Fig. 4

Ros. A induces differentiation by modulating MMP-13. Primary chondrocytes were left untreated or were treated with 75 μg/mL rosmarinic acid (Ros. A) in the absence or presence of 10 μM MMPI or 113 nM MMP-13 inhibitors for 24 h. a Type II collagen, COX-2, MMP-13, pERK, pP38, and actin were detected by western blotting. Actin was used as a loading control (left panel). The relative amounts of proteins (Type II collagen, COX-2, MMP-13. pERK, pp38) were quantified by densitometry measurements (Image J) (right panel). b Sulfated proteoglycan synthesis was detected by alcian Blue staining (upper panel). Prostaglandin E₂ (PGE₂) production was measured using a PGE₂ assay kit (lower panel). c Type II collagen and COX-2 expression was detected by immunocytochemistry. The results represent three independent experiments. Values shown are the means ± SD; *p < 0.05 compared to the control; # < 0.05 compared to the Ros. A