A role for the endometrial microbiome in dysfunctional menstrual bleeding

Microorganisms in the healthy upper reproductive tract: from denial to beneficial assignments for reproductive biology

Contrary to the traditional assumption of a sterile uterus, the number of studies characterizing microbial entities in the healthy upper reproductive tract (endometrial cavity, including follicular fluid and placenta) have been on the increase. Substantial data has been accumulated correlating microbial composition with fertility outcome. In this context, the presence of certain taxa was associated to an improved reproductive success. A summarization for the evidence of these molecular mechanisms through which bacteria may affect developmental processes during pregnancy is presented and discussed with special focus placed upon the immunological aspects.

Regulation of Inflammation Pathways and Inflammasome by Sex Steroid Hormones in Endometriosis

Endometriosis is a gynecological disorder characterized by the growth of endometrial tissue (glands and stroma) outside the uterus, mainly in the peritoneal cavity, ovaries, and intestines. This condition shows estrogen dependency and progesterone resistance, and it has been associated with chronic inflammation, severe pain, and infertility, which negatively affect the quality of life in reproductive women. The molecular mechanisms involved in the pathogenesis of endometriosis are not completely understood; however, inflammation plays a key role in the pathophysiology of the disease, mainly by altering the function of immune cells (macrophages, natural killer, and T cells) and increasing levels of pro-inflammatory mediators in the peritoneal cavity, endometrium, and blood. These immune alterations inhibit apoptotic pathways and promote adhesion and proliferation of endometriotic cells, as well as angiogenesis and neurogenesis in endometriotic lesions. It has been demonstrated that hormonal alterations in endometriosis are related to the inflammatory unbalance in this disease. Particularly, steroid hormones (mainly estradiol) promote the expression and release of pro-inflammatory factors. Excessive inflammation in endometriosis contributes to changes of hormonal regulation by modulating sex steroid receptors expression and increasing aromatase activity. In addition, dysregulation of the inflammasome pathway, mediated by an alteration of cellular responses to steroid hormones, participates in disease progression through preventing cell death, promoting adhesion, invasion, and cell proliferation. Furthermore, inflammation is involved in endometriosis-associated infertility, which alters endometrium receptivity by impairing biochemical responses and decidualization. The purpose of this review is to present current research about the role of inflammasome in the pathogenesis of endometriosis as well as the molecular role of sex hormones in the inflammatory responses in endometriosis.

Fallopian tube microbiota: evidence beyond DNA

AIM

To determine whether cultivation-dependent and -independent analyses identifying fallopian tube bacteria were associated with visually observable microbial cells in situ using scanning electron microscopy.

PATIENTS

Fallopian tubes were collected from pre- and postmenopausal women undergoing salpingectomies for benign disease or as prophylaxis.

MATERIALS & METHODS

Fresh fallopian tube samples were processed for scanning electron microscopy to characterize fallopian tube ultrastructure. Histopathology was used to exclude fallopian tube abnormalities and for menstrual cycle staging of the endometrium.

RESULTS

Scanning electron microscopy revealed observable microbial cells in fallopian tube samples.

CONCLUSION

In the absence of inflammatory pathology, the fallopian tube harbors a visually observable microbial population, which correlates with cultivation-dependent and -independent data, further refuting the sterility of this anatomical niche.

The fallopian tube microbiome: implications for reproductive health

Objective

There is a paucity of data characterizing the microbiota of the female upper genital tract, which controversially is described as a sterile site. We examine whether the fallopian tube harbours an endogenous microbial community.

Design

This prospective study collected from women undergoing total hysterectomy or salpingectomy-oophorectomy.

Setting

Private hospital gynaecology department.

Patients

Fallopian tubes were collected from women diagnosed with benign disease or for prophylaxis.

Interventions

Samples were interrogated for the presence of microbial DNA using a next generation sequencing technology approach to exploit the V5 to V9 regions of the 16S rRNA gene.

Main outcome measures

The fallopian tube microbiota was characterized using traditional culture techniques and next generation sequencing.

Results

Bacteria were isolated from 50% of cultured samples, and 100% of samples returned positive PCR results. Only 68% of the culture isolates could be confidently identified using automated diagnostic equipment in a clinical microbiology laboratory. Monomicrobial communities were identified only for cultured isolates (50%). Pyrosequencing revealed that all communities were polymicrobial. Lactobacillus spp. were not present in all groups, nor were they the most dominant isolates. Distinct differences in the microbial communities were evident for left compared to right fallopian tubes, ampulla versus isthmus, pre- and post- menopausal tissue, and in secretory phase fallopian tubes with and without Mirena intrauterine devices in situ (all p < 0.05).

Conclusion

The female upper genital tract is not sterile. Distinct microbial community profiles in the fallopian tubes of healthy women suggest that this genital tract site supports an endogenous microbiota.