Expression of erythropoietin and erythropoietin receptor in peritoneal endometriosis.
Recent studies have indicated new physiological roles for erythropoietin (Epo) unrelated to erythropoiesis. We previously demonstrated that the Epo concentrations in peritoneal fluid from patients with stage I endometriosis were significantly higher than those with stages II, III and IV of the disease. Therefore, we hypothesized that Epo may play a role in the pathogenesis of endometriosis, particularly during the early stages of the disease. We investigated the localization of Epo and the Epo receptor (Epo-R) in peritoneal endometriosis and eutopic endometrium, using immunohistochemistry. We detected Epo and Epo-R localized within glandular epithelial cells in both peritoneal endometriosis and eutopic endometrium. There was no significant difference in Epo expression between red and black peritoneal lesions, whereas Epo-R expression was significantly lower in black peritoneal lesions when compared to red lesions. Epo and Epo-R expression levels within red peritoneal lesions were comparable to those of eutopic endometrium from patients with endometriosis. The present findings suggest that Epo may play a role in the pathophysiology of endometriosis.