Prospective biomarkers of stem cells of human endometrium and fallopian tube compared with bone marrow

In Vitro Implantation Model Using Human Endometrial SUSD2+ Mesenchymal Stem Cells and Myometrial Smooth Muscle Cells

Objective

This study evaluated a novel in vitro implantation model using human endometrial mesenchymal stem cells (EMSCs), SUSD2⁺, and myometrial smooth muscle cells (SMCs) that were co-cultured with mouse blastocysts as the surrogate embryo.

Materials and Methods

In this experimental study, SUSD2⁺ MSCs were isolated from human endometrial cell suspensions (ECS) at the fourth passage by magnetic-activated cell sorting. The ECS and SUSD2⁺ cells were separately co-cultured with human myometrial muscle cells for five days. After collection of mouse blastocysts, the embryos were placed on top of the co-cultured cells for 48 hours. The interaction between the embryo and the cultured cells was assessed morphologically at the histological and ultrastructural levels, and by expression profiles of genes related to implantation.

Results

Photomicrographs showed that trophoblastic cells grew around the embryonic cells and attached to theECS and SUSD2⁺ cells. Ultrastructural observations revealed pinopode and microvilli-like structures on the surfaces of both the ECS and SUSD2⁺ cells. Morphologically, the embryos developed to the egg-cylinder stage in both groups. Gene expression analysis showed no significant differences between the two groups in the presence of an embryo, but an increased expression of αV was detected in SUSD2⁺ cells compared to ECS cells in the absence of an embryo.

Conclusion

This study showed that SUSD2⁺ cells co-cultured with SMCs could interact with mouse embryos. The co-cultured cells could potentially be used as an implantation model.

Fallopian tube epithelial cells express androgen receptor and have a distinct hormonal responsiveness when compared with endometrial epithelium

STUDY QUESTION

How does steroid receptor expression, proliferative activity and hormone responsiveness of the fallopian tube (FT) epithelium compare to that of the endometrial epithelium?

SUMMARY ANSWER

Proliferative indices, hormone receptor expression-scores and in vitro response to oestrogen and androgens of the human FT demonstrate a distinct pattern from the matched endometrium.

WHAT IS KNOWN ALREADY

The FT epithelium exists as a continuum of the endometrium, and both express steroid hormone receptors. The ovarian steroid hormones regulate cyclical proliferation and regeneration of the endometrium, but their effects on steroid hormone receptor expression and proliferation in the FT have not yet been fully elucidated.

STUDY DESIGN, SIZE, DURATION

We included women with proven fertility, undergoing hysterectomy and bilateral salpingo-oophorectomy for benign, gynaecological conditions at Liverpool Women's NHS Foundation Trust. They had no known endometrial or tubal pathology and were not on hormonal treatments for at least 3 months preceding sample collection in this prospective observational study (conducted between 2010 and 2018). A full-thickness sample of the endometrium and a sample from the FT were collected from each woman.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The differential protein and mRNA levels of steroid hormone receptors, oestrogen receptors α and β, androgen receptor (AR) and progesterone receptor (PR), and the proliferative marker (Ki67) of the endometrium and the FT tissue samples from 47 healthy women undergoing surgery (37 premenopausal and 10 postmenopausal) were investigated using immunohistochemistry and quantitative real-time PCR. The comparative responsiveness to oestrogen and androgen of the endometrium and the fimbrial end of the FT was analysed using an in vitro short-term explant culture model. The endpoints assessed in the explants were the changes in mRNA and protein levels for AR, PR and the epithelial proliferative index after 24 h treatment with oestradiol (E2) or dihydrotestosterone (DHT).

MAIN RESULTS AND THE ROLE OF CHANCE

The premenopausal endometrial functionalis glands (FG) displayed the well-known cyclic variation in cellular proliferation and steroid receptor scores. Compared with the endometrial FG, the matched FT epithelium (both fimbrial or isthmic ends) displayed a significantly lower proportion of cells expressing Ki67 (2.8% ± 2.2%, n = 18 vs 30.0% ± 26.3%, n = 16, P = 0.0018, respectively) accompanied with a significantly higher AR immunoscores (6.7 ± 2.7, n = 16 vs 0.3 ± 1.0, n = 10, P = 0.0136). The proportion of cells expressing Ki67 and the AR immunoscores of the FT epithelium correlated positively with endometrial luminal epithelium (r = 0.62, P = 0.005, and r = 0.68, P = 0.003, respectively). In vitro experiments suggested the tubal explants to be apparently less responsive to E2 yet more sensitive to DHT compared with the matched endometrium explants.

LIMITATIONS, REASONS FOR CAUTION

The short-term in vitro nature of the tissue explant cultures used in the study may not be representative of how different anatomical regions of the endometrium and FT behave in vivo. Our study included a high proportion of older premenopausal women with a regular menstrual cycle, which may therefore affect extrapolation of findings to a younger group.

WIDER IMPLICATIONS OF THE FINDINGS

Advancing our understanding of tubal and endometrial epithelial cell function has important implications for the diagnosis and treatment of diseases such as infertility, ectopic pregnancy, endometriosis and cancer.

STUDY FUNDING/COMPETING INTEREST(S)

The work included in this article was funded by Wellbeing of Women project grants RG1073 and RG2137 (D.K.H.) and Wellbeing of Women Entry-Level Scholarship ELS706 (A.M). A.M. was also supported by an NIHR ACF fellowship grant. Further support received from Liverpool Women's Hospital NHS Trust (S.M.), University of Liverpool (E.B. and A.W.). All authors declare there are no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

SOX2 is a promising predictor of relapse and death in advanced stage high-grade serous ovarian cancer patients with residual disease after debulking surgery

The transcription factor SOX2 is a well-established and important stem cell marker. Its role in cancer biology remains unclear, but it has been proposed to also be a marker of cancer stem cells. We investigated the role of SOX2 protein expression in women with high-grade serous ovarian cancer (HGSOC) to determine its potential prognostic and treatment predictive value. We constructed a tissue microarray of 130 advanced stage HGSOC tumors with an average of 6 cores each, stained for SOX2 protein expression and evaluated survival outcomes. We also treated two HGSOC cell lines with carboplatin and paclitaxel and measured SOX2 expression by RT-PCR and immunoblotting at different doses and time-points. Among patients with non-radical debulking surgery overall and progression-free survival were shorter for patients with SOX2 positive tumors (mean 26 vs. 39 months, log-rank test: p = .0076, and mean 14 vs. 19 months, p = .055, respectively). Knockdown of SOX2 in cell lines did not affect growth inhibition following chemotherapy treatment. Our results show that SOX2 has a strong prognostic potential among HGSOC patients with residual tumor tissue after debulking surgery and suggest that SOX2 expressing cells remaining after non-radical debulking surgery may constitute a subpopulation of cancer stem cells with greater tumor-initiating potential.

Characterization of cell fusion in an experimental mouse model of endometriosis†

Cell fusion is involved in the development of some adult organs, is implicated in the pathogenesis of specific types of cancer, and is known to participate in repair/regeneration processes mediated by bone-marrow-derived cells (BMDCs). Endometriosis is a disease characterized by growth of functional endometrial tissue outside of the uterine cavity. Endometriosis shares some molecular properties with cancer and BMDCs home to endometriosis lesions in a mouse model. Our objective was to determine if cell fusion can occur in endometriosis and establish whether bone-marrow-derived cells participate in cell fusion events in lesions. We employed a Cre-Lox system to identify cell fusion events in a mouse model of endometriosis. Fused cells were detected in endometriotic lesions, albeit at a low frequency (∼1 in 400 cells), localized to the stromal compartment, and displayed restricted proliferation. Using 5-fluorouracil-based nongonadotoxic bone marrow transplantation model, we demonstrate that bone marrow cells represent a principal cell source for fusion events in lesions. Cell fusion progeny uniformly lacked expression of selected markers of hematopoietic, endothelial, and epithelial markers, though they expressed the mesenchymal/stromal markers Sca-1 and CD29. This study is the first to describe the phenomenon of cell fusion in endometriosis and points to a mesenchymal population derived from cell fusion events with limited proliferative activity, properties previously attributed to endometrial stem cells. Their putative role in the pathogenesis of the disease remains to be elucidated.

Regeneration of the Fallopian Tube Mucosa Using Bone Marrow Mesenchymal Stem Cell Transplantation After Induced Chemical Injury in a Rat Model

In this study, we describe a novel insight about the use of bone marrow-derived mesenchymal stem cells (BM-MSCs) for fallopian tube (FT) regeneration. Seventy rats' tubes were involved in this study and divided into 4 groups: control (15), ethanol injured (20), mesenchymal stem cell (MSC)-recipient without injury (15), and MSC recipient after injury (20). The BM-MSCs were isolated from male rats, and their incorporation into the tissues was confirmed by the detection of Sry gene in MSC-recipient rats using RT-PCR. Histological and immunohistological sections of the 4 groups were comparably evaluated. We found that direct injection of ethanol into FT caused structural impairment, which was restored largely after receiving MSCs. We have revealed for the first time that prominin 1 (Prom1, stem cell marker) was expressed in the fimbriated distal tubal end. The MSC transplantation caused (1) significant increase in the tissue level and immunoexpresstion of Prom1 ( P < .001 and P = .017, respectively) and vascular endothelial growth factor (VEGF; vasculogenic marker; P < .001 and P = .004, respectively), (2) significant increase in the immunoexpresstion of proliferating cell nuclear antigen (PCNA; proliferation marker; P < .001), and (3) significant decrease in the immunoexpresstion of caspase 3 (CASP-3; apoptotic marker; P < .001) compared to the injured tissues. In conclusion, MSCs could exhibit its restorative effect on FT through their ability to (1) activate the resident stem cells in the distal tubal end, (2) mediate the expression of VEGF and PCNA, and (3) influence tissue apoptosis. This study laid the foundation for assessing the contribution of stem cells in the distal tubal end in direct repair of the tube when required to assist reproduction.

Isolation and characterization of equine endometrial mesenchymal stromal cells

Background

Equine mesenchymal stromal/stem cells (MSCs) are most commonly harvested from bone marrow (BM) or adipose tissue, requiring the use of surgical procedures. By contrast, the uterus can be accessed nonsurgically, and may provide a more readily available cell source. While human endometrium is known to harbor mesenchymal precursor cells, MSCs have not been identified in equine endometrium. This study reports the isolation, culture, and characterization of MSCs from equine endometrium.

Methods

The presence of MSC and pericyte markers in endometrial sections was determined using immunohistochemistry. Stromal cells were harvested and cultured after separation of epithelial cells from endometrial fragments using Mucin-1-bound beads. For comparison, MSCs were also harvested from BM. The expression of surface markers in endometrial and BM-derived MSCs was characterized using flow cytometry and quantitative polymerase chain reaction. MSCs were differentiated in vitro into adipogenic, chondrogenic, osteogenic, and smooth muscle lineages.

Results

Typical markers of MSCs (CD29, CD44, CD90, and CD105) and pericytes (NG2 and CD146) were localized in the equine endometrium. Both endometrial and BM MSCs grew clonally and robustly expressed MSC and pericyte markers in culture while showing greatly reduced or negligible expression of hematopoietic markers (CD45, CD34) and MHC-II. Additionally, both endometrial and BM MSCs differentiated into adipogenic, osteogenic, and chondrogenic lineages in vitro, and endometrial MSCs had a distinct ability to undergo smooth muscle differentiation.

Conclusions

We have demonstrated for the first time the presence of cells in equine endometrium that fulfill the definition of MSCs. The equine endometrium may provide an alternative, easily accessible source of MSCs, not only for therapeutic regeneration of the uterus, but also for other tissues where MSCs from other sources are currently being used therapeutically.

Characterization of mesenchymal stem cells in bovine endometrium during follicular phase of oestrous cycle

Stem cells have been postulated as responsible for cell regeneration in highly and continuously regenerative tissues such as the endometrium. Few studies in cattle have identified and specified the presence of stem cells in the endometrium during the oestrous cycle. The aim of this study was to investigate the presence of mesenchymal stem cells (MSCs) in the bovine endometrium during the follicular phase (FP) of the oestrous cycle. Uterine tissue was collected in the time-frame comprising day 18 of the cycle and ovulation (day 0). We isolated, cultured and expanded four primary cell lines from endometrium and identified byRT-qPCR the expression of OCT4, SOX2 but not NANOG (undifferentiated/embryonic markers), CD44 (MSCs marker) and c-KIT (stem cell marker) genes; and the encoded Oct4, Sox2 and Cd44 proteins by Western blot or immunostaining of paraffin-embedded tissue in endometrium. We demonstrated that cells isolated from bovine endometrium displayed essentially the same gene expression pattern; however, at the protein level, Oct4 and Cd44 were not detected. Besides, they showed typical functional characteristics of MSCs such as fibroblast-like morphology, plastic adherence, high proliferative capacity, clone formation in vitro and the ability to differentiate into chondrogenic, osteogenic and adipogenic lineages. We obtained for the first time an extensive characterization of undifferentiated cells populations contained in the bovine endometrium during the FP of the oestrous cycle.

Endometriosis: a role for stem cells

Endometriosis is a complex gynecologic condition affecting 6-10% of reproductive aged women and is a major cause of chronic pain and infertility. Mechanisms of disease pathogenesis are poorly understood. Considerable evidence supports the existence of a stem cell population in the endometrium which provides a physiologic source of regenerative endometrial cells, and multiple lines of evidence now support a key role for stem cells in the pathogenesis of endometriosis. In addition, new blood vessel formation is critical for the establishment and maintenance of endometriotic implants, a process in which endothelial progenitor cells may play an integral role. These new insights into disease pathogenesis present exciting opportunities to develop targeted and more effective therapeutic options in the management of this common and challenging disease.

The utility of human fallopian tube mucosa as a novel source of multipotent stem cells for the treatment of autologous reproductive tract injury

INTRODUCTION

Fallopian tube, which is normally discarded in surgical procedures, has proven to be a source of mesenchymal stem cells (MSCs) with increasing evidence. However, fallopian tube mucosa, which can be acquired via non-invasive procedures, is a previously unknown source of MSCs. In the present study, we explored the existence of MSCs in the human fallopian tube mucosa and also compared multipotent stem cells derived from fallopian tubes and fallopian tube mucosa according to their biological characteristics and therapeutic potential for treatment of autologous reproductive tract injury.

METHODS

Cells isolated from human fallopian tubes and fallopian tube mucosa were expanded and characterised by flow cytometry. The proliferative capacity of both cell types was measured by performing colony-forming unit-fibroblast and Cell Counting Kit-8 assays. Both cell types underwent in vitro adipogenic, chondrogenic, and osteogenic differentiation. The expression of osteocyte-, adipocyte-, and chondrocyte-related genes in the differentiated cell lineages was assessed by reverse transcription-polymerase chain reaction. The secretion of growth factors and immunomodulatory cytokines by both cell types were measured by enzyme-linked immunosorbent assays.

RESULTS

We found that MSCs existed in the fallopian tube mucosa. The comparison between human fallopian tube MSCs (hFTMSCs) and human fallopian tube mucosa MSCs (hFMMSCs) showed that hFTMSCs had a stronger proliferative capacity and shorter duplication time than hFMMSCs. Both cell types could be differentiated into adipocytes, osteoblasts, or chondrocytes in vitro. Real-time polymerase chain reaction analysis demonstrated that hFTMSCs displayed increased expression of osteogenic-specific genes compared with hFMMSCs, but the two types of cells showed no significant increase in the mRNA expression of adipogenic-specific or chondrogenic-specific genes. hFMMSCs and hFTMSCs robustly produced a variety of growth factors and immunomodulatory cytokines.

CONCLUSIONS

Human fallopian tube mucosa is a novel source of multipotent cells. hFMMSCs demonstrated stronger proliferative capacity and superior secretion of growth factors and immunomodulatory cytokines than hFTMSCs, making the former a better source of stem cells for the treatment of autologous reproductive tract injury. Compared with fallopian tube, fallopian tube mucosa has more wide-ranging applications and can be used to carry out autologous transplantation.

Increased ectopic fat cells in the longitudinal muscularis layer of the oviduct isthmus in obese Japanese Black cows

In obese humans, mesenchymal stem cells differentiate to become ectopic fat cells in muscles. These ectopic fat cells inhibit the contraction of vascular smooth muscles. Stem cells have been recently identified in the human oviduct, a structure important in reproduction. We therefore investigated the number of Oil Red O (ORO)-positive cells in the oviducts of control Japanese Black cows (n = 6; body condition score [BCS], 3.0 on a 5-point scale) compared to those with diet-induced obesity (n = 5; BCS, 4.0). We stained the ampulla and isthmus collected on the second day after ovulation with ORO and then counted the positive cells in each layer in 10 cross-sections of the ampulla or isthmus. The obese group (23.4 ± 3.4 in the 10 sections) had larger numbers of ORO-positive cells in the longitudinal muscularis of the isthmus (P < 0.05) than did the control group (15.0 ± 2.4). ORO-positive cells were also observed in all other layers of the isthmus and ampulla; however, the number of cells in these layers did not differ significantly between obese cows and controls. Whether this observed increase in ORO-positive cells in the oviducts of obese cows affects their reproduction warrants further study.