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Endometriosis and the microbiome: a systematic review


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Background: The aetiology and pathogenesis of endometriosis is still under investigation. There is evidence that there is a complex bidirectional interaction between endometriosis and the microbiome. Objective: To systematically review the available literature on the endometriosis-microbiome interaction, with the aim of guiding future inquiries in this emerging area of endometriosis research. Search strategy: MEDLINE, Embase, Scopus, and Web of Science were searched through May 2019. A manual search of reference lists of relevant studies was also done. Selection criteria: Published and unpublished literature in any language describing a comparison of the microbiome state in mammalian hosts with and without endometriosis. Data collection and analysis: Identified studies were screened and assessed independently by two authors. Data was extracted and compiled in a qualitative synthesis of the evidence. Main results: Endometriosis appears to be associated with an increased presence of Proteobacteria, Enterobacteriaceae, Streptococcus and Escherichia coli across various microbiome sites. The phylum Firmicutes and the genera Gardnerella also appear to have an association, however this remains unclear. Conclusions: The complex bidirectional relationship between the microbiome and endometriosis has begun to be characterised by the studies highlighted in this systematic review. Laboratory and clinical studies demonstrate that there are indeed differences in the microbiome composition of hosts with and without endometriosis. This article is protected by copyright. All rights reserved.
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Endometriosis and the microbiome: a systematic
M Leonardi,
C Hicks,
F El-Assaad,
E El-Omar,
G Condous
Acute Gynaecology, Early Pregnancy and Advanced Endosurgery Unit, Sydney Medical School Nepean, University of Sydney, Nepean
Hospital, Sydney, NSW, Australia
Microbiome Research Centre, St George and Sutherland Clinical School, UNSW Sydney, Kogarah, NSW,
Correspondence: Dr M Leonardi, Acute Gynaecology, Early Pregnancy and Advanced Endosurgery Unit, Nepean Hospital, Sydney Medical
School Nepean, University of Sydney, 62 Derby St, Kingswood, NSW 2747, Australia. Email:
Accepted 8 August 2019. Published Online 20 September 2019.
Background The aetiology and pathogenesis of endometriosis are
still under investigation. There is evidence that there is a complex
bidirectional interaction between endometriosis and the
Objective To systematically review the available literature on the
endometriosismicrobiome interaction, with the aim of guiding
future inquiries in this emerging area of endometriosis research.
Search strategy MEDLINE, Embase, Scopus and Web of Science
were searched through May 2019. A manual search of reference
lists of relevant studies was also performed.
Selection criteria Published and unpublished literature in any
language describing a comparison of the microbiome state in
mammalian hosts with and without endometriosis.
Data collection and analysis Identified studies were screened and
assessed independently by two authors. Data were extracted and
compiled in a qualitative synthesis of the evidence.
Main results Endometriosis appears to be associated with an
increased presence of Proteobacteria, Enterobacteriaceae,
Streptococcus spp. and Escherichia coli across various microbiome
sites. The phylum Firmicutes and the genus Gardnerella also
appear to have an association; however, this remains unclear.
Conclusions The complex bidirectional relationship between the
microbiome and endometriosis has begun to be characterised by
the studies highlighted in this systematic review. Laboratory and
clinical studies demonstrate that there are indeed differences in
the microbiome composition of hosts with and without
Keywords 16S ribosomal RNA gene sequencing, dysbiosis,
endometriosis, microbiota, systematic review.
Tweetable abstract Review findings show endometriosis associated
with increased Proteobacteria, Enterobacteriaceae,Streptococcus and
Escherichia coli across various microbiome sites.
Please cite this paper as: Leonardi M, Hicks C, El-Assaad F, El-Omar E, Condous G. Endometriosis and the microbiome: a systematic review. BJOG 2019;
Endometriosis is an inflammatory disease process, charac-
terised by lesions of endometrium-like tissue outside the
uterus, commonly affecting women of reproductive age.
Primarily, it causes dysmenorrhoea and subfertility, but can
also yield non-cyclical or chronic pelvic pain, deep dyspareu-
nia and dyschezia.
The severity of patient symptomatology
and disease state are not correlated, even to the extent that a
person can be asymptomatic with advanced endometriosis.
Sampson’s theory of retrograde menstruation remains
the most convincing hypothesis for the origin of
Other theories such as the coelomic
metaplasia, embryonic rest, stem cell and immune dysfunc-
tion theories may fill gaps left by Sampson’s theory.
A dysregulated immune response,
characterised by
increased production of pro-inflammatory cytokines, auto-
antibodies, growth factors, oxidative stress, decreased T-cell
and natural killer cell reactivity, increased activation and
presence of peritoneal macrophage, B cells, antibody pro-
duction and angiogenesis, may contribute to an immuno-
suppressive environment that enables the growth of
escaped ectopic endometrial cells outside the uterus,
potentially explaining why some women develop
endometriosis following retrograde menstruation, while
others do not.
1ª2019 Royal College of Obstetricians and Gynaecologists
DOI: 10.1111/1471-0528.15916
Systematic review
The microbiome
The microbiome encapsulates all the genetic material of the
microbes, including bacteria, fungi, viruses and Archaea,
that live within the host and regulate several physiological
The influence of the microbiome on
immunomodulation and the development of several
inflammatory diseases is well established.
Much is known
on how the gut microbiome maintains the integrity of the
gastrointestinal epithelial lining as well as immune home-
ostasis, preventing bacterial translocation, which can cause
low-grade systemic inflammation.
Immune homeostasis
ensures that the immune system shows tolerance towards
commensals and self-antigens but is still responsive to
Conversely, little is known about the presence and com-
position of the microbiome along the female reproductive
tract and its role in the development of endometriosis or
other gynaecological conditions. Considering the altered
inflammatory status in endometriosis, postulating that the
microbiome is involved is logical. Chen et al.
recently described the existence of unique bacterial com-
munities along the female reproductive tract from the
vagina to the ovaries. Interestingly, the microbiome influ-
ences estrogen metabolism and estrogen influences the gut
Considering that endometriosis is an estro-
gen-dominant condition,
gut dysbiosis leading to abnor-
mal levels of circulating estrogen could potentially
contribute to the development of this disease.
The aim of this systematic review is to understand the
bidirectional interaction between the microbiome and
endometriosis and to establish possible concordance
between the various studies.
A comprehensive systematic review was performed to iden-
tify observational studies that compared the microbiome in
humans or other species with endometriosis to those with-
out. The review was performed according to recommended
methods for systematic reviews and reported according to
PRISMA guidelines.
Search strategies
The following databases were searched from inception until
May 2019: MEDLINE and Embase via OvidSP, Web of
Science Core Collection and Scopus. OpenGrey was used to
search for grey literature. The electronic search algorithm
consisted of terms relating to key concepts of
‘endometriosis’ and ‘microbiome’ (see Supplementary
material, Appendix S1).
Reference lists of relevant articles and related reviews
were manually searched to identify papers not captured by
the electronic searches. Authors were contacted for further
information when necessary. There were no language
restrictions in the search or selection of papers. Studies
were uploaded to COVIDENCE (Veritas Health Innovation,
Melbourne, Australia).
Selection of studies
All studies, published and unpublished in any language at
any time, were considered for inclusion. Eligible studies
were selected if the focus of the paper was the interaction
of endometriosis and the microbiome in mammalian hosts.
Only studies that included a cohort of cases (i.e. with
endometriosis) and a cohort of controls (i.e. without
endometriosis) were considered eligible. Outcomes
included any comparison of the microbiome composition
in tissues of mammalian hosts with and without
endometriosis. Where the same cases and controls were
included in more than one publication (e.g. abstract and
full-text manuscript), only the publication offering the
most detailed information was included. Abstracts were
considered eligible if no full-text manuscript was available.
Eligibility assessment and data extraction
Two authors (ML and GC) independently screened titles
and abstracts. Discrepancies were resolved by consensus
between ML and GC. Full-text assessment was then done
by ML and GC. Again, discrepancies were resolved by con-
sensus between ML and GC. Data extraction was completed
by CH for the following: study design, research objectives,
setting (laboratory, field), case and control subjects/condi-
tions, host type (and source, for animal subjects),
endometriosis state (when relevant/documented), microbial
community (e.g. intestinal, reproductive tract), method of
characterisation of the microbiome, phylotype and/or other
relevant features of the microbiome, and study findings.
Data analysis
Findings of relevant studies were organised in a qualitative
synthesis according to host type, method of characterisa-
tion of the microbiome and phylotype. The general direc-
tion of association was sought from the included
Quality assessment
For human studies and the sole Rhesus monkey study,
quality was assessed on the basis of NewcastleOttawa
Scale (NOS) for casecontrol studies.
For mouse model
studies, the SYstematic Review Centre for Laboratory ani-
mal Experimentation (SYRCLE) risk-of-bias assessment
tool was used.
Risk-of bias-assessment was performed
by ML.
Patient and public involvement
There was no patient or public involvement in this study.
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Number of retrieved papers
The systematic search, depicted in the Supplementary
material (Figure S1), resulted in 251 records. These were
uploaded to COVIDENCE and 106 duplicates were immedi-
ately removed. Titles and abstracts were screened and
112 studies were deemed irrelevant and therefore
excluded. A full-text review was carried out for the
remaining 33 studies. Two studies included participants
from the same study and therefore only the report
including the most detailed information needed for this
review was included,
whereas the other was excluded.
Eighteen studies published between 2002 and 2019 were
included (see Supplementary material, Table S1).
Excluded studies are shown in the Supplementary
material (Table S2).
Quality assessment
Risk of bias assessment using the NOS and SYRCLE tools
revealed overall poor to moderate study quality, with many
criteria not being met or not being clearly stated in the text
(see Supplementary material, Table S3A,B). Unclear or
absent from the full texts in all but one human study
whether study participants were consecutively recruited,
permitting the closest representation of patients with
endometriosis. Human studies that had an NOS score of
6 (out of 8, as the nonresponse rate category was not
applicable for these study methodologies) had reliably
strong definitions of cases versus controls, appropriate
selection of controls, and laparoscopic evidence of
endometriosis presence or absence.
Characteristics of included studies
Animal model studies
Five of the eighteen studies identified were conducted using
animal models. One study involved the use of rhesus mon-
keys as a non-human primate model,
whereas the remain-
ing four studies used murine or rodent models.
included Sprague-Dawley
and C57BL
models; however,
one study did not declare which murine model was used.
Endometriosis was surgically induced in the murine/rodent
models via intraperitoneal transplantation; however, there
was slight variation among the methods used in each study.
Each of the models used was homologous, and tissue was
transferred from the same animal.
Clinical studies
Thirteen of the eighteen studies identified were clinical
studies that examined various tissue types, including the
gut, vagina, cervix, endometrium, fallopian tubes, ovaries,
peritoneum, peritoneal fluid, follicular fluid, menstrual
blood and ectopic endometriosis lesions. In all studies
except one,
the presence or absence of endometriosis was
confirmed in both patient and control cohorts by laparo-
Microbiome quantification
Various methods were used to quantify the microbiome.
Five of the eighteen studies used the conventional culturing
and colony count method to determine the presence and
abundance of microbial communities.
amplicon sequencing was used in seven stud-
to sequence the genomic material, while
one study used macrogenomic sequencing.
The various kits
and sequencing methods used are outlined in Table 1. Of
the seven studies that used 16S rRNA amplicon sequencing,
only five discussed the targeted sequencing region.
Each study targeted different regions, including region V3/
region V4,
region V3V5,
region V4/V5
region V5/V6.
The remaining studies used an unknown
sequencing region. Additionally, four studies used quantita-
tive polymerase chain rection to detect the presence of
viruses, in particular, human papillomavirus (HPV),
and one study used quantitative polymerase chain rection to
detect the presence of mollicutes.
Diversity assessments
Microbial communities can be characterised through the
use of diversity indices.
a-Diversity is used to describe the
Table 1. Summary of detection and sequencing methodology
Methodology Number of studies
Detection method
Conventional culturing and colony counting 5
16S ribosomal RNA sequencing 7
qPCR 5
Macrogenomic sequencing 1
Data extraction kits
QIAamp DNA Stool Mini Kit (Qiagen) 1
QuickGene DNA tissue kit S (Kurabo) 1
Purelink Genomic DNA Mini Kit (Invitrogen) 1
Power Soil
DNA Extraction Kit (Mobio) 2
DNA Mini Kit (TransGen Biotech) 1
CTAB/SDS method 1
NucleoSpin Microbial DNA 1
Sequencing method
Illumina MiSeq 4
Ion Torrent PGM 4
Macrogenomic sequencing 1
Illumina HiSeq2500 1
16S ribosomal RNA pyrosequencing 1
qPCR 4
CTAB/SDS, cetyltrimethylammonium bromide/sodium dodecyl
sulphate; qPCR, quantitative polymerase chain reaction.
3ª2019 Royal College of Obstetricians and Gynaecologists
Endometriosis and the microbiome
diversity of a microbial community within a single sample
or site whereas b-diversity is an index used to compare the
diversity of microbial communities across different samples
or sites.
Five of eighteen studies assessed a-diver-
Three studies used Shannon’s Diversity
Index to assess a-diversity.
The study by Yuan et al.
also used Simpson’s index, Chao 1, Abundance-based
Coverage Estimator (ACE), Observed Species and Good’s
coverage to assess diversity of the communities. One study
used UniFrac analysis in QIIME to assess a-diversity
one study did not include what method was used for analy-
though this was simply an abstract.
b-Diversity was assessed in three studies.
studies used UniFrac analysis to assess b-diversity
two studies used Principal Coordinate Analysis.
tionally, one study used BrayCurtis dissimilarity index
matrices to assess the diversity.
Outcomes of the included studies
Thirty-six bacterial taxa were identified as being signifi-
cantly different between endometriosis and control groups
(Table 2A, B). Twelve distinct areas of the body were sam-
pled in the studies included in this review (see Supplemen-
tary material, Table S4). The most common sites were the
gastrointestinal tract/stool and endometrium. When differ-
ences were identified, the site of those differences has been
highlighted in Table 2(A, B). The only human studies that
demonstrated statistically significant differences in the bac-
terial taxa originated from Asian countries (China, Japan,
At the phylum level, Actinobacteria,
and Verrucomicrobia
were identified as
being significantly higher in the endometriosis cohort,
compared with controls. However, Firmicutes was also
reported to be significantly decreased in the endometriosis
cohort in one study; although this was not confirmed as
statistically significant because no P-value was provided in
the abstract.
At the class level, Betaproteobacteria was reported as
being significantly higher in the endometriosis population
of mice.
At the order level, Bifidobacteriales and
Burkholderiales were also reported to be significantly
higher in the endometriosis group of mice, while Bac-
teroidales predominated in the mock group.
At the family level, Bifidobacteriaceae and Alcaligenaceae
were found to be significantly increased in animal models
of endometriosis, compared with controls. Staphylococ-
caceae and Streptococcaceae were found to be significantly
increased in women with endometriosis who had been trea-
ted with a gonadotrophin-releasing hormone agonist com-
pared with controls.
In contrast, Lactobacillaceae was
found to be significantly decreased in the same cohort.
Enterobacteriaceae was also reported to be significantly
increased in the endometriosis population of two studies,
including one involving treatment of endometriosis with a
gonadotrophin-releasing hormone agonist.
At the genus level, Atopobium,Barnesiella,Prevotella,
Gemella,Lactobacillus,Dialister,Megasphaera and Sneathia
were found to be significantly decreased in endometriosis
cohorts, compared with control cohorts.
In contrast, Allo-
and Ruminococcaceae were found to be significantly increased
in the endometriosis cohort compared with controls.
The genera Streptococcus and Escherichia were found to
be significantly increased in the endometriosis population
compared with controls in more than one study.
Gardnerella was found to be significantly increased in the
endometrial, vaginal and cervical microbiota across two
but significantly decreased in the stool of
At the species level, Escherichia coli was found to be sig-
nificantly increased in two studies.
Lachnospira,Peptococcaceae and Tyzzerella increased in
mice with endometriosis following treatment with Nei Yi
Fang, a Chinese medicine compound; however, these data
are not confirmed to be statistically significant as they were
derived from an abstract.
The nine detected taxa belonging to the phylum Pro-
teobacteria were all reported to be significantly increased in
endometriosis cohorts, compared with controls, across
seven different studies.
Six of the 18 studies did not specify a significant difference
in microbial taxa between endometriosis and control
Campos et al.
looked exclusively at the
Mollicutes class and specific species (Mycoplasma hominis,
Mycoplasma genitalium,Ureaplasma urealyticum and Urea-
plasma parvum). Chen et al.
describe a microbiota-based
model that can distinguish infertile patients with and without
endometriosis, but they do not highlight the differences in
taxa. Wang et al.
exclusively assessed the peritoneal fluid
using a backward sequencing technique (V5?V4). Cregger
et al.
applied 16S rRNA gene amplification and sequencing
of the hypervariable V3V5 region to cervical and uterine
samples in a small sample size (n=18). Appleyard et al.
used culture media to determine numbers of total bacteria,
total lactobacilli and total Gram-negative bacteria in the jeju-
num or the distal colon of mice. Lastly, the Chompre et al.
abstract states that faecal bacterial composition of mice was
analysed before and after induction of endometriosis, but the
results do not highlight the differences.
Four of the eighteen studies analysed the virome to deter-
mine whether there is an association between HPV and
4ª2019 Royal College of Obstetricians and Gynaecologists
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Table 2. (A) Summary of bacterial taxa part one; (B) summary of bacterial taxa part two
Phylum Class Order Family Genus Species
Yuan 2018
Actinobacteria Bifidobacteriales
Yuan 2018
Yuan 2018 (stool)*
Ata 2019 (stool)
Ata 2019 (vaginal/cervical excluding
Khan 2014 (endometrial)
Coriobacteriia Coriobacteriales Coriobacteriaceae Atopobium
Ata 2019 (vaginal, cervical)
Bacteroidetes Bacteroidetes Bacteroidales Porphyromonadaceae Barnesiella
Ata 2019 (stool)
Prevotellaceae Prevotella
Ata 2019 (vaginal)
Ata 2019 (cervix excluding Lactobacillus)
Ata 2019 (cervical)
Shan 2018
Yuan 2018
Bacilli Bacillales n/a Gemella
Ata 2019 (vaginal)
Khan 2016 (endometrial, ovarian
endometrioma fluid)
Lactobacillales Enterococcaceae Enterococci
Khan 2014 (endometrial)
Khan 2016 (endometrial)
Bailey 2002 (stool)*
Khan 2016 (endometrial, ovarian
endometrioma fluid)
Akiyama 2019 (cervical mucus)
Ata 2019 (cervix excluding Lactobacillus)
Khan 2014 (endometrial)
Firmicutes Clostridia Clostridiales Lachnospiraceae Blautia
Shan 2018 (stool)
Shan 2018 (stool)
Shan 2018 (stool)
Shan 2018 (stool)
Shan 2018 (stool)
5ª2019 Royal College of Obstetricians and Gynaecologists
Endometriosis and the microbiome
Table 2. (Continued)
Phylum Class Order Family Genus Species
Yuan 2018 (stool)*
Negativicutes Selenomonadales Veillonellaceae Dialister
Ata 2019 (cervix excluding Lactobacillus)
Ata 2019 (cervix excluding Lactobacillus)
Fusobacteria Fusobacteriia Fusobacteriales Leptotrichiaceae Sneathia
Ata 2019 (cervical, stool)
Shan 2018
Yuan 2018 (stool)*
Yuan 2018
Yuan 2018 (stool)*
Sutterellaceae Parasutterella
Yuan 2018 (stool)*
Gammaproteobacteria Enterobacteriales Enterobacteriaceae
Akiyama 2019 (cervical mucus)
Khan 2016 (endometrial)
Ata 2019 (vaginal/cervical excluding
Escherichia coli
Khan 2010 (menstrual
Khan 2014
Ata 2019 (vaginal/cervical excluding
Tenericutes Mollicutes Mycoplasmatales Mycoplasmataceae Ureaplasma
Ata 2019 (cervix excluding Lactobacillus)
Shan 2018
= increased, = decreased, = completely absent, * =animal model, = gonadotrophin-releasing hormone agonist, M=increase in endometriotic mice after Nei Yi Fang treatment.
All bacterial taxa included reached statistical significance (P<0.05), excluding results published by Shan et al.
For Ata et al. 2019,
sensitivity analyses excluding Lactobacillus were
conducted on the vaginal and cervical microbiota.
6ª2019 Royal College of Obstetricians and Gynaecologists
Leonardi et al.
(Table 3). Three studies found that
the HPV detection was higher and therefore associated
with endometriosis.
However, one study found that
there was no association at all.
Diversity analyses
Out of the 18 studies, four assessed a-diversity between
endometriosis and control cohorts.
There was no
significant difference between endometriosis and mock
mice in one study,
and this was also reported in a
clinical study.
Another study found that a-diversity was
lower in stressed animals.
Finally, one study found that
a-diversity was significantly higher in the endometriosis
Only three studies assessed b-diversity.
It was
reported in one study that the b-diversity index was sig-
nificantly higher in the endometriosis mice group, com-
pared with controls.
It was also found that the
diversity between vaginal, cervical and gut sites was simi-
lar between endometriosis and control groups in Ata
et al.
Bacteroidetes/Firmicutes ratio
Two studies measured the Bacteroidetes/Firmicutes
One study found that in a mouse model of
endometriosis, the ratio was two-fold higher than in con-
trol mice.
Another study found that the ratio was altered,
but it is unclear in which direction this was.
Endometriosis stage
Table S1 (see Supplementary material) outlines how the
endometriosis in patients in the human studies was clas-
sified. Only three studies specifically stated that there
was no difference in their specific microbiome findings
between groups.
Cregger et al.
specify that Ameri-
can Society of Reproductive Medicine (ASRM) stage III
exhibited ‘differences’ from the other stages, yet there
was only one patient classified as ASRM stage III in
their study. None of the studies included in this review
planned a comparison between ASRM stages as their
primary study design.
Main findings
Endometriosis appears to be associated with elevated levels
of Proteobacteria, Enterobacteriaceae,Streptococcus and
E. coli across various microbiome sites. The phylum Firmi-
cutes and genus Gardnerella also appear to have an associa-
tion, but the studies were sometimes conflicting. Nine
different taxa were reported to be significantly increased in
the endometriosis cohort, across seven separate studies
(Table 2A, B).
Table 3. Summary of virome detection
Study ID Method Tissue type Virus detection rate
Human papillomaviruses Herpes virus Other STIs
Oppelt et al. 2010
PCR Endometriosis lesions
Tissue-matched controls
Endometriosis tissue samples, 11.3%
Control tissue samples,*27.5%
No association No association
Heidarpour et al. 2017
PCR Formalin-fixed, paraffin-embedded ovarian tissue Endometriosis tissue samples, 26.0%
Control tissue samples, 10.2%
No data No data
Rocha et al. 2019
PCR Vaginal, cervical, endometrial, ovarian, uterine tube
lavage and peritoneal fluid
Endometriosis patients, 82.8%
Control patients, 38.7%
No association No association
Vestergaard et al. 2010
PCR Endometrial tissue
Endometriosis lesions
Endometriosis patients, 3.2%
Control patients, 10.0%
Endometriosis patients, 6.3%
Controls, 0%
No association
ID, identification; PCR, polymerase chain reaction; STI, sexually transmitted infection.
*Control tissue samples originate from tissue with a healthy appearance in patients with endometriosis.
7ª2019 Royal College of Obstetricians and Gynaecologists
Endometriosis and the microbiome
Strengths and limitations
This study presents the first systematic review of the lit-
erature that compares the microbiome of mammalian
hosts with and without endometriosis. The majority of
the studies included focus on humans with laparoscopic
documentation of endometriosis presence or absence,
which is essential when comparing the composition
between groups. This study presents a thorough summary
of the included studies’ findings and methodologies,
which are heterogeneous and can be challenging to
review individually. There are limitations to the review
itself. It is possible that there may be additional studies
that were not identified. We found only 18 eligible stud-
ies, many of which are of poor to moderate quality or
have an unclear risk of bias. The scarcity of the literature
resulted in some reliance on animal studies, which carry
their own limitations.
Animal model studies
The development of endometriosis in non-human primate
models is rare and slowly progresses, providing a small
sample size as seen in Bailey and Coe.
One of the major
limitations of mice models is that they do not menstruate
and therefore require the surgical induction of endometrio-
sis. Each of the mice studies included used the homologous
method (involving the transfer of tissue from the same ani-
mal); however, there are variations among them, which
may introduce some bias.
Human studies
The use of the conventional culturing and colony count
method prevents the detection of microbial communities
that are unculturable or low in abundance.
There are also
some limitations of 16S rRNA amplicon sequencing,
including the risk of amplification bias. Additionally,
amplicon sequencing provides a broad, low-resolution view
of the microbial communities present in a sample, in com-
parison to metagenomic sequencing.
Finally, it is impor-
tant to consider the hypervariable region used for
sequencing, as there is some evidence to suggest that the
V1/V2 region is not reliable in accurately representing the
microbial communities present in the female genital tract.
Moreover, there are several sample-specific limitations
with these studies that include, but are not limited to,
small sample size, representation of the cases to reflect a
true patient population, definition and selection of controls
(which often included other pathologies, which may act as
confounders for microbiome findings), other population
confounders such as time-point in menstrual cycle, use of
hormonal medications, and administration of antibiotics or
probiotics. These not only create additional heterogeneity
between studies, but also call into question the validity of
the results.
The microbiome may be involved in the pathogenesis of
A dysfunctional immune response appears to have a signifi-
cant role and there is some evidence to suggest that the
microbiome may modulate the immune response in
endometriosis. The bacterial contamination hypothesis sug-
gests that microbial pathogens activate the immune response
by binding with Toll-like receptors.
Lipopolysaccharide is a
bacterial endotoxin and marker of inflammation found in the
cell wall of Gram-negative bacteria, which has been shown to
promote the onset and progression of endometriosis lesions
via binding with Toll-like receptor 4.
Eight studies
detected taxa belonging to the phylum Proteobacteria that
were significantly increased in endometriosis cohorts.
Interestingly, this phylum is characterised by
Gram-negative staining, and hence lipopolysaccharide.
It is
unclear whether bacterial contamination occurs via direct
migration from the vagina into the uterine cavity. However,
four studies included in this review reported the prevalence of
microbial communities along the reproductive tract in women
with endometriosis.
Along the lines of inflammatory
markers, Campos et al.
identified an association between
Mycoplasma genitalium and interferon-cand interleukin-1b,
though there was no significant difference in microbial taxa
between endometriosis and control groups. No other studies
demonstrated associations between inflammatory markers and
microbiota. Finally, a recent study found that administration
of metronidazole to an endometriotic mouse model resulted
in a reduction in the volume of ectopic lesions as well as the
magnitude of the inflammatory response.
Endometriosis and ethnicity
It has been reported that ethnicity and geographical loca-
tion have a large impact on the taxonomic composition of
microbial communities. However, it is unclear whether the
impact of ethnicity is due to genetic variability, or is the
result of cultural practices.
A meta-analysis of the influ-
ence of race and ethnicity on the prevalence of
endometriosis found that in comparison with white
women, black women are less likely to be diagnosed with
endometriosis, but Asian women are more likely to receive
a diagnosis.
Interestingly, all human studies that demon-
strated significantly different microbiota between women
with endometriosis and those without originated from
Asian countries (Japan, China, Turkey).
The microbiome as a non-invasive diagnostic tool
The lack of non-invasive diagnostic tools continues to be a
major dilemma in the diagnosis of endometriosis.
Though we must exert caution to not overestimate the
value of the differences in the microbiome that have been
8ª2019 Royal College of Obstetricians and Gynaecologists
Leonardi et al.
summarised in this review, there is perhaps potential for
the establishment of a specific microbial signature to aid in
the non-invasive diagnostic process, especially for those
with isolated superficial endometriosis. In particular, Khan
et al.
reported a significant increase in the levels of E. coli
in the menstrual blood of women with ovarian endometri-
omas and superficial peritoneal lesions, when compared
with women with ovarian endometriomas alone. However,
the limitations stated above highlight the importance of
future studies also taking into account patient and environ-
mental confounders on the microbiome, so that we may
know how to interpret tests optimally.
The microbiome and estrogen metabolism
Endometriosis is an estrogen-dominant condition.
the gut microbiome exists the ‘estrobolome’, which encap-
sulates the enteric microbial genes whose products have the
capacity to metabolise estrogens in the gut.
The secretion
of b-glucuronidase and b-glucosidases by enteric bacteria
promotes the deconjugation of estrogen, which may there-
fore increase reabsorption of free estrogens, resulting in
higher circulating levels.
An analysis of microbial gen-
omes found that multiple genera within the gut micro-
biome encode for b-glucuronidase production, including
Bacteroides,Bifidobacterium,Escherichia and Lactobacillus.
Notably, levels of the genus Escherichia were reported to be
significantly higher in the stools of endometriosis patients,
compared with controls in one study included in this
The role of the ‘estrobolome’ and b-glu-
curonidase-secreting bacteria in endometriosis is currently
unknown. However, it is suggested that a dysbiotic gut
microbiome that promotes the deconjugation of estrogens
resulting in increased circulating levels may contribute to a
hyper-estrogenic environment which promotes the progres-
sion of endometriosis.
Further studies investigating b-glu-
curonidase activity in women with endometriosis are
required to determine the role of the ‘estrobolome’ in
Future directions
Recent advances in multiomic technology have enabled
comprehensive analysis of microbial communities. Ampli-
con sequencing, shotgun metagenomic sequencing and
next-generation RNA sequencing are powerful tools that
have resulted in a greater understanding of the human
The use of next-generation RNA sequencing
would be beneficial to detect changes in the expression of
microbial genes and enable the discovery of the functional
From a clinical perspective, assessment of the
microbiome of the gut and female reproductive tract in
humans over a period of time, with and without interven-
tion for endometriosis, is recommended. Considering that
there is a mindset that patients with endometriosis have
various phenotypes (superficial, ovarian and deep
may have different prevalence based on
and sometimes present quite differently clini-
cally (e.g. pain-related complaints versus infertility), micro-
biome findings could be stratified to decipher whether
there are any differences between these groups. Another
concept that warrants further exploration is the relation-
ship between the microbiota and specific inflammatory
markers that are elevated in patients with endometriosis.
The complex bidirectional relationship between the micro-
biome and endometriosis has begun to be characterised by
the studies highlighted in this systematic review. Laboratory
and clinical studies demonstrate that there are indeed dif-
ferences in the microbiome composition of hosts with and
without endometriosis. Additional, methodologically sound
translational studies are needed to further our understand-
ing of the interactions of endometriosis and the host
Disclosure of interests
None declared. Completed disclosure of interest forms are
available to view online as supporting information.
Contribution to authorship
ML, CH, FE-A, EE-O and GC wrote the protocol; ML
provided the search; ML and GC independently screened
and selected eligible studies, and CH extracted data. Dif-
ferences of opinion were registered and resolved by con-
sensus between ML and GC. ML, CH, FE-A, EE-O and
GC took part in interpretation of the data and writing
of the review.
Details of ethics approval
Supporting Information
Additional supporting information may be found online in
the Supporting Information section at the end of the arti-
Figure S1. Flow diagram for study selection.
Table S1. Characteristics of studies included in the sys-
tematic review.
Table S2. Excluded studies.
9ª2019 Royal College of Obstetricians and Gynaecologists
Endometriosis and the microbiome
Table S3. (A) Risk of bias assessment (NewcastleOttawa
Quality Assessment Scale criteria) for human and rhesus
monkey studies. (B) Risk of bias assessment [SYstematic
Review Centre for Laboratory animal Experimentation
(SYRCLE)] for laboratory mice studies.
Table S4. Frequency of anatomical site/source assessment
in systematic review included studies.
Appendix S1. Search strategy.&
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11ª2019 Royal College of Obstetricians and Gynaecologists
Endometriosis and the microbiome
... Endometriotic lesions are estrogen-dependent (192) and growth factors, inflammasomes, and pro-inflammatory cytokines contribute to an inflammatory peritoneal microenvironment which promotes the growth of endometriotic lesions (193). To further complicate our understanding of the pathophysiology of endometriosis, there is some evidence supporting a bidirectional relationship between endometriosis and the human microbiomes (194). ...
... /frph. . microbiome locations seems to be associated with endometriosis (194). Several studies profiled the FRT microbiotas in women with endometriosis and demonstrated differences vs. control groups. ...
... Furthermore, patients with gynecologic conditions including endometriosis and PCOS often experience infertility. Both conditions are associated with increased presence of pathogenic microbial species throughout the FRT (6, 194,220). An interesting avenue for future research would be to investigate differences in FRT composition among women with gynecologic disease, in association with prospective infertility and reproductive outcomes in the same population. ...
Full-text available
The intricate interactions between the host cells, bacteria, and immune components that reside in the female reproductive tract (FRT) are essential in maintaining reproductive tract homeostasis. Much of our current knowledge surrounding the FRT microbiota relates to the vaginal microbiota, where ‘health’ has long been associated with low bacterial diversity and Lactobacillus dominance. This concept has recently been challenged as women can have a diverse vaginal microbial composition in the absence of symptomatic disease. The structures of the upper FRT (the endocervix, uterus, Fallopian tubes, and ovaries) have distinct, lower biomass microbiotas than the vagina; however, the existence of permanent microbiotas at these sites is disputed. During homeostasis, a balance exists between the FRT bacteria and the immune system that maintains immune quiescence. Alterations in the bacteria, immune system, or local environment may result in perturbances to the FRT microbiota, defined as dysbiosis. The inflammatory signature of a perturbed or “dysbiotic” FRT microbiota is characterized by elevated concentrations of pro-inflammatory cytokines in cervical and vaginal fluid. It appears that vaginal homeostasis can be disrupted by two different mechanisms: first, a shift toward increased bacterial diversity can trigger vaginal inflammation, and second, local immunity is altered in some manner, which disrupts the microbiota in response to an environmental change. FRT dysbiosis can have negative effects on reproductive health. This review will examine the increasing evidence for the involvement of the FRT microbiotas and inflammation in gynecologic conditions such as endometriosis, infertility, and endometrial and ovarian cancer; however, the precise mechanisms by which bacteria are involved in these conditions remains speculative at present. While only in their infancy, the use of antibiotics and probiotics to therapeutically alter the FRT microbiota is being studied and is discussed herein. Our current understanding of the intimate relationship between immunity and the FRT microbiota is in its early days, and more research is needed to deepen our mechanistic understanding of this relationship and to assess how our present knowledge can be harnessed to assist in diagnosis and treatment of gynecologic conditions.
... Study participants may be targeting this biological system for various reasons. The rationale for addressing gastrointestinal involvement in endometriosis may relate to the immunomodulation and inflammatory process known within the microbiome [45] and addressing abdominal symptoms (such as bloating and irritable bowel syndrome) [46,47]. From a naturopathic perspective supporting the gastrointestinal system may also promote oestrogen clearance by reducing the reabsorption of deconjugated oestrogen [48]. ...
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Objectives Endometriosis is a chronic gynaecological disease with varying symptomatology and negative health outcomes. To ensure the best care for women with endometriosis, women require a multidisciplinary team approach. While some women consult with naturopaths for endometriosis, there has been little research on naturopathic knowledge and the naturopathic approach to endometriosis care. Methods This cross-sectional survey recruited naturopaths with experience in menstrual disorders from the Practitioner Research and Collaboration Initiative (PRACI) a Practice-Based Research Network (PBRN). Data collection was conducted via an online self-administrated 62-item questionnaire. Results Invitations were sent to 109 naturopaths who self-reported having experience in menstrual disorders, of whom 29 completed the survey (26.6% response rate). Naturopaths perceived endometriosis to be caused by inflammation (n=28, 96.5%) and risk factors associated with familial history (n=26, 89.6%). Many naturopaths aimed at reducing inflammation (n=27, 93.1%) and supporting gastrointestinal function (n=25, 86.2%) in their prescriptions. Naturopaths reported using various healthcare referrals to support women with endometriosis, primarily general practitioners (n=12, 41.3%), acupuncturists/Traditional Chinese Medicine practitioners (n=11, 37.9%), and gynaecologists (n=9, 31%). Naturopaths reported receiving referrals from general practitioners (n=8, 27.5%) and psychologists (n=6, 20.6%). Conclusions Naturopathic knowledge and management of endometriosis targets known problematic areas of endometriosis that can have debilitating effects on women’s quality of life. Naturopathic care has the potential to align with important health outcomes for women with endometriosis however, further attention is needed to assess the effectiveness and continue to establish a multidisciplinary approach involving naturopathic care.
... However, microbiomal studies have also investigated swabs collected from sites known to have significant bacterial colonization, such as the vagina or rectum (Chen et al. 2017. Previous reviews (Leonardi et al. 2020, D'Alterio et al. 2021) have sought to investigate the association between endometriosis and the microbiome from different locations. For this systematic review, we considered microbiome analyses of swabs collected from all potential anatomical sites, regardless of whether the site was locally affected by endometriosis, and also sought to comprehensively collect data on endometriosis stage, menstrual phase, hormonal intake, and endometriosis symptoms. ...
Full-text available
The objective of this study was to systematically review the literature on the human microbiome in association with endometriosis. PubMed/Medline, Cochrane, and Embase databases were searched for literature published from 1986 to August 2021. All human studies that assessed the microbiome using 16S rRNA sequencing or shotgun sequencing in women with endometriosis were included. Two reviewers independently abstracted data from the selected articles into tables. To assess the quality of included studies, the National Institutes of Health Study Quality Assessment Tools were utilized. This review included 12 case–control studies. Included studies compared the microbiome from various anatomical sources (fecal, vaginal, cervical, peritoneal, endometrial, and intra-lesional) between patients with endometriosis and a heterogeneous set of control patients. Study quality ranged from poor to good, with 8 of 12 studies rated fair. Multiple studies reported a different distribution of bacteria among women with endometriosis across anatomical sites, but the results were highly heterogeneous. Pseudomonas was overrepresented in peritoneal fluid among women with endometriosis across multiple studies but was also observed to be increased in vaginal, endometrial, and intra-lesional samples. Among bacteria noted across different anatomical samples, Gardnerella was found to be increased in cervical but decreased in endometrial, fecal, and vaginal samples of patients with endometriosis, while Atopium was found to be decreased in vaginal and cervical samples from patients with endometriosis. Sphingobium was found to be increased in vagina, endometrium, and peritoneal fluid from patients with endometriosis. Streptococcus was found to be increased in peritoneal, endometrial, and cervical samples from women with endometriosis. Microbiomal comparisons stratified by endometriosis stage or site of endometriosis involvement were limited and highly heterogeneous.
Full-text available
Endometriosis is a common gynecological disease, that often leads to pain and infertility. At present, the specific pathogenesis of endometriosis has not been clarified, but it may be closely related to an imbalance of sex hormones in the body, ectopic hyperplasia stimulated by immune inflammation, and invasion and escape based on tumor characteristics. Gut microbiota is associated with many inflammatory diseases. With the further study of the gut microbiota, people are paying increasing attention to its relationship with endometriosis. Studies have shown that there is an association between the gut microbiota and endometriosis. The specific ways and mechanisms by which the gut microbiota participates in endometriosis may involve estrogen, immune inflammation, and tumor characteristics, among others. Therefore, in the future, regulating gut microbiota disorders in various ways can help in the treatment of endometriosis patients. This study reviewed the research on the gut microbiota and endometriosis in order to provide ideas for clinical diagnosis and treatment.
In recent years, the function of human umbilical cord mesenchymal stem cell-originated extracellular vesicles (hUC-MSC-EVs) on endometriosis has been reported, while its specific mechanisms remain largely unknown. This study aimed at investigating the mechanisms underlying the modulation of EVs harboring miR-100 derived from hUC-MSCs in the growth dynamics of endometrial stromal cells in endometriosis. Endometriosis mouse models were established. miR-100 was upregulated and HS3ST2 was downregulated in endometriosis. Ectopic endometrial tissues and umbilical cord tissues were obtained to extract endometrial stromal cells and hUC-MSCs, from which EVs were isolated. Next, the endometrial stromal cells were co-cultured with hUC-MSC-EVs, during which gain- or loss-of-function approaches were employed for gene overexpression or silencing. The binding affinity among miR-100 and HS3ST2 was identified using multiple assays. It was unveiled that miR-100 could target and inhibit HS3ST2. miR-100 from hUC-MSCs could be transferred into the endometrial stromal cells via EVs. Moreover, miR-100 shuttled by hUC-MSC-EVs facilitated endometrial stromal cell proliferation, invasion, and migration, as well as EMT by inhibiting HS3ST2. In vivo experiments also confirmed that hUC-MSC-derived EVs carrying miR-100 induced the occurrence and development of endometriosis. Collectively, hUC-MSC-EV-loaded miR-100 downregulated HS3ST2 to facilitate the development of endometriosis, which highlights a promising therapeutic target for treating endometriosis.
Despite advances in treatment strategies, breast cancer remains one of the most prevalent cancers worldwide. Recent studies implicate the gut microbiome as a potential risk factor for breast cancer development. Alterations in gut microbial diversity resulting in dysbiosis have been linked to breast carcinogenesis by modulating host immune responses and inflammatory pathways, favoring tumorigenesis and progression. Moreover, gut microbiota populations are different between women with breast cancer versus those that are cancer-free, further implicating the role of the gut microbiome in cancer development. This alteration in gut microbiota is also associated with changes in estrogen metabolism, which strongly correlates with breast cancer development. Gut microbiota that expresses the enzyme β-glucuronidase (GUS) may increase estrogen bioavailability by deconjugating estrogen-glucuronide moieties enabling reabsorption into circulation. Increased circulating estrogens may, in turn, drive estrogen receptor-positive breast cancer. GUS-expressing microbiota also impact cancer therapy efficacy and toxicity by modifying glucuronide-conjugated drug metabolites. Therefore, GUS inhibitors have emerged as a potential anti-tumor treatment. However, the effectiveness of GUS inhibitors is still exploratory. Further studies are needed to determine how oral endocrine targeting therapies may influence or be influenced by the microbiota and how that may impact carcinogenesis initiation and tumor recurrence.
The surfaces of human internal organs are lined by a mucus layer that ensures symbiotic relationships with commensal microbiome while protecting against potentially injurious environmental chemicals, toxins, and pathogens, and disruption of this layer can contribute to disease development. Studying mucus biology has been challenging due to the lack of physiologically relevant human in vitro models. Here we review recent progress that has been made in the development of human organ-on-a-chip microfluidic culture models that reconstitute epithelial tissue barriers and physiologically relevant mucus layers with a focus on lung, colon, small intestine, cervix and vagina. These organ-on-a-chip models that incorporate dynamic fluid flow, air-liquid interfaces, and physiologically relevant mechanical cues can be used to study mucus composition, mechanics, and structure, as well as investigate its contributions to human health and disease with a level of biomimicry not possible in the past.
Is there a relationship between endometriosis and placenta previa (PP)? To investigate if there is a relationship between endometriosis and PP, a retrospective study was carried out, using prospectively recorded data from two different databases from Cruces University Hospital. Two different populations were included in the study. The ART (assisted reproduction techniques) population consisted of 246 cesarean sections (CS), from a total of 1170 deliveries, and the obstetric population consisted of 7045 CS, from a total of 50,298 deliveries. A representative subset from the obstetric population was established selecting 4 CS without PP for each CS with PP. In our ART population, the PP rate was 1.71% among all deliveries and 8.13% among CS. In our general obstetric population, the PP rate was 0.34% among all deliveries and 2.41% among the CS. Among the CS in ART pregnancies, the PP rate was 20% in the women with endometriosis vs 5.47% in women without endometriosis (OR = 4.32; 95% CI = 1.67–11.17), while considering all ART deliveries, the PP rates were 6.43% and 1.07%, respectively (OR = 6.36; 95% CI = 2.59–15.65). In the CS-obstetric population, the rate of PP was 9.61% among women with endometriosis vs 2.19% among women without endometriosis (OR = 4.74; 95% CI = 2.91–7.73). Considering all deliveries, the PP rate was 1.35% among women with endometriosis vs 0.30% in women without endometriosis. Differences persisted when adjusting for age, IVF, multiplicity, and previous deliveries. In the CS-obstetric population with PP, mean surgical time and hospital stay were significantly higher in women with endometriosis. Endometriosis is associated with a higher risk of PP even after adjusting for other parameters.
Introduction Women with endometriosis are commonly dissatisfied with the standard treatments available and, as such, novel treatment options for endometriosis care needs to be explored. Women with endometriosis are known to seek care from naturopaths to assist in disease management. However, there is limited evidence on the types of treatments naturopaths employ when providing care to women with endometriosis. Methods This cross-sectional survey describes the naturopathic treatments utilised to manage endometriosis and the perceived effectiveness of those treatments. Naturopaths who self-identified as having experience in women's reproductive diseases were invited to participate in the survey (n=109). Participants were recruited from the Practitioner Research and Collaboration Initiative (PRACI), a Practice-Based Research Network (PBRN). Data was collected via an online 62-item survey. Results A total of 29 Australian naturopaths completed the survey (response rate = 26.6%). Participants reported frequently utilising lifestyle recommendations (75.8%), herbal medicines (72.4%), clinical nutritional medicines (72.4%), and dietary recommendations (68.9%). The most frequently prescribed treatments included essential fatty acids (65.5%), exercise (62%), magnesium (55.1%), and Curcuma longa (Turmeric) (48.2%). Respondents who reported prescribing these treatments frequently perceived them to be effective, with the highest level of perceived effectiveness reported for Curcuma longa (Turmeric) (48.2%) and magnesium (44.8%). Conclusions Naturopaths appear to employ various treatments and report varied perceived effectiveness of those treatments in the management of endometriosis. Clinical research is needed to evaluate the clinician experience and verify the potential value of naturopathic treatments in improving the symptoms and quality of life of women with endometriosis.
The impact of coronavirus disease 2019 (COVID-19) on endometriosis (EM) is currently unclear. Here, we aimed to describe the potential influence of COVID-19 on the pathogenesis, clinical symptoms, and treatment of EM. The cytokine storm caused by COVID-19 may induce the occurrence and progression of EM, and immunosuppression of COVID-19 may help the ectopic endometrium escape from immune clearance. Consequently, the forced social isolation and the cancelation of non-emergency medical treatment during the COVID-19 pandemic aggravate anxiety and psychological pressure, which can aggravate the symptoms related to EM and delay routine medical services. © Copyright 2022 Reproductive and Developmental Medicine, Published by Wolters Kluwer Health, Inc.
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Background: Understanding the impact of race/ethnicity on the prevalence and presentation of endometriosis may help improve patient care. Objective: To review systematically the evidence for the influence of race/ethnicity on the prevalence of endometriosis. Search strategy: CENTRAL, MEDLINE, PubMed, Embase, LILACS, SCIELO, and CINAHL databases, as well as the grey literature, were searched from date of inception until September 2017. Selection criteria: Randomised control trials and observational studies reporting on prevalence and/or clinical presentation of endometriosis. Data collection and analysis: Twenty studies were included in the review and 18 studies were used to calculate odds ratio (OR) with 95% confidence interval (CI) through a random effects model. Methodological quality was assessed using the Newcastle-Ottawa risk of bias scale (NOS). Main results: Compared with White women, Black woman were less likely to be diagnosed with endometriosis (OR 0.49, 95% CI 0.29-0.83), whereas Asian women were more likely to have this diagnosis (OR 1.63, 95% CI 1.03-2.58). Compared with White women, there was a statistically significant difference in likelihood of endometriosis diagnosis in Hispanic women (OR 0.46, 95% CI 0.14-1.50). Significant heterogeneity (I2 > 50%) was present in the analysis for all racial/ethnic groups but was partially reduced in subgroup analysis by clinical presentation, particularly when endometriosis was diagnosed as self-reported, CONCLUSIONS: Prevalence of endometriosis appears to be influenced by race/ethnicity. Most notably, Black women appear less likely to be diagnosed with endometriosis compared with White women. There is scarce literature exploring the influence of race/ethnicity on symptomatology, as well as treatment access, preference, and response. Tweetable abstract: Prevalence of endometriosis may be influenced by race/ethnicity, but there is limited quality literature exploring this topic.
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Dysbiosis in the genital tract or gut microbiome can be associated with endometriosis. We sampled vaginal, cervical and gut microbiota from 14 women with histology proven stage 3/4 endometriosis and 14 healthy controls. The V3 and V4 regions of the 16S rRNA gene were amplified following the 16S Metagenomic Sequencing Library Preparation. Despite overall similar vaginal, cervical and intestinal microbiota composition between stage 3/4 endometriosis group and controls, we observed differences at genus level. The complete absence of Atopobium in the vaginal and cervical microbiota of the stage 3/4 endometriosis group was noteworthy. In the cervical microbiota, Gardnerella, Streptococcus, Escherichia, Shigella, and Ureoplasma, all of which contain potentially pathogenic species, were increased in stage 3/4 endometriosis. More women in the stage 3/4 endometriosis group had Shigella/Escherichia dominant stool microbiome. Further studies can clarify whether the association is causal, and whether dysbiosis leads to endometriosis or endometriosis leads to dysbiosis.
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Endometriosis can have a profound impact on women's lives, including associated pain, infertility, decreased quality of life, and interference with daily life, relationships, and livelihood. The first step in alleviating these adverse sequelae is to diagnose the underlying condition. For many women, the journey to endometriosis diagnosis is long and fraught with barriers and misdiagnoses. Inherent challenges include a gold standard based on an invasive surgical procedure (laparoscopy) and diverse symptomatology, contributing to the well-established delay of 4–11 years from first symptom onset to surgical diagnosis. We believe that remedying the diagnostic delay requires increased patient education and timely referral to a women's healthcare provider and a shift in physician approach to the disorder. Endometriosis should be approached as a chronic, systemic, inflammatory, and heterogeneous disease that presents with symptoms of pelvic pain and/or infertility, rather than focusing primarily on surgical findings and pelvic lesions. Using this approach, symptoms, signs, and clinical findings of endometriosis are anticipated to become the main drivers of clinical diagnosis and earlier intervention. Combining these factors into a practical algorithm is expected to simplify endometriosis diagnosis and make the process accessible to more clinicians and patients, culminating in earlier effective management. The time has come to bridge disparities and to minimize delays in endometriosis diagnosis and treatment for the benefit of women worldwide.
Problem Intrauterine microbial colonization and its association with the pathogenesis of endometriosis via an innate immune cascade have been reported. As a potential source of microbial transmission, information on microbial colonization in cervical mucus is unknown. We investigated pattern of microbiota in the cervical mucus collected from women with and without endometriosis using next‐generation sequencing (NGS) technology. Method of Study Cervical mucus samples were collected from women with (n = 30) and without (n = 39) endometriosis. The communities of microbiota in cervical mucus in the endometriosis group and the control group were examined by Gram staining and NGS targeting the V5‐V6 region of 16S ribosomal RNA gene. Copy number of some target bacteria was detected by real‐time PCR. Results We confirmed visual presence of bacteria in cervical mucus by Gram staining. NGS analysis showed that distribution of microbiota was similar in cervical mucus of women with and without endometriosis regardless of the phases of the menstrual cycle. In addition to predominant Lactobacilli spp. the populations of Corynebacterium, Enterobacteriaceae, Flavobacterium, Pseudomonas, and Streptococcus were increased in the endometriosis group. Of them, Enterobacteriaceae and Streptococcus were identified as the more significant candidates in the endometriosis group than in controls by real‐time PCR (P < 0.05 for each). Conclusions Our NGS analysis of cervical mucus indicated that among a variable microbiota, two candidates (Enterobacteriaceae and Streptococcus) were more frequently detected in women with endometriosis. Further investigation is needed to elucidate a mechanistic link of these bacteria in the pathophysiology of endometriosis. This article is protected by copyright. All rights reserved.
STUDY QUESTION: Does altering gut microbiota with antibiotic treatment have any impact on endometriosis progression? SUMMARY ANSWER: Antibiotic therapy reduces endometriosis progression in mice, possibly by reducing specific gut bacteria. WHAT IS KNOWN ALREADY: Endometriosis, a chronic condition causing abdominal pain and infertility, afflicts up to 10% of women between the ages of 25 and 40, ~5 million women in the USA. Current treatment strategies, including hormone therapy and surgery, have significant side effects and do not prevent recurrences. We have little understanding of why some women develop endometriosis and others do not. STUDY DESIGN, SIZE, DURATION: Mice were treated with broad-spectrum antibiotics or metronidazole, subjected to surgically induced endometriosis and assayed after 21 days. PARTICIPANTS/MATERIALS, SETTING, METHODS: The volumes and weights of endometriotic lesions and histological signatures were analysed. Proliferation and inflammation in lesions were assessed by counting cells that were positive for the proliferation marker Ki-67 and the macrophage marker Iba1, respectively. Differences in faecal bacterial composition were assessed in mice with and without endometriosis, and faecal microbiota transfer studies were performed. MAIN RESULTS AND THE ROLE OF CHANCE: In mice treated with broad-spectrum antibiotics (vancomycin, neomycin, metronidazole and ampicillin), endometriotic lesions were significantly smaller (~ 5-fold; P < 0.01) with fewer proliferating cells (P < 0.001) than those in mice treated with vehicle. Additionally, inflammatory responses, as measured by the macrophage marker Iba1 in lesions and IL-1β, TNF-α, IL-6 and TGF-β1 in peritoneal fluid, were significantly reduced in mice treated with broad-spectrum antibiotics (P < 0.05). In mice treated with metronidazole only, but not in those treated with neomycin, ectopic lesions were significantly (P < 0.001) smaller in volume than those from vehicle-treated mice. Finally, oral gavage of faeces from mice with endometriosis restored the endometriotic lesion growth and inflammation (P < 0.05 and P < 0.01, respectively) in metronidazole-treated mice. LARGE-SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: These findings are from a mouse model of surgically-induced endometriosis. Further studies are needed to determine the mechanism by which gut bacteria promote inflammation, identify bacterial genera or species that promote disease progression and assess the translatability of these findings to humans.
Purpose: The aims of this study were to clarify the effects of lipopolysaccharide (LPS) on the early development of endometriosis and on the production of cytokines and chemokines in the murine peritoneal cavity. Methods: Endometriotic lesions were induced in C57BL/6J adult female mice by intraperitoneal injection of endometrial fragments plus blood or endometrial fragments plus blood with LPS. On day 7, endometriotic lesions were assessed by gross and microscopic evaluations. Time-dependent changes in the secretion of TNF-α,IL-6,and CXCL2/MIP-2 in peritoneal lavage fluid after the intraperitoneal injection of LPS (50 µg/body) were measured by their respective enzyme-linked immunosorbent assays. Results: The areas of endometriotic lesions in the LPS group (10.8 8.6 mm2) were significantly larger than those in the control group (3.1 3.7 mm2).The levels of TNF-α and IL-6 peaked within 2 hours and the level of MIP-2 reached a maximum on day 1 after the injection of LPS. Conclusions: LPS promotes development of the early stages of murine endometriotic lesions. J. Med. Invest. 66 : 70-74, February, 2019.
Research question: Is there an association between the presence of sexually transmitted pathogens in the lower (LGT) and upper (UGT) female genital tract with endometriosis and infertility? Design: Case-control study with 60 women submitted to gynaecological laparoscopic surgery. Samples from the UGT and LGT were collected and analysed by single polymerase chain reaction (PCR) for human papillomavirus (HPV) and by multiplex PCR for other sexually transmitted infections (STI). Patients were initially divided into two clinical groups: infertile patients (n = 25) with conjugal infertility and fertile control patients (n = 35). After the surgical findings patients were further divided for additional analysis: an endometriosis group (n = 29) and non-endometriosis control group (n = 31). Results: Sixty per cent of patients were positive for DNA-HPV in some of the genital tract sites sampled. Infertile patients were associated with high-risk HPV (hrHPV) positivity in the UGT sites (P = 0.027). The endometriosis group was associated with hrHPV positivity in the LGT and UGT sites (P = 0.0002 and P = 0.03, respectively). Only hrHPV types were detected in the UGT in both groups. It may be that there is a hrHPV infection continuum, from LGT to UGT, in infertile and endometriosis patients. No association was observed among the other seven STI studied. Conclusions: This study shows both an association between hrHPV infections in the UGT with infertility and endometriosis, and a possible hrHPV infection continuum, from LGT to UGT. Larger studies are needed to fully investigate the role of hrHPV as a cause of endometriosis and infertility.
The taxonomic composition of the gut microbiome associates with patient ethnicity and geographic location. This association impacts the development of microbiome-based applications for personalized medicine.