Relative gene expression of matrix-related target genes and DNA, glycosaminoglycan (GAG), and collagen content in intervertebral discs (IVDs) injected with rhBMP-7. A. GAG/DNA and collagen/DNA did not significantly differ between the treatments. GAG/DNA in the nucleus pulposus (NP) (open bars) was significantly higher than in the annulus fibrosus (AF) (filled bars). B. Relative gene expression of collagen type 2 alpha 1 (COL2A1) and collagen type 1 alpha 1 (COL1A1) did not significantly differ between treatments. Gene expression levels of COL2A1 were significantly higher in the NP than in the AF, whereas the expression levels of COL1A1 were significantly lower in the NP than in the AF. GAG/DNA and collagen/DNA are expressed as mean ± SD, and COL2A1 and COL1A1 as relative expression ± SD. **Indicates a significant difference at a 99% confidence interval (CI).