Extracellular matrix metalloproteinase inducer expression in the baboon endometrium: menstrual cycle and endometriosis

The Known, the Unknown and the Future of the Pathophysiology of Endometriosis

Endometriosis is one of the most common causes of chronic pelvic pain and infertility, affecting 10% of women of reproductive age. A delay of up to 9 years is estimated between the onset of symptoms and the diagnosis of endometriosis. Endometriosis is currently defined as the presence of endometrial epithelial and stromal cells at ectopic sites; however, advances in research on endometriosis have some authors believing that endometriosis should be re-defined as "a fibrotic condition in which endometrial stroma and epithelium can be identified". There are several theories on the etiology of the disease, but the origin of endometriosis remains unclear. This review addresses the role of microRNAs (miRNAs), which are naturally occurring post-transcriptional regulatory molecules, in endometriotic lesion development, the inflammatory environment within the peritoneal cavity, including the role that cytokines play during the development of the disease, and how animal models have helped in our understanding of the pathology of this enigmatic disease.

Loss of basigin expression in uterine cells leads to subfertility in female mice†

Basigin (BSG) is a transmembrane glycoprotein involved in cell proliferation, angiogenesis, and tissue remodeling. BSG has been shown to be essential for male and female reproduction although little is known about its role in normal uterine function. To study the potential function of BSG in the female reproductive tract, we generated mice with conditional knockout of Bsg in uterine cells using progesterone receptor-Cre and hypothesized that BSG is required for normal pregnancy in mice. Fertility study data showed that the conditional knockout mice had significantly reduced fertility compared to controls. Ovarian function of the conditional knockout mice appeared normal with no difference in the number of superovulated oocytes collected or in serum progesterone levels between the conditional knockout and the control mice. Uterine tissues collected at various times of gestation showed increased abnormalities in implantation, decidualization, placentation, and parturition in the conditional knockout mice. Uterine cross sections on Day 5 of pregnancy showed implantation failure and abnormal uterine epithelial differentiation in a large proportion of the conditional knockout mice. There was a compromised decidual response to artificial decidualization stimuli and decreased mRNA and protein levels for decidualization genes in the uteri of the conditional knockout mice. We also observed altered protein expression of monocarboxylate transporter 1 (MCT1), as well as impaired angiogenesis in the conditional knockout uteri compared to the controls. These results support that BSG is required for successful pregnancy through its functions in implantation and decidualization.

The role of epigenetic mechanisms in the regulation of gene expression in the cyclical endometrium

BACKGROUND

The human endometrium is a highly dynamic tissue whose function is mainly regulated by the ovarian steroid hormones estradiol and progesterone. The serum levels of these and other hormones are associated with three specific phases that compose the endometrial cycle: menstrual, proliferative, and secretory. Throughout this cycle, the endometrium exhibits different transcriptional networks according to the genes expressed in each phase. Epigenetic mechanisms are crucial in the fine-tuning of gene expression to generate such transcriptional networks. The present review aims to provide an overview of current research focused on the epigenetic mechanisms that regulate gene expression in the cyclical endometrium and discuss the technical and clinical perspectives regarding this topic.

MAIN BODY

The main epigenetic mechanisms reported are DNA methylation, histone post-translational modifications, and non-coding RNAs. These epigenetic mechanisms induce the expression of genes associated with transcriptional regulation, endometrial epithelial growth, angiogenesis, and stromal cell proliferation during the proliferative phase. During the secretory phase, epigenetic mechanisms promote the expression of genes associated with hormone response, insulin signaling, decidualization, and embryo implantation. Furthermore, the global content of specific epigenetic modifications and the gene expression of non-coding RNAs and epigenetic modifiers vary according to the menstrual cycle phase. In vitro and cell type-specific studies have demonstrated that epithelial and stromal cells undergo particular epigenetic changes that modulate their transcriptional networks to accomplish their function during decidualization and implantation.

CONCLUSION AND PERSPECTIVES

Epigenetic mechanisms are emerging as key players in regulating transcriptional networks associated with key processes and functions of the cyclical endometrium. Further studies using next-generation sequencing and single-cell technology are warranted to explore the role of other epigenetic mechanisms in each cell type that composes the endometrium throughout the menstrual cycle. The application of this knowledge will definitively provide essential information to understand the pathological mechanisms of endometrial diseases, such as endometriosis and endometrial cancer, and to identify potential therapeutic targets and improve women's health.

Dose-dependent pro- or anti-fibrotic responses of endometriotic stromal cells to interleukin-1β and tumor necrosis factor α

Endometriosis are characterized by dense fibrous tissue. Numerous studies have investigated roles of inflammation on the pathophysiology of endometriosis. However, the interplay of inflammation and fibrosis remains to be clarified. Here we show that low levels of interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNFα) promoted a fibrotic phenotype, whereas high levels of IL-1β and TNFα inactivated the fibrotic phenotype of endometriotic stromal cells (Ectopic-ES). IL-1β 10 pg/mL and TNFα 100 and 1,000 pg/mL had minimal effects, whereas the highest dose of IL-1β (100 pg/mL) significantly decreased collagen gel contraction in Ectopic-ES. Furthermore, in Ectopic-ES, low levels of IL-1β (1 pg/mL) and/or TNFα 10 pg/mL significantly increased Col I mRNA expression, whereas higher doses of IL-1β (10 and/or 100 pg/mL) and/or TNFα (100 and/or 1,000 pg/mL) significantly decreased Col I and/or αSMA mRNA expression and the percentage of cells with Col I + and/or αSMA + stress fibers. In contrast, in either menstrual endometrial stromal cells of patients with endometriosis or those of healthy women, varying doses of IL-1β and/or TNFα had no significant effects on either Col I or αSMA mRNA/protein expression. The present findings bring into question whether we should still continue to attempt anti-inflammatory treatment strategies for endometriosis.

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

Altered expression of microRNA-451 in eutopic endometrium of baboons (Papio anubis) with endometriosis

STUDY QUESTION

Are microRNAs (miRs) altered in the eutopic endometrium (EuE) of baboons following the induction of endometriosis?

SUMMARY ANSWER

Induction of endometriosis causes significant changes in the expression of eight miRs, including miR-451, in the baboon endometrium as early as 3 months following induction of the disease.

WHAT IS KNOWN ALREADY

Endometriosis is one of the most common gynecological disorders and causes chronic pelvic pain and infertility in women of reproductive age. Altered expression of miRs has been reported in women and has been suggested to play an important role in the pathophysiology of several gynecological disorders including endometriosis.

STUDY DESIGN, SIZE, DURATION

EuE was obtained from the same group of baboons before and 3 months after the induction of endometriosis. The altered expression of miR-451 was validated in the eutopic and ectopic endometrium of additional baboons between 3 and 15 months following disease induction. Timed endometrial biopsies from women with and without endometriosis were also used to validate the expression of miR-451.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Total RNA was extracted from EuE samples before and after the induction of endometriosis, and miRNA expression was analyzed using a 8 × 15 K miR microarray. Microarray signal data were preprocessed by AgiMiRna software, and an empirical Bayes model was used to estimate the changes. The present study focused on quantitative RT-PCR validation of the microarray data, specifically on miR-451 and its target genes in both baboons (n = 3) and women [control (n = 7) and endometriosis (n = 19)]. Descriptive and correlative analysis of miR-451 and target gene expression was conducted using in situ hybridization and immunohistochemistry, while functional analysis utilized an in vitro 3' untranslated region (UTR) luciferase assay and overexpression of miR-451 in human endometrial and endometriotic cell lines.

MAIN RESULTS AND THE ROLE OF CHANCE

Induction of endometriosis results in the altered expression of miR-451, -141, -29c, -21, -424, -19b, -200a and -181a in the baboon endometrium. In the baboon, induction of endometriosis significantly decreased the expression of miR-451 at 3 months (P < 0.001), which was also associated with increased expression of its target gene YWHAZ (14.3.3ζ). A similar significant (P < 0.0001) decrease in miR-451 expression was observed in women with endometriosis. The 3' UTR luciferase assay confirmed the regulation of YWHAZ expression by miR-451. Furthermore, overexpression of miR-451 in 12Z cells (immortalized human endometriotic epithelial cell line) led to the decreased expression of its target YWHAZ and this was correlated with decreased cell proliferation.

LIMITATIONS, REASONS FOR CAUTION

The study focused only on miR-451 and one of its targets, namely YWHAZ. A single miR could target number of genes and a single gene could also be regulated by number of miRs; hence, it is possible that other miRs and their regulated genes may contribute to the pathophysiology of endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that the presence of ectopic lesions in baboon causes changes in EuE miR expression as early as 3 months postinduction of the disease, and some of these changes may persist throughout the course of the disease. We propose that the marked down-regulation of miR-451 in both baboons and women with endometriosis increases the expression of multiple target genes. Increased expression of one of the target genes, YWHAZ, increases proliferation, likely contributing to the pathophysiology of the disease.

EMMPRIN-mediated induction of uterine and vascular matrix metalloproteinases during pregnancy and in response to estrogen and progesterone

Pregnancy is associated with uteroplacental and vascular remodeling in order to adapt for the growing fetus and the hemodynamic changes in the maternal circulation. We have previously shown upregulation of uterine matrix metalloproteinases (MMPs) during pregnancy. Whether pregnancy-associated changes in MMPs are localized to the uterus or are generalized in feto-placental and maternal circulation is unclear. Also, the mechanisms causing the changes in uteroplacental and vascular MMPs during pregnancy are unclear. MMPs expression, activity and tissue distribution were measured in uterus, placenta and aorta of virgin, mid-pregnant (mid-Preg) and late pregnant (late-Preg) rats. Western blots and gelatin zymography revealed increases in MMP-2 and -9 in uterus and aorta of late-Preg compared with virgin and mid-Preg rats. In contrast, MMP-2 and -9 were decreased in placenta of late-Preg versus mid-Preg rats. Extracellular MMP inducer (EMMPRIN) was increased in uterus and aorta of pregnant rats, but was less in placenta of late-Preg than mid-Preg rats. Prolonged treatment of uterus or aorta of virgin rats with 17β-estradiol and progesterone increased the amount of EMMPRIN, MMP-2 and -9, and the sex hormone-induced increases in MMPs were prevented by EMMPRIN neutralizing antibody. Immunohistochemistry revealed that MMP-2 and -9 and EMMPRIN increased in uterus and aorta of pregnant rats, but decreased in placenta of late-Preg versus mid-Preg rats. Thus pregnancy-associated upregulation of uterine MMPs is paralleled by increased vascular MMPs, and both are mediated by EMMPRIN and induced by estrogen and progesterone, suggesting similar role of MMPs in uterine and vascular tissue remodeling and function during pregnancy. The decreased MMPs and EMMPRIN in placenta of late-Preg rats suggests reduced role of MMPs in feto-placental circulation during late pregnancy.

Induction of endometriosis alters the peripheral and endometrial regulatory T cell population in the non-human primate

BACKGROUND

Endometriosis is a gynecological condition that is characterized by extreme abdominal pain and also decreased fertility. Regulatory T cells (Tregs) have immunosuppressive activity critical for embryonic implantation and likewise the acceptance of tissue engraftment. Utilizing the induced non-human primate (Papio anubis) model of endometriosis, we hypothesize that endometriosis decreases the peripheral and endomet rial Treg profile, whereas ectopic lesions have increased Treg localization.

METHODS

Peripheral blood and endometrium were obtained throughout the menstrual cycle prior to and after induction of disease. Animals were randomly assigned to control (n = 7) or diseased (n = 16) treatment groups. Endometriosis was induced by i.p. injection of autologous menstrual tissue for 2 consecutive months during menses. Peripheral blood and endometrial tissue were collected at d9-11PO at 1, 3, 6, 9, 12 and 15 months post-induction of disease for fluorescence-activated cell sorting, quantitative RT-PCR and immunohistochemistry. Ectopic lesions were excised at 1 and 6 months post-inoculation and also harvested at necropsy (15 months) and processed for RNA of IHC. Identification of Tregs through analysis of FOXP3 expression was conducted utlilizing several methodologies. Differences were determined by non-parametric statistical analysis between all treatment groups and time points.

RESULTS

In control animals, the proportion of peripheral natural Tregs (nTregs) was reduced (P < 0.05) during the mid- and late secretory stages of the menstrual cycle compared with menses. The induction of disease decreased peripheral Treg expression at early time points (P < 0.05) and this remained low throughout the time course, compared with the pre-inoculatory level of an individual. FOXP3 gene expression and Treg populations were also decreased in the eutopic endometrium (P < 0.05) compared with control animals, whereas these parameters were increased in ectopic lesions (P < 0.05), compared with the eutopic endometrium.

CONCLUSIONS

Our data suggest that a reduction in peripheral Tregs may be a causative factor for endometriosis-associated infertility, while the increase in ectopic Treg expression may aid lesion development. Furthermore, endometriosis appears to disrupt Treg recruitment in both eutopic and ectopic endometrium.

Estrogen activates matrix metalloproteinases-2 and -9 to increase beta amyloid degradation

Estrogen is known to affect different aspects of β-amyloid (Aβ) synthesis and degradation. The present work was undertaken to evaluate specifically whether matrix metalloproteinases (MMP) -2 and -9 are involved in Aβ degradation induced by estrogen and whether this is relevant to estrogen-induced neuroprotection. In SH-SY5Y human neuroblastoma cells, 10 nM 17β-estradiol (17β-E2) increases mRNA and intracellular protein expression of MMP-2 and -9, as well as the levels of the active forms of both enzymes released in the medium. Specificity of the effect is proved by prevention with the estrogen receptor (ER) antagonist ICI 182,780 (1 μM) and involvement of the ERα subtype is confirmed by the use of selective ERα or ERβ agonists (PPT, DPN) and antagonists (MPP, PHTPP). 17β-E2 significantly increases the degradation of Aβ, either transferred with the conditioned medium of H4-APPSw human neuroglioma cells, engineered to overproduce Aβ(1-40) and Aβ(1-42), or exogenously added as 2 μM Aβ(1-42). Both these effects are completely prevented by preexposure to the broad spectrum MMP inhibitor GM6001 (5 μM). Importantly, the 17β-E2-induced rescue of neuroblastoma cells challenged with 2 μM Aβ(1-42), an effect prevented by ICI 182,780 (1 μM), is mediated by MMPs, as it appears significantly reduced by GM6001 (5 μM) as well as by both MMP-2 (200 nM) and MMP-9 (200nM) selective inhibitors. In conclusion, the present study shows for the first time that MMP-2 and -9 give a main contribution to estrogen's neuroprotective effect.

Serum sTREM-1 (soluble triggering receptor expressed on myeloid cells-1) associates negatively with embryo quality in infertility patients

PROBLEM

Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is a useful biomarker of infection and inflammation.

METHOD OF STUDY

We studied serum and follicular fluid sTREM-1 in infertile patients (N = 110) utilizing enzyme-linked immunosorbent assay.

RESULTS

Serum and follicular sTREM-1 were in good correlation (Pearson's correlation 0.56, P < 0.0001) with higher values in follicular fluid (140.4 ± 34.4 and 115.6 ± 35.1 pg/mL, t-test, P < 0.0001). Endometriosis associated with lower follicular and serum sTREM-1 compared with male factor infertility patients (age-adjusted r = -25.7 pg/mL, P = 0.018; r = -22.1 pg/mL, P = 0.030). No associations between follicular or serum sTREM-1 and clinical parameters were found, except higher serum sTREM-1 associated with lower embryo quality in all patients (adjusted r = -0.3%, P = 0.033), with a cutoff value between 111.5 and 113.3 pg/mL (OR = 0.38, P = 0.048; OR = 0.34, P = 0.028) predicting that more than 39% of embryos would be with good quality.

CONCLUSION

Serum sTREM-1 could represent a prognostic marker for female fecundity, probably indicating impaired inflammatory reaction of immune system.

Colony-stimulating factor-1 exerts direct effects on the proliferation and invasiveness of endometrial epithelial cells

Although macrophage colony-stimulating factor (CSF-1) has been suggested to play a role in maintaining the chronic inflammatory response in endometriosis, our data suggest that CSF-1 may also play a role in early endometriosis lesion formation. We have shown that CSF-1, in an autocrine fashion, has a direct effect on endometrial epithelial cell proliferation and attachment to peritoneal mesothelial cells, early steps in endometriosis lesion formation on the peritoneum.