FIGURE 4:

Altered cortical bone formation in cKO mice. (A) Fluorescence micrographs of calcein labels on the cortical surfaces of WTfl and cKO femurs at 1 mo of age. Double label is seen only on the endocortical surface of the WTfl bone, whereas abundant double label is seen on the periosteal surface and to a lesser extent on the endosteum of cKO bone. (B) Bone formation rate and (C) mineral apposition rate are decreased on the endosteal surface in cKO bones, whereas they are both significantly higher on the periosteal surface of mutant mice relative to WTfl controls (*, P < 0.05, t-test for unpaired samples, n = 4). (D) Serum osteocalcin levels, from 1-mo-old mice, are significantly increased in the cKO relative to WTfl (*, P < 0.05, t-test for unpaired samples, n = 7–8).