MORPHOLOGICAL AND HISTOCHEMICAL STUDIES OF BONE REPAIR IN RAT

Bone repair was studied in circumscribed holes drilled in either the inferior border of the mandible or on the lateral surface of the femur. Specimens taken periodically after surgery were studied for morphological changes and by using qualitative histochemical methods for certain hydrolytic and dehydrogenase enzymes. Cartilage formation was not found in any site of healing bone. Within 2 or 3 days after surgery, cells of the organizing granulation tissue exhibited intense staining reactions for acid phosphatase, alkaline phosphatase, nonspecific esterase, and for several dehydrogenases; namely, malic, isocitric, glutamic, lactic, alpha-glycerophosphate, DPNH and TPNH but less for succinic dehydrogenase. In general, hydrolytic and dehydrogenase enzyme activity was greatest in osteoclasts, less in osteoblasts, osteoprogenitor cells and cells of organizing granulation tissue, and least in active osteocytes. Many older osteocytes manifested only slight enzyme activity. Less enzyme activity was evident in cells of the internal callus than in cells of the external callus. © 1969.