Crystallite size in the BAp c-axis and Young’s modulus in femurs of female wild-type and Ocn–/–mice at 9 months of age.

(A) The crystallite size in the BAp c-axis in the longitudinal and vertical directions at position 5. (B) Young’s modulus along the bone longitudinal axis at position 5 in Fig 6A as measured by nanoindentation. **: P<0.01. X symbols in box plots show outliers. (C) Single regression analysis of Young’s modulus to BMD and each degree of the preferential alignment of collagen fibers and the BAp c-axis in the bone longitudinal direction at position 5. wt: blue dots, Ocn–/–: red dots. wt: n = 5, Ocn–/–: n = 6. (D) Schematic presentation of orientations of collagen fibrils and BAp c-axis. In wild-type mice, the orientations of collagen fibrils and BAp c-axis are parallel to the bone longitudinal axis. In Ocn–/–mice, the orientation of collagen fibrils is parallel to the bone longitudinal axis, whereas that of BAp c-axis is severely disrupted from the longitudinal axis. The disruption of the BAp c-axis orientation reduces Young’s modulus in the longitudinal axis.