Maria Luisa Barcena de Arellano

Overexpression of nerve growth factor in peritoneal fluid from women with endometriosis may promote neurite outgrowth in endometriotic lesions

To investigate the role of the nerve growth factor (NGF) in the endometriosis-associated innervation in the development of endometriosis-associated symptoms, 41 peritoneal fluid samples (PF) from patients with surgically and histologically proven endometriosis and 20 PF from patients with other gynecologic conditions were analyzed with Western blot and a novel in vitro model using dorsal root ganglia (DRG) to show neuronal outgrowth; endometrial cells also were analyzed. The results suggest that the PF of endometriosis patients and endometriotic lesions have neurotropic properties, because the Western blot analysis and the cell culture stainings showed NGF expression, and the neurite outgrowth of DRG treated with PF of patients with endometriosis was significantly higher than when treated with PF of patients without endometriosis. Furthermore, blocking NGF with both anti-NGF and K252a leads to a significant decrease in neurite outgrowth.

Imbalance between sympathetic and sensory innervation in peritoneal endometriosis

To investigate possible mechanisms of pain pathophysiology in patients with peritoneal endometriosis, a clinical study on sensory and sympathetic nerve fibre sprouting in endometriosis was performed. Peritoneal lesions (n=40) and healthy peritoneum (n=12) were immunostained and analysed with anti-protein gene product 9.5 (PGP 9.5), anti-substance P (SP) and anti-tyrosine hydroxylase (TH), specific markers for intact nerve fibres, sensory nerve fibres and sympathetic nerve fibres, respectively, to identify the ratio of sympathetic and sensory nerve fibres. In addition, immune cell infiltrates in peritoneal endometriotic lesions were analysed and the nerve growth factor (NGF) and interleukin (IL)-1β expression was correlate with the nerve fibre density. Peritoneal fluids from patients with endometriosis (n=40) and without endometriosis (n=20) were used for the in vitro neuronal growth assay. Cultured chicken dorsal root ganglia (DRG) and sympathetic ganglia were stained with anti-growth associated protein 43 (anti-GAP 43), anti-SP and anti-TH. We could detect an increased sensory and decreased sympathetic nerve fibres density in peritoneal lesions compared to healthy peritoneum. Peritoneal fluids of patients with endometriosis compared to patients without endometriosis induced an increased sprouting of sensory neurites from DRG and decreased neurite outgrowth from sympathetic ganglia. In conclusion, this study demonstrates an imbalance between sympathetic and sensory nerve fibres in peritoneal endometriosis, as well as an altered modulation of peritoneal fluids from patients with endometriosis on sympathetic and sensory innervation which might directly be involved in the maintenance of inflammation and pain.

Influence of nerve growth factor in endometriosis-associated symptoms.

To investigate the role of the nerve growth factor (NGF) in the development of dysmenorrhea/pelvic pain in patients with endometriosis, we performed a prospective, clinical, blind study. Peritoneal fluids (PFs) were obtained from patients with histologically proven endometriosis. Patients with endometriosis were divided into 7 different groups depending on their preoperative pain score and symptomatology: patients with no pain, patients with minimal pain (dysmenorrhea, pelvic pain, or both), and patients with severe pain (dysmenorrhea, pelvic pain, or both) and were used for the neuronal growth assay with cultured chicken dorsal root ganglia (DRG) and for Western blot analyses. Dorsal root ganglia were stained with anti-calcitonin gene-related peptide (CGRP) and anti-growth-associated protein 43 (GAP 43). Peritoneal fluids from patients with endometriosis induce neurite outgrowth. There was no significant difference in the outgrowth between the 7 pain groups. Western blot analyses showed a moderate NGF expression in the PFs from patients with endometriosis, without significant differences in the 7 pain groups. The present study suggests that the neurotrophic properties of endometriotic tissues are endometriosis- and not pain-associated.

Evidence of neurotrophic events due to peritoneal endometriotic lesions

To investigate the neurotrophic properties of endometriosis, as well as the involvement of neurotrophic factors in the development of chronic pelvic pain in patients with endometriosis, we performed a prospective clinical study. The presence of neurotrophins was investigated in the peritoneal fluid (PF) of patients with peritoneal endometriotic lesions or adenomyosis, as well as from women with non-endometriotic adhesions and from women without endometriosis/adenomyosis/adhesions. The PF from patients with peritoneal endometriotic lesions was divided in three groups: asymptomatic endometriosis, minimal pain and severe pain. PF from patients with adenomyosis or with non-endometriotic adhesions and the control group were divided in patients without pain and with pain. Neurotrophin expression in PF was analyzed using Elisa and the neuronal growth assay with cultured chicken sensory ganglia (dorsal-root-ganglia, DRG) and sympathetic ganglia. PF from women with peritoneal endometriotic lesions overexpress nerve growth factor (NGF) and neurotrophin-3 (NT-3), but not brain derived neurotrophic factor (BDNF), whereas the PF of women with adenomyosis or adhesions seems to express normal amounts of these factors. Neurotrophin expression did not differ among the pain groups. Furthermore, the PF from patients with peritoneal endometriotic lesions induced a strong sensory and a marginal sympathetic neurite outgrowth, while the PF from women with adenomyosis and non-endometriotic adhesions induced an outgrowth similar to the control group. The induced neurite outgrowth could only be inhibited in DRG incubated with peritoneal endometriotic lesions. Interestingly, the outgrowth of sympathetic ganglia was inhibited in all studied groups. The present study suggests that only peritoneal endometriotic lesions lead to an increased release of NGF and NT-3 into the PF and that NGF modulates the nerve fiber growth in endometriosis.

Immunohistochemical characterization of endometriosis-associated smooth muscle cells in human peritoneal endometriotic lesions

BACKGROUND Smooth muscle cells (SMC) are common components of endometriotic lesions. SMC have been characterized previously in peritoneal, ovarian and deep infiltrating endometriotic lesions and adenomyosis. The aim of this retrospective study was to investigate the extent of differentiation in endometriosis-associated SMC (EMaSMC) in peritoneal endometriotic lesions. METHODS We obtained biopsies from peritoneal endometriotic lesions (n = 60) and peritoneal sites distant from the endometriotic lesion (n = 60), as well as healthy peritoneum from patients without endometriosis (control tissue, n = 10). These controls were hysterectomy specimens from patients without endometriosis or adenomyosis. Histopathological examination of peritoneal specimens using antibodies against oxytocin receptor (OTR), vasopressin receptor (VPR), smooth muscle myosin heavy chain (SM-MHC), estrogen receptor (ER) or progesterone receptor (PR) was performed. To identify SMC and their level of differentiation, antibodies for smooth muscle actin desmin and caldesmon were used. RESULTS SMC were detected in all endometriotic lesions. SMC were more abundant in unaffected peritoneum of women with endometriosis (38%) compared with women without endometriosis (6%; P < 0.0001). Depending on the level of differentiation, SMC stained for SM-MHC, OTR, VPR, ER and PR. OTR was only detected in fully differentiated SMC. CONCLUSIONS Identification of OTR, VPR, ER and PR leads to the hypothesis that the EMaSMC might be functionally active and possibly involved in the generation of pain associated with endometriosis.

Eutopic endometrium from women with endometriosis does not exhibit neurotrophic properties

The role of neurotrophins in eutopic endometrium from endometriosis-patients was investigated in a prospective study using immunofluorescence-staining, Western blot and a neuronal growth assay. The nerve growth factor is expressed in primary endometrial cell culture from women with and without endometriosis. Western blot analysis of endometrial biopsies or uterine fluid from patients with and without endometriosis shows no difference in the neurotrophin expression. We could not find a difference between patients with and without endometriosis with regards to the neurite outgrowth of sensory ganglia when treated with conditioned cultured medium or uterine fluid. This result refutes the assumed neurotrophic properties of eutopic endometrium of patients with endometriosis.

Neuroimmunomodulatory Alterations in Non-Lesional Peritoneum Close to Peritoneal Endometriosis

Objectives: An imbalance in the ratio of sensory to sympathetic nerve fibre (NF) density in peritoneal endometriotic lesions (pEL) has recently been demonstrated and leads to the assumption that this preponderance of the sensory pro-inflammatory milieu is a major cause of pain in endometriosis. Therefore, the density of sensory and sympathetic NFs was determined in distal unaffected peritoneum of endometriosis patients to be able to detect possible alterations in unaffected peritoneum. Methods: In serial pEL sections (n = 40), lesional and matching unaffected peritoneum as well as healthy peritoneum (HP) from patients without endometriosis (n = 15) were immunohistochemically analysed to identify protein gene product 9.5-, substance P- and tyrosine hydroxylase-positive NFs (intact, sensory and sympathetic NFs, respectively). In addition, the amount of immune cell infiltrates and the expression of nerve growth factor (NGF) and interleukin (IL)-1β in nerves of peritoneal endometriotic specimens were compared to those in the HP. Results: The overall NF density in the non-lesional, unaffected peritoneum of endometriosis patients is significantly reduced in comparison to both HP and pEL, while sensory NFs remain the same; the sympathetic NF density is significantly decreased compared to HP, but is still higher than the density close to the pEL. Immune cell infiltrates as well as NGF and IL-1β expression in nerves is significantly elevated in distal unaffected peritoneum in comparison to HP. Conclusion: The altered NF density in the non-lesional, unaffected peritoneum of endometriosis patients suggests new aspects in the understanding of the development of endometriosis and pain management in endometriosis.

Neurotrophin Expression Is Not Affected in Uteri of Women with Adenomyosis

To investigate the involvement of neurotrophins and nerve fibres in the pathogenesis of adenomyosis, we performed a retrospective, clinical study. Hysterectomy specimens from 40 patients with histologically proven adenomyosis and from 20 patients without adenomyosis or endometriosis were used for immunohistochemical analysis. In order to investigate neurotrophic properties in adenomyosis, the antibodies against nerve growth factor (NGF), neurotrophin 3 (NT-3), the high-affinity NGF receptor (TrkA), the low-affinity neurotrophin receptor (p75NTR), the neuronal marker S100 (for myelinated nerve fibres) and protein gene product 9.5 (PGP9.5; for intact nerve fibres) were used. There was no significant difference in the NGF, NT-3 and p75NTR expression in the myometrium or endometrium between the adenomyosis and the control group. The nerve fibre density (S100, PGP9.5 and p75NTR) did not significantly differ between the adenomyosis and control group, the nerve fibre density of the adenomyosis group was tendentially decreased when compared with the nonporous control group. The present study suggests that endometrial and uterine neurotrophin expression and endometrial innervation are not altered in adenomyosis; however, women with adenomyosis or with adenomyosis/endometriosis tendentially had less myometrial nerve fibres than the control group.

High lymph vessel density and expression of lymphatic growth factors in peritoneal endometriosis.

To investigate the occurrence of lymph vessels and lymphangiogenic growth factors in peritoneal lesions, we performed immunohistochemical staining of peritoneal lesions of 37 patients with antibodies against podoplanin (D2-40), lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), prospero homeobox protein 1 (Prox-1), vascular epithelial growth factor (VEGF)-C/VEGF-D. Overall, 10 lesions were double stained against D2-40 and von Willebrand factor. The lymph vessel density in peritoneal lesion was significantly higher in comparison with healthy peritoneum. All lymph vessel makers could be detected, whereby the lymph vessel density of LYVE-1- and Prox-1-positive lymph vessels was significantly higher than the lymph vessel density of D2-40-positive lymph vessels. Endometriotic epithelial cells and stromal cells (SCs) showed a moderate-to-strong VEGF-C/VEGF-D expression. The VEGF-C-/VEGF-D-positive macrophages in endometriotic SCs could be observed. The lymphatic vasculature seems to form a further component of peritoneal lesions and could be involved in the inflammatory process. These data demonstrated a further step in the clarification of the pathogenesis of endometriosis.

TRPV1-dependent hyperalgesia in peritoneal endometriosis

About 40% of the women with chronic pelvic pain suffer from endometriosis (EM). The chronic inflammatory condition in EM is accompanied with an imbalance of sensory and sympathetic peritoneal nerve fibers, with a hyperinnervation of sensory NF and a hypoinnervation of sympathetic NF close to peritoneal endometriotic lesions (pEL). However, the pro-inflammatory stage of EM does not correlate with the pain severity, suggesting that other inflammatory and/or pain mediators co-modulate the pain sensation in EM. The presence of the TRPV1 in the pEL using immunohistological analysis was examined. Neural PC12 cells were incubated with peritoneal fluid (PF) from women with and without EM and the amount of TRPV1-RNA and protein was evaluated. Close to the lesion, the density of TRPV1-positive NF was higher than in healthy peritoneum ( p p The relative TRPV1-RNA level was higher in cells incubated with PF from women with EM ( p This study confirmed an increase in TRPV1-positive NF in pEL, suggesting that TRPV1 plays a crucial role in the pain transmission in EM. Furthermore, an overexpression of the TRPV1-RNA and protein level in PC12 incubated with PF from women with EM was demonstrated, suggesting that the PF from women with EM expresses mediators that induce the expression of TRPV1 in pEL.