Fig. 5

Inflammatory mediators promote senescent changes in chondrocytes. a–d Chondrocytes were exposed to BP or IL-1β for 24 h. Gene expression analysis was performed for p16 or p21 (A: p16: *P = 0.051 1. B: p21: *P = 0.022 9. C: p16: **P = 0.009 6. D: p21 **P = 0.003 9). Bars represent mean ± SEM for n = 5 independent experiments. e Adeno-GFP or adeno-cre were transduced into IKK2^−/− chondrocytes. Cells were then treated with BP and/or IL-1β for 24 h. After 24 h, protein lysates were collected and immunoblotting was performed for p16-Ink4a. Representative immunoblot image is shown. f Medial and lateral knee articular cartilage was isolated from patients undergoing TKA with medial compartment OA. P16 gene expression was measured by qPCR (P = 0.053 0). Bars are mean ± SD for n = 9 patients. g Medial and lateral knee articular cartilage was isolated from patients undergoing TKA with medial compartment OA. Cartilage tissue was sectioned and IHC was carried out for p16-Ink4a. Image is representative of n = 4 healthy and diseases cartilage sections. h GFP or IKK2ca were retrovirally transduced into chondrocytes. p16 expression was measured by qPCR (*P = 0.012 2). Bars are mean ± SD from n = 4 independent experiments. i IKK2ca was expressed in chondrocytes of adult mice in vivo under the control of the tamoxifen inducible aggrecan-cre (Acan^IKK2ca). Six weeks post induction, mice were sacrificed and joints were embedded in paraffin and sectioned. IHC was performed for p16, with dark stain representing p16 positive cells. Representative images are displayed. j, k IKK2^−/− chondrocytes were transduced with adeno-GFP or adeno-cre. Cells were then treated with BP for 24 h and p16 and p21 gene expression was measured (p16: *P = 0.021 2, n = 2. p21: **P = 0.001 7, n = 4). Bars represent mean ± SD from representative experiment