FIGURE 8.

Normal activation of MAPKs in the mutant articular cartilage. A, immunostaining of paraffin sections for phospho-ERK1/2 (P-ERK), phospho-p38 (P-p38), and phospho-JNK (P-JNK) shows no detectable difference in the activation of MAPKs in control and mutant femoral head chondrocytes at 1 month of age. Results are representative of those seen in five mice of each genotype. B, FN-f stimulation of ERK activation and MMP-13 expression in femoral head explant culture. Shown is representative immunostaining performed on frozen sections of four experiments. At day 0 (d0), ERK is phosphorylated in many control and mutant chondrocytes. MMP-13 staining is visible only in the center of secondary ossification (so) but not in the articular cartilage (ac) of control samples. Due to the delay of terminal hypertrophic chondrocyte differentiation, mutant explants show only restricted MMP-13 deposition in the area of secondary ossification. At day 4 (d4), both control and β1^fl/fl-Prx1cre⁺ samples treated with FN-f show ERK reactivation and MMP-13 expression in the articular cartilage.