Proliferation of ovarian theca-interstitial cells is modulated by antioxidants and oxidative stress

BACKGROUND: Maintenance of ovarian homeostasis requires precise regulation of proliferation of thecal-interstitial (T-I) cells. Recent evidence indicates that oxidative stress and antioxidants modulate proliferation of various tissues under both physiological and pathological conditions. This study evaluated the effects of oxidative stress and antioxidants on T-I proliferation. METHODS: Rat T-I cells were cultured in serum-free medium and proliferation was assessed by determination of DNA synthesis using the thymidine incorporation assay, by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and by direct counting of steroidogenically active cells and steroidogenically inactive cells. RESULTS: Antioxidants and reactive oxygen scavengers induced a dose-dependent decrease of T-I proliferation. Vitamin E succinate was inhibitory at 10±100 mmol/l, ebselen was inhibitory at 0.3±30 mmol/l, and superoxide dismutase was inhibitory at 300±1000 IU/ml. In contrast, oxidative stress resulted in a biphasic effect. Modest oxidative stress induced by 1 mmol/l hypoxanthine and xanthine oxidase (3± 30 mU/ml) stimulated proliferation of T-I cells, while greater oxidative stress induced by xanthine oxidase (1 mU/ml) profoundly inhibited proliferation. Direct cell counting demonstrated comparable effects on steroidogenically active and inactive cells. CONCLUSIONS: Reactive oxygen species may play a role in the regulation of growth of ovarian mesenchyme. Under pathological conditions, such as those encountered in polycystic ovary syndrome, excessive oxi-dative stress and depletion of antioxidants may contribute to ovarian mesenchymal hyperplasia. Key words: antioxidants/oxidative stress/proliferation/thec