Figure 4. Bone tissue characteristics.

(A) Quantitative backscatter electron imaging (qBEI) of the transiliac bone biopsy samples. Top: There is no clear separation between the trabecular and cortical compartment. Pixel gray levels correspond to mineral content (bright to higher and dark to lower). Scale bars: 200 μm; 100 μm (zoom). Nonmineralized Sharpey’s fibres are infusing the cortex (solid white arrows, zoomed-in areas), clearly identified by polarized light microscopy (see C). Bottom: Bone mineralization density distribution (BMDD) curves for the 2 patients. Ref, reference BMDD for children (66). BMDD for cancellous bone showed reduced mineral content, increased heterogeneity in matrix mineralization, and highly increased portion of lowly mineralized bone. In cortical bone of patient F1-1, the BMDD showed a peak shift to higher mineralization due to increased proportion of primary bone mineralized to a higher extent. In patient F2-1, the cortical bone mineralization was overall reduced. (B) Confocal laser scanning microscopy (CLSM) of fluorescence labeled bone. Left: CLSM image of a mineralizing surface shows diffuse appearance of double labeling. Right: Corresponding qBEI image (identical bone area; scale bar: 200 μm). Of note, the osteocyte lacunae are enlarged and of abnormal shape. (C-E) Polarized light microscopy of the bone samples. Paired images of bright-field (right) and linear polarized (left) light (scale bars: 100 μm). (C) Cortical detail of patient F1-1 (region close to zoomed-in area of A): predominantly woven bone infused with Sharpey’s fibres (thin white and black arrows) and bone formation (thick empty black and white arrows) and resorption (thick black arrow in C and thick empty white arrows in A). Of note, the new osteoid does not show a lamellar fibril arrangement. (D and E) Examples of bone tissue with coexisting woven and lamellar bone matrix. Of note, an osteon (arrows) has woven character in the center though at the peripheral region it is lamellar.