A comparison of cathepsin D levels in endometriotic tissue and in uterine endometrium**Supported by the Swedish Medical Research Council, Stockholm (Project No B91-17X-09511-01A) and Medical Faculty, University of Lund, Lund, Sweden.††Presented in part at the 3rd World Congress of Gynecological Endocrinology, Madonna di Campiglio, Italy, February 9 to 16, 1992

Cathepsin Protease Inhibition Reduces Endometriosis Lesion Establishment

Endometriosis is a gynecologic disease characterized by the ectopic presence of endometrial tissue on organs within the peritoneal cavity, causing debilitating abdominal pain and infertility. Current treatments alleviate moderate pain symptoms associated with the disorder but exhibit limited ability to prevent new or recurring lesion establishment and growth. Retrograde menstruation has been implicated for introducing endometrial tissue into the peritoneal cavity, but molecular mechanisms underlying attachment and invasion are not fully understood. We hypothesize that cysteine cathepsins, a group of powerful extracellular matrix proteases, facilitate endometrial tissue invasion and endometriosis lesion establishment in the peritoneal wall and inhibiting this activity would decrease endometriosis lesion implantation. To test this, we used an immunocompetent endometriosis mouse model and found that endometriotic lesions exhibited a greater than 5-fold increase in active cathepsins compared to tissue from peritoneal wall or eutopic endometrium, with cathepsins L and K specifically implicated. Human endometriosis lesions also exhibited greater cathepsin activity than adjacent peritoneum tissue, supporting the mouse results. Finally, we tested the hypothesis that inhibiting cathepsin activity could block endometriosis lesion attachment and implantation in vivo. Intraperitoneal injection of the broad cysteine cathepsin inhibitor, E-64, significantly reduced the number of attached endometriosis lesions in our murine model compared to vehicle-treated controls demonstrating that cathepsin proteases contribute to endometriosis lesion establishment, and their inhibition may provide a novel, nonhormonal therapy for endometriosis.

Methylation of promoter regions of genes of the human intrauterine Renin Angiotensin system and their expression

The intrauterine renin angiotensin system (RAS) is implicated in placentation and labour onset. Here we investigate whether promoter methylation of RAS genes changes with gestation or labour and if it affects gene expression. Early gestation amnion and placenta were studied, as were term amnion, decidua, and placenta collected before labour (at elective caesarean section) or after spontaneous labour and delivery. The expression and degree of methylation of the prorenin receptor (ATP6AP2), angiotensin converting enzyme (ACE), angiotensin II type 1 receptor (AGTR1), and two proteases that can activate prorenin (kallikrein, KLK1, and cathepsin D, CTSD) were measured by qPCR and a DNA methylation array. There was no effect of gestation or labour on the methylation of RAS genes and CTSD. Amnion and decidua displayed strong correlations between the percent hypermethylation of RAS genes and CTSD, suggestive of global methylation. There were no correlations between the degree of methylation and mRNA abundance of any genes studied. KLK1 was the most methylated gene and the proportion of hypermethylated KLK1 alleles was lower in placenta than decidua. The presence of intermediate methylated alleles of KLK1 in early gestation placenta and in amnion after labour suggests that KLK1 methylation is uniquely dynamic in these tissues.

Cathepsin B in eutopic and ectopic endometrial tissues of patients with endometriosis

This study was performed to investigate the expression of cathepsin B mRNA and protein in eutopic and ectopic endometrial tissues of patients with endometriosis and in normal endometrial tissues and to clarify the association between the cathepsin B expression and endometriosis. A total of 40 women with histologically confirmed endometriosis were recruited for study group. For controls, 20 women undergoing operative treatment for uterine myoma, cervical intraepithelial neoplasia (CIN) or benign gynecologic conditions other than endometriosis were recruited. Eutopic endometrial tissues of both groups and ectopic endometrial tissue of study group were collected during the operations. We employed real time reverse transcriptase - polymerase chain reaction (RT-PCR) to quantify mRNA levels of cathepsin B in these tissues. Then, we performed western blot analysis to measure the protein levels of cathepsin B. The expressions of cathepsin B mRNA and protein were significantly higher in both eutopic and ectopic endometrial tissues of women with endometriosis than in endometrial tissues of controls. These data suggest that the higher expression of cathepsin B in the endometrial tissues might be associated with the development of endometriosis. In addition, eutopic endometrium itself with higher expression cathepsin B may play a pivotal role in the histogenesis of endometriosis.

Determination of cathepsins B, D and G concentration in eutopic proliferative endometrium of women with endometriosis by the surface plasmon resonance imaging (SPRI) technique

OBJECTIVE

To determine the concentrations of cathepsins B, D and G in proliferative eutopic endometrium of patients with and without endometriosis, by use of the surface plasmon resonance imaging (SPRI) technique.

STUDY DESIGN

A total of 55 patients were recruited in the study: 31 patients with endometriosis (stages I-IV) and 24 controls. Endometrial samples were obtained in the first phase of the menstrual cycle from regularly menstruating premenopausal women, prior to laparoscopy, by the use of aspiration biopsy. Endometriosis was appropriately classified according to the Revised American Fertility Society classification and confirmed by histopathology in every case. The SPRI technique was used to determine the concentration of cathepsins B, D and G. To compare the two groups for quantitative data, Mann-Whitney-Wilcoxon's test was used due to the non-normal distribution of the tested variables and normality of distribution was assessed using Shapiro-Wilk W test.

RESULTS

The concentration of the three examined cathepsins was higher in the proliferative eutopic endometrium of patients with endometriosis, especially in advanced stages, e.g. III and IV, when compared to healthy individuals. Corresponding median values were, for cathepsin B: [7.93 pmol/mg (min-max 2.82-15.71) vs 1.2 pmol/mg (min-max 0.7-15.49) p=0.0014], for cathepsin D: [1.86 pmol/mg (min-max 0.51-5.4) vs 1.03 pmol/mg (min-max 0.4-2.72) p=0.00041] and for cathepsin G: [0.6 pmol/mg (min-max 0.33-2.51) vs 0.3 pmol/mg (min-max 0.16-1.29) p=0.00051].

CONCLUSIONS

Increased concentrations of cathepsins B, D and G in the proliferative eutopic endometrium may play a role in the implantation of endometrial tissue outside the uterine cavity.

Immunohistochemical expression of matrix metalloproteinases, their tissue inhibitors, and cathepsin-D in ovarian endometriosis: correlation with severity of disease

In this study the immunohistochemical expression of matrix metalloproteinases 1, 2, 3, and 9, tissue inhibitors (TIMPs) 1 and 2, and cathepsin-D in ovarian endometriomas were correlated with the clinical severity of endometriosis (i.e., presence of chronic pelvic pain [CPP] and American Society of Reproductive Medicine [ASRM] scores). Positive expression of proteases and their inhibitors was found more frequently in cases with low ASRM scores, whereas presence of CPP correlated significantly with absence of expression of TIMPs 1 and 2, indicating, first, that production of these enzymes is more active during the initial phases of the evolution of ovarian endometriosis, declining as fibrosis develops, and second, that expression of TIMPs seems to play a role in the development of CPP.

Stable inhibition of interleukin 1 receptor type II in Ishikawa cells augments secretion of matrix metalloproteinases: possible role in endometriosis pathophysiology

Our previous studies showed a marked deficiency in interleukin 1 receptor type II (IL1R2) in the endometrial tissue of women with endometriosis, particularly in epithelial cells. We believe that such a deficiency in IL1R2, a potent and specific IL1 inhibitor, makes endometrial cells more sensitive to IL1 and less capable of buffering the cytokine's effects, which may lead to functional changes that favor endometriosis development. The main objective of our study was to stably inhibit IL1R2 expression in endometrial cells in order to evaluate the role of IL1R2 deficiency in endometriosis pathophysiology. Stable clones of Ishikawa adenocarcinoma endometrial cells transfected with IL1R2 antisense and showing downregulation of IL1R2 protein expression, or with the empty expression vector alone and showing no noticeable difference in IL1R2 expression, were selected. The downregulation of IL1R2 expression in IL1R2 antisense transfectants when compared with control cells was confirmed by ELISA, Western blot and immunofluorescence. In these cells, IL1R2 expression was markedly reduced, compared with non-transfected cells or cells transfected with the empty vector, and there was a significant increase in the basal and the IL1-beta (IL1B)-induced levels of matrix metalloproteinase (MMP)-2 and MMP-9 secretion. Furthermore, a significant decrease in IL1B-induced secretion of tissue inhibitor of MMPs-1, a known MMP-9 inhibitor, was observed. These in vitro data make plausible a role for IL1R2 deficiency in the capability of endometrial cells to invade the host tissue and develop in ectopic locations.

The role of endometrium in endometriosis

Endometriosis is defined as the presence of endometrial glands and stroma outside the uterus. Several theories have been proposed to explain the pathogenesis of this disease. According to Sampson's retrograde menstruation theory, endometrial cells are refluxed through the fallopian tubes during the menstruation and implant onto peritoneum or pelvic organs. Since retrograde menstruation is a very common phenomenon among women of reproductive age, there must be other factors that may contribute to the pathophysiology and/or pathogenesis of endometriosis. Genetic predisposition, environmental factors, and alterations in immune and endocrine functions are believed to play significant roles in the establishment and maintenance of endometriosis. Although the eutopic endometriums of women with and without endometriosis are histologically similar, studies revealed that there are many fundamental differences between these two tissues. Invasive properties, decreased apoptosis, alterations in expression of specific gene and proteins, and increased steroid and cytokine production have been identified in eutopic endometrium of women with endometriosis. Furthermore, significant biochemical differences exist even between ectopic and autologous eutopic endometrium. These differences can be explained by the direct effects of an inflammatory peritoneal environment.

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.

Cathepsin D expression in normal, hyperplastic and malignant endometrial tissue: an immunohistochemical analysis

Cathepsin D (CathD), a lysosomal aspartyl protease secreted by normal and malignant cells, is considered to be involved in breakdown of the extracellular matrix. Aim of the present study was to determine the frequency and tissue distribution of CathD in normal, hyperplastic and malignant endometrium. Paraffin-fixed endometrial tissue was obtained from premenopausal women in the proliferative phase (n = 5), early secretory phase (n = 4) and late secretory phase (n = 4) as well as glandular-cystic hyperplasia (n = 5), endometrial polyps (n = 5), endometrial polyps from the use of tamoxifen (n = 5), adenomatous hyperplasia (AH) grade I (n = 5), grade II (n = 4), grade III (n = 5) and endometroid adenocarcinoma (n = 5). CathD expression was evaluated with the IRS score and ANOVA analysis was used for statistical evaluation. CathD was primarily localised in luminal and glandular epihelium with little staining in stromal cells. The expression of CathD was significantly higher during the late secretory phase than in the proliferative phase. Highest expression of CathD was observed in the late secretory phase and in glandular-cystic hyperplasia, whereas endometroid carcinoma showed no expression. A continuous increase in CathD expression was observed in AH, with a significant difference between AH grade I and III. In conclusion, CathD was found to be expressed in normal and hyperplastic endometrial tissue. CathD immunostaining in normal endometrial glands varied on the basis of the phase of the menstrual cycle, suggesting physiological functions of CathD in endometrial maturation and degradation. Adenocarcinomas did express significant lower amounts of CathD. Therefore, the prognostic value of this parameter remains uncertain. A continuous increase in CathD immunostaining was observed in AH. Since AH grade III can be considered as a precursor of endometrial cancer, CathD could be a possible parameter for assessing malignant transformation.

Was Sampson wrong?

OBJECTIVE

Sampson's theory of reflux menstruation suggests that endometriosis is one form of a condition known as an autotransplant. This study seeks to characterize autotransplants as they are described in the literature and to determine whether endometriosis resembles an autotransplant.

DESIGN

Literature review of published studies containing the following types of information: [1] characterization of the histologic features, immunohistochemistry, or structural function of autotransplants; and [2] comparisons of endometriosis with endometrium.

MAIN OUTCOME MEASURE(S)

Characteristics of multiple types of autotransplants were noted. Similarity or dissimilarity of endometriosis and endometrium was tabulated to judge qualitatively whether the bulk of the evidence supports the notion that endometriosis is an autotransplant.

RESULT(S)

Autotransplants remain very similar or identical to eutopic tissues of origin, regardless of the length of time following autotransplantation. Endometriosis differs in many profound and fundamental ways from eutopic endometrium, including clonality of origin, enzymatic activity, protein expression, and histologic and morphologic characteristics. A minority of studies has found similarities between endometriosis and eutopic endometrium.

CONCLUSION(S)

Endometriosis is dissimilar to eutopic endometrium and therefore lacks characteristics of an autotransplant. Sampson's theory of origin of endometriosis is not supported by the results of this study. Studies of experimental endometriosis that have not used menstrual endometrium may be misleading.

May cathepsin D immunoreactivity be used as a prognostic factor in endometrial carcinomas? A comparative immunohistochemical study

OBJECTIVE

To investigate the prognostic value of immunohistochemical detection of cathepsin D and the association between cathepsin D and established prognostic factors in endometrial carcinoma.

METHODS

Cathepsin D immunoreactivity was determined by an immunohistochemical technique in a series of 79 patients with surgical stage I-III primary endometrial carcinoma.

RESULTS

Of 79 tissue specimens, 48 (61%) showed a positive reaction for cathepsin D. A significant correlation between cathepsin D and histological grade was found (P < 0.05). The other established clinicopathological prognostic factors were not associated with cathepsin D. There was not any significant difference in prognosis between the positive cases and negative cases for cathepsin D (P > 0.05). In the univariate analysis cathepsin D immunoreactivity did not show significant prognostic value for overall survival (P > 0.05). The multivariate analysis also showed that cathepsin D was not related to patient outcome (P = 0.24, relative risk = 0.34, 95% confidence interval = 0.05-2.09).

CONCLUSIONS

Our results suggest that cathepsin D immunoreactivity may not be of prognostic value but more studies are needed to evaluate the relationship between its immunoreactivity in tumor cells and in other cells.

Endometrial anomalies in women with endometriosis

Endometriotic lesions are defined by extrauterine growth of endometrial glands and stroma. Retrograde menstruation with subsequent attachment, invasion, and neovascularization are believed to give rise to the endometriotic lesions. As most women exhibit some degree of retrograde menstruation, some other unidentified factor(s) must render certain women susceptible to attachment and growth of ectopic endometrial tissue. A variety of theories have been proposed to account for this susceptibility, including genetic predisposition, aberrant immunological response, and an altered peritoneal environment. Ectopic endometriotic lesions are histologically similar to their putative eutopic precursors, yet significant biochemical differences exist between these two tissues. Less information is available regarding differences between eutopic endometrium from women with or without endometriosis. This report describes anomalies in structure, proliferation, immune components, adhesion molecules, proteolytic enzymes and inhibitors, steroid and cytokine production and responsiveness, and gene expression and protein production that have been identified in eutopic endometrium from women with endometriosis.

Increased concentrations of cathepsin D in peritoneal fluid from women with endometriosis

To assess the release of the proteolytic enzyme cathepsin D in endometriosis, concentrations in peritoneal fluid and serum were measured by ELISA in 54 women with (n = 33) and without (n = 21) endometriosis. Surgery was scheduled in either the proliferative or secretory phase of the menstrual cycle. The concentrations of cathepsin D in the peritoneal fluid were markedly elevated in the endometriosis patients (median 58 ng/ml, interquartile range 0-166 ng/ml) as compared to the controls (5 ng/ml, 0-86 ng/ml), especially in women with late stage disease (n = 19, stages III/IV) and in those not undergoing gonadotrophin-releasing hormone (GnRH) agonist therapy (n = 15). No significant difference was determined in cathepsin D concentrations of the serum from women with and without endometriosis. We conclude that cathepsin D is an important factor that may contribute to the pathogenesis of endometriosis, possibly by promoting digestion of extracellular matrix proteins. These results have implications for the therapeutic efficacy of GnRH agonists.

Immunohistochemical localization of insulin-like growth factor-binding protein-3 in eutopic and ectopic endometrial tissues

OBJECTIVE

To evaluate the expression of insulin-like growth factor-binding protein-3 (IGFBP-3) in the eutopic endometrium and in endometriotic lesions.

DESIGN

Retrospective immunohistochemical study.

PATIENT(S)

Twenty-five normal women and 39 women with endometriosis.

INTERVENTION(S)

Endometrial and endometriotic tissue biopsies obtained at laparoscopy.

MAIN OUTCOME MEASURE(S)

Expression of IGFBP-3 assessed by immunohistochemistry.

RESULT(S)

In the endometrium, positive immunostaining of IGFBP-3 was observed both in the stroma and the epithelial glands. The intensity of staining in the glands during the secretory phase was significantly higher in women with endometriosis compared with controls (P = .018). An increased expression of IGFBP-3 over controls was found in stages I and II of the disease (P = .018), whereas in stages III and IV, the difference between controls and women with endometriosis was not significant (P = .300). In endometriotic tissues, a much-marked immunostaining of IGFBP-3 was noted in 90% of the glands and 67% of the stroma without apparent differences related to cycle phase.

CONCLUSION(S)

These data show intense staining of IGFBP-3 in endometriosis lesions and increased expression of the protein in the endometrium of patients with endometriosis compared to controls. This marked expression of IGFBP-3 could be related to its previous finding in the peritoneal fluid and to its potential involvement in the pathophysiology of endometriosis.

2,3,7,8-Tetrachlorodibenzo-p-dioxin increases mRNA levels for interleukin-1beta, urokinase plasminogen activator, and tumor necrosis factor-alpha in human uterine endometrial adenocarcinoma RL95-2 cells

This study investigated the potential role of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in uterine growth utilizing a human endometrial adenocarcinoma cell line (RL95-2). Western immunoblot analysis showed a maximal induction of cytochrome P4501A1 (CYP1A1) at 1 nM TCDD, but no change in epidermal growth factor receptor (EGFR) protein level. Northern blot analysis showed that TCDD significantly increased the steady state mRNA level of CYP1A1 and CYP1B1 which was maximal at 1 nM. TCDD significantly increased mRNA levels for interleukin-1beta (IL-1beta) by 6h, and for urokinase plasminogen activator (uPA) and tumor necrosis factor-alpha (TNF-alpha) by 36h. Nuclear runoff analysis showed that transcription of CYP1A1 was significantly increased by TCDD with no effect on CYP1B1, uPA or IL-1beta. These results indicate that TCDD can differentially alter the expression of growth factor and cytokine gene products in uterine cells which may contribute to the promotion of uterine disease.

Basic research in endometriosis

A more thorough understanding of the mechanisms associated with the cause and pathophysiology of endometriosis may help in the development of new diagnostic and therapeutic methods for the management of endometriosis. Research has begun to enhance our understanding of endometriosis by demonstrating the differences and similarites between eutopic and ectopic endometrium, and by characterizing the peritoneal environment. Animal models have been developed and validated to conduct studies that are ethically impossible in women. Recently, cell culture models, using purified populations of cells from endometriotic lesions, have provided an appropriate in vitro endometriosis model to study the language by which cells communicate; to evaluate the biochemical effects of steroids, growth factors, pharmacological agents and immunomodulatory agents on the cells; and to study the effects of endometriosis on reproduction.