Figure 4. Decreased bone mineralization in Vdr^int– mice.

(A) Calcium amount, expressed as a percentage of tibial dry weight (both in milligrams). n = 10. (B and C) Goldner staining showing osteoid on the trabeculae (arrow; B), cortical surfaces (C), and resorption cavities (arrow; C) and surrounding the osteocytes (arrowhead; C, inset) in Vdr^int– mice. Quantification of osteoid surface (OS/BS) and thickness (O.Th) is also shown in B. n = 8. Scale bars: 50 μm; 10 μm (insets). (D) BSE of a cortical osteocyte (oc), which was directly enclosed by the mineralized matrix (m) in Vdr^int+ mice, but surrounded by a hypomineralized area (p) in Vdr^int– mice. n = 3. Scale bar: 2 μm. (E and F) Semiquantification (counts per second [cps]) of Ca (E) and P (F) by energy dispersive X-ray point analysis in the regions indicated in D. n = 3. (G and H) Quantification of cortical BMD by μCT along a line from the endosteal to the periosteal side (G; note decreased Ct.Th in Vdr^int– mice) and in a predefined region (H). n = 8. (I) BSE image of the diaphyseal cortex showing hypomineralization of the periosteal bone in Vdr^int– mice, reflected by the darker gray starting from the black arrow up to the outer cortex (white arrow), but not in control mice. Scale bar: 50 μm. (J) Analysis of dynamic bone formation parameters by sequential injection with calcein showing normal double label formation (double-sided arrow) in Vdr^int+ mice. Scale bar: 25 μm. **P < 0.01, ^#P < 0.001 vs. Vdr^int+.