Plasminogen activator inhibitor-1 (PAI-1) is elevated in women with polycystic ovary syndrome (PCOS), but the regulation in granulosa cells (GCs) is unclear.PAI-1 expression in PCOS ovaries was investigated immunohistologically. PAI-1 expressions in HGrC1, a human GC cell line, were investigated at mRNA and activity levels. The expressions of TGF-β and TNF-α in peritoneal fluid mononuclear cells (PFMCs) were measured with quantitative PCR.Little PAI-1 expression is observed in healthy GCs, whereas GCs of PCOS and atretic follicle exhibit distinct expression in vivo. In vitro study using HGrC1 shows that TGF-β and TNF-α increase PAI-1 mRNA and its activity, and both together exhibit a synergistic effect. The expression of PAI-1 mRNA is suppressed by simvastatin. Moreover, insulin-sensitizing drugs (metformin, pioglitazone, and rosiglitazone) suppress LPS-induced TGF-β and TNF-α mRNA expression in PFMC.Statin and insulin-sensitizing drugs may provide a potential therapy for PCOS via down-regulation of PAI-1 expression in GCs and down-regulation of TGF-β and TNF-α expression in PFMC, respectively.