Strontium does not affect the intrinsic bone quality at tissue and BSU levels in iliac samples from Macaca fascicularis monkeys

- At bone structural unit level, bone strontium content increased dose dependently regardless of time between sacrifice and end of treatment.
- Bone strontium content did not alter the positive correlation between the degree of mineralization of bone and the microhardness.
- Chemometric analyses confirmed that presence of strontium did not affect surrogates of nanostructural quality of organic and mineral bone components.
- Presence of strontium in bone matrix had no significant effects on chemical and local mechanical properties of bone tissue.

Our purpose was to evaluate the impact of strontium ranelate (SrRan) on bone mineral quality at both tissue and bone structural unit (BSU) levels. Thirty iliac bone samples (dehydrated then embedded) were taken from monkeys who received 0 (controls), 200, 500 or 1250 mg/kg/day of SrRan for 52 weeks and were sacrificed either at the end of administration (treated animals, n = 16) or 10 weeks later (reverse animals, n = 14). Degree of mineralization (DMB), heterogeneity index of mineralization (HI), Vickers microhardness (Hv) and focal bone strontium content (BSC) were measured globally at tissue level and focally on the same 923 BSUs. Mineral and collagen characteristics, as well as chemometric analyses were performed on younger and older tissues in cortical bone and cancellous bone in 737 other BSUs. At tissue level, SrRan preserved material properties. At BSU level, BSC increased (significant) dose dependently in treated and reverse animals. DMB and Hv were greater in older than in younger bone in controls and treated animals. In treated animals, DMB was positively correlated with Hv and inversely correlated with the BSC. Thus, younger BSUs were less mineralized and less hard than older BSUs independently from the presence of strontium. Mineral maturity, crystallinity index, mineralization index, carbonation and collagen maturity were not modified by SrRan. Chemometry confirmed the absence of a direct effect of strontium on mineralization. Thus, surrogates of micro- and nano-structural mineral properties were not altered by SrRan and remained at a physiological level.