Fig. 6

The expression of Sp1 in OA and control cartilage and its significance in the expression of IGF1R and IRS1. a, The expression of SP1 was determined in control (Control) and OA cartilage (OA) in cartilage zones. OA cartilage was obtained from macroscopically intact areas (Preserved) and degenerated areas with various degrees of cartilage degeneration (Degenerated). Results are shown as described in Fig. 1. S, M and D denote superficial, middle and deep cartilage zones, respectively, which are shown by open, shaded and closed bars, respectively. Values are the mean and SE of 6–12 samples. a and b indicate p < 0.05 compared to the corresponding zone in control cartilage, or compared to the corresponding zone in preserved areas of OA cartilage, respectively. b and c, Primary cultured human chondrocytes were infected with adenoviruses encoding SP1, and the expression of IGF1R (b) and IRS1 (c) was evaluated three days later. The expression was normalized to the GAPDH expression and compared to the control cells infected with adenoviruses encoding lacZ. d and e, Two siRNAs for SP1 were introduced into primary cultured human chondrocytes, and expression of IGF1R (d) and IRS1 (e) was evaluated three days later. The expression was normalized to the GAPDH expression and compared to the control cells given control siRNA. Open and shaded bars represent the results of the two different siRNAs for SP1. In B-E, the results are presented as relative ratios. Values are the mean + SE of 4 independent experiments, each triplicate. **, p < 0.01