Diagnosis of Endometrial-Factor Infertility: Current Approaches and New Avenues for Research

Impact of miRNAs in the pathoetiology of recurrent implantation failure

Recurrent implantation failure (RIF) is a condition with a multifactorial basis. Recent research has focused on the role of genetic factors in the pathophysiology of RIF. Of particular note, miRNAs have been found to contribute to the pathogenesis of RIF. Several miRNA polymorphisms have been investigated in this context. Moreover, dysregulation of expression of a number of miRNAs, including miR-374a-5p, miR-145-5p, miR-30b-5p, miR-196b-5p, miR-22, miR-181 and miR-145 has been found in RIF. This review concentrates on the role of miRNAs in RIF to help in identification of the molecular basis for this condition and design of more effective methods for management of RIF, especially in a personalized manner that relies on the expression profiles of miRNAs in the peripheral blood or endometrium.

Intrauterine Infusion of Leukocyte-Poor Platelet-Rich Plasma Is an Effective Therapeutic Protocol for Patients with Recurrent Implantation Failure: A Retrospective Cohort Study

BACKGROUND

The clinical application of autologous leukocyte-poor platelet-rich plasma (LP-PRP) in patients with recurrent implantation failure (RIF) is rare. This retrospective observational cohort study aimed to evaluate the efficacy of LP-PRP intrauterine infusion in patients with RIF.

METHODS

Patients with RIF undergoing frozen embryo transfer (FET) from January 2019 to December 2021 (n = 118) were enrolled, with those undergoing LP-PRP intrauterine infusion as the PRP group (n = 64), and those receiving no LP-PRP treatment as the control group (n = 54). The beta-human chorionic gonadotropin (β-hCG)-positive rate, clinical pregnancy rate (CPR), live birth rate (LBR), and miscarriage rate (MR) per ET cycle were compared.

RESULTS

The β-hCG-positive rate (57.8% vs. 38.9%, p = 0.041), CPR (45.3% vs. 24.5%, p = 0.022), and LBR per ET cycle (42.2% vs. 18.5%, p = 0.009) were higher in the PRP group than in the control group, and the three variables (62.5% vs. 41.2%, p = 0.040, 47.5% vs. 23.5%, p = 0.033, and 47.5% vs. 20.6%, p = 0.027) in the PRP group transferred with the blastocyst-stage embryos were also higher than those in the control group. The MR was similar in all groups.

CONCLUSIONS

The LP-PRP treatment could improve the β-hCG-positive rate, CPR, and LBR in RIF patients undergoing FET cycles.

Endometrial Receptivity During the Preimplantation Period: A Narrative Review

Endometrial receptivity is a complex and critical process fundamental to achieving a successful pregnancy. While researchers have made significant strides in understanding the underlying mechanisms governing endometrial receptivity, effective diagnostic and therapeutic strategies remain scarce. This review article aims to elucidate the various factors that contribute to endometrial receptivity, including the hormonal regulation and molecular mechanisms that govern this process, as well as potential biomarkers for assessing endometrial receptivity. One of the major challenges in identifying reliable biomarkers for endometrial receptivity is the intricate nature of the process itself. Nonetheless, recent advances in transcriptomic and proteomic technologies have identified several candidate biomarkers that could potentially enhance our ability to predict endometrial receptivity. Furthermore, emerging technologies such as single-cell RNA sequencing and mass spectrometry-based proteomics hold great promise for providing novel insights into the molecular mechanisms underlying endometrial receptivity. Despite the lack of reliable biomarkers, various therapeutic strategies have been proposed to improve endometrial receptivity. One promising approach involves the transplantation of mesenchymal stem cells (MSCs), which have been shown to increase endometrial thickness and receptivity in both animal models and clinical trials. Growth factors, cytokines, and exosomes derived from MSCs and other cell types may also have therapeutic potential for addressing endometrial dysfunction.

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.

Live birth after transfer of a single euploid vitrified-warmed blastocyst according to standard timing vs. timing as recommended by endometrial receptivity analysis

OBJECTIVE

To determine whether endometrial receptivity analysis (ERA) improves live births in patients with and without a history of unsuccessful frozen embryo transfers (FETs).

DESIGN

Retrospective cohort study.

SETTING

Large reproductive center.

PATIENT(S)

Patients with and without ERA before euploid single FET were included in the analysis.

INTERVENTION(S)

Subjects in the exposed group underwent ERA and ERA-timed FETs. Subjects in the unexposed group followed a standard protocol FET without ERA. Outcomes were compared between nonreceptive and receptive subjects undergoing an ERA-timed FET and between ERA-timed vs. standard protocol FETs.

MAIN OUTCOME MEASURE(S)

The primary outcome was a live birth; secondary outcomes were biochemical and clinical pregnancy rates.

RESULT(S)

A total of 307 ERA-timed FETs and 2,284 standard protocol FETs were analyzed. One hundred twenty-five patients (40.7%) were ERA receptive, and 182 (59.3%) were ERA nonreceptive. After adjusting for the number of the previously failed FETs, there was no difference in the proportion of receptive and nonreceptive ERA results. There were no statistically significant differences in live births in patients with ERA-receptive vs. ERA-nonreceptive results (48.8% and 41.7%, respectively; adjusted odds ratio 1.17; 95% CI, 0.97-1.40). There were no statistically significant differences in live births in patients with or without ERA testing results before FET (44.6% and 51.3%, respectively; adjusted odds ratio 0.87; 95% CI, 0.73-1.04).

CONCLUSION(S)

Patients with an increasing number of previous failed euploid FET cycles are not at an increased risk of a displaced window of implantation. Patients categorized as receptive vs. nonreceptive and those without ERA testing results have comparable FET success rates.

Sildenafil Supplementation for Women Undergoing Infertility Treatments: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The aim of this systematic review and meta-analysis is to summarize data on the effectiveness of Sildenafil supplementation for women undergoing assisted reproduction techniques. This meta-analysis of randomized controlled trials (RCTs) evaluates the effects of Sildenafil administration during infertility treatments compared with a control group in infertile women. Outcomes evaluated were endometrial thickness (ETh) and the clinical pregnancy rate (CPR). The chemical pregnancy rate (ChPR) was also evaluated. Pooled results were expressed as the risk ratio (RR) or mean differences (MD) with a 95% confidence interval (95% CI). Women undergoing ovulation induction who received Sildenafil showed higher ETh and a higher CPR in comparison to controls. In this group, both the ETh and ChPR resulted in significantly higher values only with delayed start administration. Women undergoing fresh or frozen embryo transfer who received Sildenafil showed no significant advantages regarding ETh and CPR in comparison to controls. In this group, we found a significantly higher ChPR in women receiving Sildenafil. A subgroup analysis revealed significant advantages regarding ETh with oral administration for women undergoing fresh or frozen embryo transfer. Sildenafil therapy appears to improve endometrial thickness and pregnancy rate in women undergoing timed intercourses but it resulted not effective in IUI and IVF treatments. Further RCTs with rigorous methodology are still mandatory.

A 3D endometrial organotypic model simulating the acute inflammatory decidualisation initiation phase with epithelial induction of the key endometrial receptivity marker, integrin αVβ3

STUDY QUESTION

Is it possible to develop a simplified physiological in vitro system representing the key cell-types associated with a receptive endometrial phenotype?

SUMMARY ANSWER

We present a new concept to investigate endometrial receptivity, with a 3D organotypic co-culture model to simulate an early and transient acute autoinflammatory decidual status that resolves in the induction of a receptive endometrial phenotype.

WHAT IS KNOWN ALREADY

Embryo implantation is dependent on a receptive uterine environment. Ovarian steroids drive post-ovulation structural and functional changes in the endometrium, which becomes transiently receptive for an implanting conceptus, termed the ‘window of implantation’, and dysregulation of endometrial receptivity is implicated in a range of reproductive, obstetric, and gynaecological disorders and malignancies. The interactions that take place within the uterine microenvironment during this time are not fully understood, and human studies are constrained by a lack of access to uterine tissue from specific time-points during the menstrual cycle. Physiologically relevant in vitro model systems are therefore fundamental for conducting investigations to better understand the cellular and molecular mechanisms controlling endometrial receptivity.

STUDY DESIGN, SIZE, DURATION

We conducted an in vitro cell culture study using human cell lines and primary human cells isolated from endometrial biopsy tissue. The biopsy tissue samples were obtained from three women attending gynaecological outpatient departments in NHS Lothian. The work was carried out between December 2016 and April 2019, at the MRC Centre for Reproductive Health, Queen’s Medical Research Institute, University of Edinburgh.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An endometrial stromal cell (ESC) line, and endometrial epithelial cells (EECs) isolated from endometrial biopsy tissue and expanded in vitro by conditional reprogramming, were used throughout the study. Immunocytochemical and flow cytometric analyses were used to confirm epithelial phenotype following conditional reprogramming of EECs. To construct an endometrial organotypic co-culture model, ESCs were embedded within a 3D growth factor-reduced Matrigel structure, with a single layer of conditionally reprogrammed EECs seeded on top. Cells were stimulated with increasing doses of medroxyprogesterone acetate, cAMP and oestradiol, in order to induce ESC decidual transformation and endometrial receptivity. Decidual response and the induction of a receptive epithelial phenotype were assessed by immunocytochemical detection and quantitative in-cell western analyses, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

A transient up-regulation of the interleukin-33 receptor protein, ST2L, was observed in ESCs, indicating a transient autoinflammatory decidual response to the hormonal stimulation, known to induce receptivity gene expression in the overlying epithelium. Hormonal stimulation increased the EEC protein levels of the key marker of endometrial receptivity, integrin αVβ3 (n = 8; *P < 0.05; ***P < 0.0001). To our knowledge, this is the first demonstration of a dedicated endometrial organotypic model, which has been developed to investigate endometrial receptivity, via the recapitulation of an early decidual transitory acute autoinflammatory phase and induction of an epithelial phenotypic change, to represent a receptive endometrial status.

LIMITATIONS, REASONS FOR CAUTION

This simplified in vitro ESC-EEC co-culture system may be only partly representative of more complex in vivo conditions.

WIDER IMPLICATIONS OF THE FINDINGS

The 3D endometrial organotypic model presented here may offer a valuable tool for investigating a range of reproductive, obstetric, and gynaecological disorders, to improve outcomes for assisted reproductive technologies, and for the development of advances in contraceptive methods.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by a Medical Research Council Centre Grant (project reference MR/N022556/1). R.F. was the recipient of a Moray Endowment award and a Barbour Watson Trust award. C.-J.L. is a Royal Society of Edinburgh Personal Research Fellow, funded by the Scottish Government. The authors have no conflicts of interest to declare.

A comparative evaluation of subendometrial and intrauterine platelet-rich plasma treatment for women with recurrent implantation failure

OBJECTIVE

To compare the effectiveness of treatment with autologous activated platelet-rich plasma (PRP), administered to either the subendometrium (SE-PRP) or endometrial surface (intrauterine; IU-PRP), against controls.

DESIGN

Prospective observational cohort study.

SETTING

Tertiary fertility unit.

PATIENTS

Women aged <40 years with a history of recurrent implantation failure undergoing frozen embryo transfer (FET) (n = 318).

INTERVENTIONS

In SE-PRP, PRP was injected into the subendometrial space transvaginally in the luteal phase of the previous cycle of embryo transfer under ultrasound guidance (n = 55). In IU-PRP, PRP was administered during the index FET cycle when the endometrium was approximately 7 mm (n = 109). Both SE-PRP and IU-PRP groups were administered 300 μg of granulocyte colony-stimulating factor (G-CSF) subcutaneously once a day for 3 days to boost white blood cells (WBC) and growth factor production in the PRP sample. The control group consisted of women who did not choose PRP treatment and underwent standard FET with no intervention (n = 154).

MAIN OUTCOME MEASURES

Ongoing pregnancy rate or live birth rate (OPR/LBR) per transfer cycle, clinical pregnancy rate (CPR) per transfer cycle, and miscarriage rate.

RESULTS

As a result, OPR/LBR was higher in the SE-PRP (22/55, 40%) and IU-PRP (45/109, 41.3%) groups than that in the control group (34/154, 22.1%). It was similar between the SE-PRP and IU-PRP groups. Moreover, CPR showed a similar trend with a higher rate in the SE-PRP (28/55, 51%) and IU-PRP (57/109, 52.3%) groups than that in the controls (52/154, 33.8%). No statistical difference in the CPR was noted between the SE-PRP and IU-PRP groups. The miscarriage rate was similar in all three groups (14/55, 25.45%; 25/109, 22.23%; and 34/154, 22.07%, respectively).

CONCLUSION

In women with a history of recurrent implantation failure, PRP treatment appears to improve FET outcome with an increase in OPR/LBR. However, SE-PRP treatment does not offer any advantage over lesser invasive IU-PRP treatment.

MAML1: a coregulator that alters endometrial epithelial cell adhesive capacity

BACKGROUND

Abnormalities in endometrial receptivity has been identified as a major barrier to successful embryo implantation. Endometrial receptivity refers to the conformational and biochemical changes occurring in the endometrial epithelial layer which make it adhesive and receptive to blastocyst attachment. This takes place during the mid-secretory phase of woman's menstrual cycle and is a result of a delicate interplay between numerous hormones, cytokines and other factors. Outside of this window, the endometrium is refractory to an implanting blastocyst. It has been shown that Notch ligands and receptors are dysregulated in the endometrium of infertile women. Mastermind Like Transcriptional Coactivator 1 (MAML1) is a known coactivator of the Notch signaling pathway. This study aimed to determine the role of MAML1 in regulating endometrial receptivity.

METHODS

The expression and localization of MAML1 in the fertile human endometrium (non-receptive proliferative phase versus receptive mid-secretory phase) were determined by immunohistochemistry. Ishikawa cells were used as an endometrial epithelial model to investigate the functional consequences of MAML1 knockdown on endometrial adhesive capacity to HTR8/SVneo (trophoblast cell line) spheroids. After MAML1 knockdown in Ishikawa cells, the expression of endometrial receptivity markers and Notch dependent and independent pathway members were assessed by qPCR. Two-tailed unpaired or paired student's t-test were used for statistical analysis with a significance threshold of P < 0.05.

RESULTS

MAML1 was localized in the luminal epithelium, glandular epithelium and stroma of human endometrium and the increased expression identified in the mid-secretory phase was restricted only to the luminal epithelium (P < 0.05). Functional analysis using Ishikawa cells demonstrated that knockdown of MAML1 significantly reduced epithelial adhesive capacity (P < 0.01) to HTR8/SVneo (trophoblast cell line) spheroids compared to control. MAML1 knockdown significantly affected the expression of classical receptivity markers (SPP1, DPP4) and this response was not directly via hormone receptors. The expression level of Hippo pathway target Ankyrin repeat domain-containing protein 1 (ANKRD1) was also affected after MAML1 knockdown in Ishikawa cells.

CONCLUSION

Our data strongly suggest that MAML1 is involved in regulating the endometrial adhesive capacity and may facilitate embryo attachment, either directly or indirectly through the Notch signaling pathway.

Suboptimal mid-luteal progesterone concentrations are associated with aberrant endometrial gene expression, potentially resulting in implantation failure

RESEARCH QUESTION

What is the difference in endometrial transcriptomics between women with normal and with low mid-luteal progesterone during the implantation window?

DESIGN

An endometrial biopsy and serum progesterone concentration were taken from participants during the mid-luteal phase (LH+7 to LH+9). A total of 12 participants were recruited and categorized into two groups based on their progesterone concentrations: normal progesterone (>15 ng/ml, n = 6) and low progesterone (<15 ng/ml, n = 6). Global endometrial gene expression between the two groups was compared by microarray techniques. Principal component analysis was used to display the gene's expression pattern. Pathway and gene ontology enrichment analysis were performed to determine the biological mechanism of progesterone on the endometrium.

RESULTS

Several key genes related to endometrial receptivity were found to be regulated by progesterone. With regard to gene ontology and pathway analysis, progesterone was shown to be mainly involved in structure morphogenesis predominantly during a process of decidualization, extracellular matrix-receptor interaction and cell adhesion. Distinct differences were observed in the transcriptomic profiles between the two groups, indicating potential impairment of endometrial receptivity in women with suboptimal progesterone concentrations. There was a relatively similar pattern of gene expression between endometrial samples with progesterone concentrations approximately 10 ng/ml and >15 ng/ml. Thus, a progesterone concentration of between 10 and 15 ng/ml appears to be sufficient to induce endometrial receptivity.

CONCLUSIONS

Abnormally low progesterone below the threshold of 10-15 ng/ml during the implantation window results in aberrant endometrial gene expression that may affect implantation potential.

Endometrial scratching for infertile women undergoing a first embryo transfer: a systematic review and meta-analysis of published and unpublished data from randomized controlled trials

OBJECTIVE

To investigate endometrial scratch injury (ESI) as an intervention to improve IVF outcome in women undergoing a first ET.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Infertile women undergoing a first fresh/frozen embryo transfer.

INTERVENTION(S)

We included published and unpublished data from randomized controlled trials in which the intervention group received ESI and controls received placebo or no intervention. Pooled results were expressed as relative risk (RR) with 95% confidence interval (CI). The review protocol was registered in PROSPERO to start the data extraction (CRD42018087786).

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy/live birth rate (OPR/LBR), clinical pregnancy rate (CPR), multiple pregnancy rate (MPR), miscarriage rate (MR), and ectopic pregnancy rate (EPR).

RESULT(S)

Seven studies were included (1,354 participants). We found a nonsignificant difference between groups in terms of OPR/LBR, CPR, MR, MPR, and EPR. Subgroup analysis found that ESI on the day of oocyte retrieval (achieved by a Novak curette) reduced OPR/LBR (RR 0.31, 95% CI 0.14-0.69) and CPR (RR 0.36, 95% CI 0.18-0.71), whereas ESI during the cycle preceding ET (performed through soft devices) had no effect on OPR/LBR and CPR. No difference in the impact of ESI was observed between fresh and frozen embryo transfer.

CONCLUSION(S)

Current evidence does not support performing ESI with the purpose of improving the success of a first ET attempt.

Effects of autologous platelet-rich plasma on implantation and pregnancy in repeated implantation failure: A pilot study

BACKGROUND

Repeated implantation failure (RIF) is a major challenge in reproductive medicine and despite several methods that have been described for management, there is little consensus on the most effective one.

OBJECTIVE

This study was conducted to evaluate the effectiveness of platelet-rich plasma in improvement of pregnancy rate in RIF patients.

MATERIALS AND METHODS

Twenty women with a history of RIF who were candidates for frozen-thawed embryo transfer were recruited in this study. Intrauterine infusion of 0.5 ml of platelet-rich plasma that contained platelet 4-5 times more than peripheral blood sample was performed 48 hrs before blastocyst transfer.

RESULTS

Eighteen participants were pregnant with one early miscarriage and one molar pregnancy. Sixteen clinical pregnancies were recorded and their pregnancies are ongoing.

CONCLUSION

According to this study, it seems that platelet-rich plasma is effective in improvement of pregnancy outcome in RIF patients.