STRUCTURAL-ANALYSIS OF PROTEOGLYCANS SYNTHESIZED BY MINERALIZING BONE-CELLS IN-VITRO IN THE PRESENCE OF FLUORIDE

This study investigated the biochemical structure of proteoglycans syn thesized during matrix maturation by mineralizing bone cells in vitro, in the presence and absence of fluoride. Bone cells were obtained fro m rat femur washes and cultured in ex MEM media supplemented with feta l calf serum, ascorbic acid, P-glycerophosphate and dexamethasone. Cel ls were characterized as osteoblast-like by the expression of alkaline phosphatase activity and the synthesis of collagen type I and osteoca lcin. Fluoride, present in the culture media at concentrations of 10(- 5) M or 10(-7) M, had negligible effect on cell viability. However, ca lcium deposition was increased in cell cultures incubated in the prese nce of fluoride. Proteoglycans were extracted from the extracellular m atrix with 4 M guanidinium chloride and purified by anion exchange chr omatography. Biochemical analysis identified the presence of the small leucine rich proteoglycan, decorin and biglycan, in addition to degra dation products relating to the larger chondroitin sulphate protoeglyc an, versican. Fluoride had little effect on the size or amino acid com position of the protein core, but resulted in significant alterations to the GAG chains, including a dramatic reduction in chain length, red uction in sulphation and decrease in the proportion of dermatan sulpha te compared to chondroitin sulphate. The influence of fluoride on prot eoglycan structure synthesized by mineralizing bone cells provides val uable information, indicating specific roles for dermatan sulphate and chondroitin sulphate proteoglycans. The results suggested that fluori de affected the post-translational assembly of the GAG chains which ma y be an influential factor in the mineralization process.