Does the dysregulation of matrix metalloproteinases contribute to recurrent implantation failure?

TIMP2 rs2277698 polymorphism associated with adverse IVF outcomes in Han Chinese women

Background

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are critical regulators of extracellular matrix (ECM) proteolysis and play a pivotal role in trophoblast invasion during embryo implantation. This study aimed to investigate the effects of single-nucleotide polymorphisms (SNPs) in MMP and TIMP genes on clinical outcomes in women undergoing in vitro fertilization (IVF).

Methods

This retroprospective study included 1014 women undergoing their first fresh IVF cycle without donor eggs at Lee Women's Hospital between January 2014 and December 2015. Peripheral blood samples were collected from all participants for DNA extraction and SNP genotyping using real-time polymerase chain reaction. The study focused on three SNPs: TIMP1 (rs4898 C/T), TIMP2 (rs2277698 C/T), and MMP2 (rs243865 C/T). Associations between these SNPs and IVF outcomes, including clinical pregnancy, embryo implantation, abortion, and live birth rates, were analyzed.

Results

Among 560 patients analyzed, no significant differences were observed in baseline characteristics between the live birth and non-live birth groups. However, the minor alleles (CT+TT) of MMP2 (rs243865) and TIMP2 (rs2277698) were significantly more frequent in the non-live birth group (MMP2: 24.4% vs. 17.7%, p = 0.044; TIMP2: 48.1% vs. 34.4%, p = 0.001). In contrast, no significant differences in the genotype distribution of TIMP1 (rs4898) were noted between the groups. Logistic regression analysis identified the minor T allele of TIMP2 as a significant predictor of non-live birth (adjusted odds ratio: 1.725; 95% CI: 1.217-2.445; p = 0.002). Combined genotypes of MMP2/TIMP2, such as CC/CT+TT and CT+TT/CT+TT, were associated with an increased risk of non-live birth, even after adjusting for covariates.

Conclusions

The study demonstrates that the minor T allele of TIMP2 (rs2277698 C/T) is associated with poor IVF outcomes, particularly non-live birth. This finding highlights the potential role of genetic variations in TIMP2 in influencing clinical outcomes of IVF. Further research is warranted to elucidate the underlying mechanisms in larger and more diverse populations.

Molybdenum interferes with MMPs/TIMPs expression to reduce the receptivity of porcine endometrial epithelial cells

To investigate the effect of trace element molybdenum (Mo) on the receptivity of porcine endometrial epithelial cells (PEECs) and evaluate Mo toxicity and its potential molecular mechanisms, Mo-treated PEECs models were established by incubating the cells with various concentrations of medium containing Mo (0, 0.005, 0.020, 0.200, and 5 mmol/L MoNa2O4·2H2O). The results showed that Mo disrupted the morphology and ultrastructure of PEECs, triggered blurred cell edges, cell swelling, cell cycle arrest, and increased apoptosis. At the molecular level, Mo treatment activated the TGF-β1/SMAD2 and PI3K/AKT1 pathways, causing a significant increase in matrix metalloproteinase (MMP)-9 and MMP-2 protein expression. Accompanied by markedly increased tissue inhibitors matrix metalloproteinase (TIMP)-2 and decreased TIMP-1, the balance of MMP2/TIMP-2 and MMP-9/TIMP-1 were disrupted. Ultimately, the receptivity of PEECs was destroyed by excessive Mo, which is revealed by the significant decrease of receptive marker molecules, including leukemia inhibitory factor (LIF), integrins β3 (ITGβ3), heparin-binding epidermal growth factor (HB-EGF), and vascular endothelial growth factor (VEGF). To sum up, the current study demonstrated the potential toxicity of Mo to PEECs, indicating reproductive toxicity at high Mo concentrations and suggesting that the content of Mo should be evaluated as a potential risk factor.

Enhancing uterine receptivity for embryo implantation through controlled collagenase intervention

Ineffective endometrial matrix remodeling, a key factor in infertility, impedes embryo implantation in the uterine wall. Our study reveals the cellular and molecular impact of human collagenase-1 administration in mouse uteri, demonstrating enhanced embryo implantation rates. Collagenase-1 promotes remodeling of the endometrial ECM, degrading collagen fibers and proteoglycans. This process releases matrix-bound bioactive factors (e.g., VEGF, decorin), facilitating vascular permeability and angiogenesis. Collagenase-1 elevates embryo implantation regulators, including NK cell infiltration and the key cytokine LIF. Remarkably, uterine tissue maintains structural integrity despite reduced endometrial collagen fiber tension. In-utero collagenase-1 application rescues implantation in heat stress and embryo transfer models, known for low implantation rates. Importantly, ex vivo exposure of human uterine tissue to collagenase-1 induces collagen de-tensioning and VEGF release, mirroring remodeling observed in mice. Our research highlights the potential of collagenases to induce and orchestrate cellular and molecular processes enhancing uterine receptivity for effective embryo implantation. This innovative approach underscores ECM remodeling mechanisms critical for embryo implantation.

Comparing intra-uterine injection of mononuclear cells and platelet-rich plasma on the pregnancy rate of women with recurrent implantation failure: An RCT

Background

Recurrent implantation failure (RIF) can be explained mainly by improper crosstalk between the embryo and endometrium. The T-helper1/T-helper2 profile balance influences effective embryo implantation. Endometrial immunomodulation via intrauterine injection of activated peripheral blood mononuclear cells (PBMCs) or autologous platelet-rich plasma (PRP) is a potentially efficient treatment option.

Objective

This study aims to examine the biochemical and clinical pregnancies resulting from the intrauterine administering of activated PBMCs and PRP in RIF women.

Materials and Methods

This randomized clinical trial study was done in the Rooya Infertility Treatment Center, Qom, Iran from November 2022 to April 2024. 96 women with at least 2 RIFs were randomized into control, PBMC, and PRP groups. Briefly, 3 ml of blood sample was collected and PBMCs were isolated using Ficoll separation solution, and cultured for 72 hr. PRP was separated from 10 ml of peripheral blood through centrifugation. 2 days before embryo transfer PBMCs or PRP were transferred into the endometrial cavity.

Results

Except for the duration of infertility, which was higher in the PBMC group, all other baseline characteristics were not statistically different. Moreover, a significantly higher rate of biochemical pregnancy was observed in the PRP (10/32) and PBMC (12/32) groups compared to the control (3/32) (p = 0.027), while the rate of clinical pregnancy was only significantly higher in the PBMC group (10/32) than in the control group (2/32) (p = 0.038).

Conclusion

Neither PBMC nor PRP interventions exhibited a substantial advantage over one another regarding biochemical and clinical pregnancy rates.

The Contribution of Proteomics in Understanding Endometrial Protein Expression in Women with Recurrent Implantation Failure

Recurrent implantation failure (RIF) poses a significant challenge in assisted reproductive technology (ART) outcomes. The endometrium plays a crucial role in embryo implantation, and its protein expression profile is integral in determining receptivity. Proteomics has emerged as a valuable tool in unraveling the molecular intricacies underlying endometrial receptivity and RIF. The aim of the present review is to analyze the contribution of proteomics to the understanding of endometrial protein expression in women with RIF, based on the results of significant proteomic studies. Medline/Pubmed databases were searched using keywords pertaining to proteomics combined with terms related to RIF. 15 studies were included in the present review. Several proteins have been found to exbibit differential expression in endometrial biopsies and fluid samples between fertile women and women with RIF during the receptive endometrial phase. The profile of endometrial proteins varied significantly among the studies. Nevertheless, similar changes in the expression levels of annexin-6, progesterone receptor, MMP-2, and MMP-9 in the endometrium of women with RIF, were found in more than one study indicating that certain proteins could potentially be effective biomarkers of endometrial receptivity. Proteomics contributes significantly to the understanding of protein expression in the endometrium of women with RIF and the analysis of proteins in endometrial fluid are promising for improving the clinical management of RIF.

Endometrium Immunomodulation to Prevent Recurrent Implantation Failure in Assisted Reproductive Technology

After more than four decades of assisted reproductive technology (ART) practice worldwide, today more than 60% of women undergoing in vitro fertilization (IVF) treatments fail to become pregnant after the first embryo transfer and nearly 20% of patients are suffering from unexplained recurrent implantation failures (RIFs) and repeated pregnancy loss (RPL). The literature reported different causes of RIF–RPL, mainly multifactorial, endometrial and idiopathic. RIF remains a black box because of the complicated categorization and causes of this physio-pathological dysregulation of implantation and pregnancy process after ovarian stimulation. Many options were suggested as solutions to treat RIF–RPL with controversial results on their usefulness. In this article, we reviewed different possible therapeutic options to improve implantation rates and clinical outcomes. Based on our experience we believe that endometrium immunomodulation after intrauterine insemination of activated autologous peripheral blood mononuclear cells (PBMCs) or platelet-rich plasma (PRP) can be a promising therapeutic solution. On the other hand, peripheral lymphocyte balance typing, specific cytokines and interleukins profiling can be proposed as predictive biomarkers of implantation before embryo transfer.

Follicular Fluid Growth Factors and Interleukin Profiling as Potential Predictors of IVF Outcomes

Growth hormone (GH) has gained attention as an anti-aging compound enhancing oocyte quality. In fact, GH is known to activate intrafollicular metabolic events for oocyte maturation. Insulin growth factor I (IGF1) is another ovarian growth factor that mediates the FSH and GH actions. Cytokines could also increase IVF outcomes. Indeed, IL-6 is a pleiotropic cytokine with multiple cellular effects that can vary based on the physiological environment. IL-6 may also play an important role in follicular development (Yang et al., J Assist Reprod Genet, 2020, 37 (5), 1171–1176). Clinical studies have been performed to explore the potential role of IL-6 in human oocyte maturation and subsequent embryonic development. To date, the answers are not conclusive. During peri-implantation, many cytokines balances are regulated like pro-inflammatory and anti-inflammatory interleukins. The pro-inflammatory properties of IL-17 and its impact on the tumor microenvironment or autoimmune diseases are characterized, but new dimensions of IL-17 activity that promotes embryo implantation are not well explored. In the search for answers, our study compared concentrations of growth factors IGF1, GH, and interleukins IL-6 and IL-17 in the follicular fluid (FF) from 140 women divided into two groups depending on bad (G1) or good prognosis (G2) and investigated the relationships between these FF components’ levels and the main parameters of IVF. GH, IGF1, and IL-6 were significantly higher for G2. For GH, it was negatively correlated to patient age and positively correlated to maturity rate and IGF1. Moreover, GH and IGF1 were correlated to the top embryo rate and cumulative pregnancy rate. Regarding IL-6, it was correlated to IGF1 level, endometrium thickness, and implantation rate. As for IL-17, it was only correlated to IL-6. Consequently, all these FF components were predictive of oocyte quality except IL-17. GH seemed to be the best biomarker of this quality.

Pre-implantation triclosan exposure alters uterine receptivity through affecting tight junction protein†

Triclosan (TCS) is a broad-spectrum antibacterial agent and widely exists in environmental media and organisms. TCS exposure was reported to have adverse effects on reproduction including embryo implantation disorder. During the embryo implantation window, it is vital that the endometrium develops into a receptive state under the influence of ovarian hormones. However, the effect of TCS on embryo implantation and endometrial receptivity remains unclear. In current study, we found decreased embryo implantation rate, serum estrogen (E2) and progesterone (P4) levels in mice exposed to TCS from gestation day (GD) 0.5 to 5.5. Through RNA-seq, we identified nearly 800 differentially expressed genes (DEGs), which were enriched in pathways including uterus development, inflammatory response and immune system process. Among those enriched pathways, the tight junction pathway is essential for the establishment of receptive state of endometrium. Then, genes involved in tight junction pathway including Cldn7, Cldn10 and Crb3 were validated by RT-qPCR and the results were consistent with the RNA-seq. Through immunofluorescence staining and western blotting, we confirmed that the tight junction protein levels of CLDN7 and CRB3 were increased. All these findings suggest that pre-implantation TCS exposure reduces the rate of embryo implantation through up-regulating the expression of tight junction genes and affecting the receptivity of endometrium. Our data could be used to determine the sensitive time frame for TCS exposure and offer new strategy to prevent implantation failure.

The role of extracellular matrix on unfavorable maternal–fetal interface: focusing on the function of collagen in human fertility

Extracellular matrix (ECM) is characterized as widespread, abundant, and pluripotent. Among ECM members, collagen is widely accepted as one of the most prominent components for its essential structural property that can provide a scaffold for other components of ECM and the rich biological functions, which has been extensively used in tissue engineering. Emerging evidence has shown that the balance of ECM degradation and remodeling is vital to regulations of maternal–fetal interface including menstrual cycling, decidualization, embryo implantation and pregnancy maintenance. Moreover, disorders in these events may eventually lead to failure of pregnancy. Although the improvement of assisted conception and embryo culture technologies bring hope to many infertile couples, some unfavorable outcomes, such as recurrent implantation failure (RIF), recurrent pregnancy loss (RPL) or recurrent miscarriage (RM), keep troubling the clinicians and patients. Recently, in vitro three-dimensional (3D) model mimicking the microenvironment of the maternal–fetal interface is developed to investigate the physiological and pathological conditions of conception and pregnancy. The progress of this technology is based on clarifying the role of ECM in the endometrium and the interaction between endometrium and conceptus. Focusing on collagen, the present review summarized the degradation and regulation of ECM and its role in normal menstruation, endometrium receptivity and unsatisfying events occurring in infertility treatments, as well as the application in therapeutic approaches to improve pregnancy outcomes. More investigations about ECM focusing on the maternal–fetal interface interaction with mesenchymal stem cells or local immunoregulation may inspire new thoughts and advancements in the clinical application of infertility treatments.

Graphical abstract

Research progress of endometrial receptivity in patients with polycystic ovary syndrome: a systematic review

Polycystic ovary syndrome (PCOS) is a neuroendocrine heterogeneous disease that frequently occurs in women of reproductive age, causing serious damage to the fertility, quality of life, and physical and mental health of patients. The current studies have proved that satisfactory endometrial receptivity is one of the conditions that must be met during the process of spermatovum position, adhesion and invasion, as well as the subsequent blastocyst division and embryo development. Women with PCOS may suffer a series of pathological processes such as changes in the expression levels of hormones and related receptors, imbalances in the proportion of miscellaneous cytokines, insulin resistance, low-grade chronic inflammation and endometrial morphological changes, which will damage endometrial receptivity from various aspects and obstruct fertilized egg nidation and embryonic development, thus causing adverse reproductive health events including infertility and abortion. This article reviews the research progress about characteristics and related influencing factors of endometrial receptivity in PCOS patients.

Circulating MMP-7 and VEGF as potential predictive biomarkers for recurrent implantation failures

Recurrent implantation failure (RIF) is considered to be one of the major limiting factors of assisted reproductive technology (ART) programme success. The current study focused on the investigation of matrix metalloproteinases (MMPs), tissue inhibitors of MMPs (TIMPs), cytokines and cell adhesion molecules in peripheral blood (PB) and follicular fluid (FF) obtained from 44 women aged between 25 and 39 years old and undergoing intracytoplasmic sperm injection (ICSI). These women were divided into two groups: 22 RIF women with embryo implantation failures after the transfer of at least four fresh or frozen-thawed good quality embryos in a minimum of three ICSI cycles, and 22 ICSI success women (controls) who achieved a clinical pregnancy at their first ICSI attempt. The PB and FF samples were obtained from each patient on the day of oocyte retrieval. MMP-1, -2, -3, -7, -9, TIMP-1, -2, vascular endothelial growth factor (VEGF), leukaemia inhibitory factor (LIF), vascular cell adhesion molecule 1 (VCAM1) and intercellular adhesion molecules 1 (ICAM1) were analyzed using enzyme-linked immunosorbent assay of PB and FF. Our results showed significant decreases in PB MMP-7 and PB VEGF in the RIF group compared with controls [281.11 (33-614) pg/ml vs 119.92 (27-441) pg/ml; P-value = 0.030] and [82.54 (25.94-210.20) pg/ml vs 30.93 (13.62-193.33) pg/ml; P-value = 0.022; respectively]. Receiver operating characteristic (ROC) curve analysis showed informative area under the curve values for PB MMP-7, as well as for PB VEGF, making them able to be proposed as biomarkers of the RIF. Therefore, circulating MMP-7 and VEGF seem to play an interesting role in embryo implantation in in vitro fertilization (IVF)/ICSI cycles and could be proposed as circulating biomarkers of the RIF. These results could be helpful for clinicians and patients to choose the best rescue strategy and treatment to minimize implantation failure in women undergoing IVF/ICSI procedures after the first attempt.

Modifications of extracellular matrix features in the left and right uterine horns during the embryo pre-implantation period in Vicugna pacos

More than 98% of the pregnancies in South American camelids is carried out in the left uterine horn (LUH). Hence, embryos originated from right-ovary ovulations have to migrate to the contralateral or left uterine horn (LUH) to implant and survive. A reason for this unique pattern of embryo implantation has not been elucidated yet. In general, embryo implantation involves an extensive extracellular matrix (ECM) remodeling within the endometrium, in which collagen and matrix metalloproteinases (MMPs) play an essential role. Deregulation of collagen and MMPs has been related to embryo implantation failure, miscarriage, and infertility. Therefore, we hypothesized that ECM components in camelids could be involved in differential embryo implantation and consequently the high incidence of left horn gestations. The aim of this study was to describe and compare changes in ECM components in the left and right uterine horn of non-pregnant and 15 days pregnant alpacas. To test this hypothesis, the collagen content was evaluated by specific staining with Picrosirius Red and using ImageJ 1.42q software. Subsequently, gene expression of the following components of the MMP pathway was determined: MMP-2, -3, -7, -9, and -14, MMP substrates (COL1A2 and COL3A1), MMP inhibitors (TIMP1 and TIMP2), LGMN, an MMP activator, and EMMPRIN, an extracellular matrix metalloproteinase inducer. Uterine horns of pregnant alpacas exhibited a marked decrease in collagen content. In contrast, transcript expression of COL1A2 and COL3A1 was higher in the LUH of pregnant alpacas. Gene expression of MMP-3, -7, -9, -14, LGMN, and EMMPRIN were also higher in the LUH of pregnant animals, whereas MMP-2 gene expression was higher in the LUH of both pregnant and non-pregnant alpacas. Expression of TIMP1 and TIMP2 increased during pregnancy, with higher values in the LUH. In conclusion, expression of ECM components displayed a specific pattern depending on the uterine side and the physiological status (pregnant vs non-pregnant) of the animal. The increased expression of ECM transcripts in the left uterine horn during early pregnancy in alpacas suggests the involvement of these molecules in a highly regulated process leading to the implantation process.

Chloride intracellular channel 4 is dysregulated in endometrium of women with infertility and alters receptivity

The endometrium remodels in each menstrual cycle to become receptive in preparation for embryo implantation which occurs in the mid-secretory phase of the cycle. Failure of blastocyst adhesion and implantation cause infertility. We compared chloride intracellular channel 4 (CLIC4) expression in human endometrium from women with normal fertility and primary unexplained infertility in the mid-secretory/receptive phase of the menstrual cycle. CLIC4 localised to both the epithelial and stromal regions of the endometrium of fertile tissues across the cycle. CLIC4 expression was significantly reduced in the luminal and glandular epithelium and remained unchanged in the stromal region of mid-secretory infertile endometrium compared to fertile endometrium. siRNA knockdown of CLIC4 significantly compromised adhesive capacity of Ishikawa cells (endometrial epithelial cell line). This reduced adhesion and CLIC4 expression was associated with elevated SGK1, p53, SIRT1, BCL2 and MCL1 gene expression in the Ishikawa cells. CLIC4 expression was increased in primary human endometrial stromal cells during decidualization, however, siRNA knockdown of CLIC4 did not affect decidualization. Our data provide evidence that CLIC4 may regulate receptivity and facilitate blastocyst attachment initiating implantation. Reduced CLIC4 levels may be causative of implantation failure in women.

Chronic endometritis and reproductive failure: Role of syndecan-1

Chronic endometritis (CE) is an unusual inflammatory condition characterized by endometrial plasmacyte infiltration. It has a high prevalence in women with reproductive failure. Because of its characteristic localization patterns and molecular functions, syndecan-1 has been identified as a biomarker of plasmacyte, and syndecan-1 immunohistochemistry (IHC) becomes the most dependable diagnostic method for CE. In this review, we discuss the association between CE and reproductive failure, the clinicopathological characterization of CE, the function and expression of syndecan-1, the progress of syndecan-1 IHC in the diagnosis of CE, and the prediction of reproductive outcome.

Endometrium immunomodulation by intrauterine insemination administration of treated peripheral blood mononuclear cell prior frozen/thawed embryos in patients with repeated implantation failure

In assisted reproductive technology (ART) programmes, approximately 10% of infertile patients have at least two or three repeated implantation failures (RIFs) after an in vitro fertilization (IVF) protocol. Successful implantation mainly depends on local immune tolerance mechanisms involving a spectrum of cytokines, interleukins and growth factors. The latter have played pivotal roles in the recruitment of immune cells (and notably T-lymphocyte cells). In total, 250 couples participating in frozen-thawed embryo transfer programme were incorporated in a randomized clinical trial (peripheral blood mononuclear cells (PBMC) subgroup: n=122; control subgroup: n=128). In the PBMC group, a blood sample was collected 5 days before the scheduled frozen-thawed embryo transfer; PBMCs were isolated using Ficoll separation and then cultured for 72 h. Two days prior to embryo transfer, 0.4 ml of cultured PBMCs were transferred into the patient's uterus. Although the clinical pregnancy rate was higher in the PBMC group (34.4%) than in the control group (23.4%), this difference was not statistically significant (P=0.05 in a chi-squared test). Nevertheless, when we limited the analysis to patients with ≥3 RIFs (n=138), there was a significant difference in the clinical pregnancy rate between the PBMC group (38.6%) and the control group (19.7%; P=0.01). Our results imply that PBMC transfer can be part of effective fertility treatment for patients with RIF.