The pains of endometriosis

Pelvic pain and surgeries in women before interstitial cystitis/painful bladder syndrome

OBJECTIVE

The objective of the study was to compare subjects with interstitial cystitis/painful bladder syndrome (IC/PBS) with controls on prior surgeries.

STUDY DESIGN

IC/PBS subjects were compared with matched controls on surgeries and possible surgical indications prior to their index dates.

RESULTS

Adjusted for demographic variables, logistic regression showed subjects exceeded controls in surgeries longer than 12 months and less than 1 month before the index date. However, addition of possible surgical indications showed chronic pelvic pain (CPP) to have a strong association with IC/PBS, whereas associations with surgeries were reduced to nonsignificance.

CONCLUSION

Although women with IC/PBS were more likely to have experienced prior surgeries than controls, the apparent indications for surgeries, not the surgeries themselves, were stronger risk factors for IC/PBS. In particular, a prior history of CPP had a strong association with IC/PBS. Several features of study design, including extensive medical record review, suggest that prior CPP was not undiagnosed IC/PBS. Further investigation of CPP may yield insight into the pathogenesis of IC/PBS.

The protein kinase A pathway-regulated transcriptome of endometrial stromal fibroblasts reveals compromised differentiation and persistent proliferative potential in endometriosis

Intrinsic abnormalities in transplanted eutopic endometrium are believed to contribute to the pathogenesis of pelvic endometriosis. Herein we investigated transcriptomic differences in human endometrial stromal fibroblasts (hESFs) from women with (hESF(endo)) vs. without (hESF(nonendo)) endometriosis, in response to activation of the protein kinase A (PKA) pathway with 8-bromoadenosine-cAMP (8-Br-cAMP). hESF(nonendo) (n = 4) and hESF(endo) (n = 4) were isolated from eutopic endometrium and treated +/- 0.5 mm 8-Br-cAMP for 96 h. Purified total RNA was subjected to microarray analysis using the whole-genome Gene 1.0 ST Affymetrix platform. A total of 691 genes were regulated in cAMP-treated hESF(nonendo) vs. 158 genes in hESF(endo), suggesting a blunted response to cAMP/PKA pathway activation in women with disease. Real-time PCR and ELISA validated the decreased expression of decidualization markers in hESF(endo) compared with hESF(nonendo). In the absence of disease, 8-Br-cAMP down-regulated progression through the cell cycle via a decrease in cyclin D1, cyclin-dependent kinase 6, and cell division cycle 2 and an increase in cyclin-dependent kinase inhibitor 1A. However, cell cycle components in hESF(endo) were not responsive to 8-Br-cAMP, resulting in persistence of a proliferative phenotype. hESF(endo) treated with 8-Br-cAMP exhibited altered expression of immune response, extracellular matrix, cytoskeleton, and apoptosis genes. Changes in phosphodiesterase expression and activity were not different among experimental groups. These data support that eutopic hESF(endo) with increased proliferative potential can seed the pelvic cavity via retrograde menstruation and promote establishment, survival, and proliferation of endometriosis lesions, independent of hydrolysis of cAMP and likely due to an inherent abnormality in the PKA pathway.

Visceral organ cross-sensitization - an integrated perspective

Viscero-somatic referral and sensitization has been well documented clinically and widely investigated, whereas viscero-visceral referral and sensitization (termed cross-organ sensitization) has only recently received attention as important to visceral disease states. Because second order neurons in the CNS have been extensively shown to receive convergent input from different visceral organs, it has been assumed that cross-organ sensitization arises by the same convergence-projection mechanism as advanced for viscero-somatic referral and sensitization. However, increasing evidence also suggests participation of peripheral mechanisms to explain referral and sensitization. We briefly summarize behavioral, morphological and physiological support of and focus on potential mechanisms underlying cross-organ sensitization.

Endometriosis-associated ovarian cancer: A ten-year cohort study of women living in the Estrie Region of Quebec, Canada

Objectives

Endometriosis has been believed to increase the risk of developing ovarian cancer, but recent data supporting this hypothesis are lacking. The aim of this study was to verify whether the incidence of endometriosis, ovarian cancer and the both increased during the last 10 years among women living in the Estrie region of Quebec.

Methods

We collected data of women diagnosed with endometriosis, ovarian cancer or both, between 1997 and 2006, from a population living in the Estrie region of Quebec. We performed this retrospective cross-sectional study from the CIRESSS (Centre Informatisé de Recherche Évaluative en Services et Soins de Santé) system, the database of the CHUS (Centre Hospitalier Universitaire of Sherbrooke), Sherbrooke, Canada.

Results

Among the 2854 identified patients, 2521 had endometriosis, 292 patients had ovarian cancer and 41 patients had both ovarian cancer and endometriosis. We showed a constant increase in the number of ovarian cancer (OC) between 1997 and 2006 (r² = 0.557, P = 0.013), which is not the case for endometriosis (ENDO) or endometriosis-associated ovarian cancer (EAOC). The mean age ± SD was 40.0 ± 9.9 and 53.9 ± 11.4 for patients having ENDO and OC, respectively. Mean age of women with EAOC was 48.3 ± 10.8, suggesting an early onset of ovarian cancer in women having endometriosis of about 5.5 years average, P = 0.003. Women with ENDO were at increased risk for developing OC (Rate Ratio [RR] = 1.6; 95% Confidence Interval [CI] = 1.12-2.09). Pathological analyses showed the predominance of endometrioid type (24.4%) and clear-cell type (21.9%) types in EAOC compared to OC, P = 0.0070 and 0.0029, respectively. However, the serous type is the most widespread in OC (44.5%) in comparison to EAOC (19.51%), P = 0.0023.

Conclusion

Our findings highlight that the number of cases of ovarian cancer is constantly increasing in the last ten years and that endometriosis represents a serious risk factor which accelerates its apparition by about 5.5 years.

Allodynia in migraine: association with comorbid pain conditions

BACKGROUND

Cutaneous allodynia (CA) in migraine is a clinical manifestation of central nervous system sensitization. Several chronic pain syndromes and mood disorders are comorbid with migraine. In this study we examine the relationship of migraine-associated CA with these comorbid conditions. We also evaluate the association of CA with factors such as demographic profiles, migraine characteristics, and smoking status that may have an influence on the relationships of CA to pain and mood.

METHODS

Data are from a cross-sectional multicenter study of comorbid conditions in persons seeking treatment in headache clinics. Diagnosis of migraine was determined by a physician based on the International Classification of Headache Disorders-II criteria. Participants completed a self-administered questionnaire ascertaining sociodemographics, migraine-associated allodynia, physician-diagnosed comorbid medical and psychiatric disorders, headache-related disability, current depression, and anxiety.

RESULTS

A total of 1413 migraineurs (mean age = 42 years, 89% women) from 11 different headache treatment centers completed a survey on the prevalence of comorbid conditions. Aura was reported by 38% and chronic headache by 35% of the participants. Sixty percent of the study population reported at least one migraine-related allodynic symptom, 10% reported > or =4 symptoms. Symptoms of CA were associated with female gender, body mass index, current smoking, presence of aura, chronic headaches, transformed headaches, severe headache-related disability, and duration of migraine illness from onset. The prevalence of self-reported physician diagnosis of comorbid pain conditions (irritable bowel syndrome, chronic fatigue syndrome, fibromyalgia) and psychiatric conditions (current depression and anxiety) was also associated with symptoms of CA. Adjusted ordinal regression indicated a significant association between number of pain conditions and severity of CA (based on symptom count). Adjusting for sociodemographics, migraine characteristics, and current depression and anxiety, the likelihood of reporting symptoms of severe allodynia was much higher in those with 3 or more pain conditions (odds ratio = 3.03, 95% confidence interval: 1.78-5.17), and 2 pain conditions (odds ratio = 2.67, 95% confidence interval: 1.78-4.01) when compared with those with no comorbid pain condition.

CONCLUSION

Symptoms of CA in migraine were associated with current anxiety, depression, and several chronic pain conditions. A graded relationship was observed between number of allodynic symptoms and the number of pain conditions, even after adjusting for confounding factors. This study also presents the novel association of CA symptoms with younger age of migraine onset, and with cigarette smoking, in addition to confirming several previously reported findings.

Endometriosis and mechanisms of pelvic pain

Endometriosis remains an enigmatic disorder in that the cause, the natural history, and the precise mechanisms by which it causes pain are not completely understood. The pain symptoms most commonly attributed to endometriosis are dysmenorrhea, dyspareunia, and chronic pelvic pain. Pain may be due to nociceptive, inflammatory, or neuropathic mechanisms, and there is evidence that all 3 of these mechanisms are relevant to endometriosis-associated pelvic pain. It is proposed that the clinically observed inconsistencies of the relationships of endometriosis severity and the presence or severity of pain are likely due to variable roles of different pain mechanisms in endometriosis. A better understanding of the roles of nociceptive, inflammatory, and neuropathic pain in endometriosis is likely to improve the treatment of women with endometriosis-associated pelvic pain.

Nerve fibres in ovarian endometriotic lesions in women with ovarian endometriosis

BACKGROUND

Although nerve fibres are present in eutopic and ectopic endometrium, it is unclear whether they appear in ovarian endometriotic lesions. We investigated the presence of nerve fibres in ovarian endometriotic lesions and its correlation with clinical parameters in women with ovarian endometriosis.

METHODS

Histological sections of ovarian endometriotic lesions from 61 women with ovarian endometriosis (Stages II-IV) who underwent laparoscopic endometrioma cystectomy were stained immunohistochemically using a specific polyclonal rabbit anti-protein gene product 9.5 (PGP9.5) antibody to demonstrate myelinated and unmyelinated nerve fibres.

RESULTS

Nerve fibres stained with PGP9.5 were detected in ovarian endometriotic lesions in 31.1% of women, and most appeared in fibrotic interstitium of ovarian endometriotic lesions. The density of PGP9.5-immunoactive fibres in ovarian endometriotic lesions in women with pain symptoms (n = 35) was higher than in women with no pain symptoms (n = 26, P = 0.039), although the percentage (positive cases/total) of PGP9.5-positive fibres did not differ. In women with pain symptoms, PGP9.5-positive fibres appeared in 40.0% of cases and the density of PGP9.5-immunoactive fibres in ovarian endometriotic lesions was correlated with severity of pain symptoms (r = 0.466, P = 0.005). In women with no pain, PGP9.5-positive fibres were detected in only 5 (19.2%) women. Both the percentage and the density of PGP9.5-positive fibres in ovarian endometriotic lesions were associated with pelvic adhesions (chi2 = 6.833, P = 0.009; Z = 2.442, P = 0.015, respectively) but not with disease severity.

CONCLUSIONS

PGP9.5-immunoactive nerve fibres in ovarian endometriotic lesions may be involved in the pathophysiology of pain generation and pelvic adhesion formation in women with ovarian endometriosis.

Effect of peritoneal fluid from endometriosis patients on neuroblastoma cells in culture

AIM

Endometriosis is often associated with lower abdominal pain, dysmenorrhea, dyspareunia, and chronic pelvic pain. There is no correlation between the extent of endometriosis and the intensity of pain. The mechanism of pain in endometriosis is unknown. The aim of our study was to investigate the influence of peritoneal fluid (PF) from endometriosis patients on cultured neural cells that are the morphological basis of nociception, and to determine whether there was a relationship between the rAFS staging and an elevation of TGF-beta1 production by these cells.

METHODS

Different human neuroblastoma cell lines were grown to 3/4 confluence and then cultured in presence of PF pooled according to the presence of no, mild, or severe endometriosis. After 6 and 24 h of incubation, the morphological changes were assessed and the metabolic activity was determined.

RESULTS

The different cell lines showed strongly varying proliferation and aggregation patterns. The metabolic activity was also varying between cell lines, but no consistently increased cell turnover in the PF when compared with the control medium nor associated to a particular, endometriosis-derived PF pool could be shown. In this experimental setting, we have observed that the cell proliferation in the presence of PF was inhibited, and not enhanced as it might have been expected. Measurement of TGF-beta1 showed higher production rates for this cytokine under exposure to PF than in controls for some but not all tested cell lines, but there was no association with the stage (rAFS) of the disease.

CONCLUSION

The neuronal cell culture model may become a useful tool to investigate the endometriosis-derived pain, but different endpoints and cell lines may have to be introduced.

Neurokinin 1 receptor gene polymorphism might be correlated with recurrence rates in endometriosis

INTRODUCTION

Dysmenorrhoea is the major symptom in women with endometriosis. Recently, pain modulation through Neurokinin-1-receptor (NK1R) pathways have been investigated in neuropathic pain patients. Aim of this study was, therefore, to examine the effect of a single nucleotide polymorphism (SNP) of the NK1R gene on the susceptibility for endometriosis and the disease free survival (DFS) after surgery for endometriosis.

MATERIAL AND METHODS

A case-control study was conducted and germline DNA was isolated. Patients were followed up for a recurrence of the disease up to 4 years. Case-control analyses were performed for parameters of the medical history and the genotype of the NK1R-SNP rs881. Furthermore, DFS probabilities were calculated.

RESULTS

Concerning the DFS preoperative pain levels and the NK1R genotype were independent predictors for a recurrence with hazard ratios of 2.55 (95% CI: 1.32-4.95) for patients with a high preoperative pain level and 0.44 for patients with a heterozygous or homozygous variant genotype in rs881 (95% CI: 0.21-0.88).

CONCLUSION

The polymorphism rs811 seems to be associated with a lower recurrence risk in endometriosis patients. Thus, there might be a clinical relevant role of the NK1 pathway in the pain perception of endometriosis patients.

Endometriosis-induced vaginal hyperalgesia in the rat: role of the ectopic growths and their innervation

Endometriosis is a painful disorder defined by extrauteral endometrial growths whose contribution to pain symptoms is poorly understood. Endometriosis is created in rats by autotransplanting on abdominal arteries pieces of either uterus (ENDO), which form cysts, or fat (shamENDO), which do not form cysts. ENDO, but not shamENDO induces vaginal hyperalgesia. We tested the hypothesis that the cysts are necessary to maintain vaginal hyperalgesia by assessing the effect of surgically removing them. Complete-cyst-removal eliminated ENDO-induced vaginal hyperalgesia up to 4 months post-operatively. Sham-cyst-removal in ENDO rats, in which cysts were not removed, or partial cyst-removal increased the ENDO-induced hyperalgesia. The decreases and increases both took 3-6 weeks to develop. Changes in ENDO-induced hyperalgesia did not occur in a control group of ENDO rats who had no surgery after ENDO. In a double-surgery control group, neither shamENDO surgery nor a subsequent sham surgery that mimicked "removal" of non-existent cysts influenced vaginal nociception. In a no-surgery control group, vaginal nociception remained stable for >6 months. The increases in ENDO-induced hyperalgesia produced by the sham-cyst-removal surgery were smaller in proestrus than in other estrous stages. During the other stages (but not during proestrus), sympathetic innervation of the cysts increased. These results suggest that maintenance of ENDO-induced vaginal hyperalgesia requires continued presence of at least some ectopic endometrial tissue, and that surgical treatment that fails to remove ectopic endometrial tissue can exacerbate the hyperalgesia, possibly due in part to an increase in the cysts' sympathetic innervation.

Estrogen metabolism and action in endometriosis

Endometriosis is a complex estrogen-dependent disease that is defined as the presence of endometrial glands and stroma outside the uterine cavity. The etiology of endometriosis is multifactorial and includes complex interactions of genetic, immunological, hormonal and environmental factors. Many theories have been proposed, but no single theory can explain all aspects of endometriosis, suggesting that endometriosis is a heterogeneous disease. This review presents the current theories on the pathogenesis of endometriosis, followed by an overview on estrogen metabolism in normal endometrium and diseased endometrium of endometriosis patients. The potential role of aberrant expression of individual estrogen-metabolizing enzymes is discussed, and a model mechanism for increased formation of estradiol is presented separately for different types of endometriosis. The disturbed expression of estrogen receptors in endometriosis is detailed, and the estrogen biosynthetic enzymes and receptors are discussed as novel therapeutic targets for the treatment of endometriosis.

Macrophages are alternatively activated in patients with endometriosis and required for growth and vascularization of lesions in a mouse model of disease

The mechanisms that sustain endometrial tissues at ectopic sites in patients with endometriosis are poorly understood. Various leukocytes, including macrophages, infiltrate endometriotic lesions. In this study, we depleted mouse macrophages by means of either clodronate liposomes or monoclonal antibodies before the injection of syngeneic endometrial tissue. In the absence of macrophages, tissue fragments adhered and implanted into the peritoneal wall, but endometriotic lesions failed to organize and develop. When we depleted macrophages after the establishment of endometriotic lesions, blood vessels failed to reach the inner layers of the lesions, which stopped growing. Macrophages from patients with endometriosis and experimental mice, but not nonendometriotic patients who underwent surgery for uterine leiomyomas or control mice, expressed markers of alternative activation. These markers included high levels of scavenger receptors, CD163 and CD206, which are involved in both the scavenging of hemoglobin with iron transfer into macrophages and the silent clearance of inflammatory molecules. Macrophages in both inflammatory liquid and ectopic lesions were equally polarized, suggesting a critical role of environmental cues in the peritoneal cavity. Adoptively transferred, alternatively activated macrophages dramatically enhanced endometriotic lesion growth in mice. Inflammatory macrophages effectively protected mice from endometriosis. Therefore, endogenous macrophages involved in tissue remodeling appear as players in the natural history of endometriosis, required for effective vascularization and ectopic lesion growth.

Estrogen-dependent changes in visceral afferent sensitivity

Many forms of chronic pain are more prevalent in women and this is interpreted as the consequence of a direct role of estrogens in the modulation of pain perception. Some functional pain states, i.e. those without a clear and demonstrable pathology, are also more prevalent in women and the pain in these conditions is also modulated by hormonal variations during the menstrual cycle. Increased pain sensitivity is commonly interpreted as the consequence of peripheral or central hyperexcitability of nociceptive pathways. Therefore a role has been suggested for estrogen in the modulation of the excitability of nociceptive afferents and central neurons. The literature on the sign of this modulation is not uniform, with reports pointing to estrogen as either pro- or anti-nociceptive. In our hands, a permanent reduction in the levels of estrogen, such as that induced by surgical ovariectomy (OVX) generates a hyperalgesic state of slow onset and long duration that can be prevented or reversed by exogenous administration of estrogen. The hyperalgesia is characterized by mechanical and thermal hyperalgesia in the abdominal and pelvic regions as well as by visceral hypersensitivity. The possible role of estrogen in the prevention of chronic painful states is discussed.

Common genetic influences underlie comorbidity of migraine and endometriosis

We examined the co-occurrence of migraine and endometriosis within the largest known collection of families containing multiple women with surgically confirmed endometriosis and in an independent sample of 815 monozygotic and 457 dizygotic female twin pairs. Within the endometriosis families, a significantly increased risk of migrainous headache was observed in women with endometriosis compared to women without endometriosis (odds ratio [OR] 1.57, 95% confidence interval [CI]: 1.12-2.21, P=0.009). Bivariate heritability analyses indicated no evidence for common environmental factors influencing either migraine or endometriosis but significant genetic components for both traits, with heritability estimates of 69 and 49%, respectively. Importantly, a significant additive genetic correlation (r(G) = 0.27, 95% CI: 0.06-0.47) and bivariate heritability (h(2)=0.17, 95% CI: 0.08-0.27) was observed between migraine and endometriosis. Controlling for the personality trait neuroticism made little impact on this association. These results confirm the previously reported comorbidity between migraine and endometriosis and indicate common genetic influences completely explain their co-occurrence within individuals. Given pharmacological treatments for endometriosis typically target hormonal pathways and a number of findings provide support for a relationship between hormonal variations and migraine, hormone-related genes and pathways are highly plausible candidates for both migraine and endometriosis. Therefore, taking into account the status of both migraine and endometriosis may provide a novel opportunity to identify the genes underlying them. Finally, we propose that the analysis of such genetically correlated comorbid traits can increase power to detect genetic risk loci through the use of more specific, homogenous and heritable phenotypes.

Disturbed estrogen and progesterone action in ovarian endometriosis

Endometriosis is a very common disease in pre-menopausal women, where defective metabolism of steroid hormones plays an important role in its development and promotion. In the present study, we have examined the expression of 11 estrogen and progesterone metabolizing enzymes and their corresponding receptors in samples of ovarian endometriomas and control endometrium. Expression analysis revealed significant up-regulation of enzymes involved in estradiol formation (aromatase, sulfatase and all reductive 17beta-hydroxysteroid dehydrogenases) and in progesterone inactivation (AKR1C1 and AKR1C3). Among the estrogen and progesterone receptors, ERalpha was down-regulated, ERbeta was up-regulated, and there was no significant difference in expression of progesterone receptors A and B (PRAB). Our data indicate that several enzymes of estrogen and progesterone metabolism are aberrantly expressed in endometriosis, which can lead to increased local levels of mitogenic estradiol and decreased levels of protective progesterone. Changes in estrogen receptor expression suggest that estradiol may also act via non-estrogen receptor-mediated pathways, while expression of progesterone receptors still needs further investigation.

Dysmenorrhea: risk factors in women with endometriosis

Although it is generally accepted that endometriosis is responsible for dysmenorrhea, as well as other symptoms such as infertility, the precise relationship between the severity of dysmenorrhea and various characteristics of disease, such as stage and the type or site of endometriotic lesions, has been elusive and often a matter of heated debate, owing largely to conflicting reports. Here we review factors that are reported to be associated with dysmenorrhea in endometriosis. We also demonstrate, through a real example, that different statistical models employed in data analyses may yield somewhat different sets of risk factors, and the difference may not be always resolved within the same data set. In addition, we make the point that despite the best-fitting models, there may still be a sizable portion of variation in the severity of dysmenorrhea that can not be explained completely by the identified risk factors, suggesting that factors other than those of surgical findings or patient characteristics may also be responsible for dysmenorrhea severity. We review some possible factors that may also be responsible for the risk and severity of dysmenorrhea. Finally, we expose areas in need of further research.

Dyschezia and posterior deep infiltrating endometriosis: analysis of 360 cases

STUDY OBJECTIVE

To evaluate the relationship between anatomic locations and diameter of endometriotic lesions with severity of perimenstrual dyschezia (pain with defecation) as a possible location-indicating pain symptom for posterior deep infiltrating endometriosis (DIE).

DESIGN

Retrospective analysis (Canadian Task Force classification II-3).

SETTING

Tertiary care university hospital.

PATIENTS

We reviewed hospital records of patients who underwent laparoscopic treatment for pelvic endometriosis in our center between 2001 and 2006. In all, 360 patients with posterior DIE (endometrial glands and stroma infiltrated excised tissues of the specified organs) were included for whom preoperative scoring of perimenstrual dyschezia was performed using a 10-point visual analog scale (VAS). Data about anatomic location and diameter of excised nodules were retrieved from operative and pathological records.

INTERVENTIONS

Laparoscopic excision of suspected endometriotic lesions.

MEASUREMENTS AND MAIN RESULTS

Mean VAS score of dyschezia for patients with overall posterior DIE was 3.9 +/- 3.8, whereas in unaffected patients it was 1.9 +/- 3.3 (Mann-Whitney test p <.0005). Rectovaginal involvement (posterior vaginal wall, rectovaginal septum, and anterior rectal wall) was found in 240 of 360 women. Mean VAS score for dyschezia was 4.1 +/- 4 and 2.1 +/- 3.3 in affected and nonaffected patients, respectively (p <.0005). Mean lesion diameter in affected patients was significantly correlated with mean VAS score (Spearman rho = 0.21). Patients with anterior rectal wall endometriosis (71/240) had a mean VAS score of 4.2 +/- 4 and in nonaffected patients it was 2.7 +/- 3.6 (p <.05). Mean lesion diameter in affected patients was not significantly correlated with mean VAS score of dyschezia (Spearman rho = 0.16).

CONCLUSION

Severity of dyschezia was significantly correlated with posterior DIE. A positive correlation occurred between severity of dyschezia and lesion diameter with rectovaginal endometriosis but not with anterior rectal wall involvement.

Rich innervation of deep infiltrating endometriosis

BACKGROUND

Deep infiltrating endometriosis (DIE) is a specific type of endometriosis, which can be associated with more severe pelvic pain than other forms of endometriotic lesions. However, the mechanisms by which pain is generated are not well understood.

METHODS

DIE (n = 31) and peritoneal endometriotic (n = 40) lesions were sectioned and stained immunohistochemically with antibodies against protein gene product 9.5, neurofilament, nerve growth factor (NGF), NGF receptors tyrosine kinase receptor-A (Trk-A) and p75, substance P, calcitonin gene-related peptide, vesicular acetylcholine transporter, neuropeptide Y, vasoactive intestinal peptide and tyrosine hydroxylase to demonstrate myelinated, unmyelinated, sensory and autonomic nerve fibres.

RESULTS

There were significantly more nerve fibres in DIE (67.6 +/- 65.1/mm(2)) than in peritoneal endometriotic lesions (16.3 +/- 10.0/mm(2)) (P < 0.01). DIE was innervated abundantly by sensory Adelta, sensory C, cholinergic and adrenergic nerve fibres; NGF, Trk-A and p75 were strongly expressed in endometriotic glands and stroma of DIE.

CONCLUSIONS

The rich innervation of DIE may help to explain why patients with this type of lesion have severe pelvic pain.

Effects of surgical induction of endometriosis on response properties of preoptic area neurons in rats

Subfertility and severe pelvic pains are symptoms associated with endometriosis (ENDO), a common condition among women that is characterized by the growth of the uterine endometrium on the surface of organs within the pelvic region and abdominal cavity. The contribution of the CNS to symptoms associated with ENDO is not known. In the present study, the preoptic area (POA) of the hypothalamus was investigated, as this region of the forebrain is known to play an important role in the neuroendocrine control of the reproductive cycle, mating behavior, and antinociception. Female rats were either induced for ENDO by autotransplantation of uterine tissue (n=20) or uterine fat for surgical sham controls (n=11). Terminal extracellular electrophysiological recordings (urethane anesthesia) were conducted in the POA six weeks post-ENDO induction when the rats were in either the proestrus or metestrus stages of their estrous cycle. Significant differences were found between the ENDO versus SHAM groups of animals for the proportion of inhibitory responses as well as the percentage of neurons responding to stimulation of the abdominal branches of the vagus, which innervates portions of the female reproductive tract, including the ovaries. The endometriotic cysts were found to be significantly larger in proestrus rats (stage when hormones are elevated). These data demonstrate that the responses of POA neurons are influenced by the presence of endometriotic cysts in the abdominal cavity. Since the POA is known to be part of the neural circuitries that mediate nociception and fertility, any deviation from its normal activity under ENDO conditions could contribute to the constellation of symptoms that ensue.

A pilot study to evaluate the clinical relevance of endometriosis-associated nerve fibers in peritoneal endometriotic lesions

OBJECTIVE

To investigate the clinical relevance of endometriosis-associated nerve fibers in the development of endometriosis-associated symptoms.

DESIGN

Prospective nonrandomized study.

SETTING

University hospital endometriosis center.

PATIENT(S)

Fifty-one premenopausal patients underwent surgical laparoscopy because of chronic pelvic pain, dysmenorrhea, or for ovarian cysts. Endometriosis was diagnosed in 44 patients.

INTERVENTION(S)

The preoperative and postoperative pain scores were determined using a standardized questionnaire with a visual analogue scale from 1-10. Patients with peritoneal endometriosis were divided into two groups depending on their preoperative pain score: group A with a pain score of at least 3 or more and group B with a pain score of 2 or less. Patients without peritoneal endometriosis were classified as group C and patients without endometriosis were classified as group D. Immunohistochemical analysis of neurofilament and protein gene product 9.5 were used for nerve fiber detection. Occurrence of endometriosis-associated nerve fibers was correlated with the severity of pelvic pain and/or dysmenorrhea.

RESULT(S)

Peritoneal endometriosis-associated nerve fibers were found significantly more frequently in group A than in group B (82.6% vs. 33.3%).

CONCLUSION(S)

The present study suggests that the presence of endometriosis-associated nerve fibers in the peritoneum is important for the development of endometriosis-associated pelvic pain and dysmenorrhea.

Pain scoring in endometriosis: entry criteria and outcome measures for clinical trials. Report from the Art and Science of Endometriosis meeting

Standardized entry criteria and outcome measures for clinical trials in endometriosis-related pain would facilitate the comparison of trial results and the production of systematic reviews, improving evidence-based practice in this area. This report summarizes the recommendations from an international meeting for these criteria.

The search for genes contributing to endometriosis risk

BACKGROUND

Genetic variation contributes to the risk of developing endometriosis. This review summarizes gene mapping studies in endometriosis and the prospects of finding gene pathways contributing to disease using the latest genome-wide strategies.

METHODS

To identify candidate-gene association studies of endometriosis, a systematic literature search was conducted in PubMed of publications up to 1 April 2008, using the search terms 'endometriosis' plus 'allele' or 'polymorphism' or 'gene'. Papers included were those with information on both case and control selection, showed allelic and/or genotypic results for named germ-line polymorphisms and were published in the English language.

RESULTS

Genetic variants in 76 genes have been examined for association, but none shows convincing evidence of replication in multiple studies. There is evidence for genetic linkage to chromosomes 7 and 10, but the genes (or variants) in these regions contributing to disease risk have yet to be identified. Genome-wide association is a powerful method that has been successful in locating genetic variants contributing to a range of common diseases. Several groups are planning these studies in endometriosis. For this to be successful, the endometriosis research community must work together to genotype sufficient cases, using clearly defined disease classifications, and conduct the necessary replication studies in several thousands of cases and controls.

CONCLUSIONS

Genes with convincing evidence for association with endometriosis are likely to be identified in large genome-wide studies. This will provide a starting point for functional and biological studies to develop better diagnosis and treatment for this debilitating disease.

Is There a Role for Acupuncture in Endometriosis Pain, Or ‘endometrialgia’?

Endometriosis is a common cause of pelvic pain in women, many of whom suffer a progression of symptoms over their menstrual life. Symptoms may include combinations of abnormal visceral sensations and emotional distress. Endometriosis pain, or ‘endometrialgia’ often has a negative influence on the ability to work, on family relationships and sense of worth.

Endometrialgia is often considered to be a homogeneous sensory entity, mediated by a specialised high threshold sensory system, which extends from the periphery through the spinal cord, brain stem and thalamus to the cerebral cortex. However, multiple mechanisms have been detected in the nervous system responsible for the pain including peripheral sensitisation, phenotypic switches, central sensitisation, ectopic excitability, structural reorganisation, decreased inhibition and increased facilitation, all of which may contribute to the pain.

Although the causes of endometrialgia can differ (eg inflammatory, neuropathic and functional), they share some characteristics. Endometrialgia may be evoked by a low intensity, normally innocuous stimulus (allodynia), or it may be an exaggerated and prolonged response to a noxious stimulus (hyperalgesia). The pain may also be spontaneous in the absence of any apparent peripheral stimulus.

Oestrogens and prostaglandins probably play key modulatory roles in endometriosis and endometrialgia. Consequently many of the current medical treatments for the condition include oral drugs, like non-steroid anti-inflammatory drugs, contraceptives, progestogens, androgenic agents, gonadotrophin releasing hormone analogues, as well as laparoscopic surgical excision of the endometriosis lesions. However, management of pain in women with endometriosis is currently inadequate for many. Possibly acupuncture and cognitive therapy may be used as an adjunct.

Mast cell-derived histamine mediates cystitis pain

Background

Mast cells trigger inflammation that is associated with local pain, but the mechanisms mediating pain are unclear. Interstitial cystitis (IC) is a bladder disease that causes debilitating pelvic pain of unknown origin and without consistent inflammation, but IC symptoms correlate with elevated bladder lamina propria mast cell counts. We hypothesized that mast cells mediate pelvic pain directly and examined pain behavior using a murine model that recapitulates key aspects of IC.

Methods and Findings

Infection of mice with pseudorabies virus (PRV) induces a neurogenic cystitis associated with lamina propria mast cell accumulation dependent upon tumor necrosis factor alpha (TNF), TNF-mediated bladder barrier dysfunction, and pelvic pain behavior, but the molecular basis for pelvic pain is unknown. In this study, both PRV-induced pelvic pain and bladder pathophysiology were abrogated in mast cell-deficient mice but were restored by reconstitution with wild type bone marrow. Pelvic pain developed normally in TNF- and TNF receptor-deficient mice, while bladder pathophysiology was abrogated. Conversely, genetic or pharmacologic disruption of histamine receptor H1R or H2R attenuated pelvic pain without altering pathophysiology.

Conclusions

These data demonstrate that mast cells promote cystitis pain and bladder pathophysiology through the separable actions of histamine and TNF, respectively. Therefore, pain is independent of pathology and inflammation, and histamine receptors represent direct therapeutic targets for pain in IC and other chronic pain conditions.

Experimental autoimmune prostatitis induces chronic pelvic pain

Pain is the hallmark of patients with chronic prostatitis (CP) and chronic pelvic pain syndrome (CPPS). Despite numerous hypotheses, the etiology and pathogenesis remain unknown. To better understand CP/CPPS, we used a murine experimental autoimmune prostatitis model to examine the development, localization, and modulation of pelvic pain. Pelvic pain was detected 5 days after antigen instillation and was sustained beyond 30 days, indicating the development of chronic pain. The pain was attenuated by lidocaine treatment into the prostate, but not into the bladder or the colon, suggesting that pain originated from the prostate. Experimental autoimmune prostatitis histopathology was confined to the prostate with focal periglandular inflammatory infiltrates in the ventral, dorsolateral, and anterior lobes of the mouse prostate. Inflammation and pelvic pain were positively correlated and increased with time. Morphologically, the dorsolateral prostate alone showed significantly increased neuronal fiber distribution, as evidenced by increased protein gene product 9.5 expression. Pelvic pain was attenuated by treatment with the neuromodulator gabapentin, suggesting spinal and/or supraspinal contribution to chronic pain. These results provide the basis for identifying mechanisms that regulate pelvic pain and the testing of therapeutic agents that block pain development in CP/CPPS.

Experimental endometriosis in the rat is correlated with colonic motor function alterations but not with bacterial load

Endometriosis commonly presents with symptoms that mimic chronic gastrointestinal disorders. The authors used the autotransplantion model of endometriosis in rats to investigate the possible underlying mechanisms. After the rats were killed, the presence of endometriotic vesicles, colonic inflammation, and white blood cell (WBC) numbers in the peritoneal fluid was determined. Sections of colon and of jejunum were collected for measurement of myeloperoxidase (MPO) activity and bacterial counts, and isometric recording in response to acetylcholine was measured in segments of longitudinal and circular smooth muscle. Experimental animals had significantly more colonic damage, MPO activity, and WBC numbers than controls did. There was no significant difference in the total bacterial load; however, experimental animals demonstrated an increased tension in the longitudinal muscle, which correlated with WBC numbers and colonic damage. In summary, this study presents evidence for a significant effect of peritoneal endometriosis on colonic function and integrity, which may help explain the gastrointestinal symptoms associated with this disease.

Return of chronic pelvic pain from endometriosis after raloxifene treatment: a randomized controlled trial

OBJECTIVE

To evaluate whether 6 months of raloxifene was effective in treatment of chronic pelvic pain in women with endometriosis.

METHODS

Women with chronic pelvic pain and no endometriosis treatment for 6 months underwent laparoscopy for excision of all lesions. Those with biopsy-proven endometriosis were randomly allocated to raloxifene (180 mg) or placebo daily. A second laparoscopy was performed at 2 years, or earlier, if pain returned. Return of pain was defined as 2 months of pain equal to or more severe than that at study entry. Menstrual cycles and adverse events were recorded. The log rank test was used to compare the time to return of pain by drug group. Analyses were done as intent-to-treat.

RESULTS

A total of 127 of 158 women underwent surgery. Of these, 93 had biopsy-confirmed endometriosis and were randomly assigned to study treatment. Menstrual cycle length, pelvic pain severity, quality of life, bone mineral density, and adverse events did not differ between treatment groups. The Data Safety Monitoring Committee terminated the study early when the raloxifene group experienced pain (P=.03) and had second surgery (P=.016) significantly sooner than the placebo group. Interestingly, biopsy-proven endometriosis was not associated with return of pain (P=.6).

CONCLUSION

Raloxifene significantly shortened the time to return of chronic pelvic pain. Because recurrence of endometriosis lesions did not correlate with return of pain, other factors are implicated in pelvic pain.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.cliicaltrials.gov, NCT00001848

LEVEL OF EVIDENCE

I.

Endometriosis as a neurovascular condition: estrous variations in innervation, vascularization, and growth factor content of ectopic endometrial cysts in the rat

Endometriosis is a poorly understood, estradiol-dependent condition associated with severe pelvic pains and defined by vascularized endometrial growths outside the uterus. Endometriosis is produced in cycling rats by autotransplanting pieces of uterus onto abdominal arteries where they develop into cysts. The surgery induces vaginal and abdominal muscle hyperalgesia, whose severity is greatest in proestrus and nearly absent in estrus. The cysts contain growth factors and cytokines and develop their own sympathetic and sensory C- and Aδ-fiber innervation. Here, we used quantitative immunostaining and protein array analyses to test the hypothesis that the innervation and growth factor/cytokine content of the cysts, but not uterine horn, contribute to proestrous-to-estrous changes in hyperalgesic severity. If so, these characteristics in the cysts, but not the uterine horn, should change with estrous stage. In cysts, the density of sympathetic (but not sensory) neurites and amounts of NGF and VEGF proteins (but not cytokines IL-1, IL-6, IL-10, or TNF-α) were greater in proestrus than estrus. These changes were accompanied by vascular changes. Both sympathetic and sensory fibers in both stages colabeled with TrkA, indicating that changes in NGF could act on both afferent and efferent fibers. In contrast with the cysts, no changes occurred in the uterine horn between proestrus and estrus. Together, these results suggest that coordinated proestrous-to-estrous changes in innervation and vascularization of the cysts contribute to similar changes in hyperalgesic severity. The findings also encourage consideration of endometriosis as a neurovascular condition.

Convergence of nociceptive information in the forebrain of female rats: reproductive organ response variations with stage of estrus

Neurons in the preoptic area (POA) of the hypothalamus and the bed nucleus of stria terminalis (BST) play an important role in the neuroendocrine control of the reproductive cycle, mating behaviors and nociception. Single unit extracellular recordings were performed in the POA and BST region of 20 urethane anesthetized female rats during either the proestrus (elevated levels of estrogen/progesterone) or metestrus (low circulating hormones) stage of the estrous cycle. A total of 118 neurons in the POA and 65 neurons in the BST responded to the search stimuli, bilateral electrical stimulation of the viscerocutaneous branch of the pelvic nerve and/or sensory branch of the pudendal nerve (i.e., dorsal nerve of clitoris). Most of the neurons responding to the electrical search stimuli received a high degree of somatovisceral convergence, including inputs from the abdominal branches of the vagus, cervix, vagina, colon and skin territories on the perineum and trunk. Mean neuronal response thresholds for vaginal and cervical stimulation but not colon distention were significantly higher for animals tested during proestrus. Also, there was a shift in POA and BST neuronal responsiveness towards more inhibition and less excitation during proestrus for a variety of somatovisceral inputs. These data demonstrate that the changes in hormonal status affect the properties of POA and BST neurons, which likely relates not only to the functional importance of these inputs for reproductive behaviors but also for nociceptive processing as well.

Endometriosis-induced vaginal hyperalgesia in the rat: effect of estropause, ovariectomy, and estradiol replacement

Endometriosis (ENDO) is a painful disorder defined by extrauteral endometrial growths. It is created in rats by autotransplanting pieces of uterus (which form cysts), or, for shamENDO, fat (no cysts). ENDO induces vaginal hyperalgesia, likely via central sensitization. The severity of this hyperalgesia correlates with estradiol levels during the estrous cycle, suggesting the hyperalgesia is estradiol-modulated. If so, then hyperalgesic severity should track estradiol changes during reproductive senescence (estropause) when estradiol levels initially decrease, then increase. Using psychophysical methods to assess vaginal nociception, we found that the severity of ENDO-induced hyperalgesia paralleled estradiol changes during estropause: hyperalgesia first decreased, then returned. Furthermore, the return occurred regardless of the presence of the cysts (excised in some rats). This finding provides further support for ENDO's likely centrally-mediated effects. Additionally, the results suggest that elimination of estradiol via ovariectomy (OVX) should alleviate ENDO-induced hyperalgesia and estradiol replacement should restore it. However, in healthy and shamENDO rats, OVX produces a vaginal hyperalgesia that is alleviated by estradiol, likely via estradiol's peripheral influences on the vagina. Hence, we tested the hypothesis that OVX in ENDO rats would trigger a different type of vaginal hyperalgesia dependent on the loss of estradiol. We predicted that the opposing influences of estradiol on ENDO- and OVX-induced hyperalgesia would cancel each other. As predicted, OVX had no effect on ENDO-induced hyperalgesia and estradiol replacement alleviated it. These results suggest that, in intact rats, ENDO-induced vaginal hyperalgesia is exacerbated by estradiol, and that different mechanisms underlie ENDO-induced versus OVX-induced vaginal hyperalgesia.

Estrogen modulation of ovariectomy-induced hyperalgesia in adult mice

Some chronic pain conditions are more prevalent in women. However, the evidence from both human and animal studies as to whether estrogen is pro- or anti-nociceptive is inconsistent. We have used a model of functional abdominal pain in mice to examine the role of estrogen in the modulation of a hyperalgesic state induced by ovariectomy. C57/BL6 female mice were either ovariectomized (OVX), received the same surgery without removing the ovaries or were tested without any surgical procedure. Mechanical hyperalgesia was assessed by von Frey filaments and thermal pain was measured using a hot-plate at 50 degrees C. OVX mice, but not sham-operated, developed mechanical hyperalgesia localized to the abdominal region, the hindlimbs and the proximal tail, 4-5 weeks after OVX as well as a reduction in response latency to the hot plate. OVX animals were implanted with 17beta-estradiol pellets or with similar pellets with no hormone five weeks after OVX, when the hyperalgesic state was fully developed, and the estrogen reversed both mechanical and thermal hyperalgesia. Vaginal smears were taken to record the phase of the cycle at the time of the test from all animals and no significant differences were detected in mechanical hyperalgesia or in thermal pain threshold between normal animals in different phases of their estrous cycle. These results show that OVX induces a hyperalgesic state of slow onset and long duration that can be reversed by estrogen. We have also observed no estrous cycle modulation of pain sensitivity in normal animals.

Pelvic pain after gonadotropin administration as a potential sign of endometriosis

We describe five patients who developed significant pelvic pain, requiring narcotics, during a controlled ovarian hyperstimulation cycle and who were surgically diagnosed with significant endometriosis. Severe pain, especially if it requires narcotics, is unusual for patients undergoing controlled ovarian hyperstimulation and may be an indicator of endometriosis.

FKBP52 deficiency-conferred uterine progesterone resistance is genetic background and pregnancy stage specific

Immunophilin FKBP52 serves as a cochaperone to govern normal progesterone (P(4)) receptor (PR) function. Using Fkbp52(-/-) mice, we show intriguing aspects of uterine P(4)/PR signaling during pregnancy. Implantation failure is the major phenotype found in these null females, which is conserved on both C57BL6/129 and CD1 backgrounds. However, P(4) supplementation rescued implantation and subsequent decidualization in CD1, but not C57BL6/129, null females. Surprisingly, experimentally induced decidualization in the absence of blastocysts failed in Fkbp52(-/-) mice on either background even with P(4) supplementation, suggesting that embryonic signals complement uterine signaling for this event. Another interesting finding was that while P(4) at higher than normal pregnancy levels conferred PR signaling sufficient for implantation in CD1 null females, these levels were inefficient in maintaining pregnancy to full term. However, elevating P(4) levels further restored PR signaling to a level optimal for successful term pregnancy with normal litter size. Collectively, the results show that the indispensability of FKBP52 in uterine P(4)/PR signaling is a function of genetic disparity and is pregnancy stage specific. Since there is evidence for a correlation between P(4) supplementation and reduced risks of P(4)-resistant recurrent miscarriages and remission of endometriosis, these findings have clinical implications for genetically diverse populations of women.