Temporal analysis of connexin43 protein and gene expression throughout the menstrual cycle in human endometrium

Endometrial scratching in women undergoing IVF/ICSI: an individual participant data meta-analysis

BACKGROUND

In IVF/ICSI treatment, the process of embryo implantation is the success rate-limiting step. Endometrial scratching has been suggested to improve this process, but it is unclear if this procedure increases the chance of implantation and live birth (LB) and, if so, for whom, and how the scratch should be performed.

OBJECTIVE AND RATIONALE

This individual participant data meta-analysis (IPD-MA) aims to answer the question of whether endometrial scratching in women undergoing IVF/ICSI influences the chance of a LB, and whether this effect is different in specific subgroups of women. After its incidental discovery in 2000, endometrial scratching has been suggested to improve embryo implantation. Numerous randomized controlled trials (RCTs) have been conducted, showing contradicting results. Conventional meta-analyses were limited by high within- and between-study heterogeneity, small study samples, and a high risk of bias for many of the trials. Also, the data integrity of several trials have been questioned. Thus, despite numerous RCTs and a multitude of conventional meta-analyses, no conclusion on the clinical effectiveness of endometrial scratching could be drawn. An IPD-MA approach is able to overcome many of these problems because it allows for increased uniformity of outcome definitions, can filter out studies with data integrity concerns, enables a more precise estimation of the true treatment effect thanks to adjustment for participant characteristics and not having to make the assumptions necessary in conventional meta-analyses, and because it allows for subgroup analysis.

SEARCH METHODS

A systematic literature search identified RCTs on endometrial scratching in women undergoing IVF/ICSI. Authors of eligible studies were invited to share original data for this IPD-MA. Studies were assessed for risk of bias (RoB) and integrity checks were performed. The primary outcome was LB, with a one-stage intention to treat (ITT) as the primary analysis. Secondary analyses included as treated (AT), and the subset of women that underwent an embryo transfer (AT+ET). Treatment-covariate interaction for specific participant characteristics was analyzed in AT+ET.

OUTCOMES

Out of 37 published and 15 unpublished RCTs (7690 participants), 15 RCTs (14 published, one unpublished) shared data. After data integrity checks, we included 13 RCTs (12 published, one unpublished) representing 4112 participants. RoB was evaluated as 'low' for 10/13 RCTs. The one-stage ITT analysis for scratch versus no scratch/sham showed an improvement of LB rates (odds ratio (OR) 1.29 [95% CI 1.02-1.64]). AT, AT+ET, and low-RoB-sensitivity analyses yielded similar results (OR 1.22 [95% CI 0.96-1.54]; OR 1.25 [95% CI 0.99-1.57]; OR 1.26 [95% CI 1.03-1.55], respectively). Treatment-covariate interaction analysis showed no evidence of interaction with age, number of previous failed embryo transfers, treatment type, or infertility cause.

WIDER IMPLICATIONS

This is the first meta-analysis based on IPD of more than 4000 participants, and it demonstrates that endometrial scratching may improve LB rates in women undergoing IVF/ICSI. Subgroup analysis for age, number of previous failed embryo transfers, treatment type, and infertility cause could not identify subgroups in which endometrial scratching performed better or worse. The timing of endometrial scratching may play a role in its effectiveness. The use of endometrial scratching in clinical practice should be considered with caution, meaning that patients should be properly counseled on the level of evidence and the uncertainties.

Endometrial scratching during hysteroscopy in women undergoing in vitro fertilization: a systematic review and meta-analysis

Objective

Endometrial scratching (ES) during hysteroscopy before embryotransfer (ET) remains doubtable on whether it benefits the reproductive outcomes. The optimal technique is not clear and repeated implantation failure as a challenging field in in vitro fertilization (IVF) seems to be the springboard for clinicians to test its effectiveness.

Methods

Medline, PMC, ScienceDirect, Scopus, CENTRAL, Google Scholar were searched from their inception up to April 2023 for studies to evaluate the effectiveness of adding endometrial scratching during hysteroscopy before ET.

Results

The initial search yielded 959 references, while 12 eligible studies were included in the analyses, involving 2,213 patients. We found that hysteroscopy and concurrent ES before ET resulted in a statistically significant improvement in clinical pregnancy rate (CPR) [RR = 1.50, (95% CI 1.30-1.74), p < 0.0001] and live birth rate (LBR) [RR = 1.67, (95% CI 1.30-2.15), p < 0.0001] with no statistically significant difference on miscarriage rate [RR = 0.80 (95% CI 0.52-1.22), p = 0.30].

Conclusion

Our meta-analysis suggests that hysteroscopy with concurrent ES may be offered in IVF before ET as a potentially improving manipulation. Future randomized trials comparing different patient groups would also provide more precise data on that issue, to clarify specific criteria in the selection of patients.

Systematic Review Registration

PROSPERO (CRD42023414117).

Endometrial Injury Upregulates Expression of Receptivity Genes in Women with Implantation Failure

BACKGROUND

Homeobox genes A10 (HOXA10) and A11 (HOXA11), members of the abdominal B gene family, are responsible for embryonic survival and implantation. This study was planned to investigate whether endometrial injury alters the expression of both transcripts in women with implantation failure.

METHODS

A total of 54 women with implantation failure were divided into two equal groups as experimental (scratching) and sham (no scratching). Participants in the scratching group were exposed to endometrial injury in the mid-luteal phase, and those in the sham group were exposed to endometrial flushing. The scratching group, but not the sham group, underwent prior endometrial sampling. A second endometrial sampling was performed on the scratching group in the mid-luteal phase of the following cycle. The mRNA and protein levels of the HOXA10 and 11 transcripts were determined in endometrial samples collected before and after injury/flushing. Participants in each group underwent IVF/ET in the cycle after the second endometrial sampling.

RESULTS

Endometrial injury caused a 60.1-fold (p < 0.01) increase in HOXA10 mRNA and a 9.0-fold increase in HOXA11 mRNA (p < 0.02). Injury resulted in a significant increase in both HOXA10 (p < 0.001) and HOXA11 protein expression (p < 0.003). There was no significant change in HOXA10 and 11 mRNA expressions after flushing. Clinical pregnancy, live birth, and miscarriage rates of the both groups were similar.

CONCLUSIONS

Endometrial injury increases homeobox transcript expression at both mRNA and protein levels.

The effect of hysteroscopy and conventional curretage versus no hysteroscopy on live birth rates in recurrent in vitro fertilisation failure: a retrospective cohort study from a single referral centre experience

This retrospective cohort study aimed to evaluate the effect of hysteroscopy and endometrial scratching (ES) in patients with recurrent implantation failure (RIF) who do not have an intracavity pathology. The authors retrospectively collected data of patients between 2014 and 2019 from a single centre. The study analysed 350 unexplained RIF patients, of whom, 225 underwent hysteroscopy and endometrial scratching, and 125 did not have a hysteroscopy prior to an IVF cycle. Pregnancy rates among post endometrial scratching and no endometrial scratching cycles were 35.6% versus 27.2%, (p = .048), clinical pregnancy rates were 32.9% versus 21.6% (p = .026) and live birth rates were 26.2% versus 19.2% (p = .039). Although it is not possible to distinguish whether hysteroscopy or injury is effective in improving live birth results, the authors thought that endometrial injury with gentle conventional curettage is effective in patients with recurrent implantation failure.IMPACT STATEMENTWhat is already known on this subject? Hysteroscopy and endometrial injury improve pregnancy outcomes in IVF cycles, but definitive conclusions have been uncertain.What do the results of this study add? The study showed that endometrial injury with gentle conventional curettage during hysteroscopy significantly improved the pregnancy rates of RIF patients compared to the non-hysteroscopy group.What are the implications of these findings for clinical practice and/or further research? In cases of recurrent implantation failure, even if hysteroscopy findings are normal, endometrial scratching in the follicular phase increases pregnancy rates compared to the non-hysteroscopy group.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The effect of endometrial scratch on pregnancy outcomes of frozen-thawed embryo transfer: a propensity score-matched study

AIMS

To study the effect of endometrial scratch (ES) performed on Days 2 to 5 of the menstrual cycle on pregnancy outcomes of frozen-thawed embryo transfer (FET).

MATERIALS AND METHODS

We conducted a retrospective study including 5769 women undergoing FET from January 2018 to August 2019. The endometrial scratching group (group ES) consisted of 827 patients and the control group (group non-ES) comprised 4942 patients. A propensity score matching (PSM) method using the nearest neighbor matching at a proportion of 1:1 was performed. Subsequently, we compared the pregnancy outcomes of each group after PSM.

RESULTS

After PSM, there were significant differences in implantation (36.1% vs. 47.0%, p = .005), clinical pregnancy (45.4% vs. 58.3%, p = .007), and live birth (33.5% vs. 47.2%, p = .003) rates in matched patients with two previous implantation failures. In the matched patients with at least three previous implantation failures, we also detected increase rates of implantation (31.0% versus 40.1%, p = .028), clinical pregnancy (39.8% versus 57.0%, p = .019), live birth (32.3% versus 47.3%, p = .036). In contrast, no significant difference in pregnancy outcomes was found in women with no previous implantation failure or only one failure.

CONCLUSIONS

Endometrial scratch on day 2 to day 5 of the menstrual cycle in women with at least two previous implantation failures who underwent FET increased their implantation, clinical pregnancy, and live birth rates, and did not increase miscarriage or ectopic pregnancy rates compared to the non-ES group.

The Spiny Mouse—A Menstruating Rodent to Build a Bridge From Bench to Bedside

Menstruation, the cyclical breakdown of the uterine lining, is arguably one of evolution's most mysterious reproductive strategies. The complexity and rarity of menstruation within the animal kingdom is undoubtedly a leading contributor to our current lack of understanding about menstrual function and disorders. In particular, the molecular and environmental mechanisms that drive menstrual and fertility dysregulation remain ambiguous, owing to the restricted opportunities to study menstruation and model menstrual disorders in species outside the primates. The recent discovery of naturally occurring menstruation in the Egyptian spiny mouse (Acomys cahirinus) offers a new laboratory model with significant benefits for prospective research in women's health. This review summarises current knowledge of spiny mouse menstruation, with an emphasis on spiral artery formation, inflammation and endocrinology. We offer a new perspective on cycle variation in menstrual bleeding between individual animals, and propose that this is indicative of fertility success. We discuss how we can harness our knowledge of the unique physiology of the spiny mouse to better understand vascular remodelling and its implications for successful implantation, placentation, and foetal development. Our research suggests that the spiny mouse has the potential as a translational research model to bridge the gap between bench to bedside and provide improved reproductive health outcomes for women.

The Current Role of Induced Endometrial Trauma (Endometrial Scratch) in Women Undergoing Infertility Treatment

Induced endometrial trauma, otherwise known as endometrial scratch is a simple technique that has been rapidly adopted into clinical practice, mainly for women having IVF treatment, in an attempt to increase pregnancy rates. The introduction of endometrial scratch followed early reports of improved clinical pregnancy rates in women with repetitive implantation failure after having the procedure and follows on from evidence from animal models in the early 20^th century suggesting that mechanical trauma to the endometrium can induce decidual changes. Due to the ease and low cost of the procedure, it has been rapidly adopted as an add-on to fertility treatments, in many cases where evidence is still lacking. Despite the initial publication of a large number of studies that demonstrated encouraging improvements in pregnancy rates in women who underwent this procedure, these studies were mainly limited by the small sample sizes and heterogeneity of their study populations, leading to limited validity of the evidence provided by these studies. More recently, three large randomized controlled studies have been published that paint a different picture regarding the value of this procedure. This article explores the evolution of the evidence and the current state of endometrial scratch as an adjuvant therapy for women undergoing IVF treatment.

Endometrial scratching for poor responders based on the Bologna criteria in ICSI fresh embryo transfer cycles: a preliminary retrospective cohort study

Objective

This study evaluated the effect of endometrial injury on pregnancy outcomes in patients with a poor ovarian response (POR), based on the Bologna criteria, who underwent intracytoplasmic sperm injection (ICSI) cycles.

Material and Methods

Sixty-eight patients were enrolled in this retrospective cohort study. All patients in the endometrial scratching group (group 1, n=32) and control group (group 2, n=36) underwent office hysteroscopy in the early follicular phase of the cycle before controlled ovarian stimulation. Group 1 also underwent endometrial scratching. The main outcome measure was the ongoing pregnancy rate.

Results

The study groups had similar baseline demographics, including age, body mass index, duration of infertility, number of ICSI cycles, and hormone levels. However, the antral follicle count was significantly higher in group 1 than in group 2 (4.2±1.9 vs 3.3±1.8; p<0.05). There were no significant group differences in ovarian stimulation characteristics (ovarian stimulation time, trigger day endometrial thickness, number of metaphase II oocytes), number of embryos transferred, or the ratio of embryo transfer on days 3 and 5. Moreover, there were no significant differences between groups 1 and 2 in the rates of chemical pregnancy (25% vs 19.4%), clinical pregnancy (15.6% vs 11.1%) or ongoing pregnancy (9.4% vs 8.3%) (p>0.05 for all).

Conclusion

Endometrial scratching did not improve pregnancy outcomes for patients meeting the Bologna criteria for a POR to ICSI cycles using fresh embryo transfer and the GnRH antagonist protocol.

Uterine bathing with sonography gel prior to IVF/ICSI-treatment in patients with endometriosis, a multicentre randomised controlled trial

STUDY QUESTION

What is the effect of uterine bathing with sonography gel prior to IVF/ICSI-treatment on live birth rates after fresh embryo transfer in patients with endometriosis?

SUMMARY ANSWER

After formal interim analysis and premature ending of the trial, no significant difference between uterine bathing using a pharmacologically neutral sonography gel compared to a sham procedure on live birth rate after fresh embryo transfer in endometriosis patients (26.7% vs. 15.4%, relative risk (RR) 1.73, 95% confidence interval (CI) 0.81-3.72; P-value 0.147) could be found, although the trial was underpowered to draw definite conclusions.

WHAT IS KNOWN ALREADY

Impaired implantation receptivity contributes to reduced clinical pregnancy rates after IVF/ICSI-treatment in endometriosis patients. Previous studies have suggested a favourable effect of tubal flushing with Lipiodol^® on natural conceptions. This benefit might also be explained by enhancing implantation through endometrial immunomodulation. Although recent studies showed no beneficial effect of endometrial scratching, the effect of mechanical stress by intrauterine infusion on the endometrium in endometriosis patients undergoing IVF/ICSI-treatment has not been investigated yet.

STUDY DESIGN SIZE DURATION

We performed a multicentre, patient-blinded, randomised controlled trial in which women were randomly allocated to either a Gel Infusion Sonography (GIS, intervention group) or a sham procedure (control group) prior to IVF/ICSI-treatment. Since recruitment was slow and completion of the study was considered unfeasible, the study was halted after inclusion of 112 of the planned 184 women.

PARTICIPANTS/MATERIALS SETTING METHODS

We included infertile women with surgically confirmed endometriosis ASRM stage I-IV undergoing IVF/ICSI-treatment. After informed consent, women were randomised to GIS with intrauterine instillation of ExEm-gel^® or sonography with gel into the vagina (sham). This was performed in the cycle preceding the embryo transfer, on the day GnRH analogue treatment was started. The primary endpoint was live birth rate after fresh embryo transfer. Analysis was performed by both intention-to-treat and per-protocol.

MAIN RESULTS AND THE ROLE OF CHANCE

Between July 2014 to September 2018, we randomly allocated 112 women to GIS (n = 60) or sham procedure (n = 52). The live birth rate after fresh embryo transfer was 16/60 (26.7%) after GIS versus 8/52 (15.4%) after the sham (RR 1.73, 95% CI 0.81-3.72; P-value 0.147). Ongoing pregnancy rate was 16/60 (26.7%) after GIS versus 9/52 (17.3%) in the controls (RR 1.54, 95% CI 0.74-3.18). Miscarriage occurred in 1/60 (1.7%) after GIS versus 5/52 (9.6%) in the controls (RR 0.17, 95% CI 0.02-1.44) women. Uterine bathing resulted in a higher pain score compared with a sham procedure (visual analogue scale score 2.7 [1.3-3.5] vs. 1.0 [0.0-2.0], P < 0.001). There were two adverse events after GIS compared with none after sham procedures.

LIMITATIONS REASONS FOR CAUTION

The study was terminated prematurely due to slow recruitment and trial fatigue. Therefore, the trial is underpowered to draw definite conclusions regarding the effect of uterine bathing with sonography gel on live birth rate after fresh embryo transfer in endometriosis patients undergoing IVF/ICSI-treatment.

WIDER IMPLICATIONS OF THE FINDINGS

We could not demonstrate a favourable effect of uterine bathing procedures with sonography gel prior to IVF/ICSI-treatment in patients with endometriosis.

STUDY FUNDING/COMPETING INTERESTS

Investigator initiated study. IQ Medical Ventures provided the ExEm FOAM^® kits free of charge, they were not involved in the study design, data management, statistical analyses and/or manuscript preparation, etc. C.B.L. reports receiving grants from Ferring, Merck and Guerbet, outside the submitted work. C.B.L. is Editor-in-Chief of Human Reproduction. V.M. reports grants and other from Guerbet, outside the submitted work. B.W.M. reports grants from NHMRC (GNT1176437), personal fees from ObsEva, Merck and Merck KGaA, Guerbet and iGenomix, outside the submitted work. N.P.J. reports research funding from Abb-Vie and Myovant Sciences and consultancy for Vifor Pharma, Guerbet, Myovant Sciences and Roche Diagnostics, outside the submitted work. K.D. reports personal fees from Guerbet, outside the submitted work. The other authors do not report any conflicts of interest. No financial support was provided.

TRIAL REGISTRATION NUMBER

NL4025 (NTR4198).

TRIAL REGISTRATION DATE

7 October 2013.

DATE OF FIRST PATIENT’S ENROLMENT

22 July 2014.

IVF, from the past to the future: the inheritance of the Capri Workshop Group

Today IVF use is booming all over the world and has even started to play a role in demographic analyses. Prognosis-adjusted estimates suggest that up to two-thirds of couples could achieve a live birth. However, the scenario is less exciting in reality. Discontinuation during the cycles is common, and age and ovarian response continue to be crucial in modulating this rate of success. A growing interest is now given to the risk of abuses and in particular to overtreatment and to prescriptions of useless, if not harmful, expensive additional treatments (‘add-ons’). A more rational, evidence-based and wise approach is needed. From a scientific perspective, several obscure aspects remain and warrant future investigations. Of particular interest are the neglected role of sperm selection, the potential adult implications of early embryo life in vitro and the issue of sustainability.

Effects of Testosterone on the Expression of Connexin 26 and Connexin 43 in the Uterus of Rats During Early Pregnancy

BACKGROUND/AIM

It was hypothesized that testosterone could affect the distribution and expression of connexin 26 and connexin 43 in the uterus. Thus, the effects of testosterone on these parameters in the uterus during the uterine receptivity period were investigated.

MATERIALS AND METHODS

Intact pregnant rats were administered 1 mg/kg/day testosterone alone or in combination with flutamide, finasteride or anastrozole, subcutaneously on day-1 of pregnancy till day 3. The rats were sacrificed at day 4 of pregnancy, which was considered as the uterine receptivity period for determining the expression and distribution of connexin 26 and connexion 43 by immunohistochemistry and quantitative polymerase chain reaction, respectively.

RESULTS

Treatment with 1 mg/kg/day testosterone increased connexin 26 and decreased connexin 43 mRNA expression and protein distribution in the uterus of early pregnancy rats.

CONCLUSION

Changes in the uterine connexin 26 and connexin 43 expression by testosterone could disrupt embryo implantation, resulting in early pregnancy loss.

Endometrial scratch injury with office hysteroscopy before IVF/ICSI: A randomised controlled trial

OBJECTIVE

Endometrial scratch injury (ESI) has been proposed to improve endometrial receptivity and thereby increase implantation rates in assisted reproductive technology (ART) treatment. ESI has been widely incorporated into clinical practice despite inconclusive evidence of its effect on reproductive outcomes. We aimed to assess pregnancy and live birth rates in subfertile women receiving ESI before IVF treatment in comparison to controls.

STUDY DESIGN

This was a randomised controlled trial (RCT) with no blinding of participants, investigators or health care personnel. Women in ART treatment were allocated to either office hysteroscopy with ESI (ESI group) or no intervention (control group). In total 184 women in IVF/ICSI treatment with minimum one previous failed IVF/ICSI cycle, were included in the final analysis. The primary outcome was positive serum hCG (s-hCG). Secondary outcomes were ongoing pregnancy and live birth rate. Only per-protocol analyses were performed as all patients included at one centre had to be excluded. The trial is registered at ClinicalTrials.gov, NCT01743391.

RESULTS

Our results showed a non-significant increase in positive s-hCG (OR 1.23, 95 % CI (0.65-2.33)), ongoing pregnancy (OR 1.52, 95 % CI (0.73-3.17)), and live birth rates (OR 1.69, 95 % CI (0.78-3.64)) per randomised woman between the ESI and the control group.

CONCLUSION

We observed no significant differences in positive s-hCG or other reproductive outcomes in the ESI vs. the control group. While the crude estimates of positive reproductive outcomes were higher in the ESI group, statistical significance was not reached, and the study was not powered to show smaller differences. However, data from this study will be re-evaluated in the context of an individual participant data meta-analysis (IPD-MA) of RCTs on ESI.

Randomised controlled trials evaluating endometrial scratching: assessment of methodological issues

STUDY QUESTION

Do randomised controlled trials (RCTs) evaluating endometrial scratching suffer from methodological issues including insufficient trial registration, statistical errors or irreproducibility, randomisation errors or miscellaneous issues?

SUMMARY ANSWER

The majority of RCTs investigating endometrial scratching have methodological issues.

WHAT IS KNOWN ALREADY

A large number of small RCTs investigating the effectiveness of endometrial scratching prior to in vitro fertilisation (IVF) and intrauterine insemination (IUI)/intercourse have reported favourable findings. Subsequently, systematic reviews incorporating these RCTs yielded meta-analyses in favour of endometrial scratching. Endometrial scratching has been widely adopted by infertility specialists around the world. Recently, an international RCT including 1364 women reported no benefit from endometrial scratching before IVF.

STUDY DESIGN, SIZE, DURATION

We evaluated several methodological issues of RCTs investigating the effectiveness of endometrial scratching prior to IVF and IUI/intercourse. We identified 25 RCTs for IVF and 12 RCTs for IUI/intercourse with full-text publication.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We assessed the RCTs on the following criteria: adequacy of trial registration, statistical issues (description of statistical methods and reproducibility of univariable statistical analysis), excessive similarity or difference in baseline characteristics that is not compatible with chance (Monte Carlo simulations and Kolmogorov–Smirnov test) and miscellaneous methodological issues.

MAIN RESULTS AND THE ROLE OF CHANCE

Of 25 RCTs evaluating endometrial scratching prior to IVF, only eight (32%) had adequate trial registration. In total, 10 (40%) RCTs had issues regarding statistical methods. Nine (69%, 13 applicable) RCTs had at least one inconsistency between reported and reproduced univariable statistical analysis for categorical baseline/intermediate characteristics. Statistical results of at least one outcome were not reproducible in 14 (74%, 19 applicable) RCTs. Only two (8%) RCTs had none of the above issues. Suggested by the simulations, these RCTs did not significantly violate the null hypothesis that the baseline characteristics were the results of a properly conducted randomisation process (P = 0.4395).

Of 12 IUI/intercourse RCTs, only 2 (17%) had adequate trial registration. In total, five (42%) studies had issues of statistical methods. Inconsistency between reported and reproduced univariable analysis for baseline/intermediate categorical variable(s) was found in four (57%, 7 applicable) RCTs. Statistical analysis was not reproducible for at least one outcome in eight (80%, 10 applicable) studies. All RCTs had at least one of the above issues. These RCTs were inconsistent with the null hypothesis that their baseline characteristics were the results of proper randomised allocation (P = 1.659*10−7).

LIMITATIONS, REASONS FOR CAUTION

We were unable to assess RCTs which were not published as full-text papers. We could not analyse individual participant data to investigate possible reasons for statistical inconsistencies. The method to infer the likelihood of proper random sampling rests on assumptions including independent baseline characteristics, simple randomisation and no publication bias.

WIDER IMPLICATIONS OF THE FINDINGS

The methodological issues common to RCTs evaluating endometrial scratching may have biased the results of the trials. Further development and validation of these novel methods may be helpful for the critical appraisal of RCTs.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was sought to support this work. B.W.M. is supported by a National Health Medical Research Council (NHMRC) Practitioner Fellowship (GNT1082548). B.W.M. reports consultancy for ObsEva, Merck and Guerbet. D.W. is supported by a grant from the Paracelsus Medical University Salzburg, Austria (PMU Research Fund—PMU FFF Number: L-18/02/006-WET) and by Drs Haackert Foundation, Germany. S.L. is an author of a trial included in this study, an author of an included systematic review and a Cochrane editor. All other authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A

Endometrial scratching prior to IVF; does it help and for whom? A systematic review and meta-analysis

STUDY QUESTION

What is the effect of endometrial scratching in patients with or without prior failed ART cycles on live birth (LBR) and clinical pregnancy rates (CPR)?

SUMMARY ANSWER

It remains unclear if endometrial scratching improves the chance of pregnancy and, if so, for whom.

WHAT IS KNOWN ALREADY

Endometrial scratching is hypothesized to improve embryo implantation in ART. Multiple studies have been published, but it remains unclear if endometrial scratching actually improves pregnancy rates and, if so, for which patients.

STUDY DESIGN, SIZE, DURATION

For this review, a systematic search for published articles on endometrial scratching and ART was performed on 12 February 2018, in Pubmed, Embase and the Cochrane Library.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Randomized controlled trials (RCTs) that evaluated endometrial scratching in the cycle prior to the stimulation cycle and reported CPR or LBR were included. RCTs investigating the effect of scratching during the stimulation cycle, or prior to cryo-thaw cycles were excluded. Studies were assessed using the Cochrane Risk of Bias tool. The effect of scratching was assessed for three different patient groups: patients with no prior IVF/ICSI treatment (Group 0), patients with one failed full IVF/ICSI cycle, including cryo-thaw cycles (Group 1) and patients with two or more failed full IVF/ICSI cycles (Group 2). A meta-analysis was performed when statistical heterogeneity was low; otherwise, a descriptive analysis was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

Fourteen RCTs involving 2537 participants were included. Most RCTs contained a high or unclear risk of bias on one or more items. Substantial clinical and statistical heterogeneity was present; therefore meta-analysis for LBR and CPR could only be performed on Group 1. For this group, no differences between scratch and control were found for both LBR (risk ratio (RR) 1.01 [95%CI 0.68–1.51]) and CPR (RR 1.04 [95%CI 0.74–1.45]). For Groups 0 and 2, pooled analysis could not be performed, and for both groups the results of the individual RCTs were negative, neutral and positive. Miscarriage and multiple pregnancy rates were evaluated for the three groups (0, 1 and 2) together. Both outcomes were not significantly different between scratch and control (miscarriage rate RR 0.82 [95%CI 0.57–1.17] and multiple pregnancy rate RR 1.06 [95%CI 0.84–1.35]). Subgroup analysis, excluding trials with a risk of unintentional endometrial injury in the control group, was performed for Group 0 and 2 for LBR and CPR, and for the overall groups for miscarriage rate and multiple pregnancy rate. This reduced the heterogeneity and allowed for pooled analysis in these subgroups. Results of pooled analysis for the subgroups of Group 0 and 2 showed no significant difference for LBR, but CPR was significantly improved after endometrial scratching (Group 0 RR 1.28 [95%CI 1.02–1.62] and Group 2 RR 2.03 [95%CI 1.20–3.43]). Subgroup analysis of the overall groups showed no significant difference for miscarriage and multiple pregnancy rate.

LIMITATIONS REASONS FOR CAUTION

The main limitations were that many RCTs had a high or unclear risk of bias on one or several items, clinical heterogeneity was still present despite categorizing into three populations, and that not all RCTs could be included in the analyses because separate data for our three groups could not be provided.

WIDER IMPLICATIONS OF THE FINDINGS

It remains unclear if endometrial scratching improves the chance of pregnancy for women undergoing ART and, if so, for whom. This means endometrial scratching should not be offered in daily practice until results from large and well-designed RCTs and an individual patient data analysis become available.

STUDY FUNDING/COMPETING INTERESTS

No specific funding was sought for the study. The Department of Reproductive Medicine and Gynaecology funds of the University Medical Center of Utrecht were used to support the authors throughout the study period and preparation of the manuscript. None of the authors has a conflict of interest to declare.

REGISTRATION NUMBER

Not applicable.

Direct Cell⁻Cell Interactions in the Endometrium and in Endometrial Pathophysiology

Cell contacts exhibit a considerable influence on tissue physiology and homeostasis by controlling paracellular and intercellular transport processes, as well as by affecting signaling pathways. Since they maintain cell polarity, they play an important role in cell plasticity. The knowledge about the junctional protein families and their interactions has increased considerably during recent years. In contrast to most other tissues, the endometrium undergoes extensive physiological changes and reveals an extraordinary plasticity due to its crucial role in the establishment and maintenance of pregnancy. These complex changes are accompanied by changes in direct cell–cell contacts to meet the various requirements in the respective developmental stage. Impairment of this sophisticated differentiation process may lead to failure of implantation and embryo development and may be involved in the pathogenesis of endometrial diseases. In this article, we focus on the knowledge about the distribution and regulation of the different junctional proteins in the endometrium during cycling and pregnancy, as well as in pathologic conditions such as endometriosis and cancer. Decoding these sophisticated interactions should improve our understanding of endometrial physiology as well as of the mechanisms involved in pathological conditions.

Physiological and pathological implications of retinoid action in the endometrium

Retinol (vitamin A) and its derivatives, collectively known as retinoids, are required for maintaining vision, immunity, barrier function, reproduction, embryogenesis and cell proliferation and differentiation. Despite the fact that most events in the endometrium are predominantly regulated by steroid hormones (estrogens and progesterone), accumulating evidence shows that retinoid signaling is also involved in the development and maintenance of the endometrium, stromal decidualization and blastocyst implantation. Moreover, aberrant retinoid metabolism seems to be a critical factor in the development of endometriosis, a common gynecological disease, which affects up to 10% of reproductive age women and is characterized by the ectopic localization of endometrial-like tissue in the pelvic cavity. This review summarizes recent advances in research on the mechanisms and molecular actions of retinoids in normal endometrial development and physiological function. The potential roles of abnormal retinoid signaling in endometriosis are also discussed. The objectives are to identify limitations in current knowledge regarding the molecular actions of retinoids in endometrial biology and to stimulate new investigations toward the development potential therapeutics to ameliorate or prevent endometriosis symptoms.

Gap junctional connexin messenger RNA expression in the ovine uterus and placenta: effects of estradiol-17β-treatment, early pregnancy stages, and embryo origin

Gap junctions play a major role in direct, contact-dependent cell-cell communication, and they have been implicated in the regulation of cellular metabolism and the coordination of cellular functions during growth and differentiation of organs and tissues. Gap junctional channels, composed of connexin (Cx) proteins, have been detected and shown to be influenced by hormones (eg, estrogen and progesterone) in uterine and placental tissues in several species. We hypothesized that (1) the messenger RNA (mRNA) for Cx26, Cx32, Cx37, and Cx43 is expressed in the uterus of ovariectomized sheep treated with estradiol-17β (E2) and in ovine placenta during early pregnancy, (2) E2-treatment of ovariectomized ewes would cause time-specific changes in Cx26, Cx32, Cx37, and Cx43 mRNA expression (experiment 1), and (3) expression of these 4 Cx would vary across the days of early pregnancy (experiment 2) and will be affected by embryo origin (ie, after application of assisted reproductive technologies [ARTs]; experiment 3). Thus, we collected uterine tissues at 0 to 24 h after E2 treatments (experiment 1), and placental tissues during days 14 to 30 of early pregnancy after natural (NAT) breeding (experiment 2) and on day 22 of early pregnancy established after transfer of embryos generated through natural breeding (NAT-ET), in vitro fertilization (IVF), or in vitro activation (IVA, parthenotes; experiment 3). In experiment 1, the expression of Cx26, Cx37, and Cx43 mRNA increased (P < 0.05) and Cx32 mRNA decreased (P < 0.06) in both caruncular and intercaruncular tissues after E2 treatment. In experiment 2, during early pregnancy, there were significant changes (P < 0.01) across days in the expression of Cx26, Cx37, and Cx43 mRNA in the maternal placenta, accompanied by changes (P < 0.001) in Cx37 and Cx43 mRNA in the fetal placenta. In experiment 3, in maternal placenta, Cx32 mRNA expression was decreased (P < 0.001) in NAT-ET, IVF, and IVA groups compared to the NAT group; but in fetal placenta, Cx32 mRNA expression was increased (P < 0.05) in NAT-ET, IVF and IVF groups, and Cx26 mRNA expression was increased (P < 0.05) in IVA compared to NAT group. These data suggest that Cx26, Cx32, Cx37, and Cx43 play specific roles in E2-regulated uterine function and in placental development during early gestation both after natural mating and with application of ART.

Pipelle for Pregnancy (PIP): study protocols for three randomised controlled trials

Background

The success rate of infertility treatments remains modest. Endometrial injury has been suggested as an intervention to increase the probability of pregnancy in women undergoing assisted reproductive technologies such as in vitro fertilisation (IVF). The majority of studies and systematic reviews have reported that endometrial injury improves the outcomes of IVF, intrauterine insemination and natural conception; however, the size and quality of the studies are poor. The low quality of the available evidence questions the presence of any real beneficial effect, and the applicability of the intervention in different populations remains unclear.

Methods/design

The PIP trials are three multi-centre, randomised controlled trials designed to test three separate hypotheses: whether endometrial injury increases the probability of live birth in women or couples

1) who are undergoing autologous embryo transfer as part of an IVF cycle (PIP-IVF),

2) with unexplained infertility who are attempting to conceive naturally (PIP-UE) and

3) with subfertility related to polycystic ovarian syndrome (PCOS) who are on ovulation induction medication and attempting to conceive (PIP-PCOS).

Participants will be randomised to either undergo endometrial injury by endometrial pipelle biopsy or to:

• no intervention (PIP-IVF), or

• a sham procedure (PIP-PCOS and PIP-UE).

In PIP-IVF, endometrial injury will be carried out between day three of the cycle prior to the IVF cycle, and day three of the IVF cycle. In PIP-UE and PIP-PCOS, endometrial injury or a sham procedure will be undertaken between days 1–12 of a menstrual cycle or ovulation induction cycle respectively. Participants in PIP-UE and PIP-PCOS will then be followed for three cycles during which time they will attempt to conceive from sexual intercourse. To ensure allocation concealment, randomisation will be carried out using a web-based system or sequentially numbered, opaque, sealed envelopes. The primary outcome is live birth. Secondary outcomes include ongoing pregnancy, clinical pregnancy and miscarriage.

The required sample sizes for the PIP studies have been estimated at 840 (PIP-IVF), 350 (PIP-UE) and 280 (PIP-PCOS). Primary analysis will be as per intention-to-treat principles.

Discussion

The PIP trials are designed to address the gaps in the utility of endometrial scratching as a treatment for subfertility in three different populations. If the beneficial effect of this intervention can be confirmed in these settings, endometrial scratching will provide a cost-effective method for helping women and couples to conceive.

Trial registrations

PIP-IVF ACTRN12614000626662 registered 13/6/2014; PIP-PCOS ACTRN12614000657628 registered 24/6/2014; PIP-UE ACTRN12614000656639 registered 24/6/2014. The trials are ongoing.

The endocrine dyscrasia that accompanies menopause and andropause induces aberrant cell cycle signaling that triggers re-entry of post-mitotic neurons into the cell cycle, neurodysfunction, neurodegeneration and cognitive disease

This article is part of a Special Issue "SBN 2014". Sex hormones are physiological factors that promote neurogenesis during embryonic and fetal development. During childhood and adulthood these hormones support the maintenance of brain structure and function via neurogenesis and the formation of dendritic spines, axons and synapses required for the capture, processing and retrieval of information (memories). Not surprisingly, changes in these reproductive hormones that occur with menopause and during andropause are strongly correlated with neurodegeneration and cognitive decline. In this connection, much evidence now indicates that Alzheimer's disease (AD) involves aberrant re-entry of post-mitotic neurons into the cell cycle. Cell cycle abnormalities appear very early in the disease, prior to the appearance of plaques and tangles, and explain the biochemical, neuropathological and cognitive changes observed with disease progression. Intriguingly, a recent animal study has demonstrated that induction of adult neurogenesis results in the loss of previously encoded memories while decreasing neurogenesis after memory formation during infancy mitigated forgetting. Here we review the biochemical, epidemiological and clinical evidence that alterations in sex hormone signaling associated with menopause and andropause drive the aberrant re-entry of post-mitotic neurons into an abortive cell cycle that leads to neurite retraction, neuron dysfunction and neuron death. When the reproductive axis is in balance, gonadotropins such as luteinizing hormone (LH), and its fetal homolog, human chorionic gonadotropin (hCG), promote pluripotent human and totipotent murine embryonic stem cell and neuron proliferation. However, strong evidence supports menopausal/andropausal elevations in the LH:sex steroid ratio as driving aberrant mitotic events. These include the upregulation of tumor necrosis factor; amyloid-β precursor protein processing towards the production of mitogenic Aβ; and the activation of Cdk5, a key regulator of cell cycle progression and tau phosphorylation (a cardinal feature of both neurogenesis and neurodegeneration). Cognitive and biochemical studies confirm the negative consequences of a high LH:sex steroid ratio on dendritic spine density and human cognitive performance. Prospective epidemiological and clinical evidence in humans supports the premise that rebalancing the ratio of circulating gonadotropins:sex steroids reduces the incidence of AD. Together, these data support endocrine dyscrasia and the subsequent loss of cell cycle control as an important etiological event in the development of neurodegenerative diseases including AD, stroke and Parkinson's disease.

Endometrial disruption does not improve implantation in patients who have failed the transfer of euploid blastocysts

Purpose

To assess the impact of single pass outpatient endometrial biopsy in patients at the highest risk for an endometrial cause for failed implantation; those that have failed to conceive despite the transfer of morphologically normal euploid embryos.

Methods

This is a retrospective cohort study consisting of all patients less than 42 years old who failed their first euploid blastocyst transfer and subsequently completed a second transfer cycle of euploid blastocysts. Cycles were analyzed to determine if a single pass endometrial biopsy, termed 'endometrial disruption', was performed in a cycle preceding their second embryo transfer. Transfer outcomes were analyzed and implantation rates calculated. Data analysis was performed to compare outcomes between patients who had endometrial disruption performed versus those that did not.

Results

Two hundred ninety patients failed their first euploid embryo transfer and subsequently completed a second euploid embryo transfer and were included. Thirty-nine patients underwent endometrial disruption and 251 did not. There were no statistical differences in clinical implantation rate or sustained implantation rate between the group with endometrial disruption and subjects without any intervention (Clinical IR, 43.6 % vs. 55.0 %, p = 0.13; 38.5 % vs. 42.6 %, p = 0.60). When controlling for transfer order there was no statistical difference noted in implantation rates.

Conclusions

Single pass endometrial biopsy has no impact on endometrial receptivity in the highest risk subgroup- patient's that have failed to sustain the transfer of morphologically normal euploid embryos- as evidenced by equivalent implantation rates. It is possible that variations in technique may alter outcomes and randomized trials are needed to answer this question.

Local effects of pregnancy on connexin proteins that mediate Ca2+-associated uterine endothelial NO synthesis

Uterine artery adaptations during gestation facilitate increases in uterine blood flow and fetal growth.

HYPOTHESIS

local expression and distribution of uterine artery connexins play roles in mediating in vivo gestational eNOS activation and NO production. We established an ovine model restricting pregnancy to a single uterine horn and measured uterine blood flow, uterine artery shear stress, connexins 37/43, and P(635)eNOS protein levels in uterine artery and systemic artery (omental and renal) endothelium and connexins in vascular smooth muscle. Uterine blood flow and shear stress were locally (unilaterally) and substantially elevated by gestation. During pregnancy, uterine artery endothelial gap junction proteins connexins 37/43 were locally regulated in the gravid horn and elevated 10.3- and 25.6-fold; uterine artery endothelial P(635)eNOS and total eNOS were elevated 3.3- and 2.9-fold; whereas uterine artery vascular smooth muscle connexins 37/43 were locally elevated 12.5- and 5.9-fold, respectively. Less pronounced changes were observed in systemic vasculature except for significant pregnancy-associated increases in omental artery vascular smooth muscle connexin 43 and omental artery endothelial P(635)eNOS and total eNOS. Gap junction blockade using connexin 43, but not connexin 37-specific Gap peptides, abrogated uterine artery endothelial ATP-induced Ca(2+)-mediated NO production. Thus, uterine artery endothelial connexin 43, but not connexin 37, regulates Ca(2+)-mediated NO production required for the vasodilation to accommodate increases in uterine blood flow and shear stress during healthy pregnancies.

Reduced connexin 43 in eutopic endometrium and cultured endometrial stromal cells from subjects with endometriosis

Accumulating evidence indicates that reduced fecundity associated with endometriosis reflects a failure of embryonic receptivity. Microdomains composed of endometrial gap junctions, which facilitate cell-cell communication, may be implicated. Pharmacological or genetic inhibition of connexin (Cx) 43 block human endometrial cell differentiation in vitro and conditional uterine deletion of Cx43 alleles cause implantation failure in mice. The aim of this study was to determine whether women with endometriosis have reduced eutopic endometrial Cx43. Cx26 acted as a control. Endometrial biopsies were collected from age, race and cycle phase-matched women without (15 controls) or with histologically confirmed endometriosis (15 cases). Immunohistochemistry confirmed a predominant localization of Cx43 in the endometrial stroma, whereas Cx26 was confined to the epithelium. Cx43 immunostaining was reduced in eutopic biopsies of endometriosis subjects and western blotting of tissue lysates confirmed lower Cx43 levels in endometriosis cases, with Cx43/β-actin ratios=.4±1.5 in control and =1.2±0.3 in endometriosis biopsies (P<0.01). When endometrial stromal cells (ESC) were isolated from endometriosis cases, Cx43 levels and scrape loading-dye transfer were reduced by ∼45% compared with ESC from controls. In vitro decidualization of ESC derived from endometriosis versus control subjects resulted in lesser epithelioid transformation and a significantly reduced up-regulation of Cx43 protein (1.2±0.2- versus 1.7±0.4-fold, P<0.01). No changes in Cx26 were observed. While basal steady-state levels of Cx43 mRNA did not differ with respect to controls, ESC from endometriosis cases failed to manifest a response to hormone treatment in vitro. In summary, eutopic endometrial Cx43 concentrations in endometriosis cases were <50% those of controls in vivo and in vitro, functional gap junctions were reduced and hormone-induced Cx43 mRNA levels were blunted.

Disruption of gap junctions reduces biomarkers of decidualization and angiogenesis and increases inflammatory mediators in human endometrial stromal cell cultures

CONTEXT

Uterine decidualization is critical to embryonic implantation and sustained pregnancy.

OBJECTIVE

To evaluate the role of gap junction intercellular communications and connexin (Cx) proteins in the morphological and biochemical differentiation of decidualized human endometrial stromal cell (ESC) cultures.

DESIGN

Translational cell biological study.

SETTING

Academic medical center.

PATIENTS

Endometrial tissue was provided by five healthy reproductive age women on no hormonal medication, undergoing laparoscopy in the early proliferative phase of the menstrual cycle.

INTERVENTIONS

Endometrial biopsy under general anesthesia, establishment and decidualization of ESC with 10 nM 17β-estradiol, 100 nM progesterone and 0.5 mM dibutyryl-cAMP (E/P/c), and manipulation of gap junctions in vitro via a combination of pharmacological or transgenic approaches.

MAIN OUTCOME MEASURES

Decidualized ESC evaluated morphologically for epithelioid transformation, gap junctions by dye diffusion and Cx43, prolactin, VEGF and IL-6 expression by RT-PCR, Western and ELISA methods.

RESULTS

Cx43 accumulation and functional gap junctions between decidualized ESC increase concomitantly with morphological differentiation following E/P/c treatment. Disruption of gap junctions using pharmacological inhibitors or Cx43 shRNA prevents morphological differentiation and inhibits prolactin and VEGF secretion. By contrast, IL-6 secretion from decidualized ESC is augmented by both approaches.

CONCLUSIONS

The findings suggest that decidualized ESC function as a coordinated secretory organ to regulate embryonic implantation via intercellular cooperation mediated by gap junctions. When adjacent cells can communicate through these junctions, decidual prolactin and VEGF secretion appears to be optimized for vascular development of the placental bed. Conversely, when intercellular communications are disrupted, angiogenesis is impaired and an inflammatory state is induced.

Bovine pretransfer endometrium and embryo transcriptome fingerprints as predictors of pregnancy success after embryo transfer

Aberrant gene expression in the uterine endometrium and embryo has been the major causes of pregnancy failure in cattle. However, selecting cows having adequate endometrial receptivity and embryos of better developmental competence based on the gene expression pattern has been a greater challenge. To investigate whether pretransfer endometrial and embryo gene expression pattern has a direct relation with upcoming pregnancy success, we performed a global endometrial and embryo transcriptome analysis using endometrial and embryo biopsy technology and the pregnancy outcome information. For this, endometrial samples were collected from Simmental heifers at day 7 and 14 of the estrous cycle, one cycle prior to embryo transfer. In the next cycle, blastocyst stage embryos were transferred to recipients at day 7 of the estrous cycle after taking 30-40% of the blastocyst as a biopsy for transcriptome analysis. The results revealed that at day 7 of the estrous cycle, the endometrial gene expression pattern of heifers whose pregnancy resulting in calf delivery was significantly different compared with those resulting in no pregnancy. These differences were accompanied by qualitative and quantitative alteration of major biological process and molecular pathways. However, the transcriptome difference was minimal between the two groups of animals at day 14 of the estrous cycle. Similarly, the transcriptome analysis between embryos biopsies that resulted in calf delivery and those resulted in no pregnancy revealed a total of 70 differentially expressed genes. Among these, the transcript levels of 32 genes including SPAG17, PF6, UBE2D3P, DFNB31, AMD1, DTNBP1, and ARL8B were higher in embryo biopsies resulting in calf delivery. Therefore, the present study highlights the potential of pretransfer endometrial and embryo gene expression patterns as predictors of pregnancy success in cattle.

Connexin expression pattern in the endometrium of baboons is influenced by hormonal changes and the presence of endometriotic lesions

Experimentally induced endometriosis in baboons serves as an elegant model to discriminate between endometrial genes which are primarily associated with normal endometrial function and those that are changed by the presence of endometriotic lesions. Since connexin genes are characteristic of the hormonally regulated differentiation of the endometrium, we have examined connexin expression in baboon endometrium to delineate if they are altered in response to the presence of endometriotic lesions. Connexin expression in the endometrium of cycling baboons is similar to that of the human endometrium with Connexin(Cx)43 being primarily seen in the stromal compartment and Cx26 and Cx32 being present predominantly in the epithelium. Although Cx32 is up-regulated during the secretory phase, Cx26 and Cx43 are down-regulated. In the baboon model of induced endometriosis a change in connexin pattern was evident in the presence of endometriotic lesions. In the secretory phase, Cx26 and Cx32 are no longer present in the epithelium but Cx26 is now observed primarily in the stromal cells. Infusion of chorionic gonadotrophin in a manner that mimics blastocyst transit in utero failed to rescue the aberrant stromal expression of Cx26 that is associated with the presence of endometriotic lesions suggesting an impairment of the implantation process. The altered connexin pattern coupled with a loss of the channel protein in the epithelium and a gain of Cx26 in the stromal compartment suggests that the presence of lesions changes the uterine environment and thereby the differentiation programme. This aberrant expression of connexins may be an additional factor that contributes to endometriosis-associated infertility.

Gap junction communication between uterine stromal cells plays a critical role in pregnancy-associated neovascularization and embryo survival

In the uterus, the formation of new maternal blood vessels in the stromal compartment at the time of embryonic implantation is critical for the establishment and maintenance of pregnancy. Although uterine angiogenesis is known to be influenced by the steroid hormones estrogen (E) and progesterone (P), the underlying molecular pathways remain poorly understood. Here, we report that the expression of connexin 43 (Cx43), a major gap junction protein, is markedly enhanced in response to E in uterine stromal cells surrounding the implanted embryo during the early phases of pregnancy. Conditional deletion of the Cx43 gene in these stromal cells and the consequent disruption of their gap junctions led to a striking impairment in the development of new blood vessels within the stromal compartment, resulting in the arrest of embryo growth and early pregnancy loss. Further analysis of this phenotypical defect revealed that loss of Cx43 expression resulted in aberrant differentiation of uterine stromal cells and impaired production of several key angiogenic factors, including the vascular endothelial growth factor (Vegf). Ablation of CX43 expression in human endometrial stromal cells in vitro led to similar findings. Collectively, these results uncovered a unique link between steroid hormone-regulated cell-cell communication within the pregnant uterus and the development of an elaborate vascular network that supports embryonic growth. Our study presents the first evidence that Cx43-type gap junctions play a critical and conserved role in modulating stromal differentiation, and regulate the consequent production of crucial paracrine signals that control uterine neovascularization during implantation.

Endometrial biopsy-induced gene modulation: first evidence for the expression of bladder-transmembranal uroplakin Ib in human endometrium

OBJECTIVE

To explore the possibility that endometrial injury modulates the expression of specific genes that may increase uterine receptivity.

DESIGN

Controlled clinical study.

SETTING

Clinical IVF unit and academic research center.

PATIENT(S)

IVF patients with 28- to 30-day menstrual cycles.

INTERVENTION(S)

Endometrial biopsies from two groups of patients were collected on days 20-21 of their spontaneous menstrual cycle. The experimental, but not the control, group underwent biopsies on days 11-13 and 21-24 of their preceding cycle.

MAIN OUTCOME MEASURE(S)

Global endometrial gene expression and specific analysis of uroplakin Ib (UPIb) mRNA level throughout the menstrual cycle.

RESULT(S)

Local injury modulated the expression of a wide variety of genes. One of the prominently up-regulated genes was the bladder transmembranal protein, UPIb, whose expression by the endometrium is shown here for the first time. Endometrial UPIb mRNA increases after biopsy in the same cycle wct 2with an additional elevation in the following cycle. Immunohistochemical analysis localized the UPIb protein to the glandular-epithelial cells. Genes encoding other membrane proteins such as adipose differentiation-related protein and mucin 1, transmembrane, were also up-regulated.

CONCLUSION(S)

The biopsy-induced increase in the expression of UPIb and other genes encoding membrane proteins supports the possible importance of the membrane structure and stability during implantation. The specific role of UPIb in uterine receptivity should be elucidated.

Endometrial receptivity: Clinical assessment in relation to fertility, infertility, and antifertility

Fertility in humans and other mammalian species depends absolutely on synchronous events that render the developing blastocyst and the receiving uterus competent for implantation. Endometrial receptivity is defined as the period during which the endometrial epithelium acquires functional, but transient, ovarian steroid-dependent status supportive to blastocyst acceptance and implantation. Once inside the uterus, the blastocyst is surrounded by an intact luminal epithelium, which is considered to act as barrier to its attachment, except for this short period of high endometrial receptivity to blastocyst signal(s). Its transport and permeability properties, in conjunction with cellular action of the endometrium and the embryo, have been suggested to influence creation and maintenance of informational and nutritional status of uterine luminal milieu. This period, also termed as the 'window of implantation,' is limited to days 20-24 of menstrual cycle in humans. However, establishment of endometrial receptivity is still a biological mystery that remains unsolved despite marked advances in our understanding of endometrial physiology following extensive research associated with its development and function. This review deals with various structural, biochemical, and molecular events in the endometrium coordinated within the implantation window that constitute essential elements in the repertoire that signifies endometrial receptivity and is aimed to achieve a better understanding of its relationship to fertility, infertility, and for the development of targeted antifertility agents for human use and welfare.

Up-regulation of gap junctional intercellular communication and connexin43 expression by retinoic acid in human endometrial stromal cells

CONTEXT

Gap junctions, made up of connexins (Cxs), play fundamental roles in coordinating a number of cellular processes through their ability to directly regulate cell-cell communication. Cx43 is the most widely expressed Cx in the endometrium and is known to be important in a variety of physiological and pathological processes in this tissue.

OBJECTIVE

In this study, we investigated the ability of the retinoid, all-trans-retinoic acid (RA), to regulate Cx43 expression in human endometrial stromal cells.

DESIGN

Primary endometrial stromal cells obtained from patients undegoing surgery for infertility workup were treated in vitro with RA and control compounds for different time periods, up to 48 h. Cx43 mRNA and protein levels, protein phosphorylation, and gap junctional intercellular communication (GJIC) were analyzed.

RESULTS

Treatment of the cells with RA showed a dose-dependent increase in Cx43 expression at both the mRNA and protein levels. In addition, RA induced a relative decrease in the phosphorylated species of Cx43 while causing a corresponding increase in the nonphosphorylated form. Concomitant with these changes, RA-treated cells demonstrated up to a 250% enhancement of GJIC as assessed by dye transfer experiments. Augmentation of GJIC and alterations of Cx43 expression were observed over the same range of RA concentrations. Treatment of cells with the protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate increased the phosphorylated species of Cx43 and correspondingly inhibited GJIC.

CONCLUSIONS

Phosphorylation of Cx43 is inversely related to GJIC in endometrial stromal cells. Retinoids increase GJIC in endomentrial stromal cells through upregulation of Cx43 expression while inducing a decrease in the phosphorylated species of the protein. The data suggest a novel mechanism by which retinoids can influence endometrial cell biology.

Local injury to the endometrium doubles the incidence of successful pregnancies in patients undergoing in vitro fertilization

OBJECTIVE

Exploration of the possibility that local injury of the endometrium increases the incidence of implantation.

DESIGN

Prospective study.

SETTING

Clinical IVF unit.

PATIENT(S)

A group of 134 patients, defined as good responders to hormonal stimulation, who failed to conceive during one or more cycles of IVF and embryo transfer (ET).

INTERVENTION(S)

The IVF treatment and ET were preceded by repeated endometrial biopsies, in a randomly selected 45 of a total of 134 patients.

MAIN OUTCOME MEASURES

Outcome of IVF-ET treatments.

RESULT(S)

Transfer of a similar number of embryos (3.4 +/- 1.0 and 3.1 +/- 0.9 in the experimental and control patients, respectively) resulted in rates of implantation (27.7% vs. 14.2%, P =.00011), clinical pregnancy (66.7% vs. 30.3%, P =.00009), and live births per ET (48.9% vs. 22.5%, P =.016) that were more than twofold higher in the experimental group as compared to controls.

CONCLUSION(S)

These results suggest that IVF treatment that is preceded by endometrial biopsy doubles the chance for a take-home baby.

Oestrogen and progestin responses in human endometrium

Our understanding of the mechanisms of the actions of oestrogens and progestins have evolved from the simple concept of nuclear receptor-mediated regulation of transcription to a highly sophisticated, finely tuned interplay between various coregulators, other signaling cascades and transcription factors. The net result of these complex regulatory mechanisms is a steroid-, cell-, or tissue-specific action of oestrogens and progestins, their antagonists or selective modulators of their receptors. In this review, we have attempted to shed some light on the regulation of the actions of oestrogens and progestins on the human endometrium.