Figure 3. Effects of circulatory factors on catabolic gene expression in intervertebral discs obtained from mouse heterochronic parabionts. Levels of disc MMP13 protein (A) MMP13 mRNA, (B) ADAMTS4 protein, (C) ADAMTS4 mRNA, and (D) were quantified by Western blot and qRT-PCR. Graphs on the right of the Western blots show the relative levels of MMP13 and ADAMTS4 protein normalized to actin. Data shown are mean ± SD of 5 independent experiments for RT-PCR and 4 experiments for Western blot, *p < 0.05.