Fig. 4. Inhibition of adipogenesis by the adenoviral introduction of Runx2 in Runx2^–/– chondrocytes. Runx2^–/– chondrocytes infected with either EGFP-expressing (GFP) or Runx2-and-EGFP-expressing (Runx2) virus were cultured for 12 days and stained with oil red O (A), cultured for 6 days and harvested for northern blot analysis (B), or cultured for 15 days and harvested for real-time RT-PCR analysis at indicated days (C). Phase-contrast images are shown in (A) (x50). In northern blot analysis, 20 µg of total RNA were loaded in each lane and hybridized with mouse type II collagen or PPAR cDNA (B). The gel stained with ethidium bromide is shown as an internal control. In real-time RT-PCR analysis, Runx2 and type X collagen expression were examined (C). EGFP-expressing and Runx2-and-EGFP-expressing adenovirus infection are shown by open circles and closed circles, respectively. The value of Runx2 or type X collagen in Runx2-and-EGFP-expressing adenovirus infection on 15-day culture was defined as 1, and relative values are shown. Data represent the mean of three wells. *P<0.05 as determined by one-way ANOVA. Similar results were obtained in three independent experiments and representative data are shown.