Expression of BDNF and TrKB in Endometriosis and Dysmenorrhea

Abstract Background: Brain-derived neurotrophic factor (BDNF) has been recognized as a regulator in the formation and maintenance of chronic pain in various chronic disorders. BDNF together with its high-affinity tyrosine kinase type B (TrkB) receptor were found to be extensively expressed in mammalian female reproductive system. However, BDNF and TrkB expression in different stages of endometriosis, and the correlation between their expression in ectopic lesions and endometriosis pain remains unclear.Methods: This study enrolled 78 women underwent laparoscopic surgery. 62 women diagnosed as ovarian endometrioma, were recruited in the study group.16 women diagnosed as ovarian benign tumors were in the control group. The message RNA (mRNA) level of BDNF and TrKB was detected by real-time PCR, while the protein level was detected by immunohistochemical staining for eutopic and ectopic endometrium in both groups. Dysmenorrhea was assessed by the visual analogue scale (VAS) before the surgery.Results: Immunohistochemical analysis revealed that the expression of BDNF and TrKB in ovarian endometriotic lesions was the highest, followed by those in eutopic and normal endometrium (P<0.05). There was significant difference among each stage of endometriosis for the expression, which increased with the severity of stages. The results of RT-qPCR and immunohistochemistry were consistent with each other. Furthermore, The correlation between the mRNA expression of BDNF, TrKB in eutopic endometrium, and dysmenorrhea VAS score revealed that r=0.52 and 0.56, respectively (P<0.05). And when it came to BDNF, TrKB in eutopic endometrium, the correlation (r) was 0.82 (P<0.05).Conclusions: BDNF and TrKB may play essential roles in promoting disease progression during the development of endometriosis, and are closely related to dysmenorrhea caused by endometriosis.