Beta3 integrin expression within uterine endometrium and its relationship with unexplained infertility

When the Embryo Meets the Endometrium: Identifying the Features Required for Successful Embryo Implantation

Evaluation of the optimal number of embryos, their quality, and the precise timing for transfer are critical determinants in reproductive success, although still remaining one of the main challenges in assisted reproduction technologies (ART). Indeed, the success of in vitro fertilization (IVF) treatments relies on a multitude of events and factors involving both the endometrium and the embryo. Despite concerted efforts on both fronts, the overall success rates of IVF techniques continue to range between 25% and 30%. The role of the endometrium in implantation has been recently recognized, leading to the hypothesis that both the "soil" and the "seed" play a central role in a successful pregnancy. In this respect, identification of the molecular signature of endometrial receptivity together with the selection of the best embryo for transfer become crucial in ART. Currently, efforts have been made to develop accurate, predictive, and personalized tests to identify the window of implantation and the best quality embryo. However, the value of these tests is still debated, as conflicting results are reported in the literature. The purpose of this review is to summarize and critically report the available criteria to optimize the success of embryo transfer and to better understand current limitations and potential areas for improvement.

AlphaVBeta3 Integrin expression within uterine endometrium in unexplained infertility: a prospective cohort study

BACKGROUND

Implantation defect is one of these contributing factors for unexplained infertility. In the mid-luteal phase, when implantation is expected to happen, Integrins expression is remarkably increased. So, Integrins could potentially serve as markers for the frame of the window of implantation. αVβ3 integrin could have a role as a potential receptor for embryonic attachment. The aim of the current study is to investigate whether the women with unexplained infertility have a pattern of expression of endometrial αvβ3 integrin that could differ from those who have normal fertility or not.

METHOD

Two groups of women have been included in this study. The first group was the Unexplained Infertility Group. This group included women diagnosed with unexplained primary infertility. The second group was the fertile Group, which included fertile parous women presented to the family planning clinic seeking contraception. 2D transvaginal ultrasound scan (TVS) was performed six days after detecting urinary LH surge. (TVS) was used to measure endometrial thickness, and subendometrial blood flow color Doppler Resistance Index (RI). On the same day of transvaginal ultrasound, endometrial samples were taken using the Endocell® office suction sampler for Immunohistochemistry (IHC) study using monoclonal mouse IgG antibodies to detect endometrial αvβ3 integrin.

RESULTS

Thirty-five fertile women with a diagnosis of unexplained infertility were included as a group I [Unexplained infertility Group] along with an equal number of fertile women as group II [Fertile Group]. The group of women with a diagnosis of unexplained infertility had a significantly lower αvβ3 integrin score when compared to the fertile group (median score 0, range:0-2 and median score 1, range: 1-3 and for infertile and fertile groups respectively, P < 0.0001). In addition, the unexplained infertility group had significantly higher subendometrial flow RI and Significantly thinner endometrial thickness.

CONCLUSION

This study showed that Alpha v Beta 3 integrin is a significantly lower in endometrium in cases of unexplained infertility, which may suggest that underexpression of Alpha v Beta 3 integrin in human endometrium could be linked to defective uterine receptivity, and play a role as an unrecognized cause of infertility in this population of women. We need larger studies of adequate statistical power, ideally investigating more than one menstrual cycle in the same woman, to investigate the usefulness of using these molecular molecules in clinical practice.

Endometrial flushing αVβ3 integrin, glycodelin and PGF2α levels for evaluating endometrial receptivity in women with polycystic ovary syndrome, myoma uteri and endometrioma

The aim of this cross-sectional study is to compare endometrial flushing fluid levels of α_Vβ₃ integrin, glycodelin and PGF2α during the midluteal phase of the menstrual cycle of women with polycystic ovary syndrome (PCOS, n = 20), myoma uteri (n = 20) and endometrioma (n = 19) with the healthy controls (n = 20). After collecting samples at the midluteal phase of ovulatory volunteers and storing them at -80 °C, α_Vβ₃ integrin, glycodelin and PGF2α levels were analyzed using ELISA. The mean ages of the groups were 28.90 ± 5.45, 37.25 ± 2.73, 32.84 ± 6.62 and 32.15 ± 5.18 in PCOS, myoma uteri, endometrioma and control groups, respectively. The α_Vβ₃ integrin level (ng/ml) was statistically significantly higher in endometrioma group (9.70 ± 1.72, p < 0.05) as compared to myoma uteri and control groups. Similarly, glycodelin level (ng/ml) was significantly higher in endometrioma group (341.04 ± 93.32) than PCOS (p < 0.01), myoma uteri (p < 0.001) and healthy subjects (p < 0.001). Moreover, PGF2α level (350.04 ± 464.50 ng/ml) was significantly higher in PCOS group relative to myoma uteri (p < 0.001), endometrioma (p < 0.05) and control (p < 0.05) groups. In conclusion, α_Vβ₃ integrin level was significantly higher in endometrioma subjects than those with myoma uteri and control groups; glycodelin level was significantly higher in endometrioma group than other three groups, and lastly, PCOS patients had significantly higher PGF2α levels than those patients with myoma uteri, endometrioma and controls.

Effect of 2,3',4,4',5-Pentachlorobiphenyl Exposure on Endometrial Receptivity and the Methylation of HOXA10

Polychlorinated biphenyls (PCBs) are one of the most common endocrine-disrupting chemicals and have obvious toxicity on human reproductive development. The aim of our study was to investigate the toxicity of chronic 2,3',4,4',5-pentachlorobiphenyl (PCB 118) exposure on embryo implantation and endometrial receptivity, with the possible mechanism of DNA methylation involved. Virgin CD-1 female mice (3 weeks old) were housed and orally treated with PCB 118 (0, 1, 10, 100 μg/kg) for a month. After mating with fertile males, the pregnant mice were killed on gestation day 4.5. Compared with the control group, implantation failures were observed in 1 μg/kg PCB 118- and 100 μg/kg PCB 118-treated groups. Abnormal endometrial morphology with open uterine lumens and densely compact stromal cells and poorly developed pinopodes were substantially in response to PCB 118 doses above, as well as the significant downregulation of implantation-associated genes (estrogen receptor 1, homeobox A10 [HOXA10], integrin subunit beta 3) and hypermethylation in the promoter region of HOXA10 further. It was confirmed that chronic exposure to PCB 118 produced an increased number of implantation failures in association with a defective uterine morphology during the implantation period. Alterations in methylation of HOXA10 could explain, at least in part, the mechanism of effects of PCB 118 exposure on the implantation process.

Integrins β1 and β3 are biomarkers of uterine condition for embryo transfer

Background

Clinical ovulation induction induces blood estrogen (E₂) in excess of physiological levels, which can hinder uterine receptivity. In contrast, progesterone produces the opposite clinical effect, suggesting that it might be capable of recovering the lost receptivity resulting from exposure to high estrogen levels. Integrins are the most widely used biological markers for monitoring uterine conditions. We studied progesterone-induced changes in integrin β expression patterns as biomarkers for changes in uterine receptivity in response to increased estrogen levels.

Methods

Endometrial biopsy samples from patients were screened for their estrogen (E₂) and progesterone (P4) content and expressing levels of integrin β1 and β3. Uterine receptivity was evaluated using human endometrial adenocarcinoma cells in an embryo attachment model. The respective and concatenated effects of embryo attachment and changes in the integrin β1 and β3 expression patterns on the adenocarcinoma cell plasma membranes in response to 100 nM concentrations of E₂ and P4 were evaluated.

Results

Increased blood E₂ concentrations were associated with significantly decreased the levels of integrin β3 expression in uterine biopsy samples. In vitro experiments revealed that a 100 nM E₂ concentration inhibited the distribution of integrin β3 on the plasma membranes of human endometrial adenocarcinoma cells used in the embryo attachment model, and resulted in decreased rates of embryo attachment. In contrast, P4 enhanced the expression of integrin β1 and promoted its distribution on the plasma membranes. Furthermore, P4 recovered the embryo attachment efficiency that was lost by exposure to 100 nM E₂.

Conclusions

Blood E2 and P4 levels and integrin β3 and β1 expression levels in uterine biopsy samples should be considered as biomarkers for evaluating uterine receptivity and determining the optimal time for embryo transfer.

Trial registration Trial number: ChiCTR-TRC-13003777; Name of registry: Chinese Clinical Trial Registry; Date of registration: 4 September 2013; Date of enrollment of the first study participant: 15 October 2013

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1052-0) contains supplementary material, which is available to authorized users.

Osteopontin and Integrin αvβ3 Expression during the Implantation Window in IVF Patients with Elevated Serum Progesterone and Oestradiol Level

Background: To explore whether endometrial receptivity is determined by osteopontin (OPN) and integrin αvβ3 expression in women with elevated serum progesterone (P) and/or oestradiol (E₂) who are undergoing in vitro fertilisation (IVF). Methods: According to serum hormone levels on the day of HCG administration, 33 infertile women were divided into 3 groups: the high E₂, high P, and high E₂ and P groups. The control group included 11 fertile, healthy women. Endometrial biopsy was performed on ovulation day + 7 to + 8 for all study participants, and the mRNA and protein expression levels of OPN and integrin αvβ3 were analyzed. Result: No statistically significant differences regarding OPN and integrin αvβ3 expression were found between infertile patients in the high P, high E₂, high E₂ and P and control groups. There was no significant correlation between OPN and integrin αvβ3 staining intensity during the implantation window biopsy in any of the groups studied. Conclusion: Endometrial OPN and integrant αvβ3 expression/co-expression is not impaired during the window of implantation in patients with high P, high E₂, or high E₂ and P levels. The clinical value of assessing endometrial receptivity with OPN and integrin αvβ3 seems to be uncertain.

Effect of Endometrial Injury on Secretion of Endometrial Cytokines and IVF Outcomes in Women with Unexplained Subfertility

In order to determine the effect of endometrial injury (EI) on in vitro fertilization (IVF) outcomes in women with unexplained subfertility and explore the relationship between EI and endometrial inflammatory cytokines, 66 women with unexplained subfertility undergoing IVF treatment were recruited. 38 patients in the EI group underwent EI in the mid-luteal phase of the cycle and 28 patients in the non-EI (NEI) group. According to the pregnancy outcome, the NEI and EI groups were divided into NEI-nonpregnant (NEI-NP), NEI-pregnant (NEI-P), EI-NP, and EI-P. All patients underwent aspiration of endometrial secretions immediately before embryo transfer. The concentrations of ten mediators were measured using Milliplex Magnetic Bead assay. The clinical pregnancy was significantly higher in the EI than in the NEI group. The concentrations of interleukin- (IL-) 6, IL-8, IL-12 (p70), IL-13, interferon- (IFN-) γ, monocyte chemotactic protein- (MCP-) 1, and vascular endothelial growth factor (VEGF) were significantly higher in the EI than the NEI group. The expression of IFN-γ and VEGF in the EI-P was significantly increased compared to the EI-NP group. These findings suggest that, in women with unexplained subfertility, endometrial injury might be a potential method to improve clinical pregnancy rates by promoting the expression of IFN-γ and VEGF.

Endometrial scratching to improve pregnancy rate in couples with unexplained subfertility: a randomized controlled trial

AIM

The aim of this study was to examine the effect of endometrial scratching in women with unexplained infertility.

MATERIAL AND METHODS

A randomized controlled trial was conducted in Mansoura University Teaching Hospital and a private practice setting. A total of 105 couples with unexplained infertility were randomly allocated into two groups: group A comprised 54 women who underwent endometrial scratching in the luteal phase of a spontaneous menstrual cycle; and group B included 51 women who underwent a placebo procedure. The main outcome measured was cumulative clinical pregnancy rate after 6 months and miscarriage rate.

RESULTS

Clinical pregnancy rate was significantly higher in the women experiencing endometrial biopsy than in the control group (25.9% and 9.8%, respectively, P = 0.04). There was no significant difference in miscarriage rate between pregnant women in the endometrial injury group and pregnant women in the control group (12.5% and 16.5%, respectively, P = 0.79).

CONCLUSIONS

Endometrial scratching may improve clinical pregnancy rates in couples with unexplained infertility. Adequately powered studies are mandated to confirm or refute the findings.

Administration of calcitonin promotes blastocyst implantation in mice by up-regulating integrin β3 expression in endometrial epithelial cells

STUDY QUESTION

Does exogenous calcitonin improve the efficiency of implantation in mice by increasing uterine receptivity?

SUMMARY ANSWER

The administration of calcitonin could improve the efficiency of implantation by increasing the expression of several receptivity-related genes in endometrial epithelial cells (EECs).

WHAT IS KNOWN ALREADY

Calcitonin is one of the biomarkers of uterine receptivity, which is transiently produced in the uterine epithelia during the period of implantation both in humans and mouse.

STUDY DESIGN, SIZE, DURATION

Hormone-replaced mice were used for in vivo experiments. To evaluate the effect of calcitonin on uterine receptivity, the expression of endometrial genes was analyzed 36 h after i.p. injection of 0.5 IU calcitonin in a treatment group versus saline in the control. To evaluate the effect of calcitonin on implantation efficiency in vivo, two groups received 0.5 IU or 2 IU calcitonin (i.p.) 24 h before embryo transfer, and a control group received saline (i.p.) (n = 18 mice per group). Implantation sites were counted 7 days after embryo transfer. The RL95-2 human endometrial carcinoma cell line was used to study the mechanisms underlying the effect of calcitonin on gene expression in the endometria. Using an in vitro model of endometrium-trophoblast interaction, established with RL95-2 cells and JAR (human choriocarcinoma cell line) trophoblast, endometrial receptivity was evaluated by comparing attachment and outgrowth of JAR spheroids in control and treatment groups.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Uterine receptivity in ovariectomized mice was induced by injection of estradiol and progesterone. Expression of eight genes in murine endometrium and RL95-2 cells was analyzed by real-time RT-PCR, western blot, immunohistochemical analysis, flow cytometry and enzyme-linked immunosorbent assay. We tested the effects of a protein kinase C inhibitor, matrigel and an antibody against integrin αvβ3 using RL95-2 cells and performed attachment and outgrowth assays using the in vitro model of endometrium-trophoblast interaction. Implantation efficiency was evaluated by counting the implantation sites after embryo transfer.

MAIN RESULTS AND THE ROLE OF CHANCE

Calcitonin up-regulated αvβ3 in RL95 cells, which in turn resulted in increased levels of the leukemia inhibitory factor (LIF) and heparin binding-epidermal growth factor (HB-EGF) mRNA (both P < 0.01 versus control) and protein (both P < 0.05 versus control). The attachment and expansion of JAR spheroids was promoted by pretreatment of EECs with calcitonin (P < 0.05 versus control) together with significantly increased expression of αvβ3, LIF and HB-EGF. Moreover, the injection of calcitonin in the preimplantation phase increased the total number of implantation sites in treatment groups (55 in control versus 78 and 85 in 0.5 and 2 IU groups, respectively). Compared with the control group (3.11 ± 2.14), the average number of implantation sites in the 2 IU calcitonin treatment group increased (4.72 ± 1.87, P = 0.022).

LIMITATIONS, REASONS FOR CAUTION

Experiments were performed in mice and human cell lines but not in primary cultures of human endometrial cells.

WIDER IMPLICATIONS OF THE FINDINGS

The findings presented here have important implications, in that calcitonin administration (currently used for treatment of hypercalcemia or osteoporosis) may have clinical benefits in assisted reproduction programs, by facilitating endometrial receptivity and embryo implantation. However, further studies are required to confirm these findings.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by National Science Foundation of China (No. 81170619). There are no financial or commercial conflicts in this study.

Short-term effects of thyroid hormones during development: Focus on signal transduction

Extranuclear or nongenomic effects of thyroid hormones are mediated by receptors located at the plasma membrane or inside cells, and are independent of protein synthesis. Recently the alphaVbeta3 integrin was identified as a cell membrane receptor for thyroid hormones, and a wide variety of nongenomic effects have now been shown to be induced through binding of thyroid hormones to this receptor. However, also other thyroid hormone receptors can produce nongenomic effects, including the cytoplasmic TRalpha and TRbeta receptors and probably also a G protein-coupled membrane receptor, and increasing importance is now given to thyroid hormone metabolites like 3,5-diiodothyronine and reverse T(3) that can mimick some nongenomic effects of T(3) and T(4). Signal transduction from the alphaVbeta3 integrin may proceed through at least three independent pathways (protein kinase C, Src or mitogen-activated kinases) but the details are still unknown. Thyroid hormones induce nongenomic effects on at least three important Na(+)-dependent transport systems, the Na(+)/K(+)-ATPase, the Na(+)/H(+) exchanger, and amino acid transport System A, leading to a mitogenic response in embryo cells; but modulation of the same transport systems may have different roles in other cells and at different developmental stages. It seems that thyroid hormones in many cases can modulate nongenomically the same targets affected by the nuclear receptors through long-term mechanisms. Recent results on nongenomic effects confirm the old theory that the primary role of thyroid hormones is to keep the steady-state level of functioning of the cell, but more and more mechanisms are discovered by which this goal can be achieved.

An immunohistochemical study of beta1 integrin molecules (VLA-4, VLA-5, VLA-6) in all endometrial compartments of fertile and infertile women in Ahwaz-Iran

In some cases of infertility, implantation failure is due to a lack of expression of specific critical participating proteins such as cell adhesion molecules. The expression of beta 1 (beta1) integrin molecules within endometrial tissue has been proposed as a marker of uterine receptivity during the implantation window. Present study was conducted to assess uterine receptivity in women with unexplained infertility using beta1 integrin molecules within endometrial tissue in comparison with fertile women. This retrospective study was performed using a semiquantitative analysis on the immunohistochemical staining of beta1 integrins (VLA-4, VLA-5, VLA-6) in the mid-secretory phase of endometrium. Specimens were obtained from 30 fertile women and 28 infertile patients with a history of unexplained infertility. Chi-Square test was used to compare the expression and defect of beta1 integrin molecules between two groups. The results showed beta1 integrin molecules were present in fertile and infertile endometrial uterine tissues with different reactivity in different compartments. VLA-5 and VLA-6 expression on endometrial compartments showed an unrelated pattern of staining in either fertile or infertile women. The majority of glandular epithelial cells and stromal cells expressed VLA-4 integrin molecules in fertile endometrium. However, the reactivity with VLA-4 reduced significantly in both glandular epithelial cells and stromal cells in infertile women (p = 0.001). In conclusion differences may explain causes of unexplained infertility and suggests that VLA-4 integrin molecule may contribute in uterine endometrial receptivity at the time of the implantation window which requires more investigations in benign gynecologic diseases.