Expression of angiopoietin 1 and 2 in ectopic endometrium on the chicken chorioallantoic membrane

OBJECTIVE: To investigate the role of angiopoietin 1 and 2 (ANGPT1/ANGPT2) in angiogenesis of the ectopic endometrium as a crucial step in the development of an endometriotic lesion, we analyzed their expression patterns in an experimental model of endometriosis. DESIGN: Experimental prospective study. SETTING: University hospital. PATIENT(S): Endometrium samples obtained from healthy, ovulating women undergoing hysterectomy for benign gynecologic conditions. INTERVENTION(S): Endometrial fragments were transplanted to the chicken chorioallantoic membrane (CAM) and cultivated for 0, 24, 48, and 72 hours. MAIN OUTCOME MEASURE(S): Expression of ANGPT1 and ANGPT2 mRNA was quantified by competitive reverse transcriptase polymerase chain reaction (RT-PCR) and normalized to expression of the housekeeping gene human glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA. The expression of ANGPT1 and ANGPT2 protein was analyzed by immunohistochemical staining. RESULT(S): All grafts expressed ANGPT1 and ANGPT2 mRNA. The mRNA concentration of both factors decreased after cultivation, but the ANGPT2/ANGPT1 ratio increased considerably during the first 24 hours of cultivation. The immunohistochemical investigation for ANGPT1 and ANGPT2 revealed presence of both proteins at all the times but no obvious correlation with the duration of cultivation. CONCLUSION(S): The ratio of ANGPT2/ANGPT1 mRNA in endometrial grafts increased after 24 hours of cultivation on the chicken chorioallantoic membrane and shows a shift toward a more dominant role of ANGPT2. This agrees with the current model of angiopoietin action in angiogenesis and might indicate angiogenic activity in the endometrial graft. The angiopoietins are likely to play an important role in the pathogenesis of endometriosis.