Fig. 5. Inhibition of adipogenesis of Runx2^–/– chondrocytes by soluble differentiation factors. Runx2^–/– primary chondrocytes were plated at a density of 1x10⁵ cells/well (5x10⁴ cells/cm²) in 24 multi-well plates. Two days after inoculation, the cells were further cultured for 10 days without (control) or with a factor including TGF-ß (1 ng/ml), retinoic acid (RA) (10^–8 M), IL-1ß (10 ng/ml), PDGF (200 ng/ml), bFGF (10 ng/ml), IL-11 (100 ng/ml), PTH (10^–7 M), BMP-2 (50 ng/ml), IGF-1 (100 ng/ml) or T3 (10^–7 M), and stained with oil red O or Alcian blue. After culture, the cells were replated for the examination of type II collagen expression by immunocytochemistry. Magnification: phase contrast, oil red and Alcian blue, x50; type II collagen, x100.