Quantitative RT-PCR analysis of the mRNA expression of Tnfsf11 in calvarial bones incubated for 24 h without or with BK (1 μM), DALBK (1 μM), IL-4 (30 ng·mL−1 and IL-1β (100 pg·mL−1) in different combinations. The values represent means ± SEM for 5–6 bones per group. The statistically significant effects are shown by asterisks (*, P < 0.05; **, P < 0.01; ***, P < 0.001).