Vasculogenesis: a new piece of the endometriosis puzzle

Performance of Circulating Placental Growth Factor as A Screening Marker for Diagnosis of Ovarian Endometriosis: A Pilot Study

Background

The aim of this study is to compare the circulating placental growth factor (PlGF) concentration in women with and without endometrioma to verify the performance of this marker to diagnose the disease.

Materials and Methods

In this case-control study, thirteen women with histological diagnosis of ovarian endometriosis were compared with women without endometriosis disease. PlGF plasma levels of endometriotic patients and controls were investigated using a fluorescence immunoassay technique.

Results

PlGF showed a direct correlation with body mass index (BMI) only in the control group (P=0.013). After adjustment for BMI values, PlGF median value in endometriosis group (14.7 pg/mL) resulted higher than in control group (13.8 pg/ mL, P=0.004).

Conclusion

PlGF is a promising peripheral blood marker that can discriminate between patients with and without ovarian endometriosis.

Endometriosis and cancer

Endometriosis is manifested by the presence of both endometrial glandular and stromal cells outside the uterine cavity. It is characterized by ectopic implantation of endometrial cells with elevated proliferation and migration. Endometriosis is the leading cause of morbidity among premenopausal women and the complex pathogenesis of this disease remains controversial despite extensive research. This rather complex disease has a significant impact on quality of life of many women as none of the current treatments represent a cure. Based on the current knowledge, one can conclude that the histological and genetic alterations in endometriosis might explain why and how endometriosis can change into several types of cancer. However, the exact mechanisms of this conversion are still not fully established.

MAP kinases and the inflammatory signaling cascade as targets for the treatment of endometriosis?

INTRODUCTION

The pathogenesis of endometriosis, a common benign disease, remains ill-defined, although it is clear that chronic inflammation plays a crucial role through mitogen-activated protein kinase (MAPK) signaling pathways. All current medical therapies for endometriosis are antigonadotropic, and therefore have a contraceptive effect. A concerted research effort is hence warranted with the aim of delivering novel therapeutics that reduces disease symptoms without blocking ovulation.

AREAS COVERED

The authors review the complex pathogenic mechanisms of chronic inflammation in endometriosis and their relationships with MAPK pathways. The authors conducted a literature search of descriptive and functional targeted validation of MAPK in the pathogenesis of endometriosis. The effects of MAPK inhibitors, which constitute potential agents for future treatments, are also described.

EXPERT OPINION

Preliminary studies have highlighted a crucial role for MAPK in driving endometriosis-related inflammation. MAPK inhibitors exhibit potent activity in terms of controlling growth of endometriosis lesions both in vitro and in animal models. As MAPK inhibitors are known to have a multitude of undesirable side effects, their use in humans has to be approached with great care. Indeed, use of these drugs would probably be limited to short exposures prior to surgery in cases involving the most severe disease phenotypes.

Endometriosis: a role for stem cells

Endometriosis is a complex gynecologic condition affecting 6-10% of reproductive aged women and is a major cause of chronic pain and infertility. Mechanisms of disease pathogenesis are poorly understood. Considerable evidence supports the existence of a stem cell population in the endometrium which provides a physiologic source of regenerative endometrial cells, and multiple lines of evidence now support a key role for stem cells in the pathogenesis of endometriosis. In addition, new blood vessel formation is critical for the establishment and maintenance of endometriotic implants, a process in which endothelial progenitor cells may play an integral role. These new insights into disease pathogenesis present exciting opportunities to develop targeted and more effective therapeutic options in the management of this common and challenging disease.

Endometriosis and ovarian cancer: potential benefits and harms of screening and risk-reducing surgery

Although endometriosis is well recognized as a benign gynecologic condition, its association with ovarian cancer (OVCA) has frequently been reported. Review articles on this topic are voluminous, yet there seems to be no consensus as to whether endometriosis is truly a precursor of OVCA and whether any screening or risk-reducing surgery should be instituted, on the basis of our current knowledge. In this review, published data are compiled and critically appraised. Through this critical appraisal, it seems clear that the strongest evidence seems to come from prevalence data. This type of data also suggests a reduced risk of certain histotypes (mainly type II) of OVCA in women with endometriosis. This may explain the rather moderate increase in risk as shown in epidemiologic studies. Even with this moderate increase in OVCA risk, caution should be exercised because of apparent bias in favor of publication of positive results, extensive heterogeneities among prevalence estimates, and inverse relationship between estimates and sizes of the studies. Many molecular studies are conflicting, and earlier studies showing molecular aberrations involved in genomic instability and mutation that enable malignant transformation are not replicated in later studies. Given the low incidence of OVCA and the rather moderate increase in risk of mostly type I tumors, screening seems to be ill-advised, and risk-reducing surgery such as salpingectomy with or without oophorectomy does not seem to yield any substantial benefit to women with endometriosis.

Inhibition of MAPK and VEGFR by Sorafenib Controls the Progression of Endometriosis

INTRODUCTION

Sorafenib is a strong multikinase inhibitor targeting 2 different pathways of endometriosis pathogenesis: RAF kinase and vascular endothelial growth factor receptor (VEGFR). We investigate whether Sorafenib could control the growth of endometriotic lesions both in vitro and in vivo.

METHODS

Stromal primary cells were extracted from endometrial and endometriotic biopsies from patients with (n = 10) and without (n = 10) endometriosis. Proliferation, apoptosis, mitogen-activated protein kinases, and VEGFR-2 autophosphorylation were explored with and without Sorafenib treatment. Human endometriotic lesions were implanted in 30 nude mice randomized according to Sorafenib or placebo treatment.

RESULTS

Treating endometriotic cells with Sorafenib abrogated the phosphorylation of extracellular signal-regulated kinase in stromal cells of women with endometriosis compared to controls. In addition, this study highlights the antiangiogenic role of Sorafenib which translates as a decreased phosphorylated VEGFR-2-VEGFR-2 ratio in endometriosis. Using a xenogenic mouse model of endometriosis, we confirmed that Sorafenib regulates the endometriosis activity in vivo by targeting endometriosis-related proliferation and inflammation.

CONCLUSION

Our data suggest that Sorafenib controls the growth of endometriotic lesions in vitro and in vivo.

Pathophysiology and Immune Dysfunction in Endometriosis

Endometriosis is an estrogen-dependent, chronic, proinflammatory disease prevalent in 10% of women of reproductive age worldwide. Characterized by the growth of endometrium-like tissue in aberrant locations outside of the uterus, it is responsible for symptoms including chronic pelvic pain, dysmenorrhea, and subfertility that degrade quality of life of women significantly. In Canada, direct and indirect economic cost of endometriosis amounts to 1.8 billion dollars, and this is elevated to 20 billion dollars in the United States. Despite decades of research, the etiology and pathophysiology of endometriosis still remain to be elucidated. This review aims to bring together the current understanding regarding the pathogenesis of endometriosis with specific focus on mechanisms behind vascularization of the lesions and the contribution of immune factors in facilitating lesion establishment and development. The role of hormones, immune cells, and cytokine signaling is highlighted, in addition to discussing the current pharmaceutical options available for management of pain symptoms in women with endometriosis.

Integrative Analysis Reveals Regulatory Programs in Endometriosis

Endometriosis is a common gynecological disease found in approximately 10% of reproductive-age women. Gene expression analysis has been performed to explore alterations in gene expression associated with endometriosis; however, the underlying transcription factors (TFs) governing such expression changes have not been investigated in a systematic way. In this study, we propose a method to integrate gene expression with TF binding data and protein-protein interactions to construct an integrated regulatory network (IRN) for endometriosis. The IRN has shown that the most regulated gene in endometriosis is RUNX1, which is targeted by 14 of 26 TFs also involved in endometriosis. Using 2 published cohorts, GSE7305 (Hover, n = 20) and GSE7307 (Roth, n = 36) from the Gene Expression Omnibus database, we identified a network of TFs, which bind to target genes that are differentially expressed in endometriosis. Enrichment analysis based on the hypergeometric distribution allowed us to predict the TFs involved in endometriosis (n = 40). This included known TFs such as androgen receptor (AR) and critical factors in the pathology of endometriosis, estrogen receptor α, and estrogen receptor β. We also identified several new ones from which we selected FOXA2 and TFAP2C, and their regulation was confirmed by quantitative real-time polymerase chain reaction and immunohistochemistry (IHC). Further, our analysis revealed that the function of AR and p53 in endometriosis is regulated by posttranscriptional changes and not by differential gene expression. Our integrative analysis provides new insights into the regulatory programs involved in endometriosis.

Soluble ligands for the NKG2D receptor are released during endometriosis and correlate with disease severity

BACKGROUND

Endometriosis is a benign gynaecological disease. Abundant bulk of evidence suggests that patients with endometriosis have an immunity dysfunction that enables ectopic endometrial cells to implant and proliferate. Previous studies show that natural killer cells have a pivotal role in the immune control of endometriosis.

METHODS AND FINDINGS

This is a prospective laboratory study conducted in a tertiary-care university hospital between January 2011 and April 2013. We investigated non-pregnant, younger than 42-year-old patients (n= 202) during surgery for benign gynaecological conditions. After complete surgical exploration of the abdominopelvic cavity, 121 women with histologically proven endometriosis and 81 endometriosis-free controls women were enrolled. Patients with endometriosis were classified according to a surgical classification in three different types of endometriosis: superficial peritoneal endometriosis (SUP), ovarian endometrioma (OMA) and deep infiltrating endometriosis (DIE). Peritoneal fluid samples were obtained from all study participants during the surgery in order to detect soluble NKG2D ligands (MICA, MICB and ULBP-2). When samples with undetectable peritoneal fluid levels of MICA, MICB and ULBP-2 were excluded, MICA ratio levels were significantly higher in endometriosis patients than in controls (median, 1.1 pg/mg; range, 0.1-143.5 versus median, 0.6 pg/mg; range, 0.1-3.5; p=0.003). In a similar manner peritoneal fluid MICB levels were also increased in endometriosis-affected patients compared with disease-free women (median, 4.6 pg/mg; range, 1.2-4702 versus median, 3.4 pg/mg; range, 0.7-20.1; p=0.001). According to the surgical classification, peritoneal fluid soluble MICA, MICB and ULBP-2 ratio levels were significantly increased in DIE as compared to controls (p=0.015, p=0.003 and p=0.045 respectively). MICA ratio levels also correlated with dysmenorrhea (r=0.232; p=0.029), total rAFS score (r=0.221; p=0.031) and adhesions rAFS score (r=0.221; p=0.031).

CONCLUSIONS

We demonstrate a significant increase of peritoneal fluid NKG2D ligands in women with endometriosis especially in those cases presenting DIE. This study suggests that NKG2D ligands shedding is a novel pathway in endometriosis complex pathogenesis that impairs NK cell function.

Medical treatment of ureteral obstruction associated with ovarian remnants and/or endometriosis: report of three cases and review of the literature

STUDY OBJECTIVE

Experience with low-dose intermittent danazol or prolonged gonadotropin-releasing hormone agonist (GnRH-a) with and without add-back therapy in endometriosis-associated ureteral obstruction.

DESIGN

Retrospective case series (Canadian Task Force classification II-2).

SETTING

University-affiliated teaching hospital.

PATIENTS

Three women with endometriosis-associated ureteral obstruction.

INTERVENTION

The regimen of GnRH-a alone or with add-back included (1) leuprolide acetate 3.75 mg intramuscularly monthly; (2) micronized 17α-estradiol 1 mg/day by mouth; (3) pulsed norethinedrone 0.35 mg/day by mouth, 2 days on and/or 2 days off; and (4) letrozole 2.5 mg by mouth for the first 5 days of the first GnRH-a injection. Danazol, 100 mg/day by mouth, was prescribed as a regimen of 3 months on, 3 months off, for 4 years.

MEASUREMENTS AND MAIN RESULTS

The first case was a 50-year-old woman, gravida 3, para 3, body mass index (BMI) 27 kg/m(2), with multiple surgeries, including hysterectomy and bilateral salpingo-oophorectomy (HBSO), and history of a stroke. She presented with right-sided pain and hydro-uretero-nephrosis. Magnetic resonance imaging identified a right adnexal cyst (4.5 × 3.4 × 2.4 cm). She was treated with leuprolide acetate monthly injections and a ureteric stent. The cyst, pain, and hydro-uretero-nephrosis resolved after 12 months. The second case was a 45-year-old woman, G2P2, BMI 28 kg/m(2) with multiple surgeries, including HBSO. She presented with left-sided pelvic pain. Ultrasound identified a left adnexal cyst and hydronephrosis. After 3 months of leuprolide acetate and add-back therapy, the cyst, pain, and hydronephrosis resolved. The third case was a 46-year-old woman, G2P2, BMI 25 kg/m(2), who presented with left flank and pelvic pain. Magnetic resonance imaging indicated moderate left hydronephrosis and left adnexal pelvic side-wall involvement with possible endometriosis. Due to many previous surgeries, this patient was a high-risk surgical candidate, and therefore, she was offered medical therapy. After a normal serum liver and lipid profile, she was started on danazol, 100 mg/day for 3 months. After 3 months of therapy, there was complete resolution of the patient's hydronephrosis and pain. She was then advised to continue with a 3-month on, 3-month off regimen. She discontinued the danazol and remained asymptomatic with no recurrence of hydronephrosis at 3 years.

CONCLUSIONS

Low-dose intermittent danazol or GnRH-a alone or with add-back, may be effective long-term therapies in endometriosis-associated ureteral obstruction when surgery is contraindicated, refused, or difficult to perform.

Regression of experimental endometriotic implants in a rat model with the angiotensin II receptor blocker losartan

AIM

Endometriosis is a common disease in women of reproductive age, and many different treatments have been developed, although none has provided a cure. In this study, the efficacy of losartan, an angiotensin II type 1 receptor blocker and an antiangiogenic and anti-inflammatory agent, on regression of experimental endometriotic implants in a rat model was investigated.

METHODS

Peritoneal endometriosis was surgically induced in 16 mature female Sprague-Dawley rats. The peritoneal endometriotic implant was confirmed after 28 days, and the animals were divided randomly into two groups. The control group (n = 8) was given 4 mL/day tap water by oral gavage, and the losartan group (n = 8) was given 20 mg/kg per day losartan p.o. We compared endometriotic implant size, extent and severity of adhesion, as well as plasma and peritoneal lavage fluid cytokine levels including vascular endothelial growth factor (VEGF) and tumor necrosis factor (TNF)-α, plasma inflammatory factor pentraxin-3 (PTX-3) and C-reactive protein (CRP) between the treatment groups.

RESULTS

Mean surface endometriotic area, histological score of implants, adhesion formation, plasma VEGF, TNF, PTX-3 and CRP levels were significantly lower in the losartan group compared with control (P < 0.05). Furthermore, the peritoneal VEGF level was lower in the losartan group than in the control group (P < 0.001), but peritoneal TNF-α was similar in both groups (P > 0.05).

CONCLUSION

Losartan suppressed the implant surface area of experimental endometriosis in rats and reduced the levels of plasma VEGF, TNF-α, PTX-3 and CRP.

Endometriosis: Survey of Current Diagnostic and Therapeutic Options and Latest Research Work

Endometriosis is one of the most frequent benign diseases in women of child-bearing age. The main symptoms are chronic upper abdominal pain and infertility. However, the aetiology and pathogenesis of endometriosis are as yet insufficiently clarified. Thus, therapy is mainly symptomatic with laparoscopic surgery being the gold standard. The aim of drug therapy is to achieve a hypo-oestrogenic condition. In cases of severe endometriosis and a desire to have children there is often an indication for assisted reproduction. The present article illustrates almost all current aspects on the diagnosis of and therapy of endometriosis. From the clinical viewpoint, emphasis is placed on the rare cases of deeply infiltrating endometriosis that are, however, accompanied with a high morbidity. Current therapeutic options in cases of infertility are also presented in more detail. Furthermore, special attention is paid to the latest research results from both clinical and basic research fields in order to demonstrate our current knowledge on the pathogenesis and, where possible, potentially related therapeutic options.

Role of pigment epithelium-derived factor in the reproductive system

The physiological function of the female reproductive organs is hormonally controlled. In each cycle, the reproductive organs undergo tissue modifications that are accompanied by formation and destruction of blood vessels. Proper angiogenesis requires an accurate balance between stimulatory and inhibitory signals, provided by pro- and anti-angiogenic factors. As with many other tissues, vascular endothelial growth factor (VEGF) appears to be one of the major pro-angiogenic factors in the female reproductive organs. Pigment epithelium-derived factor (PEDF) is a non-inhibitory member of the serine protease inhibitors (serpin) superfamily, possessing potent physiologic anti-angiogenic activity that negates VEGF activity. The role of PEDF in decreasing abnormal neovascularization by exerting its anti-angiogenic effect that inhibits pro-angiogenic factors, including VEGF, has been investigated mainly in the eye and in cancer. This review summarizes the function of PEDF in the reproductive system, showing its hormonal regulation and its anti-angiogenic activity. Furthermore, some pathologies of the female reproductive organs, including endometriosis, ovarian hyperstimulation syndrome, polycystic ovary syndrome, and others, are associated with a faulty angiogenic process. This review illuminates the role of PEDF in their pathogenesis and treatment. Collectively, we can conclude that although PEDF seems to play an essential role in the physiology and pathophysiology of the reproductive system, its full role and mechanism of action still need to be elucidated.

Peripheral changes in endometriosis-associated pain

BACKGROUND

Pain remains the cardinal symptom of endometriosis. However, to date, the underlying mechanisms are still only poorly understood. Increasing evidence points towards a close interaction between peripheral nerves, the peritoneal environment and the central nervous system in pain generation and processing. Recently, studies demonstrating nerve fibres and neurotrophic and angiogenic factors in endometriotic lesions and their vicinity have led to increased interest in peripheral changes in endometriosis-associated pain. This review focuses on the origin and function of these nerves and factors as well as possible peripheral mechanisms that may contribute to the generation and modulation of pain in women with endometriosis.

METHODS

We conducted a systematic search using several databases (PubMed, MEDLINE, EMBASE and CINAHL) of publications from January 1977 to October 2013 to evaluate the possible roles of the peripheral nervous system in endometriosis pathophysiology and how it can contribute to endometriosis-associated pain.

RESULTS

Endometriotic lesions and peritoneal fluid from women with endometriosis had pronounced neuroangiogenic properties with increased expression of new nerve fibres, a shift in the distribution of sensory and autonomic fibres in some locations, and up-regulation of several neurotrophins. In women suffering from deep infiltrating endometriosis and bowel endometriosis, in which the anatomical distribution of lesions is generally more closely related to pelvic pain symptoms, endometriotic lesions and surrounding tissues present higher nerve fibre densities compared with peritoneal lesions and endometriomas. More data are needed to fully confirm a direct correlation between fibre density in these locations and the amount of perceived pain. A better correlation between the presence of nerve fibres and pain symptoms seems to exist for eutopic endometrium. However, this appears not to be exclusive to endometriosis. No correlation between elevated neurotrophin levels and pain severity appears to exist, suggesting the involvement of other mediators in the modulation of pain.

CONCLUSIONS

The increased expression of neurotrophic factors and nerve fibres in endometriotic lesions, eutopic endometrium and the peritoneum imply a role of such peripheral changes in the pathogenesis of endometriosis-associated pain. However, a clear link between these findings and pain in patients with endometriosis has so far not been demonstrated.

Combined blockade of angiotensin II type 1 receptor and activation of peroxisome proliferator-activated receptor-γ by telmisartan effectively inhibits vascularization and growth of murine endometriosis-like lesions

STUDY QUESTION

Is telmisartan effective in the treatment of endometriosis?

SUMMARY ANSWER

Combined blockade of angiotensin II type 1 receptor (AT1R) and activation of peroxisome proliferator-activated receptor (PPAR)-γ by telmisartan inhibits vascularization and growth of murine endometriosis-like lesions.

WHAT IS KNOWN ALREADY

AT1R and PPAR-γ are involved in the regulation of inflammation, proliferation and angiogenesis. These processes are also crucial for the pathogenesis of endometriosis and both receptors are expressed in endometrial tissue. Telmisartan is a partial agonist of PPAR-γ, which additionally blocks AT1R.

STUDY DESIGN, SIZE, DURATION

This was a randomized study in the mouse dorsal skinfold chamber and peritoneal model of endometriosis. Endometriosis-like lesions were induced in dorsal skinfold chambers of 21 female C57BL/6 mice, and in the peritoneal cavity of 15 additional animals, which were daily treated with an i.p. injection of pioglitazone (10 mg/kg, n = 12), telmisartan (10 mg/kg, n = 12) or vehicle (5% dimethyl sulfoxide (DMSO), n = 12) throughout an observation period of 14 and 28 days, respectively.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The anti-angiogenic actions of pioglitazone, a full PPAR-γ agonist, and telmisartan were firstly assessed in vitro by an aortic ring assay. Endometriosis-like lesions were induced in the dorsal skinfold chamber or peritoneal cavity and the effects of telmisartan and pioglitazone on their vascularization, immune cell content and growth were studied by intravital fluorescence microscopy, high-resolution ultrasound imaging as well as histological, immunohistochemical and immunofluorescent analyses. Additional quantitative real-time polymerase chain reaction (qRT-PCR) arrays served for gene expression profiling of the lesions. To limit the role of chance, the experiments were conducted under standardized laboratory conditions with appropriate vehicle-treated controls. Statistical significance was accepted for a value of P < 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

Telmisartan inhibited vascular sprout formation of aortic rings more effectively than pioglitazone. Accordingly, endometriosis-like lesions in dorsal skinfold chambers of telmisartan-treated animals exhibited a markedly lower functional microvessel density and blood perfusion. High-resolution ultrasound analyses of peritoneal endometriosis-like lesions revealed that the compound inhibited the stromal tissue growth, resulting in a significantly reduced final lesion volume. In contrast, the development of cysts did not differ between the groups. Moreover, telmisartan induced an up-regulation of PPAR-γ and a down-regulation of AT1R proteins in endometriosis-like lesions, which was associated with a decreased density of CD31-positive microvessels, a reduced immune cell content and a lower number of Ki67-positive proliferating cells. qRT-PCR arrays further demonstrated an inhibitory action of telmisartan on the expression of several angiogenic and inflammatory genes.

LIMITATIONS, REASONS FOR CAUTION

Endometriosis-like lesions were induced by syngeneic tissue transplantation into recipient mice without the use of pathological endometriotic tissue of human nature. Therefore, the results obtained in this study may not fully relate to human patients with endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrates that telmisartan inhibits vascularization, immune cell content and growth of endometriosis-like lesions. Accordingly, the combined blockade of AT1R and activation of PPAR-γ represents a promising new concept in the development of novel compounds for the treatment of endometriosis.

STUDY FUNDING/COMPETING INTEREST(S)

There was no specific funding of this study. The authors have no conflicts of interest to declare.

Theories on the pathogenesis of endometriosis

Endometriosis is a common, chronic inflammatory disease defined by the presence of extrauterine endometrial tissue. The aetiology of endometriosis is complex and multifactorial, where several not fully confirmed theories describe its pathogenesis. This review examines existing theories on the initiation and propagation of different types of endometriotic lesions, as well as critically appraises the myriad of biologically relevant evidence that support or oppose each of the proposed theories. The current literature suggests that stem cells, dysfunctional immune response, genetic predisposition, and aberrant peritoneal environment may all be involved in the establishment and propagation of endometriotic lesions. An orchestrated scientific and clinical effort is needed to consider all factors involved in the pathogenesis of this multifaceted disease and to propose novel therapeutic targets to reach effective treatments for this distressing condition.

Luminal epithelium in endometrial fragments affects their vascularization, growth and morphological development into endometriosis-like lesions in mice

In endometriosis research, endometriosis-like lesions are usually induced in rodents by transplantation of isolated endometrial tissue fragments to ectopic sites. In the present study, we investigated whether this approach is affected by the cellular composition of the grafts. For this purpose, endometrial tissue fragments covered with luminal epithelium (LE(+)) and without luminal epithelium (LE(-)) were transplanted from transgenic green-fluorescent-protein-positive (GFP(+)) donor mice into the dorsal skinfold chamber of GFP(-) wild-type recipient animals to analyze their vascularization, growth and morphology by means of repetitive intravital fluorescence microscopy, histology and immunohistochemistry during a 14-day observation period. LE(-) fragments developed into typical endometriosis-like lesions with cyst-like dilated endometrial glands and a well-vascularized endometrial stroma. In contrast, LE(+) fragments exhibited a polypoid morphology and a significantly reduced blood perfusion after engraftment, because the luminal epithelium prevented the vascular interconnection with the microvasculature of the surrounding host tissue. This was associated with a markedly decreased growth rate of LE(+) lesions compared with LE(-) lesions. In addition, we found that many GFP(+) microvessels grew outside the LE(-) lesions and developed interconnections to the host microvasculature, indicating that inosculation is an important mechanism in the vascularization process of endometriosis-like lesions. Our findings demonstrate that the luminal epithelium crucially affects the vascularization, growth and morphology of endometriosis-like lesions. Therefore, it is of major importance to standardize the cellular composition of endometrial grafts in order to increase the validity and reliability of pre-clinical rodent studies in endometriosis research.

Animal models for anti-angiogenic therapy in endometriosis

Endometriosis is a gynecological disease characterized by the growth of endometrium outside of the uterine cavity. It is often associated with dysmenorrhea, dyspareunia, pelvic pain and infertility. One of the key requirements for endometriotic lesions to survive is development of a blood supply to support their growth. Indeed, dense vascularization is characteristic feature of endometriotic lesions. This has led to the idea that suppression of blood vessel growth (anti-angiogenic therapy) may be a successful therapeutic approach for endometriosis. Potential effectiveness of anti-angiogenic therapies has been assessed in some animal models but there are no reports of human clinical trials. Without understanding the specific mechanism by which endometriosis lesions establish a new blood supply, short-term animal experiments will have limited value for translation into human medicine. Further, it is crucial to use appropriate animal models to assess efficacy of anti-angiogenic compounds. Syngeneic and autologous rodent models, where endometrial fragments are auto-transplanted into the peritoneal cavity are commonly used in anti-angiogenic therapy studies. Another approach is xenograft models where human endometrium is engrafted into immunodeficient mice. Here we review the animal models and experimental techniques used to evaluate anti-angiogenic therapies for endometriosis. We also review our own work on the role of stromal cell derived factor-1 in the recruitment of endothelial progenitor cells in endometriotic lesion angiogenesis, and the effects of the anti-angiogenic peptide ABT-898, a thrombospondin-1 mimetic, on endometriotic lesion growth and vascular development.

Angiogenesis and endometriosis

A comprehensive review was performed to survey the role of angiogenesis in the pathogenesis of endometriosis. This is a multifactorial disease in which the development and maintenance of endometriotic implants depend on their invasive capacity and angiogenic potential. The peritoneal fluid of patients with endometriosis is a complex suspension carrying inflammatory cytokines, growth factors, steroid hormones, proangiogenic factors, macrophages, and endometrial and red blood cells. These cells and their signaling products concur to promote the spreading of new blood vessels at the endometriotic lesions and surroundings, which contributes to the endometriotic implant survival. Experimental studies of several antiangiogenic agents demonstrated the regression of endometriotic lesions by reducing their blood supply. Further studies are necessary before these novel agents can be introduced into clinical practice, in particular the establishment of the safety of anti-angiogenic medications in women who are seeking to become pregnant.

Blocking of stromal cell-derived factor-1 reduces neoangiogenesis in human endometriosis lesions in a mouse model

PROBLEM

Endometriosis affects 5-10% of women and is characterized by the growth of endometrial tissue outside of the uterus. Establishing new blood supply is a fundamental requirement for endometriosis lesion growth. Endothelial progenitor cells (EPCs), recruited by stromal cell-derived factor-1 (SDF-1), contribute to neoangiogenesis in endometriotic lesions. We hypothesized that SDF-1 is central to the neoangiogenesis and survival of endometriotic lesions, and blocking of SDF-1 will reduce vascularization of lesions in a mouse model.

METHOD OF STUDY

Using immunohistochemistry, we evaluated SDF-1 and CD34(+) EPCs in human endometriotic lesions and normal endometrium samples. EPCs were co-localized using CD34 and VEGFR2. Effects of SDF-1 blocking on endometriotic lesion survival were assessed in BALB/c-Rag2(-/-) /IL2rγ(-/-) mice engrafted with human endometrium and treated with SDF-1-blocking antibody or an isotype control. Weekly blood samples from experimental mice were analyzed for cytokines and EPCs.

RESULTS

SDF-1 and CD34(+) EPCs were abundant in human endometriotic lesions compared with eutopic endometrium. In our mouse model, SDF-1-blocking antibody reduced CD31(+) microvessels compared with isotype control.

CONCLUSION

Blocking SDF-1 reduces neovascularization and survival of lesions in a mouse model of endometriosis.

Pigment epithelial-derived factor expression in endometriotic lesions in a rat model of endometriosis

Angiogenesis is a prerequisite for endometriotic lesion formation and development. Pigment epithelium-derived factor (PEDF) is a potential inhibitor of angiogenesis. The objective of this study was to detect PEDF immunolocalization in endometriotic lesions and the correlation with vascular endothelial growth factor (VEGF) and microvascular density (MVD) in a rat model of endometriosis. A subcutaneous endometriosis rat model was established by using auto-transplantation. Expression of PEDF, VEGF and MVD labeled by von Willebrand factor (v-WF) in endometriotic lesions and endometrial tissues was evaluated using immunohistochemical staining. We detected lower PEDF immunostaining and higher VEGF and MVD immunostaining in active lesions in a rat model of endometriosis than that in endometriosis endometrium or control endometrium (P<0.05), but no differences between endometriosis and control endometrium were found (P>0.05). In lesions, PEDF expression was negatively correlated with VEGF expression, MVD or sizes of cysts (P<0.01). On the contrary, both VEGF expression and MVD were positively correlated with lesion sizes (P<0.05). In addition, VEGF expression was positively correlated with MVD (P<0.01). Our results suggest that PEDF might be involved in the pathogenesis of endometriosis and may lead to novel treatment for this disease.

Peritoneal fluid reduces angiogenesis-related microRNA expression in cell cultures of endometrial and endometriotic tissues from women with endometriosis

Endometriosis, defined as the presence of endometrium outside the uterus, is one of the most frequent gynecological diseases. It has been suggested that modifications of both endometrial and peritoneal factors could be implicated in this disease. Endometriosis is a multifactorial disease in which angiogenesis and proteolysis are dysregulated. MicroRNAs (miRNAs) are small non-coding RNAs that regulate the protein expression and may be the main regulators of angiogenesis. Our hypothesis is that peritoneal fluid from women with endometriosis could modify the expression of several miRNAs that regulate angiogenesis and proteolysis in the endometriosis development. The objective of this study has been to evaluate the influence of endometriotic peritoneal fluid on the expression of six miRNAs related to angiogenesis, as well as several angiogenic and proteolytic factors in endometrial and endometriotic cell cultures from women with endometriosis compared with women without endometriosis.

Defining future directions for endometriosis research: workshop report from the 2011 World Congress of Endometriosis In Montpellier, France

Endometriosis, defined as estrogen-dependent lesions containing endometrial glands and stroma outside the uterus, is a chronic and often painful gynecological condition that affects 6% to 10% of reproductive age women. Endometriosis has estimated annual costs of US $12 419 per woman (approximately €9579), comprising one-third of the direct health care costs with two-thirds attributed to loss of productivity. Decreased quality of life is the most important predictor of direct health care and total costs. It has been estimated that there is a mean delay of 6.7 years between onset of symptoms and a surgical diagnosis of endometriosis, and each affected woman loses on average 10.8 hours of work weekly, mainly owing to reduced effectiveness while working. To encourage and facilitate research into this debilitating disease, a consensus workshop to define future directions for endometriosis research was held as part of the 11th World Congress on Endometriosis in September 2011 in Montpellier, France. The objective of this workshop was to review and update the endometriosis research priorities consensus statement developed following the 10th World Congress on Endometriosis in 2008.(1) A total of 56 recommendations for research have been developed, grouped under 6 subheadings: (1) diagnosis, (2) classification and prognosis, (3) clinical trials, treatment, and outcomes, (4) epidemiology, (5) pathophysiology, and (6) research policy. By producing this consensus international research priorities statement, it is the hope of the workshop participants that researchers will be encouraged to develop new interdisciplinary research proposals that will attract increased funding support for work on endometriosis.

Endometriosis, a disease of the macrophage

Endometriosis, a common cause of pelvic pain and female infertility, depends on the growth of vascularized endometrial tissue at ectopic sites. Endometrial fragments reach the peritoneal cavity during the fertile years: local cues decide whether they yield endometriotic lesions. Macrophages are recruited at sites of hypoxia and tissue stress, where they clear cell debris and heme-iron and generate pro-life and pro-angiogenesis signals. Macrophages are abundant in endometriotic lesions, where are recruited and undergo alternative activation. In rodents macrophages are required for lesions to establish and to grow; bone marrow-derived Tie-2 expressing macrophages specifically contribute to lesions neovasculature, possibly because they concur to the recruitment of circulating endothelial progenitors, and sustain their survival and the integrity of the vessel wall. Macrophages sense cues (hypoxia, cell death, iron overload) in the lesions and react delivering signals to restore the local homeostasis: their action represents a necessary, non-redundant step in the natural history of the disease. Endometriosis may be due to a misperception of macrophages about ectopic endometrial tissue. They perceive it as a wound, they activate programs leading to ectopic cell survival and tissue vascularization. Clearing this misperception is a critical area for the development of novel medical treatments of endometriosis, an urgent and unmet medical need.

Interleukin-19 and interleukin-22 serum levels are decreased in patients with ovarian endometrioma

OBJECTIVE

To determine the serum levels of interleukin (IL)-10 family ILs in women with ovarian endometriosis and investigate the correlation of these levels with disease activity.

DESIGN

A case-control laboratory study.

SETTING

Tertiary-care university hospital.

PATIENT(S)

Two hundred nineteen women, with (n = 112) and without (n = 107) endometriosis.

INTERVENTION(S)

Complete surgical excision with pathological analysis.

MAIN OUTCOME MEASURE(S)

Blood samples were obtained during surgical procedures. IL-10, -19, -20, and -22 were assayed by ELISA in sera, and the concentrations correlated with the extent and the severity of the disease.

RESULT(S)

IL-19 was detectable in 18.3% and IL-22 in 47.9% of sera samples from all 219 women studied. Serum IL-19 was lower in women with endometriosis (median, 292.7 pg/mL; range, 32.2-1,339.3) than in endometriosis-free women (median, 1,035.8 pg/mL; range, 32.2-2,000.0). In addition, serum IL-22 levels were decreased in women affected by endometriosis (median, 352.0 pg/mL; range, 31.2-1,392.2) as compared with endometriosis-free women (median, 709.2 pg/mL; range, 73.3-2,012.0). We found significant correlations between serum IL-22 concentrations and intensity of deep dyspareunia (r = -0.303) and noncyclic chronic pelvic pain (r = -0.212). IL-19 was correlated with the intensity of deep dyspareunia (r = -0.749).

CONCLUSION(S)

Serum IL-19 and IL-22 are decreased in women with ovarian endometrioma. IL-10 family ILs may be involved in the pathogenesis of endometriosis.

The relation of pelvic pain and dense adhesions to Doppler ultrasound findings in patients with ovarian endometriomas

PURPOSE

To study the relation of pelvic pain symptoms and pelvic adhesions to Doppler ultrasound findings in patients with ovarian endometriomas.

METHODS

62 patients who underwent laparoscopic surgery for endometrioma were divided into two groups according to their pelvic pain symptoms. Group 1 (n = 27) included patients with pelvic pain, group 2 (n = 35) asymptomatic patients. Patients were evaluated for the vascularization of endometrioma by transvaginal color and power Doppler ultrasonography before the surgery. The presence and amount of blood flow reported in terms of a color scale, pulsed Doppler indices, and dense pelvic adhesions were compared between the groups. The relation of Doppler ultrasound findings to the dense pelvic adhesions was also analyzed.

RESULTS

Blood flow was present in 74.1 % (n = 20) of patients in group 1 and 68.6 % (n = 24) in group 2 (p = 0.63). The volume and vascularization of the endometriomas, pulsed Doppler indices, stage of endometriosis, and the presence of dense pelvic adhesions were also similar. Patients with dense pelvic adhesions had significantly higher amount of blood flow compared to patients without adhesions (p = 0.006), but the mean pulsatility index and resistance index were not different between the groups (p = 0.55 and 0.59, respectively).

CONCLUSIONS

Pelvic pain symptoms were not found to be related to endometrioma vascularization. On the other hand, we observed an association between higher vascularized endometrioma and the presence of dense pelvic adhesions.

Pathogenesis and pathophysiology of endometriosis

Originally described over three hundred years ago, endometriosis is classically defined by the presence of endometrial glands and stroma in extrauterine locations. Endometriosis is an inflammatory, estrogen-dependent condition associated with pelvic pain and infertility. This work reviews the disease process from theories regarding origin to the molecular basis for disease sequelae. A thorough understanding of the histopathogenesis and pathophysiology of endometriosis is essential to the development of novel diagnostic and treatment approaches for this debilitating condition.

Decreased expression of pigment epithelium-derived factor and increased microvascular density in ovarian endometriotic lesions in women with endometriosis

OBJECTIVES

To determine whether women with endometriosis have altered expression of pigment epithelium-derived factor (PEDF) in ovarian endometriotic lesions as compared to women without endometriosis.

STUDY DESIGN

Ectopic and eutopic and normal endometrial tissues were sampled from 40 women with ovarian endometriosis and 20 control women, respectively. Endometrial PEDF expression and microvascular density (MVD) using an antibody to von Willebrand factor (vWF) and alpha-smooth muscle actin (α-SMA) were evaluated by using immunohistochemical staining.

RESULTS

We detected decreased PEDF expression and increased MVD using anti-vWF and -α-SMA in ovarian endometriotic lesions in women with endometriosis compared with the control group. In women with endometriosis, the MVD using anti-vWF and -α-SMA but not PEDF expression in ovarian endometriotic lesions correlated with the size of ovarian endometriotic cysts and the severity of the disease. Moreover, the MVD using anti-vWF was negatively correlated with PEDF expression in control endometrium but not in ovarian endometriotic lesions.

CONCLUSIONS

Our results suggest that decreased PEDF expression and increased MVD in ovarian endometriotic lesions might play an important role in the pathogenesis of ovarian endometriosis.

Thrombospondin-1 mimetic peptide ABT-898 affects neovascularization and survival of human endometriotic lesions in a mouse model

Endometriosis is a common cause of pelvic pain and infertility in women, and a common indication for hysterectomy, yet the disease remains poorly diagnosed and ineffectively treated. Because endometriotic lesions require new blood supply for survival, inhibiting angiogenesis could provide a novel therapeutic strategy. ABT-898 mimics the antiangiogenic properties of thrombospondin-1, so we hypothesized that ABT-898 will prevent neovascularization of human endometriotic lesions and that ABT-898 treatment will not affect reproductive outcomes in a mouse model. Endometriosis was induced in BALB/c-Rag2(-/-)Il2rg(-/-) mice by surgical implantation of human endometrial fragments in the peritoneal cavity. Mice received daily injections of ABT-898 for 21 days. Flow cytometry was performed to measure circulating endothelial progenitor cells in peripheral blood. Cytokines were measured in plasma samples. Half of the ABT-898-treated and control mice were euthanized to assess neovascularization of endometriotic lesions, using CD31(+) immunofluorescence. The remaining mice were mated and euthanized at gestation day 12. Endometriotic lesions increased circulating endothelial progenitor cells 13 days after engraftment, relative to baseline. Endometriotic lesions from ABT-898-treated mice exhibited reduced neovascularization, compared with controls, and lesions had fewer CD31(+) microvessels. Chronic treatment with ABT-898 did not lead to any fetal anomalies or affect litter size at gestation day 12, compared with controls. Our results suggest that ABT-898 inhibits neovascularization of human endometriotic lesions without affecting mouse fecundity.