Characterization of iron deposition in endometriotic lesions induced in the nude mouse model

BACKGROUND: Pelvic endometriotic lesions are often laden with hemosiderin. In order to investigate the potential source of such iron deposits, we examined whether the seric and erythrocyte fractions of menstrual effluent might influence the occurrence of iron deposition within lesions in a murine model of endometriosis. METHODS: Endometriosis was induced in 57 nude mice by intraperitoneal injection of unfractionated human menstrual effluent, endometrial fragments plus serum, endometrial fragments plus erythrocytes or endometrial cell fraction alone. The number of implants, histologic aspect, proliferative activity and iron deposition in lesions was assessed. RESULTS: On day 5, lesions were evidenced in all 10 mice receiving menstrual effluent, in 9/13 of those injected with the cellular fraction, in 10/13 with the cellular fraction plus serum and in 10/12 with the cellular fraction plus erythrocytes. Iron conglomerates were observed at the interface between the lesion and peritoneum when menstrual effluent (47 deposits/mm(2)) and the cellular fraction with erythrocytes (20 deposits/mm(2)) were injected, but were scarce when the cellular fraction was injected without erythrocytes, either alone (4 deposits/mm(2)) or with serum (2 deposits/mm(2)) (P < 0.05). CONCLUSIONS: Iron conglomerates, typically found in the stroma of endometriotic lesions, were induced by erythrocytes present in menstrual effluent. This may be one of the factors triggering oxidative damage and chronic inflammation.