Fig. 6. TGFβ1 protects chondrocytes against oxidative stress–induced cell death via FOXO1.

Human chondrocytes were transfected with siCtrl or siFOXO1. After incubation with or without TGFβ1 for 3 hours, H₂O₂ was added to each well to a final concentration of 0, 100, or 250 μM for 48 hours. (A) Cell viability was analyzed by MTT assay; n = 10 independent experiments. (B) ATP production was analyzed using the CellTiter-Glo assay; n = 9 independent experiments. Data are expressed as the percent absorbance (A) or luminescence (B) of cells in each group relative to cells transfected with siCtrl, and not treated with TGFβ1 and H₂O₂. Human chondrocytes were transfected with siCtrl or siFOXO1. After incubation with or without TGFβ1 for 3 hours, H₂O₂ (0 or 250 μM) was added to each well. After 48 hours, cell apoptosis was analyzed by TUNEL assay (C). Higher-magnification views are corresponding to the white boxed areas in each group. Graph shows the percentage of TUNEL positive cells; n = 5 independent experiments. Data are presented as dots showing individual values and as means ± S.D. Statistical analysis was performed using one-way repeated measures ANOVA with the Tukey–Kramer post hoc test. *P < 0.05.