['Polycystic ovary syndrome (PCOS) is associated with ovarian enlargement, prominent theca-interstitial hyperplasia, and excessive androgen production. Recent clinical trials have demonstrated that statins, 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors, decrease androgen levels in women with PCOS.', 'The present study evaluated the effect of statins on proliferation of human ovarian theca-interstitial cells.', 'In vitro experiments were performed in the university research laboratory.', 'Human theca-interstitial cells were isolated from ovaries of PCOS (n=4) and non-PCOS (n=4) patients.', 'The cells were incubated for 48 h without additives (control) or with simvastatin (3-30 μm), mevastatin (3-30 μm), and/or the cell- and mitochondrion-permeable form of cholesterol (22-hydroxycholesterol; 10 μm). To determine whether the effects of statins could be affected by leukocytes, the experiment was carried out on cells not purified of leukocytes and cells purified using anti-CD-45 immunomagnetic beads. The effect of statins on proliferation was evaluated by determination of DNA synthesis using radiolabeled thymidine-incorporation assay and by quantification of viable cells using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenil)-2H-tetrazolium assay.', 'Statins induced an inhibition of DNA synthesis in both the absence and the presence of 22-hydroxycholesterol; furthermore, 22-hydroxycholesterol alone also inhibited DNA synthesis. These effects of statins and 22-hydroxycholesterol were confirmed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenil)-2H-tetrazolium assay. Comparable inhibition of proliferation was observed in cells obtained from women with and without PCOS and in cell preparations treated and not treated with anti-CD-45 immunomagnetic beads.'] Do statins inhibit growth of human theca-interstitial cells in PCOS and non-PCOS tissues independently of cholesterol availability?