BONE INJURY RESPONSE - AN ANIMAL-MODEL FOR TESTING THEORIES OF REGULATION

Therapeutic treatment of bone disease and attempts to accelerate norma l healing require knowledge of the soluble factors that control bone r epair and the specific effects that they produce. To facilitate study of this regulatory system, an animal model involving creation of a hol e in the cortex of the rat tibia was developed, Proliferation, differe ntiation, and callus formation at the injury site were measured more p recisely than in previous animal models by means of autoradiographic, histologic, histochemical, and morphometric methods. Several novel fea tures of bone healing were observed, including the following: (1) synt hesis of bone matrix in the defect occurred only after a cambial compa rtment was established by regeneration of the fibrous periosteum and ( 2) at least 3 kinds of osteoblasts could be distinguished depending on when and where deposited calcifiable matrix, The model is well suited to evaluating the use of interventional strategies that involve chemi cal or electrical agents because the cellular parameters of interest c an be measured precisely.