Human Three-Dimensional Endometrial Epithelial Cell Model To Study Host Interactions with Vaginal Bacteria and Neisseria gonorrhoeae

Impact of Lactobacillus in the uterine microbiota on in vitro fertilization outcomes

Abundant intrauterine Lactobacillus is associated with good in vitro fertilization (IVF) outcomes; however, whether specific species of Lactobacillus have any benefit remains unclear. So we examine the effect of Lactobacillus on the clinical outcomes of IVF at the species level. Uterine microbiota were classified as either Lactobacillus-dominant (LD) or non-Lactobacillus-dominant. In the LD group, we further investigated the clinical results for each Lactobacillus species and evaluated them in relation to IVF outcomes. In Uterine microbiome analysis, Lactobacillus was the most abundant, with the four species of L. crispatus, L. iners, L. gasseri, and L. jensenii accounting for the great majority. We compared the clinical outcomes of single frozen-thawed embryo transfer conducted by Lactobacillus species and found that the implantation rate was lowest in those in whom L. iners was dominant. This study is the first to conduct a species-level analysis of the uterine microbiota and report on a detailed investigation of Lactobacillus, which was believed to be particularly helpful for pregnancy.

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.

Biomanufacturing of 3D Tissue Constructs in Microgravity and their Applications in Human Pathophysiological Studies

The growing interest in bioengineering in-vivo-like 3D functional tissues has led to novel approaches to the biomanufacturing process as well as expanded applications for these unique tissue constructs. Microgravity, as seen in spaceflight, is a unique environment that may be beneficial to the tissue-engineering process but cannot be completely replicated on Earth. Additionally, the expense and practical challenges of conducting human and animal research in space make bioengineered microphysiological systems an attractive research model. In this review, published research that exploits real and simulated microgravity to improve the biomanufacturing of a wide range of tissue types as well as those studies that use microphysiological systems, such as organ/tissue chips and multicellular organoids, for modeling human diseases in space are summarized. This review discusses real and simulated microgravity platforms and applications in tissue-engineered microphysiological systems across three topics: 1) application of microgravity to improve the biomanufacturing of tissue constructs, 2) use of tissue constructs fabricated in microgravity as models for human diseases on Earth, and 3) investigating the effects of microgravity on human tissues using biofabricated in vitro models. These current achievements represent important progress in understanding the physiological effects of microgravity and exploiting their advantages for tissue biomanufacturing.

Endometrial Microbiota and Immune Tolerance in Pregnancy

Recent studies have demonstrated that the uterus has its own microbiota. However, there is no consensus on endometrial microbiota composition, thus its role in the healthy uterine environment is still a frontier topic. Endometrial receptivity is key to embryo implantation, and in this specific context immunological tolerance against fetal antigens and the tightly regulated expression of inflammatory mediators are fundamental. According to recent evidence, endometrial microbiota may interact in a very dynamic way with the immune system during the peri-conceptional stage and later during pregnancy. For this reason, a condition of dysbiosis might lead to adverse pregnancy outcomes. The aim of this review is to summarize the evidence on the molecular mechanisms by which the endometrial microbiota may interact with the immune system. For this purpose, the link between dysbiosis and reproductive disorders, such as infertility, recurrent pregnancy loss (RPL), and preterm birth, will be discussed. In conclusion, the most recent findings from molecular analyses will be reported to illustrate and possibly overcome the intrinsic limitations of uterine microbiota detection (low endometrial biomass, high risk of contamination during sampling, and lack of standardization).

Immunometabolic and potential tumor-promoting changes in 3D cervical cell models infected with bacterial vaginosis-associated bacteria

Specific bacteria of the human microbiome influence carcinogenesis at diverse anatomical sites. Bacterial vaginosis (BV) is the most common vaginal disorder in premenopausal women that is associated with gynecologic sequelae, including cervical cancer. BV-associated microorganisms, such as Fusobacterium, Lancefieldella, Peptoniphilus, and Porphyromonas have been associated with gynecologic and other cancers, though the pro-oncogenic mechanisms employed by these bacteria are poorly understood. Here, we integrated a multi-omics approach with our three-dimensional (3-D) cervical epithelial cell culture model to investigate how understudied BV-associated bacteria linked to gynecologic neoplasia influence hallmarks of cancer in vitro. Lancefieldella parvulum and Peptoniphilus lacrimalis elicited robust proinflammatory responses in 3-D cervical cells. Fusobacterium nucleatum and Fusobacterium gonidiaformans modulated metabolic hallmarks of cancer corresponding to accumulation of 2-hydroxyglutarate, pro-inflammatory lipids, and signs of oxidative stress and genotoxic hydrogen sulfide. This study provides mechanistic insights into how gynecologic cancer-associated bacteria might facilitate a tumor-promoting microenvironment in the human cervix.

Biologia Futura: endometrial microbiome affects endometrial receptivity from the perspective of the endometrial immune microenvironment

The existence of Lactobacillus-led colonized bacteria in the endometrium of a healthy human has been reported in recent studies. Unlike the composition of the microbiome in the lower genital tract, that in the endometrium is different and closely associated with the physiological and pathological processes of gynecological diseases. For example, changing the immune microenvironment affects the receptivity of the endometrium, thereby leading to abnormal reproductive outcomes, such as embryo implantation failure and recurrent spontaneous abortion. However, the concrete functions and mechanisms of the endometrial microbiome have not been studied thoroughly. This review elaborates the research progress on the mechanisms by which the endometrial microbiome affects endometrial receptivity from the perspective of endometrial immune microenvironment regulation. Considering the lack of a unified evaluation method for the endometrial microbiome, as well as the lack of an optimal treatment protocol against recurrent spontaneous abortion, we also discussed the application of combining antibiotics with probiotics/prebiotics as precautionary measures.

Three-dimensional models of the cervicovaginal epithelia to study host-microbiome interactions and sexually transmitted infections

2D cell culture systems have historically provided controlled, reproducible means to analyze host-pathogen interactions observed in the human reproductive tract. Although inexpensive, straightforward, and requiring a very short time commitment, these models recapitulate neither the functionality of multilayered cell types nor the associated microbiome that occurs in a human. Animal models have commonly been used to recreate the complexity of human infections. However, extensive modifications of animal models are required to recreate interactions that resemble those in the human reproductive tract. 3D cell culture models have emerged as alternative means of reproducing vital elements of human infections at a fraction of the cost of animal models and on a scale that allows for replicative experiments. Here, we describe a new 3D model that utilizes transwells with epithelial cells seeded apically and a basolateral extracellular matrix (ECM)-like layer. The model produced tissues with morphologic and physiological resemblance to human cervical and vaginal epithelia, including mucus levels produced by cervical cells. Infection by Chlamydia trachomatis and Neisseria gonorrhoeae was demonstrated, as well as the growth of bacterial species observed in the human vaginal microbiota. This enabled controlled mechanistic analyses of the interactions between host cells, the vaginal microbiota, and STI pathogens. Affordable and semi high-throughput 3D models of the cervicovaginal epithelia that are physiologically relevant by sustaining vaginal bacterial colonization, and facilitate studies of chlamydial and gonococcal infections.

Et tu, Neisseria? Conflicts of Interest Between Neisseria Species

Neisseria meningitidis and Neisseria gonorrhoeae are two obligate human pathogens that have evolved to be uniquely adapted to their host. The meningococcus is frequently carried asymptomatically in the nasopharynx, while gonococcal infection of the urogenital tract usually elicits a marked local inflammatory response. Other members of the Neisseria genus are abundant in the upper airway where they could engage in co-operative or competitive interactions with both these pathogens. Here, we briefly outline the potential sites of contact between Neisseria spp. in the body, with emphasis on the upper airway, and describe the growing yet circumstantial evidence for antagonism from carriage studies and human volunteer challenge models with Neisseria lactamica. Recent laboratory studies have characterized antagonistic mechanisms that enable competition between Neisseria species. Several of these mechanisms, including Multiple Adhesin family (Mafs), Two Partner Secretion Systems, and Type VI secretion system, involve direct contact between bacteria; the genetic organisation of these systems, and the domain structure of their effector molecules have striking similarities. Additionally, DNA from one species of Neisseria can be toxic to another species, following uptake. More research is needed to define the full repertoire of antagonistic mechanisms in Neisseria spp., their distribution in strains, their range of activity, and contribution to survival in vivo. Understanding the targets of effectors could reveal how antagonistic relationships between close relatives shape subsequent interactions between pathogens and their hosts.

Tissue Models for Neisseria gonorrhoeae Research—From 2D to 3D

Neisseria gonorrhoeae is a human-specific pathogen that causes gonorrhea, the second most common sexually transmitted infection worldwide. Disease progression, drug discovery, and basic host-pathogen interactions are studied using different approaches, which rely on models ranging from 2D cell culture to complex 3D tissues and animals. In this review, we discuss the models used in N. gonorrhoeae research. We address both in vivo (animal) and in vitro cell culture models, discussing the pros and cons of each and outlining the recent advancements in the field of three-dimensional tissue models. From simple 2D monoculture to complex advanced 3D tissue models, we provide an overview of the relevant methodology and its application. Finally, we discuss future directions in the exciting field of 3D tissue models and how they can be applied for studying the interaction of N. gonorrhoeae with host cells under conditions closely resembling those found at the native sites of infection.

The Microbiome as a Key Regulator of Female Genital Tract Barrier Function

The microbiome, the collection of microbial species at a site or compartment, has been an underappreciated realm of human health up until the last decade. Mounting evidence suggests the microbiome has a critical role in regulating the female genital tract (FGT) mucosa's function as a barrier against sexually transmitted infections (STIs) and pathogens. In this review, we provide the most recent experimental systems and studies for analyzing the interplay between the microbiome and host cells and soluble factors with an influence on barrier function. Key components, such as microbial diversity, soluble factors secreted by host and microbe, as well as host immune system, all contribute to both the physical and immunologic aspects of the FGT mucosal barrier. Current gaps in what is known about the effects of the microbiome on FGT mucosal barrier function are compared and contrasted with the literature of the gut and respiratory mucosa. This review article presents evidence supporting that the vaginal microbiome, directly and indirectly, contributes to how well the FGT protects against infection.

Bacterial vaginosis and health-associated bacteria modulate the immunometabolic landscape in 3D model of human cervix

Bacterial vaginosis (BV) is an enigmatic polymicrobial condition characterized by a depletion of health-associated Lactobacillus and an overgrowth of anaerobes. Importantly, BV is linked to adverse gynecologic and obstetric outcomes: an increased risk of sexually transmitted infections, preterm birth, and cancer. We hypothesized that members of the cervicovaginal microbiota distinctly contribute to immunometabolic changes in the human cervix, leading to these sequelae. Our 3D epithelial cell model that recapitulates the human cervical epithelium was infected with clinical isolates of cervicovaginal bacteria, alone or as a polymicrobial community. We used Lactobacillus crispatus as a representative health-associated commensal and four common BV-associated species: Gardnerella vaginalis, Prevotella bivia, Atopobium vaginae, and Sneathia amnii. The immunometabolic profiles of these microenvironments were analyzed using multiplex immunoassays and untargeted global metabolomics. A. vaginae and S. amnii exhibited the highest proinflammatory potential through induction of cytokines, iNOS, and oxidative stress-associated compounds. G. vaginalis, P. bivia, and S. amnii distinctly altered physicochemical barrier-related proteins and metabolites (mucins, sialic acid, polyamines), whereas L. crispatus produced an antimicrobial compound, phenyllactic acid. Alterations to the immunometabolic landscape correlate with symptoms and hallmarks of BV and connected BV with adverse women’s health outcomes. Overall, this study demonstrated that 3D cervical epithelial cell colonized with cervicovaginal microbiota faithfully reproduce the immunometabolic microenvironment previously observed in clinical studies and can successfully be used as a robust tool to evaluate host responses to commensal and pathogenic bacteria in the female reproductive tract.

Characterization of the endometrial, cervicovaginal and anorectal microbiota in post-menopausal women with endometrioid and serous endometrial cancers

OBJECTIVE

To characterize the microbiota of postmenopausal women undergoing hysterectomy for endometrioid (EAC) or uterine serous cancers (USC) compared to controls with non-malignant conditions.

METHODS

Endometrial, cervicovaginal and anorectal microbial swabs were obtained from 35 postmenopausal women (10 controls, 14 EAC and 11 USC) undergoing hysterectomy. Extracted DNA was PCR amplified using barcoded 16S rRNA gene V4 primers. Sequenced libraries were processed using QIIME2. Phyloseq was used to calculate α- and β- diversity measures. Biomarkers associated with case status were identified using ANCOM after adjustment for patient age, race and BMI. PICRUSt was used to identify microbial pathways associated with case status.

RESULTS

Beta-diversity of microbial communities across each niche was significantly different (R2 = 0.25, p < 0.001). Alpha-diversity of the uterine microbiome was reduced in USC (Chao1, p = 0.004 and Fisher, p = 0.007) compared to EAC. Biomarkers from the three anatomical sites allowed samples to be clustered into two distinct clades that distinguished controls from USC cases (p = 0.042). The USC group was defined by 13 bacterial taxa across the three sites (W-stat>10, FDR<0.05) including depletion of cervicovaginal Lactobacillus and elevation of uterine Pseudomonas. PICRUSTt analysis revealed highly significant differences between the USC-associated clades within the cervicovaginal and uterine microbiota.

CONCLUSIONS

The microbial diversity of anatomic niches in postmenopausal women with EAC and USC is different compared to controls. Multiple bacteria are associated with USC case status including elevated levels of cervicovaginal Lactobacillus, depletion of uterine Pseudomonas, and substantially different functional potentials identified within cervicovaginal and uterine niches.

Mucus-producing 3D cell culture models

In vitro cell-based models have been used for a long time since they are normally easily obtained and have an advantageous cost-benefit. Besides, they can serve a variety of ends, from studying drug absorption and metabolism to disease modeling. However, some in vitro models are too simplistic, not accurately representing the living tissues. It has been shown, mainly in the last years, that fully mimicking a tissue composition and architecture can be paramount for cellular behavior and, consequently, for the outcomes of the studies using such models. Because of this, 3D in vitro cell models have been gaining much attention, since they are able to better replicate the in vivo environment. In this review we focus on 3D models that contain mucus-producing cells, as mucus can play a pivotal role in drug absorption. Being frequently overlooked, this viscous fluid can have an impact on drug delivery. Thus, the aim of this review is to understand to which extent can mucus affect mucosal drug delivery and to provide a state-of-the-art report on the existing 3D cell-based mucus models.

The role of gut and genital microbiota and the estrobolome in endometriosis, infertility and chronic pelvic pain

BACKGROUND

Endometriosis is a chronic, burdensome condition that is historically understudied. Consequently, there is a lack of understanding of the etiology of the disease and its associated symptoms, including infertility and chronic pelvic pain (CPP). Endometriosis development is influenced by estrogen metabolism and inflammation, which are modulated by several factors including the microbiome and the estrobolome (the collection of genes encoding estrogen-metabolizing enzymes in the gut microbiome). Therefore, there is increasing interest in understanding the role of microbiota in endometriosis etiology.

OBJECTIVE AND RATIONALE

To date, there is no cure for endometriosis and treatment options often are ineffective. This manuscript will review the potential relationship between the microbiome and endometriosis, infertility and CPP and highlight the available data on the microbiome in relation to endometriosis and its related symptoms. The overarching goal of this manuscript is to inform future microbiome research that will lead to a deeper understanding of the etiology of the disease and possible diagnostic modalities and treatments. The potential impact of the microbiome on estrogen regulation modulated by the estrobolome, as well as inflammation and other endometriosis-promoting mechanisms within the genital tract, will be reviewed. The methodological limitations of microbiome-related studies will be critically assessed to provide improved guidelines for future microbiome and clinical studies.

SEARCH METHODS

PubMed databases were searched using the following keywords: endometriosis AND microbiome, infertility AND microbiome, pelvic pain AND microbiome, IVF (in-vitro fertilization) AND microbiome, endometriosis AND infertility. Clinical and preclinical animal trials that were eligible for review, and related to microbiome and endometriosis, infertility or CPP were included. All available manuscripts were published in 2002-2021.

OUTCOMES

In total, 28 clinical and 6 animal studies were included in the review. In both human and animal studies, bacteria were enriched in endometriosis groups, although there was no clear consensus on specific microbiota compositions that were associated with endometriosis, and no studies included infertility or CPP with endometriosis. However, bacterial vaginosis-associated bacteria and Lactobacillus depletion in the cervicovaginal microbiome were associated with endometriosis and infertility in the majority (23/28) of studies. Interpretation of endometrial studies is limited owing to a variety of methodological factors, discussed in this review. In addition, metadata outlining antibiotic usage, age, race/ethnicity, menopausal status and timing of sample collection in relation to diagnosis of endometriosis was not consistently reported. Animal studies (6/6) support a bidirectional relationship between the gut microbiota and endometriosis onset and progression.

WIDER IMPLICATIONS

There is evidence that a dysbiotic gut or genital microbiota is associated with multiple gynecologic conditions, with mounting data supporting an association between the microbiome and endometriosis and infertility. These microbiomes likely play a role in the gut-brain axis, which further supports a putative association with the spectrum of symptoms associated with endometriosis, including infertility and CPP. Collectively, this review highlights the demand for more rigorous and transparent methodology and controls, consistency across the field, and inclusion of key demographic and clinical characteristics of disease and comparison participants. Rigorous study designs will allow for a better understanding of the potential role of the microbiome in endometriosis etiology and the relationship to other disorders of the female reproductive tract.

Gardnerella vaginalis induces NLRP3 inflammasome-mediated pyroptosis in macrophages and THP-1 monocytes

The vagina is colonized by a variety of microbes that serve vital roles in the maintenance of vaginal health. The purpose of the present study was to explore the underlying mechanism by which Gardnerella vaginalis (GV) can induce bacterial vaginosis (BV). The viability of primary mouse macrophages and THP-1 cells was detected using a Cell Counting Kit-8 assay. Lactate dehydrogenase and caspase-1 activity in the culture medium of macrophages and THP-1 cells were measured using a colorimetric assay and a caspase-1 activity assay kit, respectively. In the macrophages and THP-1 cells, the levels of TNF-α, IL-1β and IL-18 were detected using ELISA whereas reactive oxygen species (ROS) levels were detected using flow cytometry. The pyroptosis of macrophages and THP-1 cells was detected using calcein-AM/PI double staining. Expression of proteins associated with the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain-containing protein 3 inflammasome (NLRP3), including NLRP3, apoptosis associated speck-like protein (ASC), caspase-1 and pro-caspase-1, were measured by western blotting and reverse transcription-quantitative PCR. GV significantly inhibited cell viability and increased LDH activity in macrophages and THP-1 cells. In addition, GV markedly promoted the production of TNF-α, IL-1β, IL-18 and ROS by macrophages and THP-1 cells. GV significantly promoted caspase-1 activation-mediated pyroptosis in macrophages and THP-1 cells. Treatment with GV significantly increased the protein and mRNA expression of NLRP3, ASC and caspase-1 in macrophages and THP-1 cells. To conclude, data from the present study suggest that G. vaginalis can induce BV by promoting NLRP3 inflammasome-mediated pyroptosis, which provides one of the molecular mechanisms by which G. vaginalis can induce BV.

Gonococcal Pelvic Inflammatory Disease: Placing Mechanistic Insights Into the Context of Clinical and Epidemiological Observations

While infection by Neisseria gonorrhoeae is often asymptomatic in women, undetected infections can ascend into the upper genital tract to elicit an inflammatory response that manifests as pelvic inflammatory disease, with the outcomes depending on the intensity and duration of inflammation and whether it is localized to the endometrial, fallopian tube, ovarian, and/or other tissues. This review examines the contribution of N. gonorrhoeae versus other potential causes of pelvic inflammatory disease by considering new insights gained through molecular, immunological, and microbiome-based analyses, and the current epidemiological burden of infection, with an aim to highlighting key areas for future study.

Bacterial Vaginosis: Effects on reproduction and its therapeutics

Bacterial Vaginosis (BV) is the most common vaginal infection. A large amount of evidence shows that the anatomical scope of BV's pathogenic effect is far beyond the lower reproductive tract. BV is closely related to adverse reproductive outcomes, which may be due to the infection of the vaginal flora ascending to the upper genital tract. In addition, the incidence of BV is relatively high in infertile women. The vaginal microbiome also plays an important role in women's health and diseases. For most women, the normal vaginal microbiota is dominated by Lactobacillus, which can maintain a healthy vaginal environment by producing lactic acid, H₂O₂ and bacteriocin, etc. BV is characterized by the imbalanced vaginal flora. It changes the acidic environment that is normally dominated by Lactobacillus, and causes an overgrowth of anaerobic and facultative anaerobic bacteria such as Gardnerella vaginalis and Atopobium vaginae. Studies have shown that bacterial infections in the vagina can spread to upper genital tract and cause adverse fertility outcome. Therefore, early diagnosis and therapeutics of symptomatic BV is helpful to improve the outcome of poor fertility.

Investigation of infertility using endometrial organoids

Infertility is a common problem in modern societies with significant socio-psychological implications for women. Therapeutic interventions are often needed which, depending on the cause, can either be medical treatment, surgical procedures or assisted reproductive technology (ART). However, the treatment of infertility is not always successful due to our limited understanding of the preparation of the lining of the uterus, the endometrium, for pregnancy. The endometrium is of central importance for successful reproduction as it is the site of placental implantation providing the interface between the mother and her baby. Due to the dynamic, structural and functional changes the endometrium undergoes throughout the menstrual cycle, it is challenging to study. A major advancement is the establishment of 3D organoid models of the human endometrium to study this dynamic tissue in health and disease. In this review, we describe the changes that the human endometrium undergoes through the different phases of the menstrual cycle in preparation for pregnancy. We discuss defects in the processes of endometrial repair, decidualization and acquisition of receptivity that are associated with infertility. Organoids could be utilized to investigate the underlying cellular and molecular mechanisms occurring in non-pregnant endometrium and early pregnancy. These studies may lead to therapeutic applications that could transform the treatment of reproductive failure.

Highly glycosylated MUC1 mediates high affinity L-selectin binding at the human endometrial surface

Background

Sialyl-Lewis X/L-selectin high affinity binding interactions between transmembrane O-glycosylated mucins proteins and the embryo have been implicated in implantation processes within the human reproductive system. However, the adhesive properties of these mucins at the endometrial cell surface are difficult to resolve due to known discrepancies between in vivo models and the human reproductive system and a lack of sensitivity in current in vitro models. To overcome these limitations, an in vitro model of the human endometrial epithelial was interrogated with single molecule force spectroscopy (SMFS) to delineate the molecular configurations of mucin proteins that mediate the high affinity L-selectin binding required for human embryo implantation.

Results

This study reveals that MUC1 contributes to both the intrinsic and extrinsic adhesive properties of the HEC-1 cellular surface. High expression of MUC1 on the cell surface led to a significantly increased intrinsic adhesion force (148 pN vs. 271 pN, p < 0.001), whereas this adhesion force was significantly reduced (271 pN vs. 118 pN, p < 0.001) following siRNA mediated MUC1 ablation. Whilst high expression of MUC1 displaying elevated glycosylation led to strong extrinsic (> 400 pN) L-selectin binding at the cell surface, low expression of MUC1 with reduced glycosylation resulted in significantly less (≤200 pN) binding events.

Conclusions

An optimal level of MUC1 together with highly glycosylated decoration of the protein is critical for high affinity L-selectin binding. This study demonstrates that MUC1 contributes to cellular adhesive properties which may function to facilitate trophoblast binding to the endometrial cell surface through the L-selectin/sialyl-Lewis x adhesion system subsequent to implantation.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part II: Systems and Applications

In this second part of our systematic review on the research area of 3D cell culture in micro-bioreactors we give a detailed description of the published work with regard to the existing micro-bioreactor types and their applications, and highlight important results gathered with the respective systems. As an interesting detail, we found that micro-bioreactors have already been used in SARS-CoV research prior to the SARS-CoV2 pandemic. As our literature research revealed a variety of 3D cell culture configurations in the examined bioreactor systems, we defined in review part one “complexity levels” by means of the corresponding 3D cell culture techniques applied in the systems. The definition of the complexity is thereby based on the knowledge that the spatial distribution of cell-extracellular matrix interactions and the spatial distribution of homologous and heterologous cell–cell contacts play an important role in modulating cell functions. Because at least one of these parameters can be assigned to the 3D cell culture techniques discussed in the present review, we structured the studies according to the complexity levels applied in the MBR systems.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part I: A Systematic Analysis of the Literature Published between 2000 and 2020

Bioreactors have proven useful for a vast amount of applications. Besides classical large-scale bioreactors and fermenters for prokaryotic and eukaryotic organisms, micro-bioreactors, as specialized bioreactor systems, have become an invaluable tool for mammalian 3D cell cultures. In this systematic review we analyze the literature in the field of eukaryotic 3D cell culture in micro-bioreactors within the last 20 years. For this, we define complexity levels with regard to the cellular 3D microenvironment concerning cell–matrix-contact, cell–cell-contact and the number of different cell types present at the same time. Moreover, we examine the data with regard to the micro-bioreactor design including mode of cell stimulation/nutrient supply and materials used for the micro-bioreactors, the corresponding 3D cell culture techniques and the related cellular microenvironment, the cell types and in vitro models used. As a data source we used the National Library of Medicine and analyzed the studies published from 2000 to 2020.

3D Oral and Cervical Tissue Models for Studying Papillomavirus Host-Pathogen Interactions

Human papillomavirus (HPV) infection occurs in differentiating epithelial tissues. Cancers caused by high-risk types (e.g., HPV16 and HPV18) typically occur at oropharyngeal and anogenital anatomical sites. The HPV life cycle is differentiation-dependent, requiring tissue culture methodology that is able to recapitulate the three-dimensional (3D) stratified epithelium. Here we report two distinct and complementary methods for growing differentiating epithelial tissues that mimic many critical morphological and biochemical aspects of in vivo tissue. The first approach involves growing primary human epithelial cells on top of a dermal equivalent consisting of collagen fibers and living fibroblast cells. When these cells are grown at the liquid-air interface, differentiation occurs and allows for epithelial stratification. The second approach uses a rotating wall vessel bioreactor. The low-fluid-shear microgravity environment inside the bioreactor allows the cells to use collagen-coated microbeads as a growth scaffold and self-assemble into 3D cellular aggregates. These approaches are applied to epithelial cells derived from HPV-positive and HPV-negative oral and cervical tissues. The second part of the article introduces potential downstream applications for these 3D tissue models. We describe methods that will allow readers to start successfully culturing 3D tissues from oral and cervical cells. These tissues have been used for microscopic visualization, scanning electron microscopy, and large omics-based studies to gain insights into epithelial biology, the HPV life cycle, and host-pathogen interactions. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Establishing human primary cell-derived 3D organotypic raft cultures Support Protocol 1: Isolation of epithelial cells from patient-derived tissues Support Protocol 2: Growth and maintenance of primary human epithelial cells in monolayer culture Support Protocol 3: PCR-based HPV screening of primary cell cultures Basic Protocol 2: Establishing human 3D cervical tissues using the rotating wall vessel bioreactor Support Protocol 4: Growth and maintenance of human A2EN cells in monolayer culture Support Protocol 5: Preparation of the slow-turning lateral vessel bioreactor Support Protocol 6: Preparation of Cytodex-3 microcarrier beads Basic Protocol 3: Histological assessment of 3D organotypic raft tissues Basic Protocol 4: Spatial analysis of protein expression in 3D organotypic raft cultures Basic Protocol 5: Immunofluorescence imaging of RWV-derived 3D tissues Basic Protocol 6: Ultrastructural visualization and imaging of RWV-derived 3D tissues Basic Protocol 7: Characterization of gene expression by RT-qPCR.

Members of Prevotella Genus Distinctively Modulate Innate Immune and Barrier Functions in a Human Three-Dimensional Endometrial Epithelial Cell Model

BACKGROUND

Prevotella species are commonly isolated from the reproductive tract of women with obstetric/gynecologic health complications. However, contributions of this genus to changes in local microenvironment are not well characterized. Our objective was to evaluate species-specific effects of Prevotella on the human endometrial epithelium.

METHODS

Thirteen Prevotella strains, originally isolated from the human oral cavity, amniotic fluid, endometrium, or vagina (including women with bacterial vaginosis), were obtained from BEI and ATCC resources. Bacteria were evaluated in silico and in vitro using human endometrial epithelial cells (EEC) grown as monolayers or a 3-dimensional (3D) model.

RESULTS

Genomic characterization illustrated metabolic and phylogenetic diversity of Prevotella genus. Among tested species, P. disiens exhibited cytotoxicity. Scanning electron microscopy analysis of the 3D EEC model revealed species-specific colonization patterns and alterations of ultracellular structures. Infection with sialidase-producing P. timonensis resulted in elongated microvilli, and increased MUC3 and MUC4 expression. Infections with Prevotella species, including P. bivia, did not result in significant proinflammatory activation of EEC.

CONCLUSIONS

Collectively, findings indicate that Prevotella species are metabolically diverse and overall not cytotoxic or overtly inflammatory in EEC; however, these bacteria can form biofilms, alter barrier properties of the endometrial epithelium, and ultimately impact colonization of secondary colonizers.

In vitro models of the human endometrium: evolution and application for women's health

The endometrium is the inner lining of the uterus that undergoes complex regeneration and differentiation during the human menstrual cycle. The process of endometrial shedding, regeneration, and differentiation is driven by ovarian steroid hormones and prepares the endometrium and intrauterine environment for embryo implantation and pregnancy establishment. Endometrial glands and their secretions are essential for pregnancy establishment, and cross talk between the glandular epithelium and stromal cells appears vital for decidualization and placental development. Despite being crucial, the biology of the human endometrium during pregnancy establishment and most of pregnancy is incomplete, given the ethical and practical limitations of obtaining and studying endometrium from pregnant women. As such, in vitro models of the human endometrium are required to fill significant gaps in understanding endometrial biology. This review is focused on the evolution and development of in vitro three-dimensional models of the human endometrium and provides insight into the challenges and promises of those models to improve women's reproductive health.

Inhibition of TLR2/TLR4 alleviates the Neisseria gonorrhoeae infection damage in human endometrial epithelial cells via Nrf2 and NF-Kβsignaling

BACKGROUND

Neisseria gonorrhoeae (N.g) is Gram-negative bacteria and can lead to endometritis in female. Toll-like receptors regulate immune response in various diseases. However, the roles of TLR2 and TLR4 in. Neisseria gonorrhoeae-induced infection damage in human endometrial epithelia were investigated.

METHODS

hEECs were infected with N.g (MOI 10 and 100) and cell viability and apoptosis were measured by CCK8 and flow cytometry assays in both infected groups with the uninfected normal hEECs as negative control. TLR2/TLR4 proteins were measured by ELISA method. Pro-inflammatory markers NLRP3, PGES (PGE2) and TNF-α were assessed by RT-qPCR (mRNA expression) and Elisa (protein concentrations). Transfection assays were performed to up- or down- regulate expression of TLR2 and TLR4 so as to study the functions of TLR2/TLR4 in. N.g-infected hEECs, followed by apoptosis and inflammation assessment. Similarly, we explored the interactions between TLR2/TLR4 and Nrf2/NF-κB/p65 by knocking down TLR2/TLR4 to detect the signaling and further regulating the signaling to evaluate TLR2/ TLR4, apoptosis and inflammation in cells.

RESULTS

N.g suppressed cell viabilities and induced cell apoptosis and inflammation. TLR2/TLR4 downregulation inhibited the infection damage. Nrf2 was activated while NF-κB/p65 was depleted as TLR2/ TLR4 was knocked down. Activation of Nrf2 and inhibition of NF-κB resulted in decrease of TLR2/TLR4, which could retard apoptosis and inflammation induced by N.g infection.

CONCLUSION

TLR2/TLR4 depletion could alleviate the N.g-infected hEECs via Nrf2/NF-kB signaling, suggesting that TLR2/TLR4 inhibitors might serve as a treatment to reduce N.g infection in human endometrial epithelia.

Folliculin Controls the Intracellular Survival and Trans-Epithelial Passage of Neisseria gonorrhoeae

Neisseria gonorrhoeae, a Gram-negative obligate human pathogenic bacterium, infects human epithelial cells and causes sexually transmitted diseases. Emerging multi-antibiotic resistant gonococci and increasing numbers of infections complicate the treatment of infected patients. Here, we used an shRNA library screen and next-generation sequencing to identify factors involved in epithelial cell infection. Folliculin (FLCN), a 64 kDa protein with a tumor repressor function was identified as a novel host factor important for N. gonorrhoeae survival after uptake. We further determined that FLCN did not affect N. gonorrhoeae adherence and invasion but was essential for its survival in the cells by modulating autophagy. In addition, FLCN was also required to maintain cell to cell contacts in the epithelial layer. In an infection model with polarized cells, FLCN inhibited the polarized localization of E-cadherin and the transcytosis of gonococci across polarized epithelial cells. In conclusion, we demonstrate here the connection between FLCN and bacterial infection and in particular the role of FLCN in the intracellular survival and transcytosis of gonococci across polarized epithelial cell layers.

Uterine microbiome-low biomass and high expectations†

The existence of different bacterial communities throughout the female reproductive tract has challenged the traditional view of human fetal development as a sterile event. There is still no consensus on what physiological microbiota exists in the upper reproductive tract of the vast majority of women who are not in periods of infection or pregnancy, and the role of bacteria that colonize the upper reproductive tract in uterine diseases or pregnancy outcomes is not well established. Despite published studies and advances in uterine microbiome sequencing, some study aspects-such as study design, sampling method, DNA extraction, sequencing methods, downstream analysis, and assignment of taxa-have not yet been improved and standardized. It is time to further investigate the uterine microbiome to increase our understanding of the female reproductive tract and to develop more personalized reproductive therapies, highlighting the potential importance of using microbiological assessment in infertile patients.

Organoid models in gynaecological oncology research

Cell culture and animal models represent experimental cornerstones for the investigation of tissue, organ and body physiology in the context of gynaecological research. However, their ability to accurately reflect human mechanisms in vivo is limited. The development of organoid technologies has begun to address this limitation by providing platforms ex vivo that resemble the phenotype and genotype of the multi-cellular tissue from which they were derived more accurately. In this review, we discuss advances in organoid derivation from endometrial, ovarian, fallopian tube and cervical tissue, both benign and malignant, the manipulation of organoid microenvironment to preserve stem cell populations and achieve long-term expansion and we explore the morphological and molecular kinship of organoids to parent tissue. Apart from providing new insight into mechanisms of carcinogenesis, gynaecological cancer-derived organoids can be utilised as tools for drug screening of chemotherapeutic and hormonal compounds where they exhibit interpatient variability consistent with states in vivo and xenografted tumours allowing for patient-tailored treatment strategies. Bridging organoid with bioengineering accomplishments is clearly the way forward to the generation of organoid-on-a-chip technologies enhancing the robustness of the model and its translational potential. Undeniably, organoids are expected to stand their ground in the years to come and revolutionize development and disease modelling studies.

Pharmacokinetic/pharmacodynamic considerations for new and current therapeutic drugs for uncomplicated gonorrhoea-challenges and opportunities

BACKGROUND

Increasing multidrug resistance rates in Neisseria gonorrhoeae have raised concerns and an urgent call for new antibiotics for treatment of gonorrhoea. Several decades of subdued drug development in this field and the recent failures of two new antibiotics to show non-inferiority compared with the current first-line antibiotics ceftriaxone plus azithromycin highlight the need for improved preclinical tools to predict clinical outcome of new drugs in the development process.

OBJECTIVES

To summarize current pharmacokinetic/pharmacodynamic (PK/PD) knowledge and dose-finding strategies for antibiotics against gonorrhoea.

SOURCES

Literature review of published papers and discussions by global experts at a special workshop on this topic.

CONTENT

We review current knowledge of gonococcal specific PK/PD principles and provide an update on new in vitro and in vivo models to correlate drug exposure with clinical outcome, and identify challenges and gaps in gonococcal therapeutic research.

IMPLICATIONS

Identifying the ideal antimicrobial agent and dose for treating uncomplicated urogenital and pharyngeal gonococcal disease requires appropriate validated non-clinical PK/PD models. Recent advances in adapting in vitro and in vivo models for use in gonorrhoea are an important step for enabling the development of new drugs with reduced risk of failure in Phase 3 clinical development and diminish the risk of emergence of resistance.

Organoid technology in female reproductive biomedicine

Recent developments in organoid technology are revolutionizing our knowledge about the biology, physiology, and function of various organs. Female reproductive biology and medicine also benefit from this technology. Organoids recapitulate features of different reproductive organs including the uterus, fallopian tubes, and ovaries, as well as trophoblasts. The genetic stability of organoids and long-lasting commitment to their tissue of origin during long-term culture makes them attractive substitutes for animal and in vitro models. Despite current limitations, organoids offer a promising platform to address fundamental questions regarding the reproductive system's physiology and pathology. They provide a human source to harness stem cells for regenerative medicine, heal damaged epithelia in specific diseases, and study biological processes in healthy and pathological conditions. The combination of male and female reproductive organoids with other technologies, such as microfluidics technology, would enable scientists to create a multi-organoid-on-a-chip platform for the next step to human-on-a-chip platforms for clinical applications, drug discovery, and toxicology studies. The present review discusses recent advances in producing organoid models of reproductive organs and highlights their applications, as well as technical challenges and future directions.

Organoid systems to study the human female reproductive tract and pregnancy

Both the proper functioning of the female reproductive tract (FRT) and normal placental development are essential for women’s health, wellbeing, and pregnancy outcome. The study of the FRT in humans has been challenging due to limitations in the in vitro and in vivo tools available. Recent developments in 3D organoid technology that model the different regions of the FRT include organoids of the ovaries, fallopian tubes, endometrium and cervix, as well as placental trophoblast. These models are opening up new avenues to investigate the normal biology and pathology of the FRT. In this review, we discuss the advances, potential, and limitations of organoid cultures of the human FRT.

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The microbiome and gynaecological cancer development, prevention and therapy

The female reproductive tract (FRT), similar to other mucosal sites, harbours a site-specific microbiome, which has an essential role in maintaining health and homeostasis. In the majority of women of reproductive age, the microbiota of the lower FRT (vagina and cervix) microenvironment is dominated by Lactobacillus species, which benefit the host through symbiotic relationships. By contrast, the upper FRT (uterus, Fallopian tubes and ovaries) might be sterile in healthy individuals or contain a low-biomass microbiome with a diverse mixture of microorganisms. When dysbiosis occurs, altered immune and metabolic signalling can affect hallmarks of cancer, including chronic inflammation, epithelial barrier breach, changes in cellular proliferation and apoptosis, genome instability, angiogenesis and metabolic dysregulation. These pathophysiological changes might lead to gynaecological cancer. Emerging evidence shows that genital dysbiosis and/or specific bacteria might have an active role in the development and/or progression and metastasis of gynaecological malignancies, such as cervical, endometrial and ovarian cancers, through direct and indirect mechanisms, including modulation of oestrogen metabolism. Cancer therapies might also alter microbiota at sites throughout the body. Reciprocally, microbiota composition can influence the efficacy and toxic effects of cancer therapies, as well as quality of life following cancer treatment. Modulation of the microbiome via probiotics or microbiota transplant might prove useful in improving responsiveness to cancer treatment and quality of life. Elucidating these complex host-microbiome interactions, including the crosstalk between distal and local sites, will translate into interventions for prevention, therapeutic efficacy and toxic effects to enhance health outcomes for women with gynaecological cancers.

Prospects of NSAIDs administration as double-edged agents against endometrial cancer and pathological species of the uterine microbiome

Many types of cancers, including endometrial cancer, were found to have cyclooxygenase-2 (COX-2) overexpression. Because this enzyme belongs to the group of pro-inflammatory enzymes, so-called NSAIDs (non-steroidal anti–inflammatory drugs) directly inhibit its activity. An increasing number of reports on COX-2 involvement in cancer, as well as on the role of microbiota in abnormal metabolism and signaling of cells, forces the development of new NSAID types. Besides, NSAIDs can affect some bacteria, which are vaginal/endometrial microbiome members. The overgrowth of those species was found to be a major cause of some uterus diseases. Those infections can lead to chronic inflammatory response and suppress anti-tumorigenic cell pathways. The purpose of this review is to highlight the COX-2 enzyme role in endometrial cancer, the potential effect of the endometrial microbiome on COX-2 enzyme overexpression, and the prospects of NSAIDs use in terms of this type of cancer.

Analysis of Host Responses to Neisseria gonorrhoeae Using a Human Three-Dimensional Endometrial Epithelial Cell Model

Neisseria gonorrhoeae infections have been associated with complications including chronic endometritis and pelvic inflammatory disease. Robust in vitro models of the female reproductive tract are urgently needed to better understand the biological mechanisms leading to these pathophysiological changes. Our human three-dimensional (3D) endometrial epithelial cell (EEC) model, which is generated using the HEC-1A cell line and rotating wall vessel (RWV) bioreactor technology, replicates several hallmarks of endometrial tissue in vivo. Studying the interactions of N. gonorrhoeae with the host using this newly characterized human 3D EEC model allows for the investigation of unique mechanisms of gonococcal pathogenesis in the upper female reproductive tract. In this chapter, we describe methodologies that can be used to investigate the interactions of N. gonorrhoeae with the human 3D endometrial epithelium. Protocols for generating the human 3D EEC model using the RWV technology and assessing the host response (including morphological/ultrastructural changes to the epithelial cells; cytokine/chemokine secretion or gene expression changes) following infection with N. gonorrhoeae are presented.

Uterine Immunity and Microbiota: A Shifting Paradigm

The female reproductive tract harbors distinct microbial communities, as in the vagina, cervical canal, uterus, and fallopian tubes. The nature of the vaginal microbiota is well-known; in contrast, the upper reproductive tract remains largely unexplored. Alteration in the uterine microbiota, which is dependent on the nutrients and hormones available to the uterus, is likely to play an important role in uterine-related diseases such as hysteromyoma, adenomyosis, and endometriosis. Uterine mucosa is an important tissue barrier whose main function is to offer protection against pathogens and other toxic factors, while maintaining a symbiotic relationship with commensal microbes. These characteristics are shared by all the mucosal tissues; however, the uterine mucosa is unique since it changes cyclically during the menstrual cycle as well as pregnancy. The immune system, besides its role in the defense process, plays crucial roles in reproduction as it ensures local immune tolerance to fetal/paternal antigens, trophoblast invasion, and vascular remodeling. The human endometrium contains a conspicuous number of immune cells, mainly Natural Killers (NK) cells, which are phenotypically distinct from peripheral cytotoxic NK, cells and macrophages. The endometrium also contains few lymphoid aggregates comprising B cell and CD8⁺ T cells. The number and the phenotype of these cells change during the menstrual cycle. It has become evident in recent years that the immune cell phenotype and function can be influenced by microbiota. Immune cells can sense the presence of microbes through their pattern recognition receptors, setting up host-microbe interaction. The microbiota exerts an appropriately controlled defense mechanism by competing for nutrients and mucosal space with pathogens. It has recently been considered that uterus is a non-sterile compartment since it seems to possess its own microbiota. There has been an increasing interest in characterizing the nature of microbial colonization within the uterus and its apparent impact on fertility and pregnancy. This review will examine the potential relationship between the uterine microbiota and the immune cells present in the local environment.

Biomimetic Human Tissue Model for Long-Term Study of Neisseria gonorrhoeae Infection

Gonorrhea is the second most common sexually transmitted infection in the world and is caused by Gram-negative diplococcus Neisseria gonorrhoeae. Since N. gonorrhoeae is a human-specific pathogen, animal infection models are only of limited use. Therefore, a suitable in vitro cell culture model for studying the complete infection including adhesion, transmigration and transport to deeper tissue layers is required. In the present study, we generated three independent 3D tissue models based on porcine small intestinal submucosa (SIS) scaffold by co-culturing human dermal fibroblasts with human colorectal carcinoma, endometrial epithelial, and male uroepithelial cells. Functional analyses such as transepithelial electrical resistance (TEER) and FITC-dextran assay indicated the high barrier integrity of the created monolayer. The histological, immunohistochemical, and ultra-structural analyses showed that the 3D SIS scaffold-based models closely mimic the main characteristics of the site of gonococcal infection in human host including the epithelial monolayer, the underlying connective tissue, mucus production, tight junction, and microvilli formation. We infected the established 3D tissue models with different N. gonorrhoeae strains and derivatives presenting various phenotypes regarding adhesion and invasion. The results indicated that the disruption of tight junctions and increase in interleukin production in response to the infection is strain and cell type-dependent. In addition, the models supported bacterial survival and proved to be better suitable for studying infection over the course of several days in comparison to commonly used Transwell® models. This was primarily due to increased resilience of the SIS scaffold models to infection in terms of changes in permeability, cell destruction and bacterial transmigration. In summary, the SIS scaffold-based 3D tissue models of human mucosal tissues represent promising tools for investigating N. gonorrhoeae infections under close-to-natural conditions.

Bacterial Colonization of the Female Upper Genital Tract

Bacteria colonize most of the human body, and the female genital tract is not an exception. While the existence of a vaginal microbiota has been well established, the upper genital tract has been considered a sterile environment, with a general assumption that bacterial presence is associated with adverse clinical manifestation. However, recent metagenomic studies identified specific patterns of microbiota colonizing the uterus, fallopian tubes, ovaries, and placenta. These results need confirmation and further investigations since the data are only scarce. Bacterial colonization of these sites appears different from the vaginal one, despite evidence that vaginal bacteria could ascend to the upper genital tract through the cervix. Are these bacteria only commensal or do they play a role in the physiology of the female upper genital tract? Which are the genera that may have a negative and a positive impact on the female reproductive function? The aim of this review is to critically present all available data on upper genital tract microbiota and discuss its role in human reproduction, ranging from the technical aspects of these types of analyses to the description of specific bacterial genera. Although still very limited, research focusing on genital colonization of bacteria other than the vaginal milieu might bring novel insights into physiopathology of human reproduction.

Relating Advanced Electrospun Fiber Architectures to the Temporal Release of Active Agents to Meet the Needs of Next-Generation Intravaginal Delivery Applications

Electrospun fibers have emerged as a relatively new delivery platform to improve active agent retention and delivery for intravaginal applications. While uniaxial fibers have been explored in a variety of applications including intravaginal delivery, the consideration of more advanced fiber architectures may offer new options to improve delivery to the female reproductive tract. In this review, we summarize the advancements of electrospun coaxial, multilayered, and nanoparticle-fiber architectures utilized in other applications and discuss how different material combinations within these architectures provide varied durations of release, here categorized as either transient (within 24 h), short-term (24 h to one week), or sustained (beyond one week). We seek to systematically relate material type and fiber architecture to active agent release kinetics. Last, we explore how lessons derived from these architectures may be applied to address the needs of future intravaginal delivery platforms for a given prophylactic or therapeutic application. The overall goal of this review is to provide a summary of different fiber architectures that have been useful for active agent delivery and to provide guidelines for the development of new formulations that exhibit release kinetics relevant to the time frames and the diversity of active agents needed in next-generation multipurpose applications.

Interaction of Gardnerella vaginalis and Vaginolysin with the Apical versus Basolateral Face of a Three-Dimensional Model of Vaginal Epithelium

Studies have implicated Gardnerella vaginalis as an important etiological agent in bacterial vaginosis (BV). It produces a cholesterol-dependent cytolysin, vaginolysin (VLY). In this study, we sought to characterize the interaction between vaginal epithelium, G. vaginalis, and VLY using EpiVaginal tissues from MatTek. These tissues are three-dimensional and have distinct apical and basolateral sides, enabling comparison of the effects of G. vaginalis and VLY following exposure to either side. We measured cytotoxicity, cytokine production, and bacterial growth, following apical versus basolateral exposure. G. vaginalis exhibited more-rapid growth in coculture with the tissue model when it was exposed to the apical side. VLY permeabilized cells on the basolateral side of the tissues but failed to permeabilize apical epithelial cells. Cytokine secretion in response to VLY and G. vaginalis also depended on the polarity of exposure. VLY did not cause significant changes in cytokine levels when exposed apically. Apical tissue challenge by G. vaginalis appeared to dampen the inflammatory response, as decreases in granulocyte-macrophage colony-stimulating factor (GM-CSF) (6.6-fold), RANTES (14.8-fold), and interferon gamma inducible protein 10 kDa (IP-10) (53-fold) and an increase in interleukin-1 receptor antagonist (IL-1ra) (5-fold) were observed. In vivo, G. vaginalis normally colonizes the apical face of the vaginal epithelium. Results from this study suggest that while G. vaginalis may grow on the apical face of the vaginal epithelium, its VLY toxin does not target these cells in this model. This phenomenon could have important implications regarding colonization of the vagina by G. vaginalis and may suggest an explanation for the lack of an overt immune response to this organism.

How uterine microbiota might be responsible for a receptive, fertile endometrium

BACKGROUND

Fertility depends on a receptive state of the endometrium, influenced by hormonal and anatomical adaptations, as well as the immune system. Local and systemic immunity is greatly influenced by microbiota. Recent discoveries of 16S rRNA in the endometrium and the ability to detect low-biomass microbiota fueled the notion that the uterus may be indeed a non-sterile compartment. To date, the concept of the 'sterile womb' focuses on in utero effects of microbiota on offspring and neonatal immunity. However, little awareness has been raised regarding the importance of uterine microbiota for endometrial physiology in reproductive health; manifested in fertility and placentation.

OBJECTIVE AND RATIONALE

Commensal colonization of the uterus has been widely discussed in the literature. The objective of this review is to outline the possible importance of this uterine colonization for a healthy, fertile uterus. We present the available evidence regarding uterine microbiota, focusing on recent findings based on 16S rRNA, and depict the possible importance of uterine colonization for a receptive endometrium. We highlight a possible role of uterine microbiota for host immunity and tissue adaptation, as well as conferring protection against pathogens. Based on knowledge of the interaction of the mucosal immune cells of the gut with the local microbiome, we want to investigate the potential implications of commensal colonization for uterine health.

SEARCH METHODS

PubMed and Google Scholar were searched for articles in English indexed from 1 January 2008 to 1 March 2018 for '16S rRNA', 'uterus' and related search terms to assess available evidence on uterine microbiome analysis. A manual search of the references within the resulting articles was performed. To investigate possible functional contributions of uterine microbiota to health, studies on microbiota of other body sites were additionally assessed.

OUTCOMES

Challenging the view of a sterile uterus is in its infancy and, to date, no conclusions on a 'core uterine microbiome' can be drawn. Nevertheless, evidence for certain microbiota and/or associated compounds in the uterus accumulates. The presence of microbiota or their constituent molecules, such as polysaccharide A of the Bacteroides fragilis capsule, go together with healthy physiological function. Lessons learned from the gut microbiome suggest that the microbiota of the uterus may potentially modulate immune cell subsets needed for implantation and have implications for tissue morphology. Microbiota can also be crucial in protection against uterine infections by defending their niche and competing with pathogens. Our review highlights the need for well-designed studies on a 'baseline' microbial state of the uterus representing the optimal starting point for implantation and subsequent placenta formation.

WIDER IMPLICATIONS

The complex interplay of processes and cells involved in healthy pregnancy is still poorly understood. The correct receptive endometrial state, including the local immune environment, is crucial not only for fertility but also placenta formation since initiation of placentation highly depends on interaction with immune cells. Implantation failure, recurrent pregnancy loss, and other pathologies of endometrium and placenta, such as pre-eclampsia, represent an increasing societal burden. More robust studies are needed to investigate uterine colonization. Based on current data, future research needs to include the uterine microbiome as a relevant factor in order to understand the players needed for healthy pregnancy.

Modeling Host-Pathogen Interactions in the Context of the Microenvironment: Three-Dimensional Cell Culture Comes of Age

Tissues and organs provide the structural and biochemical landscapes upon which microbial pathogens and commensals function to regulate health and disease. While flat two-dimensional (2-D) monolayers composed of a single cell type have provided important insight into understanding host-pathogen interactions and infectious disease mechanisms, these reductionist models lack many essential features present in the native host microenvironment that are known to regulate infection, including three-dimensional (3-D) architecture, multicellular complexity, commensal microbiota, gas exchange and nutrient gradients, and physiologically relevant biomechanical forces (e.g., fluid shear, stretch, compression). A major challenge in tissue engineering for infectious disease research is recreating this dynamic 3-D microenvironment (biological, chemical, and physical/mechanical) to more accurately model the initiation and progression of host-pathogen interactions in the laboratory. Here we review selected 3-D models of human intestinal mucosa, which represent a major portal of entry for infectious pathogens and an important niche for commensal microbiota. We highlight seminal studies that have used these models to interrogate host-pathogen interactions and infectious disease mechanisms, and we present this literature in the appropriate historical context. Models discussed include 3-D organotypic cultures engineered in the rotating wall vessel (RWV) bioreactor, extracellular matrix (ECM)-embedded/organoid models, and organ-on-a-chip (OAC) models. Collectively, these technologies provide a more physiologically relevant and predictive framework for investigating infectious disease mechanisms and antimicrobial therapies at the intersection of the host, microbe, and their local microenvironments.

Porphyromonas gingivalis bypasses epithelial barrier and modulates fibroblastic inflammatory response in an in vitro 3D spheroid model

Porphyromonas gingivalis-induced inflammatory effects are mostly investigated in monolayer cultured cells. The aim of this study was to develop a 3D spheroid model of gingiva to take into account epithelio-fibroblastic interactions. Human gingival epithelial cells (ECs) and human oral fibroblasts (FBs) were cultured by hanging drop method to generate 3D microtissue (MT) whose structure was analyzed on histological sections and the cell-to-cell interactions were observed by scanning and transmission electron microscopy (SEM and TEM). MTs were infected by P. gingivalis and the impact on cell death (Apaf-1, caspase-3), inflammatory markers (TNF-α, IL-6, IL-8) and extracellular matrix components (Col-IV, E-cadherin, integrin β1) was evaluated by immunohistochemistry and RT-qPCR. Results were compared to those observed in situ in experimental periodontitis and in human gingival biopsies. MTs exhibited a well-defined spatial organization where ECs were organized in an external cellular multilayer, while, FBs constituted the core. The infection of MT demonstrated the ability of P. gingivalis to bypass the epithelial barrier in order to reach the fibroblastic core and induce disorganization of the spheroid structure. An increased cell death was observed in fibroblastic core. The development of such 3D model may be useful to define the role of EC–FB interactions on periodontal host-immune response and to assess the efficacy of new therapeutics.

The relationship between sex hormones, the vaginal microbiome and immunity in HIV-1 susceptibility in women

The role of sex hormones in regulating immune responses in the female genital tract has been recognized for decades. More recently, it has become increasingly clear that sex hormones regulate susceptibility to sexually transmitted infections through direct and indirect mechanisms involving inflammation and immune responses. The reproductive cycle can influence simian/human immunodeficiency virus (SHIV) infections in primates and HIV-1 infection in ex vivo cervical tissues from women. Exogenous hormones, such as those found in hormonal contraceptives, have come under intense scrutiny because of the increased susceptibility to sexually transmitted infections seen in women using medroxyprogesterone acetate, a synthetic progestin-based contraceptive. Recent meta-analyses concluded that medroxyprogesterone acetate enhanced HIV-1 susceptibility in women by 40%. In contrast, estradiol-containing hormonal contraceptives were not associated with increased susceptibility and some studies reported a protective effect of estrogen on HIV/SIV infection, although the underlying mechanisms remain incompletely understood. Recent studies describe a key role for the vaginal microbiota in determining susceptibility to sexually transmitted infections, including HIV-1. While Lactobacillus spp.-dominated vaginal microbiota is associated with decreased susceptibility, complex microbiota, such as those seen in bacterial vaginosis, correlates with increased susceptibility to HIV-1. Interestingly, sex hormones are inherently linked to microbiota regulation in the vaginal tract. Estrogen has been postulated to play a key role in establishing a Lactobacillus-dominated microenvironment, whereas medroxyprogesterone acetate is linked to hypo-estrogenic effects. The aim of this Review is to contribute to a better understanding of the sex-hormone-microbiome-immunity axis, which can provide key information on the determinants of HIV-1 susceptibility in the female genital tract and, consequently, inform HIV-1 prevention strategies.

An Organotypic Reconstructed Human Urethra to Study Chlamydia trachomatis Infection

Organotypic models to investigate host-microbiome interactions are still a challenge for the field of tissue engineering. This is particularly the case for organs such as the urethra. Several cell line, animal, and tissue models are available to study Chlamydia trachomatis infections, but none fully reflects natural infection in native human tissue. Therefore, we developed an organotypic reconstructed human urethral model (RhU) to study invasive and noninvasive strains of C. trachomatis. Primary urethra cells were used to reconstruct epithelium on a fibroblast populated collagen-fibrin hydrogel, yielding a RhU. Immunohistochemistry was used to compare RhU with native urethral tissue and to visualize the location of C. trachomatis bacteria in RhU after 10-day exposure. RhU closely resembled native urethral tissue with respect to proliferation and differentiation markers (keratins 6, 10, 13, 17, involucrin, SKALP [skin-derived antileucoproteinase], vimentin, and CD31). Exposure of RhU to noninvasive and invasive C. trachomatis strains revealed relevant differences in infection ability because inclusions were observed (indicating active infection) in the epithelial layer after 10 days exposure only to the invasive strain. The noninvasive strain remained localized on the surface of the epithelial layer. Human primary urethral fibroblasts and keratinocytes can be used to construct RhU that closely resembles native tissue and can be used to investigate active C. trachomatis infections. RhU provides a promising model to investigate host-microbiome interactions such as, but not limited to, the human pathogenesis of C. trachomatis.

Pathogenesis of Neisseria gonorrhoeae in the female reproductive tract: neutrophilic host response, sustained infection, and clinical sequelae

PURPOSE OF REVIEW

Gonorrhea is a major global health concern, caused by the bacterium Neisseria gonorrhoeae. The main clinical feature of acute gonorrhea is neutrophilic influx that is unable to clear infection. Women of reproductive age are predominantly at risk for serious sequelae of gonorrhea, including pelvic inflammatory disease, ectopic pregnancy, and infertility. This review will highlight how neutrophils are recruited to the female reproductive tract (FRT) in response to N. gonorrhoeae, how N. gonorrhoeae resists killing by neutrophils, and the connection between neutrophilic inflammation and cellular damage.

RECENT FINDINGS

Epithelial cells and immune cells of the FRT recognize and respond to N. gonorrhoeae lipid A and heptose bisphosphate of lipooligosaccharide, porin, lipoproteins, and peptidoglycan fragments. N. gonorrhoeae skews the resulting immune response toward a neutrophilic, Th17-like response. N. gonorrhoeae has multiple, nonredundant mechanisms to survive inside neutrophils and in neutrophil extracellular traps. Infection that ascends to the upper FRT induces the further release of inflammatory cytokines and matrix metalloproteinases, which cause epithelial damage.

SUMMARY

N. gonorrhoeae is remarkable in its ability to recruit neutrophils, yet survive in their midst. New models being developed for FRT infection with N. gonorrhoeae will be useful to reveal the mechanisms underlying these observations.

Uterine Microbiota: Residents, Tourists, or Invaders?

Uterine microbiota have been reported under various conditions and populations; however, it is uncertain the level to which these bacteria are residents that maintain homeostasis, tourists that are readily eliminated or invaders that contribute to human disease. This review provides a historical timeline and summarizes the current status of this topic with the aim of promoting research priorities and discussion on this controversial topic. Discrepancies exist in current reports of uterine microbiota and are critically reviewed and examined. Established and putative routes of bacterial seeding of the human uterus and interactions with distal mucosal sites are discussed. Based upon the current literature, we highlight the need for additional robust clinical and translational studies in this area. In addition, we discuss the necessity for investigating host–microbiota interactions and the physiologic and functional impact of these microbiota on the local endometrial microenvironment as these mechanisms may influence poor reproductive, obstetric, and gynecologic health outcomes and sequelae.