Fig. 1.

Bone formation in WT and TPH₁^−/− mice during growth and maturity. Static and dynamic histomorphometric parameters were measured in 6- and 16-wk-old animals. (A) Bone formation rate/bone surface (BFR/BS) and (B) osteoblast surface / bone surface (OB/BS) were unchanged in both genotypes (WT, black bars; TPH₁^−/−, white bars) at 6 wk and were reduced at 16 wk. (C) Biochemical markers of bone formation. Serum osteocalcin levels were determined when the mice were 6 and 16 wk old. No significant difference was observed when the mice were 6 wk old, whereas a significant decrease in the osteocalcin level was observed when they were 16 wk old. (D) Proliferation was assessed after a 3-d culture period by BrdU incorporation in WT and TPH₁^−/− calvarial osteoblasts, and no difference was observed. (E) The capacity of WT and TPH₁^−/− primary osteoblasts to produce mineralized nodules was determined by alizarin staining after 18 d in culture, and no difference was observed. Data are shown as mean ± SEM; n = 8 mice per genotype. *P < 0.01 versus WT, **P < 0.001 versus WT, ***P < 0.0001 versus WT.