Expression and significance of ERβ and TrkB in endometriosis

Elucidating the role of Brain-Derived Neurotrophic Factor (BDNF) and its receptor Tyrosine Receptor Kinase B (TrkB) in the development and symptoms of endometriosis

Endometriosis (EMs) is a common disease among women of reproductive age, and as of now, the clinical understanding of the etiology of this disease remains unclear. The occurrence of EMs has a profound impact on the reproductive health of women, making early diagnosis and treatment of this disease a pressing challenge in clinical practice. Recent studies have found that Brain-Derived Neurotrophic Factor (BDNF), in combination with its high-affinity receptor Tyrosine Receptor Kinase B (TrkB), participates in the development of EMs and the appearance of clinically relevant symptoms by activating the Mitogen-Activated Protein Kinase (MAPK) pathway, the Phosphatidylinositol 3-Kinase/Protein Kinase B (PI3K/AKT) pathway, and the Phospholipase C-gamma (PLCγ) signaling pathway, or by interacting with other factors. In order to gain a deeper understanding of the pathogenesis related to EMs, this article reviews the roles of BDNF and TrkB in EMs, particularly in terms of aberrant apoptosis and autophagy, cell invasion, proliferation, angiogenesis, oxidative stress, and inflammatory reactions, as well as their relationship with the symptoms associated with EMs.

BDNF and TrKB expression levels in patients with endometriosis and their associations with dysmenorrhoea

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a known regulator of the development and maintenance of chronic pain in various chronic disorders. Together with its high-affinity tyrosine kinase type B (TrKB) receptor, BDNF is extensively expressed in the mammalian female reproductive system. However, BDNF and TrKB expression in different stages of endometriosis and the relationship between the expression of each in ectopic lesions and endometriosis pain remain unclear.

METHODS

Sixty-two women who underwent laparoscopic surgery were enrolled in this study: forty-six diagnosed with ovarian endometrioma (study group) and sixteen diagnosed with ovarian benign tumours (control group). Samples from eutopic endometrium and ovarian endometriotic lesions were obtained at laparoscopic surgery. BDNF and TrKB messenger RNA (mRNA) and proteins levels in the eutopic and ectopic endometrium of both groups were measured by real-time PCR and immunohistochemical staining, respectively. Before the surgery the visual analogue scale (VAS) was used to measure dysmenorrhoea.

RESULTS

BDNF and TrKB expression levels were higher in ovarian endometriotic lesions than in eutopic endometrium and normal endometrium (P < 0.05), and there was no cyclical change. Furthermore, their expression levels were higher in eutopic endometrium than in normal endometrium (P < 0.05), and BDNF and TrKB levels were higher in stage IV ovarian endometriotic lesions than in stage II and III lesions (P < 0.05), with their expression being non-significantly higher in stage III than in stage II (P > 0.05). Additionally, correlation coefficients for the association analysis between the mRNA expression of BDNF or TrKB in eutopic endometrium and the dysmenorrhoea VAS score were r = 0.52 and r = 0.56 for BDNF and TrKB, respectively (P < 0.05). The correlation coefficients for the associations between BDNF and TrKB in both the eutopic and ectopic endometrium were r = 0.82 and r = 0.66, respectively (P < 0.05).

CONCLUSIONS

BDNF and TrKB are closely related to dysmenorrhoea caused by endometriosis and may be important in the pathobiology or pathophysiology of endometriosis.

Neurotrophins and glial cell line-derived neurotrophic factor in the ovary: physiological and pathophysiological implications

BACKGROUND

Neurotrophins [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4)] and glial cell line-derived neurotrophic factor (GDNF) are soluble polypeptide growth factors that are widely recognized for their roles in promoting cell growth, survival and differentiation in several classes of neurons. Outside the nervous system, neurotrophin (NT) and GDNF signaling events have substantial roles in various non-neural tissues, including the ovary.

OBJECTIVE AND RATIONALE

The molecular mechanisms that promote and regulate follicular development and oocyte maturation have been extensively investigated. However, most information has been obtained from animal models. Even though the fundamental process is highly similar across species, the paracrine regulation of ovarian function in humans remains poorly characterized. Therefore, this review aims to summarize the expression and functional roles of NTs and GDNF in human ovarian biology and disorders, and to describe and propose the development of novel strategies for diagnosing, treating and preventing related abnormalities.

SEARCH METHODS

Relevant literature in the English language from 1990 to 2018 describing the role of NTs and GDNF in mammalian ovarian biology and phenotypes was comprehensively selected using PubMed, MEDLINE and Google Scholar.

OUTCOMES

Studies have shown that the neurotrophins NGF, BDNF, NT-3 and NT-4 as well as GDNF and their functional receptors are expressed in the human ovary. Recently, gathered experimental data suggest putative roles for NT and GDNF signaling in the direct control of ovarian function, including follicle assembly, activation of the primordial follicles, follicular growth and development, oocyte maturation, steroidogenesis, ovulation and corpus luteum formation. Additionally, crosstalk occurs between these ovarian regulators and the endocrine signaling system. Dysregulation of the NT system may negatively affect ovarian function, leading to reproductive pathology (decreased ovarian reserve, polycystic ovary syndrome and endometriosis), female infertility and even epithelial ovarian cancers.

WIDER IMPLICATIONS

A comprehensive understanding of the expression, actions and underlying molecular mechanisms of the NT/GDNF system in the human ovary is essential for novel approaches to therapeutic and diagnostic interventions in ovarian diseases and to develop more safe, effective methods of inducing ovulation in ART in the treatment of female infertility.

Progesterone Receptor B (PGR-B) Is Partially Methylated in Eutopic Endometrium From Infertile Women With Endometriosis

Endometriosis is frequently related to infertility and little is known about the mechanisms underlying this association. Some studies point to an endometrial factor involved in this condition, which could compromise embryo implantation. Progesterone plays crucial role in endometrial receptivity by acting through progesterone receptor (PGR) isoforms PR-A and PR-B whose expression is epigenetically regulated by DNA methylation, in a specific promoter region for each isoform. Epigenetic changes in PGR-A and PGR-B may be related to progesterone resistance of endometriosis-related infertility. In order to better understand the mechanisms involved in endometrial receptivity, this case-control study aimed to compare the methylation pattern of PGR-A and PGR-B in eutopic endometrium from infertile women with and without endometriosis during the secretory phase. Endometrial biopsies from 19 patients (10 infertile women with endometriosis and 9 infertile controls) with regular cycles were performed during the secretory phase and were dated according to Noyes' criteria. The percentage of DNA methylation at PGR-A and PGR-B was carried out by high-resolution melting assay. The PGR-A gene showed 0% of DNA methylation (unmethylated) in both control and endometriosis groups. However, PGR-B gene showed a partially methylated pattern in majority of the patients (n = 7), with methylation percentage corresponding to 50%, while in the control group the percentage of methylation was 20% (hypomethylated; P = .04). The increased percentage of methylation at PGR-B may be related to reduced gene expression, which could compromise the endometrial receptivity in patients with endometriosis.

[Immunohistochemical predictors of recurrent ovarian endometriomas after laparoscopic surgery]

OBJECTIVE

To investigate the expression of proliferation and apoptotic factors (Ki-67, Bcl-2), inflammatory factors (NF-kβ p65, COX-2), adhesion factors (β-catenin), estrogen (ER-α) and progesterone receptors (PR-α) in ovarian endometrioma (OE) in patients with recurrent OE by an immunohistochemical assay.

SUBJECT AND METHODS

This investigation enrolled 48 reproductive-aged patients with OE. According to the course of the disease during a follow-up period of 1.5 years after surgical treatment, the biomaterial obtained from the examined patients was divided into two groups: 1) an OE capsule from 19 patients with recurrent OE (a study group); 2) an OE capsule from 28 patients without recurrent OE (a comparison group). This investigation used histological and immunohistochemical examinations. The histological analysis of the OE capsule was performed following a standard procedure. Their immunohistochemical analysis was carried out using the Tissue-Tek Quick-Ray kit that allows the preparation of paraffin blocks with a large number of tissue samples (tissue microarrays). Antibodies to Ki-67 (clone 30-9, VENTANA), Bcl-2 (clone 124, VENTANA), NF-kβ p65 (clone p65, 'Spring Bioscience Corp.'), COX-2 (clone CX-294, Agilent), β-catenin (clone 14, VENTANA), ER-α (clone SP1, VENTANA), and PR-α (clone 1E2, VENTANA) were also employed in the investigation. The specimens were prepared according to a standard protocol using a Ventana Ultra immunohistostainer. Positive and negative controls were used to correctly carry out immunohistochemical tests. Statistical analysis was performed using the applied statistical analysis programs Statistica 10.0 and Microsoft Excel.

RESULTS

The patients with recurrent OE had a significantly decreased expression of Ki-67 (2.86% vs. 9.69%; р=0.044) in the epithelial component of the OE capsule; a significantly lower expression of NF-kβ p65 (2.54 vs. 3.5; р=0.0082) and СОХ-2 (0.231 vs. 1.381; р=0.0025) in the stromal component of the OE capsule, a significantly increased expression of β-catenin (2.5 vs. 1.59; р=0.017) in the stromal component of the OE capsule; a significantly increased expression of PR-α (188.46 vs. 71.15; р=0.028) in the epithelial component of an OE capsule. The expression of ER-α (stromal component, 266 vs. 256.84; p=0.48; epithelial component, 251.54 vs. 233.85, p=0.82) and Bcl-2 (stromal component, 0.33 vs. 0.25; p=0.85; epithelial component, 0.944 vs. 0.625; p=0.31) in the OE capsule is not statistically significantly different between the study patient groups.

CONCLUSION

The immunohistochemical difference in the expression of a number of the markers under study can serve as the basis for a further investigation of these markers as predictors of recurrent OE after surgical treatment. Further investigations of these factors will also be able to examine the molecular mechanisms underlying the pathogenesis of recurrent OE, which will make it possible to affect these mechanisms in order to eliminate the fundamental causes of a recurrence of this disease.

Increased serum levels of mBDNF in women with minimal and mild endometriosis have no predictive power for the disease

The objective of our pilot clinical, prospective study was to determine the serum levels of mature brain-derived neurotrophic factor, in of women with endometriosis and controls and explore whether mature brain-derived neurotrophic factor is a potential biomarker for the disease. The patients were selected from the Endometriosis Marker Austria prospective cohort study conducted at the tertiary referral certified Endometriosis Center of the Medical University of Vienna. All women underwent laparoscopic surgery because there was a suspicion of endometriosis, or the women had pelvic pain, adnexal cysts, unexplained infertility, or uterine fibroids. Our main outcome parameter was total levels of mature brain-derived neurotrophic factor in serum, measured using ELISA. Our results show that serum levels of mature brain-derived neurotrophic factor are significantly higher in women with endometriosis compared to women without endometriosis. The mean serum protein levels are significantly higher in women with rAFS stage I and II endometriosis, whereas no difference was found in women with stage III and IV endometriosis and controls. Postoperative follow-up at 6-10 weeks revealed that surgical intervention leads to equilibration of the levels of secreted mature brain-derived neurotrophic factor between women with and without endometriosis. The difference between serum mature brain-derived neurotrophic factor levels of women with endometriosis compared to women without endometriosis is independent of menstrual cycle phase and overall self-reported pelvic pain. ROC-curve analysis showed that, the mature brain-derived neurotrophic factor is not a useful biomarker for endometriosis. In conclusion, although women with stage I and II endometriosis have increased levels of mature brain-derived neurotrophic factor in serum compared to controls, the difference is not predictive for the disease. Impact statement Endometriosis is a disease that can have a significant impact on the quality of life of affected women. The gold standard for diagnosis to this day remains visualization through laparoscopic surgery with histological verification. Current studies are attempting to find a biomarker with high sensitivity and specificity, which would bypass the surgery-associated risks and would significantly reduce costs. In an attempt to elucidate whether mature serum BDNF can serve as diagnostic marker for the disease, we compared the levels of the protein in women with endometriosis to endometriosis-free controls. While our results showed that serum concentrations of the mature protein were significantly higher in women with endometriosis, we did not find this marker to have the sensitivity or specificity needed in order to allow a reliable diagnosis.