BACKGROUNDEndometriosis (EM) is a benign gynecologic disease predominantly found in women of reproductive age. However, its pathogenesis is still poorly understood. Our experiment was designed to establish a stable and reliable cultural environment for coculture of endometrium and peritoneum, so as to observe the adhesion/invasion ability of endometrium from patients with or without EM.

METHODSEndometria of secretory phase and peritoneum were sampled from 6 women with endometriois during laparoscopy. Six with ovarian teratoma or simple ovarian cyst were taken as control. We cocultured endometrium and peritoneum into four groups (endometrium from EM cultured with peritoneum from EM, endometrium from control cultured with peritoneum from control, endometrium from EM cultured with peritoneum from non-EM and the endometrium from control cultured with peritoneum from EM) to observe the adhesion/invasion process in gas-liquid surface culture and in-medium culture. Specimens were collected at 1 hour, 6 hours, 12 hours, 24 hours, 2 days, 3 days, 4 days, 5 days, 6 days and 7 days for histology, immunofluorescence and immunohistochemical analysis on cytokeratin 8 (CK8) and CD10.

RESULTSThe gas-liquid surface culture was superior to in-medium culture for the maintenance of tissue morphology and survival of endometrium. CK8 immunoflurescence demonstrated no remarkable difference in adhesion process between patients with and without EM. CD10 immunochemistry manifested frequent invasion of endometrial stromal cells from EM patients into peritoneum of up to 3 days culture, while the endometriotic cells from non-EM patients did not invade into peritoneum.

CONCLUSIONSGas-liquid surface culture is a suitable model for observing the early events in EM lesion formation. Endometrium from patients with EM showed increased invasion capacity during coculture, which might help to explain the etiology of endometriosis.