Fig. 4

Synchrotron SAXS/WAXD shows altered collagen and mineral behavior in TβRII^ocy−/− bone during in situ tensile testing. a Synchrotron-generated X-ray exposure during tensile testing of the forearm bones of TβRII^ocy−/− and Cre-negative controls at multiple ages generates signals unique to organic collagen (SAXS) and the inorganic mineral components (WAXD) of bone based on their hierarchical size, order, and structure. The summation of composite strains (b) reveals deficiencies in the ability of collagen and minerals to carry tissue-level strains in young, male TβRII^ocy−/− and aged, female Cre-negative controls. Compared to Cre-negative controls, young TβRII^ocy−/− males showed a deficiency in collagen strain capacity (c) that recovered with age (d). Female TβRII^ocy−/− mice did not show this weakness at young ages (e). With age, female Cre-negative controls showed a decrease in collagen strain, while TβRII^ocy−/− did not, resulting in significant differences in collagen strain between these two groups (f). The mineral strains in young male bones showed genotype-dependent differences (g) that did not change with age (h), while females did not show genotype differences at either age studied (i, j). *P < 0.012 5 for 4-way Bonferroni correction in comparisons of regression slopes in an extra sum-of-squares F test. n = 5-8 per group