An ovum capture inhibitor (OCI) in endometriosis peritoneal fluid: an OCI-related membrane responsible for fimbrial failure of ovum capture

Exploring Epithelial-Mesenchymal Transition Signals in Endometriosis Diagnosis and In Vitro Fertilization Outcomes

Endometriosis (EMS) pathogenesis has been related to the release of inflammatory mediators in peritoneal fluid, creating an altered microenvironment that leads to low-grade oocyte/embryos and to the reduction of implantation rates. The Epithelial–Mesenchymal Transition (EMT), an inflammation-related process, can be a further contributing factor to EMS. This study aimed to investigate, among various cytokines and EMT markers (Cadherins, TGF-β, HIF-1α), diagnostic markers of EMS and prognostic factors of in vitro fertilization (IVF) outcomes. Herein, EMS patients manifested higher serum levels of the inflammatory molecules IL-6, IL-8, and IL-12 and a decrease in the concentrations of the anti-inflammatory IL-10. Moreover, biochemical markers associated with the EMT process were more elevated in serum and follicular fluid (FF) of EMS patients than in controls. At the end, the number of good-quality embryos was inversely related to serum IL-6 and EMT markers. Interestingly, serum IL-6 and FF IL-10 concentrations differentiated EMS patients from controls. Finally, serum IL-8 and E-Cadherin levels, as well as FF IL-10, predicted positive IVF outcome with great accuracy. Our data confirm the pivotal role of inflammatory mediators (i.e., IL-6 and IL-10) in EMS pathogenesis and suggest that EMT-related markers are elevated in EMS patients and can be predictive of IVF outcome.

Fallopian tube subtle pathology

The aim of the present review is to give a comprehensive overview of fallopian subtle lesions and suggest the impacts of these abnormalities on fertility. Tubal subtle variations, including tubal diverticula, Morgagni hydatids, accessory fallopian tube, accessory ostium of the fallopian tube, tubal phimosis, agglutination, and sacculation, have been described and cited as making significant contributions to infertility. This review summarizes characteristics of these subtle abnormalities and provides an update of recent knowledge of the diagnosis and management of these variations. We hope that the present contribution may help to bring more attention to the clinical field to recognize these abnormalities and consequently aid in improving fertility.

Comparison of the symptoms and localisation of endometriosis involvement according to fertility status of endometriosis patients

This cross-sectional study aimed to assess the prevalence of endometriosis in women who were referred for Diagnostic Laparoscopy Unit due to infertility or pelvic pain between January 2012 and January 2013 and compare the symptoms and laparoscopic signs among the three groups according to the fertility status. Four hundred and thirteen women were evaluated; of these, 383 patients for infertility and 30 patients for pelvic pain and/or cyst. Endometriosis symptoms were compared between fertile and infertile women with primary and secondary infertility. There was no statistically significant difference in the overall prevalence of endometriosis between the three study groups (52.9%, 45% and 40.7%, respectively, in primary, secondary infertile and fertile women). The endometriosis stage was categorised as early- (I and II) or late- (III and IV) stages and the extent of endometriosis was divided into peritoneal, ovarian and ovarian coexisting with peritoneal. There is no relationship between the frequency of dysmenorrhoea or non-cyclic pelvic pain and the disease stage; although these pain symptoms are significantly more prevalent in cases with both ovarian and peritoneal endometriotic implants. Infertility was more prevalent among the patients with peritoneal endometriosis in comparison to the ones with ovarian endometriosis. Further studies with a larger sample size are required to confirm these findings. Impact statement What is already known on this subject? Few studies have been done in this area and only one study compared the localisation of endometriosis lesions between fertile and infertile endometriosis cases; however, more study is needed to confirm their results. What the results of this study add? A possible relationship between localisation of endometriosis involvement and infertility was found in the present study in agreement to result of a previous study performance in this area. Although the present study includes a greater number of cases than that of the previous reported study, further studies with a larger sample size are required for the confirmation or refusal of this finding. What are the implications of these findings for clinical practice and/or further research? The results of this study could have clinical application in the consultation and decision-making in infertile women with an endometriosis diagnosis.

Pelvic endometriosis with peritoneal fluid reduces pregnancy rates in women undergoing intrauterine insemination

OBJECTIVE

This study investigated the occurrence of peritoneal fluid in women undergoing intrauterine insemination (IUI) and its correlation with the stage of pelvic endometriosis and its influence on pregnancy outcomes.

MATERIALS AND METHODS

A retrospective case-control design was used to recruit 272 infertile women with pelvic endometriosis. The treatment protocol consisted of controlled ovarian hyperstimulation with downregulation and gonadotropin for IUI treatment following ultrasound and laparoscopic intervention. The amount and color of the peritoneal fluid were determined during laparoscopy.

RESULTS

The mean amount of peritoneal fluid with pelvic endometriosis that was detected using transvaginal ultrasound was ~ 15.1 mL. Women whose cycles contained more peritoneal fluid had significantly lower pregnancy rates (17.2% and 31.3%, respectively). The total clinical pregnancy rate was not significantly different between the two groups with reddish and yellowish peritoneal fluid who had pelvic endometriosis.

CONCLUSION

Pelvic endometriosis and peritoneal fluid, detected through vaginal ultrasound, have negative effects on the pregnancy outcome of IUI treatment.

Endometriosis and infertility

Endometriosis is a debilitating condition characterized by high recurrence rates. The etiology and pathogenesis remain unclear. Typically, endometriosis causes pain and infertility, although 20-25% of patients are asymptomatic. The principal aims of therapy include relief of symptoms, resolution of existing endometriotic implants, and prevention of new foci of ectopic endometrial tissue. Current therapeutic approaches are far from being curative; they focus on managing the clinical symptoms of the disease rather than fighting the disease. Specific combinations of medical, surgical, and psychological treatments can ameliorate the quality of life of women with endometriosis. The benefits of these treatments have not been entirely demonstrated, particularly in terms of expectations that women hold for their own lives. Although theoretically advantageous, there is no evidence that a combination medical-surgical treatment significantly enhances fertility, and it may unnecessarily delay further fertility therapy. Randomized controlled trials are required to demonstrate the efficacy of different treatments.

Pyruvate reduces in vitro the embryotoxic effect of peritoneal fluid from infertile women with endometriosis

OBJECTIVES

To ascertain the embryotoxicity of peritoneal fluid from infertile women with endometriosis (PF-E), on mouse embryos in culture and to examine the effect of pyruvate in the culture medium on PF-E induced embryotoxicity.

STUDY DESIGN

Blood-free peritoneal fluid samples were obtained during laparoscopic investigation for infertility from 21 infertile women with endometriosis. The severity of endometriosis ranged from minimal or mild (PF-min to mild-E; n=7), moderate (PF-mod-E; n=7), to severe (PF-sev-E; n=7). Peritoneal fluid samples were centrifuged at 600 x g for 10 min and 4 degrees C, and the supernatant was incubated at 56 degrees C for 30 min in a water bath to inactivate the complement protein. Mice were super ovulated with intraperitoneal injection (IP) of 5IU of pregnant mare serum gonadotrophin and human chorion gonadotrophin. Twenty-four hours after confirmation of mating two-cell mouse embryos were obtained. They were then cultured in modified Whitten's medium (mWM) with peritoneal fluid from patients with endometriosis, and either in the absence or presence of excess pyruvate (0.062 mmol(-1)). Embryos were cultured for 72 h.

RESULTS AND CONCLUSION

Addition of 5% PF-E significantly (p<0.001) suppressed embryo growth at 24, 48, and 72 h of culture and the degree of suppression correlated with the severity of the disease. The presence of 0.062 mmol(-1) pyruvate in the culture medium significantly (p<0.001) reduced the embryotoxicity of PF-min to mild-E and PF-mod-E at each stage of development, but was only seen at 24h of culture (p<0.001) in cultures with PF-sev-E even when the concentration of pyruvate in the medium was increased to 0.31 mmol(-1). This study confirms the embryotoxicity of PF-E in vitro, which was reduced by the presence pyruvate in the culture medium, particularly in cultures containing fluid from women with endometriosis of minimum or mild to moderate severity.

Paracrine regulation of endometriotic tissue

Endometriosis is a chronic estrogen-dependent gynecological disease, characterized by pelvic pain and infertility, defined as the presence of endometrial glands and stroma within the pelvic peritoneum and other extrauterine sites. In the peritoneal cavity endometrial cells adhere, proliferate and induce an inflammatory response. Despite a long history of clinical and experimental research, the pathogenesis of endometriosis is still controversial. Abnormal immunological activation, the endocrine milieu and the peritoneal environment all dramatically affect endometriotic tissue function. Recent studies suggest that the peritoneal fluid of women with endometriosis contains an increased number of activated macrophages and other immune cells that secrete various local products, such as growth factors and cytokines, which exert a paracrine action on endometriotic cells. Since the peculiar biological characteristics of eutopic endometrium from women with endometriosis differ from endometrium of normal subjects, an important role in the pathogenesis of this complex disease has been suggested. All of these factors contribute to enhanced proliferative and angiogenic activity and a number of functional and structural changes, resulting in the particular behavior of this tissue.

Endometriosis and infertility

Women with endometriosis typically present with pelvic pain, infertility or an adnexal mass. Surgery for persistent adnexal masses may be indicated to remove an endometrioma or other pelvic pathology. Surgical or medical therapy is efficacious for pelvic pain due to endometriosis, but treatment of endometriosis in the female partner of an infertile couple raises a number of complex clinical questions that do not have simple answers.

The prevalence of fimbrial pathology in patients with early stages of endometriosis

STUDY OBJECTIVE

The presence of fimbrial pathology in advanced endometriosis is clearly understood. However, little is known about the prevalence of fimbrial pathology in early stages of endometriosis. The purpose of this study is to determine the prevalence of fimbrial pathology in patients with infertility with early stages of endometriosis.

DESIGN

Historical cohort study (Canadian Task Force classification II/III).

SETTING

Tertiary referral center.

PATIENTS

The study group (Group 1) consisted of 315 infertile women who were found to have stage I or stage II endometriosis, and the control group (Group 2) consisted of 152 infertile women without endometriosis (Group 2).

INTERVENTION

Laparoscopic evaluation for the presence and type of fimbrial pathology.

MEASUREMENTS AND MAIN RESULTS

The prevalence of fimbrial pathology was significantly higher in infertile patients with early stages of endometriosis (50.2%) compared with infertile patients with no endometriosis (17.8%, p <.0001).

CONCLUSION

These preliminary data suggest the presence of fimbrial pathology in many patients with early stages of endometriosis. Such pathology may act as a mechanical factor interfering with the ovum pick-up mechanism.

The reproductive significance of human Fallopian tube cilia

Effective tubal transport of ova, sperm and embryos is a prerequisite for successful spontaneous pregnancy. Although there is much yet to be discovered about the mechanisms involved, it is evident that tubal transit is a far more complicated process than initially thought. Propulsion of gametes and embryos is achieved by complex interaction between muscle contractions, ciliary activity and the flow of tubal secretions. Evidence is accumulating of the important and possibly pre-eminent role of ciliary motion in this process; and this review describes current knowledge about ciliary activity and its physiological regulation. There is also a description of the effects on ciliary function of cigarette smoking and various pathological states, including endometriosis and microbial infection, with consideration given as to how altered ciliary activity may impact upon fertility.

Smoking and reproduction: the oviduct as a target of cigarette smoke

The oviduct is an exquisitely designed organ that functions in picking-up ovulated oocytes, transporting gametes in opposite directions to the site of fertilization, providing a suitable environment for fertilization and early development, and transporting preimplantation embryos to the uterus. A variety of biological processes can be studied in oviducts making them an excellent model for toxicological studies. This review considers the role of the oviduct in oocyte pick-up and embryo transport and the evidence that chemicals in both mainstream and sidestream cigarette smoke impair these oviductal functions. Epidemiological data have repeatedly shown that women who smoke are at increased risk for a variety of reproductive problems, including ectopic pregnancy, delay to conception, and infertility. In vivo and in vitro studies indicate the oviduct is targeted by smoke components in a manner that could explain some of the epidemiological data. Comparisons between the toxicity of smoke from different types of cigarettes, including harm reduction cigarettes, are discussed, and the chemicals in smoke that impair oviductal functioning are reviewed.

Endometriosis and infertility

Women with endometriosis typically present with pelvic pain, infertility or an adnexal mass. Surgery for persistent adnexal masses may be indicated to remove an endometrioma or other pelvic pathology. Surgical or medical therapy is efficacious for pelvic pain due to endometriosis, but treatment of endometriosis in the female partner of an infertile couple raises a number of complex clinical questions that do not have simple answers.

Endometriosis and infertility

Women with endometriosis typically present with pelvic pain, infertility or an adnexal mass. Surgery for persistent adnexal masses may be indicated to remove an endometrioma or other pelvic pathology. Surgical or medical therapy is efficacious for pelvic pain due to endometriosis, but treatment of endometriosis in the female partner of an infertile couple raises a number of complex clinical questions that do not have simple answers.

Peritoneal fluid, endometriosis, and ciliary beat frequency in the human fallopian tube

Endometriosis and infertility are known to be associated, but it is unclear whether endometriosis causes infertility. We used contrast analogue enhancement to study the effect of peritoneal fluid from women with early stage endometriosis on the ciliary beat frequency of human fallopian tube epithelium. We obtained peritoneal fluid from six women with early stage endometriosis and from six fertile women with no evidence of endometriosis to use as controls. Fallopian tubes from hysterectomy specimens were collected from 17 women. The difference in ciliary beat frequency between fallopian tubes exposed to peritoneal fluids of women with and without endometriosis increased with the duration of incubation (mean difference at 24 h 1.35 Hz, 95% CI 0.94-1.75, p=0.01). At 24 h, ciliary beat frequency was significantly lower in the incubations with peritoneal fluid from women with endometriosis than controls (4.29 [0.15] vs 5.64 Hz [0.15], respectively, p=0.001). Impairment of ciliary action in women with endometriosis might reduce fertility.

Role of cytokines in endometriosis

OBJECTIVE

To review the literature on the role of cytokines in the pathogenesis of endometriosis and endometriosis-associated infertility.

DESIGN

Pertinent studies were identified by a computer search of MEDLINE. References of selected articles were hand-searched for additional citations.

RESULT(S)

Recent studies suggest that the peritoneal fluid of women with endometriosis contains an increased number of activated macrophages that secrete various local products, such as growth factors and cytokines. Levels of several cytokines were reported to be elevated in the peritoneal fluid of women with endometriosis. Because the peritoneal environment may be controlled by locally regulated factors, cytokines are believed to play a role in the development and progression of endometriosis and endometriosis-associated infertility. A possible pathogenic mechanism links cytokines with endometriosis.

CONCLUSION(S)

Cytokines, which are produced by many cell types including endometriotic tissues, play diverse roles in the pathogenesis of endometriosis and endometriosis-associated infertility. More studies about the specific role of these cells and soluble factors are needed to improve understanding of endometriosis and to develop novel therapies.

Laparoscopic surgery for endometriosis: a long-term follow-up

OBJECTIVE

To investigate if complete resolution of endometriosis by laparoscopic surgery is beneficial to postoperative fecundity, dysmenorrhea and dyspareunia.

DESIGN

An observational comparative study on the outcome of laparoscopic surgery.

PATIENTS

Laparoscopically-treated symptomatic women with endometriosis (total n = 236); complete (n = 185) and incomplete (n = 51) surgery groups.

MEASUREMENTS

Postoperative fecundity and symptom reduction.

RESULTS

With whole populations, no surgical completeness-related difference was observed in cumulative pregnancy rates during the postoperative days 0-400 (cycle fecundity rate = 0.0319). Further accumulation of pregnant cases was followed in the complete surgery group (final cumulative pregnancy rate = 80%), but not in the counterpart group (p = 0.003). The similar result was obtained when only r-AFS classification stages III and IV were compared (p = 0.007). No r-AFS stage-related difference was observed in cumulative pregnancy rates when only patients of complete surgery were selected for comparison. The surgery reduced dysmenorrhea (84.7%) and dyspareunia (80.0%).

CONCLUSIONS

Laparoscopic conservative surgery for endometriosis, especially when it is complete, increases fecundity and reduces disease-related symptoms, such as dysmenorrhea and dyspareunia.

Cigarette smoke inhibits oocyte cumulus complex pick-up by the oviduct in vitro independent of ciliary beat frequency

The purpose of this study was to quantify the effects of acute exposure to mainstream (MS) and sidestream (SS) smoke solutions on oocyte cumulus complex pick-up rate in explants of hamster oviducts using a newly developed in vitro assay. Experiments were performed in handmade perfusion chambers using infundibula from hamster oviducts and oocyte cumulus complexes harvested from mature ovarian follicles. Oocyte cumulus complex pick-up rate was measured by placing a stained oocyte cumulus complex at the base of the infundibulum and recording the length of time needed for the complex to traverse a defined path to the ostium. Addition of either whole MS or SS smoke solutions to the perfusion chamber caused a dose dependent decrease in oocyte cumulus complex pick-up rate. Unexpectedly, upon washout of smoke solutions with control medium, oocyte cumulus complex pick-up rate continued to decline. The gas phase of MS smoke is more inhibitory than the particulate phase, while SS gas and particulate phases inhibit oocyte cumulus complex pick-up rate at equivalent doses. Ciliary beat frequency and oocyte cumulus complex pick-up rate were measured using the same infundibular explants to determine if smoke solutions decrease oocyte cumulus complex pick-up rate by inhibiting ciliary beat frequency. Ciliary beat frequency decreased in MS smoke solutions and recovered either partially or completely after washout of the smoke solutions. SS smoke solutions either produced no change in ciliary beat frequency or stimulated ciliary beat frequency. Oocyte cumulus complex pick-up rate decreased in both MS and SS smoke solutions and further declined during washout when ciliary beat frequency was equivalent to or higher than controls. These data show that oocyte cumulus complex pick-up rate and ciliary beat frequency can be uncoupled and that smoke solutions inhibit oocyte cumulus complex pick-up rate by affecting factors in addition to ciliary beat frequency. Possible reasons for the smoke induced decrease in oocyte cumulus complex pick-up rate are discussed. These results may explain the increased incidence of tubal infertility and ectopic pregnancy observed in women who smoke.

In vitro analysis of oocyte cumulus complex pickup rate in the hamster Mesocricetus auratus

In mammals, the oocyte and its surrounding cumulus cells constitute on oocyte cumulus complex (OCC). During ovulation, OCCs are extruded into the peritoneal or bursal cavity, depending on the species, and are then rapidly picked up by the fimbria on the outer surface of the oviductal infundibulum and transported to the ampulla, where fertilization occurs. We developed a method to measure OCC pickup rates quantitatively in vitro, and we used this method to evaluate the effects of viscosity and temperature on pickup rates. Hamster infundibula are placed in a holding pipette in a chamber modified to study OCC pickup. Ciliary beat frequencies (CBF) can be measured in the same preparation. Pickup rates vary depending on the pathway on which the OCC travels over the surface of the infundibulum; however, rates for a given pathway are very consistent. The average pickup rate at room temperature calculated from three different pathways/infundibulum was 55.2 +/- 10.6 microns/sec. Both rates between infundibula from the same female and rates among infundibula from different females were in most cases similar. Preparations preincubated in vitro for 2.75 hr produced rates similar to nonpreincubated samples, while longer preincubation resulted in decreased rates. Inclusion of Ficoll in culture medium to increase viscosity caused a concentration-dependent decrease in both OCC pickup rate and in CBF. However, a significant decrease in OCC pickup rate was only observed at viscosities higher than those found in bursal fluid. When trials were run at physiological temperature (36.4 degrees C) rather ambient temperature, rates increased to 136.7 +/- 29.9 (SD) microns/sec. Linear regression analysis demonstrated a strong positive correlation (r = 0.94) between OCC pickup rate and temperature. The OCC pickup rate assay can be used experimentally, and should be valuable in evaluating factors that affect rate and in studies dealing with the mechanism of OCC pickup.

Basic research in endometriosis

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

Chemotaxis of macrophages by a peritoneal fluid protein in women with endometriosis

OBJECTIVE

To expand on a preliminary study comparing the chemotactic potential of peritoneal fluid (PF) from women with and without endometriosis and to characterize this activity via immunosuppressants and a protease.

DESIGN

Case control study.

SETTING

University center.

PATIENT(S)

Fifty-nine women with endometriosis and 44 without, undergoing laparoscopy.

INTERVENTION(S)

Collection of PF, endometriotic, ovarian, and endometrial biopsies at laparoscopy.

MAIN OUTCOME MEASURE(S)

Chemotactic activity of PF was tested via an in vitro assay alone and in the presence of immunosuppressants cyclosporin A (CSA), FK506, rapamycin, and type XVII-b(S-V8) protease and in media incubated with endometriotic, ovarian, or endometrial biopsy specimens.

RESULT(S)

The PF from women with endometriosis had significantly greater chemotactic activity (cells per well, mean +/- SD) than without endometriosis (142 +/- 39 versus 48 +/- 17). Cyclosporin A significantly inhibited the chemotactic activity of the endometriotic PF; FK506 and rapamycin did not. Incubation of media with endometriotic tissue, but not ovarian or endometrial, for > or = 7 hours displayed chemotactic activity. Protease type XVII-b(S-V8) added to endometriotic PF inhibited this chemotactic activity.

CONCLUSION(S)

Peritoneal fluid from patients with endometriosis contains a protein chemotactic factor attracting inflammatory cells into the peritoneal cavity, possibly secreted by endometriotic implants. This chemotactic factor may be a member of the immunophilin family because of its inhibition profile.

Endometrial leukocyte subpopulations in women with endometriosis

The aim of this study was to investigate whether the endometrium of women with endometriosis differs immunologically from the endometrium of normal fertile women. Endometrial biopsies were obtained from 18 normal fertile women who were requesting sterilisation or reversal of sterilisation and 21 infertile women who had laparoscopically diagnosed pelvic endometriosis. The endometrial biopsies were obtained from both groups during the either early, mid or late luteal phase of the menstrual cycle. A panel of 11 monoclonal antibodies and immuno-histochemical techniques were employed to characterise the endometrial stromal leukocytes in frozen sections. Image analysis was used for semi quantitation of leukocytes. In both groups, the number of endometrial granulated lymphocytes (CD56+ CD38+ cells) and macrophages (CD68+ cells) increased significantly between the early and late luteal phase of the menstrual cycle. Compared with fertile controls, women with endometriosis had fewer T-suppressor/cytotoxic (CD8+) cells and endometrial granulated lymphocytes but more T-helper/inducer (CD4+) cells, CD68+ cells and CD16+ cells. None of these differences reached a statistically significant level. This study has shown that the endometrial lymphoid tissue of women with endometriosis does not differ qualitatively or quantitively from that of normal fertile controls. However, functional differences of endometrial leukocytes between the two groups cannot be excluded.

Endometriosis: the host response

There is abundant evidence of altered immune function in endometriosis. The task that remains is to attempt a synthesis from the accumulated data, to try to make some sense of the observed phenomena and to fit them into a conceptual framework; this might permit the formulation and testing of hypotheses. Evidently, eutopic endometrium does not engender an immune response in normal subjects, otherwise the endometrium would be subject to autoimmune destruction. It has also been established that the overwhelming majority of women regurgitate menstrual debris into the peritoneal cavity. Why does this lead to endometriosis in some, but not in others? There are several possible explanations. The uterus might act as a privileged site, i.e. be exempt from immune effector mechanisms. This would certainly be conducive to the reproductive goal, the survival of the fetal allograft. Endometrium would then not enjoy the immunologic tolerance of most other tissues, and upon leaving the uterus and entering an immunocompetent environment would be subject to immune attack. In normal subjects, this could consist of elimination of menstrual debris without further sequelae. An altered response, characterized by the production of antibody that could mask receptors for cytotoxic or phagocytic effector cells, would permit persistence of ectopic endometrium. The alternative to this hypothesis is that the uterus is not a privileged site, and that the organism is normally tolerant to endometrial antigens. Menstrual debris would be eliminated intraperitoneally without loss of tolerance due to the presence of homeostatic mechanisms including suppressor T cells and suppressive cytokines. In endometriosis, this tolerance breaks down, as is the case in several autoimmune disorders, causing a chronic inflammatory response with the release of toxic factors and, eventually, peritoneal scarring. Finally, the role of cell adhesion molecules, including the integrins, is only just being explored. The behaviour of these molecules in ectopic endometrium differs from that in eutopic endometrium, and it remains to be seen whether regurgitated endometrial debris from normal subjects is different from that of endometriosis sufferers. It seems that this will be an area of intense investigation in the immediate future.

Menstruation as the pelvic aggressor

Cumulative evidence supports the concept of retrograde menstruation being a pelvic aggressor as it contributes to both the development of endometriosis and related symptoms such as dysmenorrhoea and infertility. A major problem in studying the association between these entities (retrograde menstruation, endometriosis, dysmenorrhoea and infertility) is the lack of an accurate method to quantify the amount of retrograde menstruation.

Endometriosis-associated infertility

Despite intense clinical interest and increasingly sophisticated diagnostic techniques, we know surprisingly little of the relationship between endometriosis and infertility or the mechanism of infertility in these couples. No therapy specifically directed toward the ectopic endometrial implants, medical or surgical, has been demonstrated to improve the likelihood of pregnancy for couples with endometriosis-associated infertility. This is consistent with the observation that, in the absence of mechanical distortion of the pelvic viscera, no therapy directed against the implants improves the likelihood of pregnancy in these couples. The reason for this lack of progress is most probably that the mechanism of infertility in these couples remains to be determined. At present, it would be more accurate to say that these couples have unexplained infertility. The most promising therapeutic approach is to treat women with endometriosis-associated infertility with a non-specific cycle fecundity enhancing technique. Typically this is one of the newer assisted reproductive technologies such as controlled ovarian hyperstimulation with intrauterine insemination of capacitated sperm. Since the fecundity of many of the women with endometriosis in the later reproductive years is rapidly declining, this may represent their most cost-effective option for establishing a pregnancy. Only with further effort directed towards determining the mechanisms of infertility in these couples will a more effective therapy be forthcoming.

Role of peritoneal inflammation in endometriosis-associated infertility

This paper has discussed the evidence for the presence of infertility in patients with endometriosis and more critically reviewed some of the studies that have addressed the impact of various potential local peritoneal mechanisms that may lead to subfertility. Substantial evidence supports the notion that patients with endometriosis have reduced fecundability. Although several mechanisms, including, e.g., anatomic factors and ovulatory dysfunction, are possible, recent studies have pointed towards local inflammatory cells and their secretory products as being important mediators of subfertility. Ample evidence exists for the presence of an altered peritoneal inflammatory environment in patients with endometriosis. In addition, in vitro studies have identified peritoneal macrophages and their secretory products, specifically TNF-alpha as the most likely contributors to the reduced fecundability through effects on sperm function.

Endometriosis and infertility

The relationship of endometriosis, the most common benign gynaecological disease during reproductive life, to infertility is generally ill understood. The association between infertility and minimal to mild endometriosis, when no anatomical defect is evident, may be explained by the following possible mechanisms: alternations in peritoneal fluid (macrophages - immunoglobulins, Interleukin-1, protease inhibitors, prostanoids, an ovum capture inhibitor), ovulatory dysfunctions (anovulation, LUF syndrome), luteal phase defect, disturbed implantation, and spontaneous abortion. These possibilities are discussed. The latest prospective controlled studies offer strong evidence that endometriosis per se is not a direct cause of infertility. On the other hand, the disease usually deteriorates if not treated, and therefore medical or surgical interventions are often needed when expectant treatment or other infertility therapies, e.g., ovulation induction, fail to result in pregnancy. Women with minimal to mild endometriosis only should be diagnosed as having unexplained infertility, which today may be treated by in vitro fertilization.