The fold change in ADAMTS4 (panel A) or ADAMTS5 (panel D) mRNA copy number of chondrocytes preincubated without (Ctr) or with chemical inhibitors: Helenalin (Hele), SB203580 (SB), PD98059 (PD) or LY294002 (LY), 60 minutes prior to, and during 24 addition hours of incubation in the absence (−) or presence (+) of 250 μg/ml HA oligosaccharides. Values shown represent average ± S.D. of data derived from triplicate cultures. Conditioned medium from chondrocytes preincubated without (−) or with chemical inhibitors, 60 minutes prior to, and during 24 addition hours of incubation in the absence (Ctr) or presence of 250 μg/ml HA oligosaccharides (+ HA-oligos) were analyzed by western blotting and probed using anti-bodies specific for ADAMTS4 (panel C) or ADAMTS5 (panel D).