Transforming growth factor (TGF)-beta 1, a cytokine released into the cerebrospinal fluid (CSF) after intraventricular hemorrhage (IVH), stimulates the expression of the components of the extracellular matrix (ECM), which causes progressive ventricular dilatation by impaired CSF absorption. Matrix metalloproteinase-9 (MMP-9), a proteinase involved in the removal of ECM proteins, has been shown to contribute to the resolution of progressive ventricular dilation after IVH. The aim of this study is to Clarify the mechanism by which MMP-9 is expressed following IVH. Cultured human meningeal cells were treated with human recombinant TGF-beta 1. RT-PCR demonstrated that TGF-beta 1 induced MMP-9 expression in the meningeal cells in a dose-dependent manner. The TGF-beta 1-induced MMP-9 expression was attenuated in the presence of either MEK or Smad 3 inhibitor. Our data indicated that MMP-9 is released into the CSF from meningeal cells in response to TGF-beta 1, most probably through the activation of ERK and Smad pathways. (C) 2009 Elsevier Inc. All rights reserved.