Development of organoids from mouse and human endometrium showing endometrial epithelium physiology and long-term expandability

Advances in the use of organoids in endometrial diseases

The endometrium undergoes cyclical changes in response to hormones and there is a certain degree of heterogeneity among individuals. In vivo identification of the physiologic changes of the endometrium and the pathologic process of related diseases is challenging. There have been recent advances in the use of organoids that mimic the characteristics of the corresponding organs and the morphologic, functional, and personalized characteristics involved in different stages of diseases. In this paper, we discuss the process of creating endometrial organoids, cell sources, types of extracellular matrices, and their application in the study of physiologic endometrial states and various diseases.

Applications of 3D organoids in toxicological studies: a comprehensive analysis based on bibliometrics and advances in toxicological mechanisms

A mechanism exploration is an important part of toxicological studies. However, traditional cell and animal models can no longer meet the current needs for in-depth studies of toxicological mechanisms. The three-dimensional (3D) organoid derived from human embryonic stem cells (hESC) or induced pluripotent stem cells (hiPSC) is an ideal experimental model for the study of toxicological effects and mechanisms, which further recapitulates the human tissue microenvironment and provides a reliable method for studying complex cell-cell interactions. This article provides a comprehensive overview of the state of the 3D organoid technology in toxicological studies, including a bibliometric analysis of the existing literature and an exploration of the latest advances in toxicological mechanisms. The use of 3D organoids in toxicology research is growing rapidly, with applications in disease modeling, organ-on-chips, and drug toxicity screening being emphasized, but academic communications among countries/regions, institutions, and research scholars need to be further strengthened. Attempts to study the toxicological mechanisms of exogenous chemicals such as heavy metals, nanoparticles, drugs and organic pollutants are also increasing. It can be expected that 3D organoids can be better applied to the safety evaluation of exogenous chemicals by establishing a standardized methodology.

Cytoskeletal and inter-cellular junction remodelling in endometrial organoids under oxygen-glucose deprivation: a new potential pathological mechanism for thin endometria

STUDY QUESTION

What is the pathological mechanism involved in a thin endometrium, particularly under ischaemic conditions?

SUMMARY ANSWER

Endometrial dysfunction in patients with thin endometrium primarily results from remodelling in cytoskeletons and cellular junctions of endometrial epithelial cells under ischemic conditions.

WHAT IS KNOWN ALREADY

A healthy endometrium is essential for successful embryo implantation and subsequent pregnancy; ischemic conditions in a thin endometrium compromise fertility outcomes.

STUDY DESIGN, SIZE, DURATION

We recruited 10 patients with thin endometrium and 15 patients with healthy endometrium. Doppler ultrasound and immunohistochemical results confirmed the presence of insufficient endometrial blood perfusion in patients with thin endometrium. Organoids were constructed using healthy endometrial tissue and cultured under oxygen-glucose deprivation (OGD) conditions for 24 h. The morphological, transcriptomic, protein expression, and signaling pathway changes in the OGD organoids were observed. These findings were validated in both thin endometrial tissue and healthy endometrial tissue samples.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Endometrial thickness and blood flow were measured during the late follicular phase using transvaginal Doppler ultrasound. Endometrial tissue was obtained via hysteroscopy. Fresh endometrial tissues were used for the generation and culture of human endometrial organoids. Organoids were cultured in an appropriate medium and subjected to OGD to simulate ischemic conditions. Apoptosis and cell death were assessed using Annexin-V/propidium iodide staining. Immunofluorescence analysis, RNA sequencing, western blotting, simple westerns, immunohistochemistry, and electron microscopy were conducted to evaluate cellular and molecular changes.

MAIN RESULTS AND THE ROLE OF CHANCE

Patients with thin endometrium showed significantly reduced endometrial thickness and altered blood flow patterns compared to those with healthy endometrium. Immunohistochemical staining revealed fewer CD34-positive blood vessels and glands in the thin endometrium group. Organoids cultured under OGD conditions exhibited significant morphological changes, increased apoptosis, and cell death. RNA-seq identified differentially expressed genes related to cytoskeletal remodeling and stress responses. OGD induced a strong cytoskeletal reorganization, mediated by the RhoA/ROCK signaling pathway. Additionally, electron microscopy indicated compromised epithelial integrity and abnormal cell junctions in thin endometrial tissues. Upregulation of hypoxia markers (HIF-1α and HIF-2α) and activation of the RhoA/ROCK pathway were also observed in thin endometrial tissues, suggesting ischemia and hypoxia as underlying mechanisms.

LARGE SCALE DATA

none.

LIMITATIONS AND REASONS FOR CAUTION

The study was conducted in an in vitro model, which may not fully replicate the complexity of in vivo conditions.

WIDER IMPLICATIONS OF THE FINDINGS

This research provides a new three-dimensional in vitro model of thin endometrium, as well as novel insights into the pathophysiological mechanisms of endometrial ischaemia in thin endometrium, offering potential avenues for identifying therapeutic targets for treating fertility issues related to thin endometrium.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China (81925013); National Key Research and Development Project of China (2022YFC2702500, 2021YFC2700303, 2021YFC2700601); the Capital Health Research and Development Project (SF2022-1-4092); the National Natural Science Foundation of China (82288102, 81925013, 82225019, 82192873); Special Project on Capital Clinical Diagnosis and Treatment Technology Research and Transformation Application (Z211100002921054); the Frontiers Medical Center, Tianfu Jincheng Laboratory Foundation(TFJC2023010001). The authors declare that no competing interests exist.

Recent advances in in vitro models simulating the female genital tract toward more effective intravaginal therapeutic delivery

INTRODUCTION

Intravaginal drug delivery has emerged as a promising avenue for treating a spectrum of systemic and local female genital tract (FGT) conditions, using biomaterials as carriers or scaffolds for targeted and efficient administration. Much effort has been made to understand the natural barriers of this route and improve the delivery system to achieve an efficient therapeutic response.

AREAS COVERED

In this review, we conducted a comprehensive literature search using multiple databases (PubMed Scopus Web of Science Google Scholar), to discuss the potential of intravaginal therapeutic delivery, as well as the obstacles unique to this route. The in vitro cell models of the FGT and how they can be applied to probing intravaginal drug delivery are then analyzed. We further explore the limitations of the existing models and the possibilities to make them more promising for delivery studies or biomaterial validation. Complementary information is provided by in vitro acellular techniques that may shed light on mucus-drug interaction.

EXPERT OPINION

Advances in 3D models and cell cultures have enhanced our understanding of the FGT, but they still fail to replicate all variables. Future research should aim to use complementary methods, ensure stability, and develop consistent protocols to improve therapy evaluation and create better predictive in vitro models for women's health.

Enrichment of cell cycle pathways in progesterone-treated endometrial organoids of infertile women compared to fertile women

PURPOSE

To investigate whether the transcriptome profile differs between progesterone-treated infertile and fertile endometrial organoids.

METHODS

Endometrial biopsies were obtained from 14 infertile and seven fertile women, after which organoids were generated from isolated epithelial cells. To mimic the secretory phase, organoids were sequentially treated with 17β-estradiol (E2) and progesterone (P4) and subjected to RNA sequencing. Differentially expressed genes (DEGs) were identified using DESeq2 (lfcThreshold = 0, log2 Fold Change ≥ 1.0 or ≤ -1.0), and a principal component analysis (PCA) plot was generated. Functional enrichment analysis was performed by overrepresentation analysis and Gene Set Enrichment Analysis (GSEA). To functionally assess proliferation, OrganoSeg surface measurements were performed before (T0) and after (T1) differentiation of organoids, and T1/T0 ratios were calculated to determine the proliferation rate.

RESULTS

Although the PCA plot did not show clear clustering of the fertile and infertile samples, 363 significant DEGs (129 upregulated and 234 downregulated) were detected in infertile compared to fertile organoids. Mainly cell cycle processes were highly enriched in infertile organoids. Thus, we hypothesised that proliferative activity during differentiation may be higher in infertile organoids compared to fertile organoids. However, this could not be validated by cell surface measurements.

CONCLUSIONS

This study revealed that cell cycle processes were enriched in E2/P4-treated infertile endometrial organoids as compared to fertile organoids. This could reflect persistently higher proliferative activity of the endometrial epithelial cells in differentiated infertile organoids compared to fertile organoids. To confirm this hypothesis, further studies are warranted.

Pathogenesis of Endometriosis and Endometriosis-Associated Cancers

Endometriosis is a hormone-dependent, chronic inflammatory condition that affects 5-10% of reproductive-aged women. It is a complex disorder characterized by the growth of endometrial-like tissue outside the uterus, which can cause chronic pelvic pain and infertility. Despite its prevalence, the underlying molecular mechanisms of this disease remain poorly understood. Current treatment options are limited and focus mainly on suppressing lesion activity rather than eliminating it entirely. Although endometriosis is generally considered a benign condition, substantial evidence suggests that it increases the risk of developing specific subtypes of ovarian cancer. The discovery of cancer driver mutations in endometriotic lesions indicates that endometriosis may share molecular pathways with cancer. Moreover, the application of single-cell and spatial genomics, along with the development of organoid models, has started to illuminate the molecular mechanisms underlying disease etiology. This review aims to summarize the key genetic mutations and alterations that drive the development and progression of endometriosis to malignancy. We also review the significant recent advances in the understanding of the molecular basis of the disorder, as well as novel approaches and in vitro models that offer new avenues for improving our understanding of disease pathology and for developing new targeted therapies.

The reprotoxic adverse side effects of neurogenic and neuroprotective drugs: current use of human organoid modeling as a potential alternative to preclinical models

The management of neurological disorders heavily relies on neurotherapeutic drugs, but notable concerns exist regarding their possible negative effects on reproductive health. Traditional preclinical models often fail to accurately predict reprotoxicity, highlighting the need for more physiologically relevant systems. Organoid models represent a promising approach for concurrently studying neurotoxicity and reprotoxicity, providing insights into the complex interplay between neurotherapeutic drugs and reproductive systems. Herein, we have examined the molecular mechanisms underlying neurotherapeutic drug-induced reprotoxicity and discussed experimental findings from case studies. Additionally, we explore the utility of organoid models in elucidating the reproductive complications of neurodrug exposure. Have discussed the principles of organoid models, highlighting their ability to recapitulate neurodevelopmental processes and simulate drug-induced toxicity in a controlled environment. Challenges and future perspectives in the field have been addressed with a focus on advancing organoid technologies to improve reprotoxicity assessment and enhance drug safety screening. This review underscores the importance of organoid models in unraveling the complex relationship between neurotherapeutic drugs and reproductive health.

Melatonin and resveratrol alleviate molecular and metabolic toxicity induced by Bisphenol A in endometrial organoids

Bisphenol A (BPA), a widespread environmental contaminant, poses concerns due to its disruptive effects on physiological functions of the uterine endometrium. In contrast, melatonin (MT) and Resveratrol (RSV) are under scrutiny for their potential protective roles against BPA-induced damage. For the efficacy and ethical concerns in the animal test, endometrial organoids, three-dimensional models mimicking endometrium, serve as crucial tools for unraveling the impact of environmental factors on reproductive health. This study aimed to comprehensively characterize the morphological, molecular and metabolic responses of porcine endometrial organoids to BPA and assess the potential protective effects of MT and RSV. Porcine uteri were prepared, digested with collagenase, mixed with Matrigel, and incubated at 38°C with 5 % CO2. Passaging involved dissociation through trypsin-EDTA treatment and subculturing. The culture medium was refreshed every 2-3 days. To investigate the environmental impact on reproductive health, endometrial organoids were treated with BPA (0.5 µM), MT (with/without BPA at 0.1 µM), and/or RSV (10 µM). Various molecular screening using gene expression, western blotting, immunofluorescence staining, and metabolites profiling were assessed the effects of BPA, MT, and RSV in terms of cell viability, morphology, reproductivity, and metabolism alteration in the endometrial organoids. As expected, BPA induced structural and molecular disruptions in organoids, affecting cytoskeletal proteins, Wnt/β-catenin signaling, and epithelial/mesenchymal markers. It triggered oxidative stress and apoptotic pathways, altered miRNA expression, and disrupted the endocannabinoid system. The level of glucose, galactose, and essential amino acids were increased or decreased by approximately 1.5-3 times in BPA-treated groups compared to the control groups (p-value < 0.05), indicating metabolic changes. Moreover, MT and RSV treated groups exhibited protective effects, mitigating BPA-induced disruptions across multiple pathways. For the first time, our study models endometrial organoids, advancing understanding of environmental impacts on reproductive health.

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.

Hypermethylation of Klotho and Peroxisome Proliferator-Activated Receptor γ Concomitant with Overexpression of DNA Methyltransferase 1 in Adenomyosis

Cellular senescence is known to be involved in tissue repair, but its role in adenomyosis remains unclear. This study was tasked to evaluate the expression of Klotho, a well-known aging-suppressing protein, as well as PPARγ and DNMT1 in adenomyotic lesions (AD) in comparison with that of control endometrium (CT). We performed immunohistochemistry analysis of markers of cellular senescence p16 and p21, along with Klotho, PPARγ and DNMT1 in CT and AD samples, followed by the quantification of gene expression of Klotho, PPARγ and DNMT1 in epithelial organoids derived from AD and CT samples and methylation-specific PCR to evaluate promoter methylation status. The effect of forced expression and knockdown of DNMT1 on Klotho and PPARγ expression in ectopic endometrial epithelial cells was evaluated. We found that both p16 and p21 immunoreactivity in AD was significantly higher while that of Klotho and PPARγ was significantly lower than CT samples, which was concomitant with elevated immunoexpression of DNMT1. The results were confirmed by transcriptional analysis using epithelial organoids derived from AD and CT samples. In addition, the promoter regions of both Klotho and PPARγ genes were hypermethylated in AD as compared with CT, and treatment with HDAC and DNMT inhibitors reactivated the expression of both Klotho and PPARγ. Forced expression of DNMT1 resulted in downregulation of both Klotho and PPARγ but its knockdown increased their expression. Thus, overexpression of DNMT1 seems to facilitate the promoter hypermethylation of both Klotho and PPARγ in AD, resulting in their reduced expression that is suggestive of the role of senescence in adenomyosis.

Current strategies using 3D organoids to establish in vitro maternal-embryonic interaction

IMPORTANCE

The creation of robust maternal-embryonic interactions and implantation models is important for comprehending the early stages of embryonic development and reproductive disorders. Traditional two-dimensional (2D) cell culture systems often fail to accurately mimic the highly complex in vivo conditions. The employment of three-dimensional (3D) organoids has emerged as a promising strategy to overcome these limitations in recent years. The advancements in the field of organoid technology have opened new avenues for studying the physiology and diseases affecting female reproductive tract.

OBSERVATIONS

This review summarizes the current strategies and advancements in the field of 3D organoids to establish maternal-embryonic interaction and implantation models for use in research and personalized medicine in assisted reproductive technology. The concepts of endometrial organoids, menstrual blood flow organoids, placental trophoblast organoids, stem cell-derived blastoids, and in vitro-generated embryo models are discussed in detail. We show the incorportaion of organoid systems and microfluidic technology to enhance tissue performance and precise management of the cellular surroundings.

CONCLUSIONS AND RELEVANCE

This review provides insights into the future direction of modeling maternal-embryonic interaction research and its combination with other powerful technologies to interfere with this dialogue either by promoting or hindering it for improving fertility or methods for contraception, respectively. The merging of organoid systems with microfluidics facilitates the creation of sophisticated and functional organoid models, enhancing insights into organ development, disease mechanisms, and personalized medical investigations.

De novo reconstruction of a functional in vivo-like equine endometrium using collagen-based tissue engineering

To better understand molecular aspects of equine endometrial function, there is a need for advanced in vitro culture systems that more closely imitate the intricate 3-dimensional (3D) in vivo endometrial structure than current techniques. However, development of a 3D in vitro model of this complex tissue is challenging. This study aimed to develop an in vitro 3D endometrial tissue (3D-ET) with an epithelial cell phenotype optimized by treatment with a Rho-associated protein kinase (ROCK) inhibitor. Equine endometrial epithelial (eECs) and mesenchymal stromal (eMSCs) cells were isolated separately, and eECs cultured in various concentrations of Rock inhibitor (0, 5, 10 µmol) in epithelial medium (EC-medium) containing 10% knock-out serum replacement (KSR). The optimal concentration of Rock inhibitor for enhancing eEC proliferation and viability was 10 µM. However, 10 µM Rock inhibitor in the 10% KSR EC-medium was able to maintain mucin1 (Muc1) gene expression for only a short period. In contrast, fetal bovine serum (FBS) was able to maintain Muc1 gene expression for longer culture durations. An in vitro 3D-ET was successfully constructed using a collagen-based scaffold to support the eECs and eMSCs. The 3D-ET closely mimicked in vivo endometrium by displaying gland-like eEC-derived structures positive for the endometrial gland marker, Fork headbox A2 (FOXA2), and by mimicking the 3D morphology of the stromal compartment. In addition, the 3D-ET expressed the secretory protein MUC1 on its glandular epithelial surface and responded to LPS challenge by upregulating the expression of the interleukin-6 (IL6) and prostaglandin F synthase (PGFS) genes (P < 0.01), along with an increase in their secretory products, IL-6 (P < 0.01) and prostaglandin F2alpha (PGF2α) (P < 0.001) respectively. In the future, this culture system can be used to study both normal physiology and pathological processes of the equine endometrium.

Targeting GRP75 with a Chlorpromazine Derivative Inhibits Endometrial Cancer Progression Through GRP75-IP3R-Ca2+-AMPK Axis

Tumors often overexpress glucose-regulated proteins, and agents that interfere with the production or activity of these proteins may represent novel cancer treatments. The chlorpromazine derivative JX57 exhibits promising effects against endometrial cancer with minimal extrapyramidal side effects; however, its mechanisms of action are currently unknown. Here, glucose-regulated protein 75 kD (GRP75) is identified as a direct target of JX57 using activity-based protein profiling and loss-of-function experiments. The findings show that GRP75 is necessary for the biological activity of JX57, as JX57 exhibits moderate anticancer properties in GRP75-deficient cancer cells, both in vitro and in vivo. High GRP75 expression is correlated with poor differentiation and poor survival in patients with endometrial cancer, whereas the knockdown of GRP75 can significantly suppress tumor growth. Mechanistically, the direct binding of JX57 to GRP75 impairs the structure of the mitochondria-associated endoplasmic reticulum membrane and disrupts the endoplasmic reticulum-mitochondrial calcium homeostasis, resulting in a mitochondrial energy crisis and AMP-activated protein kinase activation. Taken together, these findings highlight GRP75 as a potential prognostic biomarker and direct therapeutic target in endometrial cancer and suggest that the chlorpromazine derivative JX57 can potentially be a new therapeutic option for endometrial cancer.

The presence of blastocyst within the uteri facilitates lumenal epithelium transformation for implantation via upregulating lysosome proteostasis activity

ABBREVIATIONS

ACTB: actin beta; AREG: amphiregulin; ATP6V0A4: ATPase, H+ transporting, lysosomal V0 subunit A4; Baf A1: bafilomycin A1; BSA: bovine serum albumin; CLDN1: claudin 1; CTSB: cathepsin B; DEGs: differentially expressed genes; E2: 17β-estradiol; ESR: estrogen receptor; GATA2: GATA binding protein 2; GLA: galactosidase, alpha; GO: gene ontology; HBEGF: heparin-binding EGF-like growth factor; IGF1R: insulin-like growth factor 1 receptor; Ihh: Indian hedgehog; ISH: in situ hybridization; LAMP1: lysosomal-associated membrane protein 1; LCM: laser capture microdissection; Le: lumenal epithelium; LGMN: legumain; LIF: leukemia inhibitory factor; LIFR: LIF receptor alpha; MSX1: msh homeobox 1; MUC1: mucin 1, transmembrane; P4: progesterone; PBS: phosphate-buffered saline; PCA: principal component analysis; PPT1: palmitoyl-protein thioesterase 1; PGR: progesterone receptor; PSP: pseudopregnancy; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; qPCR: quantitative real-time polymerase chain reaction; SP: pregnancy; TFEB: transcription factor EB.

Microphysiological Constructs and Systems: Biofabrication Tactics, Biomimetic Evaluation Approaches, and Biomedical Applications

In recent decades, microphysiological constructs and systems (MPCs and MPSs) have undergone significant development, ranging from self-organized organoids to high-throughput organ-on-a-chip platforms. Advances in biomaterials, bioinks, 3D bioprinting, micro/nanofabrication, and sensor technologies have contributed to diverse and innovative biofabrication tactics. MPCs and MPSs, particularly tissue chips relevant to absorption, distribution, metabolism, excretion, and toxicity, have demonstrated potential as precise, efficient, and economical alternatives to animal models for drug discovery and personalized medicine. However, current approaches mainly focus on the in vitro recapitulation of the human anatomical structure and physiological-biochemical indices at a single or a few simple levels. This review highlights the recent remarkable progress in MPC and MPS models and their applications. The challenges that must be addressed to assess the reliability, quantify the techniques, and utilize the fidelity of the models are also discussed.

Morphogenesis and development of human telencephalic organoids in the absence and presence of exogenous extracellular matrix

The establishment and maintenance of apical-basal polarity is a fundamental step in brain development, instructing the organization of neural progenitor cells (NPCs) and the developing cerebral cortex. Particularly, basally located extracellular matrix (ECM) is crucial for this process. In vitro, epithelial polarization can be achieved via endogenous ECM production, or exogenous ECM supplementation. While neuroepithelial development is recapitulated in neural organoids, the effects of different ECM sources in tissue morphogenesis remain underexplored. Here, we show that exposure to a solubilized basement membrane matrix substrate, Matrigel, at early neuroepithelial stages causes rapid tissue polarization and rearrangement of neuroepithelial architecture. In cultures exposed to pure ECM components or unexposed to any exogenous ECM, polarity acquisition is slower and driven by endogenous ECM production. After the onset of neurogenesis, tissue architecture and neuronal differentiation are largely independent of the initial ECM source, but Matrigel exposure has long-lasting effects on tissue patterning. These results advance the knowledge on mechanisms of exogenously and endogenously guided morphogenesis, demonstrating the self-sustainability of neuroepithelial cultures by endogenous processes.

Generation of Human Endometrial Assembloids with a Luminal Epithelium using Air-Liquid Interface Culture Methods

The endometrial lining of the uterus is essential for women's reproductive health and consists of several different types of epithelial and stromal cells. Although models such as gland-like structures (GLSs) and endometrial assembloids (EnAos) are successfully established, they lack an intact luminal epithelium, which makes it difficult to recapitulate endometrial receptivity. Here, a novel EnAo model (ALI-EnAo) is developed by combining endometrial epithelial cells (EnECs) and stromal cells (EnSCs) and using an improved matrix and air-liquid interface (ALI) culture method. ALI-EnAos exhibit intact EnSCs and glandular and luminal epithelia, which recapitulates human endometrium anatomy, cell composition, hormone-induced menstrual cycle changes, gene expression profiles, and dynamic ciliogenesis. The model suggests that EnSCs, together with the extracellular matrix and ALI culture conditions, contribute to EnAo phenotypes and characteristics reflective of the endometrial menstrual cycle. This enables to transcriptionally define endometrial cell subpopulations. It anticipates that ALI-EnAos will facilitate studies on embryo implantation, and endometrial growth, differentiation, and disease.

Estrogen receptor alpha regulates uterine epithelial lineage specification and homeostasis

Postnatal development of the uterus involves specification of undifferentiated epithelium into uterine-type epithelium. That specification is regulated by stromal-epithelial interactions as well as intrinsic cell-specific transcription factors and gene regulatory networks. This study utilized mouse genetic models of Esr1 deletion, endometrial epithelial organoids (EEO), and organoid-stromal co-cultures to decipher the role of Esr1 in uterine epithelial development. Organoids derived from wild-type (WT) mice developed a normal single layer of columnar epithelium. In contrast, EEO from Esr1 null mice developed a multilayered stratified squamous type of epithelium with basal cells. Co-culturing Esr1 null epithelium with WT uterine stromal fibroblasts inhibited basal cell development. Of note, estrogen treatment of EEO-stromal co-cultures and Esr1 conditional knockout mice increased basal epithelial cell markers. Collectively, these findings suggest that Esr1 regulates uterine epithelium lineage plasticity and homeostasis and loss of ESR1 promotes altered luminal-to-basal differentiation driven by ESR1-mediated paracrine factors from the stroma.

Embryo-uterine interaction coordinates mouse embryogenesis during implantation

Embryo implantation into the uterus marks a key transition in mammalian development. In mice, implantation is mediated by the trophoblast and is accompanied by a morphological transition from the blastocyst to the egg cylinder. However, the roles of trophoblast-uterine interactions in embryo morphogenesis during implantation are poorly understood due to inaccessibility in utero and the remaining challenges to recapitulate it ex vivo from the blastocyst. Here, we engineer a uterus-like microenvironment to recapitulate peri-implantation development of the whole mouse embryo ex vivo and reveal essential roles of the physical embryo-uterine interaction. We demonstrate that adhesion between the trophoblast and the uterine matrix is required for in utero-like transition of the blastocyst to the egg cylinder. Modeling the implanting embryo as a wetting droplet links embryo shape dynamics to the underlying changes in trophoblast adhesion and suggests that the adhesion-mediated tension release facilitates egg cylinder formation. Light-sheet live imaging and the experimental control of the engineered uterine geometry and trophoblast velocity uncovers the coordination between trophoblast motility and embryo growth, where the trophoblast delineates space for embryo morphogenesis.

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.

Matrix scaffolds for endometrium-derived organoid models

The uterus-lining endometrium is essential to mammalian reproduction, receiving and accommodating the embryo for proper development. Despite its key role, mechanisms underlying endometrial biology (menstrual cycling, embryo interaction) and disease are not well understood. Its hidden location in the womb, and thereby-associated lack of suitable research models, contribute to this knowledge gap. Recently, 3D organoid models have been developed from both healthy and diseased endometrium. These organoids closely recapitulate the tissue's epithelium phenotype and (patho)biology, including in vitro reproduction of the menstrual cycle. Typically, organoids are grown in a scaffold made of surrogate tissue extracellular matrix (ECM), with mouse tumor basement membrane extracts being the most commonly used. However, important limitations apply including their lack of standardization and xeno-derivation which strongly hinder clinical translation. Therefore, researchers are actively seeking better alternatives including fully defined matrices for faithful and efficient growth of organoids. Here, we summarize the state-of-the-art regarding matrix scaffolds to grow endometrium-derived organoids as well as more advanced organoid-based 3D models. We discuss remaining shortcomings and challenges to advance endometrial organoids toward defined and standardized tools for applications in basic research and translational/clinical fields.

Organoids: opportunities and challenges of cancer therapy

Organoids are a class of multicellular structures with the capability of self-organizing and the characteristic of original tissues, they are generated from stem cells in 3D culture in vitro. Organoids can mimic the occurrence and progression of original tissues and widely used in disease models in recent years. The ability of tumor organoids to retain characteristic of original tumors make them unique for tumorigenesis and cancer therapy. However, the history of organoid development and the application of organoid technology in cancer therapy are not well understood. In this paper, we reviewed the history of organoids development, the culture methods of tumor organoids establishing and the applications of organoids in cancer research for better understanding the process of tumor development and providing better strategies for cancer therapy. The standardization of organoids cultivation facilitated the large-scale production of tumor organoids. Moreover, it was found that combination of tumor organoids and other cells such as immune cells, fibroblasts and nervous cells would better mimic the microenvironment of tumor progression. This might be important developing directions for tumor organoids in the future.

Embryo-derive TNF promotes decidualization via fibroblast activation

Decidualization is a process in which endometrial stromal fibroblasts differentiate into specialized secretory decidual cells and essential for the successful establishment of pregnancy. The underlying mechanism during decidualization still remains poorly defined. Because decidualization and fibroblast activation share similar characteristics, this study was to examine whether fibroblast activation is involved in decidualization. In our study, fibroblast activation-related markers are obviously detected in pregnant decidua and under in vitro decidualization. ACTIVIN A secreted under fibroblast activation promotes in vitro decidualization. We showed that arachidonic acid released from uterine luminal epithelium can induce fibroblast activation and decidualization through PGI₂ and its nuclear receptor PPARδ. Based on the significant difference of fibroblast activation-related markers between pregnant and pseudopregnant mice, we found that embryo-derived TNF promotes CPLA_2α phosphorylation and arachidonic acid release from luminal epithelium. Fibroblast activation is also detected under human in vitro decidualization. Similar arachidonic acid-PGI₂-PPARδ-ACTIVIN A pathway is conserved in human endometrium. Collectively, our data indicate that embryo-derived TNF promotes CPLA_2α phosphorylation and arachidonic acid release from luminal epithelium to induce fibroblast activation and decidualization.

Application of organoid culture from HPV18-positive small cell carcinoma of the uterine cervix for precision medicine

BACKGROUND

Small cell carcinoma of the uterine cervix (SCCC) is a rare and highly malignant human papillomavirus (HPV)-associated cancer in which human genes related to the integration site can serve as a target for precision medicine. The aim of our study was to establish a workflow for precision medicine of HPV-associated cancer using patient-derived organoid.

METHODS

Organoid was established from the biopsy of a patient diagnosed with HPV18-positive SCCC. Therapeutic targets were identified by whole exome sequencing (WES) and RNA-seq analysis. Drug sensitivity testing was performed using organoids and organoid-derived mouse xenograft model.

RESULTS

WES revealed that both the original tumor and organoid had 19 somatic variants in common, including the KRAS p.G12D pathogenic variant. Meanwhile, RNA-seq revealed that HPV18 was integrated into chromosome 8 at 8q24.21 with increased expression of the proto-oncogene MYC. Drug sensitivity testing revealed that a KRAS pathway inhibitor exerted strong anti-cancer effects on the SCCC organoid compared to a MYC inhibitor, which were also confirmed in the xenograft model.

CONCLUSION

In this study, we confirmed two strategies for identifying therapeutic targets of HPV-derived SCCC, WES for identifying pathogenic variants and RNA sequencing for identifying HPV integration sites. Organoid culture is an effective tool for unveiling the oncogenic process of rare tumors and can be a breakthrough for the development of precision medicine for patients with HPV-positive SCCC.

Primary human organoids models: Current progress and key milestones

During the past 10 years the world has experienced enormous progress in the organoids field. Human organoids have shown huge potential to study organ development, homeostasis and to model diseases in vitro. The organoid technology has been widely and increasingly applied to generate patient-specific in vitro 3D cultures, starting from both primary and reprogrammed stem/progenitor cells. This has consequently fostered the development of innovative disease models and new regenerative therapies. Human primary, or adult stem/progenitor cell-derived, organoids can be derived from both healthy and pathological primary tissue samples spanning from fetal to adult age. The resulting 3D culture can be maintained for several months and even years, while retaining and resembling its original tissue's properties. As the potential of this technology expands, new approaches are emerging to further improve organoid applications in biology and medicine. This review discusses the main organs and tissues which, as of today, have been modelled in vitro using primary organoid culture systems. Moreover, we also discuss the advantages, limitations, and future perspectives of primary human organoids in the fields of developmental biology, disease modelling, drug testing and regenerative medicine.

Distinguish Characters of Luminal and Glandular Epithelium from Mouse Uterus Using a Novel Enzyme-Based Separation Method

The uterine luminal epithelium, glandular epithelium, and stromal cells are vital for the establishment of pregnancy. Previously studies have shown various methods to isolate mouse uterine epithelium and stromal cells, including laser capture microdissection (LCM), enzyme digestion, and immunomagnetic beads. Despite the importance of the endometrial epithelium as the site of implantation and nutritional support for the conceptus, there is no isolated method to separate the luminal epithelium and glandular epithelium. Here, we establish a novel enzyme-based way to separate two types of epithelium and keep their viability. In this article, we analyzed their purity by mRNA level, immunostaining, and transcriptome analysis. Our isolation method revealed several unstudied luminal and glandular epithelial markers in transcriptome analysis. We further demonstrated the viability of the isolated epithelium by 2D and 3D cultures. The results showed that we successfully separated the endometrial luminal epithelium and glandular epithelium. We also provided an experimental model for the following study of the physiological function of the different parts of the uterus and related diseases.

Strategies for modelling endometrial diseases

Each month during a woman's reproductive years, the endometrium undergoes vast changes to prepare for a potential pregnancy. Diseases of the endometrium arise for numerous reasons, many of which remain unknown. These endometrial diseases, including endometriosis, adenomyosis, endometrial cancer and Asherman syndrome, affect many women, with an overall lack of efficient or permanent treatment solutions. The challenge lies in understanding the complexity of the endometrium and the extensive changes, orchestrated by ovarian hormones, that occur in multiple cell types over the period of the menstrual cycle. Appropriate model systems that closely mimic the architecture and function of the endometrium and its diseases are needed. The emergence of organoid technology using human cells is enabling a revolution in modelling the endometrium in vitro. The goal of this Review is to provide a focused reference for new models to study the diseases of the endometrium. We provide perspectives on the power of new and emerging models, from organoids to microfluidics, which have opened up a new frontier for studying endometrial diseases.

The World of Organoids: Gastrointestinal Disease Modelling in the Age of 3R and One Health with Specific Relevance to Dogs and Cats

One Health describes the importance of considering humans, animals, and the environment in health research. One Health and the 3R concept, i.e., the replacement, reduction, and refinement of animal experimentation, shape today’s research more and more. The development of organoids from many different organs and animals led to the development of highly sophisticated model systems trying to replace animal experiments. Organoids may be used for disease modelling in various ways elucidating the manifold host–pathogen interactions. This review provides an overview of disease modelling approaches using organoids of different kinds with a special focus on animal organoids and gastrointestinal diseases. We also provide an outlook on how the research field of organoids might develop in the coming years and what opportunities organoids hold for in-depth disease modelling and therapeutic interventions.

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

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

Fluorescence Imaging of 3D Cell Models with Subcellular Resolution

Over the past years, research has made impressive breakthroughs towards the development and implementation of 3D cell models for a wide range of applications, such as drug development and testing, organogenesis, cancer biology, and personalized medicine. Opposed to 2D cell monolayer culture systems, advanced 3D cell models better represent the in vivo physiology. However, for these models to deliver scientific insights, appropriate investigation techniques are required. Despite the potential of fluorescence microscopy to visualize these models with high spatial resolution, sample preparation and imaging assays are not straightforward. Here, we provide different protocols of sample preparation for fluorescence imaging, for both matrix-embedded and matrix-free models ( e.g ., organoids and spheroids, respectively). Additionally, we provide detailed guidelines for imaging 3D cell models via confocal multi-photon fluorescence microscopy. We show that using these protocols, images of 3D cell culture systems can be obtained with sub-cellular resolution. Graphical abstract.

Luminal and Glandular Epithelial Cells from the Porcine Endometrium maintain Cell Type-Specific Marker Gene Expression in Air-Liquid Interface Culture

Two different types of epithelial cells constitute the inner surface of the endometrium. While luminal epithelial cells line the uterine cavity and build the embryo-maternal contact zone, glandular epithelial cells form tubular glands reaching deeply into the endometrial stroma. To facilitate investigations considering the functional and molecular differences between the two populations of epithelial cells and their contribution to reproductive processes, we aimed at establishing differentiated in vitro models of both the luminal and the glandular epithelium of the porcine endometrium using an air–liquid interface (ALI) approach. We first tested if porcine luminal endometrium epithelial cells (PEEC-L) reproducibly form differentiated epithelial monolayers under ALI conditions by monitoring the morphology and the trans-epithelial electrical resistance (TEER). Subsequently, luminal (PEEC-L) and glandular epithelial cells (PEEC-G) were consecutively isolated from the endometrium of the uterine horn. Both cell types were characterized by marker gene expression analysis immediately after isolation. Cells were separately grown at the ALI and assessed by means of histomorphometry, TEER, and marker gene expression after 3 weeks of culture. PEEC-L and PEEC-G formed polarized monolayers of differentiated epithelial cells with a moderate TEER and in vivo-like morphology at the ALI. They exhibited distinct patterns of functional and cell type-specific marker gene expression after isolation and largely maintained these patterns during the culture period. The here presented cell culture procedure for PEEC-L and -G offers new opportunities to study the impact of embryonic signals, endocrine effectors, and reproductive toxins on both porcine endometrial epithelial cell types under standardized in vitro conditions.

A New Horizon in Reproductive Research with Pluripotent Stem Cells: Successful In Vitro Gametogenesis in Rodents, Its Application to Large Animals, and Future In Vitro Reconstitution of Reproductive Organs Such as “Uteroid” and “Oviductoid”

Simple Summary

Functional gametes, such as oocytes and spermatozoa, have been derived from rodent pluripotent stem cells, which can be applied to large animals and ultimately, to humans. In addition to summarizing these topics, we also review additional approaches for in vitro reconstitution of reproductive organs. This review illustrates intensive past efforts and future challenges on stem cell research for in vitro biogenesis in various mammalian models.

Abstract

Recent success in derivation of functional gametes (oocytes and spermatozoa) from pluripotent stem cells (PSCs) of rodents has made it feasible for future application to large animals including endangered species and to ultimately humans. Here, we summarize backgrounds and recent studies on in vitro gametogenesis from rodent PSCs, and similar approaches using PSCs from large animals, including livestock, nonhuman primates (NHPs), and humans. We also describe additional developing approaches for in vitro reconstitution of reproductive organs, such as the ovary (ovarioid), testis (testisoid), and future challenges in the uterus (uteroid) and oviduct (oviductoid), all of which may be derived from PSCs. Once established, these in vitro systems may serve as a robust platform for elucidating the pathology of infertility-related disorders and ectopic pregnancy, principle of reproduction, and artificial biogenesis. Therefore, these possibilities, especially when using human cells, require consideration of ethical issues, and international agreements and guidelines need to be raised before opening “Pandora’s Box”.

Modeling Endometrium Biology and Disease

The endometrium, lining the uterine lumen, is highly essential for human reproduction. Its exceptional remodeling plasticity, including the transformation process to welcome and nest the embryo, is not well understood. Lack of representative and reliable study models allowing the molecular and cellular mechanisms underlying endometrium development and biology to be deciphered is an important hurdle to progress in the field. Recently, powerful organoid models have been developed that not only recapitulate endometrial biology such as the menstrual cycle, but also faithfully reproduce diseases of the endometrium such as endometriosis. Moreover, single-cell profiling endeavors of the endometrium in health and disease, and of derived organoids, start to provide deeper insight into cellular complexity and expression specificities, and in resulting tissue processes. This granular portrayal will not only help in understanding endometrium biology and disease, but also in pinning down the tissue’s stem cells, at present not yet conclusively defined. Here, we provide a general overview of endometrium development and biology, and the efforts of modeling both the healthy tissue, as well as its key diseased form of endometriosis. The future of modeling and deciphering this key tissue, hidden inside the womb, looks bright.

Equine Oviductal Organoid Generation and Cryopreservation

Organoids are a type of three-dimensional (3D) cell culture that more closely mimic the in vivo environment and can be maintained in the long term. To date, oviductal organoids have only been reported in laboratory mice, women, and cattle. Equine oviductal organoids were generated and cultured for 42 days (including 3 passages and freeze-thawing at passage 1). Consistent with the reports in mouse and human oviductal organoids, the equine oviductal organoids revealed round cell clusters with a central lumen. Developing a 3D model of the mare oviduct may allow for an increased understanding of their normal physiology, including hormonal regulation. These organoids may provide an environment that mimics the in vivo equine oviduct and facilitate improved in vitro embryo production in equids.

Mapping Human Reproduction with Single-Cell Genomics

The trillions of cells in the human body develop as a result of the fusion of two extremely specialized cells: an oocyte and a sperm. This process is essential for the continuation of our species, as it ensures that parental genetic information is mixed and passed on from generation to generation. In addition to producing oocytes, the female reproductive system must provide the environment for the appropriate development of the fetus until birth. New genomic and computational tools offer unique opportunities to study the tight spatiotemporal regulatory mechanisms that are required for the cycle of human reproduction. This review explores how single-cell technologies have been used to build cellular atlases of the human reproductive system across the life span and how these maps have proven useful to better understand reproductive pathologies and dissect the heterogeneity of in vitro model systems. Expected final online publication date for the Annual Review of Genomics and Human Genetics, Volume 23 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Farm and Companion Animal Organoid Models in Translational Research: A Powerful Tool to Bridge the Gap Between Mice and Humans

Animal organoid models derived from farm and companion animals have great potential to contribute to human health as a One Health initiative, which recognize a close inter-relationship among humans, animals and their shared environment and adopt multi-and trans-disciplinary approaches to optimize health outcomes. With recent advances in organoid technology, studies on farm and companion animal organoids have gained more attention in various fields including veterinary medicine, translational medicine and biomedical research. Not only is this because three-dimensional organoids possess unique characteristics from traditional two-dimensional cell cultures including their self-organizing and self-renewing properties and high structural and functional similarities to the originating tissue, but also because relative to conventional genetically modified or artificially induced murine models, companion animal organoids can provide an excellent model for spontaneously occurring diseases which resemble human diseases. These features of companion animal organoids offer a paradigm-shifting approach in biomedical research and improve translatability of in vitro studies to subsequent in vivo studies with spontaneously diseased animals while reducing the use of conventional animal models prior to human clinical trials. Farm animal organoids also could play an important role in investigations of the pathophysiology of zoonotic and reproductive diseases by contributing to public health and improving agricultural production. Here, we discuss a brief history of organoids and the most recent updates on farm and companion animal organoids, followed by discussion on their potential in public health, food security, and comparative medicine as One Health initiatives. We highlight recent evolution in the culturing of organoids and their integration with organ-on-a-chip systems to overcome current limitations in in vitro studies. We envision multidisciplinary work integrating organoid culture and organ-on-a-chip technology can contribute to improving both human and animal health.

Treating intrauterine adhesion using conditionally reprogrammed physiological endometrial epithelial cells

Background

There is unmet need for effective therapies of intrauterine adhesions (IUAs) that are common cause of menstrual disturbance and infertility, since current clinical procedures do not improve prognosis for patients with moderate to severe IUA, with a recurrence rate of 23–50%. Stem cell-based therapy has emerged as a therapeutic option with unsolved issues for IUA patients in the past few years. Primary endometrial epithelial cells for cell therapy are largely hampered with the extremely limited proliferation capacity of uterine epithelial cells. This study was to evaluate whether IUA is curable with conditionally reprogrammed (CR) endometrial epithelial cells.

Methods

Mouse endometrial epithelial cells (MEECs) were isolated from C57BL female mice, and long-term cultures of MEECs were established and maintained with conditional reprogramming (CR) method. DNA damage response analysis, soft agar assay, and matrigel 3D culture were carried out to determine the normal biological characteristics of CR-MEECs. The tissue-specific differentiation potential of MEECs was analyzed with air–liquid interface (ALI) 3D culture, hematoxylin and eosin (H&E) staining, Masson’s trichrome and DAB staining, immunofluorescence assay. IUA mice were constructed and transplanted with CR-MEECs. Repair and mechanisms of MEECs transplantation in IUA mice were measured with qRT-PCR, Masson’s trichrome, and DAB staining.

Results

We first successfully established long-term cultures of MEECs using CR approach. CR-MEECs maintained a rapid and stable proliferation in this co-culture system. Our data confirmed that CR-MEECs retained normal biological characteristics and endometrium tissue-specific differentiation potential. CR-MEECs also expressed estrogen and progesterone receptors and maintained the exquisite sensitivity to sex hormones in vitro. Most importantly, allogeneic transplantation of CR-MEECs successfully repaired the injured endometrium and significantly improved the pregnancy rate of IUA mice.

Conclusions

Conditionally reprogrammed physiological endometrial epithelial cells provide a novel strategy in IUA clinics in a personalized or generalized manner and also serve as a physiological model to explore biology of endometrial epithelial cells and mechanisms of IUA.

Uterine bleeding: how understanding endometrial physiology underpins menstrual health

Menstruation is a physiological process that is typically uncomplicated. However, up to one third of women globally will be affected by abnormal uterine bleeding (AUB) at some point in their reproductive years. Menstruation (that is, endometrial shedding) is a fine balance between proliferation, decidualization, inflammation, hypoxia, apoptosis, haemostasis, vasoconstriction and, finally, repair and regeneration. An imbalance in any one of these processes can lead to the abnormal endometrial phenotype of AUB. Poor menstrual health has a negative impact on a person's physical, mental, social, emotional and financial well-being. On a global scale, iron deficiency and iron deficiency anaemia are closely linked with AUB, and are often under-reported and under-recognized. The International Federation of Gynecology and Obstetrics have produced standardized terminology and a classification system for the causes of AUB. This standardization will facilitate future research endeavours, diagnosis and clinical management. In a field where no new medications have been developed for over 20 years, emerging technologies are paving the way for a deeper understanding of the biology of the endometrium in health and disease, as well as opening up novel diagnostic and management avenues.

Endometrial organoids derived from Mayer-Rokitansky-Küster-Hauser syndrome patients provide insights into disease-causing pathways

The uterus is responsible for the nourishment and mechanical protection of the developing embryo and fetus and is an essential part in mammalian reproduction. Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is characterized by agenesis of the uterus and upper part of the vagina in females with normal ovarian function. Although heavily studied, the cause of the disease is still enigmatic. Current research in the field of MRKH mainly focuses on DNA-sequencing efforts and, so far, has been unable to decipher the nature and heterogeneity of the disease, thereby holding back scientific and clinical progress. Here, we developed long-term expandable organoid cultures from endometrium found in uterine rudiment horns of MRKH patients. Phenotypically, they share great similarity with healthy control organoids and are surprisingly fully hormone responsive. Transcriptome analyses, however, identified an array of dysregulated genes that point to potentially disease-causing pathways altered during the development of the female reproductive tract. We consider the endometrial organoid cultures to be a powerful research tool that promise to enable an array of studies into the pathogenic origins of MRKH syndrome and possible treatment opportunities to improve patient quality of life.

Head and neck cancer organoids as a promising tool for personalized cancer therapy: A literature review

Background and Aim

Chemotherapy and targeted therapy are used in treating head and neck cancers (HNCs) either alone or in combination with surgery, especially in advanced tumors but these treatments have resulted in variable outcomes in different patients. This, along with the introduction of new therapies to improve the survival of patients makes it necessary to search for models that can predict the response to treatment among different patients. Organoids, as three‐dimensional culture models, have been studied more widely in non‐HNCs and to a lesser extent in HNCs as tools to predict treatment outcomes. We aimed to conduct a review to validate the use of organoids as a preclinical tool for the treatment of HNCs patients.

Methods

A comprehensive literature search was separately performed by both authors in PubMed and google scholar databases, using the following keywords: “organoid,” “head and neck cancer,” “personalized medicine,” “chemotherapy,” and “targeted therapy.” The articles published up to September 2021 were included in this review and selected according to a quality appraisal method.

Results

Examination of HNC‐derived organoids made in various studies showed that these organoids had the ability to recapitulate original tumor features, including histopathological properties, functional characteristics, and expression of molecular markers in almost all of the studies. Differential sensitivity to chemotherapy drugs similar to in vivo was observed in sensitivity testing. Epidermal growth factor receptor (EGFR) expression levels were different between organoids from different patients and EGFR expression level was found to correlate with the response to anti‐EGFR targeted therapy. A similar result was reported for organoids derived from salivary adenoid cystic carcinoma.

Conclusion

Since HNC‐derived organoids seem to recapitulate characteristics of original tumors and to show differential responses to different chemotherapy and targeted therapy agents, these organoids might have the potential to be used as preclinical prediction tools for the treatment of HNC patients.

Stem cells technology as a platform for generating reproductive system organoids and treatment of infertility-related diseases

In recent years, stem cells have known as a helpful biological tool for the accurate diagnosis, treatment and recognition of diseases. Using stem cells as biomarkers have presented high potential in the early detection of many diseases. Another advancement in stem cell technology includes stem cell derived organoids model that could be a promising platform for diagnosis and modeling different diseases. Furthermore, therapeutic capabilities of stem cell therapy have increased hope in the face of different disability managements. All of these technologies are also widely used in reproductive related diseases especially in today's world that many couples encounter infertility problems. However, with the aid of numerous improvements in the treatment of infertility, over 80% of couples who dreamed of having children could now have children. Due to the fact that infertility has many negative effects on personal and social lives of young couples, many researchers have focused on the treatment of male and female reproductive system abnormalities with different types of stem cells, including embryonic stem cells, bone marrow mesenchymal stem cells (MSCs), and umbilical cord-derived MSCs. Also, design and formation of reproductive system organoids provide a fascinating window into disease modeling, drug screening, personalized therapy, and regeneration medicine. Utilizing these techniques to study, model and treat the infertility-related diseases has drawn attention of many scientists. This review explains different applications of stem cells in generating reproductive system organoids and stem cell-based therapies for male and female infertility related diseases treatment.

The Roles of Extracellular Vesicles and Organoid Models in Female Reproductive Physiology

Culture model systems that can recapitulate the anatomy and physiology of reproductive organs, such as three-dimensional (3D) organoid culture systems, limit the cost and welfare concerns associated with a research animal colony and provide alternative approaches to study specific processes in humans and animals. These 3D models facilitate a greater understanding of the physiological role of individual cell types and their interactions than can be accomplished with traditional monolayer culture systems. Furthermore, 3D culture systems allow for the examination of specific cellular, molecular, or hormonal interactions, without confounding factors that occur with in vivo models, and provide a powerful approach to study physiological and pathological reproductive conditions. The goal of this paper is to review and compare organoid culture systems to other in vitro cell culture models, currently used to study female reproductive physiology, with an emphasis on the role of extracellular vesicle interactions. The critical role of extracellular vesicles for intercellular communication in physiological processes, including reproduction, has been well documented, and an overview of the roles of extracellular vesicles in organoid systems will be provided. Finally, we will propose future directions for understanding the role of extracellular vesicles in normal and pathological conditions of reproductive organs, utilizing 3D organoid culture systems.

Human Endometrial Organoids: Recent Research Progress and Potential Applications

Since traditional two-dimensional (2D) cell culture cannot meet the demand of simulating physiological conditions in vivo, three-dimensional (3D) culture systems have been developed. To date, most of these systems have been applied for the culture of gastrointestinal and neural tissue. As for the female reproductive system, the culture of endometrial and oviductal tissues in Matrigel has also been performed, but there are still some problems that remain unsolved. This review highlights recent progress regarding endometrial organoids, focusing on the signal for organoid derivation and maintenance, the coculture of the epithelium and stroma, the drug screening using organoids from cancer patients, and provides a potential guideline for genome editing in endometrial organoids.

Organoids from human tooth showing epithelial stemness phenotype and differentiation potential

Insight into human tooth epithelial stem cells and their biology is sparse. Tissue-derived organoid models typically replicate the tissue’s epithelial stem cell compartment. Here, we developed a first-in-time epithelial organoid model starting from human tooth. Dental follicle (DF) tissue, isolated from unerupted wisdom teeth, efficiently generated epithelial organoids that were long-term expandable. The organoids displayed a tooth epithelial stemness phenotype similar to the DF’s epithelial cell rests of Malassez (ERM), a compartment containing dental epithelial stem cells. Single-cell transcriptomics reinforced this organoid-ERM congruence, and uncovered novel, mouse-mirroring stem cell features. Exposure of the organoids to epidermal growth factor induced transient proliferation and eventual epithelial-mesenchymal transition, highly mimicking events taking place in the ERM in vivo. Moreover, the ERM stemness organoids were able to unfold an ameloblast differentiation process, further enhanced by transforming growth factor-β (TGFβ) and abrogated by TGFβ receptor inhibition, thereby reproducing TGFβ's known key position in amelogenesis. Interestingly, by creating a mesenchymal-epithelial composite organoid (assembloid) model, we demonstrated that the presence of dental mesenchymal cells (i.e. pulp stem cells) triggered ameloblast differentiation in the epithelial stem cells, thus replicating the known importance of mesenchyme-epithelium interaction in tooth development and amelogenesis. Also here, differentiation was abrogated by TGFβ receptor inhibition. Together, we developed novel organoid models empowering the exploration of human tooth epithelial stem cell biology and function as well as their interplay with dental mesenchyme, all at present only poorly defined in humans. Moreover, the new models may pave the way to future tooth-regenerative perspectives.

Tissue Models for Neisseria gonorrhoeae Research—From 2D to 3D

Neisseria gonorrhoeae is a human-specific pathogen that causes gonorrhea, the second most common sexually transmitted infection worldwide. Disease progression, drug discovery, and basic host-pathogen interactions are studied using different approaches, which rely on models ranging from 2D cell culture to complex 3D tissues and animals. In this review, we discuss the models used in N. gonorrhoeae research. We address both in vivo (animal) and in vitro cell culture models, discussing the pros and cons of each and outlining the recent advancements in the field of three-dimensional tissue models. From simple 2D monoculture to complex advanced 3D tissue models, we provide an overview of the relevant methodology and its application. Finally, we discuss future directions in the exciting field of 3D tissue models and how they can be applied for studying the interaction of N. gonorrhoeae with host cells under conditions closely resembling those found at the native sites of infection.

Organoids to model the endometrium: implantation and beyond

Despite advances in assisted reproductive techniques in the 4 decades since the first human birth after in vitro fertilisation, 1–2% of couples experience recurrent implantation failure, and some will never achieve a successful pregnancy even in the absence of a confirmed dysfunction. Furthermore, 1–2% of couples who do conceive, either naturally or with assistance, will experience recurrent early loss of karyotypically normal pregnancies. In both cases, embryo-endometrial interaction is a clear candidate for exploration. The impossibility of studying implantation processes within the human body has necessitated the use of animal models and cell culture approaches. Recent advances in 3-dimensional modelling techniques, namely the advent of organoids, present an exciting opportunity to elucidate the unanswerable within human reproduction. In this review, we will explore the ontogeny of implantation modelling and propose a roadmap to application and discovery.

A Revised Stem Cell Theory for the Pathogenesis of Endometriosis

During the past decade, a stem cell-based hypothesis has emerged (among many others) to explain the pathogenesis of endometriosis. The initial hypothesis proposed that endometriosis arose from a single or a few specific cells with stem cell properties, including self-renewal and multi-lineage cell differentiation. The origins of the endometriosis-initiating stem cells were thought to be the bone marrow, uterine endometrium, and other tissues. Based on the implantation or metastatic theory in combination with the initial stem cell theory, one or a few multipotent stem/progenitor cells present in the eutopic endometrium or bone marrow translocate to ectopic sites via fallopian tubes during menstruation, vasculolymphatic routes, or through direct migration and invasion. Subsequently, they give rise to endometriotic lesions followed by differentiation into various cell components of endometriosis, including glandular and stromal cells. Recent somatic mutation analyses of deep infiltrating endometriosis, endometrioma, and eutopic normal endometrium using next-generation sequencing techniques have redefined the stem cell theory. It is now proposed that stem/progenitor cells of at least two different origins—epithelium and stroma—sequentially, differentially, but coordinately contribute to the genesis of endometriosis. The dual stem cell theory on how two (or more) stem/progenitor cells differentially and coordinately participate in the establishment of endometriotic lesions remains to be elucidated. Furthermore, the stem/progenitor cells involved in this theory also remain to be identified. Given that the origin of endometriosis is eutopic endometrium, the candidate cells for endometriotic epithelium-initiating cells are likely to be endometrial epithelial cells positive for either N-cadherin or SSEA-1 or both. The candidate cells for endometriotic stroma-initiating cells may be endometrial mesenchymal stem cells positive for SUSD2. Endometrial side population cells are also a possible candidate because they contain unipotent or multipotent cells capable of behaving as endometrial epithelial and stromal stem/progenitor cells.

Establishment of Adenomyosis Organoids as a Preclinical Model to Study Infertility

Adenomyosis is related to infertility and miscarriages, but so far there are no robust in vitro models that reproduce its pathological features to study the molecular mechanisms involved in this disease. Endometrial organoids are in vitro 3D models that recapitulate the native microenvironment and reproduce tissue characteristics that would allow the study of adenomyosis pathogenesis and related infertility disorders. In our study, human endometrial biopsies from adenomyosis (n = 6) and healthy women (n = 6) were recruited. Organoids were established and hormonally differentiated to recapitulate midsecretory and gestational endometrial phases. Physiological and pathological characteristics were evaluated by immunohistochemistry, immunofluorescence, qRT-PCR, and ELISA. Secretory and gestational organoids recapitulated in vivo glandular epithelial phenotype (pan-cytokeratin, Muc-1, PAS, Laminin, and Ki67) and secretory and gestational features (α-tubulin, SOX9, SPP1, PAEP, LIF, and 17βHSD2 expression and SPP1 secretion). Adenomyosis organoids showed higher expression of TGF-β2 and SMAD3 and increased gene expression of SPP1, PAEP, LIF, and 17βHSD2 compared with control organoids. Our results demonstrate that organoids derived from endometria of adenomyosis patients and differentiated to secretory and gestational phases recapitulate native endometrial-tissue-specific features and disease-specific traits. Adenomyosis-derived organoids are a promising in vitro preclinical model to study impaired implantation and pregnancy disorders in adenomyosis and enable personalized drug screening.

Endometrial Stem/Progenitor Cells–Their Role in Endometrial Repair and Regeneration

The human endometrium is a remarkable tissue, undergoing ~450 cycles of proliferation, differentiation, shedding (menstruation), repair, and regeneration over a woman's reproductive lifespan. Post-menstrual repair is an extremely rapid and scar-free process, with re-epithelialization of the luminal epithelium completed within 48 h of initiation of shedding. Following menstruation, the functionalis grows from the residual basalis layer during the proliferative phase under the influence of rising circulating estrogen levels. The regenerative capacity of the endometrium is attributed to stem/progenitor cells which reside in both the epithelial and stromal cell compartments of the basalis layer. Finding a definitive marker for endometrial epithelial progenitors (eEPCs) has proven difficult. A number of different markers have been suggested as putative progenitor markers including, N-cadherin, SSEA-1, AXIN2, SOX-9 and ALDH1A1, some of which show functional stem cell activity in in vitro assays. Each marker has a unique location(s) in the glandular epithelium, which has led to the suggestion that a differentiation hierarchy exists, from the base of epithelial glands in the basalis to the luminal epithelium lining the functionalis, where epithelial cells express different combinations of markers as they differentiate and move up the gland into the functionalis away from the basalis niche. Perivascular endometrial mesenchymal stem cells (eMSCs) can be identified by co-expression of PDGFRβ and CD146 or by a single marker, SUSD2. This review will detail the known endometrial stem/progenitor markers; their identity, location and known interactions and hierarchy across the menstrual cycle, in particular post-menstrual repair and estrogen-driven regeneration, as well as their possible contributions to menstruation-related disorders such as endometriosis and regeneration-related disorder Asherman's syndrome. We will also highlight new techniques that allow for a greater understanding of stem/progenitor cells' role in repair and regeneration, including 3D organoids, 3D slice cultures and gene sequencing at the single cell level. Since mouse models are commonly used to study menstruation, repair and regeneration we will also detail the mouse stem/progenitor markers that have been investigated in vivo.