Immunohistochemical staining for adiponectin receptor type 1 and type 2. Representative cartilage slides showed the expression of AdipoR1 or AdipoR2 (aA, original magnification × 100). A nonlesional cartilage area revealed weakly AdipoR2-positive chondrocytes, but not AdipoR1-positive chondrocytes. In a lesional cartilage area, AdipoR1 was stained mainly in the superficial layer (weak to strong staining intensity), whereas AdipoR2 was stained in both superficial and deep layers of the lesional cartilage (strong staining intensity). The insert is a magnified view (×400) of the area indicated by a red box. When compared between nonlesional and lesional areas, the expression levels of these two receptors significantly increased in lesional areas (B, †P < 0.05 by Wilcoxon matched-pairs signed-rank test), and the increased rate of AdipoR1 (4.2 times) was as twice as high as that of AdipoR2 (2.1 times).