Effect of estradiol on mouse uterine epithelial cell transepithelial resistance (TER)

Vaginal irritation testing-prospects of human organotypic vaginal tissue culture models

Personal lubricants intended for local or systemic delivery via the vaginal route can induce vaginal irritation, damage the vaginal epithelial barrier which can enhance microbial entry, induce inflammation, and alter the microbiome of the vaginal ecosystem. Therefore, manufacturers of personal lubricants and medical devices are required to show biocompatibility and safety assessment data to support regulatory decision-making within a specified context of use. Furthermore, due to ethical concerns and the introduction of the 7th amendment of the European Council Directive which bans animal testing for cosmetic ingredients and products coupled with the Food and Drug Administration modernization Act 2.0 guidelines, there is a wave of drive to develop alternative test methods to predict human responses to chemical or formulation exposure. In this framework, there is a potential to use three-dimensional organotypic human vaginal-ectocervical tissue models as a screening tool to predict the vaginal irritation potential of personal lubricants and medicaments. To be physiologically relevant, the in vitro tissue models need to be reconstructed using primary epithelial cells of the specific organ or tissue and produce organ-like structure and functionality that recapitulate the in vivo-like responses. Through the years, progress has been made and vaginal tissue models are manufactured under controlled conditions with a specified performance criterion, which leads to a high level of reproducibility and reliability. The utility of vaginal tissue models has been accelerated in the last 20 years with an expanded portfolio of applications ranging from toxicity, inflammation, infection to drug safety, and efficacy studies. This article provides an overview of the state of the art of diversified applications of reconstructed vaginal tissue models and highlights their utility as a tool to predict vaginal irritation potential of feminine care products.

Long-Term Maintenance of Viable Human Endometrial Epithelial Cells to Analyze Estrogen and Progestin Effects

There are fewer investigations conducted on human primary endometrial epithelial cells (HPEECs) compared to human primary endometrial stromal cells (HPESCs). One of the main reasons is the scarcity of protocols enabling prolonged epithelial cell culture. Even though it is possible to culture HPEECs in 3D over a longer period of time, it is technically demanding. In this study, we successfully established a highly pure, stable, and long-term viable human conditionally reprogrammed endometrial epithelial cell line, designated as eCRC560. These cells stained positive for epithelial markers, estrogen and progesterone receptors, and epithelial cell-cell contacts but negative for stromal and endothelial cell markers. Estradiol (ES) reduced the abundance of ZO-1 in a time- and dose-dependent manner, in contrast to the dose-dependent increase with the progestin dienogest (DNG) when co-cultured with HPESCs. Moreover, ES significantly increased cell viability, cell migration, and invasion of the eCRC560 cells; all these effects were inhibited by pretreatment with DNG. DNG withdrawal led to a significantly disrupted monolayer of eCRC560 cells in co-culture with HPESCs, yet it markedly increased the adhesion of eCRC560 to the human mesothelial MeT-5A cells. The long-term viable eCRC560 cells are suitable for in vitro analysis of HPEECs to study the epithelial compartment of the human endometrium and endometrial pathologies.

Endometrial responses to bacterial and viral infection: a scoping review

BACKGROUND

The endometrium is a highly dynamic tissue that undergoes dramatic proliferation and differentiation monthly in order to prepare the uterus for implantation and pregnancy. Intrauterine infection and inflammation are being increasingly recognized as potential causes of implantation failure and miscarriage, as well as obstetric complications later in gestation. However, the mechanisms by which the cells of the endometrium respond to infection remain understudied and recent progress is slowed in part owing to similar overlapping studies being performed in different species.

OBJECTIVE AND RATIONALE

The aim of this scoping review is to systematically summarize all published studies in humans and laboratory animals that have investigated the innate immune sensing and response of the endometrium to bacteria and viruses, and the signaling mechanisms involved. This will enable gaps in our knowledge to be identified to inform future studies.

SEARCH METHODS

The Cochrane Library, Ovid Embase/Medline, PubMed, Scopus, Google Scholar, and Web of Science databases were searched using a combination of controlled and free text terms for uterus/endometrium, infections, and fertility to March 2022. All primary research papers that have reported on endometrial responses to bacterial and viral infections in the context of reproduction were included. To focus the scope of the current review, studies in domesticated animals, included bovine, porcine, caprine, feline, and canine species were excluded.

OUTCOMES

This search identified 42 728 studies for screening and 766 full-text studies were assessed for eligibility. Data was extracted from 76 studies. The majority of studies focused on endometrial responses to Escherichia coli and Chlamydia trachomatis, with some studies of Neisseria gonorrhea, Staphylococcus aureus, and the Streptococcus family. Endometrial responses have only been studied in response to three groups of viruses thus far: HIV, Zika virus, and the herpesvirus family. For most infections, both cellular and animal models have been utilized in vitro and in vivo, focusing on endometrial production of cytokines, chemokines, and antiviral/antimicrobial factors, and the expression of innate immune signaling pathway mediators after infection. This review has identified gaps for future research in the field as well as highlighted some recent developments in organoid systems and immune cell co-cultures that offer new avenues for studying endometrial responses to infection in more physiologically relevant models that could accelerate future findings in this area.

WIDER IMPLICATIONS

This scoping review provides an overarching summary and benchmark of the current state of research on endometrial innate immune responses to bacterial and viral infection. This review also highlights some exciting recent developments that enable future studies to be designed to deepen our understanding of the mechanisms utilized by the endometrium to respond to infection and their downstream effects on uterine function.

Characterization of Myeloperoxidase in the Healthy Equine Endometrium

Myeloperoxidase (MPO), as a marker of neutrophil activation, has been associated with equine endometritis. However, in absence of inflammation, MPO is constantly detected in the uterine lumen of estrous mares. The aim of this study was to characterize MPO in the uterus of mares under physiological conditions as a first step to better understand the role of this enzyme in equine reproduction. Total and active MPO concentrations were determined, by ELISA and SIEFED assay, respectively, in low-volume lavages from mares in estrus (n = 26), diestrus (n = 18) and anestrus (n = 8) in absence of endometritis. Immunohistochemical analysis was performed on 21 endometrial biopsies randomly selected: estrus (n = 11), diestrus (n = 6) and anestrus (n = 4). MPO, although mostly enzymatically inactive, was present in highly variable concentrations in uterine lavages in all studied phases, with elevated concentrations in estrus and anestrus, while in diestrus, concentrations were much lower. Intracytoplasmic immunoexpression of MPO was detected in the endometrial epithelial cells, neutrophils and glandular secretions. Maximal expression was observed during estrus in mid and basal glands with a predominant intracytoplasmic apical reinforcement. In diestrus, immunopositive glands were sporadic. In anestrus, only the luminal epithelium showed residual MPO immunostaining. These results confirm a constant presence of MPO in the uterine lumen of mares in absence of inflammation, probably as part of the uterine mucosal immune system, and suggest that endometrial cells are a source of uterine MPO under physiological cyclic conditions.

Animal Models and Alternatives in Vaginal Research: a Comparative Review

While developments in gynecologic health research continue advancing, relatively few groups specifically focus on vaginal tissue research for areas like wound healing, device development, and/or drug toxicity. Currently, there is no standardized animal or tissue model that mimics the full complexity of the human vagina. Certain practical factors such as appropriate size and anatomy, costs, and tissue environment vary across species and moreover fail to emulate all aspects of the human vagina. Thus, investigators are tasked with compromising specific properties of the vaginal environment as it relates to human physiology to suit their particular scientific question. Our review aims to facilitate the appropriate selection of a model aptly addressing a particular study by discussing pertinent vaginal characteristics of conventional animal and tissue models. In this review, we first cover common laboratory animals studied in vaginal research-mouse, rat, rabbit, minipig, and sheep-as well as human, with respect to the estrus cycle and related hormones, basic reproductive anatomy, the composition of vaginal layers, developmental epithelial origin, and microflora. In light of these relevant comparative metrics, we discuss potential selection criteria for choosing an appropriate animal vaginal model. Finally, we allude to the exciting prospects of increasing biomimicry for in vitro applications to provide a framework for investigators to model, interpret, and predict human vaginal health.

Regulation of mucosal immunity in the female reproductive tract: the role of sex hormones in immune protection against sexually transmitted pathogens

The immune system in the female reproductive tract (FRT) does not mount an attack against human immunodeficiency virus (HIV) or other sexually transmitted infections (STI) with a single endogenously produced microbicide or with a single arm of the immune system. Instead, the body deploys dozens of innate antimicrobials to the secretions of the FRT. Working together, these antimicrobials along with mucosal antibodies attack viral, bacterial, and fungal targets. Within the FRT, the unique challenges of protection against sexually transmitted pathogens coupled with the need to sustain the development of an allogeneic fetus, has evolved in such a way that sex hormones precisely regulate immune function to accomplish both tasks. The studies presented in this review demonstrate that estradiol (E2 ) and progesterone secreted during the menstrual cycle act both directly and indirectly on epithelial cells, fibroblasts and immune cells in the reproductive tract to modify immune function in a way that is unique to specific sites throughout the FRT. As presented in this review, studies from our laboratory and others demonstrate that the innate and adaptive immune systems are under hormonal control, that protection varies with the stage of the menstrual cycle and as such, is dampened during the secretory stage of the cycle to optimize conditions for fertilization and pregnancy. In doing so, a window of STI vulnerability is created during which potential pathogens including HIV enter the reproductive tract to infect host targets.

Estradiol regulation of constitutive and keratinocyte growth factor-induced CCL20 and CXCL1 secretion by mouse uterine epithelial cells

PROBLEM

Estradiol can directly affect epithelial cells or indirectly affect epithelial cells via stromal fibroblast secretion of growth factors, such as keratinocyte growth factor (KGF). The purpose of the present study was to determine whether estradiol regulates constitutive as well as KGF-induced uterine epithelial cell secretion of CCL20 and CXCL1.

METHOD OF STUDY

Freshly isolated and polarized uterine epithelial cells from Balb/c mice were cultured with estradiol in the presence or absence of KGF. CCL20 and CXCL1 were measured by ELISA.

RESULTS

Estradiol inhibited CCL20 secretion by freshly isolated and polarized uterine epithelial cells in the presence or absence of KGF. Unexpectedly, it enhanced KGF-induced CXCL1 secretion beyond that seen with KGF alone. Estradiol increased CXCL1 secretion at 24 hr and inhibited CCL20 at 48 hr. The effects of estradiol are specific in that progesterone, cortisol, dihydrotestosterone, and aldosterone had no effect on either CCL20 or CXCL1 secretion. The inhibitory effect of estradiol on CCL20 secretion was reversed with ICI 182,780, an estrogen receptor antagonist, indicating that this effect is estrogen receptor mediated.

CONCLUSIONS

Our data indicate that estradiol is important in regulating the effects of KGF on mouse uterine epithelial cell secretion of CCL20 and CXCL1.

Effect of oestradiol and pathogen-associated molecular patterns on class II-mediated antigen presentation and immunomodulatory molecule expression in the mouse female reproductive tract

Cells of the female reproductive tract (FRT) can present antigen to naive and memory T cells. However, the effects of oestrogen, known to modulate immune responses, on antigen presentation in the FRT remain undefined. In the present study, DO11.10 T-cell antigen receptor transgenic mice specific for the class II MHC-restricted ovalbumin (OVA) 323-339 peptide were used to study the effects of oestradiol and pathogen-associated molecular patterns on antigen presentation in the FRT. We report here that oestradiol inhibited antigen presentation of OVA by uterine epithelial cells, uterine stromal cells and vaginal cells to OVA-specific memory T cells. When ovariectomized animals were treated with oestradiol for 1 or 3 days, antigen presentation was decreased by 20-80%. In contrast, incubation with PAMP increased antigen presentation by epithelial cells (Pam(3)Cys), stromal cells (peptidoglycan, Pam(3)Cys) and vaginal cells (Pam(3)Cys). In contrast, CpG inhibited both stromal and vaginal cell antigen presentation. Analysis of mRNA expression by reverse transcription PCR indicated that oestradiol inhibited CD40, CD80 and class II in the uterus and CD40, CD86 and class II in the vagina. Expression in isolated uterine and vaginal cells paralleled that seen in whole tissues. In contrast, oestradiol increased polymeric immunoglobulin receptor mRNA expression in the uterus and decreased it in the vagina. These results indicate that antigen-presenting cells in the uterus and vagina are responsive to oestradiol, which inhibits antigen presentation and co-stimulatory molecule expression. Further, these findings suggest that antigen-presenting cells in the uterus and vagina respond to selected Toll-like receptor agonists with altered antigen presentation.

Haem oxygenase-1 dictates intrauterine fetal survival in mice via carbon monoxide

Pregnancy establishment implies the existence of a highly vascularized and transient organ, the placenta, which ensures oxygen supply to the fetus via haemoproteins. Haem metabolism, including its catabolism by haem oxygenase-1 (HO-1), should be of importance in maintaining the homeostasis of haemoproteins and controlling the deleterious effects associated with haem release from maternal or fetal haemoglobins, thus ensuring placental function and fetal development. We demonstrate that HO-1 expression is essential to promote placental function and fetal development, thus determining the success of pregnancy. Hmox1 deletion in mice has pathological consequences for pregnancy, namely suboptimal placentation followed by intrauterine fetal growth restriction (IUGR) and fetal lethality. These pathological effects can be mimicked by administration of exogenous haem in wild-type mice. Fetal and maternal HO-1 is required to prevent post-implantation fetal loss through a mechanism that acts independently of maternal adaptive immunity and hormones. The protective HO-1 effects on placentation and fetal growth can be mimicked by the exogenous administration of carbon monoxide (CO), a product of haem catabolism by HO-1 that restores placentation and fetal growth. In a clinical relevant model of IUGR, CO reduces the levels of free haem in circulation and prevents fetal death. We unravel a novel physiological role for HO-1/CO in sustaining pregnancy which aids in understanding the biology of pregnancy and reveals a promising therapeutic application in the treatment of pregnancy pathologies.

Sex hormone regulation of innate immunity in the female reproductive tract: the role of epithelial cells in balancing reproductive potential with protection against sexually transmitted pathogens

The immune system in the female reproductive tract (FRT) does not mount an attack against HIV or other sexually transmitted infections (STI) with a single endogenously produced microbicide or with a single arm of the immune system. Instead, the body deploys dozens of innate antimicrobials to the secretions of the female reproductive tract. Working together, these antimicrobials along with mucosal antibodies attack many different viral, bacterial and fungal targets. Within the FRT, the unique challenges of protection against sexually transmitted pathogens coupled with the need to sustain the development of an allogeneic fetus have evolved in such a way that sex hormones precisely regulate immune function to accomplish both tasks. The studies presented in this review demonstrate that estradiol and progesterone secreted during the menstrual cycle act both directly and indirectly on epithelial cells and other immune cells in the reproductive tract to modify immune function in a way that is unique to specific sites throughout the FRT. As presented in this review, studies from our laboratory and others demonstrate that the innate immune response is under hormonal control, varies with the stage of the menstrual cycle, and as such is suppressed at mid-cycle to optimize conditions for successful fertilization and pregnancy. In doing so, a window of STI vulnerability is created during which potential pathogens including HIV enter the reproductive tract to infect host targets.

Matrix metalloproteinase induction by relaxin causes cartilage matrix degradation in target synovial joints

Our long-term goal is to understand the mechanisms by which relaxin and estrogen potentially contribute to joint diseases, particularly those afflicting the fibrocartilaginous temporomandibular joint (TMJ). Previously, we showed that relaxin produces a dose-dependent induction of tissue-degrading enzymes of the matrix metalloproteinase (MMP) family, specifically MMP-1 (collagenase-1), MMP-3 (stromelysin-1), MMP-9 (92-kDa gelatinase), and MMP-13 (collagenase-3) in cell isolates and tissue explants from TMJ fibrocartilage. The induction of these MMPs is accompanied by loss of collagen and glycosaminoglycans (GAGs), which was blocked by a pan-MMP inhibitor. We also found the targeted in vivo loss of collagen and GAGs in TMJ discs of ovariectomized rabbits treated with beta-estradiol, relaxin, or both hormones together. Progesterone attenuated the induction of MMPs and matrix loss by relaxin and estrogen. The modulation of matrix composition in TMJ fibrocartilage by these hormones was similar to that observed in the pubic symphysis and differed from that of the knee meniscus. The two target tissues showing the greatest modulation of MMPs and matrix loss, namely, the TMJ disc and pubic symphysis, had similar expression profiles of the estrogen receptors alpha and beta, relaxin-1 receptor (RXFP1, LGR7), and insulin-like peptide 3 receptor (RXFP2, LGR8) and these profiles differed from those in cells from the knee meniscus. These findings suggest a novel model for targeted tissue turnover of cartilage of specific joints through hormone-mediated induction of select MMPs.

Distribution of eosinophil granulocytes and mast cells in the reproductive tract of female goats in the preimplantation phase

Changes in eosinophil granulocytes and mast cells post-insemination may affect conceptus implantation, but information regarding the numbers of such cells in the mammalian reproductive tract is limited. This study investigated the preimplantation distribution of eosinophil granulocytes and mast cells (MCs) in the reproductive tract organs of female goats. Uterus, uterine cervix and uterine tubes samples were obtained at slaughter. Cornu uteri were washed in phosphate buffer solution (each animal contained at least one embryo). Tissues were fixed in 10% neutral buffered formol, Carnoy solution and Mota's fixative (basic lead acetate) for 48 h and embedded in paraffin. Six-micrometre-thick sections were stained with Congo red (for eosinophil granulocytes) and toluidine blue in 1% aqueous solution at pH 1.0 for 5 min (for MCs). In the uterus, MCs occurred in highest numbers in the myometrium. Higher MC numbers were observed in uterus, uterine and uterine tubes in the preimplantation (experimental) group (cycle synchronised through 7 days intravaginal sponge with 0.3 g P(4)) compared with the control group (P < 0.05). Eosinophil granulocyte numbers were significantly higher in the experimental group than in the control group (P < 0.05). These results indicate preimplantation-related changes in numbers of eosinophil granulocytes and MCs in goat reproductive tract organs.

Estradiol selectively regulates innate immune function by polarized human uterine epithelial cells in culture

The goal of this study was to examine the role of E(2) in regulating innate immune protection by human uterine epithelial cells (UECs). Recognizing that UECs produce cytokines and chemokines to recruit and activate immune cells as well as viral and bacterial antimicrobials, we sought to examine the effect of E(2) on constitutive and Toll-like receptor (TLR) agonist (lipopolysaccharide (LPS) and poly (I:C))-induced immune responses. The secretion by polarized UECs in culture of interleukin (IL)-6, macrophage inhibitory factor (MIF), and secretory leukocyte protease inhibitor (SLPI) was examined as well as the mRNA expression of human beta-defensin-2 (HBD2), tumor necrosis factor (TNF)-alpha, IL-8, and nuclear factor (NF)-kB. When incubated with E(2) for 24-48 h, we found that E(2) stimulated UEC secretion of SLPI (fourfold) and mRNA expression of HBD2 (fivefold). Moreover, when antibacterial activity in UEC secretions was measured using Staphylococcus aureus, E(2) increased the secretion of soluble factor(s) with antibacterial activity. In contrast, E(2) had no effect on constitutive secretion of proinflammatory cytokines and chemokines by UECs but completely inhibited LPS- and poly (I:C)-induced secretion of MIF, IL-6, and IL-8. Estradiol also reversed the stimulatory effects of IL-1beta on mRNA expression of TNF-alpha, IL-8, and NF-kB by 85, 95, and 70%, respectively. As SLPI is known to inhibit NF-kB expression, these findings suggest that E(2) inhibition of proinflammatory cytokines may be mediated through SLPI regulation of NF-kB. Overall, these findings indicate that the production of cytokines, chemokines, and antimicrobials by UECs are differentially regulated by E(2). Further, it suggests that with E(2) regulation, epithelial cells that line the uterine cavity have evolved immunologically to be sensitive to viral and bacterial infections as well as the constraints of procreation.

Expression of Toll-like receptors in murine vaginal epithelium is affected by the estrous cycle and stromal cells

Vaginal epithelium is regulated by female sex hormones and serves as the first line of innate immune defense against sexually transmitted infections (STIs). This occurs in part through recognition of pathogens via Toll-like receptors (TLRs); however, the expression and role of TLRs in reproductive tract immunity are poorly understood. Here, we have compared the effect of the estrous cycle and treatment with DepoProvera (Depo) on TLR mRNA expression in whole mouse vaginal tissue, vaginal epithelium isolated using laser capture microdissection (LCM) and in primary vaginal epithelial cells (ECs) grown in vitro. Distinct patterns of TLR expression were observed in LCM-isolated vaginal epithelium versus whole vaginal tissue. Absolute quantitative RT-PCR of LCM vaginal epithelium showed that expression of all TLRs, except TLR11, was significantly increased during the diestrus phase or following Depo-treatment. TLR2 mRNA showed an extraordinary increase in expression in both diestrus and following Depo-treatment (23-fold) over that in the estrus phase. Although TLR2 protein was expressed at similar levels over the estrous cycle in whole vaginal tissue, full-length TLR2 protein was only detected during diestrus or after Depo-treatment in LCM-isolated vaginal epithelium. Distinct TLR mRNA expression profiles were seen also in primary vaginal ECs in vitro and only expression of TLR2 was significantly decreased in ECs cultured in the presence of stromal cells. Thus, TLR expression in vaginal ECs is regulated by sex hormones and can be affected by stromal cells. These findings contribute to our understanding of innate immune defense against STIs and enhance the quality of woman's reproductive health.

Effect of oestradiol on PAMP-mediated CCL20/MIP-3 alpha production by mouse uterine epithelial cells in culture

The present study was undertaken to establish whether mouse uterine epithelial cells produce CCL20/macrophage inflammatory protein 3 alpha (CCL20/MIP-3 alpha) and to determine whether secretion is under hormonal control and influenced by pathogen-associated molecular patterns (PAMPs). In the absence of PAMPs, polarized uterine epithelial cells grown to confluence on cell culture inserts constitutively secreted CCL20/MIP-3 alpha with preferential accumulation into the apical compartment. When epithelial cells were treated with the Toll-like receptor (TLR) agonists Pam3Cys (TLR2/1), peptidoglycan (TLR2/6) or lipopolysaccharide (LPS; TLR4), CCL20/MIP-3 alpha increased rapidly (4 hr) in both apical and basolateral secretions. Time-course studies indicated that responses to PAMPs added to the apical surface persisted for 12-72 hr. Stimulation with loxoribin (TLR7) and DNA CpG motif (TLR9) increased basolateral but not apical secretion of CCL20/MIP-3 alpha. In contrast, the viral agonist Poly(I:C) (TLR3) had no effect on either apical or basolateral secretion. In other studies, we found that oestradiol added to the culture media decreased the constitutive release of CCL20/MIP-3 alpha. Moreover, when added to the culture media along with LPS, oestradiol inhibited LPS-induced increases in CCL20/MIP-3 alpha secretion into both the apical and basolateral compartments. In summary, these results indicate that CCL20/MIP-3 alpha is produced in response to PAMPs. Since CCL20/MIP-3 alpha is chemotactic for immature dendritic cells, B cells and memory T cells and has antimicrobial properties, these studies suggest that CCL20/MIP-3 alpha production by epithelial cells, an important part of the innate immune defence in the female reproductive tract, is under hormonal control and is responsive to microbial challenge.

Temporal expression profiling of the uterine luminal epithelium of the pseudo-pregnant mouse suggests receptivity to the fertilized egg is associated with complex transcriptional changes

BACKGROUND

The molecular basis of changes underlying the altered sensitivity of the uterine luminal epithelium (LE) to the embryo over the peri-implantation period is not fully understood.

METHODS

Microarray analysis was performed on purified LE isolated from the pseudo-pregnant mouse uterus at 12-h intervals from pre-receptivity through the implantation window to refractoriness. The aim was to identify genes whose expression changes in the LE during this period.

RESULTS

A total of 447 transcripts were identified whose abundance changed more than 2-fold in the LE but which did not change in the underlying stroma (S) and glands. Six major patterns of changing expression were noted. Of the 447 genes, 140 were expressed in LE at least 15-fold higher than in S and glandular epithelium (GE) (101 of these more than 20-fold). Detailed spatiotemporal expression profiles were derived for several genes previously implicated in implantation (including Edg7, Ptgs1, Pla2g4a and Alox15).

CONCLUSIONS

Functional changes in LE receptivity are characterized by changing constellations of gene expression. Pre-receptivity has a different molecular footprint to refractoriness. Because we have used the pseudo-pregnant mouse model, these changes are driven solely by endocrine signals rather than events downstream of embryo attachment. Some of these genes have been described in previous microarray studies on endometrium, but for the majority, this is the first time they have been implicated in implantation. The 140 genes enriched in the LE greatly expand the list of epithelial markers and provide many novel candidates for further studies to identify genes playing important roles in receptivity and embryo attachment.

Paracrine mediators of mouse uterine epithelial cell transepithelial resistance in culture

Epithelial cell integrity at mucosal surfaces provides an effective physical barrier against potential pathogens that threaten reproductive health. We have used polarized epithelial cells from adult mouse uteri to investigate the roles of TNFalpha and TGFbeta, which are produced by uterine epithelial and stromal cells, and hepatocyte growth factor (HGF), produced by uterine stromal cells, in regulating epithelial cell integrity measured as transepithelial electrical resistance (TER). Exposure of epithelial cells to TNFalpha, TGFbeta, and HGF have profound effects on TER that are different from their known actions on TER at other mucosal surfaces. When incubated with TNFalpha, TER increased in a dose-dependent manner. In contrast, when cells were incubated with TGFbeta, TER was markedly but reversibly suppressed. Interestingly, HGF, when placed in the basolateral compartment, increased TER. Based on these findings, we conclude that TNFalpha, TGFbeta and HGF may play regulatory roles in modulating epithelial cell tight junctions. These studies suggest that factors, such as hormone balance, pathogen exposure as well as pregnancy, which affect cytokine and growth factor secretion, influence epithelial cell barrier protection within the female reproductive tract.

Polarized uterine epithelial cells preferentially present antigen at the basolateral surface: role of stromal cells in regulating class II-mediated epithelial cell antigen presentation

To study Ag presentation in the female reproductive tract, DO11.10 TCR transgenic mice specific for the class II MHC-restricted OVA(323-339) peptide and non-transgenic BALB/c mice were used. We report here that freshly isolated uterine epithelial cells, uterine stromal, and vaginal APCs present OVA and OVA(323-339) peptide to naive- and memory T cells, which is reduced when cells are incubated with Abs to CD80 and 86. To determine whether polarized primary epithelial cells present Ags, uterine epithelial cells were cultured on cell inserts in either the upright or inverted position. After reaching confluence, as indicated by high transepithelial resistance (>2000 ohms/well), Ag presentation by epithelial cells incubated with memory T cells and OVA(323-339) peptide placed on the basolateral surface (inverted) was 2- to 3-fold greater than that seen with epithelial cells in contact with T cells and peptide on the apical surface (upright). In contrast, whereas freshly isolated epithelial cells process OVA, polarized epithelial cells did not. When epithelial cells grown upright on inserts were incubated with T cells and OVA(323-339) peptide, coculture with either hepatocyte growth factor or conditioned stromal medium increased epithelial cell Ag presentation (approximately 90% higher than controls). These studies indicate that uterine stromal cells produce a soluble factor(s) in addition to a hepatocyte growth factor, which regulates epithelial cell Ag presentation. Overall, these results demonstrate that polarized epithelial cells are able to present Ags and suggest that uterine stromal cells communicate with epithelial cells via a soluble factor(s) to regulate Ag presentation in the uterus.

Innate and adaptive immunity in female genital tract: cellular responses and interactions

The mucosal immune system in the female reproductive tract (FRT) has evolved to meet the unique requirements of dealing with sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and the immunologically distinct fetus. Analysis of the FRT indicates that the key cells of the innate and adaptive immune systems are present and functionally responsive to antigens. Acting through Toll-like receptors in the Fallopian tubes, uterus, cervix, and in the vagina, epithelial cells, macrophages, natural killer cells, and neutrophils confer protection through the production of chemokines and cytokines, which recruit and activate immune cells, as well as bactericidal and virucidal agents, which confer protection at times when adaptive immunity is downregulated by sex hormones to meet the constraints of procreation. The overall goal of this paper is to define the innate immune system in the FRT and, where possible, to define the regulatory influences that occur during the menstrual cycle that contribute to protection from and susceptibility to potential pathogens. By understanding the nature of this protection and the ways in which innate and adaptive immunity interact, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

Effects of estradiol on lipopolysaccharide and Pam3Cys stimulation of CCL20/macrophage inflammatory protein 3 alpha and tumor necrosis factor alpha production by uterine epithelial cells in culture

We have previously demonstrated that rat uterine epithelial cells (UEC) produce CCL20/macrophage inflammatory protein 3 alpha (MIP3alpha) and tumor necrosis factor alpha (TNF-alpha) in response to live and heat-killed Escherichia coli and to the pathogen-associated molecular patterns (PAMP) lipopolysaccharide (LPS) and Pam3Cys. To determine whether estradiol (E2) modulates PAMP-induced CCL20/MIP3alpha and TNF-alpha secretion, primary cultures of rat UEC were incubated with E2 for 24 h and then treated with LPS or Pam3Cys or not treated for an additional 12 h. E2 inhibited the constitutive secretion of TNF-alpha and CCL20/MIP3alpha into culture media. Interestingly, E2 pretreatment enhanced CCL20/MIP3alpha secretion due to LPS and Pam3Cys administration. In contrast, and at the same time, E2 lowered the TNF-alpha response to both PAMP. To determine whether estrogen receptors (ER) mediated the effects of E2, epithelial cells were incubated with E2 and/or ICI 182,780, a known ER antagonist. ICI 182,780 had no effect on E2 inhibition of constitutive TNF-alpha and CCL20/MIP3alpha secretion. In contrast, ICI 182,780 reversed the stimulatory effect of E2 on LPS- and/or Pam3Cys-induced CCL20/MIP3alpha secretion as well as partially reversed the inhibitory effect of E2 on TNF-alpha production by epithelial cells. Overall, these results indicate that E2 regulates the production of TNF-alpha and CCL20/MIP3alpha by UEC in the absence as well as presence of PAMP. Since CCL20/MIP3alpha has antimicrobial activity and is chemotactic for immune cells, these studies suggest that regulation of CCL20/MIP3alpha and TNF-alpha by E2 and PAMP may have profound effects on innate and adaptive immune responses to microbial challenge in the female reproductive tract.

Epithelial cells in the female reproductive tract: a central role as sentinels of immune protection

The continued presence of bacterial and viral antigens in the lumen of the vagina coupled with the periodic presence of antigens in the lumen of the upper reproductive tract provide an ongoing challenge that can compromise female reproductive health and threaten life. Separating underlying tissues from luminal antigens, polarized epithelial cells of the cervix, uterus and Fallopian tubes have evolved to protect against potential pathogens. Once thought to function exclusively by providing a crucial barrier, mucosal epithelial cells are now known to function as sentinels that recognize antigens, respond in ways that lead to bacterial and viral killing, as well as signal to underlying immune cells when pathogenic challenge exceeds their protective capacity. Unique to epithelial cells of the female reproductive tract is the regulatory control of the female sex hormones. Acting both directly and indirectly through underlying stromal cells, estradiol and progesterone regulate epithelial cell innate and adaptive immune functions to protect against potential pathogens while providing an environment that supports an allogeneic fetus. In this article, we will outline how polarized epithelial cells function as the first line of defense against potential pathogens in the female reproductive tract.

Sex hormone regulation of anti-bacterial activity in rat uterine secretions and apical release of anti-bacterial factor(s) by uterine epithelial cells in culture

In mature female rats, sex hormones regulate the reproductive (estrous) cycle to optimize mating and fertility. During the part of the estrous cycle when mating occurs, and when estrogen is the dominant sex hormone, the uterus is susceptible to infection with bacteria that can be deleterious for survival and fertility. The present study investigated whether sex hormones regulate innate immunity in the female reproductive tract by affecting the secretion of an anti-bacterial factor(s) in the rat uterus. Uterine fluids from intact rats at the proestrous stage of the estrous cycle significantly inhibited Staphylococcus aureus growth. When ovariectomized rats were treated with estradiol, anti-bacterial activity against both S. aureus and Escherichia coli increased in uterine secretions with hormone treatment. In contrast, rats injected with either progesterone and estradiol or progesterone alone displayed no bactericidal activity indicating that progesterone reversed the stimulatory effect of estradiol on anti-bacterial activity. In other studies, isolated uterine epithelial cells from intact animals were grown to confluence and high transepithelial resistance on cell inserts. Analysis of apical secretions indicated that a soluble factor(s) is released by polarized epithelial cells which inhibits bacterial growth. These results demonstrate that sex hormones influence the presence of a broad-spectrum bactericidal factor(s) in luminal secretions of the rat uterus. Further these studies suggest that epithelial cells which line the uterine lumen are a primary source of anti-bacterial activity.