FIG. 6.

Effect of streptococcal M protein and protein F1 on up-regulation of RANKL mRNA in infected osteoblasts. Osteoblasts were cultured without stimulant (None) or with PGE2 (2 μM) (PGE₂) or were infected with S. pyogenes JRS4 (M6⁺ F1⁺) (WT), JRS145 (M⁻ F1⁺) (M⁻), or SAM1 (M6⁺ F1⁻) (F ⁻) for 6 h. Total RNA was extracted and subjected to RT-PCR for RANKL and β-actin analysis (A) and RANKL mRNA was quantified by real-time PCR (B). The values are the means ± standard deviations for triplicate assays and are percentages of the RANKL mRNA level in osteoblasts stimulated with PGE2 (PGE₂). An asterisk indicates that the P value was <0.05 for a comparison with the RANKL mRNA level in cells cultured in the absence of the stimulant.