Fig. 6

a Representative histological image of TRAP-positive osteoclasts (arrows) within the callus tissue of a control mouse at 2 weeks after surgery. Scale bar: 20 μm. b TRAP-positive osteoclasts/HPF within the callus tissue of controls (white bars, n = 8 at 2 and 5 weeks, n = 10 at 10 weeks) and sildenafil-treated mice (black bars, n = 8 at 2 and 5 weeks, n = 10 at 10 weeks) at 2, 5 and 10 weeks after surgery, as assessed by histological analysis. Mean ± SEM; *p < 0.05 vs. control