Immunomodulators and aromatase inhibitors: are they the next generation of treatment for endometriosis?

A Systematic Review of Systematic Reviews on the Use of Aromatase Inhibitors for the Treatment of Endometriosis: The Evidence to Date

Endometriosis is a chronic gynecologic condition that affects around 6-10% of reproductive age women. This clinical entity is characterized with pelvic pain, dysmenorrhea, dyspareunia, and infertility which are the most often presenting symptoms. Aromatase P450 is the key enzyme for ovarian estrogen biosynthesis and there is evidence that endometriotic lesions express aromatase and are able to synthesize their own estrogens. Aromatase inhibitors (AIs) are potent drugs that suppress the estrogen synthesis via suppression of aromatase. We performed a systematic review of systematic reviews and narrative reviews on the use of aromatase inhibitors in the medical management of endometriosis. We searched: PubMed (1950-2022), Google Scholar (2004-2022), Cochrane Library (2010-2022) and Researchgate (2010-2022). The search included the following medical subject headings (MeSH) or keywords: "Aromatase Inhibitors" AND "Endometriosis" AND "Systematic reviews" OR "Systematic review" AND "Reviews" OR "Reviews" AND "Endometriosis". The electronic database search yielded initially 12,106 studies from the different databases. Further assessment of the studies resulted in exclusion of (n = 12,015) studies due to duplicates and irrelevance; Finally, 24 studies were selected for inclusion, 5 were Systematic reviews and 19 were Narrative reviews. The 5 systematic reviews were assessed by AMSTAR-2 criteria and were found to have low quality. Narrative reviews were assessed with SANRA criteria and were found to have high-quality aromatase inhibitors are potent drugs that can manage the endometriosis-related symptoms in cases where initial medical management has failed to show positive results. However, their use is limited by the adverse effects that are linked with menopausal symptoms. aromatase inhibitors can be administered as an alternative treatment in patients. Future studies with randomized design are required to reach safer conclusions and further investigation. These studies should define the therapeutic dose, new add-back therapy modalities. Future directions should examine the most-appropriate way of administration and the duration of therapy.

Androgens, Endometriosis and Pain

The intriguing relationship between androgens, endometriosis and chronic pain continues to unfold. Determining this relationship is of crucial importance to gynecologists managing people with these conditions, as common treatments dramatically alter her hormonal profiles, with both intended and unintended consequences. Although they may be present in the same individual, there is a recognized disconnect between pain or pain-related symptoms, and the presence or extent of endometriosis lesions. Reduced androgen levels provide a potential mechanism to link the development of endometriosis lesions and the presence of chronic pain. This research paper expands the presentation of our research at the World Endometriosis Congress in 2021, subsequently published in the Journal of Pain Research which demonstrated a strong inverse relationship between androgen levels and days per month of pelvic and period pain. Here we extend and further explore the evidence for a role for androgens in the etiology and management of dysmenorrhea and pelvic pain in women, both with and without endometriosis. We explore the potential for inflammation to induce low androgen levels and consider ways in which clinicians can optimize levels of androgens when treating women with these conditions. This article prompts the question: Is it estrogens that predispose people to a life of pain, or androgens that are protective?

Meta-Analysis of Chinese Traditional Medicine Bushen Huoxue Prescription for Endometriosis Treatment

Objectives

To evaluate the efficacy and safety of Bushen Huoxue prescription (BSHXP) for endometriosis.

Methods

A meta-analysis was performed, and studies were searched from the seven databases from the date of database establishment to April 30, 2017. Randomized controlled trials (RCTs) that explored the efficacy and safety of BSHXP for patients with endometriosis were included. Two assessors independently reviewed each trial. The Cochrane Risk of Bias assessment tool was used for quality assessment.

Results

In the 13 included studies, the total effectiveness rates of BSHXP were higher than those of Western medicine (RR, 1.55; 95% CI, 1.03–2.32; P = 0.04), but the dysmenorrhea alleviation rates of the two treatments did not significantly differ (RR, 1.28; 95% CI, 0.70–2.34; P = 0.42). The pregnancy rates of BSHXP were also higher than those of hormone therapy (RR, 1.99; 95% CI, 1.17–3.39; P = 0.01). However, whether BSHXP is more effective than Western medicine in diminishing endometriotic cyst remains unknown.

Conclusions

Our study provides evidence that BSHXP is effective and safe for endometriosis, but this evidence is inconclusive because of the low methodological quality of the included RCTs. Our findings suggest that BSHXP is an alternative drug for endometriosis, but it should be further examined in future clinical research.

Endometriosis: bright future for a cloudy past?

New estrogen receptor ligands arrest endometriotic implant survival but spare reproductive cycles in a mouse model of endometriosis, thus forging a path to new treatment options (Zhao et al., this issue).

Immunohistochemical alterations of cajal-like type of tubal interstitial cells in women with endometriosis and tubal ectopic pregnancy

PURPOSE

The aim of the study was to observe alterations of pacemaker cells termed cajal-like type of tubal interstitial cells (t-ICC) in oviduct from early-stage EMs and tEP, discuss underlying mechanisms and potential role in tubal factor infertility (TFI).

METHODS

Ten patients with early-stage EMs, 10 with unruptured tEP and 10 control subjects were included in this retrospective comparative study, received adnexectomy (salpingectomy) and/or hysterectomy. Paraffin-embedded full-thickness isthmic segment of oviduct specimens received immunohistochemistry with c-kit/CD117 antibody. Network distribution and area density of cells with features of t-ICC were analyzed.

RESULTS

t-ICC was detected mainly in lamina propria and smooth muscle layers. t-ICC lost its network integrity, became less densely stained, sparse and almost invisible with relatively very rare connections in EMs and tEP, apparently differing in morphology of t-ICC from control, which demonstrated rich t-ICC immunostaining and intact network. Further quantitative analysis showed the area density of t-ICC decreased significantly in early-stage EMs and tEP compared with the control (73.9 ± 8.8 vs. 156 ± 18.3 mm(2); and 76 ± 7.4 vs. 156 ± 18.3 mm(2); both P < 0.001).

CONCLUSIONS

We revealed that t-ICC underwent certain degree of cell damage, suggested that decreased expression of t-ICC network may be involved in early development of EMs and tEP, and might serve as an explanation for TFI in these patients.

Simvastatin decreases invasiveness of human endometrial stromal cells

Recently we reported that statins, the competitive inhibitors of the key enzyme regulating the mevalonate pathway, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), decrease proliferation of human endometrial stromal (HES) cells. Furthermore, we found that simvastatin treatment reduces the number and the size of endometrial implants in a nude mouse model of endometriosis. The present study was undertaken to investigate the effect of simvastatin on HES cell invasiveness and on expression of selected genes relevant to invasiveness: matrix metalloproteinase 2 (MMP2), MMP3, tissue inhibitor of matrix metalloproteinase 2 (TIMP2), and CD44. Because statin-induced inhibition of HMGCR reduces the production of substrates for isoprenylation-geranylgeranyl pyrophosphate (GGPP) and farnesyl pyrophosphate (FPP)-the effects of GGPP and FPP were also evaluated. Simvastatin induced a concentration-dependent reduction of invasiveness of HES cells. This effect of simvastatin was abrogated by GGPP but not by FPP. Simvastatin also reduced the mRNA levels of MMP2, MMP3, and CD44, but increased TIMP2 mRNA; all these effects of simvastatin were partly or entirely reversed in the presence of GGPP. The present findings provide a novel mechanism of action of simvastatin on endometrial stroma that may explain reduction of endometriosis in animal models of this disease. Furthermore, the presently described effects of simvastatin are likely mediated, at least in part, by inhibition of geranylgeranylation.

Primate model research for endometriosis

Endometriosis is defined as the existence of endometrial tissue outside the uterine cavity, and it includes a chronic, inflammatory reaction associated with female infertility and pelvic pain. Endometriosis occurs in 7 to 10% of women. Although it has been studied for more than 50 years, the pathogenesis and development of endometriosis are still poorly understood. There is no curative therapy for endometriosis, which often recurs after surgical or medical treatment. There is a consensus that the adverse current of menstrual blood plays a crucial role in the development of endometriosis. This places a major limitation on research using rodent models of endometriosis, although these are still widely employed, because rodents do not menstruate and endometriosis does not occur spontaneously in these animals. In fact, menstruation and spontaneous endometriosis only occur in women and some non-human primates, making models that employ non-human primates the best animal models for research into the pathogenesis, pathophysiology, spontaneous onset, and treatment of endometriosis. This review assesses the effectiveness and potential of the non-human primate models of endometriosis. It also describes the current findings and theories on the pathogenesis of endometriosis that have been obtained by research using non-human primates.

Symptomatic intestinal endometriosis requiring surgical resection: clinical presentation and preoperative diagnosis

OBJECTIVES

Intestinal endometriosis (IE) can present with varied symptoms, making the diagnosis difficult. Modalities have been described to evaluate IE, but few can provide a confirmatory diagnosis. A preoperative diagnosis of IE may help guide management. We sought to describe the presentation, diagnostic evaluation, histology and operative management of 89 patients with tissue-confirmed symptomatic IE.

METHODS

The records of 89 patients from a single institution with histologically confirmed, symptomatic IE from 1 January 1994 to 30 September 2009 were reviewed.

RESULTS

Abdominal pain was the most common symptom in patients with IE; however, rectal bleeding was significantly associated with IE of the distal colon (P=0.02), while dysfunctional uterine bleeding was seen more in patients with proximal IE (P=0.01). Preoperative confirmation of IE was uncommon; colonoscopy with biopsy confirmed the diagnosis in 29.6% of patients tested and only 15% of patients with IE had histologic lesions involving mucosa. In the five patients who underwent endoscopic ultrasound (EUS), the diagnosis of IE was established in all cases (n=4) where histology or cytology was obtained. Malignancy was considered nearly as frequently as IE preoperatively, and 90.4% of patients underwent laparotomy as the initial surgical approach.

CONCLUSIONS

IE can present with a variety of manifestations, which may provide clues to location of bowel affected. Patients with known pelvic endometriosis and rectal bleeding are more likely to have distal bowel affected; EUS with tissue sampling may play a role if routine endoscopy fails to reveal the diagnosis. Making a diagnosis of IE preoperatively may allow for less invasive surgical approaches and better patient outcomes.

The effect of Telmisartan on collagen biosynthesis depends on the status of estrogen activation in breast cancer cells

PPAR-gamma and estrogen receptor belong to a family of nuclear hormone receptors that were shown to affect transcriptional activity of each other. The angiotensin II type 1 receptor antagonist Telmisartan is a well known PPAR-gamma ligand. The effect of Telmisartan-induced PPAR-gamma activation on collagen biosynthesis was studied in the estrogen-dependent (MCF-7 cells expressing alpha and beta receptors) and estrogen-independent (MDA-MB 231, expressing only beta receptor) cell lines. We have found that the presence of estrogen in growth medium (2nM) augmented collagen biosynthesis in both cell lines. An addition to the growth medium of PPAR-gamma agonist, Telmisartan, but not rosiglitazone or clofibrat, other PPAR-gamma agonists, induced inhibition of collagen biosynthesis in MCF-7 cells, cultured in the presence of estrogen, while it had no effect on collagen biosynthesis in MDA-MB-231 cells. On the other hand, Telmisartan induced stimulation of collagen biosynthesis in MCF-7 cells cultured in the absence of estrogen (or in conditions of estrogen receptor removal by ICI 182-780-dependent degradation) and had no effect on similarly cultured MDA-MB-231 cells. The effect of Telmisartan on collagen biosynthesis was found specific for PPAR-gamma and not for angiotensin II type 1 since Losartan (specific antagonist of angiotensin II type 1 receptor) in the presence of estradiol did not induce inhibition of this protein in MCF-7 cells. The mechanism of the inhibition was found at the level of NF-kB (known inhibitor of collagen gene expression) and MAPK signaling. PPAR-gamma ligands stimulated expression of NF-kB, while they inhibited expression of p-38 but not ERK1/ERK2. The data suggest that the effect of Telmisartan on collagen biosynthesis in breast cancer cells depends on the status of estrogen receptor activation and the inhibitory effect of Telmisartan on the process requires functional alpha estrogen receptor.

The non-human primate model of endometriosis: research and implications for fecundity

The development of an animal model of endometriosis is crucial for the investigation of disease pathogenesis and therapeutic intervention. These models will enhance our ability to evaluate the causes for the subfertility associated with disease and provide a first-line validation of treatment modulators. Currently rodents and non-human primate models have been developed, but each model has their limitations. The aim of this manuscript is to summarize the current findings and theories on the development of endometriosis and disease progression and the effectiveness of therapeutic targets using the experimental induced model of endometriosis in the baboon (Papio anubis).

Nonhuman primate models for translational research in endometriosis

Endometriosis, defined as the ectopic presence of endometrial-like cells, is associated with infertility and pelvic pain in women. Whereas pathogenesis and spontaneous evolution of endometriosis are still poorly understood, recurrences after surgical therapy or after medical treatment are common. Spontaneous endometriosis occurs only in women and in nonhuman primates (NHPs). Inbred rhesus monkeys kept in colonies offer an attractive preclinical model to study the inheritance of spontaneous endometriosis. Baboons with spontaneous or induced endometriosis appear to be the best NHP model to study pathogenesis, pathophysiology, spontaneous evolution and new medical treatment options. In baboons, induction of endometriosis after intrapelvic injection of menstrual endometrium leads to biological changes in peritoneal cavity and in endometrium. This induction process may allows the study of cause-effect relationships which may lead to the discovery of new biomarkers for the development of new non-invasive diagnostic tests and drugs that may prevent or treat endometriosis.

Is aromatase expression in the endometrium the cause of endometriosis and related infertility?

Aromatase expression in the endometrium seems to play a pivotal role in the development of endometriotic lesions. Because inflammatory mediators such as prostaglandin E2 appear to activate aromatase in the cells of the endometrial stroma, it was hypothesised that the ensuing inflammation caused by the arrival of aromatase-positive cells in the peritoneal cavity would stimulate local estrogen production, which would in turn facilitate the development of endometriotic lesions by suppressing macrophage phagocytosis. Aromatase expression in the eutopic endometrium will also hamper ovum nidation, thus causing infertility. Progestins, such as gestodene and danazol, are potent inhibitors of aromatase expression in the endometrium, and the use of vaginal rings with danazol in doses that do not block ovulation is associated with the occurrence of pregnancy in patients with severe endometriosis without the need for surgery. A local effect on the endometrium suppressing aromatase expression has been suggested as a possible mechanism of action for the danazol ring.

Peritoneal macrophage depletion by liposomal bisphosphonate attenuates endometriosis in the rat model

BACKGROUND

Activation of macrophages is central to the implantation of endometriosis (EM). We examined the hypothesis that macrophage depletion by intraperitoneal (IP) injection of liposomal alendronate (LA) could result in EM attenuation in a rat model, thus supporting the notion of the pivotal role of macrophages in EM pathology.

METHODS

In this study, 90 rats were subjected to an EM model and were divided randomly into seven groups: five groups were treated by 4x once-weekly IP injections of LA (0.02, 0.1, 1, 5 or 10 mg/kg) and the other two groups received saline injections (control) or empty liposomes. Sham-operated rats also received empty liposomes. Depletion of circulating monocytes was determined by flow cytometry analyzes of blood specimens. Four weeks after the initial surgery, the number, size and weight of implants were recorded, adhesions were graded, macrophage infiltration was assessed and the peritoneal fluid was analyzed for monocyte chemotactic protein 1 (MCP-1) and tumor necrosis factor alpha (TNFalpha).

RESULTS

Monocyte depletion following IP LA administration resulted in an inhibitory effect on the initiation and growth of EM implants, as expressed by implantation rate, adhesion scoring, implants' size and weight (>0.1 mg/kg LA, P < 0.05). Reduced numbers of infiltrating macrophages were observed in implants of the 1 mg/kg LA group. Peritoneal fluid MCP-1 levels were negatively correlated with LA dose (P < 0.001), whereas no significant correlation could be found for TNFalpha.

CONCLUSIONS

Macrophage depletion using IP LA has been shown to effectively inhibit the initiation and growth of EM implants, in a rat EM model. The clear dose-response effect may be viewed as a confirmation of the validity of the concept and encourages further study.

Gene expression profiles and functional characterization of human immortalized endometriotic epithelial and stromal cells

OBJECTIVE

To determine whether immortalized endometriotic cells can be used as potential models to unravel pathophysiology/pathogenesis of endometriosis in humans.

DESIGN

In vitro study. Human immortalized endometriotic epithelial and stromal cells.

SETTING

College of Veterinary Medicine and Biomedical Sciences, Texas A&M University.

PATIENT(S)

Not applicable.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Gene expression pattern and prostaglandin E(2) production and activity of matrix metalloproteinase 2 and matrix metalloproteinase 9.

RESULT(S)

Several genes associated with estrogen and progesterone biosynthesis and signaling, cell cycle regulation, extracellular matrix degradation, angiogenesis, cell growth and survival, cytokine production, and prostaglandin E(2) biosynthesis, transport, and signaling were expressed in human immortalized endometriotic cells. These endometriotic epithelial and stromal cells exhibited migrating and invading potential, produced a high quantity of prostaglandin E(2), and showed higher matrix metalloproteinase 2 and matrix metalloproteinase 9 activity compared to normal endometrial, epithelial, and stromal cells.

CONCLUSION(S)

Human immortalized endometriotic epithelial and stromal cells could be used as ideal models to study the molecular and cellular aspects of endometriosis in humans.

Suppression of IL-1β-induced COX-2 expression by trichostatin A (TSA) in human endometrial stromal cells

OBJECTIVE

Over-production of cyclooxygenase-2 (COX-2) plays an important role in the positive feedback loop that leads to proliferation and inflammation in endometriosis. Following our observation that histone deacetylase inhibitors (HDACIs) trichostatin A (TSA) and valproic acid (VPA) can suppress proliferation of endometrial stromal cells, we sought to determine whether TSA suppresses IL-1beta-induced COX-2 expression in endometrial stromal cells.

STUDY DESIGN

In vitro study using a recently established immortalized endometrial stromal cell line. The stromal cells were pretreated with TSA before stimulation with IL-1beta, and COX-2 gene and protein expression was measured by real-time quantitative RT-PCR and Western blot analysis, respectively.

RESULTS

IL-1beta stimulated COX-2 expression in a concentration-dependent manner in endometrial stromal cells. The induced COX-2 gene and protein expression were suppressed by TSA pretreatment.

CONCLUSIONS

TSA suppresses IL-1beta-induced COX-2 gene and protein expression in endometrial stromal cells. This finding, coupled with the findings that TSA and another HDACI, valproic acid, suppress proliferation and induce cell cycle arrest, suggests that HDACIs are a promising class of compound that has therapeutic potential for endometriosis.

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.

Infliximab may reverse the toxic effects induced by tumor necrosis factor alpha in human spermatozoa: an in vitro model

OBJECTIVE

To examine the toxic effects of tumor necrosis factor alpha (TNF-alpha) on ejaculated spermatozoa and evaluate the ability of infliximab to reverse these effects.

DESIGN

Prospective controlled study.

SETTING

Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Thirty-one healthy sperm donors.

INTERVENTION(S)

Exposure of human spermatozoa to varying concentrations of TNF-alpha (100, 300, 400, 500 pg/mL, and 2.5 microg/mL) and infliximab (400 microg/mL).

MAIN OUTCOME MEASURE(S)

Sperm motility, functional integrity of plasma membrane, and DNA fragmentation.

RESULT(S)

Spermatozoa quality declined following incubation with TNF-alpha in a dose-dependent and time-dependent manner. Sperm motility and membrane integrity were higher in the samples incubated with TNF-alpha plus infliximab than in the samples treated with TNF-alpha only. These parameters improved significantly and were comparable with both controls and sperm incubated with infliximab alone. Similarly, the percentage of spermatozoa with DNA fragmentation improved significantly following incubation with TNF-alpha plus infliximab and again was comparable with both controls and sperm incubated with infliximab alone.

CONCLUSION(S)

Spermatozoa may be exposed to abnormal levels of TNF-alpha in the male reproductive tract or during their passage into the female reproductive tract (in cases of endometriosis). Exposing spermatozoa to pathological concentrations of TNF-alpha can result in significant loss of their functional and genomic integrity. Infliximab could potentially be used to help treat female infertility caused by endometriosis in those with elevated levels of TNF-alpha in their peritoneal fluid.

Treatment of endometriosis with transvaginal ultrasound-guided drainage under GnRH analogues and recombinant interleukin-2 left in the cysts

BACKGROUND

To analyze the therapeutic results of one dose of 3 million IU of recombinant interleukin-2 (rIL-2) left intracyst (group I) versus two doses with a 1-month interval (group II) after transvaginal ultrasound (US)-guided drainage of endometriomas under the effect of GnRH analogues.

METHODS

Prospective and randomized clinical trial (helped by a random number table) at a University Hospital. Twenty-four consecutive patients with endometriomas initially sent to us for laparotomy and conservative surgery for endometriosis were included.

INTERVENTIONS

Treatment with GnRH analogues every 28 days, 3 doses. Under their effect, one or two transvaginal US-guided punctures were performed in order to aspirate the endometriomas, and 3 million IU of rIL-2 were left in the aspirated cysts each time.

MAIN OUTCOME MEASURES

CLINICAL RESULTS

two menstruations after GnRH analogues. Other secondary outcome measures were: the time until recurrence of cysts, symptoms and CA-125 >35 U/ml, and the need for further medical or surgical treatment.

RESULTS

They were moderate or good in >50% of cases with one drainage and one dose of 3 million IU of rIL-2 intracyst, but were better with a second drainage and two doses of rIL-2 (25 vs. 58.3% 'good results'). There were fewer recurrences and the interval before recurrence was longer after two doses but differences were not significant. Six patients from group I (50%) and 3 from group II (25%) needed laparotomy and conservative surgery at 17.5 +/- 8.7 months (total time of follow-up = 33 +/- 8.8 months).

CONCLUSIONS

Treatment of endometriomas with transvaginal US-guided drainage and rIL-2 left in the cysts under endometrial suppressive therapy with GnRH analogues has beneficial effects, improving clinical manifestations and avoiding some surgical therapies. The use of a higher dose of rIL-2 does not produce better results, whereas drainage + rIL-2 twice does.

Association between polymorphisms in the progesterone receptor gene and endometriosis

The progesterone receptor (PR) is a candidate gene for the development of endometriosis, a complex disease with strong hormonal features, common in women of reproductive age. We typed the 306 base pair Alu insertion (AluIns) polymorphism in intron G of PR in 101 individuals, estimated linkage disequilibrium (LD) between five single-nucleotide polymorphisms (SNPs) across the PR locus in 980 Australian triads (endometriosis case and two parents) and used transmission disequilibrium testing (TDT) for association with endometriosis. The five SNPs showed strong pairwise LD, and the AluIns was highly correlated with proximal SNPs rs1042839 (delta2 = 0.877, D9 = 1.00, P < 0.0001) and rs500760 (delta2 = 0.438, D9 = 0.942, P < 0.0001). TDT showed weak evidence of allelic association between endometriosis and rs500760 (P = 0.027) but not in the expected direction. We identified a common susceptibility haplotype GGGCA across the five SNPs (P = 0.0167) in the whole sample, but likelihood ratio testing of haplotype transmission and non-transmission of the AluIns and flanking SNPs showed no significant pattern. Further, analysis of our results pooled with those from two previous studies suggested that neither the T2 allele of the AluIns nor the T1/T2 genotype was associated with endometriosis.

Reduced progesterone action during endometrial maturation: a potential risk factor for the development of endometriosis

OBJECTIVE

To discuss the role that reduced endometrial responsiveness to progesterone (P) might play in the pathophysiology of endometriosis.

DESIGN

A review of experimental evidence regarding the failure of P to regulate the expression of matrix metalloproteinases (MMPs) in the endometrium of patients with endometriosis.

CONCLUSION(S)

Progesterone and locally produced differentiation factors act cooperatively to reduce MMP expression by maternal endometrial cells within the pro-inflammatory micro-environment of early pregnancy. Our in vitro studies with normal human endometrium demonstrate that prior P exposure not only down-regulates MMP expression, but also limits the ability of locally produced proinflammatory cytokines to stimulate expression of these enzymes. In contrast, endometrial tissues from women with endometriosis demonstrate an altered response to P, allowing a continuous expression of MMPs throughout the secretory phase. Although the factors that influence the loss of P sensitivity in the endometrium of patients with endometriosis have not yet been defined, alterations in cell-cell communication seem to contribute to dysregulated MMP expression. Specifically, proinflammatory cytokines produced by epithelial cells oppose stromal cell responses to P, inhibiting production of key differentiation factors necessary for cell-specific MMP regulation. The resulting loss in normal MMP regulation enhances the invasive capacity of endometrial tissue, promoting ectopic establishment in an experimental model.

Intestinal endometriosis: the great masquerader

Chronic symptoms of abdominal pain and irregular bowel habits in women evoke a broad differential diagnosis including irritable bowel syndrome, infection, malabsorption, and inflammatory bowel disease. Endometriosis, a common disorder in young women that can involve the intestinal tract, deserves consideration as well. Intestinal endometriosis is typically asymptomatic; however, when symptoms occur, they can mimic those of irritable bowel syndrome. Identifying intestinal endometriosis can be challenging, but historical points and key clinical features aid in diagnosis.