Matrix metalloproteinase expression in Macaca mulatta endometrium: evidence for zone-specific regulatory tissue gradients

A protocol for creating endometriosis in rhesus macaques (Macaca mulatta)

BACKGROUND

Endometriosis is the presence of endometrium-like tissue outside the uterine cavity. An experimental model of endometriosis has been created in the baboon by the transcervical collection and laparoscopic inoculation of menstrual endometrium. Macaques are the preferred model for pharmaceutical development, but the complex anatomy of the macaque cervix makes the baboon method impractical. In this work, we sought to validate a surgical approach for creating endometriosis in macaques.

METHODS

Menstrual endometrium was collected via laparoscopic intrauterine puncture and transferred to the peritoneal cavity. We repeated this procedure during three menstruations. Endometriotic tissue was identified during laparoscopy, collected, and characterized by immunohistochemistry.

RESULTS

Sham surgery-treated animals (n = 3) failed to develop endometriosis. We identified red, powder burnt, and white lesions in 13/14 of the treated animals; the stroma of the red lesions stained positive for ovarian steroid receptors.

CONCLUSION

This surgical technique can reliably create hormone-responsive endometriosis in macaques for therapeutic studies.

Insights into the immunomodulatory regulation of matrix metalloproteinase at the maternal-fetal interface during early pregnancy and pregnancy-related diseases

Trophoblast immune cell interactions are central events in the immune microenvironment at the maternal-fetal interface. Their abnormalities are potential causes of various pregnancy complications, including pre-eclampsia and recurrent spontaneous abortion. Matrix metalloproteinase (MMP) is highly homologous, zinc(II)-containing metalloproteinase involved in altered uterine hemodynamics, closely associated with uterine vascular remodeling. However, the interactions between MMP and the immune microenvironment remain unclear. Here we discuss the key roles and potential interplay of MMP with the immune microenvironment in the embryo implantation process and pregnancy-related diseases, which may contribute to understanding the establishment and maintenance of normal pregnancy and providing new therapeutic strategies. Recent studies have shown that several tissue inhibitors of metalloproteinases (TIMPs) effectively prevent invasive vascular disease by modulating the activity of MMP. We summarize the main findings of these studies and suggest the possibility of TIMPs as emerging biomarkers and potential therapeutic targets for a range of complications induced by abnormalities in the immune microenvironment at the maternal-fetal interface. MMP and TIMPs are promising targets for developing new immunotherapies to treat pregnancy-related diseases caused by immune imbalance.

The Plasminogen Activator System, Glucocorticoid, and Mineralocorticoid Receptors in the Primate Endometrium During Artificial Menstrual Cycles

As a key mechanism in fibrinolysis and tissue remodeling, the plasminogen activator system has been suggested in the process of endometrial shedding and tissue remodeling. Previous studies have explored the role of estrogen, progesterone, and androgen receptors as well as elements of the renin-angiotensin-aldosterone system in shaping the morphology of the endometrium. This study investigates the distribution and concentrations of the mineralocorticoid receptor, glucocorticoid receptor, tissue plasminogen activator, urokinase plasminogen activator, and plasminogen activator inhibitor-1 within the endometrial stroma, glandular, and endothelial cells of the primate endometrium during artificial menstrual cycles. Our immunohistochemistry quantification shows mineralocorticoid and glucocorticoid receptors are ubiquitously distributed within the macaque endometrium with their patterns of expression following similar fluctuations to urokinase and tissue plasminogen activators particularly within the endometrial vasculature. These proteins are present in endometrial vasculature in high levels during the proliferative phase, decreasing levels during the secretory phase followed by rising levels in the menstrual phase. These similarities could suggest overlapping pathways and interactions between the plasminogen activator system and the steroid receptors within the endometrium. Given the anti-inflammatory properties of glucocorticoids and the role of plasminogen activators in endometrial breakdown, the glucocorticoid receptor may be contributing to stabilizing the endometrium by regulating plasminogen activators during the proliferative phase and menstruation. Furthermore, given the anti-mineralocorticoid properties of certain anti-androgenic progestins and their reduced unscheduled uterine bleeding patterns, the mineralocorticoid receptor may be involved in unscheduled endometrial bleeding.

Mechanisms of Scarless Repair at Time of Menstruation: Insights From Mouse Models

The human endometrium is a remarkable tissue which may experience up to 400 cycles of hormone-driven proliferation, differentiation and breakdown during a woman's reproductive lifetime. During menstruation, when the luminal portion of tissue breaks down, it resembles a bloody wound with piecemeal shedding, exposure of underlying stroma and a strong inflammatory reaction. In the absence of pathology within a few days the integrity of the tissue is restored without formation of a scar and the endometrium is able to respond appropriately to subsequent endocrine signals in preparation for establishment of pregnancy if fertilization occurs. Understanding mechanisms regulating scarless repair of the endometrium is important both for design of therapies which can treat conditions where this is aberrant (heavy menstrual bleeding, fibroids, endometriosis, Asherman's syndrome) as well as to provide new information that might allow us to reduce fibrosis and scar formation in other tissues. Menstruation only occurs naturally in species that exhibit spontaneous stromal cell decidualization during the fertile cycle such as primates (including women) and the Spiny mouse. To take advantage of genetic models and detailed time course analysis, mouse models of endometrial shedding/repair involving hormonal manipulation, artificial induction of decidualization and hormone withdrawal have been developed and refined. These models are useful in modeling dynamic changes across the time course of repair and have recapitulated key features of endometrial repair in women including local hypoxia and immune cell recruitment. In this review we will consider the evidence that scarless repair of endometrial tissue involves changes in stromal cell function including mesenchyme to epithelial transition, epithelial cell proliferation and multiple populations of immune cells. Processes contributing to endometrial fibrosis (Asherman's syndrome) as well as scarless repair of other tissues including skin and oral mucosa are compared to that of menstrual repair.

Nanomedicines for Endometriosis: Lessons Learned from Cancer Research

Endometriosis is an incurable gynecological disease characterized by the abnormal growth of endometrium-like tissue, characteristic of the uterine lining, outside of the uterine cavity. Millions of people with endometriosis suffer from pelvic pain and infertility. This review aims to discuss whether nanomedicines that are promising therapeutic approaches for various diseases have the potential to create a paradigm shift in endometriosis management. For the first time, the available reports and achievements in the field of endometriosis nanomedicine are critically evaluated, and a summary of how nanoparticle-based systems can improve endometriosis treatment and diagnosis is provided. Parallels between cancer and endometriosis are also drawn to understand whether some fundamental principles of the well-established cancer nanomedicine field can be adopted for the development of novel nanoparticle-based strategies for endometriosis. This review provides the state of the art of endometriosis nanomedicine and perspective for researchers aiming to realize and exploit the full potential of nanoparticles for treatment and imaging of the disorder.

Matrix Metalloprotease-7 Mediates Nucleolar Assembly and Intra-nucleolar Cleaving p53 in Gefitinib-Resistant Cancer Stem Cells

The enlarged distinct bulky-ball-like nucleolus matrix assembly is observed in most cancer stem cells (CSCs); however, the underlying mechanism is largely unknown. We show that matrix metalloproteinase-7 (MMP-7) shedding MUC-1 SEA domain releases MUC-1 C-ter, facilitating the nucleolus trafficking of p53 in gefitinib-resistant lung CSCs. The nucleolus colocalizations of p53, MUC-1 C-ter, MMP-7 and nucleolin were observed in the CD34⁺ CXADR⁺ CD44v₃⁺ gefitinib-resistant EGFR^L858R/T790M CSC colonies. MUC-1 C-ter induced a unique porous bulky-ball-shaped, cagelike nucleolus that functions as a nucleus molecular “garage” for potent tumor suppressor, p53. Nucleolus could also facilitate the novel sub-nucleus compartment for proteolytic processing p53 by MMP-7 to generate a 35 kDa fragment. Moreover, we show that salinomycin, an anti-CSC agent, disrupts nucleolus by inducing nucleoplasm translocation of p53 and sensitizing CSC to chemotherapy drugs. Thus, this study highlights the MMP-7-MUC-1-p53 axis in nucleolus as a potential therapeutic target for anti-CSCs to resolve the chemotherapy-resistance dilemma.

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MMP-7 cleaves the SEA domain of MUC-1 and releases MUC-1 C-ter

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MUC-1 C-ter mediates bulky-ball-like nucleolus assembly trapping p53 in nucleolus

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MMP-7 cleaves p53 to 35 kDa fragments in the nucleolus of gefitinib-resistant CSCs

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Salinomycin induces p53 nucleoplasm translocation sensitizing CSCs to gefitinib

The regulation of trophoblast invasion and decidual reaction by matrix metalloproteinase-2, metalloproteinase-7, and metalloproteinase-9 expressions in the rat endometrium

PURPOSE

We aimed to evaluate how matrix metalloproteinases (MMPs) regulate the trophoblast invasion and placentation.

METHODS

Female rats were divided into the estrous cycle and early pregnancy day groups. Obtained uterine tissues and implantation sites were processed for immunofluorescence and real-time PCR examinations.

RESULTS

The mRNA expression of MMP-7 was higher than MMP-2 and MMP-9. Immunofluorescence findings confirmed that MMP-2, MMP-7, and MMP-9 were localized in the endometrial stroma, while MMP-7 was high in glandular and lining epithelial cells throughout the entire estrous cycle. However, their immunolocalizations and mRNA expressions were dramatically changed with the early pregnancy days. The MMP-7 reached very strong immunostaining in the giant trophoblast cells (GTCs), and the cytoplasm of mature and differentiating decidual cells, whereas MMP-2 and MMP-9 were mostly seen in the primary decidual zone (PDZ), GTCs, and the endothelium of blood vessels.

CONCLUSIONS

All three MMPs seemed likely to be a key mediator of trophoblast invasion into the decidual region as well as angiogenesis during the placentation process. Due to the strong and wide expression of MMP-7 in the mature decidua, it could be suggested that MMP-7 is important for decidual ECM remodeling and it might be used as a new marker of decidual reaction.

Physiology of the Endometrium and Regulation of Menstruation

The physiological functions of the uterine endometrium (uterine lining) are preparation for implantation, maintenance of pregnancy if implantation occurs, and menstruation in the absence of pregnancy. The endometrium thus plays a pivotal role in reproduction and continuation of our species. Menstruation is a steroid-regulated event, and there are alternatives for a progesterone-primed endometrium, i.e., pregnancy or menstruation. Progesterone withdrawal is the trigger for menstruation. The menstruating endometrium is a physiological example of an injured or “wounded” surface that is required to rapidly repair each month. The physiological events of menstruation and endometrial repair provide an accessible in vivo human model of inflammation and tissue repair. Progress in our understanding of endometrial pathophysiology has been facilitated by modern cellular and molecular discovery tools, along with animal models of simulated menses. Abnormal uterine bleeding (AUB), including heavy menstrual bleeding (HMB), imposes a massive burden on society, affecting one in four women of reproductive age. Understanding structural and nonstructural causes underpinning AUB is essential to optimize and provide precision in patient management. This is facilitated by careful classification of causes of bleeding. We highlight the crucial need for understanding mechanisms underpinning menstruation and its aberrations. The endometrium is a prime target tissue for selective progesterone receptor modulators (SPRMs). This class of compounds has therapeutic potential for the clinical unmet need of HMB. SPRMs reduce menstrual bleeding by mechanisms still largely unknown. Human menstruation remains a taboo topic, and many questions concerning endometrial physiology that pertain to menstrual bleeding are yet to be answered.

In-vitro construction of endometrial-like epithelium using CD146+ mesenchymal cells derived from human endometrium

Endometrial CD146⁺ cells were purified, using magnetic activated cell sorting, and then embedded and cultured in a collagen-matrigel scaffold on top of myometrial smooth muscle cells for 10 days. At the end of culture period, the differentiation and formation of the epithelial-like cells were confirmed by morphological and ultrastructural evaluations, and analysis by reverse transcription polymerase chain reaction of the specific expression of genes: osteopontin (SPP1), matrix metalloproteinase 2, zonula occludens 1, laminin alpha 2 and collagen type IV; and by western blotting of CD9 protein. The results showed that the human endometrial mesenchymal CD146⁺ cells were able to produce endometrial glandular tube-like structures in vitro. Ultrastructural observation revealed some projections on the apical surfaces, appearance of basal lamina-like structures on the basal surface, and tight junctions and desmosomes on the lateral surfaces of the epithelial-like cells. The expression of studied genes at RNA level and CD9 at protein level confirmed the formation of endometrial epithelial-like cells. This culture system may have potential applications in cell therapy and in studies on human embryo implantation.

Expression and localization of matrix metalloproteinases (MMP-2, -7, -9) and their tissue inhibitors (TIMP-2, -3) in the chicken oviduct during pause in laying induced by tamoxifen

Induced pause in egg laying simulates natural molting events in which the hen's reproductive organs regress and rejuvenate. Such processes require extracellular matrix remodeling that is maintained, at least in part, by the action of proteolytic enzymes known as matrix metalloproteinases (MMPs). Nevertheless, information concerning the expression and hormonal regulation of MMP system members in chickens is scarce. Therefore, MMP-2, -7, and -9 and their tissue inhibitors (TIMP-2, -3) expression and localization were investigated in all segments of the domestic hen oviduct (infundibulum, magnum, isthmus, shell gland, vagina) during a pause in egg laying induced by tamoxifen (TMX)-an estrogen receptor modulator. Hy-Line Brown hens were treated daily with TMX (n = 6) at a dose of 6 mg/kg of body weight or a vehicle (n = 6) until complete cessation of egg laying (for 7 days). Chickens were decapitated on Day 7 of the experiment. Real-time polymerase chain reaction and Western blotting revealed section-dependent expression of MMP-2, -7, -9 and TIMP-2 and -3. Immunohistochemistry found tissue and cell-dependent localization of examined proteins in the wall of the oviduct. The MMP-2, TIMP-2, and TIMP-3 were localized mainly in the luminal epithelium, MMP-7 in the luminal and glandular epithelium, whereas MMP-9 was detected only in the connective tissue. Treatment of chickens with TMX markedly elevated the relative expression of MMP-7 and MMP-9 mRNA in the oviduct, but did not affect MMP-2, TIMP-2, and TIMP-3 mRNA levels. However, TMX increased the MMP-2 protein level in the infundibulum, shell gland, and vagina as well as activity of MMP-2 evaluated by gelatin zymography. The results obtained indicate that MMP-2, MMP-7, and MMP-9 are involved in chicken oviduct regression. Moreover, changes in the expression and activity of chosen MMPs after TMX treatment may indicate a contribution of estrogen in the regulation of transcription, translation, and/or the activity of selected elements of the MMP system.

The role of decidual cells in uterine hemostasis, menstruation, inflammation, adverse pregnancy outcomes and abnormal uterine bleeding

BACKGROUND

Human pregnancy requires robust hemostasis to prevent hemorrhage during extravillous trophoblast (EVT) invasion of the decidualized endometrium, modification of spiral arteries and post-partum processes. However, decidual hemorrhage (abruption) can occur throughout pregnancy from poorly transformed spiral arteries, causing fetal death or spontaneous preterm birth (PTB), or it can promote the aberrant placentation observed in intrauterine growth restriction (IUGR) and pre-eclampsia; all leading causes of perinatal or maternal morbidity and mortality. In non-fertile cycles, the decidua undergoes controlled menstrual bleeding. Abnormal uterine bleeding (AUB) accompanying progestin-only, long-acting, reversible contraception (pLARC) accounts for most discontinuations of these safe and highly effective agents, thereby contributing to unwanted pregnancies and abortion. The aim of this study was to investigate the role of decidual cells in uterine hemostasis, menstruation, inflammation, adverse pregnancy outcomes and abnormal uterine bleeding.

METHODS

We conducted a critical review of the literature arising from PubMed searches up to December 2015, regarding in situ and in vitro expression and regulation of several specific proteins involved in uterine hemostasis in decidua and cycling endometrium. In addition, we discussed clinical and molecular mechanisms associated with pLARC-induced AUB and pregnancy complications with abruptions, chorioamnionitis or pre-eclampsia.

RESULTS

Progestin-induced decidualization of estradiol-primed human endometrial stromal cells (HESCs) increases in vivo and in vitro expression of tissue factor (TF) and type-1 plasminogen activator inhibitor (PAI-1) while inhibiting plasminogen activators (PAs), matrix metalloproteinases (MMPs), and the vasoconstrictor, endothelin-1 (ET-1). These changes in decidual cell-derived regulators of hemostasis, fibrinolysis, extracellular matrix (ECM) turnover, and vascular tone prevent hemorrhage during EVT invasion and vascular remodeling. In non-fertile cycles, progesterone withdrawal reduces TF and PAI-1 while increasing PA, MMPs and ET-1, causing menstrual-associated bleeding, fibrinolysis, ECM degradation and ischemia. First trimester decidual hemorrhage elicits later adverse outcomes including pregnancy loss, pre-eclampsia, abruption, IUGR and PTB. Decidual hemorrhage generates excess thrombin that binds to decidual cell-expressed protease-activated receptors (PARs) to induce chemokines promoting shallow placentation; such bleeding later in pregnancy generates thrombin to down-regulate decidual cell progesterone receptors and up-regulate cytokines and MMPs linked to PTB. Endometria of pLARC users display ischemia-induced excess vasculogenesis and progestin inhibition of spiral artery vascular smooth muscle cell proliferation and migration leading to dilated fragile vessels prone to bleeding. Moreover, aberrant TF-derived thrombin signaling also contributes to the pathogenesis of endometriosis via induction of angiogenesis, inflammation and cell survival.

CONCLUSION

Perivascular decidualized HESCs promote endometrial hemostasis during placentation yet facilitate menstruation through progestational regulation of hemostatic, proteolytic, and vasoactive proteins. Pathological endometrial hemorrhage elicits excess local thrombin generation, which contributes to pLARC associated AUB, endometriosis and adverse pregnancy outcomes through several biochemical mechanisms.

Translational In Vivo Models for Women's Health: The Nonhuman Primate Endometrium--A Predictive Model for Assessing Steroid Receptor Modulators

Macaques and baboons display physiological responses to steroid hormones that are similar to those of women. Herein, we describe various uses of nonhuman primates for preclinical studies on menstruation, endometriosis, and as a model system to evaluate reproductive therapies and contraceptives. Our goal is to outline the strengths of the nonhuman primate model for studies leading to improved therapies for women.

Expression and localization of matrix metalloproteinases (MMP-2, -7, -9) and their tissue inhibitors (TIMP-2, -3) in the chicken oviduct during maturation

Although participation of matrix metalloproteinases (MMPs) in reproductive tract remodeling has been strongly suggested in mammalian species, the role of MMPs in the avian oviduct has received little attention. To gain a better understanding of the potential role of the MMP system in avian oviduct development, mRNA and protein expression, localization of selected MMPs and their tissue inhibitors (TIMPs), and gelatinolytic activity in the oviduct of growing chickens were examined. The oviducts were collected from Hy-Line Brown hens before (10, 12, 14 and 16 weeks of age) and after (week 17) the onset of egg laying. The MMP-2, -7, -9 and TIMP-2 and -3 genes were found to be differentially expressed in all examined oviductal sections: the infundibulum, magnum, isthmus and shell gland on both mRNA (by real time polymerase chain reaction) and protein (by western blotting and immunohistochemistry) levels. In the course of oviduct development, the relative expression of all genes decreased in most sections. Protein level of MMP-9 was diminished, while MMP-7 and TIMP-3 were elevated in the oviduct of growing birds. MMP-2 and TIMP-2 protein levels remained constant, with a slight increase in MMP-2 concentration just before reaching maturity. The relative activity of MMP-2 and -9 (assessed by gelatin zymography) was higher (P < 0.05, P < 0.01) in immature birds compared with adults. Immunohistochemistry demonstrated cell- and tissue-specific localization of MMPs and TIMPs in the wall of the chicken oviduct. We concluded that changes in the expression of examined MMPs and their inhibitors, as well as alterations in MMP activity occurring simultaneously with changes in the morphology of the chicken oviduct, suggest the involvement of the MMP system in the proper development and functioning of this organ. Mechanisms regulating the expression and activity of MMPs require further clarification.

Molecular and functional aspects of menstruation in the macaque

Much of our understanding of the molecular control of menstruation arises from laboratory models that experimentally recapitulate some, but not all, aspects of uterine bleeding observed in women. These models include: in vitro culture of endometrial explants or isolated endometrial cells, transplantation of human endometrial tissue into immunodeficient mice and the induction of endometrial breakdown in appropriately pretreated mice. Each of these models has contributed to our understanding of molecular and cellular mechanisms of menstruation, but nonhuman primates, especially macaques, are the animal model of choice for evaluating therapies for menstrual disorders. In this chapter we review some basic aspects of menstruation, with special emphasis on the macaque model and its relevance to the clinical issues of irregular and heavy menstrual bleeding (HMB).

Steroid regulation of menstrual bleeding and endometrial repair

The ovarian steroid hormones progesterone and estradiol are well established regulators of human endometrial function. However, more recent evidence suggests that androgens and locally generated steroids, such as the glucocorticoids, also have a significant impact on endometrial breakdown and repair. The temporal and spatial pattern of steroid receptor presence in endometrial cells has a significant impact on the endometrial response to steroids. Furthermore, regulation of steroid receptor function by modulatory proteins further refines local responses. This review focuses on steroid regulation of endometrial function during the luteo-follicular transition with a focus on menstruation and endometrial repair.

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.

Localization and hormonal regulation of endometrial matrix metalloproteinase-26 in the rhesus macaque

BACKGROUND

The current understanding of hormonal regulation of matrix metalloproteinase-26 (MMP-26) in the primate endometrium is incomplete. The goal of this work was to clarify estrogen and progesterone regulation of MMP-26 in the endometrium of ovariectomized, hormone-treated rhesus macaques.

METHODS

Ovariectomized rhesus macaques (n= 66) were treated with estradiol (E(2)), E(2) plus progesterone, E(2) followed by progesterone alone or no hormone. Endometrium was collected from the hormone-treated animals during the early, mid- and late proliferative and secretory phases of the artificial menstrual cycle. MMP-26 expression was quantified by real-time PCR, and MMP-26 transcript and protein were localized by in situ hybridization and immunohistochemistry and correlated with estrogen receptor 1 and progesterone receptor (PGR).

RESULTS

MMP-26 was localized to glandular epithelium and was undetectable in the endometrial stroma and vasculature. MMP-26 transcript levels were minimal in the hormone-deprived macaques and treatment with E(2) alone did not affect MMP-26 levels. Treatment with progesterone both in the presence and absence of E(2) stimulated MMP-26 expression in the early and mid-secretory phases (P < 0.001). MMP-26 expression preceded decidualization of endometrial stroma. MMP-26 levels then declined to baseline in the late secretory phase (P < 0.01) despite continued E(2) plus progesterone treatment. Loss of detectable MMP-26 expression in the late secretory phase was correlated with late secretory phase loss of glandular epithelial PGR.

CONCLUSIONS

Endometrial MMP-26 expression is dependent on the presence of progesterone in the early secretory phase and then gradually becomes refractory to progesterone stimulation in the late secretory phase. In the macaque, MMP-26 is a marker of the pre-decidual, secretory endometrium. During the second half of the late secretory phase, and during decidualization, MMP-26 loses its response to progesterone concurrent with the loss of epithelial PGR. The decline in MMP-26 levels between the mid- and late secretory phases may play a role in the receptive window for embryo implantation.

The role of autophagy in human endometrium

Autophagy appears to play an important role in the normal development and maintenance of homeostasis in a variety of tissues, including the female reproductive tract. However, the role of autophagy and the association between autophagy and apoptosis in cyclic remodeling of the human endometrium have not been described. Therefore, we investigated the involvement of autophagy during the human endometrial cycle and its association with apoptosis. Endometrial samples were obtained from 15 premenopausal, nonpregnant women who underwent hysterectomies for benign gynecological reasons. The autophagy-associated protein, microtubule-associated protein 1 light chain 3 alpha (MAP1LC3A), was immunolocalized, and its expression level was measured by Western blot analysis. Apoptosis was evaluated by measuring the expression level of cleaved caspase 3 protein. MAP1LC3A protein was primarily expressed within the endometrial glandular cells and increased during the secretory phase. The expression level of the membrane-bound form of MAP1LC3A (MAP1LC3A-II) also increased as the menstrual cycle progressed, reaching a maximum level during the late secretory phase. This pattern coincided with the expression of cleaved caspase 3. Furthermore, expression of MAP1LC3A-II and cleaved caspase 3 increased in the in vitro-cultured endometrial cancer cells when estrogen and/or progesterone were withdrawn from the culture media to mimic physiological hormonal changes. These findings suggest that endometrial cell autophagy is directly involved in the cyclic remodeling of the human endometrium and is correlated with apoptosis. In addition, we inhibited autophagic processes using 3-methyladenine (3-MA) or bafilomycin A1 (Baf A1) to evaluate the role of autophagy in apoptosis induction in endometrial cancer cells. While the inhibition of autophagosome formation using 3-MA did not decrease apoptosis or cell death, the inhibition of autophagosome degradation by fusion with lysosomes using Baf A1 increased apoptosis and cell death, suggesting that the accumulation of autophagosomes induces apoptosis. Furthermore, Baf A1-induced apoptotic cell death was decreased by the apoptosis inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK). In conclusion, these results indicate that autophagy is involved in the endometrial cell cycle affecting apoptosis and is most prominent during the late secretory phase.

Regulation of matrix metalloproteinases activity studied in human endometrium as a paradigm of cyclic tissue breakdown and regeneration

When abundant and activated, matrix metalloproteinases (MMPs, or matrixins) degrade most, if not all, constituents of the extracellular matrix (ECM). The resulting massive tissue breakdown is best exemplified in humans by the menstrual lysis and shedding of the endometrium, the mucosa lining the uterus. After menstruation, MMP activity needs to be tightly controlled as the endometrium regenerates and differentiates to avoid abnormal tissue breakdown while allowing tissue repair and fine remodelling to accommodate implantation of a blastocyst. This paper reviews how MMPs are massively present and activated in the endometrium at menstruation, and how their activity is tightly controlled at other phases of the cycle. Progesterone represses expression of many but not all MMPs. Its withdrawal triggers focal expression of MMPs specifically in the areas undergoing lysis, an effect mediated by local cytokines such as interleukin-1α, LEFTY-2, tumour necrosis factor-α and others. MMP-3 is selectively expressed at that time and activates proMMP-9, otherwise present in latent form throughout the cycle. In addition, a large number of neutrophils loaded with MMPs are recruited at menstruation through induction of chemokines, such as interleukin-8. At the secretory phase, progesterone repression of MMPs is mediated by transforming growth factor-β. Tissue inhibitors of metalloproteinases (TIMPs) are abundant at all phases of the cycle to prevent any undue MMP activity, but are likely overwhelmed at menstruation. At other phases of the cycle, MMPs can elude TIMP inhibition as exemplified by recruitment of active MMP-7 to the plasma membrane of epithelial cells, allowing processing of membrane-associated growth factors needed for epithelial repair and proliferation. Finally, receptor-mediated endocytosis through low density lipoprotein receptor-related protein-1 (LRP-1) efficiently clears MMP-2 and -9 at the proliferative and secretory phases. This mechanism is probably essential to prevent any excessive ECM degradation by the active form of MMP-2 that is permanently present. However, shedding of the ectodomain of LRP-1 specifically at menstruation prevents endocytosis of MMPs allowing full degradation of the ECM. Thus endometrial MMPs are regulated at the levels of transcription, release from infiltrating neutrophils, activation, binding to the cell membrane, inhibition by TIMPs and endocytic clearance by LRP-1. This allows tight control during endometrial growth and differentiation but results in a burst of activity for menstrual tissue breakdown. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

Estrogen and progesterone regulate expression of the endothelins in the rhesus macaque endometrium

BACKGROUND

Endothelins (EDNs) are thought to modulate endometrial blood flow during menses, stromal healing and endometrial growth during the proliferative phase. Our goal was to assess the effects of estrogen and progesterone on the EDN paracrine system in the endometrium of rhesus macaques.

METHODS

In this study, archived samples were used. These samples were collected from oophorectomized rhesus macaques that were treated sequentially with estradiol (E(2)) and then E(2) plus progesterone to create artificial menstrual cycles. Endometrium from animals in the menstrual, proliferative and secretory phases of the artificial cycle were analyzed by real-time PCR, in situ hybridization and immunocytochemistry to detect changes in EDN peptides (EDN1, EDN2, EDN3), EDN receptors (EDNRA, EDNRB), EDN-converting enzyme 1 (ECE1) and membrane metalloendopeptidase (MME)-an enzyme that degrades the EDNs.

RESULTS

Compared with the late secretory phase, progesterone withdrawal at the end of the artificial menstrual cycle triggered an increase (P< 0.05) in EDN1, EDNRB and ECE1 in the upper functionalis zone during menses of the next cycle. Treatment with E(2) alone in the proliferative phase increased (P< 0.05) EDNRA transcript, which was confined predominantly to the stromal cells. E(2) plus progesterone in the artificial secretory phase suppressed (P< 0.05) the expression of EDN3 in the functionalis zone stroma and epithelia, tended (P= 0.08) to attenuate levels of epithelial EDN2 and markedly up-regulated (P< 0.05) the stromal expression of MME.

CONCLUSIONS

Our results indicate that estrogen and progesterone regulate the EDN family during the menstrual cycle. The changes in the EDN paracrine system during the mid-secretory phase may indicate a role for EDN during embryo implantation.

Progesterone: a pivotal hormone at menstruation

The human endometrium is exposed to repeated inflammation every month, culminating in tissue breakdown and menstruation. Subsequently, the endometrium has a remarkable capacity for efficient repair and remodeling to enable implantation if fertilization takes place. Endometrial function is known to be governed by the ovarian hormones estradiol and progesterone. This review paper focuses on hormonal control of the cyclical tissue injury and repair that takes place in the local endometrial environment at the time of menstruation. Progesterone levels decline premenstrually as the corpus luteum regresses in the absence of pregnancy, and estradiol levels increase during the postmenstrual phase. The functional impact of these significant changes is discussed, including their immediate and downstream effects. Finally, we examine the contribution of aberrant endometrial function to the presentation of heavy menstrual bleeding and identify potential therapeutic targets for the treatment of this common gynecological problem.

Dynamic in vivo changes in the activities of gelatinases, matrix metalloproteinases (MMPs), and tissue inhibitor of metalloproteinases (TIMPs) in buffalo (Bubalus bubalis) uterine luminal fluid during estrous cycle and early pregnancy

In ruminants, the phenomenon of endometrial tissue remodeling during the estrous cycle and early pregnancy is not fully understood. In this report, the occurrence of tissue remodeling, if any, in buffalo endometrium was studied by detecting gelatinases, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs); the key regulators of tissue remodeling, in uterine luminal fluids (ULF) of cycling and early pregnant (approx. 43-65 days) buffaloes. Each stage of the estrous cycle and pregnant ULF demonstrated a unique profile of gelatinase activities compared to serum/follicular fluid, with a major gelatinase band of 60 kDa with highest activity in early-luteal stage. In addition to a 32 kDa uterus-specific gelatinase band detected in both non-pregnant and pregnant ULFs, the pregnant ULF displayed three new gelatinase bands of 86, 78, and 57 kDa. Western blot technique confirmed the presence of MMP-2 (54 kDa), MMP-9 (76/73 kDa), TIMP-1 (32 kDa), TIMP-2(20 kDa), and two molecular weight forms (31 and 22 kDa) of TIMP-3 in buffalo ULF with varying band intensities. Highest MMP-2 and MMP-9 activities were observed in follicular and early-luteal stage ULFs, respectively. Highest TIMP-1 activity was observed in early-luteal ULF. Interestingly, TIMP-2 activity was only detected in mid-luteal, late-luteal, and follicular stage ULFs with significantly increasing intensities. Highest activities of 31 and 22 kDa TIMP-3 were associated with late-luteal and early-luteal stage ULFs, respectively. The varied activities of MMPs and TIMPs in buffalo ULF during the estrous cycle and early pregnancy might be a reflection of dynamic structural remodeling of the endometrium and/or developing conceptus.

Estrogen-induced uterine abnormalities in TIMP-1 deficient mice are associated with elevated plasmin activity and reduced expression of the novel uterine plasmin protease inhibitor serpinb7

Tissue inhibitor of metalloproteinase-1 (TIMP-1) is a multifunctional protein capable of regulating a variety of biological processes in a wide array of tissue and cell types. We have previously demonstrated that TIMP-1 deficient mice exhibit alterations in normal uterine morphology and physiology. Most notably, absence of TIMP-1 is associated with an altered uterine phenotype characterized by profound branching of the uterine lumen and altered adenogenesis. To begin to assess the mechanism by which TIMP-1 may control these uterine events, we utilized steroid-treated ovariectomized wild-type and TIMP-1 null mice exposed to estrogen for 72 hr. Administration of estrogen to TIMP-1 deficient mice resulted in development of an abnormal uterine histo-architecture characterized by increased endometrial gland density, luminal epithelial cell height, and abnormal lumen structure. To determine the mediators which may contribute to the abnormal uterine morphology in the TIMP-1 deficient mice, cDNA microarray analysis was performed. Analysis revealed that expression of two plasmin inhibitors (serpbinb2 and serbinb7) was significantly reduced in the TIMP-1 null mice. Associated with the reduction in expression of these inhibitors was a significant increase in plasmin activity. Localization of the novel uterine serpinb7 revealed that expression was confined to the luminal and glandular epithelial cells. Further, expression of uterine serpinb7 was decreased by estrogen and showed an inverse relationship with plasmin activity. We conclude from these studies that in addition to controlling MMP activity, TIMP-1 may also control activity of serine proteases through modulation of serine protease inhibitors such as serpinb7.

The Macaque Endometrium, with Special Reference to the Cynomolgus Monkey (Macaca fascicularis)

The macaque endometrium undergoes dramatic morphologic and functional changes during the menstrual cycle that are nearly identical to those of the human endometrium. The sequential events that take place in the endometrium are mainly driven by the ovarian steroids and their respective receptors. To be able to interpret the changes and effects induced by mammalian or synthetic hormones and other compounds that could have influence on the hormonal status of the animal, a thorough knowledge of the anatomy, physiology, and histology of the cyclic hormone-mediated processes within the endometrium is indispensable. In this paper we give an overview of uterine growth and development, anatomy, basic histology, aging, spontaneous pathology, and the techniques to study the endometrium in-life. In addtion, a comprehensive description of the receptor-mediated, hormone-driven morphological changes during the menstrual cycle in the cynomolgus monkey (Macaca fascicularis) is given. Where possible, differences between the macaque and human endometria are discussed.

Competing Interests: This article was sponsored by Covance Inc. and Schering-Plough. Gerhard F. Weinbauer and Eberhard Buse are employed by Covance Inc. Eric Van Esch is employed by Schering-Plough. No other competing interests were declared.

Assessment of menstruation in the vervet (Cercopithecus aethiops)

Vervet monkeys (Chlorocebus aethiops) are Old World nonhumans that display attenuated menstruation that requires detection by vaginal swab. The physiology underlying attenuated menstruation in this species has not been previously studied. To fill this gap, we evaluated endometrial cell proliferation, steroid receptor localization and expression of menstruation-associated matrix metalloproteinase (MMP) enzymes in vervets during natural and artificial menstrual cycles. The artificial cycles were induced by sequentially treating ovariectomized animals with estradiol (E(2)) and progesterone (P). Because menstrual flow is exceptionally light in this species, menses was detected by vaginal swab. We found that both natural and artificially cycled animals menstruated 3-5 days after the decline of P at the end of the cycle. As in other primates, P withdrawal at the end of artificial cycles triggered endometrial expression of MMPs, including MMP-1, 2, 3, 7, 10, 11, 13 and 26 transcripts. In both the natural and artificial menstrual cycle, menstrual sloughing was restricted to the upper one-fourth of the endometrium, and MMP-1 and 2 were strongly expressed by the stroma of the sloughing zone. MMP-7 was localized in the endometrial glands during late menses. As in macaques, epithelial cell proliferation was localized to the functionalis zone during the estrogen-dominated proliferative phase and to the basalis zone glands during the P-dominated secretory phase. Regulation of estrogen and progestin (or estradiol and progesterone) receptors was similar to that reported for macaques. Because strong similarities exist between the endometrium of vervets, macaques and women, we conclude that vervets can provide a useful animal model for studies on hormone regulation of menstruation.

Regulation of homeobox A10 expression in the primate endometrium by progesterone and embryonic stimuli

Homeobox A10 (HOXA10), a member of abdominal B subclass of homeobox genes, is responsible for uterine homeosis during development. Intriguingly, in the adult murine uterus, HOXA10 has been demonstrated to play important roles in receptivity, embryo implantation, and decidualization. However, the roles of HOXA10 in the primate endometrium are not known. To gain insights into the roles of HOXA10 in the primate endometrium, its expression was studied in the endometria of bonnet monkey (Macaca radiata) in the receptive phase and also in the endometria of monkeys treated with antiprogestin onapristone (ZK98.299) or in conception cycle where the presence of preimplantation stage blastocyst was verified. In addition, the mRNA expression ofHOXA11and insulin-like growth factor-binding protein 1 (IGFBP1) was evaluated by real-time PCR in these animals.The results revealed that HOXA10 in the luteal phase primate endometrium is differentially expressed in the functionalis and the basalis zones, which is modulatedin vivoby progesterone and also by the signals from the incoming embryo suggesting the involvement ofHOXA10in the process of establishment of pregnancy in primates. In addition, the results also demonstrated that the expression ofIGFBP1but notHOXA11is coregulated withHOXA10in the endometria of these animals. The pattern of changes in the expression of HOXA10 in response to the two stimuli suggests that endometrial receptivity and implantation not only requires a synchrony of maternal and embryonic signaling on endometrial cells in the primates but there also exists a controlled differential response among the cells of various uterine compartments.

Effect of mifepristone on endometrial matrix metalloproteinase expression and leukocyte abundance in new medroxyprogesterone acetate users

PURPOSE

This double-blind, placebo-controlled study was conducted to evaluate the molecular mechanism of mifepristone controlling breakthrough bleeding (BTB) in new depot-medroxyprogesterone acetate (DMPA) users.

METHOD

A total of 50 regularly cycling women who were new starters of DMPA were randomized to receive 50 mg of mifepristone or placebo once every 14 days for six cycles. Endometrial biopsies were obtained on each patient before, during and after treatment. Endometrial matrix metalloproteinase 1 (MMP-1) and MMP-9 protein and mRNA were determined by immunohistochemistry and real-time PCR, respectively. The number of T lymphocytes (CD3-positive) and mast cells (mast tryptase-positive) was evaluated by immunohistochemistry.

RESULTS

MMP-1, MMP-9, CD3-positive and mast tryptase-positive cells increased following the DMPA treatment. Addition of mifepristone to DMPA-exposed endometrium for 1 week significantly decreased stromal MMP-9 expression and numbers of CD3-positive and mast tryptase-positive cells.

CONCLUSION

The decreased rates of BTB in new users of DMPA by mifepristone are associated with decreased MMP-1 and MMP-9 expression and fewer mast and T cells.

Estrogen decrease in tight junctional resistance involves matrix-metalloproteinase-7-mediated remodeling of occludin

Estrogen modulates tight junctional resistance through estrogen receptor-alpha-mediated remodeling of occludin. The objective of the study was to understand the mechanisms involved. Experiments using human normal vaginal-cervical epithelial cells showed that human normal vaginal-cervical epithelial cells secrete constitutively matrix-metalloproteinase-7 (MMP-7) into the luminal solution and that MMP-7 is necessary and sufficient to produce estrogen decrease of tight junctional resistance and remodeling of occludin. Treatment with estrogen stimulated activation of the pro-MMP-7 intracellularly and augmented secretion of the activated MMP-7 form. Steady-state levels of MMP-7 mRNA and protein were not affected by estrogen. Estrogen modulated phosphorylation of the MMP-7, but the changes were most likely secondary to changes in cellular MMP-7 mass. Estrogen increased coimmunoreactivity of MMP-7 with the Golgi protein GPP130. Tunicamycin and brefeldin-A had no effect on cellular MMP-7 but monensin (inhibitor of Golgi traffic) blocked estrogen effects, suggesting estrogen site of action is at the Golgi system. Estrogen increased generalized secretory activity, including of luminal exocytosis of polycarbohydrates. However, estrogen increased coimmunoreactivity of MMP-7 with synaptosomal-associated protein of 25 kDa in apical membranes, suggesting soluble N-ethylmaleimide sensitive fusion factor attachment protein receptor-facilitated exocytosis of MMP-7. Treatment with the vesicular-ATPase inhibitor bafilomycin A(1) inhibited activation of MMP-7. These data suggest that estrogen up-regulates activation of the MMP-7 intracellularly, at the level of Golgi, and augments secretion of activated MMP-7 through soluble N-ethylmaleimide sensitive fusion factor attachment protein receptor-dependent exocytosis. On the other hand, estrogen acidification of the luminal solution would tend to alkalinize exocytotic vesicles and may lead to decreased activation of the MMP-7. These mechanisms acting in concert could be important for regulation and control of estrogen modulation of paracellular permeability in vivo.

Increased expression of matrix metalloproteinase-9 in the eutopic endometrial tissue of women with endometriosis

BACKGROUND

Endometriosis is a disease where endometrial tissue implants in ectopic locations. Remodelling of the extracellular matrix (ECM) is a prerequisite for the implantation of this tissue to be possible.

METHODS

In this study, we detected immunoreactive matrix metalloproteinase-9 (MMP-9) throughout endometrial tissue and identified von Willebrand factor (vWF)-positive endothelial cells, CD45-positive leukocytes, CD3-positive T lymphocytes and CD68-positive macrophages as cells expressing MMP-9 in the stroma.

RESULTS

We found an increased expression of MMP-9 in the uterine endometrial tissue of women with endometriosis, as assessed by zymography and enzyme-linked immunosorbent assay (ELISA) (P < 0.05). However, RT-PCR did not show a statistically significant increase in MMP-9 mRNA expression in these tissues (P = 0.14). There was no significant difference between women with and without endometriosis in the expression of tissue inhibitor of MMPs (TIMP)-1, a known natural inhibitor of the pro- and active forms of MMP-9, whether tested by ELISA or by RT-PCR (P = 0.46 and 0.37, respectively). Interestingly, the ratio of MMP-9/TIMP-1 expression was significantly higher in women with endometriosis than in normal women both at the protein and the mRNA levels (P < 0.05).

CONCLUSION

These findings make plausible the involvement of MMP-9/TIMP-1 imbalance in the invasiveness of the endometrial tissue of patients with endometriosis and the ectopic development of the disease.

Regulation of human endometrial function: mechanisms relevant to uterine bleeding

This review focuses on the complex events that occur in the endometrium after progesterone is withdrawn (or blocked) and menstrual bleeding ensues. A detailed understanding of these local mechanisms will enhance our knowledge of disturbed endometrial/uterine function--including problems with excessively heavy menstrual bleeding, endometriosis and breakthrough bleeding with progestin only contraception. The development of novel strategies to manage these clinically significant problems depends on such new understanding as does the development of new contraceptives which avoid the endometrial side effect of breakthrough bleeding.

A critical period of progesterone withdrawal precedes menstruation in macaques

Macaques are menstruating nonhuman primates that provide important animal models for studies of hormonal regulation in the uterus. In women and macaques the decline of progesterone (P) at the end of the cycle triggers endometrial expression of a variety of matrix metalloproteinase (MMP) enzymes that participate in tissue breakdown and menstrual sloughing. To determine the minimal duration of P withdrawal required to induce menses, we assessed the effects of adding P back at various time points after P withdrawal on both frank bleeding patterns and endometrial MMP expression. Artificial menstrual cycles were induced by treating the animals sequentially with implants releasing estradiol (E2) and progesterone (P). To assess bleeding patterns, P implants were removed at the end of a cycle and then added back at 12, 24, 30, 36, 40, 48, 60, or 72 hours (h) after the initial P withdrawal. Observational analysis of frank bleeding patterns showed that P replacement at 12 and 24 h blocked menses, replacement at 36 h reduced menses but replacement after 36 h failed to block menses. These data indicate that in macaques, a critical period of P withdrawal exists and lasts approximately 36 h. In other similarly cycled animals, we withdrew P and then added P back either during (12-24 h) or after (48 h) the critical period, removed the uterus 24 h after P add back and evaluated endometrial MMP expression. Immunocytochemistry showed that replacement of P during the critical period suppressed MMP-1, -2 and -3 expression along with menses, but replacement of P at 48 h, which failed to suppress mense, suppressed MMP-1 and MMP-3 but did not block MMP-2. We concluded that upregulation of MMPs is essential to menses induction, but that after the critical period, menses will occur even if some MMPs are experimentally blocked.

Steroidal regulation of uterine edema and tissue inhibitors of metalloproteinase (TIMP)-3 messenger RNA expression is altered in TIMP-1-deficient mice

Tissue inhibitors of metalloproteinases (TIMPs) are expressed within the uteri of virtually all species where they are postulated to control extracellular matrix turnover, cellular apoptosis, and proliferation. The objective of the current study was to examine the steroidal regulation of uterine TIMP expression and to determine the potential role of the TIMP-1 gene product in this regulation. To accomplish these goals, ovariectomized female TIMP-1 wild-type and null mice were treated with estradiol, progesterone, or estradiol and progesterone and killed at various times after steroid administration. Estradiol induced a significant reduction in uterine TIMP-3 expression in wild-type mice at 8 and 24 h post-steroid administration, but the ability of this steroid to decrease TIMP-3 expression was impaired in the uteri of TIMP-1 null mice. Further, estrogen-induced uterine wet-weight gain/edema was enhanced in the TIMP-1 null mice, and the antiestrogen compound ICI 182780 or progesterone could only partially block this estrogenic effect. It is concluded from this study that steroidal modulation of uterine TIMP-3 expression and regulation of wet-weight gain/edema are altered in TIMP-1 null mice. These observations suggest that steroids induce uterine TIMP-1 expression and, in turn, that TIMP-1 influences TIMP-3 mRNA expression and uterine edema.

Hormonal regulation and localization of estrogen, progestin and androgen receptors in the endometrium of nonhuman primates: effects of progesterone receptor antagonists

This article reviews the effects of estradiol (E(2)), progesterone (P) and P receptor antagonists (PA) on the rhesus macaque endometrium. Ovariectomized macaques can be treated with implants of estradiol (E(2)) and P to induce precisely controlled, artificial menstrual cycles. During these cycles, treatment with E(2) alone induces an artificial proliferative phase marked by extensive endometrial epithelial cell proliferation and increased expression of stromal and epithelial estrogen receptor (ER) and P receptor (PR). Androgen receptor (AR) is also upregulated by E(2) but is expressed only by the endometrial stroma. Progesterone acts on the E(2) primed endometrium to induce secretory differentiation and causes suppression of epithelial and stromal ER, epithelial PR, and stromal AR in the functionalis zone. However, epithelial ER and PR are retained in the basalis zone during the secretory phase. When potent P antagonists (PA) are administered acutely at the end of an E(2) + P induced cycle, menses typically ensues similar to P withdrawal at the end of the menstrual cycle. When PAs are administered chronically there is significant blockage of all P- dependent effects including upregulation of ER, PR and AR and suppression of glandular secretory function. However, chronic PA administration also inhibits estrogen-dependent endometrial cell proliferation and growth. This endometrial antiproliferative effect is the basis of the clinical use of PA to control various diseases such as endometriosis.

Antiprogestins as a model for progesterone withdrawal

The key physiological function of the endometrium is preparation for implantation; and in the absence of pregnancy, menstruation and repair. The withdrawal of progesterone is the initiating factor for breakdown of the endometrium. The modulation of sex steroid expression and function with pharmacological agents has provided an invaluable tool for studying the functional responses of the endometrium to sex steroids and their withdrawal. By administration of the antiprogestin mifepristone, it is possible to mimic progesterone withdrawal and study local events in early pregnancy decidua that may play a role in the process of early pregnancy failure. Our data indicate that antagonism of progesterone action at the receptor level results in an up-regulation of key local inflammatory mediators, including NF-kappaB, interleukin-8 (IL-8), monocyte chemotactic peptide-1 (MCP-1), cyclooxygenase 2 (COX-2) and others in decidua. Bleeding induced by mifepristone in the mid-luteal phase of the cycle is associated with changes in the endometrium similar to those that precede spontaneous menstruation including up-regulation of COX-2 and down-regulation of PGDH. Administration of antagonists of progesterone provide an excellent model to study the mechanisms involved in spontaneous and induced abortion as well as providing information which may help devise strategies for treating breakthrough bleeding associated with hormonal contraception.

Expression pattern of metalloproteinases and tissue inhibitors of matrix-metalloproteinases in cycling human endometrium

The cyclic growth, differentiation, and cell death of endometrium represents the most dynamic example of steroid-driven tissue turnover in human adults. Key effectors in these processes-matrix metalloproteinases (MMPs) and their specific inhibitors (TIMPs)-are regulated by ovarian steroids and, locally, by cytokines. We used reverse transcription-polymerase chain reaction to evaluate the expression of both transcriptionally regulated molecules such as estrogen receptor-alpha, progesterone receptor, and prolactin and a large array of MMPs and TIMPs (MMP-1, -2, -3, -7, -8, -9, -11, -12, -19, -26, MT1-MMP, MT2-MMP, MT3-MMP, TIMP-1, -2, -3). Altogether, three distinct patterns of MMP and two patterns of TIMP expression were detected in cycling endometrium: 1). MMPs restricted to the menstrual period (MMPs-1, -3, -8, -9, -12); 2). MMPs and TIMPs expressed throughout the cycle (MMP-2, MT1-MMP, MT2-MMP, MMP-19, TIMP-1, and TIMP-2); 3). MMPs predominantly expressed during the proliferative phase (MMP-7, MMP-11, MMP-26, and MT3-MMP); and 4). TIMP-3, which, contrary to the other TIMPs, shows significant modulations, with maximum expression during the late secretory and menstrual phases. These specific patterns of MMP expression associated with each phase of the cycle may point to specific roles in the processes of menstruation, housekeeping activities, angiogenesis, tissue growth, and extracellular matrix remodeling.

The matrix metalloproteinase system: changes, regulation, and impact throughout the ovarian and uterine reproductive cycle

The ovary and uterus undergo extensive tissue remodeling throughout each reproductive cycle. This remodeling of the extracellular environment is dependent upon the cyclic hormonal changes associated with each estrous or menstrual cycle. In the ovary, tissue remodeling is requisite for growth and expansion of the follicle, breakdown of the follicular wall during the ovulatory process, transformation of the postovulatory follicle into the corpus luteum, as well as the structural dissolution of the corpus luteum during luteal regression. In the uterus, there is extraordinary turnover of the endometrial connective tissue matrix during each menstrual cycle. This turnover encompasses the complete breakdown and loss of this layer, followed by its subsequent regrowth. With implantation, extensive remodeling of the uterus occurs to support placentation. These dynamic changes in the ovarian and uterine extracellular architecture are regulated, in part, by the matrix metalloproteinase (MMP) system. The MMP system acts to control connective tissue remodeling processes throughout the body and is comprised of both a proteolytic component, the MMPs, and a regulatory component, the associated tissue inhibitors of metalloproteinases. The current review will highlight the key features of the MMPs and tissue inhibitors of metalloproteinases, focus on the changes and regulation of the MMP system that take place throughout the estrous and menstrual cycles, and address the impact of the dynamic tissue remodeling processes on ovarian and uterine physiology.

Mechanisms involved in the evolution of progestin resistance in human endometrial hyperplasia--precursor of endometrial cancer

BACKGROUND

Successful treatment of endometrial hyperplasia with progestins is commonly accompanied by the finding of an inactive or suppressed endometrium after therapy. However, approximately 30% of the endometrial hyperplasia cases do not respond to progestins and hyperplastic glands persist. The Fas/FasL system is known to play a role in tissue remodeling as a result of changes in menstrual hormone levels. The aims of this study are to examine Fas/FasL expression in endometrial hyperplasia of pre- and postprogestin treatment samples and to study the Fas/FasL regulation in vitro with Ishikawa cells after progestin stimulation.

DESIGN

Pre- and posttreatment paraffin-embedded endometrial hyperplasia tissue samples from 26 women were examined by immunohistochemistry for changes in Fas/FasL expression related to the administration of progestins. Among 26 patients, 18 were successfully treated with progestins and 8 failed treatment. Fas/ FasL positivity was defined by the presence of 10% or more immunoreactive epithelial cells in each specimen. In positive cases, a percentage or an immunoscore of immunoreactive cells was given by counting 500 cells. Cell viability was evaluated by the MTT assay. The in vitro effects of progesterone on Fas/FasL expression and apoptosis in Ishikawa cells were examined by using Western blot and TUNEL assays, respectively.

RESULTS

Fas immunoreactivity was present in 4/26 (15%) preprogestin cases with an average of 16% of the epithelial cells expressing Fas. FasL was expressed in 21/26 (80%) pretreatment cases with an average of 42% of the hyperplastic glandular cells being positive. In postprogestin cases, an increase of Fas expression (14/18, 77%) with an average of 47% stained cells was seen in responders (P < 0.001), while FasL was found in 16/18 (89%) responders with an average of 65% of cells positive (P = 0.587). In nonresponders, no significant changes in Fas/FasL expression were detected compared to pretreatment samples. With in vitro Ishikawa cells, a slight increase (10-20%) of Fas and FasL protein expression was detected after 24 h of progesterone treatment, but a more significant increase (220-343%) of both Fas and FasL expression was found after 48 h of withdrawing progesterone, which parallels apoptotic activity.

CONCLUSIONS

The Fas/FasL system may be involved in the development of endometrial hyperplasia. Part of the molecular mechanisms of progestin therapy for endometrial hyperplasia is through upregulation of Fas/FasL expression. Dysregulation of Fas/FasL expression in hyperplastic endometrium may be part of the molecular mechanisms for nonresponders to progestin treatment. Intermittent, rather than continuous, progestin treatment may be more effective clinically for the treatment of endometrial hyperplasia.

Regulation and function of LEFTY-A/EBAF in the human endometrium. mRNA expression during the menstrual cycle, control by progesterone, and effect on matrix metalloprotineases

The human endometrium is a unique tissue that is periodically shed during menstruation. Although overall triggered by ovarian steroids withdrawal, menstrual induction of matrix metalloproteinases (MMPs) and resulting tissue breakdown are focal responses, pointing to additional local modulators. LEFTY-A, a novel member of the transforming growth factor-beta family identified originally as an endometrial bleeding-associated factor (EBAF), is a candidate for this local control. We measured LEFTY-A and beta-ACTIN mRNA concentration during the menstrual cycle in vivo and found that their ratio was dramatically ( approximately 100-fold) increased at the perimenstrual phase. A similar increase was seen when proliferative explants were cultured for 24 h in the absence of ovarian steroids; this was followed by spontaneous production of proMMP-1, -3, and -9. Both responses were inhibited by progesterone. Moreover, addition of recombinant LEFTY-A to proliferative explants was sufficient to stimulate the expression of proMMP-3 and -7; this response was also blocked by ovarian steroids. Collectively, these data indicate that LEFTY-A may provide a crucial signal for endometrial breakdown and bleeding by triggering expression of several MMPs. Progesterone appears to exert a dual block, upstream by inhibiting LEFTY-A expression and downstream by suppressing its stimulatory effect on MMPs.

Expression of gelatinases and their tissue inhibitors in rat corpus luteum during pregnancy and postpartum

Extensive tissue remodeling occurs in the corpus luteum (CL) during both formation and luteolysis. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are believed to play pivotal roles in these processes. In the present study, to evaluate the potential roles of matrix degrading proteases in luteal development and regression, we examined gelatinases and TIMP-1, -2, -3 mRNA expressions, as well as gelatinase activity in rat CL during pregnancy and postpartum using Northern blot, in situ hybridization, and gelatin zymography, respectively. The results showed that MMP-2 mRNA was only expressed at the early stages of pregnancy; TIMP-2 mRNA was highly expressed at the early and late pregnancy and day 1 postpartum, but could not be detected during the mid-phase of pregnancy; TIMP-3 mRNA expression was abundant during early pregnancy and peaked at day 7, but was absent from other time points examined. MMP-9 and TIMP-1 mRNAs in rat CL were below detectable level in the current study. Furthermore, the active MMP-2 was only present during the early stages of pregnancy, and no MMP-9 activity was observed in the zymogram. Taken together, our results suggest that MMP-2 and TIMP-3 may have functional roles in rat luteal formation, while TIMP-2 may be implicated in both formation and regression of the pregnant CL.

Vascular proliferation and vascular endothelial growth factor expression in the rhesus macaque endometrium

The relationship between vascular endothelial growth factor (VEGF) expression and the pattern of vascular proliferation in the rhesus macaque endometrium has not been studied. In this report, we used in situ hybridization to evaluate VEGF, VEGF receptor type 1 and VEGF receptor type 2 mRNA expression during hormonally regulated menstrual cycles in ovariectomized macaques. Proliferating endothelial cells were identified by a double immunocytochemistry procedure that detected Ki-67 antigen and von Willebrand factor in the same endothelial cells. One and 2 d after progesterone withdrawal (premenstrual), VEGF mRNA was up-regulated in the glands and stroma of the superficial endometrial zones, a finding that supports our previous suggestion that VEGF may play a role in the menstrual induction cascade. During the postmenstrual repair phase, the healing surface epithelium showed a further, dramatic increase in expression of VEGF mRNA, accompanied by strong increases in signals for VEGF receptor types 1 and 2 in multiple profiles of small blood vessels immediately below the surface epithelium. This finding implicates VEGF in the early angiogenic processes associated with endometrial healing and regeneration. Vascular endothelial proliferation persisted throughout the cycle in the upper endometrial zones and showed a dramatic estrogen- dependent peak during the midproliferative phase. This proliferative peak coincided with a peak in VEGF expression in the endometrial stroma. Endothelial proliferation was also significantly correlated with the degree of stromal VEGF expression during the proliferative and secretory stages of the cycle. These results implicate VEGF of stromal origin in endometrial vascular proliferation.

Circulating ovarian steroids and endometrial matrix metalloproteinases (MMPs)

Recent studies strongly suggest that matrix metalloproteinases (MMPs) play a key role in the initiation of menstrual bleeding in the human endometrium upon the fall of ovarian steroid serum concentrations by inducing the degradation of the extracellular matrix of this mucosa. MMPs are also involved in abnormal endometrial bleeding and have been identified in endometriotic foci. In all cases, they are associated with areas of extracellular matrix breakdown. This paper reviews the literature on the regulation by estradiol and progesterone of the expression and activation of MMPs, and of the expression of their tissue inhibitors (TIMPs), (i) in the endometrium in situ during normal cycle, (ii) during artificial cycles in spayed monkeys, and (iii) in cultures of endometrial explants or purified cells. Whereas progesterone consistently decreases the activity of endometrial MMPs, its effects vary in intensity, duration, and pattern between MMPs as well as among experimental systems. The contribution and limitations of the various investigations are therefore discussed. The focal heterogeneity points to additional local controls of the expression and activation of MMPs in human endometrium, acting beyond the general inhibitory role of progesterone, for example, by cytokines. Focal changes in type or abundance of sex steroid receptors also could be responsible for spatial variation in the expression of MMPs in the endometrium and endometriotic lesions.

Premenstrual and menstrual changes in the macaque and human endometrium: relevance to endometriosis

According to current theory, endometriosis is initiated during retrograde menstruation when menstrual fragments flow out of the fimbriated end of the fallopian tubes and become established on the ovarian surface or other sites in the peritoneal cavity. In recent years, new data have accumulated on the properties of menstruating tissue itself, and several laboratories agree that this tissue is rich in matrix metalloproteinases (MMPs) that may facilitate endometriotic implantation. Recently, we found that vascular endothelial growth factor (VEGF) and its receptor VEGFR-2 (KDR) were dramatically upregulated in the stromal cells of the superficial endometrial zones by progesterone (P) withdrawal during the premenstrual phase. A unique role of VEGF at this stage of the cycle may be to stimulate MMP expression in stromal cells because VEGF, KDR, and MMPs were all coordinately induced in these cells in the superficial zone of the primate endometrium by P withdrawal. The rich content of MMPs and VEGF in the menstrual fragments could facilitate attachment and angiogenesis of menstrual fragments in ectopic sites. In addition, a variety of chemokines, cytokines, and cellular regulators are induced by P withdrawal in the premenstrual human endometrium. These include NFKB, prostaglandins, interleukin-8 (IL-8), cyclooxygenase-2 (COX-2), and monocyte chemotactic peptide-1 (MCP-1), among others. The perivascular expression of several of these factors may facilitate the rapid invasion of leukocytes into the endometrium, especially in the superficial zones. Consequently, menstrual fragments may be rich in IL-8 and MCP-1, both of which would add to the angiogenic potential of such fragments in ectopic sites. In sum, menstrual tissue is rich in VEGF, KDR, MMPs, leukocytes, chemokines, cytokines, and prostaglandins, all factors that may facilitate attachment and angiogenesis when menstrual fragments exit from the tubes and implant on pelvic sites. Additional research on these and other factors in premenstrual and menstrual endometrium may deepen our understanding of both the establishment and progression of this debilitating disease.

Disruption of the tissue inhibitor of metalloproteinase-1 gene in reproductive-age female mice is associated with estrous cycle stage-specific increases in stromelysin messenger RNA expression and activity

Tissue inhibitors of metalloproteinases (TIMPs) are expressed in the uteri of virtually all species, yet the precise role of these factors in uterine physiology is uncertain. It has been previously demonstrated that disruption of the TIMP-1 gene product in vivo results in altered reproductive cycles and an aberrant uterine phenotype. Because this phenotype may be due to an elevation in uterine matrix metalloproteinase (MMP) activity, the purpose of the following experiments was to identify which uterine MMPs may have their expression altered in response to disruption of the TIMP-1 gene. Mature female TIMP-1 wild-type and null mice were killed during each stage of the estrous cycle, and uterine MMP activity and transcript expression were assessed. Disruption of the TIMP-1 gene product was associated with an increase in total uterine protease activity. Gel zymography further revealed that uterine stromelysin (stromelysin-1, -2, and -3) activity was significantly increased in the TIMP-1 null mice, whereas Northern blot analysis indicated that an up-regulation of stromelysin-1 and -3 mRNA expression may contribute to this increase in activity. It is concluded from this study that TIMP-1 plays a pivotal role in regulating uterine stromelysins both at the level of protease activity and the level of transcript expression.

The endocrinology of menstruation--a role for the immune system

The human endometrium displays characteristic features, both structural and functional, across the menstrual cycle. It is the sex steroid hormones, oestrogen and progesterone, that drive the endometrium through the different phases of the cycle. Oestrogen and progesterone act sequentially to regulate cellular concentrations of their respective receptors, this interaction initiates gene transcription. Thereafter a cascade of local events prepares the endometrium for implantation, but in the absence of pregnancy, progesterone withdrawal leads to menstruation and cyclic repair. Withdrawal of progesterone from an oestrogen-progesterone primed endometrium is the initiating event for the cascade of molecular and cellular interactions that result in menstruation. Progesterone withdrawal first affects cells with progesterone receptors. Early events in the menstrual process are vasoconstriction and cytokine up-regulation. The activation of lytic mechanisms is a later event and involves cells that may lack progesterone receptors, for example, uterine leucocytes and epithelial cells. Hence progesterone withdrawal results in a local increase of inflammatory mediators and the enzymes responsible for tissue breakdown. The total complex of local factors implicated in normal menstrual and aberrant menstrual bleeding are yet to be fully defined.

Expression of matrix metalloproteinase-2, -9, -14, and tissue inhibitors of metalloproteinase-1, -2, -3 in the endometrium and placenta of rhesus monkey (Macaca mulatta) during early pregnancy

The extracellular matrix proteolytic machinery has long been recognized as one of the most important mechanisms for regulating trophoblast invasion. Matrix metalloproteinases (MMPs) are a group of proteases involved in this process, and their activities are regulated by tissue inhibitors of MMPs (TIMPs). In this study, we collected rhesus monkey uteri on Days 12, 18, and 26 of pregnancy and examined the mRNA expression of MMP-2, -9, -14, and TIMP-1, -2, -3, as well as the activities of MMP-2 and -9 by using in situ hybridization and gelatin zymography, respectively. The results showed that MMP-2 and -9 were expressed earlier than MMP-14 and TIMPs in the pregnant endometrium. MMP-14 and TIMP-2 mRNAs appeared in perivascular decidual cells earlier than MMP-2 mRNA. On Day 26 of pregnancy, placental villi expressed little MMP-2, -14, and TIMP transcripts but abundant MMP-9 mRNA. Furthermore, MMP-2, -9, -14, and TIMP-1, -2, -3 were highly expressed on the fetal-maternal border but were absent in the myometrium. TIMP-3 mRNA in the endometrium was specifically localized to some cells lining the outer membrane of several groups of arterioles. Combined with the results obtained by gelatin zymography, we found that active MMP-2 existed in the endometrium throughout these three phases, while MMP-9 showed considerable activities only on Days 18 and 26 of pregnancy. The data suggest key roles for MMP-2 and -9 in invasion of trophoblast cells into the endometrium and the development of the placenta and might indicate that these processes are regulated by MMP-14 and TIMP-1, -2, and -3.