Study on expression of estrogen receptor isoforms in eutopic and ectopic endometrium of ovarian endometriosis

Abstract

To investigate the distribution of ER isoforms in endometriosis and eutopic endometrium. Tissue samples of patients with ovarian endometriosis, treated in People's Liberation Army General Hospital from January 2004 to December 2006, were retrieved. A total of 60 cases of ovarian endometriotic cysts with their corresponding eutopic endometrium (30 cases of proliferation phase and 30 of secretary phase eutopic endometrium) and 30 cases of normal endometrium (15 proliferative and 15 secretary phase endometrial samples respectively) were included. Expressions of ERalpha and ERbeta were analyzed using immunohistochemistry and the expression ratio was statistically analyzed by using SPSS 12.0 software. Expressions of both ERalpha and ERbeta in epithelial cells were positively correlated with that of the stromal cells. The expression of ERalpha in eutopic endometrium (73.3% in epithelium and 76.7% in stroma) was significantly higher than that in ovarian endometriotic cysts (43.3% in epithelium and 46.7% in stroma), or normal control (56.7% in epithelium and 50.0% in stroma, respectively, each P < 0.05. However, the expression of ERbeta (90.0% in epithelium and 76.7% in stroma) was higher in ovarian endometriotic cysts than that in the eutopic endometrium (68.0% in epithelium and 63.3% in stroma respectively, P < 0.05), and ERbeta expression in eutopic endometrium was higher than that in the normal control endometrium (36.7% in epithelium and 26.7% in stroma, respectively, P < 0.05). The expressions of both ERalpha and ERbeta changed periodically in eutopic and normal endometrium, whereas ERalpha and ERbeta level were less variable in the ectopic endometrium. The expression of ERbeta was statistically higher than that of ERalpha (P < 0.05) in ectopic endometrium, whereas no significant difference was seen between the two isoforms in the eutopic or normal endometrium. Both ERalpha and ERbeta have higher expression levels in eutopic endometrium of patients with ovarian endometriotic cysts. ERbeta is predominantly expressed in endometriotic cysts, where the expression of ERalpha is limited. The different distribution of ERalpha and ERbeta may play an important role in the development of ovarian endometriosis.