Glycosaminoglycans and proteoglycans of human bone tissue at different stages of mineralization

Using ultracentrifugation, compact bone from a growing 15 years old man was separated into three fractions with different degrees of mineralization. The finely powdered material was fractionated in a density gradient of acetone and bromoform in varying proportions. The glycosaminoglycans were isolated after papain digestion of the tissue fractions. The glycosaminoglycan elution profiles from CPC-cellulose microcolumns indicated the presence of chondroitin-4-sulphate and, possibly, minor traces of hyaluronic acid. The degree of sulphatation was the same in all three fractions, while the total amount and molecular size of the glycosaminoglycans decreased somewhat with increasing degree of mineralization. The glycosaminoglycans of the tissue fractions were also extracted with 4 M guanidinium chloride and then purified chromatographically on DEAE. Gel chromatography of the isolated material showed three different peaks, two probably representing low molecular weight proteoglycans. The proportion of intermediate molecular size material increased with increasing degree of mineralization. The results are discussed briefly in relation to the mineralization process.