Basolateral secretions of human endometrial epithelial organoids impact stromal cell decidualization

Deciphering endometrial dysfunction in patients with uterine myoma using endometrial organoids: a pilot study

RESEARCH QUESTION

What influence does an intramural myoma have on the endometrium, and how is this mediated?

DESIGN

Endometrium was collected from 13 patients with non-cavity-distorting intramural myomas (diameter ≤4 cm; International Federation of Gynecology and Obstetrics type 4) and 13 patients without myomas undergoing hysterectomy for benign cervical diseases with a similar clinical baseline. Endometrial organoids were established in vitro and induced to reach the secretory phase by oestrogen and progesterone. Transcriptome sequencing was conducted on endometrial organoids in both untreated and secretory stages from three individuals with myomas and three control participants. Immunofluorescence and real-time quantitative PCR (RT-qPCR) were performed on endometrial organoids from another 10 myoma patients and 10 control patients for validation.

RESULTS

The data revealed abnormally increased hormone receptor (PGR) levels in the untreated endometrial organoids with myomas, resulting in potentially abnormal glandular and vascular development. The aberrant responses to oestrogen and progestogen prompted further investigation into the secretory phase. The secretory endometrial organoids with myomas exhibited greater changes in acetyl-α-tubulin, ODF2 and TPPP, demonstrating likely decreased cilia, and COL6A1, used as a marker for increased extracellular matrix (ECM) modelling. Both untreated and secretory endometrial organoids with myoma showed an up-regulation of genes and pathways related to ECM mechanotransduction. The expression pattern of receptivity-related genes was disturbed in endometrial organoids with myoma.

CONCLUSIONS

This study is the first to reveal that intramural myomas create an abnormal hormonal and mechanical environment in the untreated and secretory endometrial organoids. The intramural myomas negatively impacted gene expression relating to endometrial glands, blood vessels, cilia and ECM, indicating that intramural myomas impair endometrial decidualization and receptivity.

Acyl-CoA long-chain synthetase 1 (ACSL1) protects the endometrium from excess palmitic acid stress during decidualization

Endometrial receptivity relies on the functional and morphological change of endometrium stromal cells (EnSCs) and epithelial cells in the secretory phase. Decidualization of ESCs and transitions in endometrium epithelial cells are crucial for successful uterine implantation and maintaining pregnancy. Accumulated data have demonstrated that decidualization is tightly coordinated by lipid metabolism. However, the lipidomic change and regulatory mechanism in uterine decidualization are still unknown. Our study showed that endometrium stromal cells and decidual stromal cells had different lipidomic profiles. Acyl-CoA long-chain synthetase 1 (ACSL1) which converts fatty acids to acyl-CoA expression was strongly elevated during decidualization. ACSL1 knockdown inhibited stromal-to-decidual cell transition and decreased the decidualization markers prolactin and Insulin-like growth factor-binding protein-1 (IGFBP1) expression through the AKT pathway. Lipid uptake was upregulated in stromal cells while lipid droplet accumulation was downregulated during decidualization. Meanwhile, silencing of ACSL1 led to impaired spare respiratory capacity, and downregulation of TFAM expression, indicating robust lipid metabolism. While palmitic acid addition impeded decidualization, overexpression of ACSL1 could partially reverse its effect. ACSL inhibitor Triacsin C significantly impeded decidualization in a three-dimensional coculture model consisting of endometrial stromal cells and epithelial cells. Knockdown of ACSL1 in stromal cells decreased the expression of the decidualization markers PAEP and SPP1 in epithelial cells. Collectively, ACSL1 is essential for uterine decidualization and protects stromal cells from excess palmitic acid stress.

Tryptophan regulates the expression of IGFBP1 in bovine endometrial epithelial cells in vitro via the TDO2-AHR pathway

BACKGROUND

This study aimed to identify the roles of L-tryptophan (Trp) and its rate-limiting enzymes on the receptivity of bovine endometrial epithelial cells. Real-time PCR was conducted to analyze the differential expression of genes between different groups of bovine endometrial epithelial cells. Western blot was performed to detect Cyclooxygenase-2 (COX2) expression after treatment with Trp or kynurenine (the main metabolites of Trp). The kynurenine assay was used to examine if Trp or prostaglandin E2 (PGE2) can increase the production of kynurenine in the bovine endometrial epithelial cells.

RESULTS

Trp significantly stimulates insulin growth factor binding protein 1 (IGFBP1) expression, a common endometrial marker of conceptus elongation and uterus receptivity for ruminants. When bovine endometrial epithelial cells are treated with Trp, tryptophan hydroxylase-1 remains unchanged, but tryptophan 2,3-dioxygenase 2 (TDO2) is significantly increased, suggesting tryptophan is mainly metabolized through the kynurenine pathway. Kynurenine significantly stimulates IGFBP1 expression. Furthermore, Trp and kynurenine significantly increase the expression of aryl hydrocarbon receptor (AHR). CH223191, an AHR inhibitor, abrogates the induction of Trp and kynurenine on IGFBP1. PGE2 significantly induces the expression of TDO2, AHR, and IGFBP1.

CONCLUSIONS

The regulation between Trp / kynurenine and PGE2 may be crucial for the receptivity of the bovine uterus.

Stanniocalcin Protein Expression in Female Reproductive Organs: Literature Review and Public Cancer Database Analysis

Stanniocalcin (STC) 1 and 2 serve as antihyperglycemic polypeptide hormones with critical roles in regulating calcium and phosphate homeostasis. They additionally function as paracrine and/or autocrine factors involved in numerous physiological processes, including female reproduction. STC1 and STC2 contribute to the pathophysiology of several diseases, including female infertility- and pregnancy-associated conditions, and even tumorigenesis of reproductive organs. This comprehensive review highlights the dynamic expression patterns and potential dysregulation of STC1 and STC2, restricted to female fertility, and infertility- and pregnancy-associated diseases and conditions, such as endometriosis, polycystic ovary syndrome (PCOS), abnormal uterine bleeding, uterine polyps, and pregnancy complications, like impaired decidualization, preeclampsia, and preterm labor. Furthermore, the review elucidates the role of dysregulated STC in the progression of cancers of the reproductive system, including endometrial, cervical, and ovarian cancers. Additionally, the review evaluates the expression patterns and prognostic significance of STC in gynecological cancers by utilizing existing public datasets from The Cancer Genome Atlas to help decipher the multifaceted roles of these pleiotropic hormones in disease progression. Understanding the intricate mechanisms by which STC proteins influence all these reviewed conditions could lead to the development of targeted diagnostic and therapeutic strategies in the context of female reproductive health and oncology.

Bioengineering approaches for the endometrial research and application

The endometrium undergoes a series of precise monthly changes under the regulation of dynamic levels of ovarian hormones that are characterized by repeated shedding and subsequent regeneration without scarring. This provides the potential for wound healing during endometrial injuries. Bioengineering materials highlight the faithful replication of constitutive cells and the extracellular matrix that simulates the physical and biomechanical properties of the endometrium to a larger extent. Significant progress has been made in this field, and functional endometrial tissue bioengineering allows an in-depth investigation of regulatory factors for endometrial and myometrial defects in vitro and provides highly therapeutic methods to alleviate obstetric and gynecological complications. However, much remains to be learned about the latest progress in the application of bioengineering technologies to the human endometrium. Here, we summarize the existing developments in biomaterials and bioengineering models for endometrial regeneration and improving the female reproductive potential.

Cellular heterogeneity and dynamics of the human uterus in healthy premenopausal women

The human uterus is a complex and dynamic organ whose lining grows, remodels, and regenerates in every menstrual cycle or upon tissue damage. Here we applied single-cell RNA sequencing to profile more the 50,000 uterine cells from both the endometrium and myometrium of 5 healthy premenopausal individuals, and jointly analyzed the data with a previously published dataset from 15 subjects. The resulting normal uterus cell atlas contains more than 167K cells representing the lymphatic endothelium, blood endothelium, stromal, ciliated epithelium, unciliated epithelium, and immune cell populations. Focused analyses within each major cell type and comparisons with subtype labels from prior studies allowed us to document supporting evidence, resolve naming conflicts, and to propose a consensus annotation system of 39 subtypes. We release their gene expression centroids, differentially expressed genes, and mRNA patterns of literature-based markers as a shared community resource. We find many subtypes show dynamic changes over different phases of the cycle and identify multiple potential progenitor cells: compartment-wide progenitors for each major cell type, transitional cells that are upstream of other subtypes, and potential cross-lineage multipotent stromal progenitors that may be capable of replenishing the epithelial, stromal, and endothelial compartments. When compared to the healthy premenopausal samples, a postpartum and a postmenopausal uterus sample revealed substantially altered tissue composition, involving the rise or fall of stromal, endothelial, and immune cells. The cell taxonomy and molecular markers we report here are expected to inform studies of both basic biology of uterine function and its disorders.

SIGNIFICANCE

We present single-cell RNA sequencing data from seven individuals (five healthy pre-menopausal women, one post-menopausal woman, and one postpartum) and perform an integrated analysis of this data alongside 15 previously published scRNA-seq datasets. We identified 39 distinct cell subtypes across four major cell types in the uterus. By using RNA velocity analysis and centroid-centroid comparisons we identify multiple computationally predicted progenitor populations for each of the major cell compartments, as well as potential cross-compartment, multi-potent progenitors. While the function and interactions of these cell populations remain to be validated through future experiments, the markers and their "dual characteristics" that we describe will serve as a rich resource to the scientific community. Importantly, we address a significant challenge in the field: reconciling multiple uterine cell taxonomies being proposed. To achieve this, we focused on integrating historical and contemporary knowledge across multiple studies. By providing detailed evidence used for cell classification we lay the groundwork for establishing a stable, consensus cell atlas of the human uterus.

Polycystic ovary syndrome and adverse pregnancy outcomes: potential role of decidual function

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting fertility and mental health among women of reproductive age. In addition to anovulation and hyperandrogenism, patients also experience metabolic issues, such as insulin resistance, obesity, and dyslipidemia, as well as chronic low-grade inflammation throughout the body. Recent studies have shown that even with assisted reproductive technology to treat anovulatory issues, patients with PCOS still have higher rates of adverse pregnancy outcomes and abortion compared to normal pregnancies. These findings suggest that PCOS may impair the endometrium and disrupt the onset and maintenance of healthy pregnancies. Decidualization is a crucial step in the process of healthy pregnancy, during which endometrial stromal cells (ESCs) differentiate into secretory decidual stromal cells (DSCs) regulated by hormones and local metabolism. This article comprehensively reviews the pathological processes of PCOS and the mechanisms involved in its impaired decidualization. In addition, we explore how PCOS increases the incidence of adverse pregnancy outcomes (APO). By gaining a better understanding of the adverse effects of PCOS on pregnancy and its specific mechanisms, we hope to provide a theoretical basis for reducing APO and improving the live birth rate among women with PCOS.

Development of Polarity-Reversed Endometrial Epithelial Organoids

The uterine epithelium is composed of a single layer of hormone responsive polarized epithelial cells that line the lumen and form tubular glands. Endometrial epithelial organoids (EEO) can be generated from uterine epithelia and recapitulate cell composition and hormone responses in vitro. As such, the development of EEO represents a major advance for facilitating mechanistic studies in vitro. However, a major limitation for the use of EEO cultured in basement membrane extract and other hydrogels is the inner location of apical membrane, thereby hindering direct access to the apical surface of the epithelium to study interactions with the embryo or infectious agents such as viruses and bacteria. Here, a straightforward strategy was developed that successfully reverses the polarity of EEO. The result is an apical-out organoid that preserves a distinct apical-basolateral orientation and remains responsive to ovarian steroid hormones. Our investigations highlight the utility of polarity-reversed EEO to study interactions with E. coli and blastocysts. This method of generating apical-out EEO lays the foundation for developing new in vitro functional assays, particularly regarding epithelial interactions with embryos during pregnancy or other luminal constituents in a pathological or diseased state.

Using organoids to investigate human endometrial receptivity

The human endometrium is only receptive to an implanting blastocyst in the mid-secretory phase of each menstrual cycle. Such time-dependent alterations in function require intricate interplay of various factors, largely coordinated by estrogen and progesterone. Abnormal endometrial receptivity is thought to contribute to two-thirds of the implantation failure in humans and therefore significantly hindering IVF success. Despite the incontrovertible importance of endometrial receptivity in implantation, the precise mechanisms involved in the regulation of endometrial receptivity remain poorly defined. This is mainly due to a lack of proper in vitro models that recapitulate the in vivo environment of the receptive human endometrium. Organoids were recently established from human endometrium with promising features to better mimic the receptive phase. Endometrial organoids show long-term expandability and the capability to preserve the structural and functional characteristics of the endometrial tissue of origin. This three-dimensional model maintains a good responsiveness to steroid hormones in vitro and replicates key morphological features of the receptive endometrium in vivo, including pinopodes and pseudostratified epithelium. Here, we review the current findings of endometrial organoid studies that have been focused on investigating endometrial receptivity and place an emphasis on methods to further refine and improve this model.

Development of Polarity-Reversed Endometrial Epithelial Organoids

The uterine epithelium is composed of a single layer of hormone responsive polarized epithelial cells that line the lumen and form tubular glands. Endometrial epithelial organoids (EEO) can be generated from uterine epithelia and recapitulate cell composition and hormone responses in vitro . As such, the development of EEO represents a major advance for facilitating mechanistic studies in vitro . However, a major limitation for the use of EEO cultured in basement membrane extract and other hydrogels is the inner location of apical membrane, thereby hindering direct access to the apical surface of the epithelium to study interactions with the embryo or infectious agents such as viruses and bacteria. Here, a straightforward strategy was developed that successfully reverses the polarity of EEO. The result is an apical-out organoid that preserves a distinct apical-basolateral orientation and remains responsive to ovarian steroid hormones. Our investigations highlight the utility of polarity-reversed EEO to study interactions with E. coli and blastocysts. This method of generating apical-out EEO lays the foundation for developing new in vitro functional assays, particularly regarding epithelial interactions with embryos during pregnancy or other luminal constituents in a pathological or diseased state.

The effect of obesity on uterine receptivity is mediated by endometrial extracellular vesicles that control human endometrial stromal cell decidualization and trophoblast invasion

The objectives of the present study were to determine whether obesity impacts human decidualization and the endometrial control of trophoblast invasion (both of which are required for embryo implantation) and evaluate the potential involvement of endometrial extracellular vesicles (EVs) in the regulation of these physiological processes. Using primary human cell cultures, we first demonstrated that obesity is associated with significantly lower in vitro decidualization of endometrial stromal cells (ESCs). We then showed that a trophoblastic cell line's invasive ability was greater in the presence of conditioned media from cultures of ESCs from obese women. The results of functional assays indicated that supplementation of the culture medium with EVs from nonobese women can rescue (at least in part) the defect in in vitro decidualization described in ESCs from obese women. Furthermore, exposure to endometrial EVs from obese women (vs. nonobese women) was associated with significantly greater invasive activity by HTR-8/SVneo cells. Using mass-spectrometry-based quantitative proteomics, we found that EVs isolated from uterine supernatants of biopsies from obese women (vs. nonobese women) presented a molecular signature focused on cell remodelling and angiogenesis. The proteomics analysis revealed two differentially expressed proteins (fibronectin and angiotensin-converting enzyme) that might be involved specifically in the rescue of the decidualization capacity in ESCs from obese women; both of these proteins are abundantly present in endometrial EVs from nonobese women, and both are involved in the decidualization process. In conclusion, our results provided new insights into the endometrial EVs' pivotal role in the poor uterine receptivity observed in obese women.

Uterine Transcriptome: Understanding Physiology and Disease Processes

In recent years, transcriptomics has enabled us to gain a deeper understanding of fundamental reproductive physiology, including the menstrual cycle, through a more precise molecular analysis. The endometrial mRNA transcript levels fluctuate during the normal menstrual cycle, indicating changes in the relative recruitment and abundance of inflammatory cells, as well as changes in the receptivity and remodeling of the endometrium. In addition to providing a more comprehensive understanding of the molecular underpinnings of pathological gynecological conditions such as endometriosis, leiomyomas, and adenomyosis through RNA sequencing, this has allowed researchers to create transcriptome profiles during both normal menstrual cycles and pathological gynecological conditions. Such insights could potentially lead to more targeted and personalized therapies for benign gynecological conditions. Here, we provide an overview of recent advances in transcriptome analysis of normal and pathological endometrium.