FIGURE 6. GADD45β is required for hypertrophic chondrocyte differentiation in vitro and associated expression of Mmp-13 and Col10a1 mRNA.
A, murine rib growth plate chondrocytes were infected with lentivirus encoding siRNA-GFP to generate GFP KD cells or with siRNA-GADD45β to generate GADD45β KD cells and cultured as three-dimensional pellets for 3, 14, and 21 days. Toluidine blue staining showed the progressive hypertrophy in cultures of GFP KD chondrocytes but not in the cultures of GADD45β KD chondrocytes. Magnification is ×40. B, after 21 days of culture, toluidine blue (T.Blue) staining and the levels of Col10a1 and Mmp-13 mRNA, detected by in situ hybridization using antisense probes, were markedly decreased in GADD45β KD compared with GFP KD cells. Magnification is ×200.