many genes already established as key participants in ovarian and endometrial oncogenesis, progesterone receptor membrane component (PGRMC)1 and PGRMC2 have gained recent attention given that there is now solid correlative information supporting a role for at least PGRMC1 in enhancing tumor growth and chemoresistance. The expression of PGRMC1 is significantly increased in both ovarian and endometrial cancers, similar to that reported in other cancer types. Xenograft studies using human ovarian and endometrial cancer cell lines in immunocompromised mice demonstrate that reduced expression of PGRMC1 results in tumors that grow substantially slower. While the molecular underpinnings of PGRMCs' mechanisms of action are not clearly established, it is known that PGRMCs regulate survival pathways that attenuate stress-induced cell death. The objective of this review is to provide an overview of what is known about the roles that PGRMC1 and PGRMC2 play in ovarian and endometrial cancers, particularly as related to the mechanisms through which they regulate mitosis, apoptosis, chemoresistance, and cell migration.

Screening and identification of endometrial proteins as novel potential biomarkers for repeated implantation failure

Inadequate endometrial receptivity may be responsible for the low implantation rate of transferred embryos in in vitro fertilization (IVF) treatments. Patients with repeated implantation failure (RIF) impact the clinical pregnancy rate for IVF. We collected endometrial tissue during the implantation window of hysteroscopy biopsies from September 2016 to December 2019 and clinical data were collected simultaneously. Patients were divided into RIF and pregnant controls group according to pregnancy outcomes. A total of 82 differentially expressed endometrial proteins were identified, including 55 up-regulated proteins (>1.50-fold, P < 0.05) and 27 down-regulated proteins (<0.67-fold, P < 0.05) by iTRAQ labeling coupled with the 2D LC MS/MS technique in the RIF group. String analysis found interactions between these proteins which assembled in two bunches: ribosomal proteins and blood homeostasis proteins. The most significant enriched Gene Ontology terms were negative regulation of hydrolase activity, blood microparticle, and enzyme inhibitor activity. Our results emphasized the corticosteroid-binding globulin and fetuin-A as the specific proteins of endometrial receptivity by Western-blot. Our study provided experimental data to establish the objective indicator of endometrial receptivity, and also provided new insight into the pathogenesis of RIF.

The Application of Single-Cell RNA Sequencing in Mammalian Meiosis Studies

Meiosis is a cellular division process that produces gametes for sexual reproduction. Disruption of complex events throughout meiosis, such as synapsis and homologous recombination, can lead to infertility and aneuploidy. To reveal the molecular mechanisms of these events, transcriptome studies of specific substages must be conducted. However, conventional methods, such as bulk RNA-seq and RT-qPCR, are not able to detect the transcriptional variations effectively and precisely, especially for identifying cell types and stages with subtle differences. In recent years, mammalian meiotic transcriptomes have been intensively studied at the single-cell level by using single-cell RNA-seq (scRNA-seq) approaches, especially through two widely used platforms, Smart-seq2 and Drop-seq. The scRNA-seq protocols along with their downstream analysis enable researchers to accurately identify cell heterogeneities and investigate meiotic transcriptomes at a higher resolution. In this review, we compared bulk RNA-seq and scRNA-seq to show the advantages of the scRNA-seq in meiosis studies; meanwhile, we also pointed out the challenges and limitations of the scRNA-seq. We listed recent findings from mammalian meiosis (male and female) studies where scRNA-seq applied. Next, we summarized the scRNA-seq analysis methods and the meiotic marker genes from spermatocytes and oocytes. Specifically, we emphasized the different features of the two scRNA-seq protocols (Smart-seq2 and Drop-seq) in the context of meiosis studies and discussed their strengths and weaknesses in terms of different research purposes. Finally, we discussed the future applications of scRNA-seq in the meiosis field.

Identifying biomarkers for predicting successful embryo implantation: applying single to multi-OMICs to improve reproductive outcomes

BACKGROUND

Successful embryo implantation is a complex process that requires the coordination of a series of events, involving both the embryo and the maternal endometrium. Key to this process is the intricate cascade of molecular mechanisms regulated by endocrine, paracrine and autocrine modulators of embryonic and maternal origin. Despite significant progress in ART, implantation failure still affects numerous infertile couples worldwide and fewer than 10% of embryos successfully implant. Improved selection of both the viable embryos and the optimal endometrial phenotype for transfer remains crucial to enhancing implantation chances. However, both classical morphological embryo selection and new strategies incorporated into clinical practice, such as embryonic genetic analysis, morphokinetics or ultrasound endometrial dating, remain insufficient to predict successful implantation. Additionally, no techniques are widely applied to analyse molecular signals involved in the embryo-uterine interaction. More reliable biological markers to predict embryo and uterine reproductive competence are needed to improve pregnancy outcomes. Recent years have seen a trend towards 'omics' methods, which enable the assessment of complete endometrial and embryonic molecular profiles during implantation. Omics have advanced our knowledge of the implantation process, identifying potential but rarely implemented biomarkers of successful implantation.

OBJECTIVE AND RATIONALE

Differences between the findings of published omics studies, and perhaps because embryonic and endometrial molecular signatures were often not investigated jointly, have prevented firm conclusions being reached. A timely review summarizing omics studies on the molecular determinants of human implantation in both the embryo and the endometrium will help facilitate integrative and reliable omics approaches to enhance ART outcomes.

SEARCH METHODS

In order to provide a comprehensive review of the literature published up to September 2019, Medline databases were searched using keywords pertaining to omics, including 'transcriptome', 'proteome', 'secretome', 'metabolome' and 'expression profiles', combined with terms related to implantation, such as 'endometrial receptivity', 'embryo viability' and 'embryo implantation'. No language restrictions were imposed. References from articles were also used for additional literature.

OUTCOMES

Here we provide a complete summary of the major achievements in human implantation research supplied by omics approaches, highlighting their potential to improve reproductive outcomes while fully elucidating the implantation mechanism. The review highlights the existence of discrepancies among the postulated biomarkers from studies on embryo viability or endometrial receptivity, even using the same omic analysis.

WIDER IMPLICATIONS

Despite the huge amount of biomarker information provided by omics, we still do not have enough evidence to link data from all omics with an implantation outcome. However, in the foreseeable future, application of minimally or non-invasive omics tools, together with a more integrative interpretation of uniformly collected data, will help to overcome the difficulties for clinical implementation of omics tools. Omics assays of the embryo and endometrium are being proposed or already being used as diagnostic tools for personalised single-embryo transfer in the most favourable endometrial environment, avoiding the risk of multiple pregnancies and ensuring better pregnancy rates.

Progesterone receptor membrane component 1 is required for mammary gland development†

The physiological functions of progesterone (P4) in female reproductive organs including the mammary glands are mediated via the progesterone receptor (PR), but not all P4 functions can be explained by PR-mediated signaling. Progesterone receptor membrane component 1 (PGRMC1), a potential mediator of P4 actions, plays an important role in the ovary and uterus in maintaining female fertility and pregnancy, but its function in mammary glands has not been elucidated. This study investigated the role of PGRMC1 in mouse mammary gland development. Unlike in the uterus, exogenous estrogen (E2) and/or P4 did not alter PGRMC1 expression in the mammary gland, and Pgrmc1-knockout (KO) mice displayed reduced ductal elongation and side branching in response to hormone treatment. During pregnancy, PGRMC1 was expressed within both the luminal and basal epithelium and gradually increased with gestation and decreased rapidly after parturition. Moreover, although lactogenic capacity was normal after parturition, Pgrmc1 KO resulted in defective mammary gland development from puberty until midpregnancy, while the expression of PR and its target genes was not significantly different between wild-type and Pgrmc1-KO mammary gland. These data suggest that PGRMC1 is essential for mammary gland development during puberty and pregnancy in a PR-independent manner.

The endometrial proteomic profile around the time of embryo implantation†

Embryo implantation is an intricate process which requires competent embryo and receptive endometrium. The failure of endometrium to achieve receptivity is a recognized cause of infertility. However, due to multiplicity of events involved, the molecular mechanisms governing endometrial receptivity are still not fully understood. Traditional one-by-one approaches, including western blotting and histochemistry, are insufficient to examine the extensive changes of endometrial proteome. Although genomics and transcriptomics studies have identified several significant genes, the underlying mechanism remains to be uncovered owing to post-transcriptional and post-translational modifications. Proteomic technologies are high throughput in protein identification, and they are now intensively used to identify diagnostic and prognostic markers in the field of reproductive medicine. There is a series of studies analyzing endometrial proteomic profile, which has provided a mechanistic insight into implantation failure. These published studies mainly focused on the difference between pre-receptive and receptive stages of endometrium, as well as on the alternation of endometrial proteomics in women with reproductive failure. Here, we review recent data from proteomic analyses regarding endometrium around the time of embryo implantation and propose possible future research directions.

Endometrial receptivity and pregnancy outcome

Human implantation is a highly complex and multifactorial process. Successful implantation requires the presence of a healthy embryo, a receptive endometrium, and a synchronized molecular dialogue between the two, as well as immune tolerance/protection from the host. The endometrial receptivity refers to a hormonally limited period in which the endometrial tissue acquires a transient functional status allowing blastocyst implantation and pregnancy initiation. Global knowledge of endometrial receptivity grew up in recent years. Improvements in genetics, new biomarkers, noninvasive methods, new advanced techniques (Endometrial receptivity assay - the ERA system, proteomic analysis) offer the possibility to evaluate the endometrial status and to manage patients with infertility problems, especially women undergoing assisted reproductive treatment. This overview reports the most relevant knowledge and recent advances in the study of implantation processes from the perspective of the endometrium, often considered as being the main barrier for a successful pregnancy initiation. Endometrial receptivity is a topic of great interest and further studies are needed for the early identification of endometrial abnormalities and the discovery of new strategies for increasing the chance for the establishment of pregnancy.

[Endometrial receptivity in assisted reproductive techniques: An aspect to investigate in embryo implantation failure]

Infertility affects between 8 and 12% of reproductive-age couples worldwide. Despite improvements in assisted reproductive techniques (ART), live birth rates are still limited. In clinical practice, imaging and microscopy are currently widely used, but their diagnostic effectiveness remains limited. In research, the emergence of innovative techniques named OMICS would improve the identification of the implantation window, while progressing in the understanding of the pathophysiological mechanisms involved in embryo implantation failures. To date, transcriptomic analysis seems to be the most promising approach in clinical research. The objective of this review is to present the results obtained with the different approaches available in clinical practice and in research to assess endometrial receptivity in patients undergoing ART.

Progesterone receptor ligands for the treatment of endometriosis: the mechanisms behind therapeutic success and failure

BACKGROUND

Despite intense research, it remains intriguing why hormonal therapies in general and progestins in particular sometimes fail in endometriosis.

OBJECTIVE AND RATIONALE

We review here the action mechanisms of progesterone receptor ligands in endometriosis, identify critical differences between the effects of progestins on normal endometrium and endometriosis and envisage pathways to escape drug resistance and improve the therapeutic response of endometriotic lesions to such treatments.

SEARCH METHODS

We performed a systematic Pubmed search covering articles published since 1958 about the use of progestins, estro-progestins and selective progesterone receptor modulators, to treat endometriosis and its related symptoms. Two reviewers screened the titles and abstracts to select articles for full-text assessment.

OUTCOMES

Progesterone receptor signalling leads to down-regulation of estrogen receptors and restrains local estradiol production through interference with aromatase and 17 beta-hydroxysteroid dehydrogenase type 1. Progestins inhibit cell proliferation, inflammation, neovascularisation and neurogenesis in endometriosis. However, progesterone receptor expression is reduced and disrupted in endometriotic lesions, with predominance of the less active isoform (PRA) over the full-length, active isoform (PRB), due to epigenetic abnormalities affecting the PGR gene transcription. Oxidative stress is another mechanism involved in progesterone resistance in endometriosis. Among the molecular targets of progesterone in the normal endometrium that resist progestin action in endometriotic cells are the nuclear transcription factor FOXO1, matrix metalloproteinases, the transmembrane gap junction protein connexin 43 and paracrine regulators of estradiol metabolism. Compared to other phenotypes, deep endometriosis appears to be more resistant to size regression upon medical treatments. Individual genetic characteristics can affect the bioavailability and pharmacodynamics of hormonal drugs used to treat endometriosis and, hence, explain part of the variability in the therapeutic response.

WIDER IMPLICATIONS

Medical treatment of endometriosis needs urgent innovation, which should start by deeper understanding of the disease core features and diverse phenotypes and idiosyncrasies, while moving from pure hormonal treatments to drug combinations or novel molecules capable of restoring the various homeostatic mechanisms disrupted by endometriotic lesions.

iTRAQ comparison of proteomic profiles of endometrial receptivity

Endometrial receptivity is a limiting step in human reproduction. A disruption in the development of endometrial receptivity is responsible for recurrent implantation failures (RIF) of endometrial origin. To understand the molecular mechanisms behind the endometrial receptivity process, we used the isobaric tag for relative and absolute quantitation (iTRAQ) method to compare three different endometrial statuses: fertile women, intrauterine device (IUD) carriers, and RIF patients. Overall, iTRAQ allowed identified 1889 non-redundant proteins. Of these, 188 were differentially expressed proteins (DEP) (p-value < .05). Pairwise comparisons revealed 133 significant DEP in fertile vs. IUD carriers and 158 DEP in RIF vs. IUD carriers. However, no DEP were identified between fertile and RIF patients. Western blot validation of three DEP involved in endometrial receptivity (plastin 2, lactotransferrin, and lysozyme) confirmed our iTRAQ results. Moreover, functional KEGG enrichment revealed that complement and coagulation cascades and peroxisome were the two most significant pathways for the RIF vs. IUD comparison and ribosome and spliceosome for the fertile vs. IUD comparison, as possible important pathways involved in the endometrial receptivity acquisition. The lack of DEP between fertile and RIF patient endometria suggest that idiopathic RIF may not have an endometrial origin, with other as-yet-unknown factors involved. SIGNIFICANCE: A pilot study where a comparison of the endometrial protein profile from women with different endometrial receptive grade (fertile women, IUD carriers and RIF patients) during the same period of time (overlapping with the window of implantation) of a hormone replacement therapy was performed using a high-throughput proteomic technique. This approach lead us to better understand the molecular mechanisms undergoing endometrial receptivity, a time-limiting step to achieve pregnancy in humans. Moreover, the number of samples per group (10 Fertile women, 10 IUD carriers and 8 RIF patients) according to the methodology here employed (8plex iTRAQ), give more robustness to our results. Our findings confirm that an IUD introduces numerous changes in the endometrial protein profile when compared to fertile and RIF endometria, revealing some key proteins involved in endometrial receptivity. Finding no significant differences between Fertile and RIF patient endometria could suggest that other as-yet-unknown factors could be involved in the etiology of idiopathic RIF.

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.

Lipidomic profile as a noninvasive tool to predict endometrial receptivity

For the present study we asked whether the endometrial fluid lipidomic may be a useful approach to predict endometrial receptivity in freeze-all cycles. For this case-control study, endometrial fluid samples were collected from 41 patients undergoing freeze-all cycles. Samples were split depending on the pregnancy outcome: positive group (n = 24) and negative group (n = 17). Data were acquired by the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were applied. A list of potential biomarker ion ratios was obtained and the values were used to build a receiver operating characteristic (ROC) curve to predict pregnancy success. The lipid categories were attributed by LIPID MAPS database. Ion ratios were established according to their correlations and used for the analysis. The PCA showed a tendency of separation between the studied groups, whereas the PLS-DA was able to clearly distinguish them. Fifteen ratios (13 hyper-represented in the negative and two hyper-represented in the positive group) were selected according to their importance for model prediction. These ratios were used to build the ROC curve, which presented an area under curve of 84.0% (95%CI: 69.2-97.4%; p = 0.009). These findings suggest that lipidomic profiling of endometrial fluid may be a valuable tool for identifying the time interval comprising the window of implantation.

Assessment of potential biomarkers of pre-receptive and receptive endometrium in uterine fluid and a functional evaluation of the potential role of CSF3 in fertility

The endometrium lines a women's uterus becoming receptive, and allowing embryo implantation to occur, for just a few days during the post-ovulatory mid-secretory phase of each menstrual cycle. We investigated whether concentrations of proposed receptivity biomarkers (VEGF, IL8, FGF2, CSF3 sFlt-1, sGP130 and PlGF) secreted by the endometrium into the uterine cavity and forming the microenvironment for embryo implantation is altered among a population of age-matched women with unexplained (idiopathic) infertility compared to fertile women during the receptive mid-secretory phase (n = 16 fertile, 18 infertile) and the prior pre-receptive early secretory phase (n = 19 fertile, 18 infertile) of their cycle. In the mid-secretory cohort significantly elevated concentrations of five biomarkers; PlGF (p = 0.001), IL8 (p = 0.004), sGP130 (p = 0.009), sFlt-1 (p = 0.021), and CSF3 (p = 0.029) was present in uterine fluid of infertile women during the mid-secretory phase, but only CSF3 was significantly elevated in the pre-receptive early secretory phase (p = 0.006). In vitro studies of glycosylated and non-glycosylated forms of CSF3 at representative fertile (20 ng/mL) and infertile (70 ng/mL) effects on endometrium and embryo behaviour were performed. Non-glycosylated CSF3 at fertile concentrations significantly (p < 0.001) elevated endometrial epithelial cell proliferation however chronic treatment or elevated (infertile) concentrations of CSF3 in glycosylated form abrogated the positive effects. Both forms of CSF3 increased trophoblast cell invasion (p < 0.001) regardless of concentration. Mouse embryo outgrowth was significantly (p < 0.01) increased at fertile but not at infertile concentrations. The study confirmed potential utility of five biomarkers of endometrial receptivity for future application in the mid-secretory phase while highlighting CSF3 is elevated in the earlier pre-receptive phase. Our data provides evidence that CSF3 acts on both human endometrium and embryo in a manner that is concentration and glycosylation dependent.

Sorcin is involved during embryo implantation via activating VEGF/PI3K/Akt pathway in mice

Our earlier studies have demonstrated the cyclic variation and also the altered expression of sorcin in endometrium during early-to-mid-secretory phase transition in women with unexplained infertility. The current study was undertaken to establish the functional role of sorcin in endometrial receptivity in mice. Results indicated that sorcin was highly expressed during the window of implantation in mice and functional blockage of sorcin caused significant reduction in number of implanted blastocyst. The receptivity markers (i.e.Integrin β3, HBEGF, IGFBP1, WNT4 and Cyclin E)) were found to be downregulated in sorcin knocked down uterine horn on day 5 as compared to untreated horn. The reduced attachment and expansion of BeWo spheroids on RL95-2 endometrial cells with sorcin knock down, in in vitro model of endometrium-trophoblast interaction further supported these findings. Uterine sorcin expression pattern during estrous cycle and in delayed implantation mice model suggested the upregulation of sorcin by estrogen. The functional blockade of sorcin induced the intracellular Ca⁺² levels in endometrial epithelial cells (EECs), which indicated that altered Ca⁺² homeostasis might be responsible for implantation failure. Sorcin silencing led to significant reduction in the expression of angiogenic factor VEGF and its downstream effector molecules i.e. PI3K, Akt and NOS. The migratory and invasive properties of HUVECs were abrogated by anti-VEGF or by adding culture media from sorcin blocked EECs, which indicated that sorcin might mediate angiogenesis during implantation. Taken together, sorcin is involved in the regulation of Ca⁺²-mediated angiogenesis via VEGF/PI3K/Akt pathway in endometrial cells and plays a crucial role in preparing the endometrium for implantation.

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.

Expression and localization of ARTEMIN in the bovine uterus and embryos

Artemin a member of the glial cell line-derived neurotrophic factor (GDNF) family is present in mice and human preimplantation embryos, and reproductive tract, during early pregnancy promoting embryo development in vitro. The presence of artemin in cattle embryos and reproductive tract, however, is unknown. In the present work we identified for first time artemin in bovine uterine fluid (UF) (Western blot), endometrium (RT-PCR, Western blot and immunohistochemistry) and embryos (RT-PCR and immunohistochemistry) during early preimplantation development. In addition, GFRalpha3, a component of the artemin receptor was localized in blastocysts produced in vitro. Individually developing embryos released ARTEMIN in culture medium and triggered ARTEMIN mRNA down-regulation in epithelial cells from endometrial cell cultures. Our results suggest that ARTEMIN derived from early embryos and maternal reproductive tract may exert important roles during early development in cattle.

Protein expression in human cumulus cells as an indicator of blastocyst formation and pregnancy success

PURPOSE

The goal for the present study was to implement a technique for protein extraction and identification in human cumulus cells (CCs).

METHODS

Forty samples of CCs were collected after ovum pick-up from patients undergoing intracytoplasmic sperm injection (ICSI). Samples were split into the blastocyst group (n = 10), including patients in which all embryos converted into blastocysts, and the non-blastocyst group (n = 10), including patients in which none of the embryos reached the blastocyst stage or the positive-pregnancy (n = 10) and negative-pregnancy group (n = 10). Proteins were extracted and injected into a liquid chromatography system coupled to a mass spectrometer. The spectra were processed and used to search a database.

RESULTS

There were 87 different proteins in samples from the blastocyst and non-blastocyst groups, in which 30 were exclusively expressed in the blastocyst group and 17 in the non-blastocyst group. Among the 72 proteins detected in the pregnancy groups, 19 were exclusively expressed in the positive, and 16 were exclusively expressed in the negative-pregnancy group.

CONCLUSIONS

CC proteomics may be useful for predicting pregnancy success and the identification of patients that should be included in extended embryo culture programs.

Conditional Ablation of Progesterone Receptor Membrane Component 1 Results in Subfertility in the Female and Development of Endometrial Cysts

Progesterone (P4) is essential for female fertility. The objective of this study was to evaluate the functional requirement of the nonclassical P4 receptor (PGR), PGR membrane component 1, in regulating female fertility. To achieve this goal, the Pgrmc1 gene was floxed by insertion of loxP sites on each side of exon 2. Pgrmc1 floxed (Pgrmc1(fl/fl)) mice were crossed with Pgr(cre) or Amhr2(cre) mice to delete Pgrmc1 (Pgrmc1(d/d)) from the female reproductive tract. A 6-month breeding trial revealed that conditional ablation of Pgrmc1 with Pgr(cre/+) mice resulted in a 40% reduction (P = .0002) in the number of pups/litter. Neither the capacity to ovulate in response to gonadotropin treatment nor the expression of PGR and the estrogen receptor was altered in the uteri of Pgrmc1(d/d) mice compared with Pgrmc1(fl/fl) control mice. Although conditional ablation of Pgrmc1 from mesenchymal tissue using Amhr2(cre/+) mice did not reduce the number of pups/litter, the total number of litters born in the 6-month breeding trial was significantly decreased (P = .041). In addition to subfertility, conditional ablation of Pgrmc1 using either Amhr2(cre/+) or Pgr(cre/+) mice resulted in the development of endometrial cysts starting around 4 months of age. Interestingly, pregnancy attenuated the formation of these uterine cysts. These new findings demonstrate that PGR membrane component 1 plays an important role in female fertility and uterine tissue homeostasis.

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.

Progesterone, Inflammatory Cytokine (TNF-α), and Oxidative Stress (H2O2) Regulate Progesterone Receptor Membrane Component 1 Expression in Fetal Membrane Cells

Progesterone receptor membrane component 1 (PGRMC1) is an important novel mediator of progesterone (P4) function in fetal membrane cells. We demonstrated previously that PGRMC1 is differentially expressed in fetal membranes among pregnancy subjects and diminished in preterm premature rupture of membrane subjects. In the current study, we aim to elucidate whether PGRMC1 expression is regulated by P4, tumor necrosis factor α (TNF-α), and H2O2 in fetal membrane cells. Primary cultured membrane cells were serum starved for 24 hours followed by treatments of P4, 17 hydroxyprogesterone caproate, and medroxyprogesterone 17 acetate (MPA) at 10(-7) mol/L with ethanol as vehicle control; TNF-α at 10, 20, and 50 ng/mL with phosphate-buffered saline (PBS) as control; and H2O2 at 10 and 100 μmol/L with culture media as control for 24, 48, and 72 hours. The messenger RNA (mRNA) and protein expression of PGRMC1 was quantified using polymerase chain reaction and Western blotting, respectively. We found that PGRMC1 protein expression was regulated by MPA, TNF-α, and H2O2 in a dose-dependent manner. This regulation is also specific to the type of cell (amnion, chorion, or decidua). The upregulation of PGRMC1 by MPA might be mediated through glucocorticoid receptor (GR) demonstrated using amnion and chorion cells model with GR knockdown by specific small interfering RNA transfection. The mRNA expression of PGRMC1 was decreased by H2O2 (100 μmol/L) treatment in amnion cells, which might ultimately result in downregulation of PGRMC1 protein as our data demonstrated. None of other treatments changed PGRMC1 mRNA level in these cells. We conclude that these stimuli act as regulatory factors of PGRMC1 in a cell-specific manner.

Human S100A10 plays a crucial role in the acquisition of the endometrial receptivity phenotype

In assisted reproduction, about 30% of embryo implantation failures are related to inadequate endometrial receptivity. To identify molecules involved in endometrial receptivity acquisition, we investigated, using a SELDI-TOF approach, the protein expression profile of early-secretory and mid-secretory endometrium samples. Among the proteins upregulated in mid-secretory endometrium, we investigated the function of S100A10 in endometrial receptivity and implantation process. S100A10 was expressed in epithelial and stromal cells of the endometrium of fertile patients during the implantation windows. Conversely, it was downregulated in the mid-secretory endometrium of infertile patients diagnosed as non-receptive. Transcriptome analysis of human endometrial epithelial and stromal cells where S100A10 was silenced by shRNA revealed the deregulation of 37 and 256 genes, respectively, related to components of the extracellular matrix and intercellular connections. Functional annotations of these deregulated genes highlighted alterations of the leukocyte extravasation signaling and angiogenesis pathways that play a crucial role during implantation. S100A10 silencing also affected the migration of primary endometrial epithelial and stromal cells, decidualization and secretory transformation of primary endometrial stromal cells and epithelial cells respectively, and promoted apoptosis in serum-starved endometrial epithelial cells. Our findings identify S100A10 as a player in endometrial receptivity acquisition.

Omics in Reproductive Medicine: Application of Novel Technologies to Improve the IVF Success Rate

Treatment for many infertile couples often consists of in vitro fertilization (IVF) but an estimated 70% of IVF cycles fail to produce a live birth. In an attempt to improve the live birth rate, the vast majority of IVF cycles performed in the United States involve the transfer of multiple embryos, a practice that increases the risk of multiple gestation pregnancy. This is a concern because multiple gestation pregnancies are associated with an increased incidence of maternal and fetal complications and significant cost associated with the care of preterm infants. As the ideal outcome of each IVF cycle is the birth of a single healthy baby, significant effort has focused on identifying embryos with the greatest developmental potential. To date, selection of euploid embryos using comprehensive chromosome screening (CCS) is the most promising approach while metabolomic and proteomic assessment of spent culture medium have the potential to noninvasively assess embryo viability. Endometrial gene expression profiling may help determine the optimal time to perform embryo transfer. While CCS has been implemented in some clinics, further development and optimization will be required before analysis of spent culture medium and endometrial gene expression profiling make the transition to clinical use. This review will describe efforts to identify embryos with the greatest potential to result in a healthy, live birth, with a particular emphasis on detection of embryo aneuploidy and metabolic profiling of spent embryo culture medium. Assessment of endometrial receptivity to identify the optimal time to perform embryo transfer will also be discussed.

Genomic, proteomic and lipidomic evaluation of endometrial receptivity

Endometrial receptivity is a complex phenomenon that plays a vital role in infertility. Although quality of embryo can be evaluated for a successful implantation, endometrial receptivity is still an unknown factor. With advances in technology, the microarray approach has provided an 'omic' tool to evaluate endometrial receptivity. In Latin, 'omic' means the whole family. The genomic, proteomic, and lipidomic evaluations of endometrium mean a wholesome evaluation of the genes, lipids and proteins of the endometrium. Evaluation of receptivity with this three-way approach may provide insight to the potential markers of implantation. Genomic analysis has been limited to date because not every gene alteration affects protein expression. Lipidomic analysis has recently gained popularity because lipids are strictly controlled during the implantation period. In summary, with the recent advances in microarray technology, genomic, lipidomic, and proteomic analyses of the endometrium may provide 'optimal' evaluation tools and criteria to assess receptivity in the near future.

Application of gel-based proteomic technique in female reproductive investigations

Recently, gel-based proteomics has been increasingly applied to investigate proteins involved in female reproductive tract in healthy and disease states. Gel-based proteomics coupled by mass spectrometry (MS) facilitate the identification of new proteins playing roles in cellular and molecular interactions underlying female reproductive biology and it is a useful method to identify novel biomarkers of diseases by studying thousands of proteins simultaneously involved in female reproductive tract in healthy state compared to disease state. This review will discuss the best studies areas contributed to female reproductive biology in which gel-based proteomics coupled by MS has been applied to generate proteome of female reproductive tract in a healthy state.

Label-free proteomics uncovers energy metabolism and focal adhesion regulations responsive for endometrium receptivity

The menstrual cycle of the female uterus leads to periodic changes of the endometrium. These changes are important for developing the endometrial receptivity and for achieving competency of embryo implantation. However, the molecular events underlying the endometrial receptivity process remain poorly understood. Here we applied an LC-MS-based label-free quantitative proteomic approach to compare the endometrial tissues in the midsecretory (receptive) phase with the endometrial tissues in the proliferative phase from age-matched woman (n = 6/group). The proteomes of endometrial tissues were extracted using an SDS-based detergent, digested by the filter-aided sample preparation procedures, and subsequently analyzed by nano-LC-MS/MS (Orbitrap XL) with a 4 h gradient. Reliable protein expression profiles were reproducibly obtained from the endometrial tissues in the receptive and proliferative phases. A total of 2138 protein groups were quantified under highly stringent criteria with a false discovery rate of <1% for peptide and protein groups. Among these proteins, 317 proteins had differences in expression that were statistically significant between the receptive and proliferative phases. Direct protein-protein interaction network analyses of these significantly changed proteins showed that the up-regulation of creatine kinase B-type (CKB) in the receptive phase may be related to endometrium receptivity. The interaction network also showed that proteins related to cell-cell adhesion were down-regulated. Moreover, the results from KEGG pathway analyses are consistent with the protein-protein interaction results. The proteins, including alpha-actinin (ACTN), extracellular matrix proteins, integrin alpha-V, and so on, that are involved in the focal adhesion pathway were down-regulated in the receptive phase compared with the proliferative phase, which may facilitate the implantation of the fertilized ovum. Selected proteins were validated by Western blot analysis and indirect immunofluorescence, including the up-regulation of CKB and down-regulation ACTN in the receptive phase. In summary, our proteomic analysis study shows potential for predicting the endometrial remodeling from the proliferative to the receptivity phase in women, and these results also reveal the key biological mechanisms (such as energy metabolism and focal adhesion) underlying human endometrial receptivity.

Implantation and Establishment of Pregnancy in Human and Nonhuman Primates

Implantation and the establishment of pregnancy are critical for the propagation of the species, but yet remain the limiting steps in human and primate reproduction. Successful implantation requires a competent blastocyst and a receptive endometrium during a specific window of time during the menstrual cycle to initiate the bilateral communication required for the establishment of a successful pregnancy. This chapter provides an overview of these processes and discusses the molecular mechanisms associated with implantation of the blastocyst and decidualization of the uterus in primates.

Cyclic decidualization of the human endometrium in reproductive health and failure

Decidualization denotes the transformation of endometrial stromal fibroblasts into specialized secretory decidual cells that provide a nutritive and immunoprivileged matrix essential for embryo implantation and placental development. In contrast to most mammals, decidualization of the human endometrium does not require embryo implantation. Instead, this process is driven by the postovulatory rise in progesterone levels and increasing local cAMP production. In response to falling progesterone levels, spontaneous decidualization causes menstrual shedding and cyclic regeneration of the endometrium. A growing body of evidence indicates that the shift from embryonic to maternal control of the decidual process represents a pivotal evolutionary adaptation to the challenge posed by invasive and chromosomally diverse human embryos. This concept is predicated on the ability of decidualizing stromal cells to respond to individual embryos in a manner that either promotes implantation and further development or facilitates early rejection. Furthermore, menstruation and cyclic regeneration involves stem cell recruitment and renders the endometrium intrinsically capable of adapting its decidual response to maximize reproductive success. Here we review the endocrine, paracrine, and autocrine cues that tightly govern this differentiation process. In response to activation of various signaling pathways and genome-wide chromatin remodeling, evolutionarily conserved transcriptional factors gain access to the decidua-specific regulatory circuitry. Once initiated, the decidual process is poised to transit through distinct phenotypic phases that underpin endometrial receptivity, embryo selection, and, ultimately, resolution of pregnancy. We discuss how disorders that subvert the programming, initiation, or progression of decidualization compromise reproductive health and predispose for pregnancy failure.

Alteration in endometrial proteins during early- and mid-secretory phases of the cycle in women with unexplained infertility

BACKGROUND

Compromised receptivity of the endometrium is a major cause of unexplained infertility, implantation failure and subclinical pregnancy loss. In order to investigate the changes in endometrial protein profile as a cause of unexplained infertility, the current study was undertaken to analyze the differentially expressed proteins of endometrium from early-secretory (LH+2) to mid-secretory phase (LH+7), in women with unexplained infertility.

METHODS

2-D gel electrophoresis was performed to analyze the proteomic changes between early- (n = 8) and mid-secretory (n = 8) phase endometrium of women with unexplained infertility. The differentially expressed protein spots were identified by LC-MS analysis and validated by immunoblotting and immuno-histochemical analysis in early- (n = 4) and mid-secretory (n = 4) phase endometrium of infertile women. Validated proteins were also analyzed in early- (n = 4) and mid-secretory (n = 4) phase endometrium of fertile women.

RESULTS

Nine proteins were found to be differentially expressed between early- and mid- secretory phases of endometrium of infertile women. The expression of Ras-related protein Rap-1b, Protein disulfide isomerase A3, Apolipoprotein-A1 (Apo-A1), Cofilin-1 and RAN GTP-binding nuclear protein (Ran) were found to be significantly increased, whereas, Tubulin polymerization promoting protein family member 3, Superoxide dismutase [Cu-Zn], Sorcin, and Proteasome subunit alpha type-5 were significantly decreased in mid- secretory phase endometrium of infertile women as compared to early-secretory phase endometrium of infertile women. Validation of 4 proteins viz. Sorcin, Cofilin-1, Apo-A1 and Ran were performed in separate endometrial biopsy samples from infertile women. The up-regulated expression of Sorcin and down-regulated expression of Cofilin-1 and Apolipoprotein-A1, were observed in mid-secretory phase as compared to early-secretory phase in case of fertile women.

CONCLUSIONS

De-regulation of the expression of Sorcin, Cofilin-1, Apo-A1 and Ran, during early- to mid-secretory phase may have physiological significance and it may be one of the causes for altered differentiation and/or maturation of endometrium, in women with unexplained infertility.

Progesterone receptor membrane component 1 deficiency attenuates growth while promoting chemosensitivity of human endometrial xenograft tumors

Endometrial cancer is the leading gynecologic cancer in women in the United States with 52,630 women predicted to be diagnosed with the disease in 2014. The objective of this study was to determine if progesterone (P4) receptor membrane component 1 (PGRMC1) influenced endometrial cancer cell viability in response to chemotherapy in vitro and in vivo. A lentiviral-based shRNA knockdown approach was used to generate stable PGRMC1-intact and PGRMC1-deplete Ishikawa endometrial cancer cell lines that also lacked expression of the classical progesterone receptor (PGR). Progesterone treatment inhibited mitosis of PGRMC1-intact, but not PGRMC1-deplete cells, suggesting that PGRMC1 mediates the anti-mitotic actions of P4. To test the hypothesis that PGRMC1 attenuates chemotherapy-induced apoptosis, PGRMC1-intact and PGRMC1-deplete cells were treated in vitro with vehicle, P4 (1 µM), doxorubicin (Dox, 2 µg/ml), or P4 + Dox for 48 h. Doxorubicin treatment of PGRMC1-intact cells resulted in a significant increase in cell death; however, co-treatment with P4 significantly attenuated Dox-induced cell death. This response to P4 was lost in PGRMC1-deplete cells. To extend these observations in vivo, a xenograft model was employed where PGRMC1-intact and PGRMC1-deplete endometrial tumors were generated following subcutaneous and intraperitoneal inoculation of immunocompromised NOD/SCID and nude mice, respectively. Tumors derived from PGRMC1-deplete cells grew slower than tumors from PGRMC1-intact cells. Mice harboring endometrial tumors were then given three treatments of vehicle (1:1 cremophor EL: ethanol + 0.9% saline) or chemotherapy [Paclitaxel (15 mg/kg, i.p.) followed after an interval of 30 minutes by CARBOplatin (50 mg/kg)] at five day intervals. In response to chemotherapy, tumor volume decreased approximately four-fold more in PGRMC1-deplete tumors when compared with PGRMC1-intact control tumors, suggesting that PGRMC1 promotes tumor cell viability during chemotherapeutic stress. In sum, these in vitro and in vivo findings demonstrate that PGRMC1 plays a prominent role in the growth and chemoresistance of human endometrial tumors.

Two methods for establishing primary human endometrial stromal cells from hysterectomy specimens

Many efforts have been devoted to establish in vitro cell culture systems. These systems are designed to model a vast number of in vivo processes. Cell culture systems arising from human endometrial samples are no exception. Applications range from normal cyclic physiological processes to endometrial pathologies such as gynecological cancers, infectious diseases, and reproductive deficiencies. Here, we provide two methods for establishing primary endometrial stromal cells from surgically resected endometrial hysterectomy specimens. The first method is referred to as "the scraping method" and incorporates mechanical scraping using surgical or razor blades whereas the second method is termed "the trypsin method." This latter method uses the enzymatic activity of trypsin to promote the separation of cells and primary cell outgrowth. We illustrate step-by-step methodology through digital images and microscopy. We also provide examples for validating endometrial stromal cell lines via quantitative real time polymerase chain reactions (qPCR) and immunofluorescence (IF).

Power of proteomics in linking oxidative stress and female infertility

Endometriosis, PCOS, and unexplained infertility are currently the most common diseases rendering large numbers of women infertile worldwide. Oxidative stress, due to its deleterious effects on proteins and nucleic acids, is postulated to be the one of the important mechanistic pathways in differential expression of proteins and in these diseases. The emerging field of proteomics has allowed identification of proteins involved in cell cycle, as antioxidants, extracellular matrix (ECM), cytoskeleton, and their linkage to oxidative stress in female infertility related diseases. The aim of this paper is to assess the association of oxidative stress and protein expression in the reproductive microenvironments such as endometrial fluid, peritoneal fluid, and follicular fluid, as well as reproductive tissues and serum. The review also highlights the literature that proposes the use of the fertility related proteins as potential biomarkers for noninvasive and early diagnosis of the aforementioned diseases rather than utilizing the more invasive methods used currently. The review will highlight the power of proteomic profiles identified in infertility related disease conditions and their linkage with underlying oxidative stress. The power of proteomics will be reviewed with regard to eliciting molecular mechanisms for early detection and management of these infertility related conditions.

Proteomic analysis of the sheep caruncular and intercaruncular endometrium reveals changes in functional proteins crucial for the establishment of pregnancy

The expression and regulation of endometrial proteins are crucial for conceptus implantation and development. However, little is known about site-specific proteome profiles of the mammalian endometrium during the peri-implantation period. We utilised a two-dimensional gel electrophoresis/mass spectrometry-based proteomics approach to compare and identify differentially expressed proteins in sheep endometrium. Caruncular and intercaruncular endometrium were collected on days 12 (C12) and 16 (C16) of the oestrous cycle and at three stages of pregnancy corresponding to conceptus pre-attachment (P12), implantation (P16) and post-implantation (P20). Abundance and localisation changes in differentially expressed proteins were determined by western blot and immunohistochemistry. In caruncular endometrium, 45 protein spots (5% of total spots) altered between day 12 of pregnancy (P12) and P16 while 85 protein spots (10% of total spots) were differentially expressed between P16 and C16. In intercaruncular endometrium, 31 protein spots (2% of total spots) were different between P12 and P16 while 44 protein spots (4% of total spots) showed differential expression between C12 and C16. The pattern of protein changes between caruncle and intercaruncle sites was markedly different. Among the protein spots with implantation-related changes in volume, 11 proteins in the caruncular endometrium and six proteins in the intercaruncular endometrium, with different functions such as protein synthesis and degradation, antioxidant defence, cell structural integrity, adhesion and signal transduction, were identified. Our findings highlight the different but important roles of the caruncular and intercaruncular proteins during early pregnancy.