Development of an experimental model of endometriosis using mice that ubiquitously express green fluorescent protein.

BACKGROUND Aiming at improving an animal model of endometriosis, we developed a homologous mouse model using 'green mice' that ubiquitously express green fluorescent protein. METHODS Endometrial fragment obtained from estradiol (E2)-supplemented ovariectomized 'green mice' was minced and injected into the peritoneal cavity of ovariectomized wild-type mice. The recipient wild mice were raised with or without E2 supplementation for 2 weeks, and then were euthanized. Endometriotic lesions that developed in the abdomen were examined both macroscopically and microscopically under fluorescence, and weight of the lesions was measured. RESULTS The endometriotic lesions were more clearly detected under fluorescence imaging than by conventional macroscopic examination. Histologically, endometriotic lesions deriving from 'green mice' were sharply distinguished from surrounding host tissues under fluorescence microscopy. More lesions developed in E2-supplemented than control recipient mice. The measured fluorescence intensity of endometriotic lesions showed significant positive correlation with their weight (R=0.844, P<0.0001), and was significantly higher in E2-supplemented mice than in vehicle-supplemented mice (P=0.0062). CONCLUSION The present endometriosis model using 'green mice' would be useful for expeditious identification and quantitative evaluation of endometriotic lesions.