Potential involvement of hemoglobin and heme in the pathogenesis of peritoneal endometriosis

Abstract

Objective: To test whether hemoglobin may accumulate in the peritoneal cavity in case of endometriosis and to assess whether heme oxygenases (HO), detoxifying heme, are expressed in ectopic endometrium and peritoneal cells.

Design: Prospective study involving patients with and without endometriosis.

Setting: Department of gynecology in a university hospital.

Patient(s): Seventy-six patients undergoing laparoscopy for tubal sterilization or infertility and/or pelvic pain.

Intervention(s): Collection of peritoneal fluid (PF), blood samples, and biopsies from endometrium and peritoneum.

Main outcome measure(s): Measurement of free hemoglobin and its byproduct, total and direct bilirubin, in serum and PF and analysis of HO-1 and HO-2 expression in biopsies by reverse transcription polymerase chain reaction and semiquantitative immunohistochemistry.

Result(s): Higher levels of hemoglobin were found in the PF of patients with endometriosis. There was no concomitant increase in bilirubin concentrations in the PF, and HO-1 was poorly expressed in peritoneal mesothelium and macrophages. Heme oxygenase-1 and HO-2 were strongly expressed in ectopic endometrium, especially in red lesions.

Conclusion(s): Our results suggest that heme may be involved in the pathogenesis and/or development of endometriosis and that the HO system, although expressed, might be insufficient to detoxify heme in women with endometriosis.