Figure 5

Bone resorption markers are increased in rat models of OA. (A) Up-regulated expression of Cat K and TRAP (a) Cat K levels progressively increased by 2 to 4-fold in ACLT and ACLT-MMx, respectively, versus Sham. (b) Similarly, time-dependent upregulation of TRAP expression peaked at 2 to 3 fold in ACLT and ACLT-MMx, respectively. All values are shown as mean ± SD. (B) Immunolocalization of osteoclastic markers (MMP-9 and Cat K) in ACLT-MMx joint at 2-wk after surgery. (a-d) Frontal section of medial tibial plateau and growth plate were stained with anti-Cat K (brown) and anti-MMP-9 (red). (a) At 2-wk post-surgery, irregular articular surface is observed (arrow). Cat K positive multinucleated cells detected on trabecular bone surface in bone marrow (arrowheads). (b) Cat K positive cells invading into articular cartilage are found in proximity to MMP-9 (red) staining (open arrowhead) with higher magnification of squared area in (a). (c) Negative control shows no specific staining. (d) Growth plate and primary spongiosa, stained as positive control, demonstrated Cat K positive cells in proximity to MMP-9 stained region in the border of cartilage and primary spongiosa. C: articular cartilage. B: bone. GP: growth plate. PS: primary spongiosa. Bar = 500 μm in (a, c); 50 μm in (b, d).