Bone mineral composition variations in diseased versus normal mice

The mineralogy of bone tissues has important implications for bone physical and chemical properties. We employed Raman spectroscopy to study bone bioapatite in the femurs of healthy mice and those with hypophosphatemia - a genetic disorder that creates a phosphate deficiency and results in lower bone mineralization (Tommasini et al. 2014). Specifically we focused on the changes in the carbonate content of healthy, wild-type mice (WT) and hypophosphatemic mice (HYP) when the bone has undergone increased remodeling due to pregnancy and lactation. All mice were 5 months old at sacrifice and were reared under the same conditions. Raman spectra were collected from cross-sections of mice femurs embedded in poly (methyl methacrylate). Six areas located in the compact bone were examined for each bone, four sites on the bone midshaft, two on either side of the midshaft, and two sites at the end of the bone (epiphysis). As bone is a very inhomogeneous material 16 individual spectra were collected in each area and the results compiled to obtain a representative average of the bone composition. The contribution of the carbonate symmetrical stretching peak at 1074 cm-1 was determined using the method described in Awonusi et al. 2008. The results show that control, pregnant and lactating HYP mice have an increased amount of carbonate associated with their bone bioapatite in comparison to similar WT mice. Higher carbonate content corresponded to a larger full width half maximum of the phosphate 960 cm-1 peak indicating a lower crystallinity in the midshaft of the HYP mice. This study demonstrates that Raman spectroscopy can be a valuable tool for examining the mineralogical differences between healthy and diseased bone.