<p>MSCs-<i>TetR</i>/<i>Amelx</i> at 8 passages were cultured in the growth medium (Con) or osteogenic induction medium (Os). Dox was applied to MSCs-<i>TetR</i>/<i>Amelx</i> on day 0–10 (<b>a</b>: early stage), day 10–20 (<b>b</b>: intermediate stage), or day 20–30 (<b>c</b>: late stage) of osteogenic differentiation, and Alizarin Red S staining was performed at day 10, day 20, or day 30, respectively. The staining intensity was also quantitatively analyzed. Significant differences (*<i>P</i><0.01: ANOVA with Tukey’s multiple comparison test: n = 9) are shown.</p
