Microorganisms within human follicular fluid: effects on IVF

[Impact of air quality on practices and results in the IVF laboratory]

The concept of Air Quality often refers to particulate and microbiological contamination of ambiant air. European Directive 2006/86/CE encompass the IVF process and specify a class A air quality for manipulation of tissue and cells, in a class D environment (A over D rule). Recognizing the paramount importance of ensuring the highest microbiological and particulate safety in the IVF laboratory, it is equally important to take into account practicability issues and the financial burden of these recommendations, as well as the utter need to protect gametes and embryo viability during their IVF journey. The usefulness of such stringent recommendations may also be questionned given the absence of published cases of airborne contaminations and related patients infections after embryo transfer. The European directive stems from pharmaceutical standards and were not specifically designed for human IVF. Gametes and embryos are indeed extremely sensitive to physical and chemical stress and require strict temperature, osmolarity and pH control, as well as an absence of chemical contamination during manipulation and culture. These conditions are hardly obtained when using laminar flow hoods. Following concerns raised by many experts in the field, exceptions to the A over D rule were added in the 2006/86/CE Directives. This narrative review discusses all these aspects in a critical way and compare scientific and legal requirements applying to IVF practices in different regions of the world.

The matter of the reproductive microbiome

The preconceptional presence of microbiota in the female and male reproductive organs suggests that fertilization is taking place in a nonsterile environment and contributes to reproductive success. The concept of embryonic development in a sterile uterus has also been challenged with recent reports of the existence of a microbiome of the placenta, amniotic fluid and the fetal gut in normal, uncomplicated pregnancies. The maternal origins of the microbiota colonising the fetus and its surroundings are unknown as are the mechanisms of maternal-to-fetal transfer. In this review, we aim to highlight the preconception male and female microbiome, the maternal vaginal and gut microbiome during pregnancy and the fetal microbiome, including their possible roles in reproduction, and maternal and neonatal pregnancy outcome.

Initial meconium microbiome in Chinese neonates delivered naturally or by cesarean section

Previous studies have revealed significant differences in microbiome compositions between infants delivered via cesarean section (C-section) and natural vaginal birth. However, the importance of the delivery mode in the first days of life remains unclear. Importantly, this stage is minimally affected by infant feeding. Here, we used a metagenomic sequencing technique to characterize the meconium microbiome from the feces of a Chinese cohort of vaginally and C-section-delivered infants, including in vitro fertilization (IVF) newborns, during the first 24 h after birth. Meconium microbiome diversity was higher in vaginally delivered infants than that in C-section-delivered infants. Propionibacterium species were most abundant in the vaginally delivered infants, whereas the C-section group had high levels of Bacillus licheniformis. The two IVF newborns delivered by C-section harbored microbial communities similar to the vaginal microbiome in terms of taxonomic composition. Metabolic functions of the C-section group suffered more from the influence of the dominant group (B. licheniformis), whereas the vaginal group was more homogeneous, with a metabolism dominated by multi-microbes. Moreover, different modes of delivery affected the antibiotic resistance gene (ARG) prevalence. These findings provide novel information for the development of strategies to guide a healthy mode of delivery and promote the formation of healthy microbiota.

A role for the endometrial microbiome in dysfunctional menstrual bleeding

This study aimed to characterise the microbial community within the endometrial cavity and endocervix in women with menorrhagia or dysmenorrhea. Paired endocervical and endometrial biopsy samples were collected from women undergoing operative hysteroscopy and/or laparoscopy. Samples were cohorted based on pathology, indications for surgery, and histological dating of the endometrium. Samples were interrogated for the presence of microbial DNA using a two-step next generation sequencing technology approach to exploit the V5-V8 regions of the 16S rRNA gene. Pyrosequencing revealed that the endocervix and endometrium share a minor microbial community, but that each site harbours a separate and distinct microbial population (p = 0.024). This was also the case for women with menorrhagia and dysmenorrhea (p = 0.017). Lactobacillus spp. were the most abundant microbial taxa present in 50% of the cohorts, and across all endocervical groups. Members of the genera Prevotella, Fusobacterium and Jonquetella were the most abundant taxa identified in samples collected from nulliparous women. It can be concluded that the female upper genital tract is not sterile. Microbial community profiling revealed differences in the endometrial microbial community profiles for: (1) the endocervix compared to the endometrium, and (2), women with menorrhagia versus dysmenorrhea. The distinct microbial community profiles in these women may offer insight into the pathology and clinical management of dysfunctional menstrual bleeding.

Human granulosa-luteal cells initiate an innate immune response to pathogen-associated molecules

The microenvironment of the ovarian follicle is key to the developmental success of the oocyte. Minor changes within the follicular microenvironment can significantly disrupt oocyte development, compromising the formation of competent embryos and reducing fertility. Previously described as a sterile environment, the ovarian follicle of women has been shown to contain colonizing bacterial strains, whereas in domestic species, pathogen-associated molecules are concentrated in the follicular fluid of animals with uterine infection. The aim of this study is to determine whether human granulosa-luteal cells mount an innate immune response to pathogen-associated molecules, potentially disrupting the microenvironment of the ovarian follicle. Human granulosa-luteal cells were collected from patients undergoing assisted reproduction. Cells were cultured in the presence of pathogen-associated molecules (LPS, FSL-1 and Pam3CSK4) for 24h. Supernatants and total RNA were collected for assessment by PCR and ELISA. Granulosa-luteal cells were shown to express the molecular machinery required to respond to a range of pathogen-associated molecules. Expression of TLR4 varied up to 15-fold between individual patients. Granulosa-luteal cells increased the expression of the inflammatory mediators IL1B, IL6 and CXCL8 in the presence of the TLR4 agonist E. coli LPS. Similarly, the TLR2/6 ligand, FSL-1, increased the expression of IL6 and CXCL8. Although no detectable changes in CYP19A1 or STAR expression were observed in granulosa-luteal cells following challenge, a significant reduction in progesterone secretion was measured after treatment with FSL-1. These findings demonstrate the ability of human granulosa-luteal cells to respond to pathogen-associated molecules and generate an innate immune response.

The microbiota continuum along the female reproductive tract and its relation to uterine-related diseases

Reports on bacteria detected in maternal fluids during pregnancy are typically associated with adverse consequences, and whether the female reproductive tract harbours distinct microbial communities beyond the vagina has been a matter of debate. Here we systematically sample the microbiota within the female reproductive tract in 110 women of reproductive age, and examine the nature of colonisation by 16S rRNA gene amplicon sequencing and cultivation. We find distinct microbial communities in cervical canal, uterus, fallopian tubes and peritoneal fluid, differing from that of the vagina. The results reflect a microbiota continuum along the female reproductive tract, indicative of a non-sterile environment. We also identify microbial taxa and potential functions that correlate with the menstrual cycle or are over-represented in subjects with adenomyosis or infertility due to endometriosis. The study provides insight into the nature of the vagino-uterine microbiome, and suggests that surveying the vaginal or cervical microbiota might be useful for detection of common diseases in the upper reproductive tract.

Whether the female reproductive tract harbours distinct microbiomes beyond the vagina has been a matter of debate. Here, the authors show a subject-specific continuity in microbial communities at six sites along the female reproductive tract, indicative of a non-sterile environment.

Women and Their Microbes: The Unexpected Friendship

Communities of microbiota have been associated with numerous health outcomes, and while much emphasis has been placed on the gastrointestinal niche, there is growing interest in the microbiome specific for female reproductive health and the health of their offspring. The vaginal microbiome plays an essential role not only in health and dysbiosis, but also potentially in successful fertilization and healthy pregnancies. In addition, microbial communities have been isolated from formerly forbidden sterile niches such as the placenta, breast, uterus, and Fallopian tubes, strongly suggesting an additional microbial role in women's health. A combination of maternally linked prenatal, birth, and postnatal factors, together with environmental and medical interventions, influence early and later life through the microbiome. Here, we review the role of microbes in female health focusing on the vaginal tract and discuss how male and female reproductive microbiomes are intertwined with conception and how mother-child microbial transfer is a key determinant in infant health, and thus the next generation.

Left-right differences in ovarian volume and antral follicle count in 1423 women of reproductive age

The aim of this cross-sectional study was to investigate side differences in antral follicle count (AFC) and ovarian volume in left versus right ovaries in relation to chronological and "biological" age, the latter estimated by anti-Müllerian hormone (AMH) levels. The cohort comprised 1423 women: 1014 fertile and 409 infertile. All were examined by transvaginal sonography and serum AMH. Overall the right ovary contained 8.1% more antral follicles (p = 0.002) and had 10.7% larger volume compared with the left (p < 0.001). In all AMH quartiles, the right ovarian volume was larger than the left (p ≤ 0.003). AFC was significantly higher in the right compared to the left ovary in the three upper AMH quartiles (p ≤ 0.005). The findings were similar when stratified in age quartiles. More than half (54.8%) had polycystic ovarian (PCO) morphology in at least one ovary. Of these women, 46.3% (n = 361) had PCO morphology unilateral - most frequently on the right side (27.6%) compared to the left (18.7%, p < 0.001). The consistent difference in AFC and ovarian volume found in AMH and age quartiles may be explained by presence of a larger pool of primordial follicles in the right ovary established during fetal life.

Host Responses to Biofilm

From birth to death the human host immune system interacts with bacterial cells. Biofilms are communities of microbes embedded in matrices composed of extracellular polymeric substance (EPS), and have been implicated in both the healthy microbiome and disease states. The immune system recognizes many different bacterial patterns, molecules, and antigens, but these components can be camouflaged in the biofilm mode of growth. Instead, immune cells come into contact with components of the EPS matrix, a diverse, hydrated mixture of extracellular DNA (bacterial and host), proteins, polysaccharides, and lipids. As bacterial cells transition from planktonic to biofilm-associated they produce small molecules, which can increase inflammation, induce cell death, and even cause necrosis. To survive, invading bacteria must overcome the epithelial barrier, host microbiome, complement, and a variety of leukocytes. If bacteria can evade these initial cell populations they have an increased chance at surviving and causing ongoing disease in the host. Planktonic cells are readily cleared, but biofilms reduce the effectiveness of both polymorphonuclear neutrophils and macrophages. In addition, in the presence of these cells, biofilm formation is actively enhanced, and components of host immune cells are assimilated into the EPS matrix. While pathogenic biofilms contribute to states of chronic inflammation, probiotic Lactobacillus biofilms cause a negligible immune response and, in states of inflammation, exhibit robust antiinflammatory properties. These probiotic biofilms colonize and protect the gut and vagina, and have been implicated in improved healing of damaged skin. Overall, biofilms stimulate a unique immune response that we are only beginning to understand.

Characterisation of the human uterine microbiome in non-pregnant women through deep sequencing of the V1-2 region of the 16S rRNA gene

Background. It is widely assumed that the uterine cavity in non-pregnant women is physiologically sterile, also as a premise to the long-held view that human infants develop in a sterile uterine environment, though likely reflecting under-appraisal of the extent of the human bacterial metacommunity. In an exploratory study, we aimed to investigate the putative presence of a uterine microbiome in a selected series of non-pregnant women through deep sequencing of the V1-2 hypervariable region of the 16S ribosomal RNA (rRNA) gene.

Methods. Nineteen women with various reproductive conditions, including subfertility, scheduled for hysteroscopy and not showing uterine anomalies were recruited. Subjects were highly diverse with regard to demographic and medical history and included nulliparous and parous women. Endometrial tissue and mucus harvesting was performed by use of a transcervical device designed to obtain endometrial biopsy, while avoiding cervicovaginal contamination. Bacteria were targeted by use of a barcoded Illumina MiSeq paired-end sequencing method targeting the 16S rRNA gene V1-2 region, yielding an average of 41,194 reads per sample after quality filtering. Taxonomic annotation was pursued by comparison with sequences available through the Ribosomal Database Project and the NCBI database.

Results. Out of 183 unique 16S rRNA gene amplicon sequences, 15 phylotypes were present in all samples. In some 90% of the women included, community architecture was fairly similar inasmuch B. xylanisolvens, B. thetaiotaomicron, B. fragilis and an undetermined Pelomonas taxon constituted over one third of the endometrial bacterial community. On the singular phylotype level, six women showed predominance of L. crispatus or L. iners in the presence of the Bacteroides core. Two endometrial communities were highly dissimilar, largely lacking the Bacteroides core, one dominated by L. crispatus and another consisting of a highly diverse community, including Prevotella spp., Atopobium vaginae, and Mobiluncus curtisii.

Discussion. Our findings are, albeit not necessarily generalizable, consistent with the presence of a unique microbiota dominated by Bacteroides residing on the endometrium of the human non-pregnant uterus. The transcervical sampling approach may be influenced to an unknown extent by endocervical microbiota, which remain uncharacterised, and therefore warrants further validation. Nonetheless, consistent with our understanding of the human microbiome, the uterine microbiota are likely to have a previously unrecognized role in uterine physiology and human reproduction. Further study is therefore warranted to document community ecology and dynamics of the uterine microbiota, as well as the role of the uterine microbiome in health and disease.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Microbes central to human reproduction

As studies uncover the breadth of microbes associated with human life, opportunities will emerge to manipulate and augment their functions in ways that improve health and longevity. From involvement in the complexities of reproduction and fetal/infant development, to delaying the onset of disease, and indeed countering many maladies, microbes offer hope for human well-being. Evidence is emerging to suggest that microbes may play a beneficial role in body sites traditionally viewed as being sterile. Although further evidence is required, we propose that much of medical dogma is about to change significantly through recognition and understanding of these hitherto unrecognized microbe–host interactions. A meeting of the International Scientific Association for Probiotics and Prebiotics held in Aberdeen, Scotland (June 2014), presented new views and challenged established concepts on the role of microbes in reproduction and health of the mother and infant. This article summarizes some of the main aspects of these discussions.

Establishment of a xeno-free culture system that preserves the characteristics of placenta mesenchymal stem cells

Although stem cells are promising candidates for cell replacement therapies, the vast majority are derived using animal sera, which has risk of being contaminated by animal viruses or toxins. To overcome these potential problems, we initially established multiple lines of stem cells from first-trimester human placenta (fPMSC), which were cultivated using human follicular fluid (hFF) instead of fetal bovine serum (FBS). FF provides a very important microenvironment for the development of oocytes. No differences were found in the general morphology, growth rate, karyotype, gene and surface expressions between placental MSCs cultured in 5 % hFF-supplemented medium (fPMSC-X) or 10 % FBS-supplemented medium (fPMSC). Differentiation experiments confirmed similar levels of potency in cells grown in either condition. Since hFF preserved the unique features of the stem cells and is free from potential pathogens, it should be considered as the main culture medium supplement for the propagation of human stem cells for clinical applications.

TUNEL analysis of DNA fragmentation in mouse unfertilized oocytes: the effect of microorganisms within human follicular fluid collected during IVF cycles

Recently we reported the presence of bacteria within follicular fluid. Previous studies have reported that DNA fragmentation in human spermatozoa after in vivo or in vitro incubation with bacteria results in early embryo demise and a reduced rate of ongoing pregnancy, but the effect of bacteria on oocytes is unknown. This study examined the DNA within mouse oocytes after 12 hours' incubation within human follicular fluids (n=5), which were collected from women undergoing in vitro fertilization (IVF) treatment. Each follicular fluid sample was cultured to detect the presence of bacteria. Terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL) was used to label DNA fragmentation in ovulated, non-fertilized mouse oocytes following in vitro incubation in human follicular fluid. The bacteria Streptococcus anginosus and Peptoniphilus spp., Lactobacillus gasseri (low-dose), L. gasseri (high-dose), Enterococcus faecalis, or Propionibacterium acnes were detected within the follicular fluids. The most severe DNA fragmentation was observed in oocytes incubated in the follicular fluids containing P. acnes or L. gasseri (high-dose). No DNA fragmentation was observed in the mouse oocytes incubated in the follicular fluid containing low-dose L. gasseri or E. faecalis. Low human oocyte fertilization rates (<29%) were associated with extensive fragmentation in mouse oocytes (80-100%). Bacteria colonizing human follicular fluid in vivo may cause DNA fragmentation in mouse oocytes following 12h of in vitro incubation. Follicular fluid bacteria may result in poor quality oocytes and/or embryos, leading to poor IVF outcomes.