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STUDY QUESTION Do obese levels of advanced glycation end products (AGEs) within the uterine cavity detrimentally alter tissue function in embryo implantation and placental development? SUMMARY ANSWER Obese levels of AGEs activate inflammatory signaling (p65 NFκB) within endometrial epithelial cells and alter their function, cause endoplasmic reticulum (ER) stress in endometrial stromal cells and impair decidualization, compromise implantation of blastocyst mimics and inhibit trophoblast invasion. WHAT IS KNOWN ALREADY Obese women experience a higher incidence of infertility, recurrent miscarriage and pregnancy complications compared with lean women. Oocyte donation cycles suggest a detrimental uterine environment plays a role in these outcomes. STUDY DESIGN, SIZE, DURATION Uterine lavage and tissues from lean (BMI 19.5-24.9, n = 17) and obese (BMI > 30, n = 16) women examined. Cell culture experiments utilizing human endometrial epithelial, trophectoderm and trophoblast cell lines and primary human stromal cells used to examine the functional impact of obese levels of AGEs. PARTICIPANTS/MATERIALS, SETTING, METHODS Levels of AGEs examined within uterine lavage assessed by ELISA to determine differences between lean and obese women. Expression and localization of AGEs, receptor for AGEs (RAGE) and NFκB within endometrial tissues obtained from lean and obese women determined by immunohistochemistry. Endometrial epithelial cells (ECC-1), primary human stromal cells and trophoblast cells (HTR8-SVneo) treated with lean (2000 nmol/mol lysine) or obese (8000 nmol/mol lysine) uterine levels of AGEs and p65 NFκB (western immunoblot), real-time adhesion, proliferation migration and invasion (xCelligence real-time cell function analysis), decidualization (cell morphology and prolactin release), ER stress (western immunoblot for p-PERK) determined. Co-cultures of endometrial epithelial cells and blastocyst mimics (trophectoderm spheroids) similarly treated with lean or obese uterine levels of AGEs to determine their impact on embryo implantation. MAIN RESULTS AND THE ROLE OF CHANCE AGEs were significantly elevated (P = 0.004) within the obese (6503.59 μmol/mol lysine) versus lean (2165.88 μmol/mol lysine) uterine cavity (uterine lavage) with increased immunostaining for AGEs, RAGE and NFkB within obese endometrial tissues during the proliferative phase of the menstrual cycle. Obese uterine levels of AGEs inhibited adhesion and proliferation of endometrial epithelial (ECC-1) cells compared to treatment with lean uterine levels of AGEs. Obese uterine AGE levels impacted primary human endometrial stromal cell decidualization and activated ER stress within these cells. Obese uterine levels of AGEs also inhibited trophectodermal spheroid adhesion to hormonally primed endometrial epithelial cells and trophoblast cell line HTR8/SV-neo invasion. LARGE SCALE DATA N/A. LIMITATIONS REASONS FOR CAUTION Mechanistic studies are performed in vitro and may not completely recapitulate cell function in vivo. WIDER IMPLICATIONS OF THE FINDINGS These data corroborate clinical data suggesting the presence of an altered uterine environment in obese women and demonstrate that elevated uterine levels of AGEs within these women may detrimentally impact endometrial function, embryo implantation and placental development. Uterine AGE assessment in infertility work up may prove useful in determining underlying causes of infertility. AGEs can be targeted pharmacologically and such treatments may prove effective in improving reproductive complications experience by obese women. STUDY FUNDING/COMPETING INTEREST(S) Supported by NHMRC Fellowship (#1002028 to L.A.S.), and the Victorian Government's Operational Infrastructure Support Program. MTC is supported by a JDRF Australia Clinical Research Network Career Development Award. The authors have declared that no conflict of interest exists.

BACKGROUND Successful blastocyst implantation requires the differentiation of human endometrial stromal cells (HESC), a process known as decidualization. Activin A, a transforming growth factor beta (TGFbeta) superfamily member, enhances HESC decidualization and localizes to decidual cells in human endometrium. Other TGFbeta superfamily members, including BMP2, BMP4, BMP7, GDF5, GDF8, GDF11, TGFbetas and Nodal, may also play a role during decidualization. This study aimed to identify these TGFbeta family members in human endometrium, and to determine whether they are involved in human decidualization. METHODS Protein localization of TGFbeta family members was examined in secretory phase human endometrium and first trimester decidua by immunohistochemistry. mRNA expression was examined in HESC. Activin inhibitors (Activin-M108A/SB431542) with differing specificities for the other TGFbeta members under consideration were applied during HESC decidualization in vitro. The secretion levels of potential TGFbeta superfamily members were measured during decidualization, and recombinant proteins added to examine their effect. RESULTS This study has identified BMP2, BMP4, BMP7, GDF5, GDF8 and GDF11 but not Nodal in secretory phase human endometrium, but only BMP2, GDF5 and TGFbeta1 protein were detected in decidual cells. All ligands except Nodal were expressed by cultured HESC. Both inhibitors significantly reduced decidualization validating the role of activin, but potentially also other TGFbeta members, during decidualization. BMP2 and TGFbeta1 secretion increased during HESC decidualisation and exogenous administration of these proteins significantly enhanced decidualization in vitro. CONCLUSIONS Like activin, BMP2 and TGFbeta1 are likely to be involved in HESC decidualization. This is the first study to identify and localize BMP4, BMP7, GDF5, GDF8 and GDF11 in secretory phase human endometrium. Understanding the factors critical for the implantation process is needed for improving fertility and pregnancy outcomes.

BACKGROUND: Preimplantation cross-talk between a functional blastocyst and the endometrium is critical for successful blastocyst implantation. This interaction is mediated in part by endometrial cytokines/growth factors secreted by glandular epithelium into the uterine cavity. Recent evidence suggests that blastocyst-derived hCG may influence the endometrial milieu in conception cycles thereby enhancing receptivity and implantation success. This study investigated the effect of hCG on the secretory profile of a select cohort of 44 cytokines/growth factors from primary human endometrial epithelial cells (hEECs). These factors included those with both known and unknown roles during receptivity and implantation. The expression of one previously unknown hCG-regulated factor, fibroblast growth factor 2 (FGF2), in human endometrium and its effects on hEEC function were further examined. METHODS: hEECs isolated from endometrial biopsies collected from fertile cycling women (n = 15) were treated +/- recombinant hCG (0.2-20 IU/ml) for 48 h and conditioned media was quantitatively analysed using Luminex (TM) multiplex technology. FGF2 was further investigated by immunohistochemistry, western blot and cell-adhesion assays. RESULTS: Of 44 cytokines/growth factors examined, 39 were produced by hEECs with a distinct profile. hCG (2 IU/ml) significantly increased the production of six factors, including those with known roles in receptivity and trophoblast function (interleukin-11), blastocyst migration and adhesion (CXCL10), blastocyst development (granulocyte macrophage colony-stimulating factor) and one unknown with respect to receptivity and implantation (FGF2). Up-regulation of known hCG-regulated proteins, vascular endothelial growth factor and leukaemia inhibitory factor, validated this study. Immunoreactive epithelial FGF2 increased across the menstrual cycle, being highest in secretory and first trimester pregnancy endometrium in vivo. FGF2 (100 ng/ml) stimulated phosphorylation of ERK1/2 in hEEC with no effect on ERK1/2 abundance and stimulated hEEC adhesion to fibronectin and collagen IV (components of blastocyst/trophectoderm extracellular matrix). CONCLUSIONS: These findings clearly support roles for hCG and FGF2 in the blastocyst-endometrial cross-talk important for endometrial receptivity and blastocyst implantation.

BACKGROUND Embryo implantation requires a healthy embryo and a receptive uterus. Uterine incompetence contributes significantly to implantation failure and infertility. To date, there are no reliable biochemical methods that can determine whether the uterus is receptive. Proprotein convertase 5/6 (PC6) is tightly regulated in the uterus and critical for receptivity and implantation; its secretory nature predicts PC6 to be secreted into the uterine cavity. The present study examines whether PC6 is detectable in uterine lavage and whether there is any correlation between secreted PC6 levels and uterine receptivity. METHODS Western blotting determined the presence of PC6 protein in uterine lavage. A sensitive and high-throughput activity assay was established and validated. This assay was applied to 103 lavages collected from different phases of the menstrual cycle from women with proven fertility or unexplained infertility. RESULTS Uterine lavage contained PC6 protein with levels paralleling enzymatic activity. PC6 levels were significantly higher in the receptive than in the non-receptive phase in fertile women, and the putative receptive phase levels in a subgroup of women with unexplained infertility were significantly lower than in the fertile counterparts. CONCLUSIONS PC6 levels in uterine lavage are significantly elevated in the luteal phase of fertile women and markedly reduced in a subgroup of women with unexplained infertility. Uterine fluid is a valuable source of material to evaluate uterine function. Detection of PC6 in uterine fluid may lead to the development of a rapid and relatively non-surgical assessment of uterine receptivity.

BACKGROUND During implantation, the embryo adheres to the endometrium via cell adhesion molecules (CAMs) present on blastocyst trophectoderm and endometrial epithelial cells. CAMs, including integrins and extracellular matrix (ECM) ligands, are most likely regulated by hormones, cytokines and growth factors. We hypothesized first that activin A affects the adhesive properties of trophoblast cells and second that alterations in dimeric activin A levels in the uterine cavity could disrupt adhesion, thereby causing implantation failure. METHODS This study examined effects of activin A on trophoblast cell adhesion and measured activin A levels in secretory phase uterine washings from women with and without endometriosis (EOS). Activin receptor expression on trophoblast (HTR8) cells was examined by RT-PCR, and adhesive molecules measured by integrin antibody and cell-matrix adhesion assays. Dimeric activin A was measured (enzyme-linked immunosorbent assay) in uterine washings (14 controls and 23 EOS), and betaA-subunit localization was verified in endometrial tissues. RESULTS Activin receptors are expressed by HTR8 cells. Activin A activated Smad2 in a concentration-dependent manner which was blocked by an activin receptor inhibitor (SB431542). Following activin A treatment (50 ng/ml for 24 h), trophoblast cell surface integrins alpha1 alpha2 alpha3 alpha5, beta1, beta2, beta4 and alphavbeta5 were decreased, as was cell binding to the ECM ligands, fibronectin, collagen IV and collagen I (P < 0.05). Activin A was detected in 56.5% of EOS and 21.4% of control washings, with measured levels from 42 to 8481 pg/ml (not significantly different). CONCLUSIONS Decreased trophoblast CAM production and adhesion could be caused by dysregulated local activin A levels and may contribute to implantation failure. This could explain, in part, the infertility observed in women with EOS.

background: Pilot data have indicated that both doxycycline alone and mifepristone combined with ethinyl estradiol (EE) are effective in stopping episodes of bleeding in Implanon users with troublesome bleeding. We compared four treatments against a placebo in Implanon users and tested whether repeated treatment improved subsequent bleeding patterns. method: Implanon users aged 18–45 years were randomized to treatment with (i) mifepristone 25 mg given twice on day 1 followed by 4 days of EE 20 mg; (ii) doxycycline 100 mg twice daily for 5 days; (iii) mifepristone 25 mg given twice on day 1 plus doxycycline 100 mg twice daily for 5 days; (iv) doxycycline 100 mg twice daily with EE 20 mg daily; and (v) placebo twice daily for 5 days. The primary end-point was the number of days of bleeding/spotting immediately following initiation of the first 5-day course of each therapy, compared with placebo. results: There were 204 women assigned to treatment. Mifepristone in combination with either EE or doxycycline was significantly more effective in stopping an episode of bleeding (mean 4.0 days (CI 3.5–4.6) and 4.4 days (CI 3.8–5.2), respectively) than doxycycline alone or in combination with EE, or placebo (6.4 days (CI 4.4– 9.2), 6.4 days (CI 4.8 –8.6) and 6.4 days (CL 5.1– 8.0), respectively). conclusion: Mifepristone combined with either EE or doxycycline was significantly more effective than placebo in terminating an episode of bleeding in Implanon users. However there was no improvement in subsequent bleeding patterns. Trial registration number: ACTR # 012605000206628.

BACKGROUND Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that is essential for blastocyst implantation in mice. It has been suggested that LIF may play a role in human first trimester extravillous trophoblast (EVT) invasion. The aim of the present study was to establish whether LIF induces changes in EVT function related to invasiveness. METHODS Primary first trimester human EVT cell cultures were treated with/without LIF and the effects on cell adhesion to fibronectin (FN), vitronectin (VN) and laminin (LN) were assessed. Transcript levels of integrin subunits that mediate cell adhesion to these extracellular matrix (ECM) elements were determined by real-time RT–PCR. Matrix metalloproteinase (MMP)2 and MMP9 secretion was assessed by gelatine zymography and tissue inhibitors matrix metalloproteinase (TIMP) -1 and TIMP-2 secretion by enzyme-linked immunosorbent assay. RESULTS EVT cells showed increased adhesion to FN, VN and LN ECM elements in response to LIF (20, 20 and 29%, respectively, P < 0.05 FN and VN compared to control; and P < 0.001 LN compared to control). Integrin β4 mRNA levels decreased by 50% following LIF treatment (P < 0.001 versus control). MMP2 and MMP9 secretion was not affected by LIF but LIF did increase secretion of TIMP-1 and -2 (P < 0.001 versus control). LIF stimulated the phosphorylation of signal transducer and activator of transcription (STAT) 3 protein while it did not affect STAT3 protein abundance. The addition of a LIF inhibitor attenuated the LIF-induced STAT3 phosphorylation in EVT. CONCLUSION The results suggest that LIF can regulate EVT invasion, suggesting an important role in early placental development.

BACKGROUND: Abnormal bleeding is common in hormone therapy (HT) users. We aimed to determine how HT alters endometrial blood vessels and stromal factors known to regulate vascular growth and integrity. METHODS: Prospective observational study of 165 post-menopausal women in Western Australia. The following were measured in endometrial biopsies: vascular density (vessels/mm 2 ), total vessel area (total area enclosed by peripheral vascular immunostaining for perivascular pericytes in mm 2 ), total luminal area (mm 2 ) and vessel wall area (total vessel area minus luminal area), stromal expression of matrix metalloproteinases (MMP) -1, -3, -9 and -14, their tissue inhibitors (TIMPs) -1-4 and vascular endothelial growth factor (VEGF) by immunohistochemistry. RESULTS: Total vessel area was greater during bleeding compared with HT users with no bleeding (P 5 0.028) or with a prior irregular bleeding (P 5 0.039). Total vessel area was greater in non-HT users compared with HT users with no bleeding (P 5 0.021). In HT users, vessel luminal area was greater during bleeding compared with HT users with no bleeding (P 5 0.030) and vessel wall area was also increased (P 5 0.025). During bleeding there was an increase in stromal TIMP-2 staining (P 5 0.044). No significant changes in endometrial MMP or VEGF were seen. CONCLUSIONS: Abnormal bleeding in HT users is associated with changes in endometrial vessel size and in stromal expression of factors known to regulate vascular growth and integrity. These changes may contribute to abnormal bleeding.

OBJECTIVE: The objective was to assess endometrial chemokines in users of the levonorgestrel-releasing intrauterine system (LNG-IUS) and correlate them with leucocyte populations, uterine natural killer cells (uNK) and mast cells (MCs). MATERIALS AND METHODS: Endometrium was obtained from two groups of women who had been using LNG-IUS for 3 years or more: 11 amenorrhoeic women formed the non-bleeding group and 15 women who maintained some form of cyclic bleeding comprised the bleeding group. Specific antibodies were used for the assessment of neutrophils, uNK cells and MCs. Immunohistochemistry was performed to locate the chemokines 6Ckine and interleukin-8 (IL-8). RESULTS: Neutrophils were few and without differences between the two groups. uNK cells were significantly higher in the bleeding group (P < 0.0001). There was no difference between the total number of MCs and activated MCs, but there was a greater extracellular area stained for MC tryptase (P < 0.05). Chemokines 6CKine and IL-8 were abundant in the stroma and in the epithelium, and there was no difference between the groups. CONCLUSIONS: We observed more uNK cells in users with bleeding and a greater extracellular area stained for MC tryptase, although there were no differences between the number of MCs and activated MCs or the chemokines 6CKine and IL-8. uNK cells and MC products may play a role in provoking breakthrough bleeding in long-term users of the LNG-IUS.

The major side-effect of progestogen-only contraception is disruption of menstrual bleeding patterns which can lead to a high incidence of early discontinuation. The aim of this study was to compare three treatments with placebo on the duration and recurrence of frequent and/or prolonged bleeding in Implanon users. Women between the ages of 18 and 45 years who had used Implanon for = 3 months and were experiencing prolonged or frequent bleeding patterns were recruited at four Australian sites. Subjects were randomized to treatment using computer-generated random number table if they met the World Health Organization criteria for prolonged and/or frequent bleeding in the previous 90 days [Belsey E.M. Pinol A.P.Y. and Taskforce on Long- Acting Systemic Agents for Fertility Regulation World Health Organization (1997) Contraception 5557-65]. Treatments were: (1) mifepristone 25 mg given twice on day 1 followed by 4 days of twice daily placebo; (2) mifepristone 25 mg given twice on day 1 followed by 4 days of ethinyl estradiol (EE) 20 µg in the morning and placebo at night; (3) doxycycline 100 mg twice daily for 5 days; and (4) placebo twice daily for 5 days. Analysis was by intention to treat. The primary endpoint was the number of days of bleeding and spotting immediately following initiation of the 5 day course of each active therapy compared with placebo. A total of 179 women was assigned to treatment. Both mifepristone in combination with EE and doxycycline alone were significantly more effective in stopping an episode of bleeding {mean 4. 3 days [confidence interval (CI) 3.5-5.2] and 4.8 days (CI 3.9-5.8) respectively} than mifepristone alone or placebo [5.9 days (CI 4.8-7.2) and 7.5 days (CI 6.1-9.1) respectively]. No effect on subsequent bleeding patterns was observed in any treatment group. Both mifepristone plus EE and doxycycline alone were significantly more effective than placebo in terminating an episode of bleeding in women with prolonged and/or frequent bleeding using Implanon. We believe that the observed reduction in the number of bleeding days by almost 50% compared to placebo in both the mifepristone combination group and the doxycycline group demonstrates a clinically significant improvement in bleeding patterns and that further trials are needed to compare different combinations of therapy as well as multiple dosing regimens in order to establish which is the most effective treatment option. The effect of repeat administration or combinations of these preparations on long-term bleeding patterns requires further investigation. (authors)

Background Breakthrough bleeding (BTB) is the most common reason for discontinuation of progestin-only (p-only) contraceptives, yet the causes are unknown. Use of p-only contraceptives is associated with elevated influx of endometrial leukocytes, similar to that observed perimenstrually or within decidualized endometrium. We hypothesized that chemokine expression is altered in women using p-only contraceptives, leading to abnormal leukocyte recruitment and BTB. Methods Expression of eight highly abundant endometrial chemokines was examined using immunohistochemistry and real-time PCR, in endometria from women using subdermal and intrauterine levonorgestrel and correlated to leukocyte subpopulations. Results Macrophage-derived chemokine (MDC), hemofiltrate CC chemokine-1 (HCC-1), monocyte chemoattractant protein-3 (MCP-3), interleukin-8 (IL-8) and eotaxin were strongly produced by epithelial glands, comparable to levels in premenstrual phase endometrium. Stromal cells were negative for chemokines in atrophic/shedding endometria, but intensely positive in highly decidualized tissues for MDC, MCP-3, HCC-1 and 6Ckine. Macrophage inflammatory protein-1beta (MIP-1b) and HCC-4 were suppressed in all p-exposed endometria. Conclusions These data demonstrate that chemokine expression is dysregulated in p-exposed endometria, consistent with the morphological appearance of the endometrium and the leukocyte subsets present. This reinforces a potential role for chemokines in the elevated leukocyte recruitment that contributes to endometrial fragility and BTB.

BACKGROUND: Abnormal uterine bleeding is commonly associated with progestin-only contraceptives, including depot medroxyprogesterone acetate (DMPA), and remains the main reason why these agents are discontinued. Matrix metalloproteinases (MMP), enzymes which degrade specific extracellular matrix components, and leukocytes are implicated in menstruation. Alteration in endometrial MMP-9 and leukocytes has been described in users of other progestin-only contraceptives, suggesting a potential role in the pathogenesis of abnormal uterine bleeding. METHODS: This study describes the immunohistochemical localization of MMP-9, the tissue inhibitors of metalloproteinases (TIMP)-1, TIMP-2 and TIMP-3, and leukocytes [CD3 T lymphocytes, CD68 macrophages and CD56 uterine natural killer cells (uNK cells)] in the endometrium of women using DMPA. Comparison is made with perimenstrual endometria from normal cycling women. RESULTS: Similar to the perimenstrual period, an influx of MMP-9 positive cells (identified as neutrophils and CD3 T cells on the basis of dual immunofluorescence), macrophages and uNK cells was observed in the endometrium of DMPA users. However, significantly more endometrial T lymphocytes were observed in DMPA users. Immunoreactive TIMP, present in all endometrial compartments, demonstrated a significantly decreased immunostaining intensity score in endometrial epithelium (TIMP-1 and TIMP-2), stroma (TIMP-1, TIMP-2 and TIMP-3), endothelium (TIMP-1 and TIMP-2) and vascular smooth muscle (TIMP-1) of DMPA users compared with controls. No correlation was observed between the parameters studied and bleeding patterns reported by subjects. CONCLUSIONS: These findings provide additional evidence for the importance of the MMP/TIMP balance in the loss/maintenance of endometrial integrity and in the complex pathological mechanisms involved in the troubling side-effect of menstrual bleeding disturbance.

Considerable evidence supports a role for matrix metalloproteinases (MMP) in menstruation, but their focal pattern of expression within perimenstrual and menstrual endometrium suggests local rather than hormonal regulation. Menstruation shares a number of features with inflammatory responses, with leukocyte infiltration, proliferation and activation, occurring in the endometrium prior to menstruation. We propose that the leukocytes release MMP at this time and also that interactions between leukocytes and the stromal and epithelial cells of the endometrium induce and activate MMP. Co-culture studies using mast cells or neutrophils with endometrial stromal cells support this hypothesis. How leukocytes enter the endometrium is not understood but a role for chemokines has been proposed. The expression patterns of eotaxin and its receptor CCR3 in endometrium support a role in chemoattraction of eosinophils but expression of monocyte chemotactic proteins 1 and 2 does not correlate with macrophage numbers. Nothing is known of how the leukocytes become activated. Nevertheless, the overall result is a tissue in which an inflammatory-type reaction occurs with release of a myriad of potent regulators. These induce production and activation of MMP and alter the ratio between these and their tissue inhibitors, resulting in tissue breakdown.

Inhibin/activin alphaC/alphaN and betaA subunits were localized immunohistochemically in the human endometrium throughout the menstrual cycle using an affinity-purified sheep polyclonal antibody raised against the alphaC/alphaN subunit and an affinity-purified rabbit polyclonal antibody raised against the betaA subunit. The betaB subunit was below the level of detection in all human endometrial samples tested. Immunoreactive inhibin alphaC/alphaN subunit was localized in the luminal epithelium, glandular epithelium, stromal tissues and vascular endothelium with no significant variation across the normal menstrual cycle. Immunoreactive betaA subunit, common to inhibin A and activins AA and AB was localized in the luminal and glandular epithelium and in migratory cells while the endometrial stromal cells, decidua, vascular smooth muscle and endothelium were devoid of immunoreactivity. A significant variation of immunoreactive betaA subunit was observed in glandular and luminal epithelium across the normal menstrual cycle. In proliferative endometrium, only a very low level of betaA immunostaining was seen in luminal and glandular epithelium, while the luminal epithelial staining increased significantly in the early secretory phase and remained relatively constant over the rest of the menstrual cycle. A progressive increase in betaA immunoreactivity was observed also in the glandular epithelium during the secretory phase reaching a maximum in the late secretory phases, and decreasing at menstruation. Co-localization studies on serial sections suggested that the migratory cells expressing strong betaA immunoreactivity were macrophages and neutrophils but not eosinophils or mast cells. Thus, cells within the human endometrium are capable of expressing inhibin/activin molecules in vivo. The variation in the pattern of secretion of the betaA subunit across the menstrual cycle suggests that activin peptides may have a physiological role in endometrial function.

The mechanisms underlying excessive menstrual bleeding or menorrhagia are not understood. In view of its potent vasoconstrictor and growth factor properties, endothelin has been proposed to have a potential paracrine role in the regulation of uterine blood flow and therefore could be a factor in menorrhagia. We compared the cellular localization of endothelin and its metabolizing enzyme, neutral endopeptidase, in endometrial biopsies from women with documented menorrhagia and in those with a normal menstrual cycle. Menorrhagia was documented by measurement of menstrual blood loss, 146 +/- 141 ml (median +/- SD). Endothelin and neutral endopeptidase were localized by immunohistochemistry, and the staining intensity was graded. Their immunostaining patterns were found to differ in menorrhagia compared to the normal menstrual cycle. Endothelin was reduced in glandular epithelium in menorrhagia and did not vary cyclically, while neutral endopeptidase was increased in the glandular epithelium. In menorrhagia, stromal endothelin immunoreactivity was not different from the normal cycle and although neutral endopeptidase immunostaining in stroma was similar to the secretory phase of normal endometrium, cyclical variation was absent. The potential for increased metabolism of endothelin could be an explanation for the decreased endothelin immunostaining in the glandular epithelium.

Endothelin (ET) and its mRNA are present in human endometrium. Its expression varies across the menstrual cycle, reaching maximal levels in the pre-menstrual phase. Human endometrial epithelial cells are the major in-vitro source of ET, and its release is affected by the stage of the menstrual cycle from which the endometrium is taken and by the cytokines transforming growth factor-beta 1 and interleukin-1 alpha. The cyclical variation in both ET mRNA and protein expression across the normal menstrual cycle, and the differences observed in abnormal uterine bleeding (specifically reduced immuno-reactivity in luminal and glandular epithelium in the endometrium of Norplant users), are consistent with a role for ET in the control of menstrual bleeding. The role of epithelial cell ET is not yet understood. Whether this source of ET is important in endometrial regeneration and repair following menstruation or in vaso-constriction to cease menstrual bleeding remains to be determined.