Putative stem cell activity of human endometrial epithelial and stromal cells during the menstrual cycle

The Endometrial Stem/Progenitor Cells and Their Niches

Endometrial stem/progenitor cells are a type of stem cells with the ability to self-renew and differentiate into multiple cell types. They exist in the endometrium and form niches with their neighbor cells and extracellular matrix. The interaction between endometrial stem/progenitor cells and niches plays an important role in maintaining, repairing, and regenerating the endometrial structure and function. This review will discuss the characteristics and functions of endometrial stem/progenitor cells and their niches, the mechanisms of their interaction, and their roles in endometrial regeneration and diseases. Finally, the prospects for their applications will also be explored.

Unveiling heterogeneity in MSCs: exploring marker-based strategies for defining MSC subpopulations

Mesenchymal stem/stromal cells (MSCs) represent a heterogeneous cell population distributed throughout various tissues, demonstrating remarkable adaptability to microenvironmental cues and holding immense promise for disease treatment. However, the inherent diversity within MSCs often leads to variability in therapeutic outcomes, posing challenges for clinical applications. To address this heterogeneity, purification of MSC subpopulations through marker-based isolation has emerged as a promising approach to ensure consistent therapeutic efficacy. In this review, we discussed the reported markers of MSCs, encompassing those developed through candidate marker strategies and high-throughput approaches, with the aim of explore viable strategies for addressing the heterogeneity of MSCs and illuminate prospective research directions in this field.

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.

Mechanisms of Regeneration and Fibrosis in the Endometrium

The uterine lining (endometrium) regenerates repeatedly over the life span as part of its normal physiology. Substantial portions of the endometrium are shed during childbirth (parturition) and, in some species, menstruation, but the tissue is rapidly rebuilt without scarring, rendering it a powerful model of regeneration in mammals. Nonetheless, following some assaults, including medical procedures and infections, the endometrium fails to regenerate and instead forms scars that may interfere with normal endometrial function and contribute to infertility. Thus, the endometrium provides an exceptional platform to answer a central question of regenerative medicine: Why do some systems regenerate while others scar? Here, we review our current understanding of diverse endometrial disruption events in humans, nonhuman primates, and rodents, and the associated mechanisms of regenerative success and failure. Elucidating the determinants of these disparate repair processes promises insights into fundamental mechanisms of mammalian regeneration with substantial implications for reproductive health.

Platelet-rich fibrin improves repair and regeneration of damaged endometrium in rats

Purpose

Intrauterine adhesion (IUA) is the most common cause of uterine infertility. This study aims to evaluate whether platelet-rich fibrin (PRF) treatment can stimulate damaged endometrium regeneration in rats.

Methods

First, hematoxylin and eosin (HE) staining, scanning and transmission electron microscopy, and ELISAs were used to evaluate the microstructure of PRF. Then, mechanical damage was used to establish an IUA rat model. A total of 40 SD female rats were randomized to three groups: PRF transplantation group, IUA group, and sham group. Rats were sacrificed at 3, 7, and 14 days and uteruses were obtained for further analysis. Finally, functional and histological recovery of the damaged endometrium was analyzed by pregnancy test, HE staining, Masson's staining, and immunohistochemistry.

Results

PRF has two distinct zones, platelets and fibrin zone. Long and narrow fibrin fibers interconnected with each other and formed a three-dimensional, flexible, and elastic structure; platelet aggregates were trapped in fibrin fibers, and each platelet is associated with several fibrin fibers. PRF exudates promoted endometrial stromal cell proliferation and migration in vitro. PRF transplantation was beneficial for maintaining uterine structure, promoting endometrial luminal epithelium and endometrial gland regeneration, and decreasing fibrotic areas in vivo.

Conclusion

Intrauterine administration of PRF was demonstrated to be effective in preventing IUA and stimulating damaged endometrium regeneration in rats. This study not only provided a promising method for its potential in endometrial regeneration in women who suffer from uterine infertility but also may prevent IUA after intrauterine surgery in clinical cases.

Long-term maintenance of human endometrial epithelial stem cells and their therapeutic effects on intrauterine adhesion

Background

The human endometrium is a highly regenerative tissue that is believed to have two main types of stem cells: endometrial mesenchymal/stromal stem cells (eMSCs) and endometrial epithelial stem cells (eESCs). So far, eMSCs have been extensively studied, whereas the studies of eESCs are constrained by the inability to culture and expand them in vitro. The aim of this study is to establish an efficient method for the production of eESCs from human endometrium for potential clinical application in intrauterine adhesion (IUA).

Results

Here we developed a culture condition with a combination of some small molecules for in vitro culturing and expansion of human SSEA-1⁺ cells. The SSEA-1⁺ cells exhibited stem/progenitor cell activity in vitro, including clonogenicity and differentiation capacity into endometrial epithelial cell-like cells. In addition, the SSEA-1⁺ cells, embedded in extracellular matrix, swiftly self-organized into organoid structures with long-term expansion capacity and histological phenotype of the human endometrial epithelium. Specifically, we found that the SSEA-1⁺ cells showed stronger therapeutic potential than eMSCs for IUA in vitro. In a rat model of IUA, in situ injection of the SSEA-1⁺ cells-laden chitosan could efficiently reduce fibrosis and facilitate endometrial regeneration.

Conclusions

Our work demonstrates an approach for isolation and expansion of human eESCs in vitro, and an appropriate marker, SSEA-1, to identify eESCs. Furthermore, the SSEA-1⁺ cells-laden chitosan might provide a novel cell-based approach for IUA treatment. These findings will advance the understanding of pathophysiology during endometrial restoration which may ultimately lead to more rational clinical practice.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00905-4.

Expression of glucocorticoid and androgen receptors in bone marrow-derived hematopoietic and nonhematopoietic murine endometrial cells

OBJECTIVE

To determine whether bone marrow (BM)-derived cells engrafting the murine endometrium express the glucocorticoid receptor (GR) and androgen receptor (AR). Recent data demonstrate that BM is a long-term source of multiple hematopoietic and nonhematopoietic endometrial cell types. Important roles for glucocorticoids and androgens in regulating endometrial functions, including decidualization and early embryo attachment/invasion, have very recently emerged. Whether endometrial cells of BM origin express glucocorticoid or ARs has not been previously studied.

DESIGN

Animal study.

SETTING

Basic science laboratory.

ANIMAL(S)

Wild-type C57BL/6J male mice expressing enhanced green fluorescent protein (GFP) and syngeneic wild-type C57BL/6J female mice aged 6-9 weeks.

INTERVENTION(S)

Murine bone marrow transplant.

MAIN OUTCOME MEASURE(S)

Bone marrow cells were harvested from adult wild-type C57BL/6 mice and subjected to flow cytometry to identify the percentage of hematopoietic and nonhematopoietic cells expressing GR or AR. Uterine tissue sections from lethally irradiated syngeneic adult female C57BL/6 mice that had been recipients of BM transplants from adult male transgenic donor mice ubiquitously expressing GFP were studied. Immunohistochemistry was performed in the uterine tissue sections of the recipient mice at 5, 9, and 12 months after transplant using specific anti-GR, anti-AR, anti-GFP, anti-CD45 (pan leukocyte marker), and anti-F4/80 (murine macrophage marker) primary antibodies. Confocal laser microscopy was used to localize and quantitate BM-derived (GFP⁺) cell types in the endometrial stromal and epithelial compartments and determine whether BM-derived cell types in the murine endometrium express GR or AR.

RESULT(S)

Hematopoietic cells comprised 93.6%-96.6% of all cells in the BM, of which 98.1% ± 0.2% expressed GR and 92.2% ± 4.4% expressed AR. Nonhematopoietic cells comprised 0.4%-1.3% of BM, of which 52.8% ± 5.9% expressed GR and 48.9% ± 3.4% expressed AR. After BM transplant, the proportion of cells originating from BM in the endometrial stromal compartment increased over time, reaching 13.5% ± 2.3% at 12 months after transplant. In the epithelial compartments, <1% of the cells were of BM origin at 12 months after transplant. Most (60%-72%) GR⁺ and/or AR⁺ BM-derived cells in the stroma were hematopoietic (CD45⁺) cells, of which 37%-51% were macrophages. Nonetheless, 28%-33% of GR⁺ cells, and 28%-40% of AR⁺ BM-derived cells, were nonhematopoietic (CD45^-) stromal cells of BM origin.

CONCLUSION(S)

A substantial number of BM-derived cells express GR and AR, suggesting a role for these cells in both glucocorticoid-regulated and androgen-regulated endometrial functions, such as proliferation and/or decidualization.

Pathogenesis of Human Adenomyosis: Current Understanding and Its Association with Infertility

The aim of this review article was to summarize our current understanding on the etiologies and pathogenesis of human adenomyosis and to clarify the relative association between adenomyosis and infertility. The exact pathogenesis of adenomyosis is still elusive. Among different reported concepts, direction invagination of gland cells from the basalis endometrium deep into myometrium is the most widely accepted opinion on the development of adenomyosis. According to this concept, endometrial epithelial cells and changed fibroblasts, abnormally found in the myometrium in response to repeated tissue injury and/or disruption at the endometrium-myometrium interface (EMI), elicit hyperplasia and hypertrophy of the surrounding smooth muscle cells. In this review, a comprehensive review was performed with a literature search using PubMed for all publications in English and Japanese (abstract in English), related to adenomyosis and infertility, from inception to April 2021. As an estrogen-regulated factor, hepatocyte growth factor (HGF) exhibits multiple functions in endometriosis, a disease commonly believed to arise from the functionalis endometrium. As a mechanistic basis of gland invagination, we investigated the role of HGF, either alone or in combination with estrogen, in the occurrence of epithelial-mesenchymal transition (EMT) in adenomyosis. Aside from microtrauma at the EMI, metaplasia of displaced Müllerian remnants, differentiation of endometrial stem/progenitor cells within the myometrium and somatic mutation of some target genes have been put forward to explain how adenomyosis develops. In addition, the possible role of microRNAs in adenomyosis is also discussed. Besides our knowledge on the conventional classification (focal and diffuse), two recently proposed classifications (intrinsic and extrinsic) of adenomyosis and the biological differences between them have been described. Although the mechanistic basis is unclear, the influence of adenomyosis on fertility outcome is important, especially considering the recent tendency to delay pregnancy among women. Besides other proposed mechanisms, a recent transmission election microscopic (TEM) study indicated that microvilli damage and an axonemal alteration in the apical endometria of human adenomyosis, in response to endometrial inflammation, may be involved in negative fertility outcomes. We present a critical analysis of the literature data concerning the mechanistic basis of infertility in women with adenomyosis and its impact on fertility outcome.

Mesenchymal Stem Cells in Embryo-Maternal Communication under Healthy Conditions or Viral Infections: Lessons from a Bovine Model

Bovine mesenchymal stem cells are a relevant cell population found in the maternal reproductive tract that exhibits the immunomodulation capacity required to prevent embryo rejection. The phenotypic plasticity showed by both endometrial mesenchymal stem cells (eMSC) and embryonic trophoblast through mesenchymal to epithelial transition and epithelial to mesenchymal transition, respectively, is essential for embryo implantation. Embryonic trophoblast maintains active crosstalk via EVs and soluble proteins with eMSC and peripheral blood MSC (pbMSC) to ensure the retention of eMSC in case of pregnancy and induce the chemotaxis of pbMSC, critical for successful implantation. Early pregnancy-related proteins and angiogenic markers are detected as cargo in EVs and the soluble fraction of the embryonic trophectoderm secretome. The pattern of protein secretion in trophectoderm-EVs changes depending on their epithelial or mesenchymal phenotype and due to the uptake of MSC EVs. However, the changes in this EV-mediated communication between maternal and embryonic MSC populations infected by viruses that cause abortions in cattle are poorly understood. They are critical in the investigation of reproductive viral pathologies.

Unique expression patterns of the embryonal stem cell marker SOX2 and hormone receptors suggest the existence of a subpopulation of epithelial stem/progenitor cells in porcine and bovine endometrium

BACKGROUND

There are currently insufficient data on the population of endometrial epithelial stem/progenitor cells in farm animals.

OBJECTIVES

With the aim of identifying a potential population of epithelial stem/progenitor cells in the porcine and bovine endometrium, this study immunohistochemically examined the expression patterns of the oestrogen and progesterone receptors, as well as that of the embryonal stem cell marker SOX2.

METHODS

A total of 24 endometrial tissue samples obtained from cycling pigs (n = 12) and cows (n = 12) were included in our study. Each endometrium was divided into basal, middle and luminal portions. The percentage of marker-positive cells and the intensity of the immunoreaction in each portion of the endometrium were determined.

RESULTS

Inverse expression patterns of SOX2 and progesterone receptors were found in both animal species throughout the oestrous cycle. Strong diffuse SOX2 expression was detected in the basal portions of the glands, while a significant decrease in positivity and a weak immunoreaction were found in the luminal two thirds of the glandular epithelium. Strong progesterone receptor expression was observed in at least 90% of glandular cells in the middle and luminal portions, whereas weak staining and significant decrease in positivity were detected in the basal portions of the glands. One oestrogen receptor expression pattern resembled that of progesterone receptors.

CONCLUSION

The inverse expression patterns of SOX2 and hormone (especially progesterone) receptors suggest that endometrial epithelial stem/progenitor cells represent a subset of cells that reside in the basal portions of the endometrial glands in both the bovine and porcine endometrium.

The Role of Endometrial Stem/Progenitor Cells in Recurrent Reproductive Failure

Recurrent implantation failure (RIF) and recurrent pregnancy loss (RPL), collectively referred to as recurrent reproductive failure (RRF), are both challenging conditions with many unanswered questions relating to causes and management options. Both conditions are proposed to be related to an aberrant endometrial microenvironment, with different proposed aetiologies related to a restrictive or permissive endometrium for an invading embryo. The impressive regenerative capacity of the human endometrium has been well-established and has led to the isolation and characterisation of several subtypes of endometrial stem/progenitor cells (eSPCs). eSPCs are known to be involved in the pathogenesis of endometrium-related disorders (such as endometriosis) and have been proposed to be implicated in the pathogenesis of RRF. This review appraises the current knowledge of eSPCs, and their involvement in RRF, highlighting the considerable unknown aspects in this field, and providing avenues for future research to facilitate much-needed advances in the diagnosis and management of millions of women suffering with RRF.

Nuclear receptor coactivator-6 is essential for the morphological change of human uterine stromal cell decidualization via regulating actin fiber reorganization

Nuclear receptor coactivator 6 (Ncoa6), a modulator of several nuclear receptors and transcription factors, is essential for the decidualization of endometrial stromal cells in mice. However, the function of Ncoa6 in the human endometrium remains unclear. We investigated its function in the decidualization of human endometrial stromal cells (HESCs) isolated from resected uteri. Knockdown of Ncoa6 was performed using two independent small interfering RNAs. Decidualization was induced in vitro via medroxyprogesterone and cyclic adenosine monophosphate. We compared decidualized cellular morphology between the Ncoa6 knockdown cells and control cells. Messenger RNA (mRNA) sequencing was performed to determine the Ncoa6 target genes in undecidualized HESCs. We found that the knockdown of Ncoa6 caused the failure of morphological changes in decidualized HESCs compared to that in the control cells. mRNA sequencing revealed that Ncoa6 regulates the expression of genes associated with the regulation of actin fibers. Ncoa6 knockdown cells failed to reorganize actin fibers during the decidualization of HESCs. Ncoa6 was shown to play an essential role in decidualization via the appropriate regulation of actin fiber regulation in HESCs. Herein, our in vitro studies revealed a part of the mechanisms involved in endometrial decidualization. Future research is needed to investigate these mechanisms in women with implantation defects.

The fate of human SUSD2+ endometrial mesenchymal stem cells during decidualization

Regeneration of the endometrial stromal compartment in premenopausal women is likely maintained by the perivascular endometrial mesenchymal stem/stromal cells (eMSC) expressing sushi domain containing 2 (SUSD2). The fate of SUSD2+ eMSC during pregnancy and their role in decidualization is not fully known. The aim of our study was to determine the effect of progesterone on the stemness of the SUSD2+ eMSC isolated from non-pregnant uterine samples. Secondary objectives were to characterize the functional capacity including differentiation and clonogenicity assays of SUSD2+ eMSC isolated from decidua at full term and compare it to the capacity of those isolated from non-pregnant uterine samples. Progesterone treatment induced changes in the decidual gene expression profile in non-pregnant SUSD2+ eMSC. Data analysis of a publicly available single cell RNA-seq data set revealed differential expression of several mesenchymal and epithelial signature genes between the SUSD2+ eMSC and the decidual stromal cells, suggesting mesenchymal-to-epithelial transition occurs during decidualization. Histological analysis revealed a significantly lower abundance of SUSD2+ eMSC in 1st trimester and full term samples compared to non-pregnant samples, p = 0.0296 and 0.005, respectively. The differentiation and the colony forming capacity did not differ significantly between the cells isolated from non-pregnant and pregnant uterine samples. Our results suggest that SUSD2+ eMSC undergo decidualization in vitro, while maintaining MSC plasma membrane phenotype. Human eMSC seem to play an important role in the course of endometrial decidualization and embryo implantation. Pregnancy reduced the abundance of SUSD2+ eMSC, however eMSC function remains intact.

Therapeutic role of uterine-derived stem cells in acute kidney injury

BACKGROUND

Acute kidney injury (AKI) causes abrupt deterioration in kidney function that disrupts metabolic, electrolyte and fluid homeostasis. Although the prevalence of AKI is steadily increasing, no definitive treatment options are available, leading to severe morbidity and mortality. We evaluated the role of uterine-derived multipotent stem cells in kidney regeneration after ischemic AKI.

METHODS

Female C57BL/6J mice were hysterectomized and subsequently subject to AKI by either unilateral or bilateral renal ischemia-reperfusion injury. Uterine-derived cells (UDCs), containing a population of uterine stem cells, were isolated from the uteri of female transgenic DsRed mice and injected intravenously to AKI mice. Engraftment of DsRed cells was analyzed by flow cytometry while serum creatinine levels were determined colorimetrically. Expression of UDC markers and cytokine markers were analyzed by immunohistochemical and qRT-PCR methods, respectively. The Kaplan-Meier method was used to analyze survival time while unpaired t test with Welch's correction used for data analysis between two groups.

RESULTS

Mice with an intact uterus, and hence an endogenous source of UDCs, had a higher survival rate after bilateral ischemic AKI compared to hysterectomized mice. Mice treated with infusion of exogenous UDCs after hysterectomy/AKI had lower serum creatinine levels and higher survival rates compared to controls that did not receive UDCs. Engraftment of labeled UDCs was significantly higher in kidneys of bilateral ischemic AKI mice compared to those that underwent a sham surgery. When unilateral ischemic AKI was induced, higher numbers of UDCs were found in the injured than non-injured kidney. Immunofluorescence staining demonstrated double-positive DsRed/Lotus tetragonolobus agglutinin (LTA) positive cells and DsRed/CD31 positive cells indicating contribution of UDCs in renal tubular and vascular regeneration. Expression of Cxcl12, Bmp2, Bmp4, and Ctnf in renal tissue was significantly higher in the UDCs injection group than the control group.

CONCLUSIONS

UDCs engrafted injured kidneys, contributed to proximal tubule and vascular regeneration, improved kidney function and increased survival in AKI mice. UDC administration is a promising new therapy for AKI. Endogenous uterine stem cells likely also preserve kidney function, suggesting a novel interaction between the uterus and kidney. We suggest that hysterectomy may have a detrimental effect on response to renal injury.

Quinagolide Treatment Reduces Invasive and Angiogenic Properties of Endometrial Mesenchymal Stromal Cells

Endometrial mesenchymal stromal cells (E-MSCs) extensively contribute to the establishment and progression of endometrial ectopic lesions through formation of the stromal vascular tissue, and support to its growth and vascularization. As E-MSCs lack oestrogen receptors, endometriosis eradication cannot be achieved by hormone-based pharmacological approaches. Quinagolide is a non-ergot-derived dopamine receptor 2 agonist reported to display therapeutic effects in in vivo models of endometriosis. In the present study, we isolated E-MSCs from eutopic endometrial tissue and from ovarian and peritoneal endometriotic lesions, and we tested the effect of quinagolide on their proliferation and matrix invasion ability. Moreover, the effect of quinagolide on E-MSC endothelial differentiation was assessed in an endothelial co-culture model of angiogenesis. E-MSC lines expressed dopamine receptor 2, with higher expression in ectopic than eutopic ones. Quinagolide inhibited the invasive properties of E-MSCs, but not their proliferation, and limited their endothelial differentiation. The abrogation of the observed effects by spiperone, a dopamine receptor antagonist, confirmed specific dopamine receptor activation. At variance, no involvement of VEGFR2 inhibition was observed. Moreover, dopamine receptor 2 activation led to downregulation of AKT and its phosphorylation. Of interest, several effects were more prominent on ectopic E-MSCs with respect to eutopic lines. Together with the reported effects on endometrial and endothelial cells, the observed inhibition of E-MSCs may increase the rationale for quinagolide in endometriosis treatment.

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.

Understanding menstrual blood-derived stromal/stem cells: Definition and properties. Are we rushing into their therapeutic applications?

Cells with mesenchymal stem cell properties have been identified in menstrual blood and termed menstrual blood-derived stem/stromal cells (MenSCs). MenSCs have been proposed as ideal candidates for cell-based therapy in regenerative medicine and immune-related diseases. However, MenSCs identity has been loosely defined so far and there is controversy regarding their cell markers and differentiation potential. In this review, we outline the origin of MenSCs in the context of regenerating human endometrium, with attention to endometrial eMSCs as reference cells to understand MenSCs. We summarize the cell identity markers analyzed and the immunomodulatory and reparative properties reported. We also address the recent use of MenSCs in cell reprogramming. The main goal of this review is to contribute to the understanding of the identity and properties of MenSCs as well as to identify potential caveats and new venues that deserve to be explored to strengthen their potential applications.

Comparison of Organoids from Menstrual Fluid and Hormone-Treated Endometrium: Novel Tools for Gynecological Research

Endometrial organoids (EMO) are an important tool for gynecological research but have been limited by generation from (1) invasively acquired tissues and thus advanced disease states and (2) from women who are not taking hormones, thus excluding 50% of the female reproductive-aged population. We sought to overcome these limitations by generating organoids from (1) menstrual fluid (MF; MFO) using a method that enables the concurrent isolation of menstrual fluid supernatant, stromal cells, and leukocytes and (2) from biopsies and hysterectomy samples from women taking hormonal medication (EMO-H). MF was collected in a menstrual cup for 4–6 h on day 2 of menstruation. Biopsies and hysterectomies were obtained during laparoscopic surgery. Organoids were generated from all sample types, with MFO and EMO-H showing similar cell proliferation rates, proportion and localization of the endometrial basalis epithelial marker, Stage Specific Embryonic Antigen-1 (SSEA-1), and gene expression profiles. Organoids from different disease states showed the moderate clustering of epithelial secretory and androgen receptor signaling genes. Thus, MFO and EMO-H are novel organoids that share similar features to EMO but with the advantage of (1) MFO being obtained non-invasively and (2) EMO-H being obtained from 50% of the women who are not currently being studied through standard methods. Thus, MFO and EMO-H are likely to prove to be invaluable tools for gynecological research, enabling the population-wide assessment of endometrial health and personalized medicine.

The Diverse Manifestations of Regeneration and Why We Need to Study Them

For hundreds of years, the question of why some organisms can regenerate missing body parts while others cannot has remained poorly understood. This has been due in great part to the inability to genetically, molecularly, and cellularly dissect this problem for most of the history of the field. It has only been in the past 20-30 years that important mechanistic advances have been made in methodologies that introduce loss and gain of gene function in animals that can regenerate. However, we still have a very incomplete understanding of how broadly regenerative abilities may be dispersed across species and whether or not such properties share a common evolutionary origin, which may have emerged independently or both. Understanding regeneration, therefore, will require rigorously practiced fundamental, curiosity-driven, discovery research. Expanding the number of research organisms used to study regeneration allows us to uncover aspects of this problem we may not yet know exist and simultaneously increases our chances of solving this long-standing problem of biology.

Stem cell-based therapy for ameliorating intrauterine adhesion and endometrium injury

Intrauterine adhesion refers to endometrial repair disorders which are usually caused by uterine injury and may lead to a series of complications such as abnormal menstrual bleeding, recurrent abortion and secondary infertility. At present, therapeutic approaches to intrauterine adhesion are limited due to the lack of effective methods to promote regeneration following severe endometrial injury. Therefore, to develop new methods to prevent endometrial injury and intrauterine adhesion has become an urgent need. For severely damaged endometrium, the loss of stem cells in the endometrium may affect its regeneration. This article aimed to discuss the characteristics of various stem cells and their applications for uterine tissue regeneration.

Endometrial SUSD2+ Mesenchymal Stem/Stromal Cells in Tissue Engineering: Advances in Novel Cellular Constructs for Pelvic Organ Prolapse

Cellular therapy is an emerging field in clinical and personalised medicine. Many adult mesenchymal stem/progenitor cells (MSC) or pluripotent derivatives are being assessed simultaneously in preclinical trials for their potential treatment applications in chronic and degenerative human diseases. Endometrial mesenchymal stem/progenitor cells (eMSC) have been identified as clonogenic cells that exist in unique perivascular niches within the uterine endometrium. Compared with MSC isolated from other tissue sources, such as bone marrow and adipose tissue, eMSC can be extracted through less invasive methods of tissue sampling, and they exhibit improvements in potency, proliferative capacity, and control of culture-induced differentiation. In this review, we summarize the potential cell therapy and tissue engineering applications of eMSC in pelvic organ prolapse (POP), emphasising their ability to exert angiogenic and strong immunomodulatory responses that improve tissue integration of novel surgical constructs for POP and promote vaginal tissue healing.

Menstrual fluid endometrial stem/progenitor cell and supernatant protein content: cyclical variation and indicative range

STUDY QUESTION

Does natural variation exist in the endometrial stem/progenitor cell and protein composition of menstrual fluid across menstrual cycles in women?

SUMMARY ANSWER

Limited variation exists in the percentage of some endometrial stem/progenitor cell types and abundance of selected proteins in menstrual fluid within and between a cohort of women.

WHAT IS KNOWN ALREADY

Menstrual fluid is a readily available biofluid that can represent the endometrial environment, containing endometrial stem/progenitor cells and protein factors. It is unknown whether there is natural variation in the cellular and protein content across menstrual cycles of individual women, which has significant implications for the use of menstrual fluid in research and clinical applications.

STUDY DESIGN, SIZE, DURATION

Menstrual fluid was collected from 11 non-pregnant females with regular menstrual cycles. Participants had not used hormonal medications in the previous 3 months. Participants collected menstrual fluid samples from up to five cycles using a silicone menstrual cup worn on Day 2 of menstrual bleeding.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Menstrual fluid samples were centrifuged to separate soluble proteins and cells. Cells were depleted of red blood cells and CD45+ leucocytes. Menstrual fluid-derived endometrial stem/progenitor cells were characterized using multicolour flow cytometry including markers for endometrial stem/progenitor cells N-cadherin (NCAD) and stage-specific embryonic antigen-1 (SSEA-1) (for endometrial epithelial progenitor cells; eEPC), and sushi domain containing-2 (SUSD2) (for endometrial mesenchymal stem cells; eMSC). The clonogenicity of menstrual fluid-derived endometrial cells was assessed using colony forming unit assays. Menstrual fluid supernatant was analyzed using a custom magnetic Luminex assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Endometrial stem/progenitor cells are shed in menstrual fluid and demonstrate clonogenic properties. The intraparticipant agreement for SUSD2+ menstrual fluid-derived eMSC (MF-eMSC), SSEA-1+ and NCAD+SSEA-1+ MF-eEPC, and stromal clonogenicity were moderate-good (intraclass correlation; ICC: 0.75, 0.56, 0.54 and 0.52, respectively), indicating limited variability across menstrual cycles. Endometrial inflammatory and repair proteins were detectable in menstrual fluid supernatant, with five of eight (63%) factors demonstrating moderate intraparticipant agreement (secretory leukocyte protein inhibitor (SLPI), lipocalin-2 (NGAL), lactoferrin, follistatin-like 1 (FSTL1), human epididymis protein-4 (HE4); ICC ranges: 0.57-0.69). Interparticipant variation was limited for healthy participants, with the exception of key outliers of which some had self-reported menstrual pathologies.

LARGE SCALE DATA

N/A. There are no OMICS or other data sets relevant to this study.

LIMITATIONS, REASONS FOR CAUTION

The main limitations to this research relate to the difficulty of obtaining menstrual fluid samples across multiple menstrual cycles in a consistent manner. Several participants could only donate across <3 cycles and the duration of wearing the menstrual cup varied between 4 and 6 h within and between women. Due to the limited sample size used in this study, wider studies involving multiple consecutive menstrual cycles and a larger cohort of women will be required to fully determine the normal range of endometrial stem/progenitor cell and supernatant protein content of menstrual fluid. Possibility for selection bias and true representation of the population of women should also be considered.

WIDER IMPLICATIONS OF THE FINDINGS

Menstrual fluid is a reliable source of endometrial stem/progenitor cells and related endometrial proteins with diagnostic potential. The present study indicates that a single menstrual sample may be sufficient in characterizing a variety of cellular and protein parameters across women's menstrual cycles. The results also demonstrate the potential of menstrual fluid for identifying endometrial and menstrual abnormalities in both research and clinical settings as a non-invasive method for assessing endometrial health.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Australian National Health and Medical Research Council to C.E.G. (Senior Research Fellowship 1024298 and Investigator Fellowship 1173882) and to J.E. (project grant 1047756), the Monash IVF Research Foundation to C.E.G. and the Victorian Government's Operational Infrastructure Support Program. K.A.W., M.L.D.-T., S.G.S. and J.E. declare no conflicts of interest. C.E.G. reports grants from NHMRC, during the conduct of the study; grants from EndoFound USA, grants from Ferring Research Innovation, grants from United States Department of Defence, grants from Clue-Utopia Research Foundation, outside the submitted work. CEF reports grants from EndoFound USA, grants from Clue-Utopia Research Foundation, outside the submitted work.

The Elusive Endometrial Epithelial Stem/Progenitor Cells

The human endometrium undergoes approximately 450 cycles of proliferation, differentiation, shedding and regeneration over a woman's reproductive lifetime. The regenerative capacity of the endometrium is attributed to stem/progenitor cells residing in the basalis layer of the tissue. Mesenchymal stem cells have been extensively studied in the endometrium, whereas endometrial epithelial stem/progenitor cells have remained more elusive. This review details the discovery of human and mouse endometrial epithelial stem/progenitor cells. It highlights recent significant developments identifying putative markers of these epithelial stem/progenitor cells that reveal their in vivo identity, location in both human and mouse endometrium, raising common but also different viewpoints. The review also outlines the techniques used to identify epithelial stem/progenitor cells, specifically in vitro functional assays and in vivo lineage tracing. We will also discuss their known interactions and hierarchy and known roles in endometrial dynamics across the menstrual or estrous cycle including re-epithelialization at menses and regeneration of the tissue during the proliferative phase. We also detail their potential role in endometrial proliferative disorders such as endometriosis.

Single-cell RNA sequencing redefines the mesenchymal cell landscape of mouse endometrium

The endometrium is a dynamic tissue that exhibits remarkable resilience to repeated episodes of differentiation, breakdown, regeneration, and remodeling. Endometrial physiology relies on a complex interplay between the stromal and epithelial compartments with the former containing a mixture of fibroblasts, vascular, and immune cells. There is evidence for rare populations of putative mesenchymal progenitor cells located in the perivascular niche of human endometrium, but the existence of an equivalent cell population in mouse is unclear. We used the Pdgfrb‐BAC‐eGFP transgenic reporter mouse in combination with bulk and single‐cell RNA sequencing to redefine the endometrial mesenchyme. In contrast to previous reports we show that CD146 is expressed in both PDGFRβ + perivascular cells and CD31 + endothelial cells. Bulk RNAseq revealed cells in the perivascular niche which express the high levels of Pdgfrb as well as genes previously identified in pericytes and/or vascular smooth muscle cells (Acta2, Myh11, Olfr78, Cspg4, Rgs4, Rgs5, Kcnj8, and Abcc9). scRNA‐seq identified five subpopulations of cells including closely related pericytes/vascular smooth muscle cells and three subpopulations of fibroblasts. All three fibroblast populations were PDGFRα+/CD34 + but were distinct in their expression of Ngfr/Spon2/Angptl7 (F1), Cxcl14/Smoc2/Rgs2 (F2), and Clec3b/Col14a1/Mmp3 (F3), with potential functions in the regulation of immune responses, response to wounding, and organization of extracellular matrix, respectively. Immunohistochemistry was used to investigate the spatial distribution of these populations revealing F1/NGFR + cells in most abundance beside epithelial cells. We provide the first definitive analysis of mesenchymal cells in the adult mouse endometrium identifying five subpopulations providing a platform for comparisons between mesenchymal cells in endometrium and other adult tissues which are prone to fibrosis.

Characteristics of the human endometrial regeneration cells as a potential source for future stem cell-based therapies: A lab resources study

Background

Human endometrium with consecutive regeneration capability undergoes monthly hormonal changes for probable implantation, which confirms the presence of the cells in the basalis layer known as stem cell.

Objective

Previously, we reported the isolation and culture of the mesenchymal-like cells from human endometrium. In this study, we evaluated the biological and stemness characteristics of these cells.

Materials and Methods

The characterization of Yazd human endometrial-derived mesenchymal stem/stromal cells (YhEnMSCs) was assessed using immunofluorescence (IF) staining for CD105, VIMENTIN, and FIBRONECTIN as markers and RT-PCR for CD166, CD10, CD105, VIMENTIN, FIBRONECTIN, MHCI, CD14, and MHCII genes. Flow cytometry (FACS) was performed for CD44, CD73, CD90, and CD105 markers. Moreover, the differentiation capacity of the YhEnMSCs to the osteoblast and adipocytes was confirmed by Alizarin Red and Oil Red staining.

Results

YhEnMSCs expressed CD105, VIMENTIN, FIBRONECTIN, CD44, CD73, and CD90 markers and CD166, CD10, CD105, VIMENTIN, FIBRONECTIN, and MHCI, but, did not express CD14, MHCII.

Conclusion

Our data confirm previous reports by other groups indicating the application of endometrial cells as an available source of MSCs with self-renewal and differentiation capacity. Accordingly, YhEnMSCs can be used as a suitable source for cell-based therapies.

CD34+KLF4+ Stromal Stem Cells Contribute to Endometrial Regeneration and Repair

The regenerative capacity of the human endometrium requires a population of local stem cells. However, the phenotypes, locations, and origin of these cells are still unknown. In a mouse menstruation model, uterine stromal SM22α⁺-derived CD34⁺KLF4⁺ stem cells are activated and integrate into the regeneration area, where they differentiate and incorporate into the endometrial epithelium; this process is correlated with enhanced protein SUMOylation in CD34⁺KLF4⁺ cells. Mice with a stromal SM22α-specific SENP1 deletion (SENP1smKO) exhibit accelerated endometrial repair in the regeneration model and develop spontaneous uterine hyperplasia. Mechanistic studies suggest that SENP1 deletion induces SUMOylation of ERα, which augments ERα transcriptional activity and proliferative signaling in SM22α⁺CD34⁺KLF4⁺ cells. These cells then transdifferentiate to the endometrial epithelium. Our study reveals that CD34⁺KLF4⁺ stromal-resident stem cells directly contribute to endometrial regeneration, which is regulated through SENP1-mediated ERα suppression.

The regenerative capacity of the human endometrium requires a population of local stem cells. Here, Yin et al. show that uterine stromal SM22α⁺CD34⁺KLF4⁺ stem cells are activated by ERα SUMOylation and integrate into the regeneration area, where they differentiate and incorporate into the endometrial epithelium.

Endometrial and Menstrual Blood Mesenchymal Stem/Stromal Cells: Biological Properties and Clinical Application

A highly proliferative mesenchymal stem/stromal cell (MSC) population was recently discovered in the dynamic, cyclically regenerating human endometrium as clonogenic stromal cells that fulfilled the International Society for Cellular Therapy (ISCT) criteria. Specific surface markers enriching for clonogenic endometrial MSC (eMSC), CD140b and CD146 co-expression, and the single marker SUSD2, showed their perivascular identity in the endometrium, including the layer which sheds during menstruation. Indeed, cells with MSC properties have been identified in menstrual fluid and commonly termed menstrual blood stem/stromal cells (MenSC). MenSC are generally retrieved from menstrual fluid as plastic adherent cells, similar to bone marrow MSC (bmMSC). While eMSC and MenSC share several biological features with bmMSC, they also show some differences in immunophenotype, proliferation and differentiation capacities. Here we review the phenotype and functions of eMSC and MenSC, with a focus on recent studies. Similar to other MSC, eMSC and MenSC exert immunomodulatory and anti-inflammatory impacts on key cells of the innate and adaptive immune system. These include macrophages, T cells and NK cells, both in vitro and in small and large animal models. These properties suggest eMSC and MenSC as additional sources of MSC for cell therapies in regenerative medicine as well as immune-mediated disorders and inflammatory diseases. Their easy acquisition via an office-based biopsy or collected from menstrual effluent makes eMSC and MenSC attractive sources of MSC for clinical applications. In preparation for clinical translation, a serum-free culture protocol was established for eMSC which includes a small molecule TGFβ receptor inhibitor that prevents spontaneous differentiation, apoptosis, senescence, maintains the clonogenic SUSD2+ population and enhances their potency, suggesting potential for cell-therapies and regenerative medicine. However, standardization of MenSC isolation protocols and culture conditions are major issues requiring further research to maximize their potential for clinical application. Future research will also address crucial safety aspects of eMSC and MenSC to ensure these protocols produce cell products free from tumorigenicity and toxicity. Although a wealth of data on the biological properties of eMSC and MenSC has recently been published, it will be important to address their mechanism of action in preclinical models of human disease.

Endometriosis and nuclear receptors

BACKGROUND

Endometriosis is recognized as a steroid-dependent disorder; however, the precise roles of nuclear receptors (NRs) in steroid responsiveness and other signaling pathways are not well understood.

OBJECTIVE AND RATIONALE

Over the past several years, a number of paradigm-shifting breakthroughs have occurred in the area of NRs in endometriosis. We review and clarify new information regarding the mechanisms responsible for: (i) excessive estrogen biosynthesis, (ii) estrogen-dependent inflammation, (iii) defective differentiation due to progesterone resistance and (iv) enhanced survival due to deficient retinoid production and action in endometriosis. We emphasize the roles of the relevant NRs critical for these pathological processes in endometriosis.

SEARCH METHODS

We conducted a comprehensive search using PubMed for human, animal and cellular studies published until 2018 in the following areas: endometriosis; the steroid and orphan NRs, estrogen receptors alpha (ESR1) and beta (ESR2), progesterone receptor (PGR), steroidogenic factor-1 (NR5A1) and chicken ovalbumin upstream promoter-transcription factor II (NR2F2); and retinoids.

OUTCOMES

Four distinct abnormalities in the intracavitary endometrium and extra-uterine endometriotic tissue underlie endometriosis progression: dysregulated differentiation of endometrial mesenchymal cells, abnormal epigenetic marks, inflammation activated by excess estrogen and the development of progesterone resistance. Endometriotic stromal cells compose the bulk of the lesions and demonstrate widespread epigenetic abnormalities. Endometriotic stromal cells also display a wide range of abnormal NR expression. The orphan NRs NR5A1 and NR2F2 compete to regulate steroid-synthesizing genes in endometriotic stromal cells; NR5A1 dominance gives rise to excessive estrogen formation. Endometriotic stromal cells show an abnormally low ESR1:ESR2 ratio due to excessive levels of ESR2, which mediates an estrogen-driven inflammatory process and prostaglandin formation. These cells are also deficient in PGR, leading to progesterone resistance and defective retinoid synthesis. The pattern of NR expression, involving low ESR1 and PGR and high ESR2, is reminiscent of uterine leiomyoma stem cells. This led us to speculate that endometriotic stromal cells may display stem cell characteristics found in other uterine tissues. The biologic consequences of these abnormalities in endometriotic tissue include intense inflammation, defective differentiation and enhanced survival.

WIDER IMPLICATIONS

Steroid- and other NR-related abnormalities exert genome-wide biologic effects via interaction with defective epigenetic programming and enhance inflammation in endometriotic stromal cells. New synthetic ligands, targeting PGR, retinoic acid receptors and ESR2, may offer novel treatment options.

Regenerative Potential of Menstrual Blood-Derived Stem Cells and Platelet-Derived Growth Factor in Endometrial Injury

Background

Endometrial regeneration is essential for normal endometrial function; however, it is unclear whether and how menstrual blood-derived stem cells (MenSCs) and platelet-derived growth factor (PGDF) are associated with this phenomenon. The present study explored this topic.

Material/Methods

EM-E6/E7/hTERT cells were divided into 5 groups: control group, NC group, PDGF group, MenSCs group, and PDGF+MenSCs group. The effects of MenSCs and PDGF on cell proliferation, invasion, and microvascular formation of endometrial epithelium were investigated by CCK-8, Transwell, and tube formation assays, respectively. Mouse endometrial injury models were established and mice were randomly divided into control, model, PDGF, MenSCs, and PDGF+MenSCs groups. Pathological change was examined with hematoxylin and eosin (H&E) staining. Microvessel formation of endometrial epithelium was estimated by detecting the expression of CD34 protein with immunohistochemical (IHC) staining. Western blot analysis was used to detect the activation of Akt and Bad proteins in endometrial tissue.

Results

MenSCs, PDGF, and the combination treatments significantly promoted the proliferation, migration, and tube formation of endometrial epithelium compared to the control and NC group. The combination of MenSCs and PDGF remarkably promoted re-epithelialization and endometrial repair. IHC staining analysis showed significant increases in CD34 expression of the endometrial tissue following treatment with PDGF and MenSCs. The combination treatments also markedly enhanced the phosphorylation of Akt and Bad in endometrial tissue.

Conclusions

These results suggest that MenSCs and PDGF may be candidate substances for endometrial injury repair.

Partial regeneration of uterine horns in rats through adipose-derived stem cell sheets

Severe uterine damage and infection lead to intrauterine adhesions, which result in hypomenorrhea, amenorrhea and infertility. Cell sheet engineering has shown great promise in clinical applications. Adipose-derived stem cells (ADSCs) are emerging as an alternative source of stem cells for cell-based therapies. In the present study, we investigated the feasibility of applying ADSCs as seed cells to form scaffold-free cell sheet. Data showed that ADSC sheets expressed higher levels of FGF, Col I, TGFβ, and VEGF than ADSCs in suspension, while increased expression of this gene set was associated with stemness, including Nanog, Oct4, and Sox2. We then investigated the therapeutic effects of 3D ADSCs sheet on regeneration in a rat model. We found that ADSCs were mainly detected in the basal layer of the regenerating endometrium in the cell sheet group at 21 days after transplantation. Additionally, some ADSCs differentiated into stromal-like cells. Moreover, ADSC sheets transplanted into partially excised uteri promoted regeneration of the endometrium cells, muscle cells and stimulated angiogenesis, and also resulted in better pregnancy outcomes. Therefore, ADSC sheet therapy shows considerable promise as a new treatment for severe uterine damage.

Challenges in Clinical Development of Mesenchymal Stromal/Stem Cells: Concise Review

Identified 50 years ago, mesenchymal stromal/stem cells (MSCs) immediately generated a substantial interest among the scientific community because of their differentiation plasticity and hematopoietic supportive function. Early investigations provided evidence of a relatively low engraftment rate and a transient benefit for challenging congenital and acquired diseases. The reasons for these poor therapeutic benefits forced the entire field to reconsider MSC mechanisms of action together with their ex vivo manipulation procedures. This phase resulted in advances in MSCs processing and the hypothesis that MSC‐tissue supportive functions may be prevailing their differentiation plasticity, broadening the spectrum of MSCs therapeutic potential far beyond their lineage‐restricted commitments. Consequently, an increasing number of studies have been conducted for a variety of clinical indications, revealing additional challenges and suggesting that MSCs are still lagging behind for a solid clinical translation. For this reason, our aim was to dissect the current challenges in the development of still promising cell types that, after more than half a century, still need to reach their maturity. stem cells translational medicine2019;8:1135–1148

Hormonal oral contraceptive influence on isolation, Characterization and cryopreservation of mesenchymal stem cells from menstrual fluid

The purpose of the study was to evaluate whether the intake of hormonal oral contraceptive influences the viability of mesenchymal stem cell. Sixteen healthy female volunteers with regular menstrual cycles were invited to participate. Menstrual fluid was collected on the day of maximum flux, and collected cells were analyzed by a 'minimal standard' for MSC characterization: plastic adherence, trilineage (adipogenic, osteogenic, chondrogenic) in vitro differentiation and a minimalistic panel of markers assessed by flow cytometry (CD731, CD901, CD1051, CD34-, CD45-) using monoclonal antibodies. The participants were divided into two groups: Group 1 - no hormonal contraceptive use; Group 2 - hormonal oral contraceptive use. The median of the menstrual fluid volume was 5.0 and the median number of cells was 5.2 × 10⁶. Median of cell viability was 89.3%. After culture, mesenchymal stem cells increased from 0.031% of the total cells to 96.9%. The cells formed clusters and reached confluence after 15-21 days of culture in the first passage. In the second passage, clusters and the confluence were observed after 3 days of culture. No difference was observed between the groups. Our data suggest that oral hormonal contraceptive intake maintains the viability of mesenchymal stem cells from menstrual fluid.

Transplantation of human endometrial perivascular cells with elevated CYR61 expression induces angiogenesis and promotes repair of a full-thickness uterine injury in rat

Background

Disruptions of angiogenesis can have a significant effect on the healing of uterine scars. Human endometrial perivascular cells (CD146+PDGFRβ+) function as stem cells in the endometrium. Cysteine-rich angiogenic inducer 61 (CYR61) plays an important role in vascular development. The purpose of this study was to observe the effects of the transplantation of human endometrial perivascular cells (En-PSCs) overexpressing CYR61 on structural and functional regeneration in rat models of partial full-thickness uterine excision.

Methods

We first sorted human En-PSCs from endometrial single-cell suspensions by flow cytometry. Human En-PSCs expressing low or high levels of CYR61 were then generated via transfection with a CYR61-specific small interfering ribonucleic acid (si-CYR61) construct or overexpression plasmid. To establish a rat model of uterine injury, a subset of uterine wall was then resected from each uterine horn in experimental animals. Female rats were randomly assigned to five groups, including a sham-operated group and four repair groups that received either PBS loaded on a collagen scaffold (collagen/PBS), En-PSCs loaded on a collagen scaffold (collagen/En-PSCs), En-PSCs with low CYR61 expression loaded on a collagen scaffold (collagen/si-CYR61 En-PSCs), and En-PSCs overexpressing CYR61 loaded on a collagen scaffold (collagen/ov-CYR61 En-PSCs). These indicated constructs were sutured in the injured uterine area to replace the excised segment. On days 30 and 90 after transplantation, a subset of rats in each group was sacrificed, and uterine tissue was recovered and serially sectioned. Hematoxylin and eosin staining and immunohistochemical staining were then performed. Finally, the remaining rats of each group were mated with fertile male rats on day 90 for a 2-week period.

Results

Sorted En-PSCs expressed all recognized markers of mesenchymal stem cells (MSCs), including CD10, CD13, CD44, CD73, CD90, and CD105, and exhibited differentiation potential toward adipocytes, osteoblasts, and neuron-like cells. Compared with En-PSCs and En-PSCs with low CYR61 expression, En-PSCs with elevated CYR61 expression enhanced angiogenesis by in vitro co-culture assays. At day 90 after transplantation, blood vessel density in the collagen/ov-CYR61 En-PSCs group (11.667 ± 1.287) was greater than that in the collagen/En-PSCs group (7.167 ± 0.672) (P < 0.05) and the collagen/si-CYR61 En-PSCs group (3.750 ± 0.906) (P < 0.0001). Pregnancy rates differed among groups, from 40% in the collagen/PBS group to 80% in the collagen/En-PSCs group, 12.5% in the collagen/si-CYR61 En-PSCs group, and 80% in the collagen/ov-CYR61 En-PSCs group. In addition, four embryos were evident in the injured uterine horns of the collagen/ov-CYR61 En-PSCs group, while no embryos were identified in the injured uterine horns of the collagen/PBS group.

Conclusions

The results showed that CYR61 plays an important role in angiogenesis. Collagen/ov-CYR61 En-PSCs promoted endometrial and myometrial regeneration and induced neovascular regeneration in injured rat uteri. The pregnancy rate of rats treated with transplantation of collagen/En-PSCs or collagen/ov-CYR61 En-PSCs was improved. Moreover, the number of embryos implantation on the injured area in uterus was increased after transplantation of collagen/ov-CYR61 En-PSCs.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1272-3) contains supplementary material, which is available to authorized users.

Cell and biomaterial-based approaches to uterus regeneration

Asherman's syndrome (AS) is an endometrial disorder in which intrauterine adhesions crowd the uterine cavity and wall. The fibrotic adhesions are primarily the result of invasive uterine procedures that usually involve the insertion of surgical equipment into the uterus. This syndrome is accompanied by a number of clinical manifestations, including irregular or painful menstruation and infertility. The most prevalent treatment is hysteroscopy, which involves the physical removal of the fibrous strands. Within the last decade, however, the field has been exploring the use of cell-based therapeutics, in conjunction with biomaterials, to treat AS. This review is a recapitulation of the literature focused on cellular therapies for treating AS.

Uterine stem cells: from basic research to advanced cell therapies

BACKGROUND

Stem cell research in the endometrium and myometrium from animal models and humans has led to the identification of endometrial/myometrial stem cells and their niches. This basic knowledge is beginning to be translated to clinical use for incurable uterine pathologies. Additionally, the implication of bone marrow-derived stem cells (BMDSCs) in uterine physiology has opened the field for the exploration of an exogenous and autologous source of stem cells.

OBJECTIVE AND RATIONALE

In this review, we outline the progress of endometrial and myometrial stem/progenitor cells in both human and mouse models from their characterization to their clinical application, indicating roles in Asherman syndrome, atrophic endometrium and tissue engineering, among others.

SEARCH METHODS

A comprehensive search of PubMed and Google Scholar up to December 2017 was conducted to identify peer-reviewed literature related to the contribution of bone marrow, endometrial and myometrial stem cells to potential physiological regeneration as well as their implications in pathologies of the human uterus.

OUTCOMES

The discovery and main characteristics of stem cells in the murine and human endometrium and myometrium are presented together with the relevance of their niches and cross-regulation. The current state of advanced stem cell therapy using BMDSCs in the treatment of Asherman syndrome and atrophic endometrium is analyzed. In the myometrium, the understanding of genetic and epigenetic defects that result in the development of tumor-initiating cells in the myometrial stem niche and thus contribute to the growth of uterine leiomyoma is also presented. Finally, recent advances in tissue engineering based on the creation of novel three-dimensional scaffolds or decellularisation open up new perspectives for the field of uterine transplantation.

WIDER IMPLICATIONS

More than a decade after their discovery, the knowledge of uterine stem cells and their niches is crystalising into novel therapeutic approaches aiming to treat with cells those conditions that cannot be cured with drugs, particularly the currently incurable uterine pathologies. Additional work and improvements are needed, but the basis has been formed for this therapeutic application of uterine cells.

Bovine endometrial MSC: mesenchymal to epithelial transition during luteolysis and tropism to implantation niche for immunomodulation

Background

The uterus is a histologically dynamic organ, and the mechanisms coordinating its regeneration during the oestrous cycle and implantation are poorly understood.

The aim of this study was to isolate, immortalize and characterize bovine endometrial mesenchymal stem cell (eMSC) lines from different oestrous cycle stages (embryo in the oviduct, embryo in the uterus or absence of embryo) and examine their migratory and immunomodulatory properties in an inflammatory or implantation-like environment, as well as possible changes in cell transdifferentiation.

Methods

eMSCs were isolated and analysed in terms of morphological features, expression of cell surface and intracellular markers of pluripotency, inmunocytochemical analyses, alkaline phosphatase activity, proliferation and osteogenic or chondrogenic differentiation capacities, as well as their ability to migrate in response to inflammatory (TNF-α or IL-1β) or implantation (IFN-τ) cytokines and their immunomodulatory effect in the proliferation of T cells.

Results

All eMSCs showed MSC properties such as adherence to plastic, high proliferative capacity, expression of CD44 and vimentin, undetectable expression of CD34 or MHCII, positivity for Pou5F1 and alkaline phosphatase activity. In the absence of an embryo, eMSC showed an apparent mesenchymal to epithelial transition state. eMSC during the entire oestrous cycle differentiated to osteogenic or chondrogenic lineages, showed the ability to suppress T cell proliferation and showed migratory capacity towards pro-inflammatory signal, while responded with a block in their migration to the embryo-derived pregnancy signal.

Conclusion

This study describes for the first time the isolation, immortalization and characterization of bovine mesenchymal stem cell lines from different oestrous cycle stages, with a clear mesenchymal pattern and immunomodulatory properties. Our study also reports that the migratory capacity of the eMSC was increased towards an inflammatory niche but was reduced in response to the expression of implantation cytokine by the embryo. The combination of both signals (pro-inflammatory and implantation) would ensure the retention of eMSC in case of pregnancy, to ensure the immunomodulation necessary in the mother for embryo survival. In addition, in the absence of an embryo, eMSC showed an apparent mesenchymal to epithelial transition state.

Comparison of CD9 & CD146 markers in endometrial stromal cells of fertile & infertile females

Background & objectives

CD9 and CD146 are important adhesion molecules that play a role in the implantation of an embryo. This study was undertaken to correlate the expression of these markers in fertile and infertile women's endometrial stromal cells.

Methods

Human endometrial stromal cell culture from endometrial biopsies of fertile (n=50) and infertile females (n=50) was performed and primary cell lines were established. Expression of CD9 and CD146 was studied for all the 100 cell lines with the help of flow cytometry. Gene expression of CD9 and CD146 was performed by real-time polymerase chain reaction.

Results

There was a significant difference in endometrial stromal cells of fertile and infertile females. Flow cytometric results revealed significantly lower expression of CD9 (P=0.0126) and CD146 (P=0.0006) in the infertile endometrial stromal cells as compared to fertile endometrial stromal cells. These results were comparable with real-time data.

Interpretation & conclusions

This study showed that endometrial stromal cells from infertile females had lower expression of adhesion molecules, CD9 and CD146. Our findings suggest that CD9 and CD146 may have a role in infertility. Infertile female's endometrial stromal cells have decreased expression of CD9 and CD146 which can be the cause of infertility related to implantation failure.

The Fate of Autologous Endometrial Mesenchymal Stromal Cells After Application in the Healthy Equine Uterus

Because of their distinct differentiation, immunomodulatory, and migratory capacities, endometrial mesenchymal stromal cells (MSCs) may provide an optimum source of therapeutic cells not only in relation to the uterus but also for regeneration of other tissues. This study reports the fate of endometrial MSCs following intrauterine application in mares. Stromal cell fractions were isolated from endometrial biopsies taken from seven reproductively healthy mares, expanded, and fluorescence labeled in culture. Phosphate-buffered saline (PBS) or MSCs (15 × 10⁶) were autologously infused into each uterine horn during early diestrus and subsequently tracked by fluorescence microscopy and flow cytometry of endometrial biopsies and blood samples taken periodically after infusion. The inflammatory response to cell infusion was monitored in endometrial cytology samples. MSCs were detected in endometrial sections at 6, 12, and 24 h, but not later (7 or 14 days), after cell infusion. Cells were in all cases located in the uterine lumen, never within the endometrial tissue. No fluorescence signal was detected in blood samples at any time point after infusion. Cytology analyses showed an increase in % of polymorphonuclear neutrophils between 1 and 3 h after uterine infusion with either MSCs or PBS and a further increase by 6 h only in mares infused with PBS. In summary, endometrial MSCs were detected in the uterine lumen for up to 24 h after infusion, but did not migrate into the healthy endometrium. Moreover, MSCs effectively attenuated the inflammatory response to uterine infusion. We conclude that endometrial MSCs obtained from routine uterine biopsies could provide a safe and effective cell source for treatment of inflammatory conditions of the uterus and potentially other tissues.

N-cadherin identifies human endometrial epithelial progenitor cells by in vitro stem cell assays

STUDY QUESTION

Is there a specific surface marker that identifies human endometrial epithelial progenitor cells with adult stem cell activity using in vitro assays?

SUMMARY ANSWER

N-cadherin isolates clonogenic, self-renewing human endometrial epithelial progenitor cells with high proliferative potential that differentiate into cytokeratin+ gland-like structures in vitro and identifies their location in some cells of gland profiles predominantly in basalis endometrium adjacent to the myometrium.

WHAT IS KNOWN ALREADY

Human endometrium contains a small population of clonogenic, self-renewing epithelial cells with high proliferative potential that differentiate into large gland-like structures, but their identity and location is unknown. Stage-specific embryonic antigen-1 (SSEA-1) distinguishes the epithelium of basalis from functionalis and is a marker of human post-menopausal (Post-M) endometrial epithelium.

STUDY DESIGN, SIZE, DURATION

Prospective observational study of endometrial epithelial cells obtained from hysterectomy samples taken from 50 pre-menopausal (Pre-M) and 24 Post-M women, of which 4 were from women who had taken daily estradiol valerate 2 mg/day for 8 weeks prior.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Gene profiling was used to identify differentially expressed surface markers between fresh EpCAM (Epithelial Cell Adhesion Molecule)-magnetic bead-selected basalis-like epithelial cells from Post-M endometrium compared with predominantly functionalis epithelial cells from Pre-M endometrium and validated by qRT-PCR. In vitro clonogenicity and self-renewal assays were used to assess the stem/progenitor cell properties of magnetic bead-sorted N-cadherin+ and N-cadherin- epithelial cells. The cellular identity, location and phenotype of N-cadherin+ cells was assessed by dual colour immunofluorescence and confocal microscopy for cytokeratin, proliferative status (Ki-67), ERα, SSEA-1, SOX9 and epithelial mesenchymal transition (EMT) markers on full thickness human endometrium.

MAIN RESULTS AND THE ROLE OF CHANCE

CDH2 (N-cadherin gene) was one of 11 surface molecules highly expressed in Post-M compared to Pre-M endometrial epithelial cells. N-cadherin+ cells comprise a median 16.7% (n = 8) and 20.2% (n = 5) of Pre-M endometrial epithelial cells by flow cytometry and magnetic bead sorting, respectively. N-cadherin+ epithelial cells from Pre-M endometrium were more clonogenic than N-cadherin- cells (n = 12, P = 0.003), underwent more population doublings (n = 7), showed greater capacity for serial cloning (n = 7) and differentiated into cytokeratin+ gland-like organoids. N-cadherin immunolocalised to the lateral and apical membrane of epithelial cells in the bases of glands in the basalis of Pre-M endometrium and Post-M gland profiles, co-expressing cytokeratin, ERα but not SSEA-1 or SOX9, which localized on gland profiles proximal to N-cadherin+ cells. N-cadherin+ cells were quiescent (Ki-67-) in the basalis and in Post-M endometrial glands and co-localized with EMT markers vimentin and E-cadherin.

LARGE SCALE DATA

The raw and processed data files from the gene microarray have been deposited in the National Center for Biotechnology Information Gene Expression Omnibus data set with accession number GSE35221.

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive study in human endometrium only using in vitro stem cell assays. The differential ability of N-cadherin+ and N-cadherin-cells to generate endometrial glands in vivo was not determined. A small number of uterine tissues analysed contained adenomyosis for which N-cadherin has been implicated in epithelial-EMT.

WIDER IMPLICATIONS OF THE FINDINGS

A new marker enriching for human endometrial epithelial progenitor cells identifies a different and potentially more primitive cell population than SSEA-1, suggesting a potential hierarchy of epithelial differentiation in the basalis. Using N-cadherin as a marker, the molecular and cellular characteristics of epithelial progenitor cells and their role in endometrial proliferative disorders including endometriosis, adenomyosis and thin dysfunctional endometrium can be investigated.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by Cancer Council Victoria grant 491079 (C.E.G.) and Australian National Health and Medical Research Council grants 1021127 (C.E.G.), 1085435 (C.E.G., J.A.D.), 145780 and 288713 (C.N.S.), RD Wright Career Development Award 465121 (C.E.G.), Senior Research Fellowship 1042298 (C.E.G.), the Victorian Government's Operational Infrastructure Support and an Australian Postgraduate Award (HPTN), and China Council Scholarship (L.X.). The authors have nothing to declare.

Human menstrual blood-derived stem cells promote the repair of impaired endometrial stromal cells by activating the p38 MAPK and AKT signaling pathways

Multiple studies have confirmed that human menstrual blood-derived stem cells (MenSCs) have potential applications in regenerative medicine or cell therapy. However, the contribution of MenSCs to endometrial repair is currently unknown. We evaluated the protective effects of MenSCs on impaired endometrial stromal cells (ESCs), as well as the signaling pathways involved in this process. Mifepristone was used to damage human ESCs, which were subsequently cocultured with MenSCs. The proliferation, apoptosis, and migration of ESCs were assessed, together with the expression of related signaling proteins including total p38 mitogen-activated protein kinase, P-p38, total protein kinase B (AKT), P-AKT, β-catenin, and vascular endothelial growth factor (VEGF). MenSCs significantly recovered the proliferation and migration ability of impaired ESCs, inhibited ESC apoptosis, and upregulated protein expression of P-AKT, P-p38, VEGF, and β-catenin. Our findings suggest that MenSC-based therapies could be promising strategies for the treatment of endometrial injury, and that AKT and p38 signaling pathways may be involved in this process.

Molecular and Cellular Pathogenesis of Endometriosis

BACKGROUND

A substantial body of studies supports the view that molecular and cellular features of endometriotic lesions differ from those of eutopic endometrium. Apart from that, evidence exists that the eutopic endometrium from pa-tients with endometriosis differs from that of females without endometriosis.

OBJECTIVE

Aberrant expression profiles include a number of non-steroid signaling pathways that exert their putative influ-ence on the pathogenesis of endometriosis at least in part via crosstalk(s) with estrogen-mediated mechanisms. A rational to focus research on non-steroid signal pathways is that they might be remunerative targets for the development and selection of novel therapeutics to treat endometriosis possibly without affecting estrogen levels.

RESULTS AND CONCLUSION

In this article, we describe molecular and cellular features of endometriotic lesions and focus on the canonical WNT/β-signaling pathway, a key regulatory system in biology (including stem cell homeostasis) and often in pathophysiological conditions such as endometriosis. Recently emerged novel biological concepts in signal transduction and gene regulation like exosomes and microRNAs are discussed in their putative role in the pathogenesis of endometriosis.

Oestrogen, progesterone and stem cells: the discordant trio in endometriosis?

Oestrogen–progesterone signalling is highly versatile and critical for the maintenance of healthy endometrium in humans. The genomic and nongenomic signalling cascades initiated by these hormones in differentiated cells of endometrium have been the primary focus of research since 1920s. However, last decade of research has shown a significant role of stem cells in the maintenance of a healthy endometrium and the modulatory effects of hormones on these cells. Endometriosis, the growth of endometrium outside the uterus, is very common in infertile patients and the elusiveness in understanding of disease pathology causes hindrance in selection of treatment approaches to enhance fertility. In endometriosis, the stem cells are dysfunctional as it can confer progesterone resistance to their progenies resulting in disharmony of hormonal orchestration of endometrial homeostasis. The bidirectional communication between stem cell signalling pathways and oestrogen–progesterone signalling is found to be disrupted in endometriosis though it is not clear which precedes the other. In this paper, we review the intricate connection between hormones, stem cells and the cross-talks in their signalling cascades in normal endometrium and discuss how this is deregulated in endometriosis. Re-examination of the oestrogen–progesterone dependency of endometrium with a focus on stem cells is imperative to delineate infertility associated with endometriosis and thereby aid in designing better treatment modalities.

Mesenchymal endometrial stem/stromal cells for hard tissue engineering: a review of in vitro and in vivo evidence

Hard tissues including teeth, bone and cartilage have inability or poor capacity to self-renew, especially in large defects. Therefore, repair of damages in these tissues represents a huge challenge in the medical field today. Hard tissue engineering commonly utilizes different stem cell sources as a promising strategy for treating bone, cartilages and tooth defects or disorders. Decades ago, researchers successfully isolated and identified endometrial mesenchymal stem/stromal cells (EnSCs) and discovered their multidifferentiation potential. Current studies suggest that EnSCs have significant advantages compared with stem cells derived from other tissues. In this review article, we summarize the current in vitro and in vivo studies that utilize EnSCs or menstrual blood-derived stem cells for differentiation to osteoblasts, odontoblasts or chondroblasts in an effort to realize the potential of these cells in hard tissues regeneration.

Endometritis and In Vitro PGE2 Challenge Modify Properties of Cattle Endometrial Mesenchymal Stem Cells and Their Transcriptomic Profile

Mesenchymal stem cells (MSCs) were isolated and characterized from postpartum bovine endometrium of animals with subclinical (n = 5) and clinical endometritis (n = 3) and healthy puerperal females (n = 5). Cells isolated displayed mean morphological features of MSCs and underwent osteogenic, chondrogenic, and adipogenic differentiation after induction (healthy and subclinical). Cells from cows with clinical endometritis did not undergo adipogenic differentiation. All cells expressed mRNAs for selected MSC markers. Endometrial MSCs were challenged in vitro with PGE₂ at concentrations of 0, 1, 3, and 10 μM, and their global transcriptomic profile was studied. Overall, 1127 genes were differentially expressed between unchallenged cells and cells treated with PGE₂ at all concentrations (763 up- and 364 downregulated, fold change > 2, and P < 0.05). The pathways affected the most by the PGE₂ challenge were immune response, angiogenesis, and cell proliferation. In conclusion, we demonstrated that healthy puerperal bovine endometrium contains MSCs and that endometritis modifies and limits some functional characteristics of these cells, such as their ability to proceed to adipogenic differentiation. Also, PGE₂, an inflammatory mediator of endometritis, modifies the transcriptomic profile of endometrial MSCs. A similar situation may occur during inflammation associated with endometritis, therefore affecting the main properties of endometrial MSCs.

Icaritin inhibits decidualization of endometrial stromal cells

The aim of the present study was to investigate the effects of Icaritin on the proliferation and decidualization of endometrial stromal cells (ESCs). A total of 20 specimens of endometrium were collected during hysterectomy at the Gynecology Department of Shenzhen Nanshan People's Hospital (Shenzhen, China) between August 2014 and December 2015. The endometrium was digested with high concentrations of collagenase and DNase and filtered with meshes, and then the glandular epithelial and stromal cells were separated by the adhesion purification method. The purity of stromal cells was identified by vimetin and cytokeratin 7 immunostaining. The estradiol + progesterone (E2+P4) and/or cyclic adenosine monophosphate (cAMP) were added to induce an in vitro decidualization model, which was used to analyze the effect of Icaritin on the decidualization ability of the human ESCs. The decidualization markers of human ESCs, prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP-1), was analyzed by reverse-transcription quantitative polymerase chain reaction measurements of the mRNA levels, PRL immunostaining and ELISA analysis of the IGFBP-1 protein levels in the cells or cell culture supernatant separately. The results demonstrated that treatment with E2+P4 and/or cAMP for 96 h was able to induce decidualization in ESCs, and that the cells demonstrated polygon-shaped epithelioid changes. The cell nuclei revealed multinuclear changes, and the cells were also observed to be large and round in shape. The PRL expression and upregulated IGFBP-1 mRNA and protein levels in the E2+P4+cAMP treatment group indicated successful decidualization of the in vitro model. However, the addition of Icaritin inhibited the expression of PRL and IGFBP-1 mRNA, as well as IGFBP-1 protein in the induced ESCs compared with groups without Icaritin. These results suggest that Icaritin was able to inhibit the expression of decidualization-related genes in ESCs in vitro. However, the exact mechanisms require further investigation.

Equine mesenchymal stem cells derived from endometrial or adipose tissue share significant biological properties, but have distinctive pattern of surface markers and migration

Adult stromal mesenchymal stem cells (MSCs) have been postulated as responsible for cell renewal in highly and continuously regenerative tissues such as the endometrium. MSCs have been identified in the endometrium of many species including humans, rodents, pets and some farm animals, but not in horses. The objective of this work was to isolate such cells from the endometrium of mares and to compare their main biological attributes with horse adipose-derived MSCs. Here we successfully isolated and characterized endometrial MSCs (eMSCs) from mares. Said cells showed fibroblast-like morphology, grew on plastic, had doubling population times of 46.4 ± 3.38 h, underwent tri-lineage (osteo, chondro and adipogenic) differentiation after appropriate inductions, migrated toward the attraction of fetal calf serum and displayed a pattern of surface markers commonly accepted for horse MSCs. All these are properties of MSCs. Some of these attributes were shared with equine adipose-derived MSCs, but the migration pattern of eMSC at 12 and 24 h after stimulation was reduced in comparison with adipose MSCs. Also, expression of CD44, CD90 and MHCI surface markers were dramatically down-regulated in eMSCs. In conclusion, equine-derived endometrial MSC share biological attributes with adipose MSC of this species, but displayed a different surface marker phenotype and an impaired migration ability. Conceivably, this phenotype is distinctive for MSC of this origin.