Figure 2

Effect of bone morphogenetic protein-2 (BMP-2) overexpression on mRNA levels of extracellular matrix molecules and proteoglycan (PG) synthesis. (a,b) Relative expression of mRNA levels of extracellular matrix molecules. Cartilage of mice injected with either Ad-BMP-2 or Ad-luc was isolated after 3, 7, and 21 days. Cartilage was pooled per group per time point, and RNA was isolated. Cycle threshold values were first corrected for GAPDH and then for the viral control, after which the fold increase/decrease was calculated. Decreases in mRNA levels compared with controls are on the negative scale. BMP-2 induced elevated levels of collagen type II and aggrecan. No changes in collagen type X expression were found. (c,d) Effect of BMP-2 overexpression on PG synthesis. Murine knee joints were injected with either Ad-BMP-2 or a control virus. Cartilage was isolated 3, 7, or 21 days after viral injection and incubated with ³⁵SO₄^2-, after which the amount of incorporation was measured (a). To perform autoradiography, mice were injected with ³⁵SO₄^2- intraperitoneally prior to knee joint isolation, which was performed 3, 7, or 21 days after viral injection. (b) These data show that BMP-2 stimulation of cartilage results in increased synthesis of PGs. Statistical analysis with a Student t test. *p < 0.05; **p < 0.005; ***p < 0.0005. N.D., not detectable.