Matrix metalloproteinase-9 and tissue inhibitor of matrix metalloproteinase-1: a possible role in the pathogenesis of endometriosis

Relaxed fibronectin: a potential novel target for imaging endometriotic lesions

BACKGROUND

Endometriosis is characterized by the ectopic occurrence of endometrial tissue. Though considered benign, endometriotic lesions possess tumor-like properties such as tissue invasion and remodeling of the extracellular matrix. One major clinical hurdle concerning endometriosis is its diagnosis. The diagnostic modalities ultrasound and MRI are often unable to detect all lesions, and a clear correlation between imaging and clinical symptoms is still controversial. Therefore, it was our aim to identify a potential target to image active endometriotic lesions.

RESULTS

For our studies, we employed the preclinical radiotracer [111In]In-FnBPA5, which specifically binds to relaxed fibronectin-an extracellular matrix protein with key functions in homeostasis that has been implicated in the pathogenesis of diseases such as cancer and fibrosis. We employed this tracer in biodistribution as well as SPECT/CT studies in mice and conducted immunohistochemical stainings on mouse uterine tissue as well as on patient-derived endometriosis tissue. In biodistribution and SPECT/CT studies using the radiotracer [111In]In-FnBPA5, we found that radiotracer uptake in the myometrium varies with the estrous cycle of the mouse, leading to higher uptake of [111In]In-FnBPA5 during estrogen-dependent phases, which indicates an increased abundance of relaxed fibronectin when estrogen levels are high. Finally, immunohistochemical analysis of patient samples demonstrated that there is preferential relaxation of fibronectin in the proximity of the endometriotic stroma.

CONCLUSION

Estrous cycle stages characterized by high estrogen levels result in a higher abundance of relaxed fibronectin in the murine myometrium. This finding together with a first proof-of-concept study employing human endometriosis tissues suggests that relaxed fibronectin could be a potential target for the development of a diagnostic radiotracer targeting endometriotic lesions. With [111In]In-FnBPA5, the matching targeting molecule is in preclinical development.

Expression of laminin-1 and matrix metalloproteinase-9 in benign and malignant endometrium

BACKGROUND

Laminin-1 and matrix metalloproteinase (MMP)-9 may play roles in the progression from benign to malignant endometrium, so we aimed to investigate their levels of expression in these tissues.

METHODS

This case-control study was conducted at a tertiary care center between January 2014 and December 2016. Paraffin blocks of 50 specimens of benign endometrium with proliferative (n = 20), secretory (n = 11), and atrophic (n = 5) endometrium; simple endometrial hyperplasia without atypia (n = 12); and endometrial polyp (n = 2) histology and 49 specimens of malignant endometrium with endometrioid (n = 40), serous (n = 7), clear cell (n = 1), and undifferentiated (n = 1) types were immunostained with laminin-1 and MMP-9 antibodies and assessed for basement membrane continuity for laminin-1 and the percentage and intensity of MMP-9 expression in epithelial cytoplasm.

RESULTS

: Laminin-1 continuity in the basement membrane was higher in benign (92%) compared to malignant (16.3%) endometrium (p < 0.0001) without any difference between the subgroups within each group (p > 0.05). All atrophic endometria and endometrial polyps and 23.5% of low grade endometrioid and none of the other endometrial cancers showed uninterrupted basement membrane staining with laminin-1. All cases in malignant endometrium expressed MMP-9 with either low or high immunoreactivity while none of the cases in benign endometrium showed a high staining with MMP-9 (p < 0.01). Proliferative and hyperplastic endometrium together with grade 1 endometrioid cancer expressed MMP-9 better than the atrophic endometrium (p < 0.05). The immunoreactivity with MMP-9 increased gradually from secretory to hyperplastic endometrium and serous carcinoma (p < 0.05). MMP-9 expression in all types of cancers except grade 1 endometrioid and clear cell compared to proliferative endometrium was significantly higher (p < 0.05) and increased from proliferative to grade 2 endometrioid, grade 3 endometrioid, serous and undifferentiated endometrial carcinoma.

DISCUSSION

Gradual increments in MMP-9 expression and basement membrane laminin-1 discontinuity may indicate progression from normal to hyperplastic and to low- and high-grade cancerous endometrium.

IL-10 is not anti-fibrotic but pro-fibrotic in endometriosis: IL-10 treatment of endometriotic stromal cells in vitro promotes myofibroblast proliferation and collagen type I protein expression

STUDY QUESTION

Is interleukin-10 (IL-10) anti-fibrotic in endometriosis?

SUMMARY ANSWER

IL-10 is not anti-fibrotic but pro-fibrotic in endometriosis, because IL-10 treatment of endometriotic stromal cells in vitro promotes myofibroblast proliferation and collagen type I protein expression.

WHAT IS KNOWN ALREADY

We previously showed that persistent activation of signal transducer and activator of transcription 3 (STAT3) via IL-6 trans-signaling promotes fibrosis of endometriosis. Studies showed marked anti-fibrotic effects of IL-10 via the STAT3 signaling pathway, which is generally considered to be anti-inflammatory, in various organs.

STUDY DESIGN, SIZE, DURATION

Endometrial and/or endometriotic samples of 54 patients who had histological evidence of deep endometriosis, and endometrial samples from 30 healthy fertile women were analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effects of IL-10/STAT3 signaling as well as inhibition of STAT3 activation by knockdown of STAT3 gene on the pro-fibrotic phenotype in endometrial and endometriotic stromal cells in vitro were investigated. Then, the effects of various time points of IL-10 treatment in combination with transforming growth factor (TGF)-β1 and/or IL-6/soluble IL-6 receptor (sIL-6R) on the profibrotic phenotype of endometrial and endometriotic stromal cells were investigated.

MAIN RESULTS AND THE ROLE OF CHANCE

IL-10 induced pro-fibrotic phenotype (cell proliferation, collagen type I synthesis, α-smooth muscle actin positive stress fibers and collagen gel contraction) of endometriotic stromal cells. Knockdown of STAT3 gene decreased the IL-10 induced pro-fibrotic phenotype of endometriotic stromal cells. In contrast, IL-10 had no significant effects on pro-fibrotic phenotype of endometrial stromal cells of healthy women. Sequential IL-10 treatment with or without TGF-β1 and/or IL-6/sIL-6R induced persistent activation of STAT3 and significantly increased proliferation of myofibroblasts (cells with α-smooth muscle actin positive stress fibers) and protein expression of collagen type I in endometriotic stromal cells. TGF-β1 and/or IL-6/sIL6RIL-6/sIL6R treatment significantly increased tissue inhibitor of metalloproteinase 1 (TIMP1) protein expression, whereas IL-10 had no significant effects. Knockdown of STAT3 gene significantly decreased the TGF-β1 and/or IL-6/sIL6R induced TIMP1 protein expression. In contrast, pre-treatment with IL-10 before TGF-β1 and/or IL-6/sIL-6R treatment and sequential IL-10 treatment with or without TGF-β1 and/or IL-6/sIL-6R significantly decreased proliferation of fibroblasts (cells without α-smooth muscle actin positive stress fibers) and collagen type I protein expression in endometrial stromal cells of healthy women.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Given the large number of complex interactions and signaling pathways of pro- and anti-inflammatory mediators that are involved in the pathophysiology of endometriosis, the present study investigated only a very small portion of the whole. Further in vivo studies are required to validate the present findings.

WIDER IMPLICATIONS OF THE FINDINGS

Inflammatory mediators in the pathophysiology of endometriosis have been extensively investigated as potential therapeutic targets. However, the present study showed that anti-inflammatory signals of IL-10 and IL-6 through persistent STAT3 activation may promote endometriosis fibrosis. Therapeutic strategies, such as suppression of 'inflammation', might dysregulate the cross-regulation of 'pro- and anti-inflammatory mediators', leading to detrimental effects in patients with endometriosis, such as fibrosis. To develop new, but not deleterious, therapeutic strategies, studies are required to investigate whether, how and what 'anti-inflammatory mediators' along with pro-inflammatory mediators are involved in individual patients with endometriosis.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported in part by KARL STORZ SE & Co. KG (Tuttlingen, Germany). The authors have no conflict of interest to disclose.

Serum kisspeptin levels in deep-infiltrating, ovarian, and superficial endometriosis: A prospective observational study

The diagnosis of endometriosis may delay for many years due to non-deterministic symptoms and avoiding surgical interventions. Kisspeptins are hormones that interact with endometrial tissue to limit invasions during placentation and various cancers and are suggested to be also associated with endometriosis. This study evaluated if serum kisspeptin levels are associated with the invasion depth in endometriosis. Forty patients between 18 and 45 years of age and admitted to a tertiary-care Obstetrics and Gynecology Department between 2020 and 2021 with a diagnosis of endometriosis, and 40 patients without endometrioma were included in the study. Demographic, obstetric, clinical, and biochemical characteristics were evaluated in patients with superficial (SE) and deep infiltrating (DIE) endometriosis and healthy controls. Twenty patients (50%) had SE, 14 (35%) had DIE, and 22 (55%) had endometrioma in the patient group. Fertility rates were higher among controls, but similar between patients with SE and DIE. CA125 levels were significantly higher in the DIE group. SE and DIE groups had similar kisspeptin values, significantly higher than controls. CA125 and kisspeptin levels were not correlated in study groups. Serum kisspeptin levels were significantly different between endometriosis patients and healthy controls. However, kisspeptin levels were unable to differentiate endometriosis severity. Our results suggest that kisspeptins might play a role in the pathogenesis of endometriosis, which needs further assessment in more comprehensive studies.

Roles of microRNAs in Regulating Apoptosis in the Pathogenesis of Endometriosis

Endometriosis is a gynecologic disorder characterized by the presence of endometrial tissues outside the uterine cavity affecting reproductive-aged women. Previous studies have shown that microRNAs and their target mRNAs are expressed differently in endometriosis, suggesting that this molecule may play a role in the development and persistence of endometriotic lesions. microRNA (miRNA), a small non-coding RNA fragment, regulates cellular functions such as cell proliferation, differentiation, and apoptosis by the post-transcriptional modulation of gene expression. In this review, we focused on the dysregulated miRNAs in women with endometriosis and their roles in the regulation of apoptosis. The dysregulated miRNAs and their target genes in this pathophysiology were highlighted. Circulating miRNAs as potential biomarkers for the diagnosis of endometriosis have also been identified. As shown by various studies, miRNAs were reported to be a potent regulator of gene expression in endometriosis; thus, identifying the dysregulated miRNAs and their target genes could help discover new therapeutic targets for treating this disease. The goal of this review is to draw attention to the functions that miRNAs play in the pathophysiology of endometriosis, particularly those that govern cell death.

Immunoreactivity of Kisspeptin and Kisspeptin Receptor in Eutopic and Ectopic Endometrial Tissue of Women With and Without Endometriosis

Endometriosis is characterized by the presence of ectopic endometrial tissues. Mechanisms of tissue dissemination in endometriosis may be similar to those involved in tumor metastasis. We hypothesize that dysregulation of kisspeptin (KISS1), a metastasis suppressor in endometrial carcinoma, may contribute to the pathogenesis of endometriosis. In this study, we characterized the immunoreactivity of kisspeptin and its receptor, KISS1R, in eutopic and ectopic endometrial tissue of women with and without endometriosis, in proliferative and secretory menstrual cycle phases. Immunohistochemistry was performed using KISS1 and KISS1R antibodies on samples from women with (n = 35) and without (n = 14) endometriosis. Samples from women with endometriosis included eutopic endometrium (n = 20) samples, superficial endometriotic implants (SUP, n = 10) deep infiltrating endometriotic implants (DIE, n = 15), and ovarian endometriomas (OMA, n = 15). Immunoreactivity was quantified using histoscores. KISS1 and KISS1R immunoreactivity was significantly lower in eutopic endometrial stroma of women with versus without endometriosis, regardless of the menstrual cycle phase (P = 0.001 and P = 0.015 respectively). In endometriotic implants, KISS1 levels were significantly lower in both glandular and stromal components of DIE (P < 0.01) and OMA (P < 0.01) compared to SUP. KISS1R immunoreactivity was lower in the glandular component of OMA (P = 0.035) compared to SUP. KISS1 and KISS1R levels are lower in eutopic endometrial stroma from women with versus without endometriosis, consistent with a role for decreased KISS1 expression in the pathogenesis of endometriosis. As deeply invasive lesions showed lower KISS1 levels than superficial lesions, downregulation of KISS1 levels may contribute to implant invasiveness.

The levels of matrix metalloproteinase-9 and neutrophil gelatinase-associated lipocalin in different stages of endometriosis

This study was designed to explore matrix metalloproteinase-9 (MMP-9), neutrophil gelatinase-associated lipocalin (NGAL) levels and MMP-9/NGAL ratio in women with and without endometriosis diagnosed surgically and/or histopathologically. The correlation between biomarkers and the severity of the disease is analysed. The revised American Fertility Society classification system was used to determine the severity of endometriosis. Serum MMP-9 and Ca125, urine NGAL levels were measured in all participants. Serum MMP-9 levels were significantly higher in the study group (n = 60) compared to controls (n = 31) (15.0 pg/mL (6.0-143.0) vs. 12.0 (4.0-18.0), respectively; p=.002). MMP-9 levels were significantly higher in severe endometriosis compared to mild endometriosis subgroups (p<.001). No significant difference was found between NGAL levels in study and control groups (p>.05). The diagnostic value of MMP-9 and NGAL is not superior than CA-125 for endometriosis. Nevertheless, MMP-9 might be a potential predictive marker for advanced stage of the disease. Impact Statement What is already known on this subject? The gold standard diagnostic test for diagnosis of endometriosis is laparoscopy combined with histopathological confirmation of eutopic endometrial glands and/or stroma. Both invasiveness and possible accompanying complications limit the preference regarding the surgical approach. Among non-invasive markers none has been accepted as gold standard neither for diagnosis nor for determining the severity of the disease. MMPs are extracellular endopeptidases, which have a significant role in degradation and remodelling of extracellular matrix for cellular migration and invasion. Among these, MMP-9 has been shown to be higher in eutopic/ectopic endometrial tissue in women with endometriosis and has been suggested to have a role in pathogenesis of endometriosis by promoting invasion of the endometriotic lesions. NGAL is an acute phase protein, which is involved in a variety of physiological and pathophysiological processes. The molecule has also been revealed to correlate with endometriosis pathophysiology through the epithelial-mesenchymal transition process which is the basis for the onset of endometriosis. But also, NGAL which composes a complex with MMP-9 (MMP-9 and NGAL complex), has been shown to protect MMP-9 from autodegradation in vitro which might be a contributing factor for endometriosis pathophysiology. What the results of this study add? MMP-9 cut-off level for prediction of severe endometriosis is a novel finding obtained from this study with acceptable sensitivity and specificity. On the other hand, NGAL seems to have no significant value either for diagnosis of for determining severity of the disease. After all, MMP-9 might be an easy use acceptable biomarker for endometriosis but further studies on larger populations are needed. What the implications are of these findings for clinical practice and/or further research? MMP might be a potential non-invasive predictive marker for advanced stage disease.

The bimodal role of matrix metalloproteinases and their inhibitors in etiology and pathogenesis of endometriosis (Review)

Aberrant regulation of matrix metalloproteinases (MMPs) may be the primary cause of endometrial lesion formation in a group of predisposed women. Prospect for the genuine origin of endometriosis is ongoing, since retrograde menstruation leads to presence of endometrial debris in peritoneal cavity of many women, which do not experience endometriosis. Tissue remodeling is regulated precisely by a balance of MMPs and their inhibitors. Interplay between factors enhancing and suppressing matrix turnover is crucial for cyclic preparation of endometrium for embryo implantation, and endometrial shedding and renewal in physiology of primates. Disorders of the regulation of matrix remodeling leads to augmentation of implantation and invasive growth of ectopic endometrial tissue. Moreover, endometriosis-induced changes in the matrix balance leads to adhesion formation, ovulatory dysfunction and fertility impairment. The review summarizes the current knowledge regarding the regulation of extracellular matrix turnover in the physiology of the endometrial cycle and in the development of endometriosis, as well as the pathophysiology of ovulatory dysfunction in endometriotic women. Therapeutic modalities utilizing modulation of tissue remodeling were discussed.

Elevated phosphatase of regenerating liver 3 (PRL-3) promotes cytoskeleton reorganization, cell migration and invasion in endometrial stromal cells from endometrioma

STUDY QUESTION

Is phosphatase of regenerating liver-3 (PRL-3) associated with increased motility of endometriotic cells from endometrioma?

SUMMARY ANSWER

Elevated PRL-3 promotes cytoskeleton reorganization, cell migration and invasion of endometrial stromal cells (ESCs) from endometrioma.

WHAT IS KNOWN ALREADY

Overexpression of PRL-3 is associated with cancer cell migration, invasion and metastatic phenotype.

STUDY DESIGN, SIZE, DURATION

Primary human ESCs were isolated from eutopic endometrium of women without endometriosis (EuCo, n = 10), with histologically proven endometrioma (EuEM, n = 19) and from the cyst wall of ovarian endometriosis (OvEM, n = 26).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The expression of PRL-3 in ESCs derived from EuCo, EuEM and OvEM at different phases of menstrual cycle were compared. The protein and mRNA levels of PRL-3 were examined by western blot and RT-qPCR, respectively. ESCs from OvEM were transfected with/without short hairpin RNA (shRNA) or small interfering RNA (siRNA). Additionally, a plasmid-mediated delivery system was used to achieve PRL-3 overexpression in ESCs from EuEM. The cellular distribution of F-actin and α-tubulin were examined by immunocytochemistry. Cell motility was evaluated by a transwell migration/invasion assay.

MAIN RESULTS AND THE ROLE OF CHANCE

The protein and mRNA levels of PRL-3 are significantly elevated in ESCs from OvEM compared with EuCo and EuEM. The expression of PRL-3 was not altered between proliferative phase and secretory phase in ESCs from all groups. Knockdown of PRL-3 significantly modified the distribution of F-actin and α-tubulin cytoskeleton, inhibited cell migration and invasion. Endogenous inhibition of PRL-3 attenuated the expression of Ras homolog gene family members A and C (RhoA, RhoC), Rho-associated coiled-coil-containing protein kinase 1 (ROCK1) and matrix metalloproteinase (MMP) 9, but not MMP2 in ESCs from OvEM. Additionally, overexpression of PRL-3 in ESCs from EuEM up-regulates cell migration and invasion, and increases the expression of RhoA, RhoC, ROCK1 and MMP9.

LIMITATIONS, REASONS FOR CAUTION

Lack of in vivo animal studies is the major limitation of our report. Our results should be further confirmed in a larger cohort of patients and extended to include eutopic and ectopic endometrium from patients with peritoneal endometriosis at different stages of the disease.

WIDER IMPLICATIONS OF THE FINDINGS

Our study describes that elevated expression of PRL-3 contributes to the cell motility of ESCs from endometrioma. The results emphasize the importance of metastatic-related factor PRL-3 in the pathogenesis of endometrioma.

STUDY FUNDING/COMPETING INTEREST

This work was supported by National Natural Science Foundation of China (No. 81170546) and Zhejiang Medicine Science and Technology Projects (No. Y13H040003). The authors declare no conflict of interest.

The plasma and peritoneal fluid concentrations of matrix metalloproteinase-9 are elevated in patients with endometriosis

Background

Enzyme matrix metalloproteinase-9 is a member of the matrix metalloproteinase family, which is critical to normal tissue remodelling during embryogenesis and wound healing. In patients with endometriosis, increased expression and activity of matrix metalloproteinase-9 have been observed in ectopic endometrium, but the plasma and peritoneal fluid concentrations of matrix metalloproteinase-9 in patients with endometriosis and their relation to disease severity have not been clear. The aim of the study was to investigate the concentrations of matrix metalloproteinase-9 in plasma and peritoneal fluid of patients with endometriosis.

Methods

A prospective case–control study was conducted in Jinan Military General Hospital between January 2010 and December 2013. Fifty patients with proven endometriosis and 26 endometriosis-free controls were enrolled in this study. Patients with endometriosis were evaluated and divided into moderate/severe endometriosis group (stage I–II, n = 26) and minimal/mild endometriosis group (stage III–IV, n = 24) according to the revised criteria of the American Society for Reproductive Medicine. Blood samples and peritoneal fluid were obtained from both patients and controls. Matrix metalloproteinase-9 was measured using enzyme-linked immunosorbent assay in plasma and peritoneal fluid. The concentration of matrix metalloproteinase-9 between different groups was compared and its correlation to disease severity was analysed.

Results

Plasma and peritoneal fluid concentrations of matrix metalloproteinase-9 in patients with endometriosis were higher than that in controls. In addition, those patients with moderate/severe endometriosis had significantly higher plasma and peritoneal fluid concentrations of matrix metalloproteinase-9 compared to those with minimal/mild endometriosis. Matrix metalloproteinase-9 concentrations in plasma and peritoneal fluid were both positively correlated with severity of endometriosis and plasma matrix metalloproteinase-9 concentrations had a positive correlation with peritoneal fluid matrix metalloproteinase-9 concentrations in patients with endometriosis.

Conclusions

Increased concentrations of plasma and peritoneal fluid concentrations of matrix metalloproteinase-9 appear to be associated with disease severity of endometriosis and may serve as an alternative biomarker to determine disease severity of endometriosis.

The involvement of osteopontin and matrix metalloproteinase- 9 in the migration of endometrial epithelial cells in patients with endometriosis

BACKGROUND

Endometriosis, which shares certain characteristics with cancers, may cause abnormal expression of proteins involved in cell migration. Endometrial epithelial cells (EECs) are believed to play an important role in endometriotic migration. The aim of this study was to investigate the relationship between the expression of osteopontin (OPN) and matrix metalloproteinase-9 (MMP-9) in endometriotic migration.

METHODS

We performed primary culture of EECs and investigated the expression of OPN and MMP-9 in EECs regulated by 17beta-estradiol (E2). OPN-specific siRNA interference was used to down-regulate OPN and to explore the corresponding change in MMP-9 expression. Real-time RT-PCR, western blot analysis and flow cytometry were used to determine the expression levels of OPN and MMP-9. Gelatin zymography was performed to observe the enzymatic activity of MMP-9 in conditioned media. Transwell and wound scratch assays were performed to investigate the migration ability of EECs.

RESULTS

The expression levels of OPN and MMP-9 in normal EECs (NEECs) were inferior to those in EECs from patients with endometriosis (EEECs). The expression levels of OPN and MMP-9 from stage III/IV EEECs and secretory-phase EECs were higher than those of stage I/II EEECs or proliferative-phase EECs. The expression levels of OPN and MMP-9 in EEECs were increased by E2 treatment and remarkably decreased by siRNA interference. Active MMP-9 expression increased with E2 treatment and decreased with siRNA treatment in EEECs compared with the same treatments in NEECs. The migratory abilities of EEECs were enhanced after cells were treated with E2; in contrast, these abilities were reduced by siRNA interference. In NEECs, active MMP-9 and cellular migration abilities were only minimally influenced by E2 and siRNA treatment.

CONCLUSIONS

The present study suggests that the up-regulation of MMP-9 via activation of OPN induced by estrogen may correlate with the migration of endometrial epithelial cells in patients with endometriosis.

Molecular network analysis of endometriosis reveals a role for c-Jun-regulated macrophage activation

Clinical management of endometriosis is limited by the complex relationship between symptom severity, heterogeneous surgical presentation, and variability in clinical outcomes. As a complement to visual classification schemes, molecular profiles of disease activity may improve risk stratification to better inform treatment decisions and identify new approaches to targeted treatment. We use a network analysis of information flow within and between inflammatory cells to discern consensus behaviors characterizing patient subpopulations. Unsupervised multivariate analysis of cytokine profiles quantified by multiplex immunoassays identified a subset of patients with a shared "consensus signature" of 13 elevated cytokines that was associated with common clinical features of endometriosis, but was not observed among patient subpopulations defined by morphologic presentation alone. Enrichment analysis of consensus markers reinforced the primacy of peritoneal macrophage infiltration and activation, which was demonstrably elevated in ex vivo cultures. Although familiar targets of the nuclear factor κB family emerged among overrepresented transcriptional binding sites for consensus markers, our analysis provides evidence for an unexpected contribution from c-Jun, c-Fos, and AP-1 effectors of mitogen-associated kinase signaling. Their crucial involvement in propagation of macrophage-driven inflammatory networks was confirmed via targeted inhibition of upstream kinases. Collectively, these analyses suggest a clinically relevant inflammatory network that may serve as an objective measure for guiding treatment decisions for endometriosis management, and in the future may provide a mechanistic endpoint for assessing efficacy of new agents aimed at curtailing inflammatory mechanisms that drive disease progression.

Extrapelvic endometriosis: a rare entity or an under diagnosed condition?

Endometriosis is a clinical entity characterized by the presence of normal endometrial mucosa abnormally implanted in locations other than the uterine cavity. Endometriosis can be either endopelvic or extrapelvicdepending on the location of endometrial tissue implantation. Despite the rarity of extrapelvic endometriosis, several cases of endometriosis of the gastrointestinal tract, the urinarytract, the upper and lower respiratory system, the diaphragm, the pleura and the pericardium, as well as abdominal scars loci have been reported in the literature. There are several theories about the pathogenesis and the pathophysiology of endometriosis. Depending on the place of endometrial tissue implantation, endometriosis can be expressed with a wide variety of symptoms. The diagnosis of this entity is neither easy nor routine. Many diagnostic methods clinical and laboratory have been used, but none of them is the golden standard. The multipotent localization of endometriosis in combination with the wide range of its clinical expression should raise the clinical suspicion in every woman with periodic symptoms of extrapelvic organs. Finally, the therapeutic approach of this clinical entity is also correlated with the bulk of endometriosis and the locum that it is found. It varies from simple observation, to surgical treatment and treatment with medication as well as a combination of those.

Altered circulating levels of matrix metalloproteinases 2 and 9 and their inhibitors and effect of progesterone supplementation in women with endometriosis undergoing in vitro fertilization

OBJECTIVE

To investigate differences in the activity of matrix metalloproteinases (MMPs) 2 and 9 and their respective tissue inhibitors (TIMPs) in follicular fluid of women with endometriosis, to correlate the findings with IVF outcome, and to examine the therapeutic potential of progesterone supplementation in restoring the fine balance between MMPs and TIMPs.

DESIGN

Prospective case-control clinical study.

SETTING

Infertility clinic and reproductive health research unit.

PATIENT(S)

A total of 340 infertile women undergoing IVF.

INTERVENTION(S)

Natural micronized progesterone capsules were administered for luteal support.

MAIN OUTCOME MEASURE(S)

Association of MMPs 2 and 9 and TIMP-1 with oocyte maturity and embryo development.

RESULT(S)

An abnormal expression of MMP-2, MMP-9, and TIMP-1 with extensive MMP-9/TIMP-1 imbalance in women with endometriosis undergoing IVF was observed. Transforming growth factor β1 plays an important role in these women with possible involvement of Smad-2 and -3 proteins. Progesterone supplementation improves the imbalance in MMP-9/TIMP-1 ratio significantly in women with endometriosis who conceive after IVF.

CONCLUSION(S)

Increase in MMP-2 and -9 and decrease in TIMP-1 expression was associated with poor oocyte and embryo development in women with endometriosis undergoing IVF. MMP-9/TIMP-1 balance was highly affected in these women, and progesterone supplementation appeared to restore this imbalance to a considerable degree.

Multiplexed protease activity assay for low-volume clinical samples using droplet-based microfluidics and its application to endometriosis

As principal degrading enzymes of the extracellular matrix, metalloproteinases (MPs) contribute to various pathologies and represent a family of promising drug targets and biomarker candidates. However, multiple proteases and endogenous inhibitors interact to govern MP activity, often leading to highly context-dependent protease function that unfortunately has impeded associated clinical utility. We present a method for rapidly assessing the activity of multiple specific proteases in small volumes (<20 μL) of complex biological fluids such as clinical samples that are available only in very limited amounts. It uses a droplet-based microfluidic platform that injects the sample into thousands of picoliter-scale droplets from a barcoded droplet library (DL) containing mixtures of unique, moderately selective FRET-based protease substrates and specific inhibitors and monitors hundreds of the reactions thus initiated simultaneously by tracking these droplets. Specific protease activities in the sample are then inferred from the reaction rates using a deconvolution technique, proteolytic activity matrix analysis (PrAMA). Using a nine-member DL with three inhibitors and four FRET substrates, we applied the method to the peritoneal fluid of subjects with and without the invasive disease endometriosis. The results showed clear and physiologically relevant differences with disease, in particular, decreased MMP-2 and ADAM-9 activities.

Increased circulating MMP-2 levels in infertile patients with moderate and severe pelvic endometriosis

The current study compares the levels of matrix metalloproteinase (MMP)-2 and MMP-9 in the follicular fluid (FF) of infertile patients with and without endometriosis submitted to ovarian stimulation for in vitro fertilization and the levels of MMP-2 in the serum of the same patients. We also evaluated whether the severity of endometriosis can influence serum and/or FF concentration of these metalloproteinases. A cross-sectional study was conducted on 30 patients: stage I/II endometriosis (n = 10), stage III/IV endometriosis (n = 10), and control (infertility due to tubal and/or male factor; n = 10). Blood samples for the analysis of MMP-2 levels were obtained during the early follicular phase of the menstrual cycle. The FF samples for the analysis of MMP-2 and MMP-9 were obtained on the day of oocyte retrieval. The concentrations of MMP-2 and MMP-9 were determined by zymography. No intragroup or intergroup difference was observed in MMP-2 or MMP-9 levels in FF. Significantly higher MMP-2 levels were detected in the serum of infertile women with stage III/IV endometriosis compared to women with stage I/II endometriosis. In conclusion, no differences were observed in the follicular levels of MMP-2 and MMP-9 between infertile patients with and without endometriosis. However, the levels of MMP-2 were significantly higher in the serum of infertile women with advanced stages of endometriosis. Taken together, the present results demonstrate that advanced pelvic endometriosis severity is related to higher serum MMP-2 levels but does not influence follicular MMP-2 or MMP-9 levels in periovulatory follicles obtained from stimulated cycles.

Estrogen suppresses expression of the matrix metalloproteinase inhibitor reversion-inducing cysteine-rich protein with Kazal motifs (RECK) within the mouse uterus

RECK (reversion-inducing cysteine-rich protein with Kazal motifs) is a membrane-anchored glycoprotein which regulates MMP2 and MMP9 activity and has been proposed to play a role in embryo implantation while misexpression of RECK has been associated with a variety of carcinomas. Unfortunately, understanding on the steroidal regulation of uterine RECK is lacking. To address this gap in our knowledge, we examined steroidal regulation and cellular expression of Reck mRNA and protein within the mouse uterus in vivo. Uterine Reck mRNA and protein were decreased by estrogen, while progesterone alone had no effect. The estrogen-induced down regulation could be partially blocked by progesterone. RECK was localized primarily to luminal and glandular epithelial cells and the level of expression was regulated in a similar fashion as in whole tissue by the steroids. Knock-down of endogenous RECK in human endometrial epithelial and stromal cells resulted in a significant increase in active MMP9 expression but not that of pro-MMP9 or MMP2. These studies demonstrate that RECK expression in the mouse uterus is steroidally regulated and that within endometrial epithelial and stromal cells, RECK regulates MMP9, but not MMP2 activity.

Puerarin suppresses invasion and vascularization of endometriosis tissue stimulated by 17β-estradiol

BACKGROUND

Puerarin, a phytoestrogen with a weak estrogenic effect, binds to estrogen receptors, thereby competing with 17β-estradiol (E2) and producing an anti-estrogenic effect. This study was to investigate whether puerarin could suppress the invasion and vascularization of E2-stimulated endometriotic tissue.

METHODOLOGY/PRINCIPAL FINDINGS

The endometriotic stromal cells (ESCs) were successfully established and their invasive ability under different treatments was assessed through a Transwell Assay. Simultaneously, matrix metallopeptidase 9 (MMP-9) and tissue inhibitor of metalloproteinase 1 (TIMP-1) were detected by western blotting. Vascularization of endometriotic tissues was observed by chicken chorioallantoic membrane (CAM) assay. The staining of MMP-9, intercellular adhesion molecule 1 (ICAM-1), TIMP-1, and vascular endothelial growth factor (VEGF) in grafted endometriotic tissues was examined using immunohistochemistry analysis. The purity of ESCs in isolated cells was >95%, as determined by the fluoroimmunoassay of vimentin. E2 (10(-8) mol/L) promoted the invasiveness of ESCs by increasing MMP-9 accumulation and decreasing TIMP-1 accumulation. Interestingly, puerarin (10(-9) mol/L) significantly reversed these effects (P<0.01). The CAM assay indicated that puerarin (10(-9) mol/L) also inhibited the angiopoiesis of endometriotic tissue stimulated by the E2 (10(-8) mol/L) treatment (P<0.05). Accordingly, immunohistochemistry showed that the accumulation of MMP-9, ICAM-1, and VEGF was reduced whereas that of TIMP-1 increased in the combination treatment group compared with the E2 treatment group.

CONCLUSIONS/SIGNIFICANCE

This study demonstrated that puerarin could suppress the tissue invasion by ESCs and the vascularization of ectopic endometrial tissues stimulated by E2, suggesting that puerarin may be a potential drug for the treatment of endometriosis.

Selective inhibition of prostaglandin E2 receptors EP2 and EP4 inhibits invasion of human immortalized endometriotic epithelial and stromal cells through suppression of metalloproteinases

Prostaglandin E2 (PGE2) plays an important role in the pathogenesis of endometriosis. We recently reported that inhibition of COX-2 decreased migration as well as invasion of human endometriotic epithelial and stromal cells. Results of the present study indicates that selective inhibition of PGE2 receptors EP2 and EP4 suppresses expression and/or activity of MMP1, MMP2, MMP3, MMP7 and MMP9 proteins and increases expression of TIMP1, TIMP2, TIMP3, and TIMP4 proteins and thereby decreases migration and invasion of human immortalized endometriotic epithelial and stromal cells into matrigel. The interactions between EP2/EP4 and MMPs are mediated through Src and β-arrestin 1 protein complex involving MT1-MMP and EMMPRIN in human endometriotic cells. These novel findings provide an important molecular and cellular framework for further evaluation of selective inhibition of EP2 and EP4 as potential nonsteroidal therapy for endometriosis in childbearing-age women.

Endometrial mRNA expression of matrix metalloproteinases, their tissue inhibitors and cell adhesion molecules in unexplained infertility and implantation failure patients

The aim of this study was to analyse whether some cases of unexplained infertility and implantation failure after IVF could be explained by different expression levels of the matrix metalloproteinases (MMP-2, 9), their tissue inhibitors (TIMP-2, 3) and intercellular (ICAM-1) and vascular (VCAM-1) adhesion molecules in endothelial cells. Total RNA was extracted from the endometrial tissues of 41 women (unexplained infertile, group 1, n = 15; fertile volunteers, group 2, n = 15 and patients with implantation failure after IVF, group 3, n = 11). MMP-2, MMP-9, TIMP-2, TIMP-3, ICAM-1 and VCAM-1 mRNA expression levels were measured quantitatively using real-time polymerase chain reaction. In the endometrium from women with unexplained infertility and implantation failure after IVF, MMP-2 and TIMP-3 expression were significantly decreased when compared with the fertile group (P < 0.05 and P </= 0.001 respectively). In addition, a marked decrease was observed in the expression of VCAM-1 in women with unexplained infertility. These results suggest that the expression of gelatinase A (MMP-2), TIMP-3 and VCAM-1, at least at the transcriptional level, might be regulated by common factors and signalling pathways. The present study adds new and important data in this field and highlights the complex preparation of the endometrium for implantation at the molecular level.

Matrix metalloproteinases are elevated in the urine of patients with endometriosis

In a prospective, blinded, longitudinal study MMP-2, MMP-9, and MMP-9/neutrophil gelatinase-associated lipocalin were significantly more likely to be detected in the urine of patients with endometriosis than in controls.

Association between MMP1 and MMP9 activities and ICAM1 cleavage induced by tumor necrosis factor in stromal cell cultures from eutopic endometria of women with endometriosis

Endometriosis is a benign gynecological pathology in which immune system deregulation may play a role in its initiation and progression. In endometriotic lesions, intercellular adhesion molecule-1 (ICAM1) is released from the cell membrane by proteolytic cleavage of its extracellular domain, a process that coincides with increased expression and proteolytic activity of metalloproteinases such as MMP1 and MMP9. The objective of our study was to investigate the association between MMP1 and MMP9 activities and ICAM1 cleavage mediated by tumor necrosis factor (TNF) in eutopic endometrial stromal cells from women with and without (control) endometriosis during culture. The RNA was evaluated by RT-PCR, and the protein was determined by western blot (ICAM1, MMP1), casein or gelatin zymographies (secreted active MMP1 or MMP9 respectively), ELISA (soluble ICAM1 (sICAM1)), and fluorescence assay (secreted active MMP1). Under basal conditions, proMMP9 dimer and MMP9 were higher in endometriosis cell cultures. In stromal cultures derived from control women and those with endometriosis, TNF augmented the intracellular proMMP1 (1.2-fold in control stromal cells) and ICAM1 (1.4- and 1.9-fold), greatly increased MMP1 and proMMP9 levels, and the sICAM1 concentration (2.3- and 4.3-fold) in their media compared with basal levels. The combination of TNF and MMP9 increased the sICAM1 concentration 14-fold in the endometriosis cell media, whereas GM6001 inhibited the stimulatory effect of TNF in both cell cultures. The deregulation of MMP9, and the TNF participation in the MMP1 and proMMP9 secretions, in the MMP9 expression and in the expression and cleavage of ICAM1 may contribute to the pathophysiology of this disease.

The role of matrix metalloproteinases in the pathogenesis of endometriosis

Endometriosis is a benign, estrogen-dependent disease with an obscure etiology. Even the most widely accepted theory of retrograde menstruation cannot satisfactorily explain the development of endometriosis due to the many gaps in our understanding of its pathophysiology. Although most women have retrograde menstruation; only some develop endometriosis. Apart from simply being present in the peritoneal cavity, the endometrial cells are able to attach to, invade the peritoneum, and proliferate to create and maintain an endometriotic lesion. Matrix metalloproteinases (MMPs) are a group of enzymes that degrade the extracellular matrix. These enzymes participate in the histologic changes of the endometrium during the menstrual cycle with generally a higher expression during the menstrual and proliferative phase of the endometrium and a decreased expression during the secretory phase. As noted above, not only do these enzymes play a crucial factor in the cycling endometrium but the degradation of extracellular matrix is essential for the endometrial cells to invade the peritoneum and to develop an endometriotic lesion as well. The aim of this review is to describe the altered expression of MMPs in the development of endometriosis.

Regulation of uterine matrix metalloproteinase-9 and the role of microRNAs

Controlled expression of matrix metalloproteinase-9 (MMP9) is vital for normal uterine physiology, whereas abnormal expression of MMP9 is associated with uterine disease. Despite the importance of MMP9 within the uterus, its regulation is poorly understood. In this review, the complex regulation of MMP9 within the uterus is highlighted, and the potential novel role of microRNAs in the regulation of this protease is discussed. Emphasis is placed on the necessity to enhance our understanding of the regulation of MMP9 expression, which may lead to the establishment of novel approaches to counteract misexpression of this protease and the diseases associated with it.

Gelatinase A (MM-2), gelatinase B (MMP-9) and their inhibitors (TIMP 1, TIMP-2) in serum of women with endometriosis: Significant correlation between MMP-2, MMP-9 and their inhibitors without difference in levels of matrix metalloproteinases and tissue inhibitors of metalloproteinases in relation to the severity of endometriosis

Endometriosis is a highly prevalent gynecological condition, where the formation of endometriotic foci is linked with locally increased activity of matrix metalloproteinases (MMPs). In the present study, we tested the hypothesis that raised serum levels of MMPs might reflect the severity of endometriosis. We compared serum levels of MMP-2 and MMP-9, and of their tissue inhibitors TIMP-1 and TIMP-2, in infertile women, matched for age and body mass index, with either mild (stage I, END-I; n = 15) or severe endometriosis (stage IV, END-IV; n = 22). There was no difference in the concentrations of MMP-2, MMP-9, TIMP-1 and TIMP-2 between the analyzed groups. There was, however, a correlation between MMP-9 and TIMP-1 for the combined group (n = 37) (r = 0.48; p = 0.0032) and in women with END-IV (r = 0.51; p = 0.0163), as well as a highly significant correlation between MMP-2 and TIMP-2 for the combined group (r = 0.69; p = 0.0001), END-I (r = 0.51; p = 0.0406) and END-IV groups (r = 0.77; p = 0.0001). There was also a significant correlation between TIMP-1 and TIMP-2 in the combined and END-IV groups (r = 0.39; p = 0.0182 and r = 0.5450; p = 0.0099, respectively). The balance between MMPs and their inhibitors is preserved in the serum of women with endometriosis, but serum concentrations of MMP-2, MMP-9, TIMP-1 and TIMP-2 cannot be considered to represent a valid measure of the severity of endometriosis.

Gene expression profiling of the rat endometriosis model

PROBLEM

To investigate the molecular mechanism of endometriosis, gene expression profiling was analyzed in a rat endometriosis model.

METHOD OF STUDY

An endometriosis model was induced by uterine autotransplantation in the peritoneal cavity on a female-SD rat (8 weeks old). As control samples, the normal uterine tissues were used. The gene expression was compared between endometriotic lesions and normal uterine tissues by cDNA microarray analysis, quantitative real time RT-PCR and immunohistochemistry.

RESULTS

The expression of 71 genes was upregulated and that of 45 genes was downregulated in the endometriotic lesions compared to normal uterine tissues. The upregulated genes included genes encoding cytokines, chemokines, growth factors and cell adhesion molecules. The levels of transcripts of osteopontin, Lyn, Vav1, Runx1, and l-selectin in the endometriotic lesions were 130, 10, 10, 12 and 46-fold higher than the respective levels in the eutopic endometrial samples.

CONCLUSION

The results suggest that osteopontin, Lyn, Vav1, Runx1, and l-selectin play important roles in the pathogenesis of endometriosis.

Tissue inhibitors of matrix metalloproteinase-1 levels are increased in serum of patients with allergic contact dermatitis

Allergic contact dermatitis (ACD) is an antigen-specific, T-cell-mediated skin inflammatory disease. Matrix metalloproteinases (MMPs) and their tissue inhibitors of matrix metalloproteinases (TIMPs) play a role in degradation of extracellular matrix and subsequent tissue remodelling during inflammatory process. The objective of this study was to examine a possible role of TIMP-1 and MMP-9 in the pathogenesis of ACD. The serum levels of MMP-9 and TIMP-1 have been measured using enzyme-linked immunosorbent assay in patients with disseminated ACD during exacerbation of skin lesions and the remission stage (n= 20) and were compared with healthy subjects (n= 20). The mean serum levels of TIMP-1 were significantly higher in patients with ACD than in control group (42.8 +/- 4.9 ng/ml). This difference was more prominent in patients with ACD during remission (69.01 +/- 6.99 ng/ml, P < 0.0001) than in patients with exacerbation of disease (46.8 +/- 3.6 ng/ml, P= 0.0054). Mean values of serum MMP-9 did not differ significantly between patients with ACD, both in the acute and in the remission stage, compared with healthy persons (P= 0.76 and P= 0.29, respectively). TIMP-1 might be involved in pathogenesis of ACD. It seems that moderately increased levels of TIMP-1 could reflect degree of activity of skin inflammation, whereas markedly increased levels could contribute to the maintenance of the remission of disease.

Imbalance in the expression of the activating type I and the inhibitory type II interleukin 1 receptors in endometriosis

BACKGROUND

The ectopic establishment and progression of endometrial tissue is dependent upon its interaction with and responsiveness to the stimuli present in its new environment. Immune cell-derived cytokines, such as interleukin 1 (IL1), may alone or in concert with estrogens enhance the capability of ectopic endometrial cells to implant and develop into the host tissue. The objective of this study was to further evaluate the expression and significance of IL1 receptor type I (IL1R1), the signalling receptor that mediates cell activation by IL1, and IL1 receptor type II (IL1R2), a potent and specific down-regulator of IL1 action, in normal compared to endometriotic/endometrial tissues.

METHODS

Techniques included immunohistochemistry, immunofluorescent staining, ELISA, western blotting and endometriotic cell culture transfection.

RESULTS

Our study showed an imbalance in the expression of IL1R1 and IL1R2 in eutopic, and particularly in ectopic, endometrial tissues of women with endometriosis. Actually, a decreased IL1R2 expression is predominant in the eutopic and ectopic endometrium of women with endometriosis when compared with normal women, whereas a concomitant increase in IL1R1 expression occurs in ectopic endometrial tissue in comparison to eutopic endometrial tissue of normal or endometriotic women, particularly in the initial and most active implants. Transfection of endometriotic cells with a cDNA coding for IL1R2 resulted in a significant decrease in IL1-induced secretion of vascular endothelial cell growth factor and monocyte chemotactic protein 1.

CONCLUSIONS

IL1R1/IL1R2 imbalance may amplify endometrial cell responsiveness to IL1 and represent a key mechanism underlying the ability of these cells to implant and develop into host tissues.

TIMP-1 as candidate gene for embryo survival in two divergent lines selected for uterine capacity in rabbits

Selection on uterine capacity has been used in animal breeding as a way to improve the litter size. A divergent selection experiment for uterine capacity was performed in rabbits during ten generations. After the first generations of selection, large differences in number of implanted embryos were obtained between high and low lines. The major part of the differences between lines was due to embryo survival. A segregation analysis suggested the presence of a major gene affecting the reproductive traits. The objective of this work was to test the TIMP-1 gene as a candidate gene for embryo survival in rabbits since it stands up as a target for the investigation of reproductive problems in humans. We have analyzed the parental generation of a F2 cross which consists of 8 and 14 animals from the high and low uterine capacity lines, respectively. The rabbit TIMP-1 gene structure and sequence has been determined, including the proximal promoter region. Despite of the absence of polymorphism between lines in the screened regions (CDS, proximal promoter, exon 1, intron 1, and exon 2), a real-time RT-PCR quantification of the TIMP-1 mRNA in oviduct has shown significant differences between high and low lines at 62 hr of gestation, just when rabbit embryos are located in the oviduct, postulating TIMP-1 as an interesting candidate gene to be involved in the phenotypic differences between the two rabbit lines.

Suppression of matrix metalloproteinase-9 by prostaglandin E(2) in peritoneal macrophage is associated with severity of endometriosis

Decreased phagocytotic ability of macrophages has been reported to be associated with the severity of endometriosis, although the underlying mechanism remains uncharacterized. Expression and secretion of matrix metalloproteinase (MMP)-9 by macrophages is a means to degrade the extracellular matrix of cells that are designated for phagocytosis. Here, we describe the regulation of MMP-9 expression and activity in peritoneal macrophages of women with endometriosis. Results demonstrated that peritoneal macrophages isolated from women with endometriosis have decreased levels of protein and enzyme activity of MMP-9. Treatment of macrophages with peritoneal fluid obtained from patients with severe endometriosis inhibited MMP-9 expression and gelatinase activity. Further investigation identified prostaglandin (PG) E(2) as the major factor in the peritoneal fluid that inhibited MMP-9 activity. The inhibitory effect of PGE(2) was mediated via the EP2/EP4-dependent PKA pathway. Furthermore, expression of tissue inhibitor of metalloproteinase-1, tissue inhibitor of metalloproteinase-2, and RECK in macrophages was not affected by treatment with PGE(2), indicating the effect of PGE(2) on suppressing MMP-9 activity was not mediated by up-regulation of its inhibitor. Our results suggest that decreased phagocytotic capability of peritoneal macrophage in patients with endometriosis may be caused by PGE(2)-mediated decreases in MMP-9 expression.

Inhibiting MMP activity prevents the development of endometriosis in the chicken chorioallantoic membrane model

BACKGROUND

Matrix metalloproteinases (MMPs) are essential for extracellular matrix remodelling and may contribute to the development of endometriosis. Transplantation of endometrium onto the chicken chorioallantoic membrane (CAM) results in endometriosis-like lesion formation, a process that requires extensive tissue remodelling. We investigated the expression of a wide range of MMPs in menstrual endometrium, endometriosis-like lesions in CAMs, in peritoneal endometriosis and in endometriosis in the rectovaginal space, as well as the function of MMPs in early lesion formation in the CAM model.

METHODS

Expression of MMPs was evaluated by immunohistochemistry and MMP function was studied in the CAM by inhibiting MMP activity during lesion formation.

RESULTS

Nearly all MMPs were present in all tissues studied. No significant differences in the expression of a majority of MMPs were found in endometriosis-like lesions in CAMs when compared with human endometriosis. Inhibition of MMP-1, -2, -3, -7 and -13 activities significantly impaired endometriosis-like lesion formation in CAMs.

CONCLUSIONS

The MMP expression profiles of experimentally induced endometriosis in CAMs and human endometriosis are similar. The prevention of endometriosis-like lesion formation in the CAM by inhibiting MMP activity strongly suggests that MMPs have a function in the early development of endometriotic lesions.

Pathogenesis of endometriosis

Many women harbour spots of peritoneal endometriosis without having any symptoms; this is referred to as the phenomenon endometriosis. Some of these women go on to develop symptomatic endometriosis. Although we know the factors potentially involved in the aetiology and pathogenesis of endometriosis, the exact mechanism by which the phenomenon endometriosis develops into the disease endometriosis, with its associated signs and symptoms, remain obscure. The widely accepted theory is Sampson's transplantation theory. Recent findings indicate that certain properties of the endometrium, and the influence of the local environment, are crucial in the development of endometriosis. Early endometriosis lesion formation is described in detail, as this seems to be a key process in the development of peritoneal endometriosis.

The role of the matrix metalloproteinases in human endometrial and ovarian cycles

The matrix metalloproteinases (MMPs) are part of an expanded family of proteins called the astacin family of zinc metalloproteinases. The MMPs, probably balanced by their tissue inhibitors of metalloproteinases (TIMPs), are essential effectors of developmental processes participating in cell migration, cell proliferation, apoptosis and tissue morphogenesis. The MMPs regulate the function of biologically active molecules as well as fulfilling an important role in endothelial cell invasion, angiogenesis and in tumor progression. The dynamic normal physiology of the human reproductive system involves almost all of the above-mentioned aspects of MMPs activity. This review presents and discusses new insights into the role of MMPs, and their TIMPs, in human endometrial cycle and ovarian function.