Downregulation of Human Endometrial IL-18 by Exogenous Ovarian Steroids

The Next Frontier in ART: Harnessing the Uterine Immune Profile for Improved Performance

Assisted reproduction techniques have improved considerably in recent decades, but despite these advances, success rates remain relatively low. Endometrial immune profiling involves the analysis of cytokine biomarkers in the endometrium during the mid-luteal phase. This profiling aims to provide insights into the immune environment of the uterus. The aim is to identify immune disturbances and thus guide the development of personalized therapeutic approaches. The first part of the review looks back at the emergence of innovative concepts, highlighting the specificity of the human uterine environment at the time of implantation. Based on this new knowledge, biomarkers have been selected for endometrial immune profiling. The second part details the results of clinical studies conducted over the last ten years. These clinical results suggest that this approach can increase the rate of live births in patients suffering from repeated implantation failures or repeated pregnancy loss. Uterine immune profiling represents a clinical innovation that can significantly improve the performance of medically assisted reproduction treatments through personalized strategies tailored to the local immune profile. Innovation in personalized medicine for assisted reproduction is crucial to improving the success rates of fertility treatments, while reducing the risks and costs associated with ineffective or unnecessary interventions.

The expression and activity of Toll-like receptors in the preimplantation human embryo suggest a new role for innate immunity

STUDY QUESTION

Is the innate immunity system active in early human embryo development?

SUMMARY ANSWER

The pattern recognition receptors and innate immunity Toll-like receptor (TLR) genes are widely expressed in preimplantation human embryos and the pathway appears to be active in response to TLR ligands.

WHAT IS KNOWN ALREADY

Early human embryos are highly sensitive to their local environment, however relatively little is known about how embryos detect and respond to specific environmental cues. While the maternal immune response is known to be key to the establishment of pregnancy at implantation, the ability of human embryos to detect and signal the presence of pathogens is unknown.

STUDY DESIGN, SIZE, DURATION

Expression of TLR family and related genes in human embryos was assessed by analysis of published transcriptome data (n = 40). Day 5 (D-5) human embryos (n = 25) were cultured in the presence of known TLR ligands and gene expression and cytokine production measured compared to controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human embryos surplus to treatment requirements were donated with informed consent from several ART centres. Embryos were cultured to Day 6 (D-6) in the presence of the TLR3 and TLR5 ligands Poly (I: C) and flagellin, with gene expression measured by quantitative PCR and cytokine release into medium measured using cytometric bead arrays.

MAIN RESULTS AND THE ROLE OF CHANCE

TLR and related genes, including downstream signalling molecules, were expressed variably at all human embryo developmental stages. Results showed the strongest expression in the blastocyst for TLRs 9 and 5, and throughout development for TLRs 9, 5, 2, 6 and 7. Stimulation of Day 5 blastocysts with TLR3 and TLR5 ligands Poly (I: C) and flagellin produced changes in mRNA expression levels of TLR genes, including the hyaluronan-mediated motility receptor (HMMR), TLR5, TLR7, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and monocyte chemoattractant Protein-1 (MCP-1) (P < 0.05, P < 0.001 compared to unstimulated controls), and release into culture medium of cytokines and chemokines, notably IL8 (P = 0.00005 and 0.01277 for flagellin and Poly (I: C), respectively).

LIMITATIONS, REASONS FOR CAUTION

This was a descriptive and experimental study which suggests that the TLR system is active in human embryos and capable of function, but does not confirm any particular role. Although we identified embryonic transcripts for a range of TLR genes, the expression patterns were not always consistent across published studies and expression levels of some genes were low, leaving open the possibility that these were expressed from the maternal rather than embryonic genome.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first report of the expression and activity of a number of components of the innate immunity TLR system in human embryos. Understanding the role of TLRs during preimplantation human development may be important to reveal immunological mechanisms and potential clinical markers of embryo quality and pregnancy initiation during natural conception and in ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the Ministry of Higher Education, The State of Libya, the UK Medical Research Council, and the NIHR Local Comprehensive Research Network and NIHR Manchester Clinical Research Facility and the European Union’s Horizon 2020 Research and Innovation Programmes under the Marie Skłodowska-Curie Grant Agreement No. 812660 (DohART-NET). In accordance with H2020 rules, no new human embryos were sacrificed for research activities performed from the EU funding, which concerned only in silico analyses of recorded time-lapse and transcriptomics datasets. None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

n/a.

NK-92 cells change their phenotype and function when cocultured with IL-15, IL-18 and trophoblast cells

NK cell development is affected by their cellular microenvironment and cytokines, including IL-15 and IL-18. NK cells can differentiate in secondary lymphoid organs, liver and within the uterus in close contact with trophoblast cells. The aim was to evaluate changes in the NK cell phenotype and function in the presence of IL-15, IL-18 and JEG-3, a trophoblast cell line. When cocultured with JEG-3 cells, IL-15 caused an increase in the number of NKG2D+ NK-92 cells and the intensity of CD127 expression. IL-18 stimulates an increase in the amount of NKp44+ NK-92 cells and in the intensity of NKp44 expression by pNK in the presence of trophoblast cells. NK-92 cell cytotoxic activity against JEG-3 cells increased only in presence of IL-18. Data on changes in the cytotoxic activity of NK-92 cells against JEG-3 cells in the presence of IL-15 and IL-18 indicate the modulation of NK cell function both by the cytokine microenvironment and directly by target cells. IL-15 and IL-18 were present in conditioned media (CM) from 1st and 3rd trimester placentas. In the presence of 1st trimester CM and JEG-3 cells, NK-92 cells showed an increase in the intensity of NKG2D expression. In the presence of 3rd trimester CM and JEG-3 cells, a decrease in the expression of NKG2D by NK-92 cells was observed. Thus, culturing of NK-92 cells with JEG-3 trophoblast cells stimulated a pronounced change in the NK cell phenotype, bringing it closer to the decidual NK cell-like phenotype.

The Endometrial Immune Profiling May Positively Affect the Management of Recurrent Pregnancy Loss

Introduction

The endometrial immune profiling is an innovative approach based on the analysis of the local immune reaction occurring in the endometrium at the time of the embryo implantation. By documenting the local immune activation during the period of uterine receptivity, we aim to detect and correct potential imbalances before and at the very beginning of placentation. The main objective of the study was to analyze in women with a history of repeated pregnancy loss (RPL) the association of personalized strategies based on immune dysregulations with live birth rates. The secondary objective was to highlight the main prognostic factors for live births.

Methods

This is an observational retrospective analysis of 104 patients with RPL, included between January 2012 and December 2019. Inclusion criteria included a spontaneous fertility with at least three miscarriages, an assessment including a three-dimension ultrasound scan, an endometrial biopsy for uterine immune profiling and a follow-up over at least 6 months with personalized care if indicated after the complete assessment. We defined as a success if the patients had a live birth after the suggested plan, as a failure if the patient either did not get pregnant or experienced a new miscarriage after the targeted therapies.

Results

Uterine immune profiling was the only exploration to be significantly associated with a higher live birth rate (LBR) if a dysregulation was identified and treated accordingly (55% vs 45%, p=0.01). On the contrary, an absence of local dysregulation (resulting in an apparently balanced immune environment) was associated with a higher risk of a new miscarriage, suggesting that the cause inducing RPL still needed to be identified. Independently of age and AMH level, dysregulated immune profile is significatively associated with 3 times higher LBR than a non-deregulated profile (OR=3.4 CI 95%1.27-9.84) or five times in case of an overactive profile treated by immunotherapy (OR=5 CI 95% 1.65-16.5). The usage of ART was significantly associated with lower LBR regardless of the presence of a subfertility factor (p=0.012). Personalization of medical care using natural cycle or simple hormonal stimulation is associated with a significantly higher LBR than personalization including ART treatments regardless of maternal age and AMH level (OR= 2.9 CI 95% 1.03-8.88).

Conclusion

Our study suggests that some endometrial immune profiles with targeted management of RPL are associated with a higher rate of LBR. ART may be negatively associated with LBR.

Endometrial Immune Profiling: A Method to Design Personalized Care in Assisted Reproductive Medicine

Objective: To assess the efficiency of the endometrial immune profiling as a method to design personalized care to enhance the pregnancy rate in a large heterogeneous infertile population. We hypothesized that some reproductive failures could be induced by a uterine immune dysregulation which could be identified and corrected with a targeted plan.

Design: Prospective cohort study.

Setting: Multicentric study.

Intervention(s) and Main outcome measure(s): One thousand and seven hundred thirty-eight infertile patients had an immune profiling on a timed endometrial biopsy between 2012 and 2018. This test documented the absence or the presence of an endometrial immune dysregulation and identified its type. In case of dysregulation, a targeted personalized plan was suggested to the treating clinician aiming to supply the anomaly. One year after the test, the clinician was contacted to provide the outcome of the subsequent embryo transfer with the applied suggested plan.

Result(s): After testing, 16.5% of the patients showed no endometrial immune dysregulation, 28% had a local immune under-activation, 45% had a local immune over-activation, and 10.5% had a mixed endometrial immune profile. In patients with a history of repeated implantation failures (RIF) or recurrent miscarriages (RM), the pregnancy rate was significantly higher if an endometrial dysregulation was found and the personalized plan applied, compared to the patients with an apparent balanced immune profile (respectively 37.7 and 56% vs. 26.9 and 24%, p < 0.001). In contrast, in good prognosis IVF (in vitro fertilization) subgroup and patients using donor eggs, this difference was not significant between dysregulated and balanced subgroups, but higher pregnancy rates were observed in absence of dysregulation. For patients with immune over-activation, pregnancy rates were significantly higher for patients who had a test of sensitivity, regarding the type of immunotherapy introduced, when compared to the ones who did not (51 vs. 39.9%, p = 0.012).

Conclusion(s): Local endometrial immunity appears to be a new and important parameter able to influence the prognosis of pregnancy. Targeted medical care in case of local immune dysregulation resulted in significantly higher pregnancy rates in RIF and RM patients.

Effects of human chorionic gonadotropin, estradiol, and progesterone on interleukin-18 expression in human decidual tissues

Interleukin (IL)-18 is a proinflammatory cytokine which mediates a myriad of inflammatory responses during pregnancy. Changes in IL-18 levels have been linked to complications during pregnancy. This study was designed to assess the effects of estradiol, human chorionic gonadotropin (hCG), and progesterone on IL-18 expression in human decidual tissues. Uterine deciduas from women with normal pregnancy, spontaneous abortion, and progesterone treated spontaneous abortion were collected, and the effects of hormones on the viability of decidual cells and IL-18 secretion were detected by MTT and ELISA assays. We found that Estradiol, hCG, and progesterone inhibited decidual cell growth independent of dosage and time.IL-18 secretion in the spontaneous abortion group was increased in the decidual cells over time, but all hormones significantly reduced its secretion (p < 0.05). Our results indicate that estradiol, hCG, and progesterone can reduce IL-18 secretion in the cultured endometrial stromal cells from patients who experienced spontaneous abortion to the levels observed following normal pregnancy. Progesterone can significantly reduce IL-18 expression and increase growth of CD56+ CD16- uNK cells, suggesting that these activities may underlie the mechanism by which progesterone improves pregnancy outcomes.

The Uterine Immune Profile May Help Women With Repeated Unexplained Embryo Implantation Failure After In Vitro Fertilization

LABELED PROBLEM

Embryo implantation remains the main limiting factor in assisted reproductive medicine (20% success rate).

METHODS OF STUDY

An endometrial immune profiling was performed among 394 women with the previous history of repeated embryo implantation failures (RIF). The endometrial immune profile documented the ratio of IL-15/Fn-14 mRNA as a biomarker of uNK cell activation/maturation (together with the uNK cell count) and the IL-18/TWEAK mRNA ratio as a biomarker of both angiogenesis and the Th1/Th2 balance. According to their profile, we recommended personalized care to counteract the documented dysregulation and assessed its effects by the live birth rate (LBR) for the next embryo transfer.

RESULTS

Endometrial immune profiles appeared to be dysregulated in 81.7% of the RIF patients compared to control. Overactivation was diagnosed in 56.6% and low activation in 25%. The LBR among these dysregulated/treated patients at the first subsequent embryo transfer was 39.8%.

CONCLUSION

Endometrial immune profiling may improve our understanding of RIF and subsequent LBR if treated.

Caprine endometrial stromal cells modulate the effects of steroid hormones on cytokine secretion by endometrial epithelial cells in vitro

The main purpose of this study was to examine the effects of 17β-estradiol (E(2)) and progesterone (P(4)) on cytokine secretion by caprine endometrial epithelial cells (EEC) in vitro. Epithelial cells grown alone or in co-culture with stromal cells (ESC) were treated with E(2) or P(4), or both. Homogeneity of the endometrial cell populations was ascertained immunocytochemically. The quantities of cytokines secreted in this system were assessed by ELISA and their protein expression by Western blot. The exposure of EEC to P(4) alone or in combination with E(2) significantly increased the amount of TGF-β1, TNF-α and IL-18 secretion, whereas E(2) had no effect on the synthesis of these cytokines. When epithelial cells were co-cultured with ESC, the secretion of TGF-β1, TNF-α and IL-18 by EEC significantly increased compared to that by EEC alone. However, the treatment with both steroids decreased the secretion of TNF-α, IL-18 and TGF-β1 by EEC in the presence of ESC. In contrast to TGF-β1, TNF-α and IL-18, the secretion of leukemia inhibitory factor (LIF) by EEC was not affected by E(2) and/or P(4) either directly or indirectly. The present results indicate that the interactions between caprine endometrial stromal and epithelial cells can modulate the secretion of TGF-β1, TNF-α and IL-18 by EEC exposed to E(2) and/or P(4)in vitro.

Stromal-epithelial interactions modulate the effect of ovarian steroids on goat uterine epithelial cell interleukin-18 release

A primary role of epithelial-stromal interactions in mediating steroid hormone action in the uterus has been established. The present study was undertaken to determine the mode of ovarian steroid action in regulating IL-18 release by goat endometrial epithelial cells (EECs) in the presence and absence of endometrial stromal cells (ESCs). Primary and telomerase-immortalized goat EECs grown alone or cocultured with ESCs were treated with two ovarian steroids, 17β-estradiol (E(2)) and progesterone (P(4)). The IL-18 mRNA and protein expression in EECs were studied by reverse transcript (RT) PCR, ELISA, and Western blot assay. The E(2) and/or P(4) treatment of EECs led to a significant increase in both IL-18 mRNA and protein expression either in the primary or in the immortalized EECs compared with that in EECs without the steroid treatment. However, in the presence of ESCs, IL-18 expression by EECs treated with steroids was significantly decreased compared with cells untreated with E(2) and/or P(4). In addition, significantly high abundance of IL-18 mRNA and protein expression by primary and telomerase-immortalized goat EECs was observed in the presence of ESCs compared with those cells without ESCs. These findings suggest that steroids are important for the control of IL-18 expression in goat EECs. Underlying ESCs are needed to mediate the inhibitory effects of steroids on the IL-18 secretory activity of goat EECs in vitro. The IL-18 abundance expressed by goat EECs in vitro are enhanced by underlying ESCs without the treatment of E(2) and/or P(4).

Differential expression and regulation of angiopoietin-2 in mouse uterus during preimplantation period

Angiogenesis is crucial to successful implantation and decidualization, however, as an important angiogenic growth factor, the effect of Ang-2 in the process of implantation and decidualization is still unknown. This study is to investigate the differential expression of Ang-2 in mouse uterus during early pregnancy and its regulation by steroid hormones using in situ hybridization and RT-PCR. There is no detectable Ang-2 mRNA signal on days 1-5 of pregnancy by in situ hybridization. On days 6-8, Ang-2 mRNA is mainly expressed in the primary decidua of mesometrial side, and the expression gradually increases. By RT-PCR, a significantly higher level of Ang-2 expression is observed on day 8 of pregnancy, although Ang-2 expression can be found through days 1-8. Similarly, Ang-2 is highly expressed in decidualized cells under artificial decidualization. In the ovariectomized mouse uterus, Ang-2 expression gradually increases after estrogen injection and with peak levels at 12 hr, while progesterone injection can cause a decline in uterine Ang-2 mRNA level, which reaches a nadir at 12 hr. These results suggest that Ang-2 may play a key role in the process of mouse decidualization. Estrogen can induce the expression of Ang-2 while progesterone can inhibit its expression in the ovariectomized mouse uterus.

Modulation of cytokine and chemokine secretions in rhesus monkey trophoblast co-culture with decidual but not peripheral blood monocyte-derived macrophages

PROBLEM

Decidual macrophages are thought to promote pregnancy success, in part through interactions with invading trophoblast cells in hemochorial placentation. However, the factors that constitute this regulatory cross talk are not well understood.

METHOD OF STUDY

Rhesus monkey decidual and peripheral blood-derived macrophages were co-cultured with primary Rhesus trophoblasts. Macrophage functions including cell-surface marker expression, antigen uptake and processing, in vitro migration, and cytokine and chemokine secretions were evaluated.

RESULTS

While most macrophage functions were unchanged by trophoblast co-culture, changes in the secretion of selected cytokines and the migration of trophoblasts were noted when decidual (but generally, not peripheral blood monocyte-derived) macrophages were cultured with trophoblasts. In addition, basal secretion differed significantly between peripheral blood-derived and decidual macrophages for a broad spectrum of cytokines. When trophoblasts were pre-treated with an anti-Mamu-AG antibody, 25D3, there was no change in cytokine or chemokine secretion.

CONCLUSION

Macrophage cytokine expression can be modulated by trophoblast co-culture, but it remains unclear how Mamu-AG is involved.

Divergent regulation of angiopoietin-1 and -2, Tie-2, and thrombospondin-1 expression by estrogen in the baboon endometrium

Estrogen has an important role in the reconstruction of a new vascular network in the endometrium during each menstrual cycle; however, the underlying mechanisms are incompletely understood. Angiopoietin-1 (Ang-1) promotes vessel assembly, whereas Ang-2 and thrombospondin-1 (TSP-1) cause vessel breakdown. To determine the potential effect of estrogen on the expression of these angioregulatory factors in the endometrium, Ang-1, Ang-2, TSP-1, and Tie-2 receptor mRNA levels were assessed by real-time reverse transcriptase polymerase chain reaction in glandular epithelial and stromal cells isolated from the endometrium of ovariectomized baboons treated acutely with estradiol. Corresponding protein expression was assessed by immunocytochemistry and the proximity ligation assay (PLA) during advancing stages of the baboon menstrual cycle. Serum estradiol levels in ovariectomized baboons were 400 pg/ml within 4-6 hr of estradiol treatment. Ang-1 mRNA levels in glandular epithelial cells increased threefold (P < 0.01) within 4 hr of estradiol administration. In contrast, TSP-1 mRNA levels decreased four- to fivefold (P < 0.01) in endometrial glandular epithelial and stromal cells 4-6 hr after estradiol, whereas Ang-2 and Tie-2 expression was unaltered. Immunostaining for Ang-1 increased, TSP-1 decreased, and Ang-2 and Tie-2 were unaltered in the endometrium during the secretory compared with the proliferative phase of the cycle. Endometrial Ang-1 protein expression, quantified by PLA, increased 10-fold (P < 0.05) between the early proliferative and late proliferative/mid-secretory phases of the menstrual cycle in association with the rise in estrogen. In summary, estrogen induced a rapid, divergent, and cell-specific change in expression of angiostimulatory and angioinhibitory growth factors in the endometrium of the nonhuman primate.

Associations of plasma pro-inflammatory cytokines, fibrinogen, viscosity and C-reactive protein with cardiovascular risk factors and social deprivation: the fourth Glasgow MONICA study

Circulating inflammatory markers [plasma fibrinogen, viscosity and C-reactive protein (CRP)] have been associated with cardiovascular risk factors. In part, these associations may reflect 'upstream' changes in pro-inflammatory cytokines - interleukin (IL)-6, IL-18 and tumour necrosis factor (TNF)alpha. These variables were measured in 1666 men and women aged 25-64 years and their associations with risk factors were studied. All six markers increased significantly with age. IL-18 and TNFalpha levels were higher, and fibrinogen levels lower, in males. Oral contraceptive use increased levels of CRP, whilst postmenopausal women had elevated IL-18 levels. Inflammatory markers were also associated with components of the metabolic syndrome. Most inflammatory markers showed an increasing trend with alcohol consumption in men and a decreasing trend in women, and increasing trends with level of smoking. Inflammatory markers generally showed strong positive associations with social deprivation. After adjustment for classical risk factors, IL-6, IL-18 and TNFalpha retained significant associations with social deprivation only in men (P < 0.008). We conclude that pro-inflammatory cytokines are associated with several cardiovascular risk factors including social deprivation, and may mediate some of their associations with 'downstream' inflammatory markers (fibrinogen, viscosity and CRP).

Facilitation of decidualization by locally produced ghrelin in the human endometrium

Ghrelin acting via the growth hormone secretagogue receptor (GHS-R) stimulates GH secretion from pituitary glands. Both ligand and receptor are present in the pituitary, hypothalamus and many peripheral tissues including the uterus. This study demonstrates the cyclical expression of GHS-R and ghrelin in human endometrium. mRNA and protein for ghrelin and GHS-R were examined using RT-PCR and immunohistochemistry. Both ghrelin and GHS-R mRNA levels were highest in the secretory phase, with lower levels in the mid-proliferative phase and even lower expression in the menstrual phase. Immunoreactive ghrelin and GHS-R were confined predominantly to glandular epithelial and stromal cells with the greatest intensity of staining in secretory phase samples, consistent with the RT-PCR data. Additionally, we examined ghrelins effect on the decidualization of human endometrial stromal cells (HESCs) combined with sex steroid and cAMP treatments using prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) production as markers of decidualization. Ghrelin administered in combination with sex steroids to HESC, resulted in an increase in PRL and IGFBP-1 production above that obtained with cAMP, or sex steroids alone (P<0.001) whereas ghrelin in combination with cAMP inhibits the action of cAMP. These findings have potential clinical applications for the regulation of fertility.