Pathogenesis

Endometriosis: Epidemiology, Classification, Pathogenesis, Treatment and Genetics (Review of Literature)

Endometriosis is a “mysterious” disease and its exact cause has not yet been established. Among the etiological factors, congenital, environmental, epigenetic, autoimmune and allergic factors are listed. It is believed that the primary mechanism of the formation of endometriosis foci is retrograde menstruation, i.e., the passage of menstrual blood through the fallopian tubes into the peritoneal cavity and implantation of exfoliated endometrial cells. However, since this mechanism is also observed in healthy women, other factors must also be involved in the formation of endometriosis foci. Endometriosis is in many women the cause of infertility, chronic pain and the deterioration of the quality of life. It also represents a significant financial burden on health systems. The article presents a review of the literature on endometriosis—a disease affecting women throughout the world.

CD44 variant 6 is involved in the attachment and invasion of endometrial cells to peritoneum

OBJECTIVE

To study the effects of CD44 standard (CD44s), CD44v3, and CD44v6 overexpression (OE) on immortalized human endometrial epithelial (iEECs) and stroma cells (human endometrial stromal cells [hESCs]) using in vitro assays and a nude mouse xenograft model. Menstrual endometrial cells from women with endometriosis have increased adhesion and also express higher levels of CD44 variant 6 (v6), but not v3, compared to menstrual endometrial cells from women without endometriosis.

DESIGN

In vitro studies and in vivo xenograft model.

SETTING

Academic center.

PATIENTS(S)

Deidentified immortalized endometrial epithelial tissue samples of a reproductive-age woman.

INTERVENTION(S)

Overexpression of CD44s, CD44v3, and CD44v6 was carried out using lipofectamine, and their expression was verified with mRNA and protein in iEEC and hESCs. The OE cells were used in in vitro studies and an in vivo xenograft model compared to plasmid control.

MAIN OUTCOME MEASURE(S)

The effect of CD44s, CD44v3, and CD44v6 OE on attachment and invasion assays and a xenograft model with immortalized human stromal and epithelial cells.

RESULT(S)

Expression of mRNA and protein confirmed appropriate OE of CD44s, CD44v3, and CD44v6 in the different cell types. CD44v6 OE increased attachment of hESCs compared with controls. CD44v6 OE did not change the attachment of iEECs. There was no difference in attachment in iEECs or hESCs with OE of CD44s or CD44v3.

CONCLUSION(S)

Overexpression of CD44v6 increases attachment of hESCs to peritoneal mesothelial cells in an in vitro assay and an in vivo xenograft model. Menstrual endometrial cell type and CD44 variants play a complex role in the development of the early endometriotic lesion.

Adolescent Physical Activity and Endometriosis Risk

Background

In the one study examining the relationship, adolescent physical activity was not associated with risk for endometriosis. Case-control studies have shown 40–80% reductions in risk for adult activity, while only an 11% reduction in endometriosis risk was observed in a recent prospective analysis.

Methods

Using data collected from the Nurses’ Health Study II, a prospective cohort study of premenopausal US nurses that began in 1989, we have attempted to clarify this relation. Data are updated every 2 yrs with follow-up for these analyses through to 2001. Women reported the average amount of time per week spent in moderate and strenuous recreational activity during three age periods: ages 12–13, ages 14–17, and ages 18–22. A metabolic equivalent (MET) score was assigned to each activity and these were summed to estimate total activity.

Results

During 637,747 person-years of follow-up, 1,481 cases of laparoscopically confirmed endometriosis were reported among women with no past infertility. After adjusting for age, calendar time, birth weight, age at menarche, parity, oral contraceptive use, and body mass index (BMI), we observed a 16% increase in the risk for endometriosis comparing the greatest amount of activity (≥80 MET-h/wk) with the least (<20 MET-h/wk) during ages 12–13 (RR=1.16, 95% CI=0.98–1.37, p-value test for trend=0.02), and no associations for ages 14–17 or ages 18–22. In analyses of the individual activity types within each time period, only strenuous activity during ages 12–13 was associated with endometriosis.

Conclusions

We did not find evidence of a beneficial association between adolescent physical activity and laparoscopically confirmed endometriosis, but in fact found a small increase in risk.

Impaired Development of Early Endometriotic Lesions in CD44 Knockout Mice

Previous studies have shown endometrial cell (EC) CD44 and peritoneal mesothelial cell (PMC)-associated hyaluronan (hyaluronic acid [HA]) are involved in the attachment of endometrial stroma and epithelial cells to peritoneal mesothelium. Here we assess the CD44-HA interaction in the formation of the early endometriotic lesion using CD44(-/-) (knockout) mice. Using an established murine model and crossover technique, endometrial tissue from donor mice (wild type [WT] and CD44(-/-)) was used to induce endometriosis in recipient mice (WT and CD44(-/-)). Endometriotic lesions were visualized by fluorescent microscopy and confirmed by hematoxylin and eosin staining. Early endometriotic lesions were decreased when CD44(-/-) endometrium was placed in WT recipients and when WT endometrium was placed in CD44(-/-) recipients (P = .002). Early endometriotic lesions were also significantly decreased when both peritoneal and endometrial tissues lacked CD44 expression (P < .01). These studies demonstrate that both EC and PMC CD44 play a role in the development of early endometriotic lesion.

Rotating nightshift work and the risk of endometriosis in premenopausal women

OBJECTIVE

The purpose of this prospective study was to study the association between rotating nightshift work and endometriosis risk within the Nurses' Health Study II.

STUDY DESIGN

We found 89,400 women without diagnosed endometriosis at baseline; the 2062 laparoscopically confirmed cases that were documented during 16 years of follow-up evaluation formed our study population.

RESULTS

Overall, there was no association between rotating nightshift work and risk of endometriosis. When the cases were categorized by infertility status, risk was elevated among women with concurrent infertility and ≥5 years of rotating nightshift work (rate ratio, 1.71; 95% confidence interval, 1.18-2.49; P(trend) = .005), compared with women with no rotating nightshift work. In contrast, there was no association among women without reported infertility (P(heterogeneity) = .003).

CONCLUSION

Women who work rotating nightshifts for ≥5 years may have a modestly elevated risk of endometriosis if concurrently infertile. However, the relation between shiftwork, endometriosis, and infertility is complex, and the potential for bias because of a healthy or infertile worker effect must be considered.

A prospective study of body size during childhood and early adulthood and the incidence of endometriosis

BACKGROUND

An inverse association between adult body mass index (BMI) and risk of endometriosis has frequently been reported. However, the association between body size during childhood and early adulthood and endometriosis is not as well documented.

METHODS

Using data collected from the Nurses' Health Study II, a prospective cohort study of premenopausal US nurses, that began in 1989, we have attempted to clarify this relationship. Data are updated every 2 years with follow-up for these analyses through 2001. In 1989 women recalled their body size at ages 5, 10 and 20 years using a validated 9-level figure drawing.

RESULTS

During 831 910 person-years of follow-up, 1817 cases of self-reported laparoscopically-confirmed endometriosis were observed among women with no past infertility. After adjusting for age, birthweight, age at menarche, parity, oral contraceptive use and adult BMI, we observed a significant reduction in the incidence of endometriosis with increasing body size for all time periods. The relative risks (RRs) comparing the smallest and largest figure sizes to the middle category during childhood (ages 5-10) were 1.18 (95% confidence interval 1.02-1.36) and 0.82 (0.66-1.02), P-trend = 0.0002. At age 20, the RRs for the same comparisons were 1.32 (1.06-1.65) and 0.87 (0.74-1.03), P-trend = 0.04. Additional adjustment by menstrual cycle length and regularity yielded similar associations. The associations were stronger among nulliparous women than among parous women, although not all differences were statistically significant.

CONCLUSION

In this large cohort of premenopausal women, there was evidence of a persistent inverse association between childhood and early adulthood body size and incidence of laparoscopically confirmed endometriosis, independent of adult BMI and menstrual cycle characteristics.

Adult physical activity and endometriosis risk

BACKGROUND

Regular exercise has been associated with a 40%-80% reduction in risk for endometriosis in several case-control studies. However, women experiencing symptoms prior to their diagnosis may be less likely to exercise than healthy controls, thus biasing the observed association.

METHODS

Using data collected from the Nurses' Health Study II, a prospective cohort study of premenopausal US nurses that began in 1989, we have attempted to clarify this relation. Data are updated every 2 years with follow-up for these analyses through 2001. In 1989, 1991, and 1997 women reported average amount of time per week engaging in various physical activities. A metabolic equivalent (MET) score was assigned to each activity, and these were summed to estimate total activity.

RESULTS

A total of 102,197 premenopausal women contributed 996,422 person-years of follow-up with 2703 cases of laparoscopically confirmed endometriosis. After adjusting for BMI at age 18, current BMI, smoking, parity, infertility status, oral contraceptive use, age at menarche, and menstrual cycle length and pattern in college, we observed only a slight reduction in the incidence of endometriosis, comparing the highest level of activity (>or=42 MET hours/week) to the lowest (<3 MET hours/week) (rate ratio = 0.89 [95% confidence interval = 0.77-1.03]). The association was limited to participants with no past or concurrent infertility (P = 0.002, test for heterogeneity). No associations were seen with inactivity.

CONCLUSIONS

In this first prospective assessment, we did not find evidence of the strong inverse association previously reported, although we cannot rule out a modest inverse association.

Immunopathogenesis of pelvic endometriosis: role of hepatocyte growth factor, macrophages and ovarian steroids

Endometriosis, a chronic disease characterized by endometrial tissue located outside the uterine cavity is associated with chronic pelvic pain and infertility. However, an in-depth understanding of the pathophysiology of endometriosis is still elusive. It is generally believed that besides ovarian steroid hormones, the growth of endometriosis can be regulated by innate immune system in pelvic microenvironment by their interaction with endometrial cells and immune cells. We conducted a series of studies in perspectives of pelvic inflammation that is triggered primarily by bacterial endotoxin (lipopolysaccharide) and is mediated by toll-like receptor 4 and showed their involvement in the development of pelvic endometriosis. As a cellular component of innate immune system, macrophages were found to play a central role in inducing pelvic inflammatory reaction. We further report here that peritoneal macrophages retain receptors encoding for estrogen and progesterone and ovarian steroids also participate in producing an inflammatory response in pelvic cavity and are involved in the growth of endometriosis either alone or in combination with hepatocyte growth factor (HGF). As a pleiotropic growth factor, HGF retains multifunctional role ometriosis. We describe here the individual and step-wise role of HGF, macrophages and ovarian steroid hormones and their orchestrated involvement in the immunopathogenesis of pelvic endometriosis.

Natural hair color and the incidence of endometriosis

OBJECTIVE

To investigate a previously hypothesized relation between natural hair color and endometriosis.

DESIGN

Prospective cohort study.

SETTING

Nurses' Health Study II with 10 years of follow-up.

PARTICIPANT(S)

A total of 90,065 women, 25-42 years old, who had never been diagnosed with endometriosis, infertility, or cancer at baseline in 1989.

MAIN OUTCOME MEASURE(S)

Incidence of laparoscopically confirmed endometriosis according to natural hair color.

RESULT(S)

During 379,422 person-years of follow-up, 1,130 cases of laparoscopically confirmed endometriosis were reported among women with no past infertility. After adjusting for age, calendar time, parity, race, and body mass index at age 18, we observed no association overall. However, compared with women with any other hair color, we observed an increased rate of endometriosis among women with naturally red hair who had never been infertile (incidence rate = 1.3, 95% confidence interval [CI] = 1.0-1.7), but a decreased rate among women with naturally red hair among women who were infertile (incidence rate = 0.4, 95% CI = 0.2-1.2); P value, test for heterogeneity = .03.

CONCLUSION(S)

Overall, we did not observe a significant relation between red hair color and the rate of endometriosis, however this prospective cohort study suggests that the relation may differ by infertility status.

Peritoneal fluid cytokines and sICAM-1 in minimal endometriosis: search for discriminating factors between infertility and/or endometriosis

OBJECTIVE

To evaluate cytokine levels (IL-1beta, TNF-alpha, IL-6, IL-8), soluble intercellular adhesion molecule-1 (sICAM-1) and number of macrophages in peritoneal fluid (PF) of women with no minimal endometriosis and associated (or not) infertility in order to discriminate between infertility and/or endometriosis.

STUDY DESIGN

Cytokines and sICAM-1 were measured by using quantitative enzyme-linked immunosorbent assay (ELISA) while the macrophages were identified by May-Grunwald-Giemsa and non-specific esterase staining and presented as medians. The measurements were performed in 78 women belonging to four selected subgroups according to their endometriosis and/or infertility status. Statistical analysis was performed using Kruskal-Wallis non-parametric ANOVA test. Additionally, discriminant function analyses were performed.

RESULTS

We have found the most elevated macrophage numbers in the groups of women with endometriosis. IL-1beta did not present any statistically significant values differentiating the analysed subgroups. IL-6 (110.0 pg/ml) and TNF-alpha exhibited the highest concentrations (statistically significant) in a group of fertile women with endometriosis. IL-8 clearly differentiated between the subgroups with infertility and sICAM-1 was statistically significantly elevated in the subgroups of infertile women. In the forward discriminant analysis, when subdividing the studied population according to its infertility status (we considered macrophages, IL-8 and IL-6 in order of probability values), we have found striking probability value of 92% for the correct classification into an infertile population.

CONCLUSION

Out of the range of the analysed factors we have found only the sICAM-1 to be singled out between the standard discriminant analysis and the forward one. However, this important flagging molecule might be of considerable value for discrimination between different types of pathology at the level of immune effector function. The increased levels of TNF-alpha and IL-6 signified a group of fertile women with endometriosis; however only IL-6 presented a discriminating value in multifunctional analysis of examined subgroups. The analysed range of factors had a greater tendency to discriminate between infertility status rather than endometriosis.

2,3,7,8-Tetrachlorodibenzo-p-dioxin increases glycodelin gene and protein expression in human endometrium

CONTEXT

Glycodelin (GdA) is an immunosuppressive endometrial glycoprotein critical for embryonic implantation and pregnancy establishment.

OBJECTIVE

The aim of the present study was to examine the effect of dioxin [2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)] on GdA production in human endometrial cells.

DESIGN

Controlled endometrial explant (EE) and cell cultures were used in this study.

SETTING

Work was conducted at university hospital research laboratories in Bern, Switzerland, and in San Francisco, California.

PATIENTS

Ovulatory women provided endometrial biopsies in the proliferative or secretory phase.

INTERVENTION(S)

EEs and cells were cultured without and with TCDD.

MAIN OUTCOME MEASURE(S)

GdA protein and gene expression were quantified.

RESULTS

A 2.5-fold increase in GdA production was demonstrated in EEs treated with 10 nm TCDD for 9 d. Fluorography revealed a 3- to 4-fold increase in new GdA biosynthesis and secretion in TCDD-treated endometrial epithelial cells. Because the action of dioxin is mediated by the aryl hydrocarbon receptor (AhR), we ascertained that primary epithelial and Ishikawa cells express AhR. Dose responses to TCDD and expressed AhR were established in transiently transfected Ishikawa cells using luciferase fusion vectors containing 1.0 kb of 5' flanking DNA relative to the GdA transcriptional start site but not when shorter promoter constructs were used. A dioxin response element was mapped to nucleotides -539 to -533 of the gene promoter and verified by site-directed mutagenesis.

CONCLUSIONS

We demonstrated a direct AhR-mediated effect of dioxin on GdA gene transcription and protein secretion that might influence human female fertility.

Elevated levels of macrophage migration inhibitory factor in the peripheral blood of women with endometriosis

OBJECTIVE

To evaluate the concentrations of macrophage migration inhibitory factor (MIF) in the peripheral blood of normal women and patients with endometriosis.

DESIGN

Retrospective study using ELISA to measure peripheral blood MIF.

SETTING

Gynecology clinic and human reproduction research laboratory.

PATIENT(S)

Thirty-eight normal women and 55 women with endometriosis.

INTERVENTION(S)

Peripheral blood samples were obtained a few days before laparoscopy.

MAIN OUTCOME MEASURE(S)

The MIF concentrations in blood serum.

RESULT(S)

This current study showed a 364% increase in MIF concentrations in women with endometriosis as compared to normal women. A significant increase was seen in endometriosis stages I-II, but a more marked increase was observed in the more advanced stages of the disease (III-IV). Both fertile and infertile women with endometriosis had higher levels of MIF than normal controls, but the difference was more significant in infertile women with endometriosis. Women with endometriosis with no pelvic pain had higher levels of MIF than normal controls, but a more significant increase in MIF levels was observed in women with endometriosis reporting pelvic pain.

CONCLUSION(S)

This study showed a marked increase in MIF concentrations in the peripheral blood of women with endometriosis and a relationship with disease progress, and suggests that MIF may be involved in endometriosis-related pain and infertility.

In utero exposures and the incidence of endometriosis

OBJECTIVE

To investigate the relation between the fetal environment and endometriosis.

DESIGN

Prospective cohort study.

SETTING

Nurses' Health Study II with 10 years of follow-up.

PARTICIPANT(S)

Eighty-four thousand, four hundred forty-six women aged 25-42 who had never been diagnosed with endometriosis, infertility, or cancer at baseline in 1989.

MAIN OUTCOME MEASURE(S)

Incidence of laparoscopically confirmed endometriosis according to birthweight, prematurity, multiple gestation, diethylstilbestrol (DES) exposure, and having been breastfed.

RESULT(S)

During 566,250 woman-years of follow-up, 1,226 cases of laparoscopically-confirmed endometriosis were reported among women with no past infertility. After adjusting for age, calendar time, parity, race, and body mass index at age 18, we observed a linear increase in the incidence rate with decreasing birthweight (rate ratio [RR] = 1.3 for birthweight <5.5 pounds versus 7.0-8.4 pounds, 95% confidence interval [CI] = 1.0-1.8, P value, test for trend = .01). In addition, women who were born as one of a multiple gestation (i.e., twins or greater number) were at increased risk even after controlling for birthweight (RR = 1.7, CI = 1.2-2.5). The rate of endometriosis was also 80% greater among women exposed to diethylstilbestrol in utero (RR = 1.8, CI = 1.2-2.8). Neither premature delivery nor having been breastfed were associated with the incidence of endometriosis. None of these effect estimates were modified by infertility status at the time of endometriosis diagnosis.

CONCLUSION(S)

The fetal environment is associated with subsequent laparoscopically confirmed endometriosis in this cohort of US women.

Reproductive history and endometriosis among premenopausal women

OBJECTIVE

To clarify the temporal complexities of the relation between reproductive factors and endometriosis.

METHODS

We analyzed 10 years of prospective data from the Nurses' Health Study II cohort. Information was obtained through questionnaires sent every 2 years to 116,678 women aged 25-42 years when enrolled in 1989. Cox proportional hazards models were used to adjust for age, calendar time, and confounding variables.

RESULTS

During 726,205 woman-years of follow-up, 1,721 cases of laparoscopically confirmed endometriosis were reported among women with no past infertility. Greater incidence was observed among women with an earlier age at menarche (rate ratio of 1.3 comparing menarche at age < 10 to age 12 years; 95% confidence interval [CI] 1.0-1.8; P value, test for trend < .001) and shorter cycle length during late adolescence (rate ratio of 1.3 comparing < 26 days to 26-31 days; 95% CI 1.1-1.5). Time to cycle regularity was not associated with risk. Among parous women, a linear decrease in risk was observed with number of liveborn children (rate ratio of 0.5 comparing > 3 with 2 children; 95% CI 0.4-0.7; P value, test for trend < .001) and lifetime duration of lactation if time since last birth was less than 5 years (rate ratio of 0.2 comparing > 23 months with never; 95% CI 0.1-0.4; P value, test for trend < .001).

CONCLUSION

Hormonal and anatomical changes associated with menstruation and pregnancy may affect the rate of laparoscopically confirmed endometriosis. Within this cohort, risk was greatest among nulliparous women with earlier age at menarche and shorter menstrual cycles. Among parous women, parity and lifetime duration of lactation were associated with decreased risk.

The epidemiology of endometriosis

The epidemiologic study of endometriosis presents researchers with unique challenges. As a result, few well-designed studies have been published. The authors briefly describe the primary pathogenic hypotheses, discuss methodologic issues specific to endometriosis, and review the small body of literature addressing risk factors. Finally, they offer a brief interpretation of these findings and suggest hypotheses for future research.

Estradiol and interleukin-1beta exert a synergistic stimulatory effect on the expression of the chemokine regulated upon activation, normal T cell expressed, and secreted in endometriotic cells

Endometriosis, commonly associated with intraperitoneal inflammation, is estrogen dependent. Possible links between the immunoinflammatory and endocrine changes observed in endometriotic women have been poorly understood. In this study, we report that estradiol (E(2)) and IL-1beta exert a synergistic stimulatory action on RANTES (regulated upon activation, normal T cell expressed, and secreted) expression by endometriotic cells. Treatment of endometriotic cells with IL-1beta had a dose-dependent effect on RANTES protein secretion and mRNA steady state levels, whereas cell treatment with E(2) or progesterone had no detectable effect. Interestingly, treatment of endometriotic cells with E(2) before stimulation with IL-1beta resulted in a further increase in RANTES protein secretion and mRNA steady state levels, compared with IL-1beta alone, whereas treatment with progesterone did not significantly affect cell responsiveness to IL-1beta. Assessment of RANTES mRNA half-life revealed that cell pretreatment with E(2) enhanced RANTES mRNA stability and increased gene transcription as shown by run-on analysis. Immunohistochemical analysis of RANTES in endometriotic tissue showed immunostaining to be predominant in the stroma with no noticeable differences in tissues from the proliferative and secretory phase of the menstrual cycle. This appears to be consistent with the cell culture data and indicates that RANTES expression in endometriotic tissue is not subject to cyclic variation. These findings reveal a new regulatory mechanism by which IL-1beta produced by activated macrophages can in synergy with ovarian and locally produced E(2) lead to enhanced macrophage and T-lymphocyte recruitment, thereby exacerbating the local immunoinflammatory process. Furthermore, the findings provide a further evidence for a close relationship between the endocrine and immunological changes observed in endometriosis.

Soluble interleukin-1 receptor type II blocks monocyte chemotactic protein-1 secretion by U937 cells in response to peripheral blood serum of women with endometriosis

OBJECTIVE

To assess the ability of peripheral blood serum from women with endometriosis to induce monocyte chemotactic protein-1 (MCP-1) secretion by monocytes and the putative role of the interleukin-1 (IL-1) system in endometriosis-associated monocyte activation.

DESIGN

Cultures of U937 monocytic cells exposed to serum from normal women (control group) or women with endometriosis.

SETTING

Gynecology clinic and human reproduction research laboratory.

PATIENT(S)

Seventy-nine women with endometriosis and 38 control women with no evidence of endometriosis at laparoscopy.

INTERVENTION(S)

Peripheral blood obtained a few days before laparoscopy.

MAIN OUTCOME MEASURE(S)

MCP-1 secretion in the culture medium and serum concentrations of soluble IL-1 receptor type II (sIL-1RII), IL-1beta, and IL-1alpha by ELISA or by enzyme immunometric assay.

RESULT(S)

Serum concentrations of sIL-1RII were significantly lower in women with stage I-II endometriosis than in control women, whereas serum concentrations of IL-1beta and IL-1alpha were comparable between the two groups. The serum of women with endometriosis induced higher secretion of MCP-1 by U937 cells than that of control women, particularly in the initial stages of endometriosis (stages I-II), and recombinant IL-1RII (rIL-1RII) significantly blocked that secretion.

CONCLUSION(S)

These findings point toward a deficiency in the mechanisms involved in the down-regulation of IL-1 actions at the systemic level and reveal sIL-1RII as a key factor involved in that process.

Spontaneous and stimulated secretion of monocyte chemotactic protein-1 and macrophage migration inhibitory factor by peritoneal macrophages in women with and without endometriosis

OBJECTIVE

To assess spontaneous and stimulated secretion of monocyte chemotactic protein-1 (MCP-1) and macrophage migration inhibitory factor (MIF) by peritoneal macrophages in women with and without endometriosis.

DESIGN

Macrophages were isolated from the peritoneal fluid and cultured for different periods of time (6, 20, and 44 hours) without any stimulation to determine spontaneous secretion of MCP-1 and MIF. Macrophages were also exposed to 1 microg/mL lipopolysaccharide for 6 hours to evaluate the stimulated secretion of these cytokines.

SETTING

Gynecology clinic and human reproduction research laboratory.

PATIENT(S)

Twelve fertile women and 11 women with endometriosis.

INTERVENTION(S)

Peritoneal fluid obtained at laparoscopy.

MAIN OUTCOME MEASURE(S)

Monocyte chemotactic protein-1 and MIF concentrations in the culture medium using ELISA.

RESULT(S)

Peritoneal macrophages of women with endometriosis demonstrated an increased capacity to secrete MCP-1 either spontaneously or after stimulation with lipopolysaccharide. They also showed a marked tendency for an increased secretion of MIF, but no statistically significant difference was found.

CONCLUSION(S)

Monocyte chemotactic protein-1 and MIF production by peritoneal macrophages may contribute to paracrine and autocrine activation and to macrophage accumulation in the peritoneal cavity of women with endometriosis. These mechanisms may exacerbate peritoneal inflammation and favor the growth of endometrial implants.

Decreased expression of the decoy interleukin-1 receptor type II in human endometriosis

Many of the biological changes occurring in the endometrium during the menstrual cycle bear a striking resemblance to those associated with inflammatory and reparative processes. Hence, it would not be surprising to find that cytokines known for their pro-inflammatory properties, such as interleukin-1 (IL-1), could play a key role in the physiology of this tissue and that their action would be tightly controlled by local mechanisms. In the present study, immunohistochemical and Western blot analyses show that in normal women (n = 39), the endometrial tissue expresses, in a cycle-dependent manner, the IL-1 receptor type II (IL-1RII), a molecule of which the only biological property known to date is that of capturing IL-1, inhibiting thereby its binding to the functional type I IL-1 receptor. IL-RII immunostaining was particularly intense within the lumen of the glands and at the apical side of surface epithelium. Interestingly, the intensity of staining was markedly less pronounced in the endometrium of women with endometriosis (n = 54), a disease believed to arise from the abnormal development of endometrial tissue outside the uterus, especially in the early stages of the disease (stages I and II). This study is the first to show the local expression in endometrial tissue of IL-1RII, a potent and specific down-regulator of IL-1 action and its decreased expression in women suffering from endometriosis.

Effect of hormonal agents on monocyte chemotactic protein-1 expression by endometrial epithelial cells of women with endometriosis

OBJECTIVE

To assess whether hormonal agents used in the medical treatment of endometriosis, such as danazol and GnRH agonist, exert direct regulatory action on monocyte chemotactic protein-1 (MCP-1) expression by endometrial epithelial cells.

DESIGN

Primary cultures of epithelial cells isolated from human endometrium were exposed to different concentrations of cytokines and steroid hormone analogs. Expression of MCP-1 was analyzed at the levels of protein and messenger RNA.

SETTING

Gynecology clinic and laboratory of endocrinology of reproduction.

PATIENT(S)

Women presenting for infertility or pelvic pain in whom endometriosis was diagnosed by using laparoscopy.

INTERVENTION(S)

Endometrial tissue biopsy performed at laparoscopy.

MAIN OUTCOME MEASURE(S)

Secretion of MCP-1 protein was measured by using enzyme-linked immunosorbent assay, and mRNA steady-state levels were measured by performing Northern blot analysis.

RESULT(S)

Buserelin acetate, a GnRH agonist (0.1-10 ng/mL), had no significant effect on MCP-1 expression, whereas danazol (10(-7)-10(-5) M), a testosterone analog, and dexamethasone, an anti-inflammatory glucocorticoid hormone (10(-12)-10(-6)M), showed a direct and a dose-dependent inhibitory effect on MCP-1 expression. This effect occurred at the level of protein and mRNA.

CONCLUSION(S)

The findings of the study may affect understanding of the mechanisms by which hormonal treatments act on endometriosis and influence its clinical manifestations.

Whole explants of peritoneum and endometrium: a novel model of the early endometriosis lesion

OBJECTIVE

To determine whether whole fragments of endometrium can adhere to peritoneum with intact mesothelium.

DESIGN

Tissue culture and immunohistochemical study.

SETTING

University medical center.

PATIENT(S)

Reproductive-age women undergoing surgery for benign conditions.

INTERVENTION(S)

Explants of human peritoneum from the anterior abdominal wall and the posterior surface of the uterus were cultured with whole fragments of mechanically dispersed endometrium.

MAIN OUTCOME MEASURE(S)

Adhesion of endometrial fragments to the surface of the peritoneum was evaluated. Adherent endometrium was identified with the use of the dissecting microscope and by the performance of serial sections of the peritoneum explants. Immunohistochemical staining of the mesothelium with antibodies to cytokeratin was used to ensure an intact layer of mesothelium beneath the endometrial implants. Transmission electron microscopy also was used to evaluate this adhesion process.

RESULT(S)

Endometrium was identified attached to the surface of the peritoneum. Most of the implants did not have identifiable mesothelium beneath them, but most had intact mesothelium running up to the point of attachment. Approximately 10% of the endometrial implants had intact mesothelium at the site of attachment. Endometrial stromal cells, and not epithelium, attached to the mesothelium.

CONCLUSION(S)

Endometrium can attach to the mesothelial surface of the peritoneum. Endometrial stromal cells are involved in this attachment. Invasion through the mesothelium seems to occur rapidly.