Effect of vitamin D in addition to letrozole on the ovulation rate of women with polycystic ovary syndrome: protocol of a multicentre randomised double-blind controlled trial.

INTRODUCTION: Low vitamin D status is prevalent among women with polycystic ovary syndrome (PCOS). The objective of the study is to assess the effect of vitamin D supplementation on (1) the ovulation rate to letrozole and (2) other reproductive, endocrine and metabolic outcomes after 1 year of supplementation in women with PCOS. METHODS AND ANALYSIS: This is a multicentre, randomised, double-blind, controlled clinical trial. A total of 220 anovulatory women with PCOS diagnosed by the Rotterdam criteria will be recruited. They will be randomly assigned to either the (1) vitamin D supplementation group or (2) placebo group. Those in the vitamin D group will take oral Vitamin D3 50 000 IU/week for 4 weeks, followed by 50 000 IU once every 2 weeks for 52 weeks. Those who remain anovulatory after 6 months will be treated with a 6-month course of letrozole (2.5 mg to 7.5 mg for 5 days per cycle titrated according to response) for ovulation induction. The primary outcome is the ovulation rate. All statistical analyses will be performed using intention-to-treat and per protocol analyses. ETHICS AND DISSEMINATION: Ethics approval was sought from the Institutional Review Board of the participating units. All participants will provide written informed consent before joining the study. The results of the study will be submitted to scientific conferences and peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04650880.

Comparing blastocyst euploid rates between the progestin-primed and gonadotrophin-releasing hormone antagonist protocols in aneuploidy genetic testing: a randomised trial protocol.

INTRODUCTION: Progestin can inhibit the pituitary luteinising hormone (LH) surge during ovarian stimulation for in vitro fertilisation (IVF) and studies show progestin-primed ovarian stimulation (PPOS) is effective in blocking the LH surge in IVF. More and more centres are using PPOS because this regimen appears simpler and cheaper. This study aims to compare the euploidy rate of blastocysts following the PPOS protocol and the gonadotropin-releasing hormone antagonist protocol in women undergoing preimplantation genetic testing for aneuploidy (PGT-A). METHODS/ANALYSIS: This is a randomised trial. A total of 400 women undergoing PGT-A will be enrolled and randomised according to a computer-generated randomisation list to either (1) the antagonist group: an antagonist given once daily from day 6 of ovarian stimulation till the day of the ovulation trigger; or (2) the PPOS group: dydrogesterone from the first day of ovarian stimulation till the day of ovulation trigger. The primary outcome is the euploidy rate of blastocysts. ETHICS/DISSEMINATION: An ethical approval was granted from the ethics committee of assisted reproductive medicine in Shanghai JiAi Genetics and IVF institute (JIAIE2020-03). A written informed consent will be obtained from each woman before any study procedure is performed, according to good clinical practice. The results of this randomised trial will be disseminated in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: NCT04414748.

Endometrial mesenchymal stromal/stem cells improve regeneration of injured endometrium in mice.

BACKGROUND: The monthly regeneration of human endometrial tissue is maintained by the presence of human endometrial mesenchymal stromal/stem cells (eMSC), a cell population co-expressing the perivascular markers CD140b and CD146. Endometrial regeneration is impaired in the presence of intrauterine adhesions, leading to infertility, recurrent pregnancy loss and placental abnormalities. Several types of somatic stem cells have been used to repair the damaged endometrium in animal models, reporting successful pregnancy. However, the ability of endometrial stem cells to repair the damaged endometrium remains unknown. METHODS: Electrocoagulation was applied to the left uterine horn of NOD/SCID mice causing endometrial injury. Human eMSC or PBS was then injected into the left injured horn while the right normal horn served as controls. Mice were sacrificed at different timepoints (Day 3, 7 and 14) and the endometrial morphological changes as well as the degree of endometrial injury and repair were observed by histological staining. Gene expression of various inflammatory markers was assessed using qPCR. The functionality of the repaired endometrium was evaluated by fertility test. RESULTS: Human eMSC successfully incorporated into the injured uterine horn, which displayed significant morphological restoration. Also, endometrium in the eMSC group showed better cell proliferation and glands formation than the PBS group. Although the number of blood vessels were similar between the two groups, gene expression of VEGF-α significantly increased in the eMSC group. Moreover, eMSC had a positive impact on the regeneration of both stromal and epithelial components of the mouse endometrium, indicated by significantly higher vimentin and CK19 protein expression. Reduced endometrial fibrosis and down-regulation of fibrosis markers were also observed in the eMSC group. The eMSC group had a significantly higher gene expression of anti-inflammatory factor Il-10 and lower mRNA level of pro-inflammatory factors Ifng and Il-2, indicating the role of eMSC in regulation of inflammatory reactions. The eMSC group showed higher implantation sites than the PBS group, suggesting better endometrial receptivity with the presence of newly emerged endometrial lining. CONCLUSIONS: Our findings suggest eMSC improves regeneration of injured endometrium in mice.

Optimizing non-invasive preimplantation genetic testing: investigating culture conditions, sample collection, and IVF treatment for improved non-invasive PGT-A results.

PURPOSE: This study aimed to optimize the non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) in the laboratory by comparing two collection timing of the spent culture medium (SCM), two embryo rinsing protocols, and the use of conventional insemination instead of intracytoplasmic sperm injection (ICSI). METHODS: Results of two embryo rinsing methods (one-step vs sequential) and SCM collected on day 5 vs day 6 after retrieval were compared against trophectoderm (TE) biopsies as reference. Results from day 6 SCM in cycles fertilized by conventional insemination were compared with PGT-A using ICSI. RESULTS: The rate of concordance was higher in day 6 samples than in day 5 samples when the sequential method was used, in terms of total concordance (TC; day 6 vs day 5: 85.0% vs 60.0%, p = 0.0228), total concordance with same sex (TCS, 82.5% vs 28,0%, p < 0.0001), and full concordance with same sex (FCS, 62.5% vs 24.0%, p = 0.0025). The sequential method significantly out-performed the one-step method when SCM were collected on day 6 (sequential vs one-step, TC: 85.0% vs 64.5%, p = 0.0449; TCS: 82.5% vs 54.8%, p = 0.0113; FCS: 62.5% vs 25.8%, p = 0.0021). There was no significant difference in niPGT-A results between cycles fertilized by the conventional insemination and ICSI. CONCLUSION: We have shown a higher concordance rate when SCM was collected on day 6 and the embryos were rinsed in a sequential manner. Comparable results of niPGT-A when oocytes were fertilized by conventional insemination or ICSI. These optimization steps are important prior to commencement of a randomized trial in niPGT-A.

The functional roles of protein glycosylation in human maternal-fetal crosstalk.

BACKGROUND: The establishment of maternal-fetal crosstalk is vital to a successful pregnancy. Glycosylation is a post-translational modification in which glycans (monosaccharide chains) are attached to an organic molecule. Glycans are involved in many physiological and pathological processes. Human endometrial epithelium, endometrial gland secretions, decidual immune cells, and trophoblasts are highly enriched with glycoconjugates and glycan-binding molecules important for a healthy pregnancy. Aberrant glycosylation in the placenta and uterus has been linked to repeated implantation failure and various pregnancy complications, but there is no recent review summarizing the functional roles of glycosylation at the maternal-fetal interface and their associations with pathological processes. OBJECTIVE AND RATIONALE: This review aims to summarize recent findings on glycosylation, glycosyltransferases, and glycan-binding receptors at the maternal-fetal interface, and their involvement in regulating the biology and pathological conditions associated with endometrial receptivity, placentation and maternal-fetal immunotolerance. Current knowledge limitations and future insights into the study of glycobiology in reproduction are discussed. SEARCH METHODS: A comprehensive PubMed search was conducted using the following keywords: glycosylation, glycosyltransferases, glycan-binding proteins, endometrium, trophoblasts, maternal-fetal immunotolerance, siglec, selectin, galectin, repeated implantation failure, early pregnancy loss, recurrent pregnancy loss, preeclampsia, and fetal growth restriction. Relevant reports published between 1980 and 2023 and studies related to these reports were retrieved and reviewed. Only publications written in English were included. OUTCOMES: The application of ultrasensitive mass spectrometry tools and lectin-based glycan profiling has enabled characterization of glycans present at the maternal-fetal interface and in maternal serum. The endometrial luminal epithelium is covered with highly glycosylated mucin that regulates blastocyst adhesion during implantation. In the placenta, fucose and sialic acid residues are abundantly presented on the villous membrane and are essential for proper placentation and establishment of maternal-fetal immunotolerance. Glycan-binding receptors, including selectins, sialic-acid-binding immunoglobulin-like lectins (siglecs) and galectins, also modulate implantation, trophoblast functions and maternal-fetal immunotolerance. Aberrant glycosylation is associated with repeated implantation failure, early pregnancy loss and various pregnancy complications. The current limitation in the field is that most glycobiological research relies on association studies, with few studies revealing the specific functions of glycans. Technological advancements in analytic, synthetic and functional glycobiology have laid the groundwork for further exploration of glycans in reproductive biology under both physiological and pathological conditions. WIDER IMPLICATIONS: A deep understanding of the functions of glycan structures would provide insights into the molecular mechanisms underlying their involvement in the physiological and pathological regulation of early pregnancy. Glycans may also potentially serve as novel early predictive markers and therapeutic targets for repeated implantation failure, pregnancy loss, and other pregnancy complications.

Endometrial mesenchymal stromal/stem cells improve regeneration of injured endometrium in mice

BACKGROUND: The monthly regeneration of human endometrial tissue is maintained by the presence of human endometrial mesenchymal stromal/stem cells (eMSC), a cell population co-expressing the perivascular markers CD140b and CD146. Endometrial regeneration is impaired in the presence of intrauterine adhesions, leading to infertility, recurrent pregnancy loss and placental abnormalities. Several types of somatic stem cells have been used to repair the damaged endometrium in animal models, reporting successful pregnancy. However, the ability of endometrial stem cells to repair the damaged endometrium remains unknown. METHODS: Electrocoagulation was applied to the left uterine horn of NOD/SCID mice causing endometrial injury. Human eMSC or PBS was then injected into the left injured horn while the right normal horn served as controls. Mice were sacrificed at different timepoints (Day 3, 7 and 14) and the endometrial morphological changes as well as the degree of endometrial injury and repair were observed by histological staining. Gene expression of various inflammatory markers was assessed using qPCR. The functionality of the repaired endometrium was evaluated by fertility test. RESULTS: Human eMSC successfully incorporated into the injured uterine horn, which displayed significant morphological restoration. Also, endometrium in the eMSC group showed better cell proliferation and glands formation than the PBS group. Although the number of blood vessels were similar between the two groups, gene expression of VEGF-α significantly increased in the eMSC group. Moreover, eMSC had a positive impact on the regeneration of both stromal and epithelial components of the mouse endometrium, indicated by significantly higher vimentin and CK19 protein expression. Reduced endometrial fibrosis and down-regulation of fibrosis markers were also observed in the eMSC group. The eMSC group had a significantly higher gene expression of anti-inflammatory factor Il-10 and lower mRNA level of pro-inflammatory factors Ifng and Il-2, indicating the role of eMSC in regulation of inflammatory reactions. The eMSC group showed higher implantation sites than the PBS group, suggesting better endometrial receptivity with the presence of newly emerged endometrial lining. CONCLUSIONS: Our findings suggest eMSC improves regeneration of injured endometrium in mice.

Adrenomedullin has a pivotal role in trophoblast differentiation: A promising nanotechnology-based therapeutic target for early-onset preeclampsia.

Early-onset preeclampsia (EOPE) is a severe pregnancy complication associated with defective trophoblast differentiation and functions at implantation, but manifestation of its phenotypes is in late pregnancy. There is no reliable method for early prediction and treatment of EOPE. Adrenomedullin (ADM) is an abundant placental peptide in early pregnancy. Integrated single-cell sequencing and spatial transcriptomics confirm a high ADM expression in the human villous cytotrophoblast and syncytiotrophoblast. The levels of ADM in chorionic villi and serum were lower in first-trimester pregnant women who later developed EOPE than those with normotensive pregnancy. ADM stimulates differentiation of trophoblast stem cells and trophoblast organoids in vitro. In pregnant mice, placenta-specific ADM suppression led to EOPE-like phenotypes. The EOPE-like phenotypes in a mouse PE model were reduced by a placenta-specific nanoparticle-based forced expression of ADM. Our study reveals the roles of trophoblastic ADM in placental development, EOPE pathogenesis, and its potential clinical uses.

Randomised double-blind controlled trial of non-invasive preimplantation genetic testing for aneuploidy in in vitro fertilisation: a protocol paper.

INTRODUCTION: The success rate of in vitro fertilisation (IVF) treatment for couples with infertility remains low due to lack of a reliable tool in selecting euploid embryos for transfer. This study aims to compare the efficacy in embryo selection based on morphology alone compared with non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) and morphology in infertile women undergoing IVF. METHODS AND ANALYSIS: This is a randomised double-blind controlled trial conducted in two tertiary assisted reproduction centres. A total of 500 infertile women will be recruited and undergo IVF as indicated. They will be randomly assigned on day 6 after oocyte retrieval into two groups: the intervention group using morphology and niPGT-A and the control group based on morphology alone. In the control group, blastocysts with the best quality morphology will be replaced first. In the intervention group, blastocysts with the best morphology and euploid result of spent culture medium will be replaced first. The primary outcome is a live birth per the first embryo transfer. The statistical analysis will be performed with the intention to treat and per protocol. ETHICS AND DISSEMINATION: Ethics approval was sought from the institutional review board of the two participating units. All participants will provide written informed consent before joining the study. The results of the study will be submitted to scientific conferences and peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04474522.

Knowledge, attitudes and intention on fertility preservation among breast cancer patients.

Breast cancer is the most common cancer in reproductive age women. The aim of this study is to assess the knowledge, attitude and intention on fertility preservation among women diagnosed to have breast cancer. This is a multi-centre cross-sectional questionnaire study. Reproductive age women diagnosed with breast cancer attending Oncology, Breast Surgery and Gynaecology Clinics and support groups were invited to participate. Women filled in paper or electronic form of the questionnaire. 461 women were recruited and 421 women returned the questionnaire. Overall, 181/410 (44.1%) women had heard of fertility preservation. Younger age and higher education level were significantly associated with increased awareness of fertility preservation. Awareness and acceptance of the different fertility preservation methods in reproductive age women with breast cancer was suboptimal. However, 46.1% women felt that their fertility concerns affected their decision for cancer treatment in some way.

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.

Acupuncture and Doxylamine-Pyridoxine for Nausea and Vomiting in Pregnancy : A Randomized, Controlled, 2 × 2 Factorial Trial.

BACKGROUND: An effective and safe treatment for nausea and vomiting of pregnancy (NVP) is lacking. OBJECTIVE: To assess the efficacy and safety of acupuncture, doxylamine-pyridoxine, and a combination of both in women with moderate to severe NVP. DESIGN: Multicenter, randomized, double-blind, placebo-controlled, 2 × 2 factorial trial. (ClinicalTrials.gov: NCT04401384). SETTING: 13 tertiary hospitals in mainland China from 21 June 2020 to 2 February 2022. PARTICIPANTS: 352 women in early pregnancy with moderate to severe NVP. INTERVENTION: Participants received daily active or sham acupuncture for 30 minutes and doxylamine-pyridoxine or placebo for 14 days. MEASUREMENTS: The primary outcome was the reduction in Pregnancy-Unique Quantification of Emesis (PUQE) score at the end of the intervention at day 15 relative to baseline. Secondary outcomes included quality of life, adverse events, and maternal and perinatal complications. RESULTS: No significant interaction was detected between the interventions (P = 0.69). Participants receiving acupuncture (mean difference [MD], -0.7 [95% CI, -1.3 to -0.1]), doxylamine-pyridoxine (MD, -1.0 [CI, -1.6 to -0.4]), and the combination of both (MD, -1.6 [CI, -2.2 to -0.9]) had a larger reduction in PUQE score over the treatment course than their respective control groups (sham acupuncture, placebo, and sham acupuncture plus placebo). Compared with placebo, a higher risk for births with children who were small for gestational age was observed with doxylamine-pyridoxine (odds ratio, 3.8 [CI, 1.0 to 14.1]). LIMITATION: The placebo effects of the interventions and natural regression of the disease were not evaluated. CONCLUSION: Both acupuncture and doxylamine-pyridoxine alone are efficacious for moderate and severe NVP. However, the clinical importance of this effect is uncertain because of its modest magnitude. The combination of acupuncture and doxylamine-pyridoxine may yield a potentially larger benefit than each treatment alone. PRIMARY FUNDING SOURCE: The National Key R&D Program of China and the Project of Heilongjiang Province "TouYan" Innovation Team.

The role of spermatozoa-zona pellucida interaction in selecting fertilization-competent spermatozoa in humans.

Human fertilization begins when a capacitated spermatozoon binds to the zona pellucida (ZP) surrounding a mature oocyte. Defective spermatozoa-ZP interaction contributes to male infertility and is a leading cause of reduced fertilization rates in assisted reproduction treatments (ARTs). Human ejaculate contains millions of spermatozoa with varying degrees of fertilization potential and genetic quality, of which only thousands of motile spermatozoa can bind to the ZP at the fertilization site. This observation suggests that human ZP selectively interacts with competitively superior spermatozoa characterized by high fertilizing capability and genetic integrity. However, direct evidence for ZP-mediated sperm selection process is lacking. This study aims to demonstrate that spermatozoa-ZP interaction represents a crucial step in selecting fertilization-competent spermatozoa in humans. ZP-bound and unbound spermatozoa were respectively collected by a spermatozoa-ZP coincubation assay. The time-course data demonstrated that ZP interacted with a small proportion of motile spermatozoa. Heat shock 70 kDa protein 2 (HSPA2) and sperm acrosome associated 3 (SPACA 3) are two protein markers associated with the sperm ZP-binding ability. Immunofluorescent staining indicated that the ZP-bound spermatozoa had significantly higher expression levels of HSPA2 and SPACA3 than the unbound spermatozoa. ZP-bound spermatozoa had a significantly higher level of normal morphology, DNA integrity, chromatin integrity, protamination and global methylation when compared to the unbound spermatozoa. The results validated the possibility of applying spermatozoa-ZP interaction to select fertilization-competent spermatozoa in ART. This highly selective interaction might also provide diagnostic information regarding the fertilization potential and genetic qualities of spermatozoa independent of those derived from the standard semen analysis.

Effect of basal serum testosterone level on the ovarian response and the cumulative live birth rate in infertile women undergoing in vitro fertilization.

PURPOSE: To evaluate the effect of basal serum testosterone levels on the ovarian response and the cumulative live birth rate of infertile women undergoing in vitro fertilization (IVF). METHODS: It is a retrospective study in a university-affiliated assisted reproduction center in Hong Kong. Infertile women undergoing the first IVF cycle in the center between December 2012 and November 2016 with archived serum samples and available information on cumulative live birth were included for the analysis. RESULTS: A total of 1122 women were included for analysis. The median basal serum testosterone level was 0.53 (25-75th percentile: 0.40-0.67) nmol/L. Women with higher basal serum testosterone levels required a lower total dosage of gonadotrophin and a shorter duration of stimulation and had more oocytes retrieved. The cumulative live birth rates did not differ among women with serum testosterone levels in the four quartiles. Basal serum testosterone level was not a significant independent predictor of the cumulative live birth after adjusted for the women's age and number of normally fertilized oocytes in a binary logistic regression. The areas under the receiver operative characteristics (ROC) curves in predicting low or high ovarian response and the cumulative live birth were all below 0.6. CONCLUSION: Higher basal serum testosterone levels were associated with a better ovarian response but had no effect on the cumulative live birth rate of infertile women undergoing IVF.

Comparing the intercycle variation of serum anti-Mullerian hormone and antral follicle count measurements over four consecutive menstrual cycles.

OBJECTIVE: To compare the intercycle variation of serum anti-Mullerian hormone (AMH) and antral follicle count (AFC) measurements over four consecutive menstrual cycles. DESIGN: Observational study with secondary analysis using data from two previous randomized controlled trials. PATIENTS: Seventy-eight women from two previous randomized trials on the effect of dehydroepiandrosterone pretreatment on ovarian response in women undergoing in vitro fertilization (IVF) treatment. MEASUREMENTS: The intraclass correlation coefficients (ICC) for AFC and AMH across the four study cycles, as well as their predictive performance on poor ovarian response, were compared. RESULTS: No significant difference was observed in AMH (p = .608) across the four study cycles. AFC was significantly higher at 4 weeks before ovarian stimulation compared with 0, 8 and 12 weeks before ovarian stimulation (p < .05, Conover posthoc test). Both single-measures and average-measures ICC were significantly higher with AMH than with AFC. The areas under the receiver operating characteristic curve of the four AFC measurements in predicting poor ovarian response (defined as three or less oocytes retrieved) in the IVF cycle ranged from 0.657 to 0.743 with no significant difference (p > .05) among the four cycles, whereas those of the four AMH measurement ranged from 0.730 to 0.780 with no significant difference (p > .05) among the four cycles. CONCLUSIONS: Although both AFC and AMH are good predictors of ovarian response, intercycle repeatability was significantly better with serum AMH than AFC measurement. Both have no significant difference in their predictive performance on poor ovarian response when assessed within three months before IVF treatment, hence allowing pre-IVF assessment at more flexible timing.

The role of Notch signaling in endometrial mesenchymal stromal/stem-like cells maintenance.

Human endometrium undergoes cycles of regeneration in women of reproductive age. The endometrial mesenchymal stromal/stem cells (eMSC) contribute to this process. Notch signaling is essential for homeostasis of somatic stem cells. However, its role in eMSC remains unclear. We show with gain- and loss-of-function experiments that activation of Notch signaling promotes eMSC maintenance, while inhibition induces opposite effect. The activation of Notch signaling better maintains eMSC in a quiescent state. However, these quiescent eMSC can re-enter the cell cycle depending on the Notch and Wnt activities in the microenvironment, suggesting a crosstalk between the two signaling pathways. We further show that the Notch signaling is involved in endometrial remodeling event in a mouse menstrual-like model. Suppression of Notch signaling reduces the proliferation of Notch1+ label-retaining stromal cells and delays endometrial repair. Our data demonstrate the importance of Notch signaling in regulating the endometrial stem/progenitor cells in vitro and in vivo.

Three-dimensional culture models of human endometrium for studying trophoblast-endometrium interaction during implantation.

During implantation, a symphony of interaction between the trophoblast originated from the trophectoderm of the implanting blastocyst and the endometrium leads to a successful pregnancy. Defective interaction between the trophoblast and endometrium often results in implantation failure, pregnancy loss, and a number of pregnancy complications. Owing to ethical concerns of using in vivo approaches to study human embryo implantation, various in vitro culture models of endometrium were established in the past decade ranging from two-dimensional cell-based to three-dimensional extracellular matrix (ECM)/tissue-based culture systems. Advanced organoid systems have also been established for recapitulation of different cellular components of the maternal-fetal interface, including the endometrial glandular organoids, trophoblast organoids and blastoids. However, there is no single ideal model to study the whole implantation process leaving more research to be done pursuing the establishment of a comprehensive in vitro model that can recapitulate the biology of trophoblast-endometrium interaction during early pregnancy. This would allow us to have better understanding of the physiological and pathological process of trophoblast-endometrium interaction during implantation.

Hypoxia Regulates the Self-Renewal of Endometrial Mesenchymal Stromal/Stem-like Cells via Notch Signaling.

Human endometrium is an incredibly dynamic tissue undergoing cyclic regeneration and shedding during a woman's reproductive life. Endometrial mesenchymal stromal/stem-like cells (eMSC) contribute to this process. A hypoxic niche with low oxygen levels has been reported in multiple somatic stem cell types. However, the knowledge of hypoxia on eMSC remains limited. In mice, stromal stem/progenitor cells can be identified by the label-retaining technique. We examined the relationship between the label-retaining stromal cells (LRSC) and hypoxia during tissue breakdown in a mouse model of simulated menses. Our results demonstrated that LRSC resided in a hypoxic microenvironment during endometrial breakdown and early repair. Immunofluorescence staining revealed that the hypoxic-located LRSC underwent proliferation and was highly colocalized with Notch1. In vitro studies illustrated that hypoxia activated Notch signaling in eMSC, leading to enhanced self-renewal, clonogenicity and proliferation of cells. More importantly, HIF-1α played an essential role in the hypoxia-mediated maintenance of eMSC through the activation of Notch signaling. In conclusion, our findings show that some endometrial stem/progenitor cells reside in a hypoxic niche during menstruation, and hypoxia can regulate the self-renewal activity of eMSC via Notch signaling.