RESUMO
OBJECTIVES: Low-dose estrogen-progestin (LEP) agents are often used for relieving endometriosis-associated chronic pelvic pain, but a direct effect of LEP on endometriotic lesions remains to be demonstrated. The objective of this study is to investigate the antiproliferative and apoptotic effects of the synthetic progestin norethisterone (NET) against human endometriotic stromal cells (ESCs). STUDY DESIGN: Ovarian endometrioma specimens were obtained at laparoscopy from 19 patients with endometriosis, and ESCs were isolated. The antiproliferative effect of compounds against cultured ESCs was evaluated by measuring the inhibition of [(3)H]thymidine incorporation. The ability of compounds to induce apoptosis in the cultured cells was evaluated by the measurement of caspase 3/7 activity and by nuclear staining. The cytotoxicity of compounds was evaluated by measuring the leakage of lactate dehydrogenase (LDH) into the supernatant of the cell culture. RESULTS: NET and progesterone (P4) at concentrations of greater than 10nM significantly inhibited [(3)H]thymidine incorporation in a dose-dependent manner. Co-treatment with 17ß-estradiol at 0.1 ng/mL did not affect the inhibition of [(3)H]thymidine incorporation by NET. At concentrations greater than 100 nM, NET significantly increased caspase 3/7 activity and the numbers of apoptotic cells, whereas P4 did not. Treatment of ESCs for 24h with NET or P4 at concentrations of up to 1000 nM did not cause LDH leakage. CONCLUSIONS: NET inhibits the proliferation of ESCs and induces their apoptosis. These results suggest a possible direct effect of NET on endometriotic lesions in patients with endometriosis.