Surgical induction of endometriosis in the rabbit: effects on fertility and concentrations of peritoneal fluid prostaglandins

Diminished Ovarian Reserve in Endometriosis: Insights from In Vitro, In Vivo, and Human Studies-A Systematic Review

Endometriosis, a prevalent disorder in women of reproductive age, is often associated with undesired infertility. Ovarian reserve, an essential measure of ovarian function that is crucial for maintaining fecundity, is frequently diminished in women with endometriosis. Though the causative relationship between endometriosis and reduced ovarian reserve is not fully understood due to the lack of standardized and precise measurements of ovarian reserve, there is ongoing discussion regarding the impact of interventions for endometriosis on ovarian reserve. Therefore, in this review, we investigate articles that have related keywords and which were also published in recent years. Thereafter, we provide a comprehensive summary of evidence from in vitro, in vivo, and human studies, thereby shedding light on the decreased ovarian reserve in endometriosis. This research consolidates evidence from in vitro, in vivo, and human studies on the diminished ovarian reserve associated with endometriosis, as well as enhances our understanding of whether and how endometriosis, as well as its interventions, contribute to reductions in ovarian reserve. Furthermore, we explore potential strategies to modify existing therapy options that could help prevent diminished ovarian reserve in patients with endometriosis.

What We Have Learned from Animal Models to Understand the Etiology and Pathology of Endometrioma-Related Infertility

Endometrioma (OMA) is the most common subtype of endometriosis, in which the endometriotic lesions are implanted in the ovary. Women with OMA are usually associated with infertility, presenting with reduced ovarian reserve, low oocyte quantity and quality, and poor fertility outcomes. However, the underlying pathological mechanisms in OMA-related infertility are still unclear. Due to the limitations and ethical issues of human studies in reproduction, animal models that recapitulate OMA characteristics and its related infertility are critical for mechanistic studies and subsequent drug development, preclinical testing, and clinical trials. This review summarized the investigations of OMA-related infertility based on previous and latest endometrioma models, providing the possible pathogenesis and potential therapeutic targets for further studies.

Endometriosis: current challenges in modeling a multifactorial disease of unknown etiology

Endometriosis is a chronic inflammatory hormone-dependent condition associated with pelvic pain and infertility, characterized by the growth of ectopic endometrium outside the uterus. Given its still unknown etiology, treatments usually aim at diminishing pain and/or achieving pregnancy. Despite some progress in defining mode-of-action for drug development, the lack of reliable animal models indicates that novel approaches are required. The difficulties inherent to modeling endometriosis are related to its multifactorial nature, a condition that hinders the recreation of its pathology and the identification of clinically relevant metrics to assess drug efficacy. In this review, we report and comment endometriosis models and how they have led to new therapies. We envision a roadmap for endometriosis research, integrating Artificial Intelligence, three-dimensional cultures and organ-on-chip models as ways to achieve better understanding of physiopathological features and better tailored effective treatments.

Dose-Dependent Decreased Fertility in Response to the Burden of Endometriosis in a Murine Model

Endometriosis is a gynecological disease caused by the growth of endometrial cells outside the uterus leading to inflammation, pelvic pain, and infertility. The relationship between the amount of ectopic uterine tissue growth and the severity of symptoms is still unclear. The presence or degree of pain and infertility does not correlate with the stage of disease as currently defined. Here, we report a clear dose-response relationship between the amount of ectopic tissue transplanted and the reproductive outcomes in a murine model of endometriosis. Endometriosis was induced in mice using various amounts of transplanted uterine tissue. Four groups of mice consisted of a sham surgery control or those transplanted with 1, 2, or 4 endometrial segments of 5 mm each. Pregnancy rates were significantly lower in those transplanted with 2 or 4 segments compared to sham or the 1 segment groups. We demonstrate that infertility does correlate with the extent of active disease. Current clinical staging systems do not account for disease activity and may inappropriately weight sequela of disease. Early recognition and treatment in women may help to minimize the effect of endometriosis on fertility. Here, we describe a mouse model of endometriosis and infertility that may be useful to elucidate the mechanisms of infertility in endometriosis.

Development of a domestic animal model for endometriosis: Surgical induction in the dog, pigs, and sheep

Background:

Endometriosis affects one in ten women of reproductive age but it is diagnosed at advanced stages. Our objective was to develop a domestic animal model that would permit sequential assessment of endometriotic changes.

Materials and methods:

Surgical transplantation of endometrial tissue and fat (n = 4 grafts/tissue/animal) was done in dogs (n = 5), pigs (n = 4), and sheep (n = 5). Autologous grafts were sutured to the visceral (urinary bladder in dogs and pigs and uterus in sheep) and parietal peritoneum. Sham surgeries were performed (dogs and sheep n = 5 and pigs n = 3) by placing fat grafts alone. Plasma estrogen and progesterone concentration was performed prior to surgery and weekly following surgery until euthanasia. Animals were euthanized between 80 and 110 days after surgery. Gross and histopathologic features of endometriotic lesions were recorded.

Results:

A variety of lesions from transplanted endometrial grafts included endometriotic cysts, vesicles, solid lesions, or absence of lesions. The proportion of cysts was greater (p < 0.01) in dogs (18/20 grafts) than in pigs (5/16) and sheep (5/20). The area of endometriotic lesions at the time of euthanasia was greater than at the time of surgery in dogs (0.89 ± 0.11 cm2 vs 0.50 ± 0.09 cm2; p < 0.05), whereas, the size of lesions decreased (p < 0.05) by half or more in pigs and sheep. In dogs, endometrial cysts were characterized by simple cuboidal/columnar epithelium, endometrial glands, stromal tissue with hemorrhage and/or hemosiderin-laden macrophages, and smooth muscle cells.

Conclusion:

The development of endometriotic cysts was apparent in dogs than in sheep and pigs. Therefore, dog is a better domestic animal model for endometriosis.

Animal models of endometriosis: Replicating the aetiology and symptoms of the human disorder

Endometriosis is a chronic incurable disorder that affects 1 in 10 women of reproductive age: associated symptoms include chronic pain and infertility. The aetiology of endometriosis remains poorly understood but patients, clinicians and researchers are all in agreement that new non-surgical therapies are urgently needed to reduce the severity of symptoms. Preclinical testing of drugs requires the development and validation of models that recapitulate the key features of the disorder. In this review we describe the best-validated animal models (primate, rodent, xenograft) and their contributions to our understanding of the factors underpinning the development of symptoms. We consider the evidence that these models have provided the platform for identification of new therapeutic interventions and reflect on future directions for research and drug validation.

Endometrial receptivity in the eutopic endometrium of women with endometriosis: it is affected, and let me show you why

The endometrium maintains complex controls on proliferation and apoptosis as part of repetitive menstrual cycles that prepare the endometrium for the window of implantation and pregnancy. The reliance on inflammatory mechanisms for both implantation and menstruation creates the opportunity in the setting of endometriosis for establishment of chronic inflammation that is disruptive to endometrial receptivity, causing both infertility and abnormal bleeding. Clinically, there can be little doubt that the endometrium of women with endometriosis is less receptive to embryo implantation, and strong evidence exists to suggest that endometrial changes are associated with decreased cycle fecundity as a result of this disease. Here we provide unifying concepts regarding those changes and how they are coordinated to promote progesterone resistance and estrogen dominance through aberrant cell signaling pathways and reduced expression of key homeostatic proteins in eutopic endometrium of women with endometriosis.

Models of endometriosis and their utility in studying progression to ovarian clear cell carcinoma

Endometriosis is a common benign gynaecological condition affecting at least 10% of women of childbearing age and is characterized by pain--frequently debilitating. Although the exact prevalence is unknown, the economic burden is substantial (∼$50 billion a year in the USA alone) and it is associated with considerable morbidity. The development of endometriosis is inextricably linked to the process of menstruation and thus the models that best recapitulate the human disease are in menstruating non-human primates. However, the use of these animals is ethically challenging and very expensive. A variety of models in laboratory animals have been developed and the most recent are based on generating menstrual-like endometrial tissue that can be transferred to a recipient animal. These models are genetically manipulable and facilitate precise mechanistic studies. In addition, these models can be used to study malignant transformation in epithelial ovarian carcinoma. Epidemiological and molecular evidence indicates that endometriosis is the most plausible precursor of both clear cell and endometrioid ovarian cancer (OCCA and OEA, respectively). While this progression is rare, understanding the underlying mechanisms of transformation may offer new strategies for prevention and therapy. Our ability to pursue this is highly dependent on improved animal models but the current transgenic models, which genetically modify the ovarian surface epithelium and oviduct, are poor models of ectopic endometrial tissue. In this review we describe the various models of endometriosis and discuss how they may be applicable to developing our mechanistic understanding of OCCA and OEA.

Animal Models in Endometriosis Research

The initiation of endometriosis in women is difficult to investigate, because there is usually a delay of several years from the onset of lesion development to the clinical diagnosis. Animal models of endometriosis, on the other hand, provide an important contribution to the investigation of the disease pathogenesis and the efficacy of therapeutic intervention strategies.

Interplay between Endometriosis and Pregnancy in a Mouse Model

Objectives

To evaluate the effect of endometriosis on fertility and the levels of the IL-2 and IFN-γ in the peritoneal fluid in a mouse model; to evaluate the effect of pregnancy on endometriotic lesion growth, apoptosis and cell proliferation.

Study Design

Two month old C57BL/6 female mice underwent either a surgical procedure to induce endometriosis or a sham surgery. Four weeks after surgery mice were mated and sacrificed at day 18 of pregnancy. Number of implantation sites, fetuses and fetal weight were recorded. Endometriotic lesions were counted, measured, excised and fixed. Apoptosis and cell proliferation were evaluated in lesions by TUNEL and immunohistochemistry for PCNA respectively. Levels of IL-2 and IFN-γ were assessed by ELISA in the peritoneal fluid.

Results

Pregnancy rate (i.e. pregnant mice/N) decreased in mice with endometriosis. However there were no significant differences in resorption rate, litter size and pup weight between groups. IFN-γ augmented in endometriosis mice independently of pregnancy outcome. Additionally IFN-γ increased in pregnant endometriosis mice compared to pregnant sham animals. While IFN-γ increased in non pregnant versus pregnant mice in the sham group, IL-2 was increased in non pregnant mice in the endometriosis group. The size of endometriotic lesions increased in pregnant mice while apoptosis increased in the stroma and cell proliferation decreased in the epithelium of these lesions. Additionally, leukocyte infiltration, necrosis and decidualization were increased in the same lesions.

Conclusions

Pregnancy rate is reduced in this mouse model of endometriosis. Levels of IL-2 are increased in the peritoneal fluid of mice with endometriosis suggesting a role of this cytokine in infertility related to this disease. The size of endometriotic lesions is increased in pregnant mice; however pregnancy has a beneficial effect on lesions by decreasing cell proliferation and by increasing apoptosis, decidualization and necrosis.

Cellular and molecular basis for endometriosis-associated infertility

Endometriosis is a gynecological disease characterized by the presence of endometrial glandular epithelial and stromal cells growing in the extra-uterine environment. The disease afflicts 10%–15% of menstruating women causing debilitating pain and infertility. Endometriosis appears to affect every part of a woman’s reproductive system including ovarian function, oocyte quality, embryo development and implantation, uterine function and the endocrine system choreographing the reproductive process and results in infertility or spontaneous pregnancy loss. Current treatments are laden with menopausal-like side effects and many cause cessation or chemical alteration of the reproductive cycle, neither of which is conducive to achieving a pregnancy. However, despite the prevalence, physical and psychological tolls and health care costs, a cure for endometriosis has not yet been found. We hypothesize that endometriosis causes infertility via multifaceted mechanisms that are intricately interwoven thereby contributing to our lack of understanding of this disease process. Identifying and understanding the cellular and molecular mechanisms responsible for endometriosis-associated infertility might help unravel the confounding multiplicities of infertility and provide insights into novel therapeutic approaches and potentially curative treatments for endometriosis.

Pleural endometriosis in an aged rhesus macaque (Macaca mulatta): a histopathologic and immunohistochemical study

Endometriosis is defined as the presence of endometrial tissue outside the uterine cavity and is one of the most common reproductive abnormalities encountered in women as well as Old World primates. The majority of endometriosis cases in Old World primates occur within the abdominal cavity, with spread to extraabdominal sites considered to be a rare event. A 19-year-old multiparous female rhesus macaque (Macaca mulatta) presented to necropsy for difficulty breathing and weight loss. Grossly, the animal had marked abdominal endometriosis and severe hemoabdomen and hemothorax, the latter of which was accompanied by marked pleural fibrosis. Histologic examination confirmed the abdominal endometriosis and also revealed numerous uterine glands and stroma embedded within the pleural fibrosis. Rafts of endometrial tissue were present within pulmonary lymphatics and the tracheobronchial lymph nodes. Immunohistochemically, all ectopic endometrial tissue had varying degrees of positive immunoreactivity to cytokeratin, vimentin, progesterone and estrogen receptors, and calretinin but was negative for desmin and carcinoembryonic antigen. Pleural endometriosis is an extremely rare manifestation of endometriosis in nonhuman primates. This case report emphasizes lymphatic spread as a likely mechanism for extrauterine endometriosis.

Endometriosis and headache

Headache and endometriosis show some similarities in their clinical and epidemiological features that are probably due to the influence of female sexual hormones on both disorders. Epidemiological studies indicate that they are comorbid disorders. However, the nature of the comorbidity is not known with certainty, but a likely explanation may be common susceptibility genes. Another possibility is that, because they both are related to pain, increased pain sensitivity induced by one of the disorders may lead to a higher likelihood of developing the other, possibly mediated by nitrogen oxide or prostaglandins. A common link to the widespread use of estroprogestins may seem less probable. For physicians dealing with women with either of these disorders, awareness of the comorbidity may be helpful in the treatment of the patient.

Desenvolvimento de modelo experimental de endometriose em ratas

OBJETIVO: Desenvolver um modelo de endometriose experimental em ratas. MÉTODOS: Foram utilizadas 30 ratas adultas da linhagem Wistar. A técnica cirúrgica consistiu em laparotomia mediana com identificação do útero bicorno e ressecção de um segmento de 2 cm do corno uterino direito. Um retalho de 0,25 cm² foi retirado dessa estrutura e suturado na parede abdominal com a face endometrial voltada para a cavidade peritoneal. As ratas foram divididas aleatoriamente em dois grupos de acordo com o tempo para a reoperação: grupo 1 (n=15), reoperado em 30 dias, e grupo 2 (n=15), em 60 dias. No momento da segunda laparotomia os implantes foram avaliados macroscopicamente, ressecados e encaminhados para análise microscópica com coloração hematoxilina-eosina e imunohistoquímica (HEMA, AE1 e AE2). RESULTADOS: Os implantes se desenvolveram em 83,3 % do Grupo 1 e 71,4% no Grupo 2. Não houve diferença estatisticamente significativa entre o peso dos animals dos dois grupos. Também não houve diferença estatisticamente significativa no tamanho da área das lesões induzidas: no Grupo 1 a média foi 0,37 cm² e no Grupo 2, de 0,25 cm². Segundo a classificação histológica semi-quantitativa de Keenan (de acordo com a preservação da camada epitelial de endométrio), o Grupo 1 teve média de 1,9 e o Grupo 2, de 2,4. CONCLUSÃO: A técnica utilizada para o desenvolvimento de endometriose em ratas foi satisfatória.

Increased cell proliferation in experimentally induced endometriosis in rabbits

OBJECTIVE

To characterize the pattern of cell proliferation and apoptosis of eutopic and ectopic endometrium in rabbits after endometrium implantation for the experimental induction of endometriosis.

DESIGN

Animal experimental study.

SETTING

Sector of experimental surgery.

ANIMAL(S)

Twenty-female New Zealand rabbits.

INTERVENTION(S)

All animals underwent laparotomy for endometriosis induction by resection of one uterine horn, isolation of the endometrium, and fixation of tissue segment to the pelvic peritoneum. Two groups of 10 animals were sacrificed 4 and 8 weeks after endometriosis induction. The lesion was excised together with the opposite uterine horn for endometrial gland and stroma determination.

MAIN OUTCOME MEASURE(S)

Cell proliferation and apoptosis were determined in the eutopic and ectopic endometrium, and the cell proliferation index (CPI) and apoptotic index (AI) were calculated as the number of labeled cells per 1,000 cells. The tissue homeostasis index was the CPI/AI ratio. Glands and stroma were analyzed separately.

RESULT(S)

The CPI for ectopic tissue was increased compared with eutopic tissue, but there was no difference in the ectopic lesions between 4 and 8 weeks of induction. Considering only the AI, eutopic and ectopic endometrium did not differ after 4 weeks, but differed significantly in glandular tissue after 8 weeks. The tissue homeostasis index revealed cell proliferation in these tissues, with a CPI/AI more than 1.

CONCLUSION(S)

Ectopic lesions seem to have a higher CPI than eutopic endometrium, with uncontrolled tissue growth occurring in induced endometriotic lesions.

The aetiology and pathogenesis of endometriosis

It is 130 years since the first description of endometriosis and yet this enigmatic disease still continues to confound gynaecologists. In the last five years there has been evidence which suggests that endometriosis is a much more common finding in the pelvis than previously recognized and this has created conflict over the precise definition of the disease. Currently it is difficult for clinicians to be certain what constitutes endometriosis and what is the clinical and pathological significance of the visual diagnosis of the disease. This article will review the evidence about the pathological significance of the visual diagnosis of endometriosis. It will analyze the aetiological factors that predispose to the disease and evidence concerning its pathogenesis. Finally, it will discuss the evidence that points to a particular epithelium being the origin of endometriosis.

Functional imaging of estrogen receptors with radiolabeled-GAP-EDL in rabbit endometriosis model

RATIONALE AND OBJECTIVES

Endometriosis is a common women's health problem. Animal models provide an invaluable tool to study the natural history of endometriosis. We previously have reported that (99m)Tc-labeled glutamate peptide-estradiol ((99m)Tc-GAP-EDL) is a useful agent for imaging functional estrogen receptor (ER) via an ER-mediated process. This study was to evaluate the feasibility of using radiolabeled GAP-EDL to image ER-positive (ER +) endometriosis in nonprimate animal models.

MATERIALS AND METHODS

3-Aminoethyl estradiol (EDL) was conjugated to glutamate peptide (GAP) to yield GAP-EDL. In vitro cellular uptake studies of (99m)Tc and (68)Ga-GAP-EDL inhibition with cold estrone were conducted in 13,762 rat mammary tumor cells. To create a rabbit model with endometriosis, part of uterine tissue was dissected and grafted in the peritoneal wall. Eight weeks after surgery, scintigraphic images were obtained after intravenous injection of (99m)Tc-GAP-EDL (1 mCi/rabbit, intravenous) at 0.5-2.0 hours, and (68)Ga-GAP-EDL at 45 minutes. We also performed (68)Ga-GAP-EDL blocking study in rabbit model by using tamoxifen. The rabbits were sacrificed and the grafts were excised for histologic examination.

RESULTS

In vitro uptake study of (99m)Tc- and (68)Ga-GAP-EDL in 13,762 rat breast cancer cells showed gradually increasing uptake of both tracers. Accumulation of (68)Ga-GAP-EDL in 13,762 cells was inhibited with cold estrone in a dose-dependent manner. In the endometriosis model, the grafted uterine tissue could be visualized by (99m)Tc-GAP-EDL. Necropsy was performed at 2.5 hours after injection time. Four follicular endometrial lesions in eight implanted endometrial tissues were detected, and all lesions could be detected by (99m)Tc-GAP-EDL. Planar scintigraphy of uterus, ovary and implants of necropsy specimen revealed an increased uptake of (99m)Tc-GAP-EDL in comparison with surrounding abdominal wall tissue. Microscopic examinations support that (99m)Tc-GAP-EDL was accumulated in the microinvasive endometrial tissue. After blocking with tamoxifen, (68)Ga-GAP-EDL accumulation in the endometrial grafts could not be visualized, and endometrial tissue-to-normal tissue count ratios were statistically higher in a nonblocked image than that in the blocked image.

CONCLUSIONS

Endometriosis uptake of radiolabeled GAP-EDL was via an estrogen receptor-mediated process. Radiolabeled-GAP-EDLs are useful agents for imaging endometriosis.

Gene expression analysis of endometrium reveals progesterone resistance and candidate susceptibility genes in women with endometriosis

The identification of molecular differences in the endometrium of women with endometriosis is an important step toward understanding the pathogenesis of this condition and toward developing novel strategies for the treatment of associated infertility and pain. In this study, we conducted global gene expression analysis of endometrium from women with and without moderate/severe stage endometriosis and compared the gene expression signatures across various phases of the menstrual cycle. The transcriptome analysis revealed molecular dysregulation of the proliferative-to-secretory transition in endometrium of women with endometriosis. Paralleled gene expression analysis of endometrial specimens obtained during the early secretory phase demonstrated a signature of enhanced cellular survival and persistent expression of genes involved in DNA synthesis and cellular mitosis in the setting of endometriosis. Comparative gene expression analysis of progesterone-regulated genes in secretory phase endometrium confirmed the observation of attenuated progesterone response. Additionally, interesting candidate susceptibility genes were identified that may be associated with this disorder, including FOXO1A, MIG6, and CYP26A1. Collectively these findings provide a framework for further investigations on causality and mechanisms underlying attenuated progesterone response in endometrium of women with endometriosis.

MUC1 in endometriosis and ovarian cancer

Endometriosis is a chronic, debilitating disease, associated with pelvic pain and infertility. Recent epidemiological studies suggest that women with endometriosis are at increased risk for ovarian cancer. Although the causative factors for both endometriosis and ovarian cancer remain largely unknown, several similarities between the proposed etiology of ovarian cancer and the observed pathophysiology of endometriosis have been reported. MUC1 glycoprotein is present in endometriotic lesions and overexpressed in epithelial ovarian tumors. We are currently studying immunity to MUC1 antigen in newly emerging preclinical models for endometriosis and ovarian cancer and exploring the potential for immune therapy/prevention with MUC1 in both diseases.

Altered expression of HOXA10 in endometriosis: potential role in decidualization

Endometriosis is a poorly understood gynaecologic disorder that is associated with infertility. In this study, we examined the expression of HOXA10 in the eutopic endometrium of baboons with induced endometriosis. A decrease in HOXA10 mRNA was observed after 3, 6, 12 and 16 months of disease, which reached statistical significance at 12 and 16 months. HOXA10 protein levels were decreased in both the epithelial and stromal cells of the endometrium. Furthermore, expression of beta3 integrin (ITGB3), which is upregulated by HOXA10, was decreased, whereas EMX2, a gene that is inhibited by HOXA10, was increased. Next, methylation patterns of the HOXA10 gene were analysed in the diseased and control animals. The F1 region on the promoter was found to be the most significantly methylated in the endometriosis animals and this may account for the decrease in HOXA10 expression. Finally, we demonstrate that stromal cells from the eutopic endometrium of baboons with endometriosis expressed significantly higher levels of insulin-like growth factor binding protein-1 (IGFBP1) mRNA than disease-free animals in response to estradiol, medroxyprogesterone acetate and dibutyryl cAMP (H + dbcAMP). The functional role of HOXA10 in IGFBP1 expression was further explored using human endometrial stromal cells (HSC). Overexpression of HOXA10 in HSC resulted in a decrease of IGFBP1 mRNA, whereas silencing HOXA10 caused an increase of IGFBP1 mRNA, even in the presence of H + dbcAMP. These data demonstrate that HOXA10 negatively influences IGFBP1 expression in decidualizing cells. Thus, the decrease in HOXA10 levels may in part be involved with the altered uterine environment associated with endometriosis.

Two Unsuccessful Clinical Trials on Endometriosis and a Few Lessons Learned

In 1999, a phase II clinical trial on the use of fulvestrant to treat endometriosis was launched; yet after 7 years there is still no report on its outcome. In 2005, another trial on the use of raloxifene to treat endometriosis was terminated early due to unfavorable outcome. The two apparently unsuccessful clinical trials on endometriosis have taught us a few important lessons. First, we need to understand endometriosis through more basic research. We have also been reminded that human endometriosis trials differ from animal studies; anatomy and physiology are often divergent, and outcome measures are certainly different. Ectopic endometrium can differ significantly from eutopic tissue, and this issue needs to be more thoroughly explored. We believe human cell lines will prove to be an inexpensive and valuable tool for future preliminary evaluation of medical therapies as well as discerning pathophysiologic processes of the disease. Based on our current understanding of endometriosis, some concrete benchmarks can be established for testing or screening potential compounds in vitro. Finally, estrogen receptor modulators are often tissue-, cell-, and context-specific in their actions; they should not be simplistically grouped together nor should extrapolations from one compound to another be undertaken in a cavalier manner.

Animal models in endometriosis research

Endometriosis is a common gynaecological disease, defined as the presence of endometrial tissue outside the uterus, causing pelvic pain and subfertility in approximately 10% of women of reproductive age. Current therapies lead to pain relief, however, do not address the causes and entail severe side effects. Still little is known about the pathogenic processes leading to the development and maintenance of endometriosis. Because endometriosis occurs spontaneously only in humans and some non-human primates, animal models of induced endometriosis have been developed and are of high value for the evaluation of pathophysiological mechanisms underlying the development of this disease. These experimental models include the autotransplantation of uterine fragments into the peritoneal cavity of rodents and non-human primates or the heterotransplantation of human endometrial or endometriotic tissue to immunodeficient mice or onto the chicken chorioallantoic membrane (CAM). This review describes the animal models for endometriosis and assesses their different potentials and limitations in regard to endometriosis research, with the aim of developing novel non-invasive diagnostic tools and improved strategies for the treatment of endometriosis in women.

Development of an experimental model of endometriosis using mice that ubiquitously express green fluorescent protein

BACKGROUND

Aiming at improving an animal model of endometriosis, we developed a homologous mouse model using 'green mice' that ubiquitously express green fluorescent protein.

METHODS

Endometrial fragment obtained from estradiol (E2)-supplemented ovariectomized 'green mice' was minced and injected into the peritoneal cavity of ovariectomized wild-type mice. The recipient wild mice were raised with or without E2 supplementation for 2 weeks, and then were euthanized. Endometriotic lesions that developed in the abdomen were examined both macroscopically and microscopically under fluorescence, and weight of the lesions was measured.

RESULTS

The endometriotic lesions were more clearly detected under fluorescence imaging than by conventional macroscopic examination. Histologically, endometriotic lesions deriving from 'green mice' were sharply distinguished from surrounding host tissues under fluorescence microscopy. More lesions developed in E2-supplemented than control recipient mice. The measured fluorescence intensity of endometriotic lesions showed significant positive correlation with their weight (R=0.844, P<0.0001), and was significantly higher in E2-supplemented mice than in vehicle-supplemented mice (P=0.0062).

CONCLUSION

The present endometriosis model using 'green mice' would be useful for expeditious identification and quantitative evaluation of endometriotic lesions.

Increased frequency of migraine among women with endometriosis

BACKGROUND

Our aim is to assess the prevalence and characteristics of headache in patients with endometriosis compared with women without this disease.

METHODS

One hundred and thirty-three women with histologically proven endometriosis and 166 controls were interviewed by a neurologist experienced in headache diagnosis; the headache disorders were classified according to the 1988 International Headache Society criteria.

RESULTS

The prevalence of migraine was significantly higher among women with endometriosis [n = 51, 38.3%; 95% confidence interval (CI) 30.1-47.2%] than in controls (n = 25, 15.1%; 95% CI 10.0-21.4%) (P < 0.001). Migraine with aura was observed in 18 women with endometriosis (13.5%) and in two controls (1.2%; P < 0.001). The age at migraine onset was significantly lower in women with endometriosis than in controls (16.4 versus 21.9 years; P = 0.001). No significant difference was observed in pain intensity and attack frequency between the two groups; a trend for women with endometriosis to have longer unmedicated attacks was observed. No significant correlation was observed between attack frequency, unmedicated headache duration, migraine intensity and the severity of endometriosis.

CONCLUSION

Migraine is more frequent in women with endometriosis than in controls, although its presence and characteristics are not related to the severity of endometriosis.

Endometriosis

Endometriosis is an oestrogen-dependent disorder that can result in substantial morbidity, including pelvic pain, multiple operations, and infertility. New findings on the genetics, the possible roles of the environment and the immune system, and intrinsic abnormalities in the endometrium of affected women and secreted products of endometriotic lesions have given insight into the pathogenesis of this disorder and serve as the background for new treatments for disease-associated pain and infertility. Affected women are at higher risk than the general female population of developing ovarian cancer, and they also may be at increased risk of breast and other cancers as well as autoimmune and atopic disorders. Clinicians should assess and follow up affected women for these and other associated disorders. There will probably be a new repertoire of approaches for treatment and perhaps cure of this enigmatic disorder in the near future.

Animal studies in endometriosis: a review

Endometriosis is a common women's health problem that is characterized by the presence of tissue resembling endometrium outside the uterus. The condition causes painful periods, chronic pelvic pain, and subfertility, which are potentially debilitating; and it affects millions of women worldwide. The diagnosis is made on visual inspection of the pelvis, usually at laparoscopy. The natural history is unknown, and well-controlled experiments are difficult to perform because of the need for repeated surgical procedures to assess endometriotic lesions over time. Thus, despite over 50 years' research, the cause of endometriosis remains unclear, and treatment options are limited. Animal models provide an invaluable tool to study risk factors, prevalence, and the natural history of endometriosis especially in those menstruating nonhuman primates that develop the disease spontaneously. Many of the practical problems associated with studying the disease in humans can therefore be overcome. The pathophysiology of endometriosis can also be investigated and new treatments assessed in both nonprimates and nonhuman primates, with "disease" induced by placing autologous uterine tissue in ectopic sites, or human endometrium in the case of nude mice. However, although nonprimates have obvious advantages as a model, the extent to which the induced lesions are truly representative of the disease itself is debatable. This review explores the value of the experimental models that have been used to date.

An improved mouse model for endometriosis allows noninvasive assessment of lesion implantation and development

OBJECTIVE

To test whether fragments of human endometrium transduced with the green fluorescent protein (GFP) cDNA and transplanted into nude mice can be noninvasively visualized.

DESIGN

A murine experimental model for human endometriosis.

SETTING

A biotechnology company.

ANIMAL(S)

Ovariectomized nude mice.

INTERVENTION(S)

Whole fragments of human endometrium were transduced in vitro by adenoviral infection with the GFP cDNA before transplantation into nude mice. Animals were noninvasively and repeatedly imaged before lesion collection.

MAIN OUTCOME MEASURE(S)

Fluorescence of GFP-expressing human endometrial fragments was evaluated before transplantation into animals. Development of endometriotic lesions was monitored through direct visualization of fluorescent tissue in the living animal or through conventional dissection.

RESULT(S)

GFP gene transfer into whole endometrial fragments can be performed, and a high proportion of cells express the reporter gene. Fluorescent endometrial fragments implant in nude mice and form endometriotic-like lesions, which can be directly visualized through the skin of living mice using a simple imaging device.

CONCLUSION(S)

This improved mouse model allows noninvasive and dynamic studies of lesion implantation and development to be conducted. In addition to helping better understand the pathophysiology of the disease, this model represents a valuable preclinical tool for testing the efficacy of new drugs targeting endometriosis, which should ultimately accelerate their development phase.

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.

Endometriosis and infertility: a cause-effect relationship?

Two major methodological problems that impact clinical research in endometriosis are the absence of a low-cost, highly reliable method for diagnosing endometriosis and the possibility that endometriosis is actually multiple different diseases that we have not yet been able to differentiate. Animal models of endometriosis clearly demonstrate that advanced endometriosis causes reduced fertility. In humans, endometriosis and infertility are commonly associated. However, few data from high-quality clinical trials demonstrate that endometriosis causes infertility in humans. Future research should focus on the implications of the observation that, in ovarian endometriosis cysts, the epithelium is monoclonal. This observation suggests that nonrandom somatic mutations cause ovarian endometriosis cysts. If somatic mutations cause ovarian endometriosis cysts, it is likely that a small number of genes can be identified that play a central role in pathogenesis of this disease.

Implantation defects in infertile women with endometriosis

The endometrium undergoes characteristic histologic changes during the menstrual cycle as it prepares for embryo implantation. Historic and current data suggest the presence of a defined period of maximal uterine receptivity during the mid-secretory phase occurring between days 7 and 10 postovulation. In recent years, we and others have sought to define biochemical markers of receptivity that might be used to better understand this time of endometrial differentiation. Based on the work with cell adhesion molecules, we have discovered three different integrins that are only coexpressed during this time in the cycle when embryos will successfully implant. By studying the regulation of one of these, the alpha(v)beta3 integrin, and its extracellular matrix ligand, osteopontin (OPN), we have defined two separate regulatory pathways that may regulate endometrial receptivity. While alpha(v)beta3 expression appears to be stimulated by EGF or heparin-binding EGF, osteopontin is stimulated by progesterone. We now believe the former pathway is a paracrine-mediated signal, while the latter is a direct effect of progesterone on the estrogen-primed endometrial epithelium. In women with endometriosis, it appears that alpha(v)beta3 expression is reduced, while OPN expression is unaffected. Interestingly, binding of OPN to the surface epithelium appears quite limited when alpha(v)beta3 expression is lacking. Such evidence continues to reinforce the notion that endometrium from some women with endometriosis is dysfunctional and may account for the reduction in cycle fecundity noted in this group of patients.

The molecular basis for implantation failure in endometriosis: on the road to discovery

Endometriosis is a benign gynecologic disorder associated with pelvic pain and infertility, with the latter being due, in part, to failure of embryonic implantation in the maternal endometrium. Adequacy of the endometrium for fertility has been classically investigated by histologic evaluation of a mid-late luteal phase biopsy and, historically, normal histology has been reassuring. However, recent studies demonstrate histologically normal, but biochemically abnormal, endometrium during the window of implantation in some women with endometriosis. In the pregenomic era, a "one-by-one" approach has been adopted to investigate proteins and genes expressed in the window of implantation, and several genes or gene products have been found to be aberrantly expressed in endometrium of women with endometriosis either during the implantation window or at other times of the cycle. Some of these are related to failure of implantation, while others likely contribute to the establishment and growth of endometriotic lesions. The time has come for a genome-wide approach to evaluate uterine endometrium for embryonic implantation. Knowing the biochemical mechanisms underlying normal implantation and the abnormalities in endometriosis will facilitate development of new diagnostic criteria beyond histologic evaluation and will permit identification and validation of molecular targets for future drug discovery. This monograph reviews (a) some of the evidence of compromised fertility in women with endometriosis and treatments targeted to improve their fertility; (b) the concept of the window of implantation; (c) genes/gene products aberrantly expressed in endometrium during the window of implantation or other times of the cycle in women with endometriosis; and (d) the use of microarray technology to investigate endometrial gene expression in human endometrial stromal cells and preliminary data resulting from a collaborative consortium effort of a genome-wide investigation of gene expression in the window of implantation of women with versus without endometriosis.

Medical management of endometriosis and infertility

OBJECTIVE

To review the literature on the use of medical management of endometriosis and infertility.

DESIGN

Literature review.

RESULT(S)

Endometriosis is a common finding in women with infertility, but the mechanism by which it renders a woman infertile remains unclear. Despite many years of controversy and debate, there remains a strong bias against medical treatment for endometriosis-associated infertility. A review of the current literature suggests that medical management of endometriosis may be effective in selected patients and in certain settings, including patients undergoing IVF.

CONCLUSION(S)

A closer look at the question of medical management of endometriosis reveals that much remains to be learned before a final decision can be made about the use of medical therapies, such as GnRH agonists, for endometriosis and associated infertility.

Transplantation of cultured explants of human endometrium into nude mice

The objective of this study was to analyse the histological and immunohistochemical characteristics of cultured explants of human endometrium transplanted into nude mice. Biopsies of eutopic endometrium were taken from six patients during laparoscopic surgery and classified according to the phase of the cycle. All the explants were cultured with oestrogen and progesterone for 24 h before transplantation into 15 mice. Four mice were grafted with explants of menstrual endometrium, four with explants of late proliferative endometrium, and seven with explants of late secretory-premenstrual endometrium. Typical endometrial glands and stroma were observed in 87% of cases 3 weeks after the transplantation. All the grafts revealed histological characteristics of the proliferative phase, even when the endometrial biopsy was taken during the late secretory phase. Immunohistochemical studies revealed that the proliferation index was high, whatever the menstrual phase of the endometrial biopsy. An extensive vascular network developed at the interface between the graft and the surrounding tissue. Vascular endothelial growth factor (VEGF) positive stained cells were observed in all grafts, the VEGF score being significantly higher in epithelial cells than in stromal cells. In conclusion, human endometrial explants, cultured for 24 h, could be successfully transplanted into nude mice. Immunohistochemical studies proved that human cultured endometrial tissue could not only survive in nude mice but could also become very active and develop characteristics different from the tissue of origin. An active vascular network is a necessary condition for the survival of the graft and may be explained by the high VEGF content.

The SCID mouse: an experimental model for endometriosis

The purpose of this study was to validate the suitability of the severe combined immunodeficient (SCID) mouse as an experimental model for endometriosis, by defining the morphological and histological features of induced endometrial implants, and characterizing specific biochemical properties of these implants. Human secretory endometrial tissues were injected into the peritoneal cavity of SCID/SCID CB17 mature female mice. Successful peritoneal implantation was observed in 55 of 57 (96.5%) SCID mice and consisted of circumscribed elevated nodules. Haematoxylin-eosin staining of implanting lesions demonstrated the presence of endometrial glandular tissue in a mixed background of stromal and inflammatory cells. When progesterone was administered to mice, epithelial glands underwent well-defined secretory changes. Immunohistochemical analysis using polyclonal human pan-cytokeratin antibodies demonstrated selective positive staining in the glandular epithelium of the human implants with none in the surrounding stroma. In-situ hybridization analysis using complement component 3 cDNA radiolabelled riboprobes yielded significantly more intense signals in glands compared to stroma. As human endometrial implants in SCID mice were shown to retain specific histological, functional and biochemical properties, we conclude that the SCID mouse is an attractive animal model for the study of endometriosis.

Effect of pelvic endometrial implants on overall reproductive functions of female rats

The effects of pelvic endometrial implants on the overall reproductive potential of female rats were investigated. After homologous transplantation in the peritoneum, the ectopic endometrium developed into highly vascularized nodes that gradually increased in mass until the 9th week postsurgery and then plateaued. In the presence of these implants, overall reproductive function was adversely affected. The effect was of greatest magnitude during 50-70 days posttransplantation. As compared with values in corresponding controls, ovulation was reduced by 43% (6 of 14) (p < 0.05), mating rate was reduced by 44% (12 of 27) (p < 0.025), and premature termination of pregnancy occurred in 34% (5 of 15) of rats. Wastage of pregnancy, which included complete termination or reduction of fetal number, occurred during the postimplantation course of gestation. Furthermore, 100% of the rats with transplants failed to respond to the copulomimetic stimulation for the induction of pseudopregnancy (p < 0.01, compared with corresponding controls). However, on exposure to vasectomized males, 46% (6 of 13) of these rats exhibited development of pseudopregnancy (p < 0.05, compared with corresponding group receiving copulomimetic stimulation). Increased rate of mating failure and differential pseudopregnancy rates after copulomimetic and natural cervical stimulation suggest that the rats with endometrial explants possibly had an absence or a short appearance of behavioral estrus. Hormonal assessment during the preovulatory phase showed a tendency toward lower mean levels of preovulatory estradiol and significantly lower LH (p < 0.01) and progesterone (p < 0.01) concentrations. The adversely affected reproductive functions may be a secondary consequence of these altered endocrine milieus.

Induction of endometriosis and adenomyosis by transvaginal pituitary transplantation in mice with and without natural killer cell activity

PROBLEM

The aims of this study were to establish a mouse model of endometriosis and adenomyosis and to elucidate the necessity of reduced natural killer (NK)-cell and T-cell activities in the establishment of endometriosis and adenomyosis.

METHOD OF STUDY

Pituitary glands, submandibular glands, a hypothalami were transvaginally inoculated into the uteri of syngeneic female mice. Twenty weeks later, the recipient mice were sacrificed and examined.

RESULTS

Cysts, adhesion of the uteri to surrounding tissues, and adenomyosis had formed in the uteri of 7 (29.2%), 14 (58.3%), and 22 (91.7%) mice, respectively, out of 24 BALB/c mice after the transplantation of pituitary glands. Similar findings were obtained by experiments with C3H/He and C57BL/6 mice. In NK-cell-deficient C57BL/6-bgJ and T-cell-deficient BALB/c nu/nu mice, an increase in the formation of cysts, adhesion, and adenomyosis was not observed.

CONCLUSIONS

These findings indicate that transvaginal pituitary transplantation specifically induces cysts, adhesion, and adenomyosis. Reduced NK-cell activities may not be necessary in the primary development of endometriosis and adenomyosis.

Experimental model for endometriosis. Comparative histological study between the ectopic and eutopic endometrium

Thyrty-six rats werw implanted with endometrial squares (2 X 2mm) to the left parietal peritoneum and the right uterine horn was tied. The rats were mated for 20 days and then sacrificed. Topic and ectopic endometrial histological pattern were compared. There was a correlation between the histological pattern of the autografted endometrium and the eutopic endometrium im most rats, pregnant or not. This suggests that both responded in a similar way to the same endocrine stimuli. The experimental model for endometriosis admiting the histological correlation between the uterine endometrium and the ectopic is factible and it is easy to be repetead.

Inhibitory effects of a novel aromatase inhibitor, YM511, on growth of endometrial explants and insulin-like growth factor-I gene expression in rats with experimental endometriosis

Estrogen deprivation therapy effectively prevents progress of endometriosis but the precise mechanism by which estrogen stimulates growth of endometriotic implants is still unknown. We examined effects of hypoestrogenic state induced by ovariectomy, gonadotropin-releasing hormone agonist (leuprolide) or aromatase inhibitor (YM511), on growth of experimental endometrial explant, a section of endometrium transplanted under the renal capsule, in rats. Ovariectomy gradually reduced the volume of endometrial explants for 21 days. YM511 (0.1 mg/kg) and leuprolide (1 mg/rat) completely reduced volume of endometrial explants but they differed widely in the onset of inhibitory action. YM511 prevented growth of explants on day 4 but leuprolide had no inhibitory effect until day 15. YM511 dose-dependently reduced volume of endometrial explants and its minimum effective dose was 0.04 mg/kg. Insulin-like growth factor-I (IGF-I) mRNA expression in endometrial explant and uterus was examined on day 4. YM511 decreased IGF-I expression in endometrial explant and uterus by 58% and 48%, respectively. Reductions of the extent of IGF-I expression by YM511 and ovariectomy were comparable. A significant correlation between the volume and IGF-I mRNA expression in endometrial explant suggests that local expression of this gene may play an important role in stimulating growth of endometrial explants.

Pathophysiology. The biologic principles of disease

Endometriosis, although associated with a large variety of symptoms, primarily produces pain and infertility; however, the strong correlation with these disorders, along with basic questions as to why endometriosis develops, when does it become a disease status, and why it's associated with symptoms such as pain or infertility, are still not well understood. A better understanding of the relationship between disease and symptoms of endometriosis must be acquired if effective progress in the treatment of pain and infertility related to endometriosis is to be made.

Pathogenesis of endometriosis

This article reviews the pathogenesis of endometriosis, which involves retrograde dissemination of endometrium and/or development in situ by metaplasia, and there is evidence suggesting that genetic and hormonal factors may play a role. There is also substantial evidence that immunologic factors, namely peritoneal macrophages, T cells, natural killer cells, and soluble products secreted by these cells, are involved in the pathogenesis of endometriosis.

Continuous exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin inhibits the growth of surgically induced endometriosis in the ovariectomized mouse treated with high dose estradiol

The objectives of this study were to evaluate the effects of repeated injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the growth of endometriosis and the formation of adhesions in the mouse. Sexually mature female B6C3F1 mice (n = 19) were ovariectomized and subcutaneously implanted with a silastic capsule containing estradiol (E2). Uterine tissues in full thickness (I x I mm2, 5 pieces) from the left uterine horn were surgically autotransplanted to 5 different locations in the peritoneal cavity. One week later the animals were randomly assigned to four groups and treated with: vehicle alone (corn oil). 10.50 or 100 ng/kg/day TCDD for 28 days. Two days after last dose a necropsy was performed to measure the diameter of endometrial implants and to score the adhesions. Endometrial implants were harvested for histology and blood was collected for assessment of E2 levels. The diameter of endometrial implants was significantly smaller in the TCDD treated groups compared to the controls (p < 0.05). Survival of endometrial implants, the formation and scores of adhesions, and serum E2 levels were not significantly different among the dosing groups. Histology of implants showed a significant regression of endometrial tissues in the animals receiving 50 and 100 ng/kg/day TCDD compared to the controls. We conclude that continuous exposure to TCDD resulted in regression of the endometriotic implants in the ovariectomized mice treated with a high dose exogenous F2.

The effect of endometriosis on implantation: results from the Yale University in vitro fertilization and embryo transfer program

OBJECTIVE

To investigate the effect of endometriosis on implantation.

DESIGN

Case-control study from Yale University IVF-ET program.

PATIENTS

Two hundred eighty-four consecutive IVF cycles were analyzed retrospectively. Patients with endometriosis only (n = 35; 89 cycles) were compared with an age-matched control group with tubal infertility (n = 70; 147 cycles) and also to a group with unexplained infertility (n = 15; 48 cycles). Data from the endometriosis group was analyzed further in subgroups of minimal-mild (43 cycles) and moderate-severe (46 cycles).

RESULTS

No difference was found in the number and the quality of oocytes retrieved and fertilization rates between the endometriosis, the tubal infertility, and the unexplained infertility groups. The quality and the number of embryos transferred in each group were comparable. A trend toward reduced pregnancy rate per transfer (14.8%) in the endometriosis versus tubal or unexplained infertility groups (25.7% and 23.3%, respectively) was observed. Implantation rate (gestational sac per transferred embryo) was significantly lower in the endometriosis versus the tubal infertility group (3.9% versus 8.1%; unexplained infertility group, 7.2%). Analysis of first cycles only across all groups revealed that the implantation rate also was significantly lower in the endometriosis versus the tubal infertility group (3.1% versus 9%; unexplained infertility group, 6.7%). Within the endometriosis group, although the pregnancy rate per cycle and per transfer were similar in subgroups, patients with minimal-mild endometriosis had the lowest implantation rate.

CONCLUSION

We conclude that, in patients with endometriosis, implantation rate is low. Abnormal implantation, which may be secondary to endometrial dysfunction or embryotoxic environment, is a factor in endometriosis-associated subfertility.

Receptor concentrations for estradiol and progesterone in surgically induced endometriosis in the rat

In order to obtain more detailed information about the validity of the rat as an endometriotic experimental model, endometriosis was surgically induced in 48 female Wistar rats, and the estrogen (ERc) and progesterone (PRc) receptor concentrations present in experimental endometriosis and endometrium were compared in the four estrous phases (n = 12). Lower values of ERc were found in endometriosis than in endometrium (proestrus, 156.27 +/- 24.09 vs. 195.27 +/- 32.13 pmol/g tissue, P < 0.05; estrus, 302.33 +/- 45.16 vs. 335.67 +/- 44.82 pmol/g tissue, P < 0.05; metestrus, 166.60 +/- 26.09 vs. 193.30 +/- 22.04 pmol/g tissue, P < 0.05; diestrus, 130.27 +/- 20.58 vs. 135.81 +/- 16.25 pmol/g tissue, P > 0.05; Student's t-test). As in the case of ERc, lower PRc were observed in endometriotic than in endometrial tissues (proestrus, (proestrus, 137.83 +/- 22.64 vs. 176.54 +/- 21.78 pmol/g tissue, P < 0.05; estrus, 242.10 +/- 34.78 vs. 286.20 +/- 31.74 pmol/g tissue, P < 0.05; metestrus, 194.36 +/- 35.08 vs. 224.73 +/- 20.21 pmol/g tissue, P < 0.05; diestrus, 147.72 +/- 26.21 vs. 147.33 +/- 22.65 pmol/g tissue, P > 0.05; Student's t-test). Similar ERc/PRc ratios were found for both the endometriotic and the endometrial tissues (proestrus, 1.14 +/- 0.07 vs. 1.08 +/- 0.09, P > 0.05; estrus, 1.29 +/- 0.19 vs. 1.21 +/- 0.18, P > 0.05; metestrus, 0.87 +/- 0.14 vs. 0.89 +/- 0.11 P > 0.05; diestrus, diestrus, 0.89 +/- 0.06 vs. 0.92 +/- 0.06, P > 0.05; Student's t-test, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Nonsteroidal antiinflammatory drugs and reproduction

The role of nonsteroidal antiinflammatory drugs in human reproduction and reproductive disorders is reviewed. Nonsteroidal antiinflammatory drugs inhibit the biosynthesis of prostanoids and can cross the placental barrier into the fetal circulation. Nonsteroidal antiinflammatory drugs are the treatment of choice in primary dysmenorrhea and intrauterine contraceptive device-induced dysmenorrhea and menorrhagia. Nonsteroidal antiinflammatory drugs can be used for effective control of menorrhagia, preterm labor, and polyhydramnios and for prevention of preeclampsia, but larger definitive clinical trials are needed. Prostaglandin inhibition with some nonsteroidal antiinflammatory drugs appear promising in the relief of some premenstrual symptoms and in the prevention of postoperative pelvic adhesion formation, but more studies are needed in women. Whereas implantation and tubal mobility are mediated by local prostaglandins, the potential use of nonsteroidal antiinflammatory drugs to suppress prostaglandin in these reproductive processes for enhancing or reducing fertility warrants further studies. In the last 2 decades nonsteroidal antiinflammatory drugs have been used increasingly in the treatment of some reproductive disorders and are promising for many others.

Time-related effects of RU486 treatment in experimentally induced endometriosis in the rat

OBJECTIVE

To evaluate the time-dependent effect of the progesterone antagonist RU486 on experimentally induced endometriosis in the rat.

DESIGN

Endometriosis was induced by implanting endometrium onto the peritoneal side wall. Size of the implants was measured before and after treatment.

PARTICIPANTS

Fifty-two adult female Sprague-Dawley female rats weighing 200 to 225 g.

SETTING

Departmental research laboratory of university hospital.

INTERVENTION

Animals treated with RU486 or vehicle only for 2, 4, 6, or 8 weeks.

MAIN OUTCOME MEASURES

Size of the implant was measured before and after treatment; relative change in size of the implants was calculated.

RESULTS

There was not a statistically significant difference between the treatment groups and the control groups. There was no regression of endometriosis in any of the treatment groups.

CONCLUSIONS

RU486 administered for 8 weeks in the rat model was not effective therapy for endometriosis.

Experimentally induced endometriosis in rats: effect on fertility and the effects of pregnancy and lactation on the ectopic endometrial tissue

OBJECTIVE

To investigate the repercussion of experimentally induced endometriosis on the fertility of Wistar rats and the effects of pregnancy and lactation on endometrial ectopic implants.

DESIGN

Eight-five animals were used for the experiment. Experimental endometriosis was induced in 44 and the remaining 41 were sham-operated (control group). After evaluating the growth of the implants in a second laparotomy, all the animals were mated until finding sperm in vaginal smears. In third and fourth laparotomies during pregnancy and lactation, pregnancy rate was determined, and the implants were re-evaluated, being resected for histological study. Serum estradiol (E2) and progesterone (P) levels were also measured.

RESULTS

The pregnancy rate in animals with endometriosis was 65.7% versus 100% in control group. No statistical differences in days of gestation and number of pups were found between the two groups. Ectopic implants underwent a significant regression during lactation period. Serum E2 and P levels and histological features sustained these findings.

CONCLUSION

Experimentally induced endometriosis diminishes pregnancy rate in rats. It is not pregnancy, but the anestrus condition created by lactation that exerts a beneficial effect on experimentally induced endometriosis in rats.