Relative gene expression of genes associated with apoptosis. Relative gene expression of caspase 3 (CASP3), B-cell lymphoma 2-associated X/B-cell lymphoma 2 (BAX/BCL2) ratio in the nucleus pulposus (NP) (open bars) and the annulus fibrosus (AF) (filled bars) injected with a sucrose buffer (sham), 2.5 μg, 25 μg, or 250 μg rhBMP-7, were indicative of an anti-apoptotic effect of 250 μg rhBMP-7. The sham-treated NP was used as a reference and was set at 1 (dashed line). Data are expressed as n-fold change ± SD. ** Indicates a significant difference at a 99% confidence interval (CI); filled circle indicates a significant difference at a 96% CI.