Current state of management of struma ovarii and preoperative imaging features: A retrospective case series study of 18 patients at a single institution.

AIM: Even though 95% of struma ovarii are benign, it is often overtreated because of the difficulty to distinguish it from malignancy. In this study, our aim was to evaluate the current state of the preoperative diagnosis and the selection of the surgical procedure, and to improve preoperative diagnostic accuracy by retrospectively reviewing imaging findings. METHODS: We retrospectively reviewed the clinical course and imaging characteristics of 18 patients who were diagnosed postoperatively with struma ovarii, pathologically, at our institution between 2015 and 2021. RESULTS: The preoperative diagnoses included benign ovarian tumor in eight cases, borderline in four cases, and malignant in six cases. None of the cases were diagnosed as struma ovarii preoperatively. Of the seven patients who had confirmed a desire for future childbearing, four patients were suspected for borderline or malignant tumor preoperatively, and underwent abdominal adnexectomy. In patients without a desire for childbearing, laparoscopic surgery was performed in only 45% of the patients whose preoperative diagnosis was benign. On magnetic resonance imaging (MRI), 54% of the cases showed enhanced solid components, which is characteristic of malignant tumors, but diffusion restriction was observed in only 11%. On computed tomography (CT), 78% of the cases showed a high attenuation lesion reflecting thyroid tissue. CONCLUSIONS: Struma ovarii is difficult to distinguish from malignancy preoperatively, making the choice of surgical approach complicated. A comprehensive evaluation of diffusion-weighted MRI and CT findings may improve the accuracy of preoperative diagnosis of struma ovarii.

Transcriptomic profiling analysis of human endometrial stromal cells treated with autologous platelet-rich plasma.

Purpose: To clarify the mechanisms of intrauterine platelet-rich plasma (PRP) infusion that support embryo implantation in in vitro fertilization treatment. Methods: Blood and endometrial samples were collected from four infertile women. Human endometrial stromal cells (HESCs) were cultured and passaged equally into four cell culture dishes in each patient. Two were treated with PRP twice, and the other two were treated with vehicle. Subsequently, two cultures with and without PRP were decidualized with 8-bromoadenosine 3',5'-cyclic AMP and progesterone for 5 days. Results: The gene expression in undifferentiated or decidualized HESCs with and without PRP was compared. In the microarray analysis, 381 and 63 differentially expressed genes were detected in undifferentiated and decidualized HESCs, respectively. In the undifferentiated HESCs, PRP was found to promote the gene expression associated with cell growth, tissue regeneration, proinflammatory response, and antibiotic effects. In decidualized HESCs, PRP was found to attenuate the gene expression involved in cell proliferation and inflammation by inhibiting the expression of phosphoinositide 3-kinase signaling. Conclusions: Platelet-rich plasma regulates the reprogramming of cell proliferation and inflammation depending on menstrual cycle phases in an appropriate manner, suggesting that PRP has the potential to increase endometrial thickness in the proliferative phase and improve immune tolerance in the secretory phase.

Increasing number of implantation failures and pregnancy losses associated with elevated Th1/Th2 cell ratio.

PROBLEM: We aimed to assess whether an imbalance of T-helper (Th) 1 and Th2 cells contributes to implantation failure and pregnancy loss. METHOD OF STUDY: In this cross-sectional study, 197 consecutive patients with a history of repeated implantation failure (RIF) after three or more embryo transfer (ET) cycles and/or recurrent pregnancy loss (RPL) after two or more clinical pregnancy losses underwent Th cell testing. After excluding 42 women aged ≥44 and 9 with vitamin D supplementation, we recruited 146 women including 79 with RIF and 81 with RPL. Fourteen women had a history of both RIF and RPL. We also recruited 45 fertile women and 40 general infertile women without a history of in vitro fertilization treatment. This study was approved by the local ethics committee. RESULTS: There was no significant difference in IFN-γ-producing Th1 and IL-4-producing Th2 cell levels between the fertile and general infertile women, but Th1 cell levels and the Th1/Th2 cell ratio were significantly higher in the women with ≥4 ET cycles and ≥2 pregnancy losses than in the fertile and general infertile women. In the general infertile women, the total livebirth rates including natural conception after two ET cycles in the normal and high Th1/Th2 groups (Th1/Th2 <11.8 and ≥11.8, respectively) were 66.7% and 87.5%, respectively (p = .395). CONCLUSIONS: A high Th1/Th2 cell ratio was linked to ≥4 implantation failure cycles and ≥2 pregnancy losses but not to general infertility.

Incidences and risk factors of moderate-to-severe ovarian hyperstimulation syndrome and severe hemoperitoneum in 1,435,108 oocyte retrievals.

RESEARCH QUESTION: What are the risk factors affecting the incidences of moderate-to-severe ovarian hyperstimulation syndrome (OHSS) and severe hemoperitoneum in assisted reproductive technology (ART) treatment cycles? DESIGN: A retrospective cohort study was conducted on 1,435,108 oocyte retrieval cycles among Japanese ART registry data between 2007 and 2015. The study included 11,378 cycles with moderate-to-severe OHSS, 1182 cycles with severe hemoperitoneum, including 27 cycles with both conditions, and 1,422,575 cycles without moderate-to-severe OHSS and severe hemoperitoneum. RESULTS: The incidences of moderate-to-severe OHSS and severe hemoperitoneum were 0.79% and 0.08%, respectively, and decreased by 0.57-fold and 0.29-fold from 2007 to 2015, respectively. In cycles with OHSS and cycles with hemoperitoneum women were younger (odds ratios [OR] 0.91 and 0.95, respectively) and had more retrieved oocytes (OR 1.09 and 1.01, respectively) compared with cycles without both complications. The use of a gonadotrophin-releasing hormone (GnRH) agonist protocol for ovarian stimulation was the highest risk factor in cycles with OHSS and hemoperitoneum (OR 1.83 and 1.24, respectively), followed by GnRH antagonist protocol (reference), gonadotrophin with or without oral medicine (OR 0.45 and 0.56, respectively) and natural or oral medicine (OR 0.02 and 0.19, respectively). In fresh embryo transfer, clinical pregnancy was associated with an increased risk of OHSS and hemoperitoneum (OR 1.19 and 2.34, respectively). CONCLUSIONS: The highest risk factors affecting OHSS and hemoperitoneum were the use of a GnRH agonist protocol and clinical pregnancy following fresh embryo transfer. The incidences of OHSS and hemoperitoneum have decreased yearly with a reduction of GnRH agonist use and fresh embryo transfer.

Analysis of the risk factors and treatment for repeated implantation failure: OPtimization of Thyroid function, IMmunity, and Uterine Milieu (OPTIMUM) treatment strategy.

PROBLEM: What are the pregnancy outcomes after the OPtimization of Thyroid function, Immunity, and Uterine Milieu (OPTIMUM) treatment strategy in patients with repeated implantation failure (RIF)? METHOD OF STUDY: Infertile women with a history of RIF after more than three embryo transfer (ET) cycles underwent implantation testing, including a hysteroscopy, endometrial biopsy for CD138 immunostaining and bacterial culture, and serum 25-hydroxyvitamin D3 , interferon-γ-producing helper T (Th1) cell, IL-4-producing helper T (Th2) cell, thyroid-stimulating hormone, thyroid peroxidase antibody, and thrombophilia screening between April 2017 and August 2018. We treated chronic endometritis with antibiotics, aberrant high Th1/Th2 cell ratios with vitamin D and/or tacrolimus intake, overt/subclinical hypothyroidism with levothyroxine, and thrombophilia with low-dose aspirin. Of the 116 RIF women, 88 women with 133 ET cycles were recruited from a questionnaire-based survey regarding pregnancy outcomes. Fifty-nine consecutive RIF patients without the OPTIMUM treatment strategy were also recruited as a control. RESULTS: The 116 women with RIF after the OPTIMUM treatment strategy were 38.3 ± 3.8 years old and had an implantation failure history over 5 (3-19) ET cycles. Implantation testing identified impaired intrauterine circumstances in 75 women (64.7%), an aberrant elevated Th1/Th2 cell ratio in 56 women (48.3%), and thyroid abnormalities in 33 women (28.4%). Cumulative ongoing pregnancy rates including spontaneous pregnancy in the patients aged < 40 and ≥ 40 years were 72.7% and 45.5% within two ET cycles, respectively. The pregnancy outcomes in the OPTIMUM group were significantly higher than those in the control. CONCLUSIONS: The OPTIMUM treatment strategy improved pregnancy outcomes in patients with RIF.

Effect of thyroxine treatment on pregnancy outcomes in infertile Japanese women with TSH levels between 2.5 µIU/mL and the upper reference limit: a retrospective study.

Recent randomized controlled studies have revealed that levothyroxine (LT4) treatment improves pregnancy outcomes only in infertile women with subclinical hypothyroidism who have thyroid autoantibodies (TAs), but not for those with high TSH levels within the normal range who have TAs. Here, we retrospectively investigated pregnancy outcomes in infertile Japanese women with 2.5 µIU/mL ≤ TSH < upper reference limit (URL). Between 2012 and 2018, 286 patients diagnosed with infertility were followed for more than 1 year at our institution. Among them, we included 106 patients with 2.5 µIU/mL ≤ TSH < URL. We divided these patients into four groups based on the combination of TA positivity and LT4 treatment status to assess the effects of LT4 treatment considering TA positivity on the incidence of pregnancy or miscarriage. In this study, we did not find any significant differences in the rates of pregnancy or miscarriage among the four groups (p = 0.81 and 0.52, respectively). In addition, logistic regression analysis showed that age and history of miscarriage were associated with the incidence of pregnancy, but presence of TAs and LT4 treatment status were not and that no variables examined were associated with the incidence of miscarriage. In summary, we were not able to demonstrate the benefit of LT4 treatment for pregnancy outcomes in Japanese euthyroid infertile women with 2.5 µIU/mL ≤ TSH < URL regardless of TA status in this study.

The actions of resveratrol in decidualizing endometrium: acceleration or inhibition?†.

Resveratrol, a natural polyphenolic compound, is widely studied for its anti-inflammatory and antisenescent properties. Recently, two studies reported seemingly conflicting findings on the actions of resveratrol on decidualization of human endometrial stromal cells (HESCs). One study by Ochiai et al. demonstrated that resveratrol inhibits decidual transformation of primary cultured HESCs. The other study by Mestre Citrinovitz et al., showed that resveratrol enhances decidualization of HESCs in culture. At a glance, the reason for these opposing observations seems puzzling. However, recent studies demonstrated that decidualization is a multistep process, which starts with an acute proinflammatory stress response that lasts for several days and is followed by the emergence of stress-resistant decidual cells as well as senescent decidual cells. The balance between these decidual subpopulations may determine if the cycling endometrium can successfully transition into the decidua of pregnancy upon embryo implantation. Here, we explore the importance of timing of drugs aimed at modulating the decidual response. We posit that resveratrol treatment during the initial proinflammatory decidual phase, i.e., coinciding with the implantation window in vivo, inhibits decidual transformation of the endometrium. However, when given after the initial phase, resveratrol may promote decidualization by inhibiting decidual senescence. Further, if restricted to the proliferative phase, resveratrol may promote ovarian function without adversely impacting on embryo implantation or decidualization. Thus, failure to align drug interventions with the correct phase of the menstrual cycle may negate beneficial clinical effects and results in adverse reproductive outcomes.

Preconception resveratrol intake against infertility: Friend or foe?

BACKGROUND: Resveratrol is an antiaging, antioxidant, anti-inflammatory, and insulin-sensitizing natural polyphenolic compound. Growing evidence indicates that resveratrol has potential therapeutic effects in infertile women with diminished ovarian function, polycystic ovary syndrome (PCOS), or endometriosis. However, only one clinical trial in women undergoing in vitro fertilization (IVF) cycles using resveratrol has ever been reported. This review focuses on the potential therapeutic effects of resveratrol on pregnancy and on its advantages and disadvantages in pregnancy outcomes during infertility treatment. METHODS: We performed a literature review to describe the known impacts of resveratrol on the ovary and endometrium. RESULTS: Resveratrol upregulates sirtuin (SIRT)1 expression in ovaries, which is associated with protection against oxidative stress. It leads to the activation of telomerase activity and mitochondrial function, improving ovarian function. In the endometrium, resveratrol downregulates the CRABP2-RAR pathway leading to suppressing decidual and senescent changes of endometrial cells, which is essential for embryo implantation and placentation. Moreover, resveratrol may also induce deacetylation of important decidual-related genes. CONCLUSIONS: Resveratrol has potential therapeutic effects for improving ovarian function; however, it also has anti-deciduogenic actions in uterine endometrium. In addition, its teratogenicity has not yet been ruled out; thus, resveratrol should be avoided during the luteal phase and pregnancy.

Analysis of 122 triplet and one quadruplet pregnancies after single embryo transfer in Japan.

RESEARCH QUESTION: What is the prevalence of triplet and quadruplet pregnancies after single embryo transfer (SET) in Japan. DESIGN: A retrospective observational study was conducted on 274,605 pregnancies after 937,848 SET cycles in registered assisted reproductive technology (ART) data from the Japanese ART national registry database between 2007 and 2014. A questionnaire survey of ART centres was also conducted. Data on pregnancies with embryo division into three or more after SET were analysed. RESULTS: According to the Japanese ART national registry database, SET resulted in 109 triplet pregnancies (0.04% of pregnancies), and the questionnaire reports from 31 centres revealed 33 triplet and one quadruplet pregnancies. After exclusion of 20 duplicated cases, 122 triplet and one quadruplet pregnancies included 46 monochorionic (one gestational sac [37.4%]), 18 dichorionic (two gestational sacs [14.6%]) and 59 trichorionic pregnancies (three gestational sacs [48.0%]). Compared with singleton pregnancies, patients with monozygotic triplet or quadruplet pregnancies were less frequently diagnosed with unexplained infertility (P = 0.004), more often received gonadotrophin injections for ovarian stimulation in 39 cases with information available (P = 0.021) and underwent more blastocyst transfers and assisted hatching (P = 0.002 and P < 0.001, respectively). The proportion of live birth, defined as at least one baby born, excluding induced abortion, was 64.6% (73/116 pregnancies) of monozygotic triplet or quadruplet pregnancies. CONCLUSIONS: Combined Japanese ART national registry and survey data revealed 122 triplet and one quadruplet pregnancies, the majority after cryopreserved embryo transfer. Most were conceived after blastocyst transfer and often after assisted hatching, which are potential risk factors for zygotic splitting.

Influence of resveratrol supplementation on IVF-embryo transfer cycle outcomes.

RESEARCH QUESTION: Does resveratrol, a polyphenolic compound, affect IVF-embryo transfer outcomes? DESIGN: This single-centre, cross-sectional retrospective study was designed to compare the outcomes of embryo transfer cycles in women receiving resveratrol supplementation (200 mg/day) continuously (RES group) with a control group (non-RES group). Of 8686 embryo transfer cycles, 1409 cycles with poor prognostic factors were excluded, including cycles in women aged ≥43 years and those with poor-quality embryos. The RES group (204 cycles, 102 women) was compared with the non-RES group (7073 cycles, 2958 women). RESULTS: After matching patients by age at the time of oocyte retrieval, grade and developmental stage of embryos, number of embryos transferred, and fresh or vitrified-warmed embryo transfer, multivariate logistic regression analysis showed that resveratrol supplementation is strongly associated with a decrease in clinical pregnancy rate [odds ratio (OR) 0.539, 95% confidence interval (CI) 0.341-0.853] and an increased risk of miscarriage (OR 2.602, 95% CI 1.070-6.325). CONCLUSIONS: Resveratrol supplementation during embryo transfer cycles appears to be detrimental for pregnancy outcomes. An analysis of the supplementation protocol and randomized controlled studies are needed.

Resveratrol inhibits decidualization by accelerating downregulation of the CRABP2-RAR pathway in differentiating human endometrial stromal cells.

Pregnancy critically depends on the transformation of the human endometrium into a decidual matrix that controls embryo implantation and placenta formation, a process driven foremost by differentiation and polarization of endometrial stromal cells into mature and senescent decidual cells. Perturbations in the decidual process underpin a spectrum of prevalent reproductive disorders, including implantation failure and early pregnancy loss, emphasizing the need for new therapeutic interventions. Resveratrol is a naturally occurring polyphenol, widely used for its antioxidant and anti-inflammatory properties. Using primary human endometrial stromal cell (HESC) cultures, we demonstrate that resveratrol has anti-deciduogenic properties, repressing not only the induction of the decidual marker genes PRL and IGFBP1 but also abrogating decidual senescence. Knockdown of Sirtuin 1, a histone deacetylase activated by resveratrol, restored the expression of IGFBP1 but not the induction of PRL or senescence markers in decidualizing HESCs, suggesting involvement of other pathways. We demonstrate that resveratrol interferes with the reprogramming of the retinoic acid signaling pathway in decidualizing HESCs by accelerating down-regulation of cellular retinoic acid-binding protein 2 (CRABP2) and retinoic acid receptor (RAR). Notably, knockdown of CRABP2 or RAR in HESCs was sufficient to recapitulate the anti-deciduogenic effects of resveratrol. Thus, while resveratrol has been advanced as a potential fertility drug, our results indicate it may have detrimental effects on embryo implantation by interfering with decidual remodeling of the endometrium.

Combination Treatment of Preoperative Embryo Cryopreservation and Endoscopic Surgery (Surgery-ART Hybrid Therapy) in Infertile Women with Diminished Ovarian Reserve and Uterine Myomas or Ovarian Endometriomas.

STUDY OBJECTIVE: To analyze the clinical outcomes of and predictive factors for the therapeutic effect of combination treatment of preoperative embryo cryopreservation and endoscopic surgery (surgery-assisted reproductive technology [ART] hybrid therapy) in infertile women with diminished ovarian reserve (DOR) with uterine fibroids and/or ovarian endometriomas. DESIGN: Retrospective cohort study. SETTING: Data from all patients who underwent surgery-ART hybrid therapy at Juntendo University Hospital and Sugiyama Clinic between 2014 and 2016 were analyzed retrospectively. We compared women who experienced live birth (success group) and implantation failure or miscarriage (failure group) after surgery-ART hybrid therapy and evaluate the predictive factors for live birth. PATIENTS: A total of 39 infertile women underwent surgery-ART hybrid therapy with 86 embryo transfer cycles. INTERVENTIONS: All women underwent ART treatment for embryo cryopreservation preoperatively, reproductive surgery, and warmed embryo transfer after the postoperative contraceptive interval (surgery-ART hybrid therapy) for women with DOR (anti-Müllerian hormone <1.0 ng/mL) and/or advanced reproductive age (>40 years) with uterine myomas and/or ovarian endometriomas who required surgery. RESULTS: Among 39 women underwent surgery-ART hybrid therapy, 1 woman acquired no embryo after oocyte retrieval trials and abandoned efforts to conceive, 14 experienced childbirth (success group) and 24 (63.2%) experienced implantation failure or miscarriage (failure group) after surgery-ART hybrid therapy. The median patient age was 40 years (interquartile range [IQR], 38-41 years) in the success group and 41.5 years (IQR, 41-42 years) in the failure group (p = .032). The respective serum anti-Müllerian hormone levels were 2.5 ng/mL (range, 0.1-8.6 ng/mL) and 1.3 ng/mL (range, 0.1-4.2 ng/mL) (p = .396), and the respective numbers of preoperative frozen were 5.0 (range, 4.0-6.0) and 2.0 (range, 1.0-3.0) (p < .001). There were no significant differences in surgical findings of myomas and endometriosis between the 2 groups. Compared with the 24 women who experienced hybrid therapy failure, the 14 who underwent successful surgery-ART hybrid therapy were significantly younger and had a greater number of cryopreserved embryos. CONCLUSION: Successful surgery-ART hybrid therapy requires a sufficient preoperative age-specific number of frozen embryos, establishment of ART treatment with stable pregnancy outcomes and skillful reproductive surgery, and a strong desire of the patient and doctor for pregnancy.

Reciprocal changes of H3K27ac and H3K27me3 at the promoter regions of the critical genes for endometrial decidualization.

AIM: Decidualization is essential for embryo implantation and placental development. We aimed to obtain transcriptome and epigenome profiles for primary endometrial stromal cells (ESCs) and in vitro decidualized cells. MATERIALS & METHODS: ESCs isolated from human endometrial tissues remained untreated (D0), or decidualized for 4 days (D4) and 8 days (D8) in the presence of 8-bromo-cAMP and progesterone. RESULTS: Among the epigenetic modifications examined (DNA methylation, H3K27ac, H3K9me3 and H3K27me3), the H3K27ac patterns changed most dramatically, with a moderate correlation with gene expression changes, upon decidualization. Subsets of up- and down-regulated genes upon decidualization were associated with reciprocal changes of H3K27ac and H3K27me3 modifications at their promoter region, and were enriched with genes essential for decidualization such as WNT4, ZBTB16, PROK1 and GREB1. CONCLUSION: Our dataset is useful to further elucidate the molecular mechanisms underlying decidualization.

Vitamin D Regulates Maternal T-Helper Cytokine Production in Infertile Women.

Vitamin D (VD) deficiency is associated with reproductive failure. However, the relationship between VD and maternal immunity remains unclear. We investigated the clinical efficacy of VD in maternal T-helper (Th) cytokines in 276 infertile women and examined for Th1 and Th2 cells based on the deficient, insufficient, and sufficient serum 25-hydroxyvitamin D3 (25[OH]VD) levels (<12, 12⁻30, and >30 ng/mL, respectively). Most infertile women had a low-level of VD (87.3%). Immunological tests of pre-/post-VD supplementation were performed in patients who were deficient and insufficient in VD. Of 23 patients, 11 (47.8%) exhibited sufficient VD levels after supplementation. Th1/Th2 cell ratio in patients with insufficient VD was significantly decreased after supplementation (p = 0.004). After supplementation, serum 25(OH)VD levels of the patients: 11 in the sufficient group showed significant decreases in Th1 cell level and Th1/Th2 cell ratio (p = 0.032 and 0.010, respectively), whereas no significant differences in Th1/Th2 cell ratio were recognized in the insufficient group. Furthermore, mid-luteal endometrial biopsies (n = 18) were processed for primary cultures and measured interferon [IFN]-γ and interleukin [IL]-4 in condition media. Decidualizing cultures with 1,25-dihydroxvitamin D3 (1,25[OH]2VD) decreased IFN-γ. Sufficient VD supplementation in women with insufficient VD may optimize maternal T-helper cytokines during pregnancy via rebalancing the Th1/Th2 cell ratio.

Infertility treatment strategy involving combined freeze-all embryos and single vitrified-warmed embryo transfer during hormonal replacement cycle for in vitro fertilization of women with hypogonadotropic hypogonadism.

AIM: Hypogonadotropic hypogonadism (HH) is a condition caused by the deficient secretion of pituitary gonadotropins, leading to diminished ovarian function. Several studies of in vitro fertilization (IVF) in women with HH revealed acceptable clinical pregnancy outcomes but high multiple pregnancy rates after multiple fresh embryo transfer (ET). The purpose of this study was to analyze the outcomes of combined freeze-all embryos and single vitrified-warmed ET in women with HH. METHODS: Of 91 infertile women with HH (basal luteinizing hormone and follicle-stimulating hormone levels <2.0 mIU/mL), we excluded patients aged ≥40 years (n = 2) and women who preferred fresh ET (n = 10). Seventy-nine women underwent 117 oocyte retrieval cycles and 135 vitrified-warmed ET during hormone replacement (HR) cycles from 2008 to 2014 at the Kato Ladies Clinic and Juntendo University Hospital. RESULTS: In 26 single cleavage ET cycles, the rates of clinical pregnancy and live birth were 34.6% (9/26 ET) and 26.9% (7/26 ET), respectively. Regarding the outcomes after single vitrified-warmed blastocyst transfer, clinical pregnancy and live birth rates were 65.1% (71/109 ET) and 50.5% (55/109 ET), respectively. Multiple conceptions and ovarian hyperstimulation syndrome did not occur in any of the women with HH. CONCLUSION: Our results demonstrated that IVF followed by single vitrified-warmed ET in adjusted endocrine milieu during the HR cycle is an effective fertility treatment for women with HH and decreases the incidence of complications, including multiple conceptions.

Reprogramming of the retinoic acid pathway in decidualizing human endometrial stromal cells.

Upon breaching of the endometrial surface epithelium, the implanting embryo embeds in the decidualizing stroma. Retinoic acid (RA), a metabolite of vitamin A, is an important morphogen during embryonic and fetal development, although the role of the RA pathway in the surrounding decidual cells is not understood. Here we show that decidual transformation of human endometrial stromal cells (HESCs) results in profound reprogramming of the RA signaling and metabolism pathways. Differentiating HESCs downregulate the intracellular carrier proteins CRABP2 and FABP5, responsible for transfer and binding of RA to the nuclear receptors RAR and PPARß/δ, respectively. Furthermore, the expression of RAR, the receptor that mediates the pro-apoptotic effects of RA, was also inhibited. By contrast, PPARß/δ, which transduces the differentiation responses of RA, was upregulated. Decidualization was also associated with increased expression of retinol-binding protein 4 (RBP4) and various enzymes involved in the metabolism of RA and its precursor, retinaldehyde (Rald), including CYP26A1, DHRS3, and RDH12. Exposure of differentiating HESCs to RA or Rald reversed the inhibition of the CRABP2-RAR pathway, perturbed the expression of decidual marker genes and triggered cell death. Taken together, the data demonstrate that decidualizing HESCs silence RA signaling by downregulating key cytoplasmic binding proteins and by increasing retinoid metabolism. However, excessive RA exposure is toxic for decidual cells and triggers a response that may lead to pregnancy failure.