Bone Abstracts

Objectives: Most osteolytic tumors are in fact mixed and contain an osteoblastic component associated with the predominant osteolytic areas. This metaplastic woven bone can be evidenced on X-rays as blurred white areas but is always evidenced by histological analysis even in the absence of radiological expression. Metaplastic bone formation reflects the activation of new osteoblasts, the stimulation of the dormant lining cells due to the release of growth factors buried in the bone matrix during the osteoclastic resorption. The production of bone matrix by malignant cells has also been advocated.

Materials and methods: Twelve patients with secondary metastases of the iliac crest evidenced by hot spots on a ⁹⁹Tc-MBP san were diagnosed by histomorphometry on bone biopsies. Fourier transformed infrared analysis and imaging (FTIRI) was used on 4 μm thick sections of undecalcified bone. The mineral, the collagen and the cross links ratio (1660:1690/cm bands) were determined. The matrix characteristics were analyzed and imaged in the ‘old’ residual bone and in the newly formed woven bone in the vicinity of the tumor cells. Imaging was done after peak selection and transfer of the selected files into the MalLab software.

Results: FTIRI provided images of the phosphate, amide and combination of peak ratio after having selected the peaks of interest. In addition, the matrix properties can be measured and compare between the old and newly formed bones. Woven bone appeared poorly calcified with a low phosphate:amide ratio (P=0.03) crystallinity (P<0.0001) and carbonate substitution (P=0.003). Collagen was less mature as evidenced by lower cross-links (P=0.01).

Conclusions: Woven bone observed in normal conditions (fetal bone and callus) is known to be highly mineralized by the process of matrix vesicles. Woven bone associated with bone metastasis appears on the contrary poorly mineralized and rapidly elaborated by osteoblasts. The collagen matrix has a low level of reticulation. FTIRI is a powerful tool to measure and visualize the various components of the bone matrix in human diseases.