MMP-3 has been detected in human placenta and reduced expression of the enzyme was observed in invasive trophoblasts of patients with severe preeclampsia. However, detailed expression pattern, regulation and biological properties of the placental protease have not been elucidated so far. RT-PCR analyses, Western blotting and enzyme activity assays revealed that pro- and active form of MMP-3 were predominantly expressed in purified first trimester villous trophoblasts, in invasive cytotrophoblasts of differentiating explant cultures and in trophoblastic SGHPL-4 cells. Accordingly, immunofluorescene of first trimester placental tissues detected MMP-3 mainly in villous and extravillous cytotrophoblasts. IL-1I?, an inducer of MMP-3 in decidual cells, increased secretion and activity of the protease in trophoblast supernatants in a dose- and time-dependent manner. IL-1I?-stimulated production of the enzyme was suppressed in the presence of inhibitors of MAPK and AKT signalling. Similar to recombinant MMP-3, MMP-3 in supernatants of IL-1I?-stimulated decidual stromal or SGHPL-4 cells degraded IGFBP-1 in vitro resulting in the appearance of cleavage products at approximately 25, 22, 17, 14 and 11 kD. However, cleavage assays using recombinant MMP-2 suggested that the gelatinase may contribute to IGFBP-1 degradation in trophoblast supernatants. Despite its effects on MMP-3 expression IL-1I? failed to significantly alter invasion of SGHPL-4 cells through Matrigel-coated transwells. In conclusion, the data suggest that invasive trophoblast cell models secrete bioactive MMP-3. Inducible expression of the protease involves MAPK and AKT signalling. In addition to the decidua, MMP-3 of trophoblasts may contribute to the regulation of the IGF system by degrading IGFBP-1. A? 2008 Elsevier Ltd. All rights reserved.