Disturbances in the LIF pathway in the endometrium among women with unexplained infertility

An unbiased approach of molecular characterization of the endometrium: toward defining endometrial-based infertility

Infertility is a complex condition affecting millions of couples worldwide. The current definition of infertility, based on clinical criteria, fails to account for the molecular and cellular changes that may occur during the development of infertility. Recent advancements in sequencing technology and single-cell analysis offer new opportunities to gain a deeper understanding of these changes. The endometrium has a potential role in infertility and has been extensively studied to identify gene expression profiles associated with (impaired) endometrial receptivity. However, limited overlap among studies hampers the identification of relevant downstream pathways that could play a role in the development of endometrial-related infertility. To address these challenges, we propose sequencing the endometrial transcriptome of healthy and infertile women at the single-cell level to consistently identify molecular signatures. Establishing consensus on physiological patterns in endometrial samples can aid in identifying deviations in infertile patients. A similar strategy has been used with great success in cancer research. However, large collaborative initiatives, international uniform protocols of sample collection and processing are crucial to ensure reliability and reproducibility. Overall, the proposed approach holds promise for an objective and accurate classification of endometrial-based infertility and has the potential to improve diagnosis and treatment outcomes.

The dysregulation of leukemia inhibitory factor and its implications for endometriosis pathophysiology

Endometriosis is an estrogen dominant, chronic inflammatory disease characterized by the growth of endometrial-like tissue outside of the uterus. The most common symptoms experienced by patients include manifestations of chronic pelvic pain- such as pain with urination, menstruation, or defecation, and infertility. Alterations to Leukemia Inhibitory Factor (LIF), a cytokine produced by the luminal and glandular epithelium of the endometrium that is imperative for successful pregnancy, have been postulated to contribute to infertility. Conditions such as recurrent implantation failure, unexplained infertility, and infertility associated diseases such as adenomyosis and endometriosis, have demonstrated reduced LIF production in the endometrium of infertile patients compared to fertile counterparts. While this highlights the potential involvement of LIF in infertility, LIF is a multifaceted cytokine which plays additional roles in the maintenance of cell stemness and immunomodulation. Thus, we sought to explore the implications of LIF production within ectopic lesions on endometriosis pathophysiology. Through immunohistochemistry of an endometrioma tissue microarray and ELISA of tissue protein extract and peritoneal fluid samples, we identify LIF protein expression in the ectopic lesion microenvironment. Targeted RT qPCR for LIF and associated signaling transcripts, identify LIF to be significantly downregulated in the ectopic tissue compared to eutopic and control while its receptor, LIFR, is upregulated, highlighting a discordance in ectopic protein and mRNA LIF expression. In vitro treatment of endometriosis representative cell lines (12Z and hESC) with LIF increased production of immune-recruiting cytokines (MCP-1, MCP-3) and the angiogenic factor, VEGF, as well as stimulated tube formation in human umbilical vein endothelial cells (HUVECs). Finally, LIF treatment in a syngeneic mouse model of endometriosis induced both local and peripheral alterations to immune cell phenotypes, ultimately reducing immunoregulatory CD206+ small peritoneal macrophages and T regulatory cells. These findings suggest that LIF is present in the ectopic lesions of endometriosis patients and could be contributing to lesion vascularization and immunomodulation.

Interplay of "leukemia inhibitory factor receptor gene" (rs3099124) polymorphism, leukemia inhibitory factor and ovarian steroids with unexplained infertility

OBJECTIVE OF THE STUDY

To explore the association of leukemia inhibitory factor receptor (LIFR) gene variant rs3099124, ovarian steroids, and leukemia inhibitory factor with unexplained infertility in Pakistani females.

METHODOLOGY

A case-control investigation in which eighty-one (81) females with unexplained infertility and one hundred and sixty-two (162) fertile counterparts (age and body mass index compared) were recruited between October 2016 and 2018. Ten milliliters of venous blood was collected from all participants. "Genomic DNA" was taken out from lymphocytes in peripheral blood samples. "Tetra Amplification Refractory Mutation System Polymerase Chain Reaction (T-ARMS-PCR)" was constructed through software "Primer-I". Amplification was carried out by "T-ARMS-PCR" followed by subsequent sequencing for confirmation and extensive consonance. Estradiol, Progesterone and Leukemia Inhibitory Factor (LIF) were measured in serum by ELISA.

RESULTS

Statistically significant difference was noticed in genotype frequency in "LIFR-gene variant; rs3099124" (χ² = 28.222, P value < 0.01) between research participants. Although, rs "3099124" "AA" (OR = 0.000; 95%CI = 0-0) and "GA" genotypes (OR = 0.525; 95%CI = 0.226-1.22) showed non-significant safety/protection against unexplained infertility yet minor/risk allele "A" frequency was greater in women with unexplained infertility suggesting a possible explanation of implantation failure. LIF concentration varied between fertile and infertile groups (χ² = 9.857, P < 0.05) revealing significant threat of unexplained infertility in women with decreased LIF concentration (OR = 2.316, 95%CI = 1.214-4.416). Progesterone was significantly related to unexplained infertility in both study groups (χ² = 20.347, P < 0.05). High progesterone reduced the possibility of unexplained infertility (OR = 0.306; 95% CI = 0.166-0.567).

CONCLUSION

LIFR gene variation (rs3099124) and reduced LIF secretion may cause implantation failure in women with unexplained infertility.

Endogenous progesterone in unexplained infertility: a systematic review and meta-analysis

PURPOSE

To investigate the possibility that altered actions of endogenous progesterone affect receptivity and contribute to unexplained infertility (UI).

METHODS

Two authors electronically searched MEDLINE, CINAHL and Embase databases from inception to 6 July 2022 and hand-searched according to Cochrane methodology. We included all published primary research reporting outcomes related to endogenous progesterone in natural cycles in women with UI. Studies were assessed for risk of bias using a modified Newcastle-Ottawa Score or NHLBI Score. We pooled results where appropriate using a random-effects model. Findings were reported as odds ratios or mean differences.

RESULTS

We included 41 studies (n = 4023). No difference was found between the mid-luteal serum progesterone levels of women with UI compared to fertile controls (MD 0.74, - 0.31-1.79, I² 36%). Women with UI had significantly higher rates of 'out-of-phase' endometrium than controls. Nine out of 10 progesterone-mediated markers of endometrial receptivity were significantly reduced in women with UI compared to fertile controls (the remaining 1 had conflicting results). Resistance in pelvic vessels was increased and perfusion of the endometrium and sub-endometrium reduced in UI compared to fertile controls in all included studies. Progesterone receptor expression and progesterone uptake were also reduced in women with unexplained infertility.

CONCLUSIONS

End-organ measures of endogenous progesterone activity are reduced in women with UI compared to fertile controls. This apparently receptor-mediated reduction in response affects endometrial receptivity and is implicated as the cause of the infertility. Further research is required to confirm whether intervention could overcome this issue, offering a new option for treating unexplained infertility.

TRIAL REGISTRATION

PROSPERO registration: CRD42020141041 06/08/2020.

Role of endometrial microRNAs in repeated implantation failure (mini-review)

MicroRNAs (miRNAs) play various roles in the implantation and pregnancy process. Abnormal regulation of miRNAs leads to reproductive disorders such as repeated implantation failure (RIF). During the window of implantation, different miRNAs are released from the endometrium, which can potentially reflect the status of the endometrium for in vitro fertilization (IVF). The focus of this review is to determine whether endometrial miRNAs may be utilized as noninvasive biomarkers to predict the ability of endometrium to implant and provide live birth during IVF cycles. The levels of certain miRNAs in the endometrium have been linked to implantation potential and pregnancy outcomes in previous studies. Endometrial miRNAs could be employed as non-invasive biomarkers in the assisted reproductive technology (ART) cycle to determine the optimal time for implantation. Few human studies have evaluated the association between ART outcomes and endometrial miRNAs in RIF patients. This review may pave the way for more miRNA transcriptomic studies on human endometrium and introduce a specific miRNA profile as a multivariable prediction model for choosing the optimal time in the IVF cycle.

Endometrial injury concurrent with hysteroscopy increases the expression of Leukaemia inhibitory factor: a preliminary study

OBJECTIVE

It is not known by which mechanism endometrial injury increases pregnancy rates. Leukaemia inhibitory factor (LIF) is a cytokine involved in wound healing and implantation. The aim of this study was to determine the change in endometrial LIF mRNA expression before and after mechanical injury during hysteroscopy.

METHODS

Forty patients with a history of two or more unsuccessful implantations who decided to undergo hysteroscopy in the proliferative phase were divided into two equal groups: one with endometrial injury (scratching group) and the other with noninjury (control group). Endometrial sampling was conducted before injury on the patients in the scratching group, and then injury was performed with monopolar needle forceps. Only diagnostic hysteroscopy was performed on the patients in the control group. Endometrial tissues were collected using a Pipelle catheter between Days 20 and 23 of the mid-luteal phase of the next cycles in both the scratching and control groups. Endometrial LIF mRNA expression was evaluated with the use of reverse-transcription polymerase chain reactions.

RESULTS

Relative changes in mRNA expression levels of the LIF gene in endometrial samples taken before and after injury were calculated using the 2-ΔΔCt method, and the fold changes obtained were compared between and within the groups. Compared with preinjury values, an 11.1-fold increase was found in postinjury LIF mRNA expression in patients with monopolar forceps injury (p < 0.001). There was a 3.9-fold significant increase in postinjury LIF mRNA levels compared with those in the control group (p < 0.02).

CONCLUSIONS

The fertility-promoting effect of hysteroscopy-guided mechanical endometrial injury may be mediated by LIF mRNA.

OUP accepted manuscript

STUDY QUESTION

Can the accuracy of timing of luteal phase endometrial biopsies based on urinary ovulation testing be improved by measuring the expression of a small number of genes and a continuous, non-categorical modelling approach?

SUMMARY ANSWER

Measuring the expression levels of six genes (IL2RB, IGFBP1, CXCL14, DPP4, GPX3 and SLC15A2) is sufficient to obtain substantially more accurate timing estimates and to assess the reliability of timing estimates for each sample.

WHAT IS KNOWN ALREADY

Commercially available endometrial timing approaches based on gene expression require large gene sets and use a categorical approach that classifies samples as pre-receptive, receptive or post-receptive.

STUDY DESIGN, SIZE, DURATION

Gene expression was measured by RTq-PCR in different sample sets, comprising a total of 664 endometrial biopsies obtained 4–12 days after a self-reported positive home ovulation test. A further 36 endometrial samples were profiled by RTq-PCR as well as RNA-sequencing.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A computational procedure, named ‘EndoTime’, was established that models the temporal profile of each gene and estimates the timing of each sample. Iterating these steps, temporal profiles are gradually refined as sample timings are being updated, and confidence in timing estimates is increased. After convergence, the method reports updated timing estimates for each sample while preserving the overall distribution of time points.

MAIN RESULTS AND THE ROLE OF CHANCE

The Wilcoxon rank-sum test was used to confirm that ordering samples by EndoTime estimates yields sharper temporal expression profiles for held-out genes (not used when determining sample timings) than ordering the same expression values by patient-reported times (GPX3: P < 0.005; CXCL14: P < 2.7e−6; DPP4: P < 3.7e−13). Pearson correlation between EndoTime estimates for the same sample set but based on RTq-PCR or RNA-sequencing data showed a high degree of congruency between the two (P = 8.6e−10, R² = 0.687). Estimated timings did not differ significantly between control subjects and patients with recurrent pregnancy loss or recurrent implantation failure (P > 0.05).

LARGE SCALE DATA

The RTq-PCR data files are available via the GitHub repository for the EndoTime software at https://github.com/AE-Mitchell/EndoTime, as is the code used for pre-processing of RTq-PCR data. The RNA-sequencing data are available on GEO (accession GSE180485).

LIMITATIONS, REASONS FOR CAUTION

Timing estimates are informed by glandular gene expression and will only represent the temporal state of other endometrial cell types if in synchrony with the epithelium. Methods that estimate the day of ovulation are still required as these data are essential inputs in our method. Our approach, in its current iteration, performs batch correction such that larger sample batches impart greater accuracy to timing estimations. In theory, our method requires endometrial samples obtained at different days in the luteal phase. In practice, however, this is not a concern as timings based on urinary ovulation testing are associated with a sufficient level of noise to ensure that a variety of time points will be sampled.

WIDER IMPLICATIONS OF THE FINDINGS

Our method is the first to assay the temporal state of luteal-phase endometrial samples on a continuous domain. It is freely available with fully shared data and open-source software. EndoTime enables accurate temporal profiling of any gene in luteal endometrial samples for a wide range of research applications and, potentially, clinical use.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by a Wellcome Trust Investigator Award (Grant/Award Number: 212233/Z/18/Z) and the Tommy's National Miscarriage Research Centre. None of the authors have any competing interests. J.L. was funded by the Biotechnology and Biological Sciences Research Council (UK) through the Midlands Integrative Biology Training Partnership (MIBTP, BB/M01116X/1).

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

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

Expression and significance of miR-30d-5p and SOCS1 in patients with recurrent implantation failure during implantation window

BACKGROUND

Poor endometrial receptivity is a major factor that leads to recurrent implantation failure. However, the traditional method cannot accurately evaluate endometrial receptivity. Various studies have indicated that microRNAs (miRNAs) are involved in multiple processes of embryo implantation, but the role of miRNAs in endometrial receptivity in patients with recurrent implantation failure (RIF) remains elusive. In the present study, we investigated the presence of pinopodes and the roles of miR-30d-5p, suppressor of cytokine signalling 1 (SOCS1) and the leukaemia inhibitory factor (LIF) pathway in women with a history of RIF during the implantation window.

METHODS

Endometrial tissue samples were collected between January 2018 to June 2019 from two groups of women who underwent in vitro fertilisation and embryo transfer (IVF-ET) or frozen ET. The RIF group included 20 women who underwent ≥ 3 ETs, including a total of ≥ 4 good-quality embryos, without pregnancy, whereas the control group included 10 women who had given birth at least once in the past year. An endometrial biopsy was performed during the implantation window (LH + 7). The development of pinopodes in the endometrial biopsy samples from all groups was evaluated using scanning electron microscopy (SEM). Quantitative reverse transcription-polymerase chain reaction and western blotting were used to investigate the expression levels of miR-30d-5p, SOCS1, and the LIF pathway.

RESULTS

The presence of developed pinopodes decreased in patients with RIF on LH + 7. The expression level of miR-30d-5p decreased in the endometria during the implantation window of patients with RIF, whereas the mRNA and protein levels of SOCS1 were significantly higher in the RIF group than in the control group. Furthermore, a negative correlation was observed between the expression of miR-30d-5p and SOCS1 (r² = 0.8362). In addition, a significant decrease in LIF and p-STAT3 expression was observed during the implantation window in patients with RIF.

CONCLUSIONS

MiR-30d-5p and SOCS1 may be potential biomarkers for endometrial receptivity. Changes in pinopode development and abnormal expression of miR-30d-5p, SOCS1 and LIF pathway in the endometrium could be the reasons for implantation failure.

Association of novel stop-gained leukaemia inhibitory factor receptor gene (rs121912501) variant, leukaemia inhibitory factor and ovarian steroids with unexplained infertility among Pakistani women

AIMS AND OBJECTIVES

Embryo implantation is a complex process that requires sequential steps at the interface of embryo interaction with decidual endometrium. Many women after experiencing multiple attempts of assisted reproductive techniques fail to get implantation because of instability of leukaemia inhibitory factor and leukaemia inhibitory factor receptor-signal transducer and activator of transcription factor 3 (LIF-LIFR STAT3) signalling cascade. Therefore, this study explores the association of ovarian steroids, LIF and LIFR stop-gained variant using the tetra primer amplification refractory mutation system-polymerase chain reaction (TARMS-PCR) with unexplained infertility (UEX-IF) among Pakistani women.

MATERIALS AND METHODS

This is a case-control study, a total of 81 unexplained infertile women and 162 fertile controls (with age and BMI matched) were inducted. Serum estradiol, progesterone and LIF were determined using enzyme-linked immunosorbent assay (ELISA). T-ARMS-PCR was designed using Primer 1 software. Genomic DNA was extracted from peripheral blood and amplified using T-ARMS-PCR followed by sequencing for validation and comprehensive concordance.

RESULTS

This study established differences in LIF levels (χ²  = 9.857, P < .05) between patients and controls as well as explored the decreased LIF significantly raised the risk of UEX-IF (OR = 2.316; 95% CI = 1.214, 4.416). Progesterone (P) was significantly associated with UEX-IF between fertile and infertile counterparts (χ²  = 20.347, P < .05). It was also observed that increased Progesterone reduced the risk of UEX-IF (OR = 0.306; 95% CI = 0.166, 0.567). A rapid and inexpensive method for genotyping novel LIFR gene polymorphism through T- ARMS-PCR was successfully developed. LIFR gene SNP (rs121912501) had significant association (χ²  = 200.681, P < .05) with UEX-IF. LIFR rs121912501 "TT" genotype (OR = 5.417; 95% CI = 1.868, 15.709) and "CT" genotype (OR = 3.104, 95% CI = 1.586,6.076) were at increased risk of infertility.

CONCLUSION

UEX-IF can be caused by LIFR gene variation irrespective of increased P. It may open the doors for the discovery of new management plans for infertile women.

Alterations in Epithelial Cell Polarity During Endometrial Receptivity: A Systematic Review

BACKGROUND

Abnormal endometrial receptivity is one of the major causes of embryo implantation failure and infertility. The plasma membrane transformation (PMT) describes the collective morphological and molecular alterations occurring to the endometrial luminal epithelium across the mid-secretory phase of the menstrual cycle to facilitate implantation. Dysregulation of this process directly affects endometrial receptivity and implantation. Multiple parallels between these alterations to confer endometrial receptivity in women have been drawn to those seen during the epithelial-mesenchymal transition (EMT) in tumorigenesis. Understanding these similarities and differences will improve our knowledge of implantation biology, and may provide novel therapeutic targets to manage implantation failure.

METHODS

A systematic review was performed using the Medline (Ovid), Embase, and Web of Science databases without additional limits. The search terms used were "(plasma membrane* or cell membrane*) and transformation*" and "endometrium or endometrial." Research studies on the PMT or its regulation in women, discussing either the endometrial epithelium, decidualized stroma, or both, were eligible for inclusion.

RESULTS

A total of 198 articles were identified. Data were extracted from 15 studies that matched the inclusion criteria. Collectively, these included studies confirmed the alterations occurring to the endometrial luminal epithelium during the PMT are similar to those seen during the EMT. Such similarities included alterations to the actin cytoskeleton remodeling of adherens junctions, integrin expression and epithelial-stromal communication. These were also some differences between these processes, such as the regulation of tight junctions and mucins, which need to be further researched.

CONCLUSIONS

This review raised the prospect of shared and distinct mechanisms existing in PMT and EMT. Further investigation into similarities between the PMT in the endometrium and the EMT in tumorigenesis may provide new mechanistic insights into PMT and new targets for the management of implantation failure and infertility.

N-glycosylation of uterine endometrium determines its receptivity

Glycosylation alters the molecular and functional features of glycoproteins, which is closely related with many physiological processes and diseases. During "window of implantation", uterine endometrium transforms into a receptive status to accept the embryo, thereby establishing successful embryo implantation. In this article, we aimed at investigating the role of N-glycosylation, a major modification type of glycoproteins, in the process of endometrial receptivity establishment. Results found that human uterine endometrial tissues at mid-secretory phase exhibited Lectin PHA-E+L (recognizes the branched N-glycans) positive N-glycans as measured by the Lectin fluorescent staining analysis. By utilizing in vitro implantation model, we found that de-N-glycosylation of human endometrial Ishikawa and RL95-2 cells by tunicamycin (inhibitor of N-glycosylation) and peptide-N-glycosidase F (PNGase F) impaired their receptive ability to human trophoblastic JAR cells. Meanwhile, N-glycosylation of integrin αvβ3 and leukemia inhibitory factor receptor (LIFR) are found to play key roles in regulating the ECM-dependent FAK/Paxillin and LIF-induced STAT3 signaling pathways, respectively, thus affecting the receptive potentials of endometrial cells. Furthermore, in vivo experiments and primary mouse endometrial cells-embryos coculture model further verified that N-glycosylation of mouse endometrial cells contributed to the successful implantation. Our results provide new evidence to show that N-glycosylation of uterine endometrium is essential for maintaining the receptive functions, which gives a better understanding of the glycobiology of implantation.

A Two-Cohort RNA-seq Study Reveals Changes in Endometrial and Blood miRNome in Fertile and Infertile Women

The endometrium undergoes extensive changes to prepare for embryo implantation and microRNAs (miRNAs) have been described as playing a significant role in the regulation of endometrial receptivity. However, there is no consensus about the miRNAs involved in mid-secretory endometrial functions. We analysed the complete endometrial miRNome from early secretory (pre-receptive) and mid-secretory (receptive) phases from fertile women and from patients with recurrent implantation failure (RIF) to reveal differentially expressed (DE) miRNAs in the mid-secretory endometrium. Furthermore, we investigated whether the overall changes during early to mid-secretory phase transition and with RIF condition could be reflected in blood miRNA profiles. In total, 116 endometrial and 114 matched blood samples collected from two different population cohorts were subjected to small RNA sequencing. Among fertile women, 91 DE miRNAs were identified in the mid-secretory vs. early secretory endometrium, while no differences were found in the corresponding blood samples. The comparison of mid-secretory phase samples between fertile and infertile women revealed 21 DE miRNAs from the endometrium and one from blood samples. Among discovered novel miRNAs, chr2_4401 was validated and showed up-regulation in the mid-secretory endometrium. Besides novel findings, we confirmed the involvement of miR-30 and miR-200 family members in mid-secretory endometrial functions.

Effect of Growth Hormone on Uterine Receptivity in Women With Repeated Implantation Failure in an Oocyte Donation Program: A Randomized Controlled Trial

Background and Objective:

Administration of growth hormone (GH) during ovarian stimulation has been shown to improve success rates of in vitro fertilization. GH beneficial effect on oocyte quality is shown in several studies, but GH effect on uterine receptivity is not clear. To assess it, we studied whether GH administration can improve the chance of pregnancy and birth in women who experienced repeated implantation failure (RIF) using donated oocyte programs.

Design and Study Population:

A total of 105 infertile women were enrolled in the randomized controlled trial: 70 women were with a history of RIF with donated oocytes, and 35 infertile women underwent the first oocyte donation attempt. Women receiving donated oocytes were treated with progressively increasing doses of oral estradiol, followed by intravaginal progesterone after previous pituitary desensitization with gonadotropin-releasing hormone agonist. Thirty-five RIF patients were treated with GH (GH patients), whereas the rest of the 35 RIF patients (non-GH patients) and 35 first-attempt patients (positive control group) were not.

Results:

RIF patients receiving GH showed significantly thicker endometrium and higher pregnancy and live birth rates as compared with RIF patients of non-GH study group, although these rates remained somewhat lower as compared with the non-RIF patients of the positive control group. No abnormality was detected in any of the babies born.

Conclusion:

Our data of improved implantation, pregnancy, and live birth rates among infertile RIF patients treated with GH indicate that GH improves uterine receptivity.

Endometrial BCL6 testing for the prediction of in vitro fertilization outcomes: a cohort study

OBJECTIVE

To evaluate endometrial BCL6 expression as a prognostic biomarker for IVF outcome in women with unexplained infertility (UI) before ET.

DESIGN

Prospective cohort study.

SETTING

University-associated infertility clinic.

PATIENT(S)

Women with UI for >1 year.

INTERVENTION(S)

We studied women with UI who underwent testing for endometrial BCL6, in an LH-timed midluteal phase biopsy and completed an IVF cycle and ET.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rate (PR) and live birth rate per transfer was compared for women positive or negative for BCL6 expression. An abnormal BCL6 result was defined by an histologic score (>1.4).

RESULT(S)

Women with normal and abnormal BCL6 and those who conceived or not had similar characteristics. Women with low levels of BCL6 expression had a significantly higher clinical PR (11/17; 64.7%; 95% confidence interval [CI] 41.3-82.6) compared with women with abnormal (high) BCL6 expression (9/52; 17.3%; 95% CI 9.3-30.8). These results yield a relative risk of 0.267 (95% CI 0.13-0.53; P=.0004) for those with normal BCL6 expression, an absolute benefit of 47.4% (95% CI 22.5-72.0). Live birth rate was also significantly higher in women with low BCL6 expression (10/17; 58.8%; 95% CI 36.0-78.4) compared with women with abnormal BCL6 expression (6/52; 11.5%; 95% CI 5.4-23.0). The relative risk was 0.19 (95% CI 0.08-0.45; P=.0002), yielding an absolute benefit of 47.3% (95% CI 21.8-67.8).

CONCLUSION(S)

Aberrant BCL6 expression (histologic score, >1.4) was strongly associated with poor reproductive outcomes in IVF cycles in women with UI.

LIF endometrial expression is impaired in women with unexplained infertility while LIF-R expression in all infertility sub-groups

The main objective of our study was to study LIF and LIF-R endometrial expression during the implantation window in the various sub-groups of infertile women according to infertility cause. A prospective observational case-control study was performed from March 2013 to February 2016. Infertile women consisted of the patients' group (group 2) while fertile women were the control group (group 1). Infertile women were divided according to infertility cause in women with tubal factor (group 2a), poor ovarian reserve (group 2b), endometriosis (group 2c) and unexplained infertility (group 2d). Endometrial biopsy was performed on 7th-8th postovulatory menstrual day. Leukemia Inhibitory Factor (LIF) and LIF-Receptor (LIF-R) expression in epithelial and stromal cells were assessed with Immunohistochemistry (IHC). There were 20 infertile with poor ovarian reserve, 15 with tubal factor, 10 with endometriosis and 15 with unexplained infertility included in the analysis. LIF expression in patients with unexplained infertility was significantly compared with controls (P=0.006). No significant difference was observed between patients with tubal factor, poor ovarian reserve and endometriosis compared with control group (P=0.78, P=0.44 and P=0.56 respectively). Analysis of LIF-R expression in sub-categories of infertility indicated that expression was significantly decreased in all sub-groups of infertility. Our study indicated impaired LIF expression levels only in women with unexplained infertility, while LIF-R expression was impaired in all sub-groups of infertile women. Further multicenter prospective studies should be performed in order to assess the exact etiopathogenetic role of these cytokines in the molecular background of infertility.

Research on the expression of integrin β3 and leukaemia inhibitory factor in the decidua of women with cesarean scar pregnancy

Background

Cesarean scar pregnancy (CSP) is a late serious complication of cesarean section. There has been an increase in the incidence of CSP worldwide in recent years. It’s a life-threatening condition because of the high risk of uncontrolled hemorrhage and uterine rupture. The mechanism of CSP is still unclear. The endometrial receptivity might be different in the cesarean scar between CSP and normal pregnancies. Endometrial expression of integrin β3 and LIF positively correlates with endometrial receptivity and embryo implantation. The purpose of the study is to explore the mechanism of CSP.

Methods

The EnVision two-step immunohistochemical staining technique was used to detect the expression of integrin β3 and LIF in the decidua of women with CSP (20 cases) and normal pregnancies (20 cases). The distribution and staining intensity of integrin β3 and LIF in the two groups were observed. Observation of the staining were done using microscope within five randomly selected high-power fields (HPF, 10 × 40). All data analyses were conducted with SPSS 17.0 and the statistical significance was set at P <0.05.

Results

The decidua in the different parts of both two groups that stained with the anti-integrin β3 and anti-LIF antibody: most of the integrin β3 and LIF positive cells were located in glandular epithelium. The expression intensity of integrin β3 in the cesarean scar in CSP group was significant higher than the uterine cavity in CSP group and the cesarean scar in normal pregnancy group. It’s similar with the uterine cavity in normal pregnancy group. The expression intensity of LIF in the cesarean scar in CSP group was significant higher than the uterine cavity in CSP group and the cesarean scar in normal pregnancy group. It’s significant lower than the uterine cavity in normal pregnancy group.

Conclusions

The decidual integrin β3 and LIF might play an important role in the mechanism of CSP. The increase expression of integrin β3 and LIF in the cesarean scar decidua might be associated with embryo implantation in cesarean scar. The occurrence of CSP might be related to the changes of endometrial receptivity in local cesarean scar.

What is the contribution of embryo-endometrial asynchrony to implantation failure?

PURPOSE

The synchronized development of a viable embryo and a receptive endometrium is critical for successful implantation to take place. The aim of this paper is to review current thinking about the importance of embryo-endometrial synchrony in in vitro fertilization (IVF).

METHODS

Detailed review of the literature on embryo-endometrial synchrony.

RESULTS

By convention, the time when the blastocyst first attaches and starts to invade into the endometrium has been defined as the 'window of implantation'. The term window of implantation can be misleading when it is used to imply that there is a single critical window in time that determines whether implantation will be successful or not. Embryo maturation and endometrial development are two independent continuous processes. Implantation occurs when the two tissues fuse and pregnancy is established. A key concept in understanding this event is developmental 'synchrony', defined as when the early embryo and the uterus are both developing at the same rate such that they will be ready to commence and successfully continue implantation at the same time. Many different events, including controlled ovarian hyperstimulation as routinely used in IVF, can potentially disrupt embryo-endometrial synchrony. There is some evidence in humans that implantation rates are significantly reduced when embryo-endometrial development asynchrony is greater than 3 days (±1.5 days).

CONCLUSIONS

Embryo-endometrial synchrony is critical for successful implantation. There is an unmet need for improved precision in the evaluation of endometrial development to permit better synchronization of the embryo and the endometrium prior to implantation.

Integrative Analyses of Uterine Transcriptome and MicroRNAome Reveal Compromised LIF-STAT3 Signaling and Progesterone Response in the Endometrium of Patients with Recurrent/Repeated Implantation Failure (RIF)

Intimate two-way interactions between the implantation-competent blastocyst and receptive uterus are prerequisite for successful embryo implantation. In humans, recurrent/repeated implantation failure (RIF) may occur due to altered uterine receptivity with aberrant gene expression in the endometrium as well as genetic defects in embryos. Several studies have been performed to understand dynamic changes of uterine transcriptome during menstrual cycles in humans. However, uterine transcriptome of the patients with RIF has not been clearly investigated yet. Here we show that several signaling pathways as well as many genes and microRNAs are dysregulated in the endometrium of patients with RIF (RIFE). Whereas unsupervised hierarchical clustering showed that overall mRNA and microRNA profiles of RIFE were similar to those of endometria of healthy women, many genes were significantly dysregulated in RIFE (cut off at 1.5 fold change). The majority (~75%) of differentially expressed genes in RIFE including S100 calcium binding protein P (S100P), Chemokine (C-X-C motif) ligand 13 (CXCL13) and SIX homeobox 1 (SIX1) were down-regulated, suggesting that reduced uterine expression of these genes is associated with RIF. Gene Set Enrichment analyses (GSEA) for mRNA microarrays revealed that various signaling pathways including Leukemia inhibitory factor (LIF) signaling and a P4 response were dysregulated in RIFE although expression levels of Estrogen receptor α (ERα) and Progesterone receptor (PR) were not significantly altered in RIFE. Furthermore, expression and phosphorylation of Signal transducer and activator of transcription 3 (STAT3) are reduced and a gene set associated with Janus kinase (JAK)-STAT signaling pathway is systemically down-regulated in these patients. Pairwise analyses of microRNA arrays with prediction of dysregulated microRNAs based on mRNA expression datasets demonstrated that 6 microRNAs are aberrantly regulated in RIFE. Collectively, we here suggest that dysregulation of several major signaling pathways and genes critical for uterine biology and embryo implantation may lead to uterine abnormalities in patients with RIF.

Human Decidual Stromal Cells as a Component of the Implantation Niche and a Modulator of Maternal Immunity

The human decidua is a specialized tissue characterized by embryo-receptive properties. It is formed during the secretory phase of menstrual cycle from uterine mucosa termed endometrium. The decidua is composed of glands, immune cells, blood and lymph vessels, and decidual stromal cells (DSCs). In the process of decidualization, which is controlled by oestrogen and progesterone, DSCs acquire specific functions related to recognition, selection, and acceptance of the allogeneic embryo, as well as to development of maternal immune tolerance. In this review we discuss the relationship between the decidualization of DSCs and pathological obstetrical and gynaecological conditions. Moreover, the critical influence of DSCs on local immune cells populations as well as their relationship to the onset and maintenance of immune tolerance is described.

LIF and LIF‑R expression in the endometrium of fertile and infertile women: A prospective observational case‑control study

The aim of the present study was to determine the expression of leukemia inhibitory factor (LIF) and LIF receptor (LIF‑R) in the endometrium of fertile and infertile women during the implantation window. A prospective study was conducted between March 2013 and March 2015 at Iakentro, Infertility Treatment Center (Thessaloniki, Greece) and the 3rd Department of Obstetrics and Gynecology, Aristotle University of Thessaloniki (Thessaloniki, Greece). The patient group consisted of women diagnosed with infertility, whereas the control group consisted of women who had delivered at least one live newborn (fertile women). An endometrial biopsy was obtained using a Pipelle on day 7 or 8 post‑ovulation, and the expression of LIF and LIF‑R was assessed by immunohistochemistry in epithelial and stromal cells. Primary outcomes included positive cellular percentage, staining intensity and H‑score. P<0.05 was considered to indicate a statistically significant difference. Overall, 45 women were included in the present analysis (15 fertile women and 30 infertile women). Mean age was 32.8±6.0 years for the fertile group, and 37.6±3.7 for the infertile group. LIF and LIF‑R expression was significantly reduced in the epithelial cells of infertile women (P=0.05 and P=0.006, respectively). However, no significant differences were detected with regards to the expression of LIF in stromal cells (P=0.95). In addition, LIF‑R expression was relatively higher in the stromal cells of the fertile group; however, the difference did not reach statistical significance (P=0.10). In conclusion, endometrial expression of LIF and LIF‑R is significantly reduced in the epithelial cells of infertile women. Expression patterns of LIF‑R in stromal cells require further research in order to achieve definitive results.

Endometrial transcriptome analysis indicates superiority of natural over artificial cycles in recurrent implantation failure patients undergoing frozen embryo transfer

Little consensus has been reached on the best protocol for endometrial preparation for frozen embryo transfer (FET). It is not known how, and to what extent, hormone supplementation in artificial cycles influences endometrial preparation for embryo implantation at a molecular level, especially in patients who have experienced recurrent implantation failure. Transcriptome analysis of 15 endometrial biopsy samples at the time of embryo implantation was used to compare two different endometrial preparation protocols, natural versus artificial cycles, for FET in women who have experienced recurrent implantation failure compared with fertile women. IPA and DAVID were used for functional analyses of differentially expressed genes. The TRANSFAC database was used to identify oestrogen and progesterone response elements upstream of differentially expressed genes. Cluster analysis demonstrated that natural cycles are associated with a better endometrial receptivity transcriptome than artificial cycles. Artificial cycles seemed to have a stronger negative effect on expression of genes and pathways crucial for endometrial receptivity, including ESR2, FSHR, LEP, and several interleukins and matrix metalloproteinases. Significant overrepresentation of oestrogen response elements among the genes with deteriorated expression in artificial cycles (P < 0.001) was found; progesterone response elements predominated in genes with amended expression with artificial cycles (P = 0.0052).

Association between leukaemia inhibitory factor gene polymorphism and pregnancy outcomes after assisted reproduction techniques

Certain gene polymorphisms are associated with implantation failure and pregnancy loss. Studies of leukaemia inhibitory factor (LIF) gene polymorphisms are scarce. The LIF single nucleotide polymorphism (SNP) thymine (T)/guanine (G) (rs929271) was studied in women to determine whether an association existed with pregnancy outcomes after intracytoplasmic sperm injection (ICSI); 411 women who underwent ICSI were recruited. DNA was extracted from the peripheral blood, and the LIF gene SNP T/G (rs929271) was genotyped using real-time polymerase chain reaction. Participants were divided into three groups according to their LIF genotype: T/T (n = 168), T/G (n = 202) and G/G (n = 41). All IVF and ICSI procedures were carried out under the same clinical and laboratory conditions. The ICSI cumulative results (from fresh plus frozen cycles) of each genotype group were analysed. The G/G genotype in women was associated with a higher implantation rate (T/T: 15.9%, T/G: 16.2%, G/G: 27.0%; P < 0.05), ongoing pregnancy rate/patient (T/T: 31.5%, T/G: 36.1%, G/G: 53.7%; P < 0.05) and ongoing pregnancy rate/transfer (T/T: 18.5%, T/G: 20.2%, G/G: 36.7%; P < 0.05). LIF SNP T/G (rs929271) seems to be a susceptibility biomarker capable of predicting implantation efficiency and pregnancy outcomes.

Leukemia Inhibitory Factor (LIF) Inhibition during Mid-Gestation Impairs Trophoblast Invasion and Spiral Artery Remodelling during Pregnancy in Mice

The placenta forms the interface between the maternal and fetal circulation and is critical for the establishment of a healthy pregnancy. Trophoblast cell proliferation, migration and invasion into the endometrium are fundamental events in the initiation of placentation. Leukemia inhibitory factor (LIF) has been shown to promote trophoblast invasion in vitro, however its precise role in trophoblast invasion in vivo is unknown. We hypothesized that LIF would be required for normal trophoblast invasion and spiral artery remodeling in mice. Both LIF and its receptor (LIFRα) co-localized with cytokeratin-positive invasive endovascular extravillous trophoblasts (EVT) in mouse implantation sites during mid-gestation. Temporally blocking LIF action during specific periods of placental development via administration of our unique LIFRα antagonist, PEGLA, resulted in abnormal trophoblast invasion and impaired spiral artery remodeling compared to PEG control. PEGLA-treated mouse decidual vessels were characterized by retention of α-smooth muscle actin (αSMA)-positive vascular smooth muscle cells (VSMCs), while PEG control decidual vessels were remodelled by cytokeratin-positive trophoblasts. LIF blockade did not alter F4/80-positive decidual macrophage numbers between treatment groups, but resulted in down-regulation of decidual transcript levels of monocyte chemoattractant protein-1 (MCP-1) and interleukin-10 (IL-10), which are important immune cell activation factors that promote spiral artery remodeling during pregnancy. Our data suggest that LIF plays an important role in trophoblast invasion in vivo and may facilitate trophoblast-decidual-immune cell cross talk to enable adequate spiral artery remodeling.

Blocking Endogenous Leukemia Inhibitory Factor During Placental Development in Mice Leads to Abnormal Placentation and Pregnancy Loss

The placenta forms the interface between the maternal and fetal circulation and is critical for the establishment of a healthy pregnancy. Specialized trophoblast cells derived from the embryonic trophectoderm play a pivotal role in the establishment of the placenta. Leukemia inhibitory factor (LIF) is one of the predominant cytokines present in the placenta during early pregnancy. LIF has been shown to regulate trophoblast adhesion and invasion in vitro, however its precise role in vivo is unknown. We hypothesized that LIF would be required for normal placental development in mice. LIF and LIFRα were immunolocalized to placental trophoblasts and fetal vessels in mouse implantation sites during mid-gestation. Temporally blocking LIF action during specific periods of placental development via intraperitoneal administration of our specific LIFRα antagonist, PEGLA, resulted in abnormal placental trophoblast and vascular morphology and reduced activated STAT3 but not ERK. Numerous genes regulating angiogenesis and oxidative stress were altered in the placenta in response to LIF inhibition. Pregnancy viability was also significantly compromised in PEGLA treated mice. Our data suggest that LIF plays an important role in placentation in vivo and the maintenance of healthy pregnancy.

Morphological Changes and Expression of Cytokine After Local Endometrial Injury in a Mouse Model

OBJECTIVE

To establish a mouse model for endometrial injury and determine the underlying mechanism regarding its favorable effect on embryo implantation.

STUDY DESIGN

Female Kunming mice were randomly allocated into 4 groups: group I, normal control; group II, injury procedure control; and group III and group IV, the mice being scratched with a blunt syringe on the right uterine horn or both, respectively. All the mice were mated with the males during the next estrus phase. The number of implanted embryos on each side of uterus was calculated on day 8 of pregnancy. The endometrial samples were taken on day 4 of pregnancy, and the local morphological changes and cytokine expressions were examined.

RESULTS

Compared to group II, our results showed that in group IV (1) there were significantly higher numbers of implanted embryos, (2) the endometrial glands and vasculatures in stroma were obviously increased and the pinopodes were abundant and well developed, and (3) the local levels of cytokines leukemia inhibitory factor (LIF) and oncostatin M (OSM) messenger RNA and protein expression were significantly increased.

CONCLUSIONS

Local mechanical injury on mouse uteri enhanced endometrial receptivity and improved embryo implantation, which were correlated with the characteristic changes in endometrial morphology and the upregulation of LIF and OSM gene and protein expression.

SOCS genes expression during physiological and perturbed implantation in bovine endometrium

In mammals, suppressor of cytokine signalling (CISH, SOCS1 to SOCS7) factors control signalling pathways involved in the regulation of numerous physiological processes including pregnancy. In order to gain new insights into the biological functions of SOCS in the endometrium, a comprehensive analysis of SOCS gene expression was carried out in bovine caruncular (CAR) and intercaruncular (ICAR) tissues collected i) during the oestrous cycle, ii) at the time of maternal recognition of pregnancy and at implantation in inseminated females, iii) following uterine interferon-tau (IFNT) infusion at day 14 post-oestrus, iv) following a period of controlled intravaginal progesterone release and v) following transfer of embryos by somatic-cell nuclear transfer (SCNT). The regulatory effects of IFNT on in vitro cultured epithelial and stromal cells were also examined. Altogether, our data showed that CISH, SOCS4, SOCS5 and SOCS7 mRNA levels were poorly affected during luteolysis and pregnancy. In contrast, SOCS1, SOCS2, SOCS3 and SOCS6 mRNA levels were strongly up-regulated at implantation (day 20 of pregnancy). Experimental in vitro and in vivo models demonstrated that only CISH, SOCS1, SOCS2 and SOCS3 were IFNT-induced genes. Immunohistochemistry showed an intense SOCS3 and SOCS6 staining in the nucleus of luminal and glandular epithelium and of stromal cells of pregnant endometrium. Finally, SOCS3 expression was significantly increased in SCNT pregnancies in keeping with the altered immune function previously reported in this model of compromised implantation. Collectively, our data suggest that spatio-temporal changes in endometrial SOCS gene expression reflect the acquisition of receptivity, maternal recognition of pregnancy and implantation.

Prospective assessment of midsecretory endometrial leukemia inhibitor factor expression versus ανβ3 testing in women with unexplained infertility

OBJECTIVE

To evaluate endometrial leukemia inhibitor factor (LIF) expression as a marker of endometrial receptivity in women with unexplained infertility (UI).

DESIGN

Prospective case-control study.

SETTING

University-associated infertility clinics.

PATIENT(S)

Women with UI for more than 1 year and healthy control women.

INTERVENTION(S)

Endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Time to pregnancy was compared between patients with UI who were evaluated for endometrial LIF protein as well as ανβ3 integrin expression. Endometrium was evaluated using immunohistochemistry (IHC) and messenger RNA by real time reverse transcriptase-polymerase chain reaction (PCR) (quantitative real-time reverse transcriptase-PCR) in samples from women with UI as well as healthy control women.

RESULT(S)

Leukemia inhibitor factor was expressed in epithelial cells in a cyclic fashion in controls, and overall expression in the secretory phase was similar between controls and women with UI, whereas ανβ3 integrin expression was reduced. However, using quantitative real-time PCR, LIF messenger RNA abundance was 4.4-fold lower in women with low levels of ανβ3 integrin expression compared with samples with normal integrins. By immunohistochemistry, ανβ3 integrin expression was always lacking when the histology was out of phase, whereas LIF expression was only negative in a subset of those samples. Reduced endometrial LIF expression was strongly associated with poor reproductive outcomes.

CONCLUSION(S)

Endometrial LIF expression peaks in the midsecretory phase and is reduced in some women with UI. The use of LIF in combination with ανβ3 integrin as biomarkers appears to be superior to integrin testing alone when evaluating endometrial receptivity, primarily because of its earlier pattern of expression during the secretory phase.

The association of trefoil factor 3 gene polymorphisms and haplotypes with unexplained female infertility: molecular insights into TFF3 regulation in receptive phase endometrium

Abstract This study examined the genetic variation within the gene trefoil factor 3 (TFF3) in relation to unexplained female infertility in a group of women where aberrant endometrial maturation was suspected. The study consisted of 113 women with a diagnosis of unexplained infertility and 289 healthy fertile volunteers. Five single nucleotide polymorphisms rs225439, rs533093, rs225361, rs11701143, and rs77436142 within TFF3 gene were analyzed using real-time PCR. The formed haplotype pattern within the TFF3 gene in relation to infertility was also assessed. TFF3 protein localization and expression in receptive stage endometrium at the time of implantation was measured in a subset of fertile (n = 7) and infertile (n = 12) women. Allele and genotype frequencies did not differ significantly between fertile and infertile women, nor did the formed haplotypes. TFF3 protein was expressed in all cell types in receptive stage endometria in fertile and infertile women. No significant association was observed between protein expression and analyzed genotypes. A significantly higher TFF3 expression in luminal epithelial cells was detected in women with unexplained infertility (p = 0.003).

The role of leukemia inhibitory factor in tubal ectopic pregnancy

INTRODUCTION

Ectopic pregnancy is unique to humans and a leading cause of maternal morbidity and mortality. The etiology remains unknown however factors regulating embryo implantation likely contribute. Leukemia inhibitory factor (LIF) has roles in extravillous trophoblast adhesion and invasion and is present in ectopic implantation sites. We hypothesised that LIF facilitates blastocyst adhesion/invasion in the Fallopian tube, contributing to ectopic pregnancy.

METHODS

We immunolocalised LIF receptor (R) in tubal ectopic pregnancy (N = 5). We used an oviduct cell line (OE-E6/E7) to model Fallopian tube epithelial cells and a trophoblast spheroid co-culture model (HTR-8/SVneo cell line formed spheroids) to model blastocyst attachment to the Fallopian tube. We examined LIF signaling pathways in OE-E6/E7 cells by Western blot. The effect of LIF and LIF inhibition (using a novel LIF inhibitor, PEGLA) on first-trimester placental outgrowth was determined.

RESULTS

LIFR localised to villous and extravillous trophoblast and Fallopian tube epithelium in ectopic pregnancy. LIF activated STAT3 but not the ERK pathway in OE-E6/E7 cells. LIF stimulated HTR-8/SVneo spheroid adhesion to OE-E6/E7 cells which was significantly reduced after PEGLA treatment. LIF promoted placental explants outgrowth, while co-treatment with PEGLA blocked outgrowth.

DISCUSSION

Our data suggests LIF facilitates the development of ectopic pregnancy by stimulating blastocyst adhesion and trophoblast outgrowth from placental explants. Ectopic pregnancy is usually diagnosed after 6 weeks of pregnancy, therefore PEGLA may be useful in targeting trophoblast growth/invasion.

CONCLUSION

LIF may contribute to the development of ectopic pregnancies and that pharmacologically targeting LIF-mediated trophoblast outgrowth may be useful as a treatment for ectopic pregnancy.

The low expression of leukemia inhibitory factor in endometrium: possible relevant to unexplained infertility with multiple implantation failures

Unexplained infertility affects 25% of infertile couples. Cytokines and growth factors have been suggested to play an important role in the initial process of successful implantation in humans and failures in their production may be a cause of unexplained infertility. Leukemia inhibitory factor (LIF) and Interleukin-6 (IL-6) have demonstrated their importance in implantation in both animal and human studies. Lower expression of LIF is found in proliferative phase and maximal expression is found in secretory phase of the menstrual cycle. Lower expression of LIF is also found in secretory phase endometrium in patients with infertility. However, studies investigating whether the levels of LIF in proliferative phase are associated with multiple implantation failures (MIFs) are limited. 30 Endometrial biopsies in proliferative phase from unexplained infertile women with MIF with normal hormone levels were collected. The expression of LIF, IL-6 and its receptor gp130 were measured by immunohistochemistry and western blotting. Moderate expression of LIF in the proliferative phase and high expression of LIF in the secretory phase were found in fertile women. However, lower expression of LIF was found in unexplained infertile women with MIF compared to fertile women. There was no difference in endometrial IL-6 and gp130 expression between unexplained infertile women with MIF and fertile women. LIF expression is independent of the process of embryo and dependent partially on the maternal sex hormone levels. Our data suggest that the initial lower expression of LIF in proliferative phase may be one of the causes for multiple failure of implantation.

Glycoprotein 130 promotes human blastocyst development in vitro

OBJECTIVE

To investigate the efficacy of leukemia inhibitory factor (LIF) and/or glycoprotein 130 (gp130) on in vitro growth of human embryos.

DESIGN

Laboratory study.

SETTING

University hospital-based IVF clinic.

PATIENT(S)

A total of 164 frozen embryos that survived thawing were cultured in media supplemented with LIF and/or gp130 or control media.

INTERVENTION(S)

Morphological development was evaluated by light microscopy. Protein expression profiles of single blastocysts were evaluated using matrix-assisted laser desorption/ionization time of flight-based intact cell mass spectrometry.

MAIN OUTCOME MEASURE(S)

Embryo development and protein content.

RESULT(S)

Addition of gp130 to culture media improved blastocyst formation (73% vs. 43%). Addition of LIF to the culture media did not improve embryo development. Protein fingerprint spectra were obtained that revealed significant intensity changes for multiple molecular species including thymosin beta-10, thymosin beta-4, histone H2A, histone H2B, histone H4, ubiquitin, ubiquitin-T, and acyl-CoA binding protein.

CONCLUSION(S)

Glycoprotein 130, but not LIF, seems to be beneficial for preimplantation embryo development, implicating a physiological role in regulating preimplantation development in humans and thus ought to be included in culture media designed for embryo culture to the blastocyst stage. Furthermore, these findings highlight the great potential of matrix-assisted laser desorption/ionization time of flight mass spectrometry and intact cell mass spectrometry as a versatile tool in reproductive medicine research.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Effect of surgical intervention on the expression of leukemia inhibitory factor and L-selectin ligand in the endometrium of hydrosalpinx patients during the implantation window

The aim of this study was to investigate the effect of surgical intervention on the expression of leukemia inhibitory factor (LIF) and L-selectin ligand in the endometrium of patients with hydrosalpinx during the implantation window. A total of 60 patients with hydrosalpinx and 30 patients with tubal obstruction were recruited, and immunohistochemistry was performed to detect the expression of LIF and L-selectin ligand in the endometrium of hydrosalpinx patients before and after surgery and in the endometrium of patients with tubal obstruction. The expression of LIF and L-selectin ligand in the endometrium of hydrosalpinx patients before surgery was markedly lower than that of patients with tubal obstruction (P<0.05). Following surgery, the expression of LIF and L-selectin ligand in the endometrium of hydrosalpinx patients was comparable to that of patients with tubal obstruction (P>0.05). In addition, there was a pronounced difference in the expression of LIF and L-selectin ligand in the endometrium before and after surgery in patients with hydrosalpinx (P<0.05). Hydrosalpinx reduces the expression of LIF and L-selectin ligand in the endometrium during the implantation window. LIF and L-selectin ligand may be important factors influencing the endometrial receptivity of hydrosalpinx patients, and surgery is capable of improving the expression of LIF and L-selectin ligand in the endometrium during the implantation window.

Research resource: interactome of human embryo implantation: identification of gene expression pathways, regulation, and integrated regulatory networks

A prerequisite for successful embryo implantation is adequate preparation of receptive endometrium and the establishment and maintenance of a viable embryo. The success of implantation further relies upon a two-way dialogue between the embryo and uterus. However, molecular bases of these preimplantation and implantation processes in humans are not well known. We performed genome expression analyses of human embryos (n = 128) and human endometria (n = 8). We integrated these data with protein-protein interactions in order to identify molecular networks within the endometrium and the embryo, and potential embryo-endometrium interactions at the time of implantation. For that, we applied a novel network profiling algorithm HyperModules, which combines topological module identification and functional enrichment analysis. We found a major wave of transcriptional down-regulation in preimplantation embryos. In receptive-stage endometrium, several genes and signaling pathways were identified, including JAK-STAT signaling and inflammatory pathways. The main curated embryo-endometrium interaction network highlighted the importance of cell adhesion molecules in the implantation process. We also identified cytokine-cytokine receptor interactions involved in implantation, where osteopontin (SPP1), leukemia inhibitory factor (LIF) and leptin (LEP) pathways were intertwining. Further, we identified a number of novel players in human embryo-endometrium interactions, such as apolipoprotein D (APOD), endothelin 1 (END1), fibroblast growth factor 7 (FGF7), gastrin (GAST), kringle containing trnasmembrane protein 1 (KREMEN1), neuropilin 1 (NRP1), serpin peptidase inhibitor clade A member 3 (SERPINA3), versican (VCAN), and others. Our findings provide a fundamental resource for better understanding of the genetic network that leads to successful embryo implantation. We demonstrate the first systems biology approach into the complex molecular network of the implantation process in humans.

Leukemia inhibitory factor enhances endometrial stromal cell decidualization in humans and mice

Adequate differentiation or decidualization of endometrial stromal cells (ESC) is critical for successful pregnancy in humans and rodents. Here, we investigated the role of leukemia inhibitory factor (LIF) in human and murine decidualization. Ex vivo human (H) ESC decidualization was induced by estrogen (E, 10(-8) M) plus medroxyprogesterone acetate (MPA, 10(-7) M). Exogenous LIF (≥50 ng/ml) induced STAT3 phosphorylation in non-decidualized and decidualized HESC and enhanced E+MPA-induced decidualization (measured by PRL secretion, P<0.05). LIF mRNA in HESC was down-regulated by decidualization treatment (E+MPA) whereas LIF receptor (R) mRNA was up-regulated, suggesting that the decidualization stimulus 'primed' HESC for LIF action, but that factors not present in our in vitro model were required to induce LIF expression. Ex vivo first trimester decidual biopsies secreted >100 pg/mg G-CSF, IL6, IL8, and MCP1. Decidualized HESC secreted IL6, IL8, IL15 and MCP1. LIF (50 ng/ml) up-regulated IL6 and IL15 (P<0.05) secretion in decidualized HESC compared to 0.5 ng/ml LIF. In murine endometrium, LIF and LIFR immunolocalized to decidualized stromal cells on day 5 of gestation (day 0 = day of plug detection). Western blotting confirmed that LIF and the LIFR were up-regulated in intra-implantation sites compared to inter-implantation sites on Day 5 of gestation. To determine the role of LIF during in vivo murine decidualization, intra-peritoneal injections of a long-acting LIF antagonist (PEGLA; 900 or 1200 µg) were given just post-attachment, during the initiation of decidualization on day 4. PEGLA treatment reduced implantation site decidual area (P<0.05) and desmin staining immuno-intensity (P<0.05) compared to control on day 6 of gestation. This study demonstrated that LIF was an important regulator of decidualization in humans and mice and data provides insight into the processes underlying decidualization, which are important for understanding implantation and placentation.

The nucleolar channel system reliably marks the midluteal endometrium regardless of fertility status: a fresh look at an old organelle

OBJECTIVE

To determine whether nucleolar channel systems (NCSs) in the midluteal endometrium are associated with overall fertility status and/or with unexplained infertility.

DESIGN

Retrospective and prospective clinical studies.

SETTING

Repository of stored specimens from prior multicenter study and private infertility center.

PATIENT(S)

Retrospective study that included 97 women (49 fertile couples, 48 infertile couples) who had been randomized for endometrial biopsy during the midluteal or late luteal phase. The prospective study included 78 women with a variety of infertility diagnoses.

INTERVENTION(S)

Endometrial biopsies were obtained and assessed for the presence of NCSs by indirect immunofluorescence.

MAIN OUTCOME MEASURE(S)

The presence of NCS was graded semiquantitatively and dichotomized as normal versus low or absent.

RESULT(S)

Normal presence of NCS was significantly associated with the midluteal phase compared with the late luteal phase (80% vs. 29%). However, there was no association between presence of NCS and fertility status or between presence of NCS and unexplained infertility.

CONCLUSION(S)

Midluteal phase endometrium consistently forms NCSs regardless of fertility status, including unexplained infertility. This indicates a possible role for the NCS in initiating the window of endometrial receptivity. However, the consistent presence of NCSs across several different types of infertility challenges the likelihood that inadequate secretory transformation is a cause of infertility.

Update on the role of leukemia inhibitory factor in assisted reproduction

PURPOSE OF REVIEW

To review the recent literature on the involvement and importance of leukemia inhibitory factor (LIF) in the human implantation process, and the attempts using LIF-based interventions to improve assisted reproductive technologies (ARTs) outcome in women with recurrent implantation failure.

RECENT FINDINGS

High LIF expression is an indicator of receptive endometrium in fertile women. However, in infertile individuals, the data on endometrial LIF expression and secretion are controversial. Even after ruling out other causes of infertility, such as tubal, endocrine, male factor, and endometriosis, LIF-only detection is not sufficient for assessment of implantation potential in women with unexplained infertility. This is obviously in contrast to evidence of the crucial role of LIF in mouse endometrial physiology. In a large multicenter study, recombinant human LIF failed to improve the outcome of IVF treatment in women with recurrent implantation failure.

SUMMARY

A better comprehension of the mechanisms underlying endometrial receptivity and implantation should guide clinicians through proper management and treatment of infertility and implantation failure, and may eventually enable widespread adherence to single embryo transfer practices.