Eagle’s minimum essential medium (MEM), fetal bovine serum, trypsin-EDTA, and trypan blue were obtained from Invitrogen-Gibco (Osaka, Japan); 24- and 96-well culture plates from Corning Glass Co. (Corning, NY); native porcine type I collagen (acid solubilized) and 5× Dulbecco’s modified Eagle’s medium (DMEM) from Nitta Gelatin (Osaka, Japan); bovine plasminogen, collagenase, dispase, and dimethyl sulfoxide (DMSO) from Sigma-Aldrich (St. Louis, MO); recombinant human IL-1β from R&D Systems (Minneapolis, MN); triptolide from Alexis Biochemicals (Carlsbad, CA); filters (Ultrafree-MC) from Millipore (Bedford, MA); an MMP-1 colorimetric assay kit from Biomol (Plymouth Meeting, PA); synthetic substrate S-2251 for plasmin from Chromogenix (Milan, Italy); nitrocellulose membranes and a chemiluminescence (ECL) kit from Amersham Pharmacia Biotech (Uppsala, Sweden); kits for RNA purification (RNeasy Mini Kit) and polymerase chain reaction (QuantiTect SYBR Green PCR Kit) from Qiagen (Hilden, Germany); a reverse transcription system and a cytotoxicity assay (CytoTox 96 Non-Radioactive) from Promega (Madison, WI). Sheep antibodies to rabbit MMP-1 and -3 were kindly provided by Hideaki Nagase. All media and reagents used for cell culture were endotoxin minimized.