Human Endometrium Research Articles

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.

Differences in the Active Endometrial Microbiota across Body Weight and Cancer in Humans and Mice.

Simple SummaryOf all cancers, endometrial cancer has the greatest association with obesity. Obesity causes dysbiosis of intestinal microbiota, but little is known about whether obesity is associated with dysbiosis of the female genital tract. Therefore, the aim of this study was to determine whether obesity and cancer were associated with altered microbiota profiles in the endometrium. 16S rRNA transcript amplicon sequencing (which captures actively replicating bacteria) of endometrial tissues showed that obesity and cancer were associated with the prevalence of microbial community types in the human endometrium. However, obesity was not associated with microbial community types in the mouse endometrium. The presence of endometrial cancer (but not obesity) was associated with decreased abundance of the Lactobacillus genus in the human endometrium. In mice, an enrichment of Lactobacillus was associated with lower prevalence of disease (normal uterine histology). These results suggest that obesity and cancer may influence microbiota community types in the endometrium (at least in humans) and Lactobacillus may be protective in the endometrium. This study therefore supports further research into the role of microbiota in endometrial cancer development.Obesity is a risk factor for endometrial cancer. The aim of this study was to determine whether actively replicating microbiota in the endometrium differ between obese vs. lean and cancer vs. benign states. We performed 16S rRNA amplicon sequencing on endometrial tissues from lean and obese women with and without endometrial cancer, and lean and obese mice. Results displayed human endometrial microbiota clustered into three community types (R = 0.363, p = 0.001). Lactobacillus was dominant in community type 1 (C1) while community type 2 (C2) had high levels of Proteobacteria and more cancer samples when compared to C1 (p = 0.007) and C3 (p = 0.0002). A significant increase in the prevalence of the C2 community type was observed across body mass index and cancer (χ2 = 14.24, p = 0.0002). The relative abundance of Lactobacillus was lower in cancer samples (p = 0.0043), and an OTU with 100% similarity to Lactobacillus iners was enriched in control samples (p = 0.0029). Mouse endometrial microbiota also clustered into three community types (R = 0.419, p = 0.001) which were not influenced by obesity. In conclusion, obesity and cancer are associated with community type prevalence in the human endometrium, and Lactobacillus abundance is associated with normal uterine histologies in humans and mice.

Hypoxia Regulates the Self-Renewal of Endometrial Mesenchymal Stromal/Stem-like Cells via Notch Signaling.

Human endometrium is an incredibly dynamic tissue undergoing cyclic regeneration and shedding during a woman’s reproductive life. Endometrial mesenchymal stromal/stem-like cells (eMSC) contribute to this process. A hypoxic niche with low oxygen levels has been reported in multiple somatic stem cell types. However, the knowledge of hypoxia on eMSC remains limited. In mice, stromal stem/progenitor cells can be identified by the label-retaining technique. We examined the relationship between the label-retaining stromal cells (LRSC) and hypoxia during tissue breakdown in a mouse model of simulated menses. Our results demonstrated that LRSC resided in a hypoxic microenvironment during endometrial breakdown and early repair. Immunofluorescence staining revealed that the hypoxic-located LRSC underwent proliferation and was highly colocalized with Notch1. In vitro studies illustrated that hypoxia activated Notch signaling in eMSC, leading to enhanced self-renewal, clonogenicity and proliferation of cells. More importantly, HIF-1α played an essential role in the hypoxia-mediated maintenance of eMSC through the activation of Notch signaling. In conclusion, our findings show that some endometrial stem/progenitor cells reside in a hypoxic niche during menstruation, and hypoxia can regulate the self-renewal activity of eMSC via Notch signaling.

TNFα-induced abnormal activation of TNFR/NF-κB/FTH1 in endometrium is involved in the pathogenesis of early spontaneous abortion.

Early spontaneous abortion (ESA) is one of the most common complications during pregnancy and the inflammation condition in uterine environment such as long‐term exposure to high TNFα plays an essential role in the aetiology. Ferritin heavy chain (FTH1) is considered to be closely associated with inflammation and very important in normal pregnancy, yet the underlying mechanism of how TNFα induced abortion and its relationship with FTH1 remain elusive. In this study, we found that TNFα and FTH1 were positively expressed in decidual stromal cells and increased significantly in the ESA group compared with the normal pregnancy group (NP group). Besides, TNFα expression was positively correlated with FTH1 expression. Furthermore, in vitro cell model demonstrated that high TNFα could induce the abnormal signals of TNFR/NF‐κB/FTH1 and activate apoptosis both in human endometrium stromal cells (hESCs) and in local decidual tissues. Taken together, the present findings suggest that the excessive apoptosis in response to TNFα‐induced upregulation of FTH1 may be responsible for the occurrence of ESA, and thus provide a possible therapeutic target for the treatment of ESA.

Synergistic Growth Inhibitory Effects of Eryngium kotschyi Extracts with Conventional Cytotoxic Agents: Cisplatin and Doxorubicin against Human Endometrium Cancer Cells.

Endometrial cancer is one of the most common types of cancer. For this reason, various studies have been carried out on its treatment and the effects of natural products on this disease. This study aimed to examine the growth inhibitory effects of Eryngium kotschyi Boiss. ethyl acetate [EKE] and butanol [EKB] obtained from the main methanol [EKM] extract from the aerial parts on human endometrium carcinoma [RL95-2] cells and their synergistic effect with cisplatin or doxorubicin. RL95-2 cells were treated with E. kotschyi extracts either alone or in combination with cisplatin or doxorubicin. The effects on cell growth were determined using the MTT assay and real-time cell analysis xCELLigence. The extracts demonstrated growth inhibitory activity, with a certain degree of selectivity against the RL95-2 cell line. Synergistic effects of EKE/cisplatin or doxorubicin at different concentration levels were demonstrated in RL95-2 cells. In some instances, the EKE/doxorubicin combinations resulted in antagonistic effects. The reduction level of cell viability was different and specific to each combination for the RL95-2 cell line. The growth inhibitory activity of cisplatin or doxorubicin, as a single agent, may be modified by combinations of the extracts and be synergistically enhanced in some cases. A significant synergistic effect of EKE on the RL95-2 cell line with cisplatin and doxorubicin was observed. This cytotoxic effect can be investigated in terms of molecular mechanisms. This study is the first of its kind in the literature. The mechanisms involved in this interaction between chemotherapeutic drugs and plant extracts remain unclear and should be further evaluated.

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.

Is There a Role for SARS-CoV-2/COVID-19 on the Female Reproductive System?

Coronavirus disease (COVID-19) has emerged as a very serious pandemic caused by the rapidly evolving transmission of the coronavirus SARS-CoV-2. Since its outbreak in 2020, the SARS CoV-2 has represented an important challenge for the physicians due to its well known respiratory sequelae. To date, the role of SARS-CoV-2 infection on organs and systems other than lungs and respiratory tract remains less clear. In particular, it remains to be investigated whether the reproductive system can be affected by the SARS-CoV-2 in the long term-period or, in alternative, drugs used to treat COVID-19 might impact the reproductive systems and, in turn, fertility. What is known is that SARS-Cov-2 binds to target cells of host through different receptors including angiotensin-converting enzyme 2 (ACE2), neuropilin-1, AXL and antibody-FcɣR complexes. ACE2 physiologically regulates both the expression of angiotensin II (Ang II) as well as Ang-(1-7) to exerts its physiological functions. The reproductive system abundantly expresses ACE2 and produces Ang-(1-7), starting from precursors which are locally generated or derived from systemic circulation. Ang-(1-7) plays an important role of stimulus to the growth and maturation of ovarian follicle as well as to ovulation. Also human endometrium expresses Ang-(1-7), mainly during the post-ovulatory phase. Animal and human observational studies demonstrated that Ang-(1-7) is involved in the maternal immune response to pregnancy and its deficiency is associated with a defective placenta development. In our manuscript, we review the current knowledge about whether SARS-CoV-2 may impact the female reproductive system. We further explain the possible molecular mechanism by which SARS-CoV-2 might affect ovarian, endometrial and female genital tract cells.

Gankyrin has a potential role in embryo implantation via activation of STAT3.

Embryo implantation, a critical step during the mammalian reproductive process, requires normal developing blastocysts and a receptive endometrium. Endometriosis, a common pathologically benign gynecological condition, is associated with decreased fertility and reduced endometrial receptivity. The oncoprotein, Gankyrin, has been associated with endometriosis and endometrial cancer. Here, we examined the role of Gankyrin during the process of embryo implantation and found that Gankyrin expression levels were significantly increased during the mid-secretory phase, but unaffected during the proliferative phase in the human endometrium. Using an in vitro cell adhesion assay to examine the cell adhesion rate of BeWo trophoblast spheroids to Gankyrin knockdown or overexpressing human endometrial carcinoma RL95-2 cells, we demonstrated that the adhesion rate was significantly reduced in Gankyrin-knockdown RL95-2 cells, while overexpression of Gankyrin promoted cell adhesion. Furthermore, we found that the downregulation of Gankyrin inhibited STAT3 activation and subsequent matrix metalloproteinase 2 (MMP2) expression, while overexpression led to STAT3 activation and MMP2 expression. In vivo, we found that Gankyrin expression was increased in the endometrium after conception but decreased with the prolongation of gestation time in female mice. siRNA-mediated knockdown of Gankyrin in the uterine horn led to a significant reduction in the number of implanted embryos 9 days post-gestation, which was associated with a decrease in p-STAT3 expression and MMP2 transcription. Taken together, our findings indicate that Gankryin has a potential role in embryo implantation via STAT3 activation.

Molecular and Physiological Aspects of SARS-CoV-2 Infection in Women and Pregnancy.

Whilst scientific knowledge about SARS-CoV-2 and COVID-19 is rapidly increasing, much of the effects on pregnant women is still unknown. To accommodate pregnancy, the human endometrium must undergo a physiological transformation called decidualization. These changes encompass the remodeling of endometrial immune cells leading to immunotolerance of the semi-allogenic conceptus as well as defense against pathogens. The angiotensin converting enzyme 2 (ACE2) plays an important regulatory role in the renin-angiotensin-system (RAS) and has been shown to be protective against comorbidities known to worsen COVID-19 outcomes. Furthermore, ACE2 is also crucial for decidualization and thus for early gestation. An astounding gender difference has been found in COVID-19 with male patients presenting with more severe cases and higher mortality rates. This could be attributed to differences in sex chromosomes, hormone levels and behavior patterns. Despite profound changes in the female body during pregnancy, expectant mothers do not face worse outcomes compared with non-pregnant women. Whereas mother-to-child transmission through respiratory droplets during labor or in the postnatal period is known, another question of in utero transmission remains unanswered. Evidence of placental SARS-CoV-2 infection and expression of viral entry receptors at the maternal-fetal interface suggests the possibility of in utero transmission. SARS-CoV-2 can cause further harm through placental damage, maternal systemic inflammation, and hindered access to health care during the pandemic. More research on the effects of COVID-19 during early pregnancy as well as vaccination and treatment options for gravid patients is urgently needed.

Spatiotemporal dynamics of clonal selection and diversification in normal endometrial epithelium

It has become evident that somatic mutations in cancer-associated genes accumulate in the normal endometrium, but spatiotemporal understanding of the evolution and expansion of mutant clones is limited. To elucidate the timing and mechanism of the clonal expansion of somatic mutations in cancer-associated genes in the normal endometrium, we sequence 1311 endometrial glands from 37 women. By collecting endometrial glands from different parts of the endometrium, we show that multiple glands with the same somatic mutations occupy substantial areas of the endometrium. We demonstrate that “rhizome structures”, in which the basal glands run horizontally along the muscular layer and multiple vertical glands rise from the basal gland, originate from the same ancestral clone. Moreover, mutant clones detected in the vertical glands diversify by acquiring additional mutations. These results suggest that clonal expansions through the rhizome structures are involved in the mechanism by which mutant clones extend their territories. Furthermore, we show clonal expansions and copy neutral loss-of-heterozygosity events occur early in life, suggesting such events can be tolerated many years in the normal endometrium. Our results of the evolutionary dynamics of mutant clones in the human endometrium will lead to a better understanding of the mechanisms of endometrial regeneration during the menstrual cycle and the development of therapies for the prevention and treatment of endometrium-related diseases.

Deciphering the endometrial niche of human thin endometrium at single-cell resolution

Thin endometrium has been widely recognized as a critical cause of infertility, recurrent pregnancy loss, and placental abnormalities; however, access to effective treatment is a formidable challenge due to the rudimentary understanding of the pathogenesis of thin endometrium. Here, we profiled the transcriptomes of human endometrial cells at single-cell resolution to characterize cell types, their communications, and the underlying mechanism of endometrial growth in normal and thin endometrium during the proliferative phase. Stromal cells were the most abundant cell type in the endometrium, with a subpopulation of proliferating stromal cells whose cell cycle signaling pathways were compromised in thin endometrium. Both single-cell RNA sequencing and experimental verification revealed cellular senescence in the stroma and epithelium accompanied by collagen overdeposition around blood vessels. Moreover, decreased numbers of macrophages and natural killer cells further exacerbated endometrial thinness. In addition, our results uncovered aberrant SEMA3, EGF, PTN, and TWEAK signaling pathways as causes for the insufficient proliferation of the endometrium. Together, these data provide insight into therapeutic strategies for endometrial regeneration and growth to treat thin endometrium.

Extruded Nucleoli of Human Dental Pulp Cells.

Background and Objectives: The dental pulp stem cells are highly proliferative and can differentiate into various cell types, including endothelial cells. We aimed to evaluate the ultrastructural characteristics of the human dental pulp cells of the permanent frontal teeth. Materials and Methods: Human adult bioptic dental pulp was collected from n = 10 healthy frontal teeth of five adult patients, prior to prosthetic treatments for aesthetic purposes. Tissues were examined under transmission electron microscopy. Results: We identified cells with a peculiar trait: giant nucleoli resembling intranuclear endoplasmic reticulum, which mimicked extrusion towards the cytoplasm. These were either partly embedded within the nuclei, the case in which their adnuclear side was coated by marginal heterochromatin and the abnuclear side was coated by a thin rim of ribosomes, or were apparently isolated from the nuclei, while still being covered by ribosomes. Conclusions: Similar electron microscopy features were previously reported in the human endometrium, as nucleolar channel system; or R-Rings induced by Nopp140. To our knowledge, this is the first report of extruded nucleolar structure in the dental pulp. Moreover, the aspect of giant extruded nucleoli was not previously reported in any human cell type, although similar evidence was gathered in other species as well as in plants.

A Novel Xeno-Free Method to Isolate Human Endometrial Mesenchymal Stromal Cells (E-MSCs) in Good Manufacturing Practice (GMP) Conditions.

The cyclic regeneration of human endometrium is guaranteed by the proliferative capacity of endometrial mesenchymal stromal cells (E-MSCs). Due to this, the autologous infusion of E-MSCs has been proposed to support endometrial growth in a wide range of gynecological diseases. We aimed to compare two different endometrial sampling methods, surgical curettage and vacuum aspiration biopsy random assay (VABRA), and to validate a novel xeno-free method to culture human E-MSCs. Six E-MSCs cell samples were isolated after mechanical tissue homogenization and cultured using human platelet lysate. E-MSCs were characterized for the colony formation capacity, proliferative potential, and multilineage differentiation. The expression of mesenchymal and stemness markers were tested by FACS analysis and real-time PCR, respectively. Chromosomal alterations were evaluated by karyotype analysis, whereas tumorigenic capacity and invasiveness were tested by soft agar assay. Both endometrial sampling techniques allowed efficient isolation and expansion of E-MSCs using a xeno-free method, preserving their mesenchymal and stemness phenotype, proliferative potential, and limited multi-lineage differentiation ability during the culture. No chromosomal alterations and invasive/tumorigenic capacity were observed. Herein, we report the first evidence of efficient E-MSCs isolation and culture in Good Manufacturing Practice compliance conditions, suggesting VABRA endometrial sampling as alternative to surgical curettage.

Increased expression of HOXA11-AS attenuates endometrial decidualization in recurrent implantation failure patients

Endometrial decidualization is a prerequisite for implantation, and impaired decidualization is associated with recurrent implantation failure (RIF). Coding genes of the HOX family have been clarified as critical regulators in endometrial decidualization, but the role of long non-coding RNAs (lncRNAs) in the HOX gene family has yet to be determined. The aim of this study was to clarify the possible roles of lncRNAs in the HOX gene family in decidualization. In this study, we identified that HOXA11-AS was the most reduced lncRNA in the HOX family in the human endometrium during the window of implantation, and it was elevated in RIF patients. Mechanistically, HOXA11-AS negatively regulated decidualization through competitive interaction with PTBP1, an RNA-binding protein. Binding of PTBP1 to HOXA11-AS limited PTBP1 availability to regulate PKM1/2 alternative splicing, resulting in enhanced PKM1 and diminished PKM2 expression, thus attenuating decidualization. The pattern of high HOXA11-AS expression and impaired PKM2 splicing was consistently observed in RIF patients. Collectively, our study indicates that the increase of HOXA11-AS is detrimental to endometrial decidualization, likely contributing to RIF. Our study may shed light on the pathogenesis and treatment of RIF.

Expression levels of Tyro3 Receptor Kinase in the Decidua of the First Trimester Unexplained Recurrent Pregnancy Loss

Spontaneous loss is seen 12-15 % in all pregnancies. More than %50 of those patients do not have a defined etiology, so they are named unexplained Recurrent Pregnancy Loss (URPL). Studies in recent years have made us think that Pregnancy Losses may be related to insufficient decidualization and undetected prothrombotic problems. Tyro3 receptor kinase (RTK) is a member of TAM receptors and has been reported to have an important role in migration, Epithelial-mesenchymal transition (EMT), and platelet aggregation. There is not sufficient knowledge about expression levels of Tyro3 RTK in human first-trimester URPL decidua (URPLD). By immunohistochemistry, immunoblotting, and qPCR, we investigated the expression of Tyro3 RTK in the decidua of human first-trimester termination healthy pregnancy (TPD)(n:6) and URPLD(n:6), and human endometrium (CE)(n:6). Our results suggest that Tyro3 RTK expression significantly decreases with pregnancy and then returns to levels of CE for URPLD. Considering the role of Tyro3 RTK in platelet activation and thrombus formation, it suggests that this decrease observed in TPD may prevent the formation of prothrombosis which can prevent placental flow, and thus, hemostasis could be regulated in pregnancy through Tyro3 RTK. Although Tyro3 RTK decrease in TPD, locally increase on TPD, and also decrease on URPLD of Tyro3 RTK on DSCs makes us think, which Tyro3 RTK has a regulating role for EMT formation on DSCs and may participate in implantation and survival processing of the embryo through DSCs. If those predictions are supported by further functional analyses, one of the causes of URPLD can be enlightened.

Artificial intelligence deep learning model assessment of leukocyte counts and proliferation in endometrium from women with and without polycystic ovary syndrome

To study whether artificial intelligence (AI) technology can be used to discern quantitative differences in endometrial immune cells between cycle phases and between samples from women with polycystic ovary syndrome (PCOS) and non-PCOS controls. Only a few studies have analyzed endometrial histology using AI technology, and especially, studies of the PCOS endometrium are lacking, partly because of the technically challenging analysis and unavailability of well-phenotyped samples. Novel AI technologies can overcome this problem. Case-control study. University hospital-based research laboratory. Forty-eight women with PCOS and 43 controls. Proliferative phase samples (26 control and 23 PCOS) and luteinizing hormone (LH) surge timed LH+ 7-9 (10 control and 16 PCOS) and LH+ 10-12 (7 control and 9 PCOS) secretory endometrial samples were collected during 2014-2019. None. Endometrial samples were stained with antibodies for CD8+ T cells, CD56+ uterine natural killer cells, CD68+ macrophages, and proliferation marker Ki67. Scanned whole slide images were analyzed with an AI deep learning model. Cycle phase differences in leukocyte counts, proliferation rate, and endometrial thickness were measured within the study populations and between the PCOS and control samples. A subanalysis of anovulatory PCOS samples (n = 11) vs. proliferative phase controls (n = 18) was also performed. Automated cell counting with a deep learning model performs well for the human endometrium. The leukocyte numbers and proliferation in the endometrium fluctuate with the menstrual cycle. Differences in leukocyte counts were not observed between the whole PCOS population and controls. However, anovulatory women with PCOS presented with a higher number of CD68+ cells in the epithelium (controls vs. PCOS, median [interquartile range], 0.92 [0.75-1.51] vs. 1.97 [1.12-2.68]) and fewer leukocytes in the stroma (CD8%, 3.72 [2.18-4.20] vs. 1.44 [0.77-3.03]; CD56%, 6.36 [4.43-7.43] vs. 2.07 [0.65-4.99]; CD68%, 4.57 [3.92-5.70] vs. 3.07 [1.73-4.59], respectively) compared with the controls. The endometrial thickness and proliferation rate were comparable between the PCOS and control groups in all cycle phases. Artificial intelligence technology provides a powerful tool for endometrial research because it is objective and can efficiently analyze endometrial compartments separately. Ovulatory endometrium from women with PCOS did not differ remarkably from the controls, which may indicate that gaining ovulatory cycles normalizes the PCOS endometrium and enables normalization of leukocyte environment before implantation. Deviant endometrial leukocyte populations observed in anovulatory women with PCOS could be interrelated with the altered endometrial function observed in these women.

C-Peptide Promotes Cell Migration by Controlling Matrix Metallopeptidase-9 Activity Through Direct Regulation of β-Catenin in Human Endometrial Stromal Cells.

The motility of endometrial stromal cells (ESCs) contributes to the restoration of the endometrial functional layer and subsequently supports the trophoblast invasion during early pregnancy. Following ESCs differentiation through decidualization in response to progesterone during the menstrual cycle and embryo implantation, decidualized ESCs (D-ESCs) have greater motility and invasive activity. The human proinsulin-connecting peptide (C-peptide) is produced in equimolar amounts during the proteolysis of insulin in pancreatic β-cells. However, the function of C-peptide in the cellular motility of the human endometrium remains unexamined. In the present study, C-peptide was identified as a determinant of undecidualized human endometrial stromal cells (UnD-ESCs) migration. C-peptide promoted the migration and invasion of UnD-ESCs and trophoblast-derived Jeg3 cells, but not that of ESCs post decidualization, a functional and biochemical differentiation of UnD-ESCs. Both Akt and protein phosphatase 1 regulated β-catenin phosphorylation in UnD-ESCs, not D-ESCs, thereby promoting β-catenin nuclear translocation in C-peptide-treated UnD-ESCs. C-peptide was also observed to increase matrix metallopeptidase-9 (MMP9) activity by increasing MMP9 expression and decreasing the expression of metallopeptidase inhibitor 1 (TIMP1) and TIMP3. Their expression was modulated by the direct binding of β-catenin in the regulatory region of the promoter of MMP9, TIMP1, and TIMP3. Inhibition of either β-catenin or MMP9 dampened C-peptide-enhanced migration in UnD-ESCs. Together, these findings suggest that C-peptide levels are critical for the regulation of UnD-ESC migration, providing evidence for the association between C-peptide levels and the failure rate of trophoblast invasion by inducing abnormal migration in UnD-ESCs in hyperinsulinemia or PCOS patients.

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.

Mechanisms of Scarless Repair at Time of Menstruation: Insights From Mouse Models.

The human endometrium is a remarkable tissue which may experience up to 400 cycles of hormone-driven proliferation, differentiation and breakdown during a woman's reproductive lifetime. During menstruation, when the luminal portion of tissue breaks down, it resembles a bloody wound with piecemeal shedding, exposure of underlying stroma and a strong inflammatory reaction. In the absence of pathology within a few days the integrity of the tissue is restored without formation of a scar and the endometrium is able to respond appropriately to subsequent endocrine signals in preparation for establishment of pregnancy if fertilization occurs. Understanding mechanisms regulating scarless repair of the endometrium is important both for design of therapies which can treat conditions where this is aberrant (heavy menstrual bleeding, fibroids, endometriosis, Asherman's syndrome) as well as to provide new information that might allow us to reduce fibrosis and scar formation in other tissues. Menstruation only occurs naturally in species that exhibit spontaneous stromal cell decidualization during the fertile cycle such as primates (including women) and the Spiny mouse. To take advantage of genetic models and detailed time course analysis, mouse models of endometrial shedding/repair involving hormonal manipulation, artificial induction of decidualization and hormone withdrawal have been developed and refined. These models are useful in modeling dynamic changes across the time course of repair and have recapitulated key features of endometrial repair in women including local hypoxia and immune cell recruitment. In this review we will consider the evidence that scarless repair of endometrial tissue involves changes in stromal cell function including mesenchyme to epithelial transition, epithelial cell proliferation and multiple populations of immune cells. Processes contributing to endometrial fibrosis (Asherman's syndrome) as well as scarless repair of other tissues including skin and oral mucosa are compared to that of menstrual repair.

Role of Natural Killer Cells during Pregnancy and Related Complications.

A high number of leucocytes reside in the human endometrium and are distributed differentially during the menstrual cycle and pregnancy. During early pregnancy, decidual natural killer (dNK) cells are the most common type of natural killer (NK) cells in the uterus. The increase in the number of uterine NK (uNK) cells during the mid-secretory phase of the menstrual cycle, followed by further increase of dNK cells in early pregnancy, has heightened interest in their involvement during pregnancy. Extensive research has revealed various roles of dNK cells during pregnancy including the formation of new blood vessels, migration of trophoblasts, and immunological tolerance. The present review article is focused on the significance of NK cells during pregnancy and their role in pregnancy-related diseases. The article will provide an in-depth review of cellular and molecular interactions during pregnancy and related disorders, with NK cells playing a pivotal role. Moreover, this study will help researchers to understand the physiology of normal pregnancy and related complications with respect to NK cells, so that future research work can be designed to alleviate the complications.