The role of iron in the pathogenesis of endometriosis: a systematic review

Glypican3 and serglycin as potential biomarkers involved in the pathogenesis of ovarian endometriosis

Endometriosis, a non-malignant gynecological disorder characterized by debilitating symptoms, displays several cancer-like characteristics, including metastatic behavior and extracellular matrix (ECM) remodeling. The dynamics of ECM are largely influenced by proteoglycans (PGs), a family of glycosaminoglycan (GAG)-decorated proteins known for their regulatory impact on cellular behavior through ECM modulation. This study aimed to investigate the dysregulated expression of 20 PG genes in ovarian endometrioma (n = 24) in comparison to eutopic endometrial tissue samples (n = 16) from patients diagnosed with ovarian endometriosis, employing quantitative real-time PCR (qPCR) and immunohistochemistry (IHC). qPCR screening identified four upregulated PG genes-glypican 3 (GPC3), decorin (DCN), serglycin (SRGN), and glypican 5 (GPC5)-whereas 16 PG genes were found to be downregulated. In ovarian endometrioma, relative to eutopic endometrial tissue, GPC3 and SRGN expression were further verified to be significantly overexpressed by 18.6-fold (P < 0.05) and 6.7-fold (P < 0.01), respectively, whereas brevican (BCAN) and syndecan 4 (SDC4) were markedly downregulated by approximately 90 % and 86 %, respectively (both P < 0.001). IHC staining further validated the significant overexpression of GPC3 protein in ovarian endometrioma compared to eutopic and control endometrial tissues (P < 0.0001). In-silico analysis using the Enrichr database identified enriched functional pathways associated with the top overexpressed genes, such as hypoxia, glycolysis, and WNT signaling, known to be implicated in endometriosis. These findings suggest that the overexpression of GPC3 and SRGN may contribute to the pathogenesis of ovarian endometrioma, highlighting their potential as biomarkers and therapeutic targets for this disease.

Endometriosis: An Immunologist's Perspective

Endometriosis, a complex inflammatory disease, affects a significant proportion of women of reproductive age, approximately 10-15%. The disease involves the growth of endometrial glands and stroma outside the uterine cavity, leading to tissue remodeling and fibrosis. Hormonal imbalances, accompanied by local and general inflammation and pain, are key features of endometriosis. Endometriotic lesions are associated with the overproduction of cytokines, metalloproteinases, prostaglandins, reactive oxygen radicals, and extracellular vesicles. Genetic predisposition and cytokine gene polymorphisms have been documented. Macrophages, dendritic cells, mast cells, Th1 in the early phase, Th2 in the late phase, and T regulatory cells play a crucial role in endometriosis. Reduced NK cell function and impaired immune vigilance contribute to endometrial growth. The strong inflammatory condition of the endometrium poses a barrier to the proper implantation of the zygote, contributing to the infertility of these patients. Cytokines from various cell types vary with the severity of the disease. The role of microbiota in endometriosis is still under study. Endometriosis is associated with autoimmunity and ovarian cancer. Hormonal treatments and surgery are commonly used; however, recent interest focuses on anti-inflammatory and immunomodulatory therapies, including cytokine and anti-cytokine antibodies. Modulating the immune response has proven critical; however, more research is needed to optimize treatment for these patients.

Endometrial Aging and Reproductive Decline: The Central Role of Mitochondrial Dysfunction

Socioeconomic factors have led an increasing number of women to postpone childbirth, thereby elevating the risks of reduced fertility, pregnancy complications, preterm birth, cesarean delivery, and chromosomal abnormalities. While diminished oocyte quality is a well-established contributor to age-related infertility, endometrial dysfunction also plays a pivotal role. Optimizing both oocyte quality and endometrial health is essential for enhancing reproductive outcomes. Although aging has been defined by twelve hallmarks, research specifically addressing age-related changes in endometrial function remains limited. This review examines the process of endometrial aging, with a particular emphasis on mitochondrial function. A comprehensive literature search was conducted using PubMed and Google Scholar to identify relevant studies published up to 31 January 2025. Endometrial aging is driven by multiple biological mechanisms, most notably the decline in endometrial receptivity. Key contributing factors include hormonal dysregulation, chronic inflammation, cell cycle arrest, genomic instability, epigenetic alterations, telomere attrition, and mitochondrial dysfunction. Among these, mitochondrial dysfunction emerges as a central driver of the aging process. Endometrial senescence, precipitated by irreversible mitochondrial impairment, may underlie the progressive decline in reproductive potential. Elucidating the role of mitochondrial dysfunction in aging provides critical insights into the molecular basis of fertility decline, particularly through its impact on endometrial receptivity.

Adenomyosis-associated infertility: an update of the immunological perspective

Adenomyosis is characterized by the invasion of endometrial glands and stroma into the myometrium. Its clinical manifestations often include dysmenorrhoea, excessive menstrual bleeding and infertility. Reduced pregnancy and live birth rates and an increased miscarriage rate are observed in women with adenomyosis. This review summarizes relevant advances and presents the underlying mechanisms of adenomyosis-associated infertility from an immunological perspective. Individuals with adenomyosis exhibit imbalances in immune cell subpopulations and the endocrine hormone-immunomodulatory axis. These immunological alterations may be key contributors to, or at least accomplices in, impaired endometrial receptivity. In addition, adenomyosis often occurs in association with endometriosis, uterine leiomyoma or endometrial polyps, which are pathogenetically relevant; their similarities and differences are discussed from an immunological perspective. The clinical diagnostic criteria of adenomyosis are not perfect, and the pathogenesis remains to be fully explored. Therefore screening for effective targets for early diagnosis and treatment at the cellular and molecular levels from the immunological point of view holds great potential, which will be of great importance in preventing this disease and improving women's reproductive health.

Advancing endometriosis detection in daily practice: a deep learning-enhanced multi-sequence MRI analytical model

BACKGROUND AND PURPOSE

Endometriosis affects 5-10% of women of reproductive age. Despite its prevalence, diagnosing endometriosis through imaging remains challenging. Advances in deep learning (DL) are revolutionizing the diagnosis and management of complex medical conditions. This study aims to evaluate DL tools in enhancing the accuracy of multi-sequence MRI-based detection of endometriosis.

METHOD

We gathered a patient cohort from our institutional database, composed of patients with pathologically confirmed endometriosis from 2015 to 2024. We created an age-matched control group that underwent a similar MR protocol without an endometriosis diagnosis. We used sagittal fat-saturated T1-weighted (T1W FS) pre- and post-contrast and T2-weighted (T2W) MRIs. Our dataset was split at the patient level, allocating 12.5% for testing and conducting seven-fold cross-validation on the remainder. Seven abdominal radiologists with experience in endometriosis MRI and complex surgical planning and one women's imaging fellow with specific training in endometriosis MRI reviewed a random selection of images and documented their endometriosis detection.

RESULTS

395 and 356 patients were included in the case and control groups respectively. The final 3D-DenseNet-121 classifier model demonstrated robust performance. Our findings indicated the most accurate predictions were obtained using T2W, T1W FS pre-, and post-contrast images. Using an ensemble technique on the test set resulted in an F1 Score of 0.881, AUROCC of 0.911, sensitivity of 0.976, and specificity of 0.720. Radiologists achieved 84.48% and 87.93% sensitivity without and with AI assistance in detecting endometriosis. The agreement among radiologists in predicting labels for endometriosis was measured as a Fleiss' kappa of 0.5718 without AI assistance and 0.6839 with AI assistance.

CONCLUSION

This study introduced the first DL model to use multi-sequence MRI on a large cohort, showing results equivalent to human detection by trained readers in identifying endometriosis.

Targeting ferroptosis for the treatment of female reproductive system disorders

Ferroptosis, a regulated form of cell death driven by iron-dependent lipid peroxidation, has emerged as a critical factor in female reproductive health and has been implicated in disorders such as polycystic ovary syndrome, premature ovarian insufficiency, endometriosis, and ovarian cancer. This review explores the intricate molecular mechanisms underlying ferroptosis, emphasizing its reliance on iron metabolism and oxidative stress, which disrupt key processes in reproductive tissues, including granulosa cell function, folliculogenesis, and embryo implantation. Increasing evidence linking ferroptosis to these conditions offers new therapeutic opportunities, with iron chelators, lipid peroxidation inhibitors, and antioxidants showing the potential to alleviate reproductive dysfunction by modulating ferroptotic pathways. In ovarian cancer, ferroptosis inducers combined with conventional cancer therapies, such as chemotherapy, provide promising strategies to overcome drug resistance. This review synthesizes current knowledge on ferroptosis and highlights its importance as a therapeutic target in reproductive health, emphasizing the need for further research to refine and expand treatment options, evaluate their applicability in clinical settings, and explore their role in fertility preservation. By advancing our understanding of ferroptosis regulation, these therapeutic approaches could lead to novel treatments for reproductive disorders and cancers, offering new hope for improving outcomes in women's health and cancer therapy.

Ferroptosis in Endometriosis: Traditional Chinese Medicine Interventions and Mechanistic Insights

Endometriosis (EMS) is a chronic, estrogen-dependent inflammatory disease affecting 5-10% of women of reproductive age, characterized by the growth of endometrial tissue on the outside of the uterus. The dysregulation of iron metabolism leads to the accumulation of iron ions at the lesion sites, resulting in oxidative stress and pro-inflammatory responses that promote the progression of EMS. The mechanisms underlying ferroptosis in EMS primarily involve iron accumulation, lipid peroxidation, and loss of glutathione peroxidase 4 activity. These mechanisms confer resistance to ferroptosis within the ectopic tissues and facilitate cell survival and proliferation. Traditional Chinese medicine (TCM) has demonstrated therapeutic potential for modulating ferroptosis. Studies have shown that TCM monomers may regulate ferroptosis by modulating iron transport proteins and anti-oxidant defense mechanisms. TCM formulas employ distinct treatment strategies depending on the stage of EMS: in the early stages, they promote ferroptosis to control lesion growth, whereas in the later stages, they inhibit ferroptosis to reduce oxidative stress and inflammation in order to improve reproductive health and slow disease progression. This study provides a new perspective on potential therapeutic strategies for the management of EMS by summarizing the role of ferroptosis in its pathological mechanisms and reviewing findings on the use of TCM in regulating ferroptosis.

Mechanisms of Endometrioma-Mediated Ovarian Damage: Myths and Facts

Ovarian endometriomas (OEMs), cystic formations within the ovaries, are a significant manifestation of endometriosis and present in 20-40% of affected women. Despite extensive research, the pathogenesis of endometriosis remains unclear, with retrograde menstruation, coelomic metaplasia, and lymphatic dissemination being proposed mechanisms. OEMs negatively impact ovarian function by reducing the ovarian reserve, disrupting folliculogenesis, and altering the ovarian microenvironment through oxidative stress, inflammation, and fibrosis. Elevated reactive oxygen species (ROS) accelerate follicular atresia, and extracellular matrix remodeling contributes to ovarian damage, while immune dysregulation and cytokine imbalances further exacerbate the condition. The presence of OEMs does not significantly affect live birth rates in in vitro fertilization (IVF) treatments, despite potential reductions in the quality and quantity of oocytes. However, their surgical excision compromises the ovarian reserve. This review highlights the complex mechanisms by which OEMs impair ovarian function and emphasizes the need for further research to develop strategies that mitigate these effects, ultimately improving reproductive outcomes for women with endometriomas.

Effect of dietary patterns and nutritional supplementation in the management of endometriosis: a review

Endometriosis is an estrogen-dependent chronic inflammatory disease which causes dysmenorrhea, chronic pelvic pain, and infertility in women of childbearing age, significantly impacting their quality of life and physical and mental health. The etiology of endometriosis remains unclear, with oxidative stress and inflammation currently thought to play pivotal roles in its pathophysiology. Epidemiological studies and clinical trials indicate that varying dietary patterns and specific nutrient supplementation can influence oxidative stress markers and levels of inflammatory factors and related pathways, potentially impacting the progression of endometriosis. In this review, we summarize the roles of oxidative stress and inflammation in endometriosis and thoroughly examine the current understanding of the effect of dietary patterns and nutrient supplementation in treating endometriosis. This study suggests that nutrients may prevent the occurrence of endometriosis by modulating levels of inflammatory factors, regulating angiogenesis, and influencing the metabolism of estrogen pathways. The findings might provide new insights into the treatment of endometriosis patients and the potential benefits of dietary patterns and nutrient supplementation in patients with endometriosis.

Update on the pathogenesis of endometriosis-related infertility based on contemporary evidence

Endometriosis, the most prevalent cause of infertility, is associated with anatomical distortion leading to adhesions and fibrosis, as well as endocrine abnormalities and immune disorders. This review discusses the mechanisms underlying endometriosis-related infertility. Firstly, alterations in the hypothalamic-pituitary-ovarian axis lead to the secretion of gonadotropins and steroid hormones, with adverse effects on ovulation and implantation, leading to fertility decline. Secondly, dysregulation of the hypothalamic-pituitary-adrenal axis induces elevated serum cortisol and prolactin levels in patients with endometriosis, accounting for its regulation of stress, depression, and anxiety. Abnormal interactions between endometrial cells and the immune system change the local microenvironment, resulting in epithelial-mesenchymal transition and inflammation. Activated epithelial cells, stromal cells, and immunocytes produce various chemokines, cytokines, or autoantibodies, creating an unfavorable environment for embryo implantation. These findings suggest that alterations in the immune spectrum play a crucial role in endometriosis-related infertility. Thirdly, oxidative stress has adverse effects on the ovarian reserve and subsequent embryonic development, predicting another promising strategy for endometriosis-related infertility. An unbalanced redox state, including impaired mitochondrial function, dysregulated lipid metabolism, and iron-induced oxidative stress, generates a pro-oxidative microenvironment, which negatively impacts oocyte quality and sperm and embryo viability. Thus, an updated understanding of the mechanisms involved in this disease will help to develop effective strategies to manage endometriosis-related infertility.

β-elemene, a sesquiterpene constituent from Curcuma phaeocaulis inhibits the development of endometriosis by inducing ferroptosis via the MAPK and STAT3 signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

The rhizome of Curcuma phaeocaulis Valeton, Curcuma wenyujin Y.H. Chen & C. Ling, or Curcuma kwangsiensis S. G. Lee et C. F. Liang, commonly known as Wen-E-Zhu and E'zhu, has been utilized in traditional Chinese medicine for the treatment of cancer and gynecological diseases since antiquity. This traditional medicinal herb is highly esteemed for its efficacy in promoting blood circulation, dissolving blood stasis, reducing swelling, and alleviating pain. β-Elemene (β-ELE), a sesquiterpene compound derived from Curcuma phaeocaulis, has demonstrated potential in inhibiting tumor cell proliferation and inducing ferroptosis, which have been extensively studied in various malignant neoplasms. Previous studies have confirmed that Sparganium stoloniferum-Curcuma phaeocaulis containing β-ELE may possess anti-endometriotic properties. However, the exact mechanism underlying β-ELE's anti-endometriosis activity remains largely unknown and requires further research and investigation.

AIM OF THE STUDY

To identify the anti-endometriosis target of β-ELE and elucidate the underlying molecular mechanism of β-ELE in endometriosis, focusing on inducing ferroptosis.

MATERIALS AND METHODS

The target pathway of β-ELE in endometriosis treatment was predicted through network pharmacology and bioinformatics analysis. Surface plasmon resonance-high performance liquid chromatography-protein mass spectrometry (SPR-HPLC-MS) and molecular docking were used to further identify the potential targets of β-ELE in endometriosis. The immortalized endometriosis epithelial cell line 12Z was used for in vitro study. The effect of β-ELE on cell proliferation and migration was detected by CCK-8, EdU and wound healing assay, and ultrastructural changes were examined via transmission electron microscopy. The effect of β-ELE-induced ferroptosis was determined by western blot, immunohistochemistry staining and flow cytometry. SPR affinity analysis was performed to specific the direct interaction between β-ELE and FTH1, FTL, GPX4, STAT3 and MAPK14. To establish a mouse model of endometriosis and to assess the inhibitory effects of β-ELE and ELE injection on endometriosis in vivo as well as safety profile of administration, and investigate the effects and underlying mechanisms of β-ELE and ELE injection on ferroptosis in ectopic lesions.

RESULTS

SPR-HPLC-MS was employed to identify 76 potential targets of β-ELE for endometriosis treatment, closely linked to ferroptosis. Molecular docking revealed that glutathione peroxidase 4 (GPX4), ferritin heavy chain 1 (FTH1), ferritin light chain (FTL), signal transducer and activator of transcription 3 (STAT3), and mitogen-activated protein kinase 14 (MAPK14) are key action targets of β-ELE in endometriosis. Further investigations revealed that β-ELE inhibited the proliferation and migration of endometriotic cells in vitro while inducing ferroptosis, as evidenced by increased levels of iron, reactive oxygen species (ROS), and lipid peroxidation. In a mouse model, β-ELE inhibited the growth of endometriotic lesions, induced ferroptosis, suppressed fibrosis, and exhibited anti-endometriotic effects. Mechanistically, β-ELE downregulates the expression levels of GPX4, FTH1, and FTL and inhibited the phosphorylation of STAT3 and MAPK14, which may elucidate its underlying molecular mechanisms.

CONCLUSION

This study demonstrates that the inhibitory effect of β-ELE on endometriosis by inducing ferroptosis in vitro and in vivo. Our results revealed that β-ELE exerts anti-endometriosis effects by inducing ferroptosis via the MAPK and STAT3 signaling pathways.

Female reproductive disease, endometriosis: From inflammation to infertility

Despite the fact that endometriosis is a common gynecological disease that occurs in 10% of women of reproductive age, the pathogenesis and treatment strategy are not clear to date. Endometriosis patients are commonly characterized by adhesions in the pelvis or ovaries, which leads to prolonged inflammation in the abdominal cavity. To handle the chronic inflammation, changes of immune cells, including T cells, NK cells, and macrophage, are accompanied. Therefore, diverse cytokines and adhesions of the abdominal cavity lead to poor quality of ovarian follicles, inappropriate response to the hormone, and infertility. This review will guide researchers to summarize the molecular changes and identify new treatment strategies for endometriosis-mediated inflammation and pregnancy failure.

Dietary and Nutritional Interventions for the Management of Endometriosis

Endometriosis is a chronic, complex, systemic inflammatory condition that impacts approximately 190 million girls and women worldwide, significantly impacting their quality of life. The effective management of endometriosis requires a multi-disciplinary and holistic approach, one that includes surgical and medical management, such as a laparoscopy and a chronic medical management plan, as well as dietary, nutritional, and lifestyle adjunct interventions, such as pelvic pain physiotherapy and acupuncture. There is growing evidence to support the role of dietary and nutritional interventions in the adjunct management of endometriosis-related pain and gastrointestinal symptoms. However, the implementation of these interventions is often not regulated, as patients with endometriosis often adopt self-management strategies. Diet and nutrition can modulate key players integral to the pathophysiology of endometriosis, such as, but not limited to, inflammation, estrogen, and the microbiome. However, it is unclear as to whether diet plays a role in the prevention or the onset of endometriosis. In this review, we discuss three key players in the pathogenesis of endometriosis-inflammation, estrogen, and the microbiome-and we summarize how diet and nutrition can influence their mechanisms, and consequently, the progression and manifestation of endometriosis. There is a major need for evidence-based, non-invasive adjunct management of this debilitating disease, and diet and nutritional interventions may be suitable.

Rethinking the pathogenesis of endometriosis: Complex interactions of genomic, epigenetic, and environmental factors

AIM

Endometriosis is a complex, multifactorial disease. Recent advances in molecular biology underscore that somatic mutations within the epithelial component of the normal endometrium, alongside aberrant epigenetic alterations within endometrial stromal cells, may serve as stimulators for the proliferation of endometriotic tissue within the peritoneal cavity. Nevertheless, pivotal inquiries persist: the deterministic factors driving endometriosis development in certain women while sparing others, notwithstanding comparable experiences of retrograde menstruation. Within this review, we endeavor to synopsize the current understanding of diverse pathophysiologic mechanisms underlying the initiation and progression of endometriosis and delineate avenues for future research.

METHODS

A literature search without time restriction was conducted utilizing PubMed and Google Scholar.

RESULTS

Given that aberrant clonal expansion stemming from cancer-associated mutations is common in normal endometrial tissue, only endometrial cells harboring mutations imparting proliferative advantages may be selected for survival outside the uterus. Endometriotic cells capable of engendering metabolic plasticity and modulating mitochondrial dynamics, thereby orchestrating responses to hypoxia, oxidative stress, inflammation, hormonal stimuli, and immune surveillance, and adeptly acclimating to their harsh surroundings, stand a chance at viability.

CONCLUSION

The genesis of endometriosis appears to reflect the evolutionary principles of mutation, selection, clonal expansion, and adaptation to the environment.

Role of autophagy and ferroptosis in the development of endometriotic cysts (Review)

It is considered that the etiology of endometriosis is retrograde menstruation of endometrial tissue. Although shed endometrial cells are constantly exposed to a challenging environment with iron overload, oxidative stress and hypoxia, a few cells are able to survive and continue to proliferate and invade. Ferroptosis, an iron‑dependent form of non‑apoptotic cell death, is known to play a major role in the development and course of endometriosis. However, few papers have concentrated on the dynamic interaction between autophagy and ferroptosis throughout the progression of diseases. The present review summarized the current understanding of the mechanisms underlying autophagy and ferroptosis in endometriosis and discuss their role in disease development and progression. For the present narrative review electronic databases including PubMed and Google Scholar were searched for literature published up to the October 31, 2023. Autophagy and ferroptosis may be activated at early stages in endometriosis development. On the other hand, excessive activation of intrinsic pathways (e.g., estrogen and mechanistic target of rapamycin) may promote disease progression through autophagy inhibition. Furthermore, suppression of ferroptosis may cause further progression of endometriotic lesions. In conclusion, the autophagy and ferroptosis pathways may play a dual role in disease initiation and progression. The present review discussed the temporal transition of non‑apoptotic cell death regulation during disease progression from retrograde endometrium to early lesions to established lesions.

Assessment of the Ferroptosis Regulators: Glutathione Peroxidase 4, Acyl-Coenzyme A Synthetase Long-Chain Family Member 4, and Transferrin Receptor 1 in Patient-Derived Endometriosis Tissue

Ferroptosis, an iron-dependent form of non-apoptotic cell death, plays a pivotal role in various diseases and is gaining considerable attention in the realm of endometriosis. Considering the classical pathomechanism theories, we hypothesized that ferroptosis, potentially driven by increased iron content at ectopic sites, may contribute to the progression of endometriosis. This retrospective case-control study provides a comprehensive immunohistochemical assessment of the expression and tissue distribution of established ferroptosis markers: GPX4, ACSL4, and TfR1 in endometriosis patients. The case group consisted of 38 women with laparoscopically and histologically confirmed endometriosis and the control group consisted of 18 women with other gynecological conditions. Our study revealed a significant downregulation of GPX4 in stromal cells of endometriosis patients (M = 59.7% ± 42.4 versus 90.0% ± 17.5 in the control group, t (54) = -2.90, p = 0.005). This finding aligned with slightly, but not significantly, higher iron levels detected in the blood of endometriosis patients, using hemoglobin as an indirect predictor (Hb 12.8 (12.2-13.5) g/dL versus 12.5 (12.2-13.4) g/dL in the control group; t (54) = -0.897, p = 0.374). Interestingly, there was no concurrent upregulation of TfR1 (M = 0.7 ± 1.2 versus 0.2 ± 0.4 for EM, t (54) = 2.552, p = 0.014), responsible for iron uptake into cells. Our empirical findings provide support for the involvement of ferroptosis in the context of endometriosis. However, variances in expression patterns within stromal and epithelial cellular subsets call for further in-depth investigations.

Is retrograde menstruation a universal, recurrent, physiological phenomenon? A systematic review of the evidence in humans and non-human primates

STUDY QUESTION

What are the quantitative, qualitative, and temporal patterns of retrograde mentruation?

SUMMARY ANSWER

The extreme quantitative and qualitative heterogeneity of the available studies prevents the definitive conclusion that retrograde menstruation is a universal and consistent phenomenon during the reproductive period.

WHAT IS KNOWN ALREADY

Retrograde menstruation has been defined as a universal, physiological phenomenon that occurs similarly in about 90% of menstruators during the reproductive period. However, uncertainties still exist in terms of the event frequency, total amount, and cellular composition of retrograde menstruation and the differences between individuals with versus those without endometriosis.

STUDY DESIGN SIZE DURATION

Two systematic reviews were performed, one for human studies, and one for non-human primate studies. We retrieved studies from the PubMed and Embase databases published between 1 January 1980 and 1 November 2023. Studies published in the English language were included and identified using a combination of MeSH terms. References from relevant publications were systematically screened and further articles were identified using PubMed's 'similar articles' and 'cited by' functions.

PARTICIPANTS/MATERIALS SETTING METHODS

Results were reported in accordance with the PRISMA guidelines. Studies that did not report original data or provided a review of the field were excluded. Bias analysis was completed for each included human study by using the Newcastle-Ottawa scoring system.

MAIN RESULTS AND THE ROLE OF CHANCE

Fifteen studies were finally included in the human systematic review, mostly with limited sample sizes. The macroscopic visualization of blood in PF during menses was reported with a frequency ranging from 9% to 100%. A prevalence of endometrial cells detected in peritoneal fluid ranging from 8% to 75% was reported in the various studies. Controversial findings were reported in relation to patients with endometriosis. Retrograde menstruation has been evaluated cross-sectionally on single occasions, and no information is available on the course of the phenomenon within an entire cycle and between subsequent cycles. Two studies were included in the non-human primate systematic review; one of them showed that retrograde menstruation was observed more frequently in baboons with naturally occurring endometriosis (83%) than in those with a normal pelvis (51%).

LIMITATIONS REASONS FOR CAUTION

In humans, peritoneal fluid has often been collected at different cycle phases and not systematically during menstruation. The indication for laparoscopy was not always clear for all participants. A wide variety of methods were used to detect endometrial cells, including cytological staining, cell block analysis, immunocytochemistry, and various methods of cell culture.

WIDER IMPLICATION OF THE FINDINGS

The idea that almost all women experience retrograde menstruation regularly and similarly during their reproductive life is currently unsubstantiated. It is an academic notion accepted uncritically. Development of endometriosis may derive from differences in the frequency or severity of the event.

STUDY FUNDING/COMPETING INTERESTS

The review was partially funded by Italian Ministry of Health-Current Research IRCCS. P.Vi. serves as co-editor in Chief of Journal of Endometriosis and Uterine Disorders. E.S. serves as Editor in Chief of Human Reproduction Open and discloses research grants from Ferring, Ibsa, Gedeon Richter, and Theramex, and honoraria from Ibsa and Gedeon Richter. P.Ve. serves as Associate Editor for Human Reproduction Open; is a member of the Editorial Board of the Journal of Obstetrics and Gynaecology Canada, of the Italian Journal of Obstetrics and Gynaecology, and of the International Editorial Board of Acta Obstetricia et Gynecologica Scandinavica; has received royalties from Wolters Kluwer for chapters on endometriosis management in the clinical decision support resource UpToDate; and maintains both a public and private gynecological practice. All other authors declare they have no conflict of interest.

REGISTRATION NUMBER

N/A.

Oxidative Stress and the Nrf2/PPARγ Axis in the Endometrium: Insights into Female Fertility

Successful pregnancy depends on precise molecular regulation of uterine physiology, especially during the menstrual cycle. Deregulated oxidative stress (OS), often influenced by inflammatory changes but also by environmental factors, represents a constant threat to this delicate balance. Oxidative stress induces a reciprocally regulated nuclear factor erythroid 2-related factor 2/peroxisome proliferator-activated receptor-gamma (Nrf2/PPARγ) pathway. However, increased PPARγ activity appears to be a double-edged sword in endometrial physiology. Activated PPARγ attenuates inflammation and attenuates OS to restore redox homeostasis. However, it also interferes with physiological processes during the menstrual cycle, such as hormonal signaling and angiogenesis. This review provides an elucidation of the molecular mechanisms that support the interplay between PPARγ and OS. Additionally, it offers fresh perspectives on the Nrf2/PPARγ pathway concerning endometrial receptivity and its potential implications for infertility.

Development of deep pelvic endometriosis following acute haemoperitoneum: a prospective ultrasound study

STUDY QUESTION

Is acute haemoperitoneum that is managed conservatively a precursor of deep endometriosis?

SUMMARY ANSWER

Our study provides evidence to suggest that acute haemoperitoneum may lead to the development of deep endometriosis in a significant proportion of cases.

WHAT IS KNOWN ALREADY

A recent pilot study was the first to suggest that acute haemoperitoneum could be a precursor of deep endometriosis. However, the sample size was small, and the follow-up was not standardized owing to unknown rates of clot absorption and development of endometriosis.

STUDY DESIGN SIZE DURATION

This was a prospective observational cohort study conducted at a single centre over a 31-month period. A required sample size of 30 was calculated using results from a previous study, with a minimum of 15 women each in the groups with and without significant haemoperitoneum (study and control groups, respectively). A total of 59 women were recruited to the study and eight were lost to follow-up. The final sample comprised 51 women, 15 in the study group and 36 in the control group.

PARTICIPANTS/MATERIALS SETTING METHODS

All non-pregnant, premenopausal women aged 18-50 years who consecutively presented to our dedicated gynaecological diagnostic unit with severe acute lower abdominal pain were eligible for this study. We only included women who were clinically stable and were suitable for conservative management. Those with prior history or evidence of endometriosis on their initial ultrasound scan, previous hysterectomy, or bilateral oophorectomy were excluded. Participants had standardized follow-up visits for 6 months, with pelvic ultrasound scans and the British Society of Gynaecological Endoscopy pelvic pain questionnaires completed at each visit. The primary outcome was the sonographically confirmed presence of newly formed endometriosis. Secondary outcomes were the presence and change of pelvic pain symptoms and health-related quality of life (HR-QOL).

MAIN RESULTS AND THE ROLE OF CHANCE

After completion of follow-up, 7/15 (47%; 95% CI 21.3-71.4%) women presenting with acute haemoperitoneum (study group) developed sonographic evidence of deep endometriosis, compared to 0/36 (0%; 97.5% CI 0.0-9.7%) women in the control group. A ruptured functional haemorrhagic cyst was the most common cause of haemoperitoneum, occurring in 13/15 cases (87%). The time from the initial event to sonographic evidence of endometriosis varied from 2 to 6 months. The EuroQol visual analogue scores were not significantly different at baseline between the groups that developed and did not develop endometriosis [28 (interquartile range (IQR) 15-40, n = 6) vs 56 (IQR 35-75, n = 44), P = 0.09], while the EuroQol-5D values were lower in the endometriosis group [-0.01 (IQR -0.07 to 0.19, n = 6) vs 0.62 (IQR 0.24-0.73, n = 44), P = 0.002]. At 6 months, the EuroQol-5D scores were improved in both groups, but remained significantly lower in the endometriosis group compared to the no endometriosis group [0.69 (IQR 0.66-0.80, n = 6) vs 0.85 (IQR 0.76-1.00, n = 44), P = 0.03]. There was no clinically relevant difference in the pelvic pain scores at either time point.

LIMITATIONS REASONS FOR CAUTION

It remains uncertain whether minimal, superficial endometriosis existed at commencement of the study and had a role in the development of deep endometriosis. Although the ultrasound findings were in keeping with deep endometriosis, this was not confirmed histologically. The pelvic pain and HR-QOL findings could have been influenced by the baseline scores being taken when the patient was admitted with acute pain. Also, the sample size was too small to draw reliable conclusions regarding the impact of newly developed endometriosis on QoL.

WIDER IMPLICATIONS OF THE FINDINGS

Our study provides further evidence showing that significant haemoperitoneum may be a precursor of deep endometriosis. Haemodynamically stable women presenting with acute pelvic pain and significant haemoperitoneum should be counselled about the risk of developing deep endometriosis. Interventional studies should be carried out in the future to see whether laparoscopy and pelvic washout could prevent development of deep endometriosis. Preventative strategies, including treatment to suppress ovulation and formation of functional cysts, should be further investigated. This includes the combined and progesterone-only contraceptive pills. Larger future studies are also required to assess women over a longer period of time, with adjustment for confounding factors, to evaluate a possible effect on HR-QOL and pain symptoms.

STUDY FUNDING/COMPETING INTERESTS

Funding was obtained from The Gynaecology Ultrasound Centre, London, UK. TT received personal fees from GE, Samsung, Medtronic, and Merck for lectures on ultrasound. TT also received a postdoctoral grant from the South-Eastern Norwegian Health Authority (grant number 2020083).

TRIAL REGISTRATION NUMBER

researchregistry6472.

Saliva, a molecular reflection of the human body? Implications for diagnosis and treatment

For many diseases, and cancer in particular, early diagnosis allows a wider range of therapies and a better disease management. This has led to improvements in diagnostic procedures, most often based on tissue biopsies or blood samples. Other biological fluids have been used to diagnose disease, and among them saliva offers a number of advantages because it can be collected non-invasively from large populations at relatively low cost. To what extent might saliva content reveal the presence of a tumour located at a distance from the oral cavity and the molecular information obtained from saliva be used to establish a diagnosis are current questions. This review focuses primarily on the content of saliva and shows how it potentially offers a source of diagnosis, possibly at an early stage, for pathologies such as cancers or endometriosis.

The role of regulatory T-cells in the development of endometriosis

Endometriosis is a benign disease of the female reproductive tract, characterized by the process of chronic inflammation and alterations in immune response. It is estimated to affect 2-19% of women in the general population and is commonly associated with symptoms of chronic pelvic pain and infertility. Regulatory T cells (Treg) are a subpopulation of T lymphocytes that are potent suppressors of inflammatory immune response, essential in preventing destructive immunity in all tissues. In endometriosis, several studies have investigated the possible role of Treg cells in the development of the disease. Most studies to date are heterogeneous in methodology and are based on a small number of cases, which means that it is impossible to define their exact role at present. Based on current knowledge, it seems that disturbed Treg homeostasis, leading to increased systemic and local inflammation within ectopic and eutopic endometrium, is present in women who eventually develop endometriosis. It is also evident that different subsets of human Treg cells have different roles in suppressing the immune response. Recent studies in patients with endometriosis have investigated naive/resting FOXP3lowCD45RA+ Treg cells, which upon T cell receptor stimulation, differentiate into activated/effector FOXP3highCD45RA- Treg cells, characterized by a strong immunosuppressive activity. In addition, critical factors controlling expression of Treg/effector genes, including reactive oxygen species and heme-responsive master transcription factor BACH2, were found to be upregulated in endometriotic lesions. As shown recently for cancer microenvironments, microbial inflammation may also contribute to the local composition of FOXP3+ subpopulations in endometriotic lesions. Furthermore, cytokines, such as IL-7, which control the homeostasis of Treg subsets through the tyrosine phosphorylation STAT5 signalling pathway, have also been shown to be dysregulated. To better understand the role of Treg in the development of endometriosis, future studies should use clear definitions of Tregs along with specific characterization of the non-Treg (FOXP3lowCD45RA-) fraction, which itself is a mixture of follicular Tregs and cells producing inflammatory cytokines.

Immune Dysregulation in Endometriomas: Implications for Inflammation

The most common manifestation of endometriosis, a condition characterized by the presence of endometrial-like tissue outside of the uterus, is the endometrioma, a cystic ovarian lesion. It is a commonly occurring condition associated with chronic pelvic pain exacerbated prior to and during menstruation, as well as infertility. The exact pathomechanisms of the endometrioma are still not fully understood. Emerging evidence suggests a pivotal role of immune dysregulation in the pathogenesis of endometriomas, primarily influencing both local and systemic inflammatory processes. Among the factors implicated in the creation of the inflammatory milieu associated with endometriomas, alterations in both serum and local levels of several cytokines stand out, including IL-6, IL-8, and IL-1β, along with abnormalities in the innate immune system. While numerous signaling pathways have been suggested to play a role in the inflammatory process linked to endometriomas, only NF-κB has been conclusively demonstrated to be involved. Additionally, increased oxidative stress, both resulting from and contributing to endometriomas, has been identified as a primary driver of both systemic and local inflammation associated with the condition. This article reviews the current understanding of immune dysfunctions in the endometrioma and their implications for inflammation.

Combined delta neutrophil index and red blood cell distribution width as a new biomarker to predict endometriosis

Objective

The aim of this study was to evaluate the use of delta neutrophil index (DNI) in predicting endometriosis.

Material and Methods

A retrospective, case-control study was performed in a tertiary care center. DNI, red cell distribution width (RDW), and other blood parameters obtained from complete blood counts of 267 patients, consisting of 122 (45.7%) endometriosis patients with proven pathology reports of stages 3-4, and a control group of 145 women who underwent laparoscopy for simple ovarian cyst and/or diagnostic purposes and had normal histopathology, were compared. Receiver operating characteristic and logistic regression analyses were performed.

Results

DNI and RDW were significantly higher in endometriosis patients than in the control group (p=0.034 and p=0.003, respectively). Other parameters obtained from complete blood counts (leukocyte, neutrophil, lymphocyte, monocytes, and platelet counts and neutrophil-to-lymphocyte ratio), did not differ (p>0.05). For DNI, at a cut-off value of 0.025, area under the curve (AUC) was 0.572 and it was statistically significant [p=0.042; 95% confidence interval (CI): 0.503-0.642, sensitivity: 45.9%, specificity: 67.6%, Youden’s index: 0.135]. For RDW, AUC: 0.601 for cut-off value of 13.65 was statistically significant (p=0.004, 95% CI: 0.553-0.669, sensitivity: 50.8%, specificity: 67.6%, Youden’s index: 0.184). The logistic regression model established with the combined marker obtained by multiplying the DNI and RDW was statistically significant (p<0.001, Nagelkerke R2=0.72, 95% CI: 2.58-47.26, B: 2.40, negative predictive value: 78.6%, positive predictive value: 37.7%).

Conclusion

DNI, a new inflammatory marker, and RDW, known to be associated with inflammation, may be useful minimally invasive biomarkers of endometriosis.

Spotlight on iron overload and ferroptosis: Research progress in female infertility

Iron is an essential trace element for organisms. However, iron overload, which is common in haematological disorders (e.g. haemochromatosis, myelodysplastic syndromes, aplastic anaemia, and thalassaemia, blood transfusion-dependent or not), can promote reactive oxygen species generation and induce ferroptosis, a novel form of programmed cell death characterised by excess iron and lipid peroxidation, thus causing cell and tissue damage. Infertility is a global health concern. Recent evidence has indicated the emerging role of iron overload and ferroptosis in female infertility by inducing hypogonadism, causing ovary dysfunction, impairing preimplantation embryos, attenuating endometrial receptivity, and crosstalk between subfertility-related disorders, such as polycystic ovary syndrome and endometriosis. In addition, gut microbiota and their metabolites are involved in iron metabolism, ferroptosis, and female infertility. In this review, we systematically elaborate on the current research progress in female infertility with a novel focus on iron overload and ferroptosis and summarise promising therapies targeting iron overload and ferroptosis to recover fertility in women. In summary, our study provides new insights into female infertility and offers literature references for the clinical management of female infertility associated with iron overload and ferroptosis, which may be beneficial for females with haematopoietic disorders suffering from both iron overload and infertility.

Impaired bone morphogenetic protein (BMP) signaling pathways disrupt decidualization in endometriosis

Endometriosis is linked to increased infertility and pregnancy complications due to defective endometrial decidualization. We hypothesized that identification of altered signaling pathways during decidualization could identify the underlying cause of infertility and pregnancy complications. Our study reveals that transforming growth factor β (TGFβ) pathways are impaired in the endometrium of individuals with endometriosis, leading to defective decidualization. Through detailed transcriptomic analyses, we discovered abnormalities in TGFβ signaling pathways and key regulators, such as SMAD4, in the endometrium of affected individuals. We also observed compromised activity of bone morphogenetic proteins (BMP), a subset of the TGFβ family, that control endometrial receptivity. Using 3-dimensional models of endometrial stromal and epithelial assembloids, we showed that exogenous BMP2 improved decidual marker expression in individuals with endometriosis. Our findings reveal dysfunction of BMP/SMAD signaling in the endometrium of individuals with endometriosis, explaining decidualization defects and subsequent pregnancy complications in these individuals.

Regulated Cell Death in Endometriosis

Regulated cell death (RCD) represents a distinct mode of cell demise, differing from accidental cell death (ACD), characterized by specific signaling cascades orchestrated by diverse biomolecules. The regular process of cell death plays a crucial role in upholding internal homeostasis, acting as a safeguard against biological or chemical damage. Nonetheless, specific programmed cell deaths have the potential to activate an immune-inflammatory response, potentially contributing to diseases by enlisting immune cells and releasing pro-inflammatory factors. Endometriosis, a prevalent gynecological ailment, remains incompletely understood despite substantial progress in unraveling associated signaling pathways. Its complexity is intricately tied to the dysregulation of inflammatory immune responses, with various RCD processes such as apoptosis, autophagic cell death, pyroptosis, and ferroptosis implicated in its development. Notably, limited research explores the association between endometriosis and specific RCD pathways like pyroptosis and cuproptosis. The exploration of regulated cell death in the context of endometriosis holds tremendous potential for further advancements. This article thoroughly reviews the molecular mechanisms governed by regulated cell death and their implications for endometriosis. A comprehensive understanding of the regulated cell death mechanism in endometriosis has the potential to catalyze the development of promising therapeutic strategies and chart the course for future research directions in the field.

Proposal for targeted, neo-evolutionary-oriented, secondary prevention of early-onset endometriosis and adenomyosis. Part I: pathogenic aspects

The potential for repeated ovulation and menstruation is thought to have provided a Darwinian advantage during the Palaeolithic. Reproductive conditions remained relatively stable until the pre-industrial era, characterized by late menarche, very young age at first birth, multiple pregnancies, and prolonged periods of lactational amenorrhoea. For hundreds of thousands of years, menstruators experienced few ovulatory cycles, even though they were genetically adapted to ovulate and menstruate every month. In the post-industrial era, the age at menarche gradually declined, the age at first birth progressively increased, and breastfeeding became optional and often of short duration. This created a mismatch between genetic adaptation and socio-environmental evolution, so that what was initially a probable reproductive advantage subsequently contributed to increased susceptibility to diseases associated with lifetime oestrogen exposure, such as ovarian, endometrial and breast cancer and, hypothetically, also those associated with the number of ovulatory menstruations, such as endometriosis and adenomyosis. The incidence of endometriosis shows a steep and progressive increase around the age of 25 years, but given the consistently reported delay in diagnosis, the actual incidence curve should be shifted to the left, supporting the possibility that the disease has its roots in adolescence. This raises the question of whether, from an evolutionary point of view, anovulation and amenorrhoea should not still be considered the physiological state, especially in the postmenarchal period. However, an increase in the frequency of endometriosis in recent decades has not been demonstrated, although this deserves further epidemiological investigation. In addition, as endometriosis occurs in a minority of individuals exposed to retrograde menstruation, other important pathogenic factors should be scrutinised. Research should be resumed to explore in more detail the transtubal reflux of not only blood, but also endometrial cells, and whether they are systematically present in the peritoneal fluid after menstruation. If repetitive ovulatory menstruation during the early reproductive years is shown to increase the risk of endometriosis and adenomyosis development and progression in susceptible individuals, hormonal interventions could be used as secondary prevention in symptomatic adolescents.

Proposal for targeted, neo-evolutionary-oriented secondary prevention of early-onset endometriosis and adenomyosis. Part II: medical interventions

According to consistent epidemiological data, the slope of the incidence curve of endometriosis rises rapidly and sharply around the age of 25 years. The delay in diagnosis is generally reported to be between 5 and 8 years in adult women, but it appears to be over 10 years in adolescents. If this is true, the actual onset of endometriosis in many young women would be chronologically placed in the early postmenarchal years. Ovulation and menstruation are inflammatory events that, when occurring repeatedly for years, may theoretically favour the early development of endometriosis and adenomyosis. Moreover, repeated acute dysmenorrhoea episodes after menarche may not only be an indicator of ensuing endometriosis or adenomyosis, but may also promote the transition from acute to chronic pelvic pain through central sensitization mechanisms, as well as the onset of chronic overlapping pain conditions. Therefore, secondary prevention aimed at reducing suffering, limiting lesion progression, and preserving future reproductive potential should be focused on the age group that could benefit most from the intervention, i.e. severely symptomatic adolescents. Early-onset endometriosis and adenomyosis should be promptly suspected even when physical and ultrasound findings are negative, and long-term ovulatory suppression may be established until conception seeking. As nowadays this could mean using hormonal therapies for several years, drug safety evaluation is crucial. In adolescents without recognized major contraindications to oestrogens, the use of very low-dose combined oral contraceptives is associated with a marginal increase in the individual absolute risk of thromboembolic events. Oral contraceptives containing oestradiol instead of ethinyl oestradiol may further limit such risk. Oral, subcutaneous, and intramuscular progestogens do not increase the thromboembolic risk, but may interfere with attainment of peak bone mass in young women. Levonorgestrel-releasing intra-uterine devices may be a safe alternative for adolescents, as amenorrhoea is frequently induced without suppression of the ovarian activity. With regard to oncological risk, the net effect of long-term oestrogen-progestogen combinations use is a small reduction in overall cancer risk. Whether surgery should be considered the first-line approach in young women with chronic pelvic pain symptoms seems questionable. Especially when large endometriomas or infiltrating lesions are not detected at pelvic imaging, laparoscopy should be reserved to adolescents who refuse hormonal treatments or in whom first-line medications are not effective, not tolerated, or contraindicated. Diagnostic and therapeutic algorithms, including self-reported outcome measures, for young individuals with a clinical suspicion of early-onset endometriosis or adenomyosis are proposed.

ITRAQ-based proteomics analysis of human ectopic endometrial stromal cells treated by Maqian essential oil

BACKGROUND

Endometriosis is a common and complex syndrome characterized by the presence of endometrial-like tissue outside the uterus. Chinese medicine has been recently found to show good efficacy in treating endometriosis. Our previous results revealed that Maqian fruit essential oil (MQEO) could inhibit the proliferation and induce apoptosis of ectopic endometrial stromal cells (EESCs), but the mechanisms remain unclear. In this study, we aim to explore the molecular mechanism of MQEO's specific effects in EESCs.

METHODS

We conducted a quantitative proteomics analysis by iTRAQ on EESCs treated with MQEO or DMSO. Then deep analysis was performed based on differentially expressed proteins, including Gene Ontology enrichment analysis, pathway enrichment analysis and protein interaction analysis. Candidate protein targets were subsequently verified by western blotting.

RESULTS

Among 6575 identified proteins, 435 proteins exhibited altered expression levels in MQEO-treated EESCs. Of these proteins, most were distributed in signal transduction as well as immune system and the most significantly altered pathway was complement and coagulation cascades. Moreover, two differentially expressed proteins (Heme oxygenase 1 and Acyl-CoA 6-desaturase) were verified and they can be potential biomarkers for endometriosis treatment.

CONCLUSIONS

Our proteomic analysis revealed distinct protein expression patterns induced by MQEO treatment in EESCs, highlighting the potential of MQEO for endometriosis treatment and biomarker discovery.

Impaired bone morphogenetic protein (BMP) signaling pathways disrupt decidualization in endometriosis

Endometriosis is linked to increased infertility and pregnancy complications due to defective endometrial decidualization. We hypothesized that identification of altered signaling pathways during decidualization could identify the underlying cause of infertility and pregnancy complications. Our study reveals that transforming growth factor β (TGFβ) pathways are impaired in the endometrium of individuals with endometriosis, leading to defective decidualization. Through detailed transcriptomic analyses, we discovered abnormalities in TGFβ signaling pathways and key regulators, such as SMAD4, in the endometrium of affected individuals. We also observed compromised activity of bone morphogenetic proteins (BMP), a subset of the TGFβ family, that control endometrial receptivity. Using 3-dimensional models of endometrial stromal and epithelial assembloids, we showed that exogenous BMP2 improved decidual marker expression in individuals with endometriosis. Our findings unveil a previously unidentified dysfunction in BMP/SMAD signaling in the endometrium of individuals with endometriosis, explaining decidualization defects and subsequent pregnancy complications in these individuals.

Impaired bone morphogenetic protein signaling pathways disrupt decidualization in endometriosis

It is hypothesized that impaired endometrial decidualization contributes to decreased fertility in individuals with endometriosis. To identify the molecular defects that underpin defective decidualization in endometriosis, we subjected endometrial stromal cells from individuals with or without endometriosis to time course in vitro decidualization with estradiol, progesterone, and 8-bromo-cyclic-AMP (EPC) for 2, 4, 6, or 8 days. Transcriptomic profiling identified differences in key pathways between the two groups, including defective bone morphogenetic protein (BMP)/SMAD4 signaling (ID2, ID3, FST), oxidate stress response (NFE2L2, ALOX15, SLC40A1), and retinoic acid signaling pathways (RARRES, RARB, ALDH1B1). Genome-wide binding analyses identified an altered genomic distribution of SMAD4 and H3K27Ac in the decidualized stromal cells from individuals without endometriosis relative to those with endometriosis, with target genes enriched in pathways related to signaling by transforming growth factor β (TGFβ), neurotrophic tyrosine kinase receptors (NTRK), and nerve growth factor (NGF)-stimulated transcription. We found that direct SMAD1/5/4 target genes control FOXO, PI3K/AKT, and progesterone-mediated signaling in decidualizing cells and that BMP2 supplementation in endometriosis patient-derived assembloids elevated the expression of decidualization markers. In summary, transcriptomic and genome-wide binding analyses of patient-derived endometrial cells and assembloids identified that a functional BMP/SMAD1/5/4 signaling program is crucial for engaging decidualization.