Abstract
BackgroundThe roles of the neurotrophins NGF (Neurotrophic growth factor) and BDNF (brain-derived neurotrophic factor) in neuronal growth and development are already known. Meanwhile, the neurotrophin receptors TrkA (tropomyosin related kinase A), TrkB, and p75 are important for determining the fate of cells. In endometriosis, this complex system has not been fully elucidated yet. The aim of this study was to evaluate the expression and location of these neurotrophins and their receptors in peritoneal (PE) and deep infiltrating endometriotic (DIE) tissues and to measure and compare the density of nerve fibers in the disease subtypes.MethodsPE lesions (n = 20) and DIE lesions (n = 22) were immunostained and analyzed on serial slides with anti-BDNF, −NGF, −TrkA, −TrkB, −p75,-protein gene product 9.5 (PGP9.5, intact nerve fibers) and -tyrosine hydroxylase (TH, sympathetic nerve fibers) antibodies.ResultThere was an equally high percentage (greater than 75 %) of BDNF-positive immunostaining cells in both PE and DIE. TrkB (major BDNF receptor) and p75 showed a higher percentage of immunostaining cells in DIE compared to in PE in stroma only (p < 0.014, p < 0.027, respectively). Both gland and stroma of DIE lesions had a lower percentage of NGF-positive immunostaining cells compared to those in PE lesions (p < 0.01 and p < 0.01, respectively), but there was no significant reduction in immunostaining of TrkA in DIE lesions. There was no difference in the mean density of nerve fibers stained with PGP9.5 between PE (26.27 ± 17.32) and DIE (28.19 ± 33.15, p = 0.8). When we performed sub-group analysis, the density of nerves was significantly higher in the bowel DIE (mean 57.33 ± 43.9) than in PE (mean 26.27 ± 17.32, p < 0.01) and non-bowel DIE (mean 14.6. ± 8.6 p < 0.002).ConclusionsWhile the neurotrophin BDNF is equally present in PE and DIE, its receptors TrkB and p75 are more highly expressed in DIE and may have a potential role in the pathophysiology of DIE, especially in promotion of cell growth. BDNF has a stronger binding affinity than NGF to the p75 receptor, likely inducing sympathetic nerve axonal pruning in DIE, resulting in the lower nerve fiber density seen.Electronic supplementary materialThe online version of this article (doi:10.1186/s12958-016-0178-5) contains supplementary material, which is available to authorized users.
Highlights
The roles of the neurotrophins nerve growth factor (NGF) (Neurotrophic growth factor) and brain-derived neurotrophic factor (BDNF) in neuronal growth and development are already known
While the neurotrophin BDNF is present in PE and deep infiltrating endometriotic (DIE), its receptors TrkB and p75 are more highly expressed in DIE and may have a potential role in the pathophysiology of DIE, especially in promotion of cell growth
Cell growth and development Based on the high degree of staining for BDNF in both glands and stroma of PE and DIE, this neurotrophin appears to play a role in the innervation of endometriosis
Summary
The roles of the neurotrophins NGF (Neurotrophic growth factor) and BDNF (brain-derived neurotrophic factor) in neuronal growth and development are already known. The neurotrophin receptors TrkA (tropomyosin related kinase A), TrkB, and p75 are important for determining the fate of cells. In endometriosis, this complex system has not been fully elucidated yet. The aim of this study was to evaluate the expression and location of these neurotrophins and their receptors in peritoneal (PE) and deep infiltrating endometriotic (DIE) tissues and to measure and compare the density of nerve fibers in the disease subtypes. Endometriosis is diagnosed by the presence of endometrial glands and stroma outside of the uterine cavity These endometriotic lesions are predominantly found in the pelvis, namely on the peritoneum, ovaries, myometrium of the uterus (adenomyosis) and the bowel. But not all, conclude that these aspects differ between DIE and PE endometriosis [2,3,4]
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