Sustained static compression induces consistently decreased expression of antiapoptotic proteins in intervertebral disc cells. (A) Representative immunohistochemical sections for B-cell lymphoma 2 (Bcl-2), silent mating-type information regulation 2 homolog 1 (SIRT1), and negative control in the loaded disc nucleus pulposus (NP) and annulus fibrosus (AF) at 0, 7, 28, and 56 days of loading (bars, 50 μm). (B) Changes in the percentage of Bcl-2-positive cells and SIRT1-positive cells in the NP and AF at 0, 7, 28, and 56 days of loading. Data are mean ± standard deviation (n = 6). Two-way analysis of variance with the Tukey-Kramer post hoc test was used. *P < 0.05 when compared between loaded and unloaded conditions. †P < 0.05 when compared between different time points.