SEM and TEM study of the hierarchical structure of C57BL/6J and C3H/HeJ mice trabecular bone.

Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the hierarchical structure of trabecular bone from C57BL/6J (low bone mass) and C3H/HeJ mice (high bone mass). Bone was harvested from two different anatomical locations: femoral metaphysis and L5 vertebra. This investigation focused on three structural scales: the mesostructural (porous network of trabecular struts), the microstructural (collagen fibril arrangements in trabecular packets), and the nanostructural (collagen fibril and apatite crystals) levels. At the mesostructural level, no distinct differences were found in the trabecular structure of femoral metaphysis but thinner trabecular struts were observed in L5 vertebra for C57BL/6J mice strain. At the microstructural level, the collagen fibrils forming the rotated, twisted, and orthogonal plywood arrangements were distinguished as well as atypical arrangements. At the nanostructural level, the shape and size of apatite crystals, and their arrangement with respect to collagen fibrils were studied. In spite of very different bone mass densities, both mice strains had similar structures at the nanostructural and microstructural levels.

TEM analysis of the nanostructure of normal and osteoporotic human trabecular bone.

Transmission electron microscopy (TEM) was used to investigate the crystal-collagen interactions in normal and osteoporotic human trabecular bone at the nanostructural level. More specifically, two-dimensional TEM observations were used to infer the three-dimensional information on the shape, the size, the orientation, and the alignment of apatite crystals in collagen fibrils in normal and osteoporotic bone. We found that crystals were of platelet shape with irregular edges and that there was no substantial difference in crystal length or crystal thickness between normal and osteoporotic trabecular bone. The crystal arrangement in cross-sectioned fibrils did not neatly conform to the parallel arrangement of crystals seen in longitudinally-sectioned fibrils. Instead, the crystal arrangement in both normal and osteoporotic trabecular bone took on more of a random, undulated arrangement, with certain localized areas demonstrating circular oriented patterns. The TEM imaging was done using bright fields only. Thus, the results presented are within the limitations of this approach.