Expression of interleukin-8 and monocyte chemotactic protein-1 in adenomyosis

BACKGROUND: To clarify the inflammatory nature of adenomyosis, we aimed to investigate the expression of interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) by immunohistochemistry to determine their putative role in pathophysiology of adenomyosis. METHODS: Adenomyosis samples, with their eutopic endometrium, were collected from 30 women undergoing hysterectomy. Endometrium from 27 women without adenomyosis were also collected as a control group. Samples were grouped according to the menstrual cycle phase and examined by immunohistochemistry for IL-8 and MCP-1. RESULTS: In normal endometrium, secretory phase samples expressed higher levels of epithelial IL-8 than in proliferative phase samples (P = 0.01), and we observed a trend for an increased epithelial MCP-1 expression in the secretory phase samples compared with the proliferative phase samples (P = 0.07). Endometrial samples of women with adenomyosis did not show the same cyclic variation. In the secretory phase, eutopic endometrium of women with adenomyosis expressed lower levels of epithelial IL-8 and MCP-1 compared with normal endometrium (P < 0.05). The expression of epithelial IL-8 and MCP-1 was higher in the adenomyosis foci than the eutopic endometrium (P < 0.05). CONCLUSIONS: These findings may indicate that an intrinsic abnormality of inflammatory response may be present in eutopic endometrium of women with adenomyosis, and IL-8 and MCP-1 may contribute to the pathophysiology of adenomyosis.     

子宫内膜及异位灶趋化因子受体转录在子宫内膜异位症发病中的作用

目的：探讨子宫内膜异位症患者在位内膜及异位灶18种趋化因子受体的转录特征，以揭示趋化因子受体及其配体在子宫内膜异位症发生发展中的作用。方法：以正常子宫内膜为对照，半定量RT-PCR检测子宫内膜异位症患者在位内膜及异位灶18种趋化因子受体mRNA的表达水平，并比较其差异。结果：与正常子宫内膜相比，子宫内膜异位症患者在位子宫内膜CCR6、CCR8、CCR9、CX3CR1表达明显升高（P＜0．05）。与在位内膜相比，异位灶CCR4、CCR8、CCR9、CXCR1表达显著升高（P＜0．05）。结论：在位子宫内膜CCR6、CCR8、CCR9、CX3CR1高表达，可能参与子宫内膜异位症的发生；异位灶CCR4、CCR8、CCR9、CXCR1高表达，可能参与子宫内膜异位症的进一步发展。     

血管内皮生长因子在子宫内膜异位症发病中的作用

目的探讨血管内皮生长因子(vascularendothelialgrowthfactor,VEGF)在子宫内膜异位症(endometriosis,EM)发病中的作用。方法应用免疫组织化学方法并结合图像分析技术。结果正常子宫内膜和EM在位内膜腺上皮细胞的VEGF随月经周期呈现规律性变化,分泌期腺上皮VEGF蛋白表达量显著高于增殖期(P<0.05)。在增殖期,EM在位子宫内膜腺上皮VEGF的表达与正常子宫内膜相比无明显差别,但在分泌期,EM在位子宫内膜腺上皮细胞中VEGF的表达强度明显高于正常子宫内膜(P<0.01)。EM在位内膜腺上皮的VEGF含量显著高于同组卵巢子宫内膜异位囊肿的异位腺上皮(P<0.01)。结论表明VEGF的表达异常与EM的发病有关。     

Phenotypic and functional studies of leukocytes in human endometrium and endometriosis

The aetiology of endometriosis, a common and disabling disorder, is presently unknown, although immune dysfunction could allow ectopic endometrial fragments to survive outside the uterine cavity. These studies investigate the relationship between leukocyte populations, steroid hormone receptor expression, proliferative activity, bcl-2 expression and apoptosis in eutopic and ectopic endometrium from women with endometriosis or adenomyosis at different phases of the menstrual cycle. Significantly increased oestrogen receptor expression, bcl-2 expression and numbers of CD8+ leukocytes were found in ectopic compared with eutopic endometrium in endometriosis, and CD56+ endometrial granulated lymphocytes (eGLs) were significantly reduced in ectopic endometrium. Apoptotic cells were rarely found in control and subject endometria. In contrast with endometriosis, adenomyotic lesions showed identical steroid hormone receptor expression, proliferative activity, bcl-2 expression and leukocyte subpopulations to eutopic endometrium, indicating different aetiologies for these disorders. The unusual CD56+ CD16- eGLs present in large numbers in late secretory phase eutopic endometrium were highly purified (>98%) by immunomagnetic separation. Except for a negligible cytotoxic activity of eGLs from early proliferative samples, cytotoxic activity of eGLs from non-pregnant endometrium during the menstrual cycle was comparable with those in peripheral blood, predominantly CD56+ CD16+ natural killer cells. eGLs from non-pregnant endometrium and early pregnancy showed a variable proliferative response to 5 and 100 U/ml interleukin-2 over 48-h and 120-h time courses. eGLs are evidently functionally important in the eutopic endometrium. Their absence in endometriotic lesions together with increased CD+8 T-cell numbers and increased oestrogen receptor and bcl-2 expression may have significant effects on the development and progression of endometriosis.     

GnRH II as a possible cytostatic regulator in the development of endometriosis

BACKGROUND: GnRH II is the second form of GnRH and is widely distributed in peripheral tissues of the female reproductive tract as well as in the central nervous system. In the present study, we studied the possible implication of GnRH II in endometriosis. METHODS: Effects of GnRH II on 5-bromo-2'-deoxyuridine (BrdU) uptake by cultured endometriotic stromal cells were examined. Effects of GnRH II on interleukin (IL)-1beta-induced expression of cyclooxygenase (COX)-2 and IL-8 were also studied. mRNA levels of GnRH I, GnRH II, type I GnRH receptor and type II GnRH receptor were determined by real-time quantitative RT-PCR in endometrial tissues of women with or without endometriosis and in endometriotic tissues. RESULTS: GnRH II dose-dependently suppressed BrdU uptake by endometrial stromal cells. Treatment with IL-1beta markedly increased mRNA levels of COX-2 and IL-8 in endometrial stromal cells and IL-8 protein secretion by these cells, while these increments were significantly suppressed by supplementation with GnRH II. The mRNA levels of GnRH II were lower in endometrial and endometriotic tissues of women with endometriosis than in endometrial tissues of women without endometriosis, both in the proliferative phase and the secretory phase. In addition, as for GnRH I, type I GnRH receptor and type II GnRH receptor, the mRNA levels were lower in endometrial tissues of women with endometriosis than in those without endometriosis in the secretory phase. CONCLUSIONS: In the light of the demonstrated antiproliferative and anti-inflammatory effects of GnRH II on endometrial stromal cells, the lower expression of GnRH II in eutopic and ectopic endometrium of women with endometriosis suggests that endogenous GnRH II-mediated cytostatic regulation may be impaired in the development of endometriosis.     

Apoptosis and bcl-2 expression in normal human endometrium, endometriosis and adenomyosis

Apoptosis has been implicated in the pathogenesis of several diseases and is partly regulated by bcl-2, which blocks the apoptotic pathway and promotes cell survival. Apoptosis and bcl-2 expression were examined in paired eutopic and ectopic endometrium from women with endometriosis (n = 30 samples) or adenomyosis (n = 15 samples) and compared with control endometrium (n = 30 samples). Apoptotic cells were detected using the dUTP nick-end labelling (TUNEL) assay for DNA fragmentation; bcl-2 expression was demonstrated with a streptavidin- biotin peroxidase immunohistochemical technique. Apoptotic cells were rare in eutopic, ectopic and control endometrium; there were no significant differences between subject groups nor between eutopic and ectopic endometrium. Stromal bcl-2 expression increased in the late secretory phase in control and eutopic endometrium in endometriosis; double labelling studies revealed that most stromal bcl-2+ cells were leukocytes. Stromal bcl-2 expression in endometriotic foci was significantly increased compared with the paired eutopic endometrium, did not vary with menstrual cycle and included a significant population of non-leukocytic bcl-2+ stromal cells. In contrast, stromal bcl-2 expression in adenomyosis remained at low levels and did not show significant cyclical variation. Glandular epithelial bcl-2 expression also varied with menstrual cycle phase and peaked in the proliferative phase; in contrast, surface epithelial bcl-2 expression increased in the late secretory phase. Elevated stromal bcl-2 expression in ovarian endometriotic lesions could have implications for the growth and survival of ectopic endometrial tissue at these sites.      

Immunohistochemical characterization of proliferation, oestrogen receptor and progesterone receptor expression in endometriosis: comparison of eutopic and ectopic endometrium with normal cycling endometrium

Recent studies examining oestrogen and progesterone receptorstatus and the proliferative activity of endo-metriotic lesionshave produced conflicting reports. This study aimed to clarifythe receptor status and proliferative activity of eutopic andectopic endometrium from women with endometriosis and endometriumfrom normal women. Progesterone and oestrogen receptor expressionand proliferative activity were studied in eutopic and ectopicendometrium from 30 women with endometriosis and in endometriumfrom 30 normal cycling women using microwave-pretreated paraffin-embeddedsections stained with an avidin-biotin peroxidase technique.Progesterone and oestrogen receptor expression in the controlendo-metrium did not differ from that of eutopic endometriumfrom women with endometriosis. Oestrogen receptor expressionin ectopic endometrium increased from the proliferative to thelate secretory phase. Epithelial progesterone receptor expressiondecreased during the cycle. Oestrogen receptor expression inboth epithelium and stroma of ectopic endometrium was significantlyhigher than in eutopic endometrium throughout the cycle. Incontrast, stromal progesterone receptor expression tended tobe reduced in ectopic endometrium compared with eutopic tissue.Epithelial progesterone receptor expression was increased inectopic endometrium but only in the late secretory phase. Althoughproliferative activity in the epithelium of control and eutopicendometrium was reduced from the proliferative to the late secretoryphase, stromal activity did not vary. The proliferative activityin ectopic endometrium remained low and constant throughoutthe cycle. In the proliferative and early secretory phases,the proliferative activity of eutopic endometrium was increasedcompared with ectopic endometrium, but in the late secretoryphase, levels were comparable. These findings challenge previousreports which have suggested that oestrogen receptors are reducedin ectopic tissue. This may have clinical implications for thedevelopment of novel treatments for endometriosis.     

Urocortin 2 and urocortin 3 in endometriosis: evidence for a possible role in inflammatory response

Urocortin 2 (Ucn 2) and urocortin 3 (Ucn 3) are neuropeptides expressed by human endometrium. This study evaluated (i) the expression of Ucn 2 and Ucn 3 mRNA in endometriotic lesions and in endometrium of women with endometriosis; (ii) the effect of Ucn 2 and Ucn 3 on cytokines secretion from cultured endometrial stromal cells. Endometriotic tissue was collected from endometrioma (n=39); endometrial specimens were obtained from women with (n=39) and without (n=41) endometriosis throughout menstrual cycle. Tissue specimens were analysed for Ucn 2 and Ucn 3 mRNA expression and peptide localization; the effects of Ucn 2 or Ucn 3 on tumour necrosis factor (TNF-α) and interleukin (IL-4) secretion from cultured endometrial stromal cells was studied. Ucn 2 and Ucn 3 mRNA expression and localization were assessed by RT-PCR and by immuohistochemistry, respectively; cytokines secretion were measured by ELISA. Results showed that endometriotic tissue expressed both Ucn 2 and Ucn 3, with Ucn 3 expression higher in ectopic than in eutopic endometrium. Endometrial Ucn 2 mRNA expression in controls showed peak values at early proliferative phase, while in endometriotic patients low expression and no significant changes throughout menstrual cycle were observed. Endometrial Ucn 3 mRNA expression was highest in late secretory phase in controls, while in endometriotic patients low levels and no menstrual-cycle-related changes were found. When added to cultured endometrial cell cultures, Ucn 2 significantly increased TNF-α (P<0.01) and IL-4 (P<0.001), while Ucn 3 induced an increase of IL-4 secretion (P<0.01). In conclusion, endometriotic tissue expressed and localized Ucn 2 and Ucn 3; patients with endometriosis showed Ucn 2 and Ucn 3 mRNA expression in eutopic endometrium lower than in control group, with no endometrial cycle-related changes. Ucn 2 and Ucn 3-modulated TNF-α and IL-4 secretion from culture endometrial cells. These data suggest a possible involvement of Ucn 2 and Ucn 3 in the mechanisms of endometriosis.     

Characterization of Lymphocyte Subpopulations and T Cell Activation In Endometriosis

PROBLEM: Numerous studies have characterized the lymphocyte subpopulations in normal eutopic endometrium and suggested a role for the cytokine secretory products of these lymphocytes in regulating endometrial cell proliferation and differentiation. Recent studies have shown that ectopic endometrium contains a greater concentration of scattered stromal lymphocytes than does eutopic endometrium. However, the lymphocyte subpopulations and their activation status have not been characterized in ectopic endometrium. METHODS: We performed immunohistochemical studies on serial sections of proliferative and secretory phase eutopic endometrium and ectopic endometrium obtained during the proliferative phase using monoclonal antibodies to CD4 (T helper-inducer cells), CD8 (T cytolytic-suppressor cells), CD22 (B-cells), CD56 (natural killer cells), and VLA-1 (T-cell activation marker). RESULTS: Ectopic endometrium contained significantly more scattered stromal CD4, CD8, and activated T cells than did proliferative and secretory eutopic endometrium. There were more activated T-cells in proliferative than in secretory eutopic endometrium. Ectopic endometrium contained significantly fewer NK cells than proliferative and secretory endometrium. CONCLUSIONS: These results demonstrate that (1) the increased lymphocyte population in ectopic endometrium is due to increased numbers of CD4 and CD8 cells, and (2) a greater number of activated T cells are present in ectopic endometrium as compared to eutopic endometrium. Increased concentration of stromal T cells and enhanced VLA-1 expression in ectopic endometrium suggest that cytokine products of the activated T-cells may be involved in regulating cellular processes of endometriosis tissue.     

Differential expression of interleukins (IL)-13 and IL-15 in ectopic and eutopic endometrium of women with endometriosis and normal fertile women

PROBLEM: Interleukins (IL) 13 and 15 are key regulators of inflammatory and immune responses, processes that are central to endometriosis and associated abnormalities. The present study examined (1) whether ectopic endometrial tissue expresses IL-13 and IL-15 (2) if their expression differs compared with matched eutopic endometrium and control endometrium from normal fertile women, and (3) if peritoneal fluids (PF) content of these cytokines reflects the disease compared with PF from women with peritoneal adhesions unrelated to endometriosis and those without pelvic pathology. METHODS: The expression of IL-13 and IL-15 mRNA and protein was determined using quantitative RT-PCR, ELISA and immunohistochemistry. RESULTS: Ectopic endometrium expresses IL-13 and IL-15 mRNA and protein with elevated levels compared with eutopic and control endometrium, irrespective of the phases of the menstrual cycle, with predominance in IL-13 expression. Endometrial epithelial cells were found to be the primary site of IL-13 and IL-15 expression. The PF content of IL-13 and IL-15 show a trend toward higher concentrations in women with adhesion and endometriosis, respectively, compared with fertile control without pelvic pathology. CONCLUSION: Interleukins 13 and 15 are expressed in ectopic endometrium and present in PF of women with endometriosis and their elevated expression in ectopic endometrium suggests that these cytokines play a key role in local inflammatory/immune responses that are critical in endometriosis-associated abnormalities.     

The macrophage stimulating protein/RON system: a potential novel target for prevention and treatment of endometriosis

Our recent DNA microarray analysis using tissue obtained by laser capture microdissection (LCM) identified up-regulation of RON (a tyrosine kinase receptor) during the late secretory phase in eutopic endometrial epithelial cells from patients with deep endometriosis compared with control endometrium from women with macroscopically normal pelvic cavities. In the present study, we further investigated mRNA expression of RON and its ligand, macrophage stimulating protein (MSP), in deep endometriotic lesions, eutopic endometrium from patients with deep endometriosis and control endometrium by using LCM and quantitative real-time RT-PCR. MSP mRNA expression in endometrial epithelial cells was significantly up-regulated in endometriosis patients during the late secretory phase compared with expression in controls. Furthermore, we detected up-regulation of MSP mRNA in ectopic endometrial epithelial cells compared with matched eutopic endometrial epithelial cells within the same patients regardless of the menstrual phase. MSP has an intrinsically dual functional nature through its receptor RON-it is a trophic cytokine preventing apoptosis and a scatter factor promoting invasion, both of which may be necessary for the initial development and growth of endometriosis. The present findings suggest that the MSP/RON system may be involved in the pathophysiology of endometriosis.     

GnRHⅡ蛋白在子宫内膜异位症患者中的表达及意义

目的：检测GnRHⅡ蛋白在子宫内膜异位症患者异位子宫内膜、在位子宫内膜和正常子宫内膜中的表达情况,同时分析其表达是否与子宫内膜月经周期有关。方法：采用免疫组织化学SP法检测GnRHⅡ蛋白在异位内膜、在位内膜及正常子宫内膜组织中的表达情况,并分析和比较其表达是否有差异。结果：GnRHⅡ蛋白在子宫内膜异位症患者异位、在位子宫内膜及正常子宫内膜中均有表达,阳性表达定位于子宫内膜腺体及间质细胞的细胞质;GnRHⅡ蛋白在异位内膜、在位内膜及对照组正常内膜的表达依次增强,两两比较差异有统计学意义（P＜0.05）;GnRHⅡ蛋白在正常子宫内膜分泌期表达强于增生期（P＜0.05）,且以分泌早中期最强,显著强于增生期和分泌晚期（P＜0.01）,而异位组或在位组的分泌期与增生期比较,差异无统计学意义（P＞0.05）。结论：GnRHⅡ蛋白在子宫内膜异位症的发病中以及在人类月经生理方面可能起重要作用。     

Distribution of cyclooxygenase-2 in eutopic and ectopic endometrium in endometriosis and adenomyosis

The objective of this study was to determine the distribution of cyclooxygenase-2 (COX-2) in eutopic and ectopic endometria in endometriosis and adenomyosis. The subjects were 35 patients with endometriosis diagnosed by laparoscopy, 33 patients with histologically confirmed adenomyosis and 50 female controls with normal fecundity. Expression of COX-2 was immunohistochemically investigated in tissues from eutopic endometrium and myometrium and ectopic endometrium of the wall of ovarian chocolate cysts using polyclonal antibody. Surface epithelial cells, endometrial glandular epithelial cells or stromal cells were assessed. Cells were semi-quantitatively assessed on a scale of 1 to 5 using a nomogram created from positive cell count and the degree of staining. COX-2 expression in surface and glandular epithelia of the control group varied markedly during the menstrual cycle. It was lowest in the early proliferative phase and gradually increased thereafter. It remained high throughout the secretory phase. However, in patients with endometriosis, expression of COX-2 in glandular epithelium was higher than that in the control group, though it varied throughout the menstrual cycle. On the other hand, there was no variation in expression of COX-2 in the adenomyosis group during the menstrual cycle, and it was lower than that in the endometriosis group in all phases. Pronounced COX-2 expression was observed in glandular cells from ectopic endometrial tissue of ovarian chocolate cyst walls in all cases regardless of the menstrual phase. In summary, increased COX-2 expression in eutopic and ectopic endometria was believed to be strongly correlated with pathological abnormalities in these disorders.     

Correlation between decreased type-II interleukin-1 receptor and increased monocyte chemotactic protein-1 expression in the endometrium of women with endometriosis

PROBLEM: Monocyte chemotactic protein-1 (MCP-1), a potent inducer of macrophage recruitment and activation, is overexpressed in the eutopic endometrium of women with endometriosis. Eutopic endometrial cells of women with endometriosis secrete higher levels of MCP-1 than those of normal women, following stimulation with interleukin-1 (IL-1). The aim of this study was to examine whether there is any correlation between the expression of IL-1 receptor type II (IL-IRII), a specific downregulator of IL-1 activity, and that of MCP-1 in the eutopic endometrium of women with endometriosis. METHOD OF STUDY: Endometrial biopsies of 46 women with endometriosis and 22 healthy women were evaluated simultaneously for IL-1RII and MCP-1 expression by immunohistochemistry. RESULTS: Our study revealed a highly significant correlation between the decreased expression of IL-1RII and the increased expression of MCP-1 in the endometrial tissue of women with endometriosis (Spearman correlation coefficient r = -0.377, P = 0.002), particularly in the initial stages of the disease (stages I and II; r = - 0.368, P = 0.020 and r = -0.480, P = 0.002, respectively). Furthermore, this correlation was observed in the proliferative (r = -0.366, P = 0.047) and the secretory phases (r = -0.321, P = 0.049) of the menstrual cycle. CONCLUSIONS: These results suggest that the reduced capability of endometrial tissue to downregulate IL-1 proinflammatory effects may be involved in the increased expression of MCP-1 in the endometrium of women with endometriosis and the establishment of an inflammatory state. The results also indicate a sustained process of cell activation throughout the menstrual cycle.     

The expression profile of micro-RNA in endometrium and endometriosis and the influence of ovarian steroids on their expression

MicroRNAs (miRNAs), through mRNA degradation or repression, act as key regulator of gene expression. Our aim was to identify specific miRNAs that are expressed in endometrium of women with and without endometriosis. We profiled the expression of 287 miRNAs in paired eutopic and ectopic endometrium and isolated endometrial cells using microarray and validated the expression of selected miRNAs using real-time PCR. On the basis of global normalization, 65 of these miRNAs were identified to be expressed above the threshold levels set during the analysis in the endometrium of women without endometriosis with a progressive decline in expression in paired eutopic and ectopic endometrium. Statistical analysis (ANOVA) identified 48 of these miRNAs as differentially expressed among these tissues and 32 miRNAs between isolated endometrial stromal cell (ESC) and glandular epithelial cell (GEC) (P < 0.05). The expression of hsa-miR20a, hsa-miR21, hsa-miR26a, hsa-miR18a, hsa-miR206, hsa-miR181a and hsa-miR142-5p, predicted to target many genes, including TGF-betaR2, ERalpha, ERbeta and PR, respectively, was validated in these tissues and cells using real-time PCR. Treatment of ESC and GEC with 17beta-estradiol and medroxyprogesterone acetate (10(-8) M) differentially regulated the expression of hsa-miR20a, hsa-miR21 and hsa-miR26a, which in part reversed following co-treatment with ICI-182780 and RU-486 (10(-6) M), respectively (P < 0.05). In conclusion, we provided evidence for the expression of a number of differentially expressed miRNAs in eutopic/ectopic endometrium and isolated endometrial cells, opening up the possibility that aberrant/altered expression of some miRNAs whose expression is regulated by the ovarian steroids may influence the expression of specific target genes with central roles in normal endometrial cellular activities and pathogenesis of endometriosis.     

Differential expression and localization of de-novo synthesized endometriotic haptoglobin in endometrium and endometriotic lesions

Endometriosis protein-I (ENDO-I) mRNA expression and protein localization were evaluated using in-situ hybridization and immunohistochemistry in endometriotic lesions and eutopic endometrium from women with endometriosis, and in eutopic endometrium from women without endometriosis (controls). When present, ENDO-I mRNA and protein were observed in the functionalis zone of endometrial stroma and the stroma of endometriotic lesions. Expression and localization differences were scored and statistically analysed. During the secretory stage, ENDO-I mRNA expression by endometriotic lesions and eutopic endometrium from women with disease was significantly greater than ENDO-I mRNA expression by proliferative stage eutopic endometrium from women with disease or eutopic endometrium from controls, regardless of cycle stage (P < 0.001). More ENDO-I protein was localized in endometriotic lesions and eutopic endometrium from women with disease than in eutopic endometrium from controls, regardless of cycle stage (P < 0.001). Differential expression and localization of ENDO-I may help develop minimally invasive diagnostic strategies for endometriosis. Further, as ENDO-I shares nucleotide sequence and amino acid sequence with hepatic haptoglobin-which in certain disease states is immunosuppressive and angiogenic-differences in ENDO-I expression and localization in the peritoneal cavity may contribute to the pathogenesis of endometriosis and/or facilitate development of unprecedented diagnostic or therapeutic approaches for management of this enigmatic disease.     

Nitric oxide synthesis is increased in the endometrial tissue of women with endometriosis

BACKGROUND: Previous studies have shown that peritoneal macrophages from women with endometriosis produce excess nitric oxide (NO). This study was designed to quantify the amount of NO and determine the expression of endothelial (eNOS) and inducible NO synthases (iNOS) in women with and without endometriosis. METHODS: An enzyme-linked immunosorbent assay (ELISA) was performed on endometrial tissues obtained from controls (myoma, n = 30) and on eutopic/ectopic endometrial tissues from endometriosis patients (n = 34) to evaluate eNOS and iNOS protein concentrations in these endometrial tissues. A rapid-response chemiluminescence analyser was used to measure NO directly in fresh endometrial tissues. RESULTS: Mean (+/- SEM) levels of NO were significantly increased in the endometrial tissues of women with endometriosis (13.2 +/- 7.8 versus 19.8 +/- 12.6 nmol/g tissue; P = 0.016). Apparently higher levels of NO were found in ectopic compared with eutopic endometrium (P = 0.057). Endometrial tissues of women with endometriosis appeared to contain more iNOS than those of controls (3.6 +/- 2.2 versus 8.6 +/- 12.2 pg/ microg protein; P = 0.06), but no significant difference was found in eNOS levels. CONCLUSIONS: Greater amounts of NO and NOS are present in the endometrial tissues of women with endometriosis, implying a possible role for NO in the pathogenesis of endometriosis.