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.