Fig. 5

a–f Representative histological images of Safranin-O-stained femora in controls (a–c) and sildenafil-treated mice (d–f) at 2 (a, d), 5 (b, e) and 10 weeks (c, f) after surgery. Fibrous tissue (ft), cartilaginous tissue (ct), woven bone (wb) and cortical bone (cb) are indicated. Scale bars: 0.5 mm. g–i Total callus area (mm²) of femora 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 (g), 5 (h) and 10 (i) weeks after surgery. j–l Callus composition (%), including fibrous tissue (white), cartilaginous tissue (gray) and osseous tissue (black), of femora of controls (n = 8 at 2 and 5 weeks, n = 10 at 10 weeks) and sildenafil-treated mice (n = 8 at 2 and 5 weeks, n = 10 at 10 weeks) at 2 (j), 5 (k) and 10 (l) weeks after surgery. Mean ± SEM; *p < 0.05 vs. control