Figure 4.

IGF-1-mediated suppression of noggin and stimulation of aggrecan are via the PI3K/Akt pathway. A. Serum-starved NP cells were stimulated by IGF-1 (100 ng/ml) for the indicated periods of time. Cell lysates were then prepared and analyzed by western blotting with specific anti-phospho-Erk and anti-phosph-Akt Ser⁴⁷³ antibody. β-actin was used as a control for normalization. B and C. The cells were treated with IGF-1 (100 ng/ml) in the presence or absence of Erk/MAPK pathway-specific inhibitor (PD98059, 25 µM), PI3K/Akt pathway-specific inhibitor (LY294002, 50 nM). The cells were harvested 24 hrs after the initiation of each treatment to perform real-time PCR (B, aggreccan; C, noggin). β-actin was used as a control for normalization. The data represent three different donors measured in triplicate for each experiment. Analysis of variance was performed using StatView 5.0 software (SAS Institute, Cary, NC). P-values lower than 0.05 were considered significant. Three independent experiments in triplicates were performed.