Differentiating mouse embryonic stem cells express markers of human endometrium

New Solutions for Old Problems: How Reproductive Tissue Engineering Has Been Revolutionizing Reproductive Medicine

Acquired disorders and congenital defects of the male and female reproductive systems can have profound impacts on patients, causing sexual and endocrine dysfunction and infertility, as well as psychosocial consequences that affect their self-esteem, identity, sexuality, and relationships. Reproductive tissue engineering (REPROTEN) is a promising approach to restore fertility and improve the quality of life of patients with reproductive disorders by developing, replacing, or regenerating cells, tissues, and organs from the reproductive and urinary systems. In this review, we explore the latest advancements in REPROTEN techniques and their applications for addressing degenerative conditions in male and female reproductive organs. We discuss current research and clinical outcomes and highlight the potential of 3D constructs utilizing biomaterials such as scaffolds, cells, and biologically active molecules. Our review offers a comprehensive guide for researchers and clinicians, providing insights into how to reestablish reproductive tissue structure and function using innovative surgical approaches and biomaterials. We highlight the benefits of REPROTEN for patients, including preservation of fertility and hormonal production, reconstruction of uterine and cervical structures, and restoration of sexual and urinary functions. Despite significant progress, REPROTEN still faces ethical and technical challenges that need to be addressed. Our review underscores the importance of continued research in this field to advance the development of effective and safe REPROTEN approaches for patients with reproductive disorders.

A functional mechanism for a non-coding variant near AGTR2 associated with risk for preterm birth

BACKGROUND

Preterm birth (PTB), defined as delivery before 37 gestational weeks, imposes significant public health burdens. A recent maternal genome-wide association study of spontaneous PTB identified a noncoding locus near the angiotensin II receptor type 2 (AGTR2) gene. Genotype-Tissue Expression data revealed that alleles associated with decreased AGTR2 expression in the uterus were linked to an increased risk of PTB and shortened gestational duration. We hypothesized that a causative variant in this locus modifies AGTR2 expression by altering transcription factor (TF) binding.

METHODS

To investigate this hypothesis, we performed bioinformatics analyses and functional characterizations at the implicated locus. Potential causal single nucleotide polymorphisms (SNPs) were prioritized, and allele-dependent binding of TFs was predicted. Reporter assays were employed to assess the enhancer activity of the top PTB-associated non-coding variant, rs7889204, and its impact on TF binding.

RESULTS

Our analyses revealed that rs7889204, a top PTB-associated non-coding genetic variant is one of the strongest eQTLs for the AGTR2 gene in uterine tissue samples. We observed differential binding of CEBPB (CCAAT enhancer binding protein beta) and HOXA10 (homeobox A10) to the alleles of rs7889204. Reporter assays demonstrated decreased enhancer activity for the rs7889204 risk "C" allele.

CONCLUSION

Collectively, these results demonstrate that decreased AGTR2 expression caused by reduced transcription factor binding increases the risk for PTB and suggest that enhancing AGTR2 activity may be a preventative measure in reducing PTB risk.

A Preliminary Study on the Correlation Between Age and Endometrial Receptivity

Background

It is well established that female fertility declines with age, primarily because of loss of ovarian function. However, few studies have clarified the relationship between increasing age and endometrial receptivity. Here, we aimed to study the impact of age on endometrial receptivity, meanwhile, we examined the expression of endometrial mesenchymal stem cell (eMSC) surface markers (CD146 and PDGF-Rβ), essential for endometrial development and re-growth, in different age groups.

Methods

Participants were enrolled in this study between October 2020 and July 2021. All 31 patients were divided into three age groups; early (30-39 years old, n=10), intermediate (40-49 years old, n=12) and advanced (≥50 years old, n=9). We assessed localization and expression of CD146 and PDGF-Rβ by immunofluorescence and further analyzed selected endometrial receptivity markers (Homeobox A10 HOXA10, leukemia inhibitory factor LIF and osteopontin) and steroid hormone receptors by immunohistochemistry.

Results

There were no significant differences in expression of HOXA10 and OPN (p>0.05) among the three groups. However, we found a significant difference in LIF expression between the early and advanced age groups, with higher expression noted in the latter group (p=0.02). Similarly, estrogen receptor (ER) and progesterone receptor (PR) expression were significantly increased (p=0.01 and p=0.01, respectively) in the advanced age group compared with the early age group. There were no significant difference in CD146 and PDGF-Rβ expression among the three groups (p>0.05).

Conclusion

These results suggest that the age of the patient does not influence their endometrial receptivity. So, this study serves to increase our understanding of the impact of age and eMSCs on endometrial receptivity and expands the etiology of age-related infertility.

Endometriosis Stem Cells as a Possible Main Target for Carcinogenesis of Endometriosis-Associated Ovarian Cancer (EAOC)

Endometriosis is a serious recurrent disease impairing the quality of life and fertility, and being a risk for some histologic types of ovarian cancer defined as endometriosis-associated ovarian cancers (EAOC). The presence of stem cells in the endometriotic foci could account for the proliferative, migrative and angiogenic activity of the lesions. Their phenotype and sources have been described. The similarly disturbed expression of several genes, miRNAs, galectins and chaperones has been observed both in endometriotic lesions and in ovarian or endometrial cancer. The importance of stem cells for nascence and sustain of malignant tumors is commonly appreciated. Although the proposed mechanisms promoting carcinogenesis leading from endometriosis into the EAOC are not completely known, they have been discussed in several articles. However, the role of endometriosis stem cells (ESCs) has not been discussed in this context. Here, we postulate that ESCs may be a main target for the carcinogenesis of EAOC and present the possible sequence of events resulting finally in the development of EAOC.

Bi-potential hPSC-derived Müllerian duct-like cells for full-thickness and functional endometrium regeneration

Stem cell-based tissue regeneration strategies are promising treatments for severe endometrial injuries. However, there are few appropriate seed cells for regenerating a full-thickness endometrium, which mainly consists of epithelia and stroma. Müllerian ducts in female embryonic development develop into endometrial epithelia and stroma. Hence, we first generated human pluripotent stem cells (hPSC)-derived Müllerian duct-like cells (MDLCs) using a defined and effective protocol. The MDLCs are bi-potent, can gradually differentiate into endometrial epithelial and stromal cells, and reconstitute full-thickness endometrium in vitro and in vivo. Furthermore, MDLCs showed the in situ repair capabilities of reconstructing endometrial structure and recovering pregnancy function in full-thickness endometrial injury rats, and their differentiation fate was revealed by single-cell RNA sequencing (scRNA-seq). Our study provides a strategy for hPSC differentiation into endometrial lineages and an alternative seed cell for injured endometrial regeneration.

New Insights in Pathogenesis of Endometriosis

Endometriosis is a gynecological disease characterized by the growth of endometrial glands and stroma outside the uterine cavity. The incidence of the disease is very high, there are currently no reliable early diagnostic tests, the therapies are only symptomatic and, consequently, the social impact of endometriosis is very important, also considering the related fertility problems. Despite this, the pathogenesis of endometriosis is still not fully defined. Retrograde menstruation and coelomic metaplasia are currently the most recognized pathogenetic hypotheses. Recent experimental evidences generated by our research group and by others have indicated an alteration of the fine-tuning of the female genital system developmental program during a critical window of time in the fetal life as the pathogenetic event prompting to the development of endometriosis later in life. Goal of this article is to present a revision of the recent literature about the different pathogenetic mechanisms proposed for endometriosis with particular emphasis on the embryologic theory. The possible clinical and pathological implications of these findings will be discussed.

Identification of Intercellular Crosstalk between Decidual Cells and Niche Cells in Mice

Decidualization is a crucial step for human reproduction, which is a prerequisite for embryo implantation, placentation and pregnancy maintenance. Despite rapid advances over recent years, the molecular mechanism underlying decidualization remains poorly understood. Here, we used the mouse as an animal model and generated a single-cell transcriptomic atlas of a mouse uterus during decidualization. By analyzing the undecidualized inter-implantation site of the uterus as a control, we were able to identify global gene expression changes associated with decidualization in each cell type. Additionally, we identified intercellular crosstalk between decidual cells and niche cells, including immune cells, endothelial cells and trophoblast cells. Our data provide a valuable resource for deciphering the molecular mechanism underlying decidualization.

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.

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.

The Origin and Pathogenesis of Endometriosis

Recent molecular genetic findings on endometriosis and normal endometrium suggest a modified model in which circulating epithelial progenitor or stem cells intended to regenerate uterine endometrium after menstruation may become overreactive and trapped outside the uterus. These trapped epithelium-committed progenitor cells form nascent glands through clonal expansion and recruit polyclonal stromal cells, leading to the establishment of deep infiltrating endometriosis. Once formed, the ectopic tissue becomes subject to immune surveillance, resulting in chronic inflammation. The inflammatory response orchestrated by nuclear factor-κB signaling is exacerbated by aberrations in the estrogen receptor-β and progesterone receptor pathways, which are also affected by local inflammation, forming a dysregulated inflammation-hormonal loop. Glandular epithelium within endometriotic tissue harbors cancer-associated mutations that are frequently detected in endometriosis-related ovarian cancers. In this review, we summarize recent advances that have illuminated the origin and pathogenesis of endometriosis and have provided new avenues for research that promise to improve the early diagnosis and management of endometriosis.

Aminopeptidase N expression in the endometrium could affect endometrial receptivity

Aminopeptidase N (ANPEP) is a membrane-bound zinc-dependent peptidase. Although it is widely believed that ANPEP acts as an important angiogenesis regulatory factor, there are few studies about its function in the female reproductive system. In our previous research, we applied Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) to analyze the influence of different controlled superovulation treatments for Assisted Reproductive Technology, In Vitro Fertilization and Embryo Transfer (IVF-ET)) patients from a global proteomic perspective to search for potential biomarkers associated with endometrium receptivity and embryo implantation. ANPEP is one of the proteins that demonstrated differential expression between different treatment groups and may be closely associated with endometrial receptivity. In this study, we assessed the expression of ANPEP in the endometrium of mice at different ages and found it to be highest in the mature period. We also detected ANPEP expression in the endometrium of IVF-ET patients in the proliferative, preimplantation and implantation stages, and the highest expression level of ANPEP was found in the last group. Human primary endometrial stromal cells were infected with an adenovirus expression vector containing the ANPEP gene and a green fluorescent protein (GFP) fusion protein; the mRNA levels of HOXA-10, LIF, and integrin β3 were found to be increased. Therefore, we conclude that ANPEP could be involved in the regulation of endometrial receptivity.