Effect of adiponectin on the degradation of osteoarthritis (OA) cartilage matrix. IL-1β (5 ng/ml) significantly increased the concentrations of collagenase-cleaved type II collagen neoepitope (C1-2C) in conditioned media collected on days 4 and 8 (n = 4, duplicate, P < 0.05 for both). Adiponectin (30 μg/ml) also showed increased the C1-2C levels in the media on day 8 (P < 0.05). The histogram with error bars represents the mean and the standard error of the mean. †P < 0.05 by Mann-Whitney test.