Cyclical endometrial repair and regeneration.

Uniquely among adult tissues, the human endometrium undergoes cyclical shedding, scar-free repair and regeneration during a woman's reproductive life. Therefore, it presents an outstanding model for study of such processes. This Review examines what is known of endometrial repair and regeneration following menstruation and parturition, including comparisons with wound repair and the influence of menstrual fluid components. We also discuss the contribution of endometrial stem/progenitor cells to endometrial regeneration, including the importance of the stem cell niche and stem cell-derived extracellular vesicles. Finally, we comment on the value of endometrial epithelial organoids to extend our understanding of endometrial development and regeneration, as well as therapeutic applications.

New concepts on the etiology of endometriosis.

Endometriosis is a serious, chronic disorder where endometrial tissue grows outside the uterus, causing severe pelvic pain and infertility. It affects 11% of women. Endometriosis is a multifactorial disorder of unclear etiology, although retrograde menstruation plays a major role. It has a genetic component with over 40 genetic risk factors mapped, although their mechanism of action is still emerging. New evidence suggests a role for retrograde menstruation of endometrial stem/progenitor cells, now that identifying markers of these cells are available. Recent lineage tracing and tissue clearing microscopy and 3D reconstruction has provided new understanding of endometrial glandular structure, particularly the horizontal orientation and interconnection of basalis glands. New sequencing technologies, particularly whole genome DNA sequencing are revealing somatic mutations, including in cancer driver genes, in normal and eutopic endometrium of patients with endometriosis, as well as ectopic endometriotic lesions. Methylome sequencing is offering insight into the regulation of genes and the role of the environmental factors. Single cell RNA sequencing reveals the transcriptome of individual endometrial cells, shedding new light on the diversity and range of cellular subpopulations of the major cell types present in the endometrium and in endometriotic lesions. New endometrial epithelial organoid cultures replicating glandular epithelium are providing tractable models for studying endometriosis. Organoids derived from menstrual fluid offer a non-invasive source of endometrial tissue and a new avenue for testing drugs and developing personalized medicine for treating endometriosis. These new approaches are rapidly advancing our understanding of endometriosis etiology.

Vaginal pressure sensor measurement during maximal voluntary pelvic floor contraction correlates with vaginal birth and pelvic organ prolapse-A pilot study.

AIMS: To measure the force applied along the anterior and posterior vaginal walls in a cohort of 46 patients measured by a fiber-optic pressure sensor and determine if this correlates with vaginal parity and pelvic organ prolapse (POP). METHODS: An intravaginal fiber-optic sensor measured pressure at nine locations along the anterior and posterior vaginal walls during a maximal voluntary pelvic floor muscle contraction (MVC). An automated probe dilation cycle measured the tissue resistance incorporating the vagina and surrounding anatomy. MVC and resting tissue resistance (RTR) were assessed between subjects grouped by the number of vaginal births and prolapse stage. RESULTS: A previous vaginal birth was associated with a significant threefold decrease in the overall anterior pressure measurement during MVC. Decreased anterior pressure measurements were observed at Sensors 1 and 3 (distal vagina) and, posteriorly at Sensors 4-6 (midvagina). Women with Stage 2 posterior prolapse exhibited a decreased MVC pressure in the midvagina than those with Stage 0/1. In this pilot study, there was no difference in the vaginal wall RTR according to previous vaginal birth or stage of prolapse. CONCLUSION: This pilot study found that a decrease in vaginal pressure measured during MVC is associated with vaginal birth and with posterior POP. Greater sample size is required to assess the role of resting tissue pressure measurement.

Identification and characterisation of maternal perivascular SUSD2+ placental mesenchymal stem/stromal cells.

Mesenchymal stem cells (MSCs) that meet the International Society for Cellular Therapy (ISCT) criteria are obtained from placental tissue by plastic adherence. Historically, no known single marker was available for isolating placental MSCs (pMSCs) from the decidua basalis. As the decidua basalis is derived from the regenerative endometrium, we hypothesised that SUSD2, an endometrial perivascular MSC marker, would purify maternal perivascular pMSC. Perivascular pMSCs were isolated from the maternal placenta using SUSD2 magnetic bead sorting and assessed for the colony-forming unit-fibroblasts (CFU-F), surface markers, and in vitro differentiation into mesodermal lineages. Multi-colour immunofluorescence was used to colocalise SUSD2 and α-SMA, a perivascular marker in the decidua basalis. Placental stromal cell suspensions comprised 5.1%SUSD2+ cells. SUSD2 magnetic bead sorting of the placental stromal cells increased their purity approximately two-fold. SUSD2+ pMSCs displayed greater CFU-F activity than SUSD2- stromal fibroblasts (pSFs). However, both SUSD2+ pMSC and SUSD2- pSF underwent mesodermal differentiation in vitro, and both expressed the ISCT surface markers. Higher percentages of cultured SUSD2+ pMSCs expressed the perivascular markers CD146, CD140b, and SUSD2 than SUSD2- pSFs. These findings suggest that SUSD2 is a single marker that enriches maternal pMSCs, suggesting they may originate from eMSC. Placental decidua basalis can be used as an alternative source of MSC for clinical translation in situations where there is no access to endometrial tissue.

Endometrial stem/progenitor cells in menstrual blood and peritoneal fluid of women with and without endometriosis.

RESEARCH QUESTION: Are endometrial stem/progenitor cells shed into uterine menstrual blood (UMB) and the peritoneal cavity in women with and without endometriosis during menstruation? DESIGN: Women with (n = 32) and without endometriosis (n = 29) at laparoscopy (total 61), carried out during the menstrual (n = 41) and non-menstrual phase (n = 20) were recruited. The UMB, peritoneal fluid and peripheral blood were analysed by clonogenicity assay and flow cytometry to quantify the concentrations of endometrial clonogenic cells, SUSD2+ mesenchymal stem cells (eMSC) and N-cadherin+ epithelial progenitor cells (eEPC). RESULTS: Clonogenic endometrial cells, eMSC and eEPC were found in most UMB samples at similar concentrations in women with and without endometriosis. In contrast, 62.5% of women with endometriosis and 75.0% without (controls) had clonogenic cells in peritoneal fluid samples during menses. The eMSC were present in the peritoneal fluid of 76.9% of women with endometriosis and 44.4% without, and eEPC were found in the peritoneal fluid of 60.0% of women with and 25.0% without endometriosis during menses. Median clonogenic, eMSC and eEPC concentrations in peritoneal fluid were not significantly different between groups. More clonogenic cells persisted beyond the menstrual phase in the peritoneal fluid of women with endometriosis (menstrual 119/ml [0-1360/ml] versus non-menstrual 8.5/ml [0-387/ml]; P = 0.277) compared with controls (menstrual 76.5/ml [1-1378/ml] versus non-menstrual 0/ml [0-14/ml]; P = 0.0362). No clonogenic endometrial cells were found in peripheral blood. CONCLUSIONS: Clonogenic endometrial cells, SUSD2+ eMSC and N-cadherin+ eEPC are present in UMB and the peritoneal fluid of women with and without endometriosis. Further study of the function of these cells may shed light on the cellular origins of endometriosis.

Endometrial mesenchymal stem/stromal cell modulation of T cell proliferation.

Perivascular mesenchymal stem/stromal cells can be isolated from the human endometrium using the surface marker SUSD2 and are being investigated for use in tissue repair. Mesenchymal stem/stromal cells from other tissues modulate T cell responses via mechanisms including interleukin-10, prostaglandin E2, TGF-ß1 and regulatory T cells. Animal studies demonstrate that endometrial mesenchymal stem/stromal cells can also modify immune responses to implanted mesh, but the mechanism/s they employ have not been explored. We examined the immunomodulatory properties of human endometrial mesenchymal stem/stromal cells on lymphocyte proliferation using mouse splenocyte cultures. Endometrial mesenchymal stem/stromal cells inhibited mitogen-induced lymphocyte proliferation in vitro in a dose-dependent manner. Inhibition of lymphocyte proliferation was not affected by blocking the mouse interleukin-10 receptor or inhibiting prostaglandin production. Endometrial mesenchymal stem/stromal cells continued to restrain lymphocyte proliferation in the presence of an inhibitor of TGF-ß receptors, despite a reduction in regulatory T cells. Thus, the in vitro inhibition of mitogen-induced lymphocyte proliferation by endometrial mesenchymal stem/stromal cells occurs by a mechanism distinct from the interleukin-10, prostaglandin E2, TGF-ß1 and regulatory T cell-mediated mechanisms employed by MSC from other tissues. eMSCs were shown to produce interleukin-17A and Dickkopf-1 which may contribute to their immunomodulatory properties. In contrast to MSC from other sources, systemic administration of endometrial mesenchymal stem/stromal cells did not inhibit swelling in a T cell-mediated model of skin inflammation. We conclude that, while endometrial mesenchymal stem/stromal cells can modify immune responses, their immunomodulatory repertoire may not be sufficient to restrain some T cell-mediated inflammatory events.

Bone Marrow Stem Cells Do Not Contribute to Endometrial Cell Lineages in Chimeric Mouse Models.

Studies from five independent laboratories conclude that bone marrow stem cells transdifferentiate into endometrial stroma, epithelium, and endothelium. We investigated the nature of bone marrow-derived cells in the mouse endometrium by reconstituting irradiated wild type recipients with bone marrow containing transgenic mTert-green fluorescent protein (GFP) or chicken ß-actin (Ch ß-actin)-GFP reporters. mTert-GFP is a telomerase marker identifying hematopoietic stem cells and subpopulations of epithelial, endothelial, and immune cells in the endometrium. Ch ß-actin-GFP is a ubiquitous reporter previously used to identify bone marrow-derived cells in the endometrium. Confocal fluorescence microscopy for GFP and markers of endometrial and immune cells were used to characterize bone marrow-derived cells in the endometrium of transplant recipients. No evidence of GFP+ bone marrow-derived stroma, epithelium, or endothelium was observed in the endometrium of mTert-GFP or Ch ß-actin-GFP recipients. All GFP+ cells detected in the endometrium were immune cells expressing the pan leukocyte marker CD45, including CD3+ T cells and F4/80+ macrophages. Further examination of the Ch ß-actin-GFP transplant model revealed that bone marrow-derived F4/80+ macrophages immunostained weakly for CD45. These macrophages were abundant in the stroma, infiltrated the epithelial and vascular compartments, and could easily be mistaken for bone marrow-derived endometrial cells. We conclude that it is unlikely that bone marrow cells are able to transdifferentiate into endometrial stroma, epithelium, and endothelium. This result has important therapeutic implications, as the expectation that bone marrow stem cells contribute directly to endometrial regeneration is shaping strategies designed to regenerate endometrium in Asherman's syndrome and to control aberrant endometrial growth in endometriosis. Stem Cells 2018;36:91-102.

Blended Nanostructured Degradable Mesh with Endometrial Mesenchymal Stem Cells Promotes Tissue Integration and Anti-Inflammatory Response in Vivo for Pelvic Floor Application.

The current urogynecological clinical meshes trigger unfavorable foreign body response which leads to graft failure in the long term. To overcome the present challenge, we applied a tissue engineering strategy using endometrial SUSD2+ mesenchymal stem cells (eMSCs) with high regenerative properties. This study delves deeper into foreign body response to SUSD2+ eMSC based degradable PLACL/gelatin nanofiber meshes using a mouse model targeted at understanding immunomodulation and mesh integration in the long term. Delivery of cells with nanofiber mesh provides a unique topography that enables entrapment of therapeutic cells for up to 6 weeks that promotes substantial cellular infiltration of host anti-inflammatory macrophages. As a result, degradation rate and tissue integration are highly impacted by eMSCs, revealing an unexpected level of implant integration over 6 weeks in vivo. From a clinical perspective, such immunomodulation may aid in overcoming the current challenges and provide an alternative to an unmet women's urogynecological health need.

Tissue engineering approaches for treating pelvic organ prolapse using a novel source of stem/stromal cells and new materials.

PURPOSE OF REVIEW: Nondegradable transvaginal polypropylene meshes for treating pelvic organ prolapse (POP) are now generally unavailable or banned. In this review, we summarize recent developments using tissue engineering approaches combining alternate degradable scaffolds with a novel source of mesenchymal stem/stromal cells from human endometrium (eMSC). RECENT FINDINGS: Tissue engineering constructs comprising immunomodulatory, reparative eMSC and biomimetic materials with nanoarchitecture are a promising approach for vaginal repair and improving outcomes of POP surgery. Culture expansion of eMSC that maintains them (and other MSC) in the undifferentiated state has been achieved using a small molecule transforming growth factor-ß receptor inhibitor, A83-01. The mechanism of action of A83-01 has been determined and its suitability for translation into the clinic explored. Novel blends of electrospun synthetic and natural polymers combined with eMSC shows this approach promotes host cell infiltration and slows biomaterial degradation that has potential to strengthen the vaginal wall during healing. Improving the preclinical ovine transvaginal surgical model by adapting the human clinical POP-Quantification system for selection of multiparous ewes with vaginal wall weakness enables assessment of this autologous eMSC/nanobiomaterial construct. SUMMARY: A tissue engineering approach using autologous eMSC with degradable nanobiomaterials offers a new approach for treating women with POP.

A fiber-optic sensor-based device for the measurement of vaginal integrity in women.

AIMS: Pelvic floor disorders (PFDs) in women are a major public health concern. Current clinical methods for assessing PFDs are either subjective or confounded by interference from intra-abdominal pressure (IAP). This study introduces an intravaginal probe that can determine distributed vaginal pressure during voluntary exercises and measures the degree of vaginal tissue support independent of IAP fluctuations. METHODS: An intravaginal probe was fabricated with 18 independent fiber-optic pressure transducers positioned along its upper and lower blades. Continuous pressure measurement along the anterior and posterior vaginal walls during the automated expansion of the probe enabled the resistance of the tissue to be evaluated as a function of displacement, in a manner reflecting the elastic modulus of the tissue. After validation in a simulated vaginal phantom, in vivo measurements were conducted in the relaxed state and during a series of voluntary exercises to gauge the utility of the device in women. RESULTS: The probe reliably detected variations in the composition of sub-surface material in the vaginal phantom. During in-vivo measurements the probe detected distributed tissue elasticity in the absence of IAP change. In addition, the distribution of pressure along both anterior and posterior vaginal walls during cough, Valsalva and pelvic floor contraction was clearly resolved with a large variation observed between subjects. CONCLUSIONS: Our data highlight the potential for the probe to assess the integrity of the vagina wall and support structures as an integrated functional unit. Further in vivo trials are needed to correlate data with clinical findings to assist in the assessment of PFDs.

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.

Comparative restoration of acute liver failure by menstrual blood stem cells compared with bone marrow stem cells in mice model.

BACKGROUND AIMS: The application of menstrual blood stem cells (MenSCs) in regenerative medicine is gaining increasing attention. The aim of this study was to investigate the therapeutic potential of MenSCs compared with bone marrow-derived stem cells (BMSCs) in an animal model of CCl4-induced acute hepatic failure. METHODS: Injured Balb/C mice were divided into multiple groups and received MenSCs, BMSCs or hepatocyte progenitor-like (HPL) cells derived from these cells. RESULTS: Tracking of green fluorescent protein-labeled cells showed homing of cells in injured areas of the liver. In addition, the liver engraftment of MenSCs was shown by immunofluorescence staining using anti-human mitochondrial antibody. Microscopically examination, periodic acid-Schiff and Masson's trichrome staining of liver sections demonstrated the considerable liver regeneration post-cell therapy in all groups. Assessment of serum parameters including aspartate aminotransferase, alanine aminotransferase, total bilirubin, urea and cholesterol at day 7 exhibited significant reduction, such that this downward trend continued significantly until day 30. The restoration of liver biochemical markers, changes in mRNA levels of hepatic markers and the suppression of inflammatory markers were more significant in the MenSC-treated group compared with the BMSC-treated group. On the other hand, HPL cells in reference to undifferentiated cells had better effectiveness in the treatment of the acute liver injury. CONCLUSIONS: Our data show that MenSCs may be considered an appropriate alternative stem cell population to BMSCs for treatment of acute liver failure.

The impact of uterine immaturity on obstetrical syndromes during adolescence.

Pregnant nulliparous adolescents are at increased risk, inversely proportional to their age, of major obstetric syndromes, including preeclampsia, fetal growth restriction, and preterm birth. Emerging evidence indicates that biological immaturity of the uterus accounts for the increased incidence of obstetrical disorders in very young mothers, possibly compounded by sociodemographic factors associated with teenage pregnancy. The endometrium in most newborns is intrinsically resistant to progesterone signaling, and the rate of transition to a fully responsive tissue likely determines pregnancy outcome during adolescence. In addition to ontogenetic progesterone resistance, other factors appear important for the transition of the immature uterus to a functional organ, including estrogen-dependent growth and tissue-specific conditioning of uterine natural killer cells, which plays a critical role in vascular adaptation during pregnancy. The perivascular space around the spiral arteries is rich in endometrial mesenchymal stem-like cells, and dynamic changes in this niche are essential to accommodate endovascular trophoblast invasion and deep placentation. Here we evaluate the intrinsic (uterine-specific) mechanisms that predispose adolescent mothers to the great obstetrical syndromes and discuss the convergence of extrinsic risk factors that may be amenable to intervention.

Vaginal wall weakness in parous ewes: a potential preclinical model of pelvic organ prolapse.

INTRODUCTION AND HYPOTHESIS: Ewes develop pelvic organ prolapse (POP) and may be a suitable model for preclinical studies evaluating cell-based therapies for POP. The aim of this study was to establish a clinical score of vaginal weakness and to compare POP Quantification System (POP-Q) values in conscious nulliparous and parous ewes and determine whether ewes are a suitable POP model. METHODS: Ewes (n = 114) were examined while conscious, without sedation, and standing in a V conveyer by adapting the human POP-Q measurement. Ovine POP was defined as descent to the introitus from POP-Q points Aa 3 cm above the introitus on the anterior wall, Ap 3 cm above the introitus on the posterior wall, or increased Ba anterior wall descent above the urethra (≥0). A test-retest showed good inter- and intrarater reliability. RESULTS: There was no evidence of tissue mobility at Aa, Ap, Ba (all -3 cm) in nulliparous ewes (n = 14). In contrast, multiparous ewes had a median of -1 and interquartile range (IQR) (-2 to 0) for Aa, [0 (-1 to 0)] for Ap and [0 (-2.75 to 0)] for Ba (n = 33; P < 0.0001 in comparison with nulliparous) ewes. Ovine vaginal displacement was seen in 50.9 % of parous ewes and was strongly associated with parity (P = 0.003). CONCLUSIONS: A modified POP-Q in conscious ewes was established showing that the vaginal wall of parous animals has similar regions of weakness as do women and may be similarly related to parity. Ewes appear to be a representative preclinical model of human vaginal prolapse.

The mouse endometrium contains epithelial, endothelial and leucocyte populations expressing the stem cell marker telomerase reverse transcriptase.

STUDY HYPOTHESIS: The mouse endometrium harbours stem/progenitor cells that express the stem cell marker mouse telomerase reverse transcriptase (mTert). STUDY FINDING: We used a mouse carrying a transgenic reporter for mTert promoter activity to identify rare endometrial populations of epithelial and endothelial cells that express mTert. WHAT IS KNOWN ALREADY: Stem/progenitor cells are hypothesized to be responsible for the remarkable regenerative capacity of the endometrium, but the lack of convenient endometrial stem/progenitor markers in the mouse has hampered investigations into the identity of these cells. STUDY DESIGN, SAMPLES/MATERIALS, METHODS: A mouse containing a green fluorescent protein (GFP) reporter under the control of the telomerase reverse transcriptase promoter (mTert-GFP) was used to identify potential stem/progenitor cells in the endometrium. mTert promoter activity was determined using fluorescence microscopy and flow cytometry to identify GFP(+) cells. GFP(+) cells were examined for epithelial, stromal, endothelial, leucocyte and proliferation markers and bromodeoxyuridine retention to determine their identity. The endometrium of ovariectomized mice was compared to that of intact cycling mice to establish the role of ovarian hormones in maintaining mTert-expressing cells. MAIN RESULTS AND THE ROLE OF CHANCE: We found that mTert-GFP is expressed by rare luminal and glandular epithelial cells (0.3% of epithelial cells by flow cytometry), rare CD45(-) cells in the stromal compartment (0.028 ± 0.010% of stromal cells by microscopy) and many CD45(+) leucocytes. Ovariectomy resulted in significant decrease of mTert-GFP(+) epithelial cells (P = 0.029 for luminal epithelium; P = 0.034 for glandular epithelium) and a decrease in the percentage of mTert-GFP(+) CD45(+) leucocytes in the stromal compartment (P = 0.015). However, CD45(-) mTert-GFP(+) cells in the stromal compartment were maintained in ovariectomized mice. This population is enriched for cells bearing the endothelial marker CD31 (10.3% of CD90(-) CD45(-) and 97.8% CD90(+) CD45(-) by flow cytometry). CD45(-) mTert-GFP(+) cells also immunostained for the endothelial marker von Willebrand factor. These results suggest that the endometrial epithelium and vasculature are foci of stem/progenitor activity and provide a system to investigate molecular mechanisms involved in endometrial regeneration and repair. LIMITATIONS, REASONS FOR CAUTION: The stem/progenitor activity of endometrial mTert-GFP(+) cells needs to be experimentally verified. WIDER IMPLICATIONS OF THE FINDINGS: The identification and characterization of mTert-expressing progenitor cells in the mouse will facilitate the identification of equivalent populations in the human endometrium that are likely to be involved in endometrial function, fertility and disease. LARGE-SCALE DATA: Not applicable. STUDY FUNDING AND COMPETING INTERESTS: This study was funded by National Health and Medical Research Council (NHMRC) of Australia grants (1085435, C.E.G., J.A.D.), 1021127 (C.E.G.), NHMRC Senior Research Fellowship (1042298, C.E.G.), the Victorian Infrastructure Support Program, U.S. National Institutes of Health grant R01 DK084056 (D.T.B.) and the Harvard Stem Cell Institute (D.T.B.). The authors have no conflicts of interest to declare.

Changes in pelvic organ prolapse mesh mechanical properties following implantation in rats.

BACKGROUND: Pelvic organ prolapse (POP) is a multifactorial disease that manifests as the herniation of the pelvic organs into the vagina. Surgical methods for prolapse repair involve the use of a synthetic polypropylene mesh. The use of this mesh has led to significantly higher anatomical success rates compared with native tissue repairs, and therefore, despite recent warnings by the Food and Drug Administration regarding the use of vaginal mesh, the number of POP mesh surgeries has increased over the last few years. However, mesh implantation is associated with higher postsurgery complications, including pain and erosion, with higher consecutive rates of reoperation when placed vaginally. Little is known on how the mechanical properties of the implanted mesh itself change in vivo. It is assumed that the mechanical properties of these meshes remain unchanged, with any differences in mechanical properties of the formed mesh-tissue complex attributed to the attached tissue alone. It is likely that any changes in mesh mechanical properties that do occur in vivo will have an impact on the biomechanical properties of the formed mesh-tissue complex. OBJECTIVE: The objective of the study was to assess changes in the multiaxial mechanical properties of synthetic clinical prolapse meshes implanted abdominally for up to 90 days, using a rat model. Another objective of the study was to assess the biomechanical properties of the formed mesh-tissue complex following implantation. STUDY DESIGN: Three nondegradable polypropylene clinical synthetic mesh types for prolapse repair (Gynemesh PS, Polyform Lite, and Restorelle) and a partially degradable polypropylene/polyglecaprone mesh (UltraPro) were mechanically assessed before and after implantation (n = 5/ mesh type) in Sprague Dawley rats for 30 (Gynemesh PS, Polyform Lite, and Restorelle) and 90 (UltraPro and Polyform Lite) days. Stiffness and permanent extension following cyclic loading, and breaking load, of the preimplanted mesh types, explanted mesh-tissue complexes, and explanted meshes were assessed using a multi-axial (ball-burst) method. RESULTS: The 4 clinical meshes varied from each other in weight, thickness, porosity, and pore size and showed significant differences in stiffness and breaking load before implantation. Following 30 days of implantation, the mechanical properties of some mesh types altered, with significant decreases in mesh stiffness and breaking load, and increased permanent extension. After 90 days these changes were more obvious, with significant decreases in stiffness and breaking load and increased permanent extension. Similar biomechanical properties of formed mesh-tissue complexes were observed for mesh types of different preimplant stiffness and structure after 90 days implantation. CONCLUSION: This is the first study to report on intrinsic changes in the mechanical properties of implanted meshes and how these changes have an impact on the estimated tissue contribution of the formed mesh-tissue complex. Decreased mesh stiffness, strength, and increased permanent extension following 90 days of implantation increase the biomechanical contribution of the attached tissue of the formed mesh-tissue complex more than previously thought. This needs to be considered when using meshes for prolapse repair.

Endometrial side population cells: potential adult stem/progenitor cells in endometrium.

Uterine endometrium is one of the most important organs for species preservation. However, the physiology of human endometrium remains poorly understood, because the human endometrium undergoes rapid and large changes during each menstrual cycle and it is very difficult to investigate human endometrium as one organ. This remarkable regenerative capacity of human endometrium strongly suggests the existence of adult stem cells, and physiology of endometrium cannot be explained without adult stem cells. Therefore, investigating endometrial stem/progenitor cells should lead to a breakthrough in understanding the normal endometrial physiology and the pathophysiology of endometrial neoplastic disorders, such as endometriosis and endometrial cancer. Several cell populations have been discovered as putative endometrial stem/progenitor cells. Emerging evidence reveals that the endometrial side population (SP) is one of the potential endometrial stem/progenitor populations. Of all the endometrial stem/progenitor cell candidates, the endometrial SP (ESP) is best investigated in vitro and in vivo, and has the largest number of references. In this review, we provide an overview of the accumulating evidence for the ESP cells, both directly from human endometria and from cultured endometrial cells. Furthermore, SP cells are compared to other potential stem/progenitor cells, and we discuss their stem cell properties. We also discuss the difficulties and unsolved issues in endometrial stem cell biology.

A Review of Current Animal Models for the Study of Cervical Dysplasia and Cervical Carcinoma.

Cancer research has long relied on animal models for the study of disease mechanisms and new therapeutics. Future cancer treatments are likely to rely heavily on patient-derived xenograft models to develop novel treatments and tailor regimens to individual patient needs. However, specific models for cervical cancer and cervical dysplasia are limited. Only 3 models have been described in the published literature. A transgenic model for cervical cancer has allowed for the study of the differential contributions of the human papillomavirus 16 proteins E6 and E7 during oncogenesis. This model has also shown dysplasia development, although this has received little attention. A patient-derived tumor xenograft model where cervical cancer tissue is transplanted to the subcutaneous and orthotopic sites has been described. Here we review the reported transgenic and xenograft models, their strengths and limitations, and highlight the potential for the development of improved models to study cervical neoplasia.