Oxidative enzymes of intermediary metabolism in healing bone fractures. A histochemical study

Publisher Website
Google Scholar
Abstract
The fibulae of young adult rats were cut at the mid‐diaphysis with scissors and examined at various stages of repair. The distribution of enzymes participating in glycolysis, in the citric acid cycle, and in the hexose monophosphate shunt was studied histochemically in healing bone fractures.Three days after the fracture there was marked proliferation and an increased enzyme activity in the osteoprogenitor cells in the inner layer of the periosteum along the entire diaphysis. Remarkable enzyme activity was also observed in the newly formed osteocytes. No qualitative differences were noticed among osteoprogenitor cells, osteoblasts, and osteocytes. Necrotic muscle fibers, periosteum, and bone cells failed to react.Seven days after the fracture, a bulky cartilaginous callus developed. The proliferating osteoprogenitor cells of the periosteum and of the callus had a similar enzyme pattern. As the fibroblast‐like osteoprogenitor cells of the callus developed into chondrocytes, enzyme activity increased. This was especially striking for isocitric dehydrogenase and glucose‐6‐phosphate dehydrogenase. When the chondrocytes became hypertrophic, they gradually lost enzyme activity. Mononuclear and multinuclear osteoclasts, macrophages and foreign body giant cells showed marked activity of most demonstrated enzymes. Glucose‐6‐phosphate dehydrogenase activity was marked in foreign body giant cells, but appeared weak in osteoclasts.At 14 days the enzyme pattern of the callus was essentially the same as at seven days.At 30 days bone union was well established, but there was still considerable osteoblastic and osteoclastic activity.The histochemical findings have been described in detail and discussed in correlation with pertinent morphological and biochemical data. Histochemically, bone regeneration proved to be essentially a recapitulation of normal bone growth.