Decreased endometrial vascularity and receptivity in unexplained recurrent miscarriage patients during midluteal and early pregnancy phases

An investigation of endometrial vascularity in normally menstruating women and those in other physiological states using 3D ultrasound imaging

OBJECTIVES

This study aimed to determine the normal vasculature indices of the endometrium and to correlate them with those in various physiological states.

METHODS

Women undergoing ultrasound at the Feto-Maternal Center, Qatar in 2020-2021 as part of their gynecologic evaluation were enrolled into the study. They were divided into those with normal menses and no additional pathology, those following spontaneous miscarriage, postpartum and menopausal. Three-dimensional (3D) evaluation of the endometrial vasculature was done and the parameters quantified included vascularization index (VI), flow index (FI), vascularization flow index (VFI), endometrial thickness, endometrial volume and uterine volume. JASP, an open-source statistical analysis software, was used for analysis and an independent t-test to compare the vascularity indices. A multivariate regression analysis was also done to look at the factors affecting the endometrial vascular indices within the luteal phase.

RESULTS

A total of 461 women were studied: 122 in the follicular phase, 199 in the luteal phase, 90 after a spontaneous miscarriage, 29 postpartum, and 16 menopausal. The vascularity indices were highest after miscarriage and lowest postnatally. There were no significant effects of age, gravida, para, or abortions on VI and VFI. However, there was a significant positive effect of age on FI (P = 0.019) There was a significant increase in endometrial volume and thickness in the luteal phase as compared to follicular phase (P < 0.01), but there was no difference in the vascularity indices. The uterine and endometrial volume in the postnatal group were nearly double that of the luteal group (P value <0.01 and 0.014, respectively). There was a significant decrease in flow index in the postnatal group compared to the luteal group (P < 0.01), suggesting low flow intensity in the postnatal group.

CONCLUSIONS

Endometrial vascular indices measured using 3D Doppler can be used to determine normal vascular indices and vary with physiological states such as after miscarriages, postnatally and in the menopausal states.

Radiomics optimizing the evaluation of endometrial receptivity for women with unexplained recurrent pregnancy loss

Background

The optimization of endometrial receptivity (ER) through individualized therapies has been shown to enhance the likelihood of successful gestation. However, current practice lacks comprehensive methods for evaluating the ER of patients with recurrent pregnancy loss (RPL). Radiomics, an emerging AI-based technique that enables the extraction of mineable information from medical images, holds potential to offer a more objective and quantitative approach to ER assessment. This innovative tool may facilitate a deeper understanding of the endometrial environment and enable clinicians to optimize ER evaluation in RPL patients.

Objective

This study aimed to identify ultrasound radiomics features associated with ER, with the purpose of predicting successful ongoing pregnancies in RPL patients, and to assess the predictive accuracy of these features against regular ER parameters.

Methods

This retrospective, controlled study involved 262 patients with unexplained RPL and 273 controls with a history of uncomplicated full-term pregnancies. Radiomics features were extracted from ultrasound endometrial segmentation images to derive a radiomics score (rad-score) for each participant. Associations between rad-scores, baseline clinical variables, and sonographic data were evaluated using univariate and multivariate logistic regression analyses to identify potential indicators of RPL. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive accuracy of the rad-score and other identified indicators in discriminating RPL cases. Furthermore, the relationships between age and these identified indicators were assessed via Pearson correlation analysis.

Results

From the 1312 extracted radiomics features, five non-zero coefficient radiomics signatures were identified as significantly associated with RPL, forming the basis of the rad-score. Following multivariate logistic regression analysis, age, spiral artery pulsatility index (SA-PI), vascularisation index (VI), and rad-score emerged as independent correlates of RPL (all P<0.05). ROC curve analyses revealed the superior discriminative capability of the rad-score (AUC=0.882) over age (AUC=0.778), SA-PI (AUC=0.771), and VI (AUC=0.595). There were notable correlations between age and rad-score (r=0.275), VI (r=-0.224), and SA-PI (r=0.211), indicating age-related variations in RPL predictors.

Conclusion

This study revealed a significant association between unexplained RPL and elevated endometrial rad-scores during the WOI. Furthermore, it demonstrated the potential of rad-scores as a promising predictive tool for successful ongoing pregnancies in RPL patients.

Effect of autologous platelet-rich plasma for treatment of recurrent pregnancy loss: a randomized controlled trial

Objective

Recurrent pregnancy loss (RPL) is a fertility problem for which no exact mechanism of abortion or efficient treatment has been described. This study was conducted between 2018 and 2019 to investigate the effectiveness of autologous platelet-rich plasma (PRP) in improving the live birth rate of women with RPL who required in vitro fertilization (IVF).

Methods

A total of 63 patients with at least two previous pregnancy losses and no specific cause detected for the RPL were included and randomly assigned into two groups (PRP and control). Intrauterine infusion of 0.5 mL of autologous PRP was performed 48 hours before embryo transfer in the PRP group. Women in the control group received standard treatment.

Results

Forty patients completed the study. The baseline and cycle characteristics of the participants did not differ significantly between the PRP and control groups. The clinical pregnancy rate was higher in the PRP group (35% vs. 20%, P=0.288). The live birth rate was 15% in the PRP group, but no live births were recorded in the control group (P=0.231).

Conclusion

This is the first study to show that intrauterine infusion of PRP in patients with RPL who undergo IVF may increase the chance of live birth.

Synergistic regenerative therapy of thin endometrium by human placenta-derived mesenchymal stem cells encapsulated within hyaluronic acid hydrogels

Background

Thin endometrium is a primary cause of defective endometrial receptivity, resulting in infertility or recurrent miscarriage. Much effort has been devoted toward regenerating thin endometrium by stem cell-based therapies. The human placenta-derived mesenchymal stem cells (HP-MSCs) are emerging alternative sources of MSCs with various advantages. To maximize their retention inside the uterus, we loaded HP-MSCs with cross-linked hyaluronic acid hydrogel (HA hydrogel) to investigate their therapeutic efficacy and possible underlying mechanisms.

Methods

Ethanol was injected into the mice uterus to establish the endometrium-injured model. The retention time of HP-MSCs and HA hydrogel was detected by in vivo imaging, while the distribution of HP-MSCs was detected by immunofluorescence staining. Functional restoration of the uterus was assessed by testing embryo implantation rates. The endometrial morphological alteration was observed by H&E staining, Masson staining, and immunohistochemistry. In vitro studies were further conducted using EdU, transwell, tube formation, and western blot assays.

Results

Instilled HP-MSCs with HA hydrogel (HP-MSCs-HA) exhibited a prolonged retention time in mouse uteri than normal HP-MSCs. In vivo studies showed that the HP-MSCs-HA could significantly increase the gland number and endometrial thickness (P < 0.001, P < 0.05), decrease fibrous area (P < 0.0001), and promote the proliferation and angiogenesis of endometrial cells (as indicated by Ki67 and VEGF, P < 0.05, P < 0.05, respectively) in mice injured endometrium. HP-MSCs-HA could also significantly improve the embryo implantation rate (P < 0.01) compared with the ethanol group. Further mechanistic study showed the paracrine effects of HP-MSCs. They could not only promote the proliferation and migration of human endometrial stromal cells via the JNK/Erk1/2-Stat3-VEGF pathway but also facilitate the proliferation of glandular cells via Jak2-Stat5 and c-Fos-VEGF pathway. In turn, the increased VEGF in the endometrium promoted the angiogenesis of endothelial cells.

Conclusion

Our study suggested the potential therapeutic effects and the underlying mechanisms of HP-MSCs-HA on treating thin endometrium. HA hydrogel could be a preferable delivery method for HP-MSCs, and the strategy represents a promising therapeutic approach against endometrial injury in clinical settings.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02717-2.

Killer Timing: The Temporal Uterine Natural Killer Cell Differentiation Pathway and Implications for Female Reproductive Health

Natural killer (NK) cells are the predominant maternal uterine immune cell component, and they densely populate uterine mucosa to promote key changes in the post-ovulatory endometrium and in early pregnancy. It is broadly accepted that (a) immature, inactive endometrial NK (eNK) cells in the pre-ovulatory endometrium become activated and transition into decidual NK (dNK) cells in the secretory stage, peri-implantation endometrium, and continue to mature into early pregnancy; and (b) that secretory-stage and early pregnancy dNK cells promote uterine vascular growth and mediate trophoblast invasion, but do not exert their killing function. However, this may be an overly simplistic view. Evidence of specific dNK functional killer roles, as well as opposing effects of dNK cells on the uterine vasculature before and after conception, indicates the presence of a transitory secretory-stage dNK cell (s-dNK) phenotype with a unique angiodevelopmental profile during the peri-implantation period, that is that is functionally distinct from the angiomodulatory dNK cells that promote vessel destabilisation and vascular cell apoptosis to facilitate uterine vascular changes in early pregnancy. It is possible that abnormal activation and differentiation into the proposed transitory s-dNK phenotype may have implications in uterine pathologies ranging from infertility to cancer, as well as downstream effects on dNK cell differentiation in early pregnancy. Further, dysregulated transition into the angiomodulatory dNK phenotype in early pregnancy will likely have potential repercussions for adverse pregnancy outcomes, since impaired dNK function is associated with several obstetric complications. A comprehensive understanding of the uterine NK cell temporal differentiation pathway may therefore have important translational potential due to likely NK phenotypic functional implications in a range of reproductive, obstetric, and gynaecological pathologies.

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

STUDY QUESTION

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

SUMMARY ANSWER

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

WHAT IS KNOWN ALREADY

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

STUDY DESIGN, SIZE, DURATION

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

PARTICIPANTS/MATERIALS, SETTING, METHODS

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

MAIN RESULTS AND THE ROLE OF CHANCE

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

LIMITATIONS, REASONS FOR CAUTION

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

WIDER IMPLICATIONS OF THE FINDINGS

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

STUDY FUNDING/COMPETING INTEREST(S)

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

Cytokine imbalance at materno-embryonic interface as a potential immune mechanism for recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a prominent reproductive disease that distresses about 2%-5% of couples. RPL is the loss of two or more successive spontaneous pregnancies prior to the 20th week of embryo development. The commencement of pregnancy necessitates implantation of the embryo into responsive maternal decidua synchronized with the process of placentation, decidual and myometrial trophoblast incursion as well as refashioning of spiral blood arteries of uterus. The collapse of any of the processes fundamental for pregnancy success may result into an array of pregnancy problems including spontaneous pregnancy loss. Endometrium of human female manufactures an extensive range of cytokines during the proliferative and secretory stage of the menstrual cycle. These endometrial cytokines are thought as major players for making the uterus ready for embryo implantation and placental development during pregnancy. Decidual cytokines regulate the invasion of trophoblast and remodeling of spiral arteries as well as take part in immune suppression to accomplish the pregnancy. Deterrence of maternal rejection of embryo needs a regulated milieu, which takes place essentially at the embryo-maternal interface and the tissues of the uterus. The reasons of RPL remain anonymous in a large number of cases that lead to difficulties in management and severe trauma in couples. Cytokine modulatory therapies have been shown promising for preventing RPL. Further study of novel factors is wanted to establish more effective RPL treatment protocols. The present study aims to review the outcome of cytokine breach at materno-embryonic interface and the efficacy of cytokine modulatory therapies in RPL.

Application of ultrasound multimodal score in the assessment of endometrial receptivity in patients with artificial abortion

BACKGROUND

This study aimed to evaluate the value and feasibility of ultrasound multimodal score in the evaluation of endometrial receptivity in patients with artificial abortion (AA).

METHODS

Sixty-eight patients with AA (AA group) and 70 women of the childbearing age without any history of abortion (control group) were recruited between January 2018 and December 2018. All subjects received the examination of endometrium in the middle luteum phase (7-9 days after ovulation) with two-dimensional gray-scale ultrasound, two-dimensional color Doppler ultrasound, and three-dimensional ultrasound, and the quantitative scores were obtained and compared between two groups.

RESULTS

The quantitative score of endometrial receptivity was 10.46 ± 2.99 in the AA group and 13.49 ± 2.21 in the control group showing significant difference (p < 0.05).

CONCLUSIONS

Ultrasound multimodal quantitative scores can be used to evaluate the endometrial receptivity of patients with AA.

The effects and mechanisms of GM-CSF on endometrial regeneration

BACKGROUND

Endometrial injury can result in thin endometrium and subfertility. Granulocyte macrophage colony stimulating factor (GM-CSF) contributes to tissue repair, but its role in endometrial regeneration has not been investigated.

METHODS

To determine the effect of GM-CSF on endometrial regeneration, we established a mouse model of thin endometrium by uterine perfusion with 20 μL 90% ethanol. Thin endometrium in mice was featured by lowered endometrial thickness, decreased expression of Ki67 in glandular cells, and a reduced number of implantation sites. To explore the mechanism of GM-CSF on endometrial regeneration, endometrium was obtained from patients undergoing hysterectomy or hysteroscopy and endometrial biopsy. Effects of GM-CSF on primary cultured human endometrial glandular and stromal cells were examined by the 5-bromo-2'-deoxyuridine (BrdU) proliferation assay and transwell migration assay, followed by exploration of the potential signaling pathway.

RESULTS

GM-CSF intraperitoneal (i.p.) injection significantly increased endometrial thickness, expression of Ki67 in endometrial glandular cells, and the number of implantation sites. GM-CSF significantly promoted proliferation of primary human endometrial glandular cells and migration of stromal cells. GM-CSF activated p-Akt and increased expressions of p70S6K and c-Jun, which were blocked by LY294002.

CONCLUSION

We found that GM-CSF could improve endometrial regeneration, possibly through activating PI3K/Akt signaling pathway.

Characteristics of midluteal phase uterine artery hemodynamics in patients with recurrent pregnancy loss

AIM

To study the association in resistance to uterine artery blood flow and recurrent pregnancy loss (RPL) and find its potential influencing factors.

METHODS

A retrospective study was conducted in 870 RPL and 237 non-RPL patients visiting to the Clinic from January 2014 to February 2018. All participants underwent comprehensive examinations and were scanned by transvaginal Doppler ultrasonography during the midluteal phase to measure the pulsatility index (PI), resistance index (RI) and systolic/diastolic ratio (S/D) values of the left and right main uterine arteries. P value less than 0.05 was considered statistically significant.

RESULTS

The mean PI, RI and S/D values for uterine arteries were significantly higher in RPL patients than in non-RPL patients (P < 0.001). When subjects were grouped according to the different etiologies of RPL, significant higher indices of uterine arteries were found in RPL patients with antiphospholipid syndrome (P < 0.001), autoimmune diseases (P < 0.001), endocrinological abnormalities (P < 0.05), thrombophilia (P < 0.001), uterine anomalies (P < 0.01) and unexplained RPL (P < 0.001). No differences were found between patients with chromosomal anomalies and uterine arteries blood flow (P > 0.05). In RPL patients, mean PI, mean RI and mean S/D values shows no difference among groups (P > 0.05). The Similar results were observed in age and number of spontaneous abortion (P > 0.05).

CONCLUSION

Impaired uterine artery blood perfusion may be an underlying pathology to RPL, and it can be used as an independent risk factor for pregnancy failure.

BMP7 coordinates endometrial epithelial cell receptivity for blastocyst implantation through the endoglin pathway in cell lines and a mouse model

Bone morphogenetic protein (BMP) expression has been observed in the uterus in previous studies. However, the influence of BMP7 on blastocyst implantation remains unclear. Blastocysts first act on luminal endometrial epithelial cells during implantation. The purpose of the present study was to explore the influence of BMP7 on endometrial epithelial cells. A pregnancy animal model, and mouse and human endometrial epithelial cells were used in the present study. Transient knockdown, immunofluorescence assay, in vitro embryo implantation, BMP7 silencing, reverse transcription-quantitative polymerase chain reaction, western blotting, immunoprecipitation and Rac1 function assay were also performed. It was revealed that BMP7 concentration was increased in endometrial epithelial cells during the final pre-receptive and receptive stages of receptivity in the mouse endometrium. Additionally, BM7 acted on the transforming growth factor-β receptor, endoglin. Endoglin expression was detected in both stromal and endothelial cells apart from trophoblast expression. Following knockdown of BMP7, Rac-GTP was decreased in endometrial epithelial cells and the uterus. Knockdown of endoglin by small interfering RNA decreased the number of blastocysts and implantation regions. Additionally, BMP7 silencing and endoglin suppression of Ishikawa cells led to impaired JAr spheroid attachment. These findings suggest that BMP7 is associated with receptivity of the endometrium, indicating that BMP7 regulates receptivity of endometrial epithelial cells for implantation of blastocysts via the endoglin pathway.

Three-dimensional 3D ultrasound combined with power Doppler for the differential diagnosis of endometrial lesions among infertile women

OBJECTIVE

To assess three-dimensional (3D) ultrasound combined with power Doppler (PD) for the differential diagnosis of endometrial lesions among infertile women.

METHODS

A prospective study carried out at a reproductive medicine center in Luoyang, China, between January and December 2015. The inclusion criteria were asymptomatic infertility with normal endometrium or specific endometrial lesions. Participants were subdivided by whether they had normal endometrium (group 1, n=357), or endometrial lesions including polyps, hyperplasia, intrauterine adhesions, or endometritis (group 2, n=99). 3D PD and hysteroscopy were performed in the follicular phase. Endometrial thickness, volume, vascularization index (VI), flow index (FI), and vascularization flow index (VFI), and subendometrial VI, FI, and VFI were calculated. Endometrial lesions were confirmed by pathologic analysis.

RESULTS

The overall prevalence of endometrial lesions was 99/456 (21.3%). Endometrial thickness and volume were significantly larger in group 2 than in group 1 (9.96 ± 3.24 vs 8.15 ± 2.50 mm and 3.70 ± 2.54 vs 2.42 ± 1.64 cm³ , respectively; both P<0.001). Endometrial thickness and volume were larger among women with endometrial polyps and hyperplasia; endometrial VI, FI, and VFI were lower among women with intrauterine adhesions.

CONCLUSION

Three-dimensional PD has value for the differential diagnosis of endometrial lesions among infertile women.

CLINICAL TRIAL REGISTRATION

The trial is registered in the Chinese Clinical Trial Registry as ChiCTR1800015799.

Histological component quantification for the evaluation of endometrial receptivity in women with natural cycles undergoing in vitro fertilization/intracytoplasmic sperm injection

OBJECTIVE

Our aim was to evaluate the value of the volumetric fraction of vascular endothelial cells (EnVF) for determining endometrial receptivity in women undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI).

MATERIALS AND METHODS

The records of women undergoing IVF/ICSI between 2006 and 2010 were retrospectively reviewed. An endometrial biopsy was performed in the cycle prior to IVF/ICSI. EnVF was calculated from endometrial biopsy staining.

RESULTS

Twenty-seven patients who did not become pregnant, 8 who had a miscarriage, and 21 with a clinical pregnancy were included. The three groups were similar with respect to infertility and IVF characteristics. An EnVF ≤3.85 was associated with not becoming pregnant, an EnVF >5.29 with miscarriage, and a level between 3.86 and 5.29 was associated with clinical pregnancy (p = 0.001).

CONCLUSIONS

EnVF examined in the prior cycle may be a marker of endometrial receptivity and predict the chance of pregnancy in women undergoing IVF/ICSI.

Correlation between three-dimensional power Doppler and morphometric measurement of endometrial vascularity at the time of embryo implantation in women with unexplained recurrent miscarriage

Power Doppler in combination with three-dimensional (3D-PD) ultrasonography has been used as a noninvasive tool to evaluate the vascularity. However, it is unclear whether 3D-PD can accurately reflect endometrial vascularization and replace the invasive endometrial biopsy. This study aims to investigate the correlation between 3D-PD and micro vessel morphometric measurement of endometrial vascularity. Twenty-five women with unexplained recurrent miscarriage were recruited for 3D-PD and endometrial biopsy on precisely day LH + 7. Immunohistochemistry using vWF was employed to identify micro vessels in endometrial biopsy specimens followed by the use of morphometric technique to measure the mean vessel diameter and volume fractions. The vascularization index (VI), flow index (FI) and vascularization flow index (VFI) assessed by 3D-PD were calculated for both the endometrial and sub-endometrial regions. There were no significant correlations between any of the ultrasonographic measurements (endometrial thickness, endometrial volume, endometrial VI/FI/VFI, sub-endometrial volume, sub-endometrial VI/FI/VFI) and morphometric features (number of micro vessel, mean diameter of micro vessel and volume fraction measurement of vessel). This study indicates that endometrial vascularity assessed by 3D-PD could not be used to reflect changes in micro vessels of the endometrium at the time of embryo implantation in women with unexplained recurrent miscarriage.