FIGURE 1.

Shear stress mediates the temporal regulation of MMP-9 and IL-1β mRNA and protein expression in human chondrocytes. T/C-28a2 chondrocytes (A, C, and D) or human primary articular chondrocytes (B) were subjected to fluid shear stress (20 dynes/cm²) or static conditions (0 dyne/cm²) for the indicated time intervals. A and B, MMP-9 mRNA and activity levels were determined by qRT-PCR and zymography, respectively. GAPDH and MMP-2 served as internal controls in qRT-PCR and zymography assays, respectively. C and D, IL-1β mRNA expression and secretion were determined using qRT-PCR and an IL-1β enzyme immunoassay kit, respectively. GAPDH and total protein in the medium served as internal controls for the qRT-PCR and IL-1β enzyme immunoassay, respectively. Data represent the mean ± S.E. of three independent experiments. *, p < 0.05 with respect to static control.