Elevated IGF-II and TGF-beta concentrations in human calvarial bone: potential mechanism for increased graft survival and resistance to osteoporosis.

Calvarial bone grafts may have greater survival as donor tissue than bone from other sites. Furthermore, calvarial bone is resistant to osteoporosis. Because bone contains growth factors that may play an important role in the regulation of bone repair, we proposed that bone from calvaria may be enriched in one or more growth factors. To test this hypothesis, samples of bone from 10 men 64 years of age or older that were obtained at autopsy from three skeletal sites (calvaria, iliac crest, and vertebral body) were cleaned, extracted by demineralization, and assayed for growth factors insulin-like growth factor I, insulin-like growth factor II, and transforming growth factor-beta. Insulin-like growth factor II and transforming growth factor-beta concentrations were significantly higher in calvaria than in iliac crest or vertebral body. We conclude that the increased concentrations of growth factors in calvarial bone may lead to a greater capacity for bone repair and graft retention.