The effects of mechanical stability on the macromolecules of the connective tissue matrices produced during fracture healing. II. The glycosaminoglycans.

The glycosaminoglycans secreted into the matrices associated with fractures of the rabbit tibia healing under stable and unstable mechanical conditions have been characterized histochemically using the dye Alcian Blue at pH 5.7 in the presence of increasing concentrations of magnesium chloride, and after enzymatic extractions. These results are compared with those of immunohistochemical experiments using monoclonal antibodies which recognize epitopes specific to various glycosaminoglycans. The results indicate that the fibrous tissues, including those of the cavities of the cancellous bone and periosteum, possess hyaluronate and chondroitin sulphate, but the amounts present are small. The glycosaminoglycans detected in the cortical bone are located mainly around the osteocyte lacunae where chondroitin and keratan sulphates are found. The developing trabeculae of cancellous bone in the callus contain chondroitin and keratan sulphates, but as the trabeculae mature, these glycosaminoglycans are no longer present throughout the matrix; they are found particularly around the osteocyte lacunae. The cartilage in the callus of mechanically unstable fractures contains chondroitin, chondroitin-4- and 6-sulphates and keratan sulphate, through their distribution is variable. The small, transient areas of cartilage in the callus of mechanically stable fractures also contain those glycosaminoglycans, but they appear to be less highly sulphated. The mechanical stability of the fractures appears to affect the amount and degree of sulphation of the glycosaminoglycans, rather than the types of glycosaminoglycan produced. The glycosaminoglycans produced during fracture healing are compared with those produced during embryonic development and other healing processes.