Fig. 4

Absence of Tgif1 in the bone microenvironment reduces the number and activity of osteoblasts in vivo.a Schematic presentation of the experimental outline to investigate the role of Tgif1 in the bone microenvironment using 8-week-old mice with a germ line deletion of Tgif1 (Tgif1^−/−) or control littermates (Tgif1^+/+). b Representative images of von Kossa-stained sections of the tibiae (top panel) and of fluorescence double labeling (lower panel) from Tgif1^+/+ and Tgif1^−/− mice. Scale bars indicate 1 mm (black) and 20 μm (white). c Representative images of toluidine blue-stained sections of the tibiae demonstrating the reduction of osteoblasts (red arrows) lining trabecular bone surfaces in Tgif1^−/− mice compared to Tgif1^+/+ mice. Scale bar indicates 20 μm. d Representative images of the bone marrow vasculature. Tibia sections from Tgif1^+/+ and Tgif1^−/− mice were stained for Endomucin to visualize vessels. GP, growth plate. Scale bar indicates 100 μm. e–l Histomorphometric analysis of trabecular bone mass (e), mineralized bone surfaces (f), osteoid volume (g), bone formation rate (h), osteoid surface (i), osteoblast number (j), osteoblast surface (k), and the number of osteoclasts (l) in Tgif1^+/+ and Tgif1^−/− mice (n = 5–10 mice/group). BV/TV, bone volume/tissue volume; MS/BS, mineralizing surface/bone surface; OV/BV, osteoid volume/bone volume; BFR/BS, bone formation rate/bone surface; OS/BS, osteoid surface/bone surface; N.Ob/BS, number of osteoblasts/bone surface; Ob.S/BS, osteoblast surface/bone surface; N.Oc/BS, number of osteoclasts/bone surface. m Serum TRAP5b concentration measured by enzyme-linked immunosorbent assay (ELISA) (n = 3–6 mice/group). n–p Number (n), size (o), and length (p) of Endomucin-positive bone marrow vessels were analyzed using 3–4 non-serial sections of the tibiae per mouse. Data are presented as mean ± SEM. Two-tailed Student’s t test was used to compare the two groups; **p < 0.01, ***p < 0.001