Sensitivity of osteoinductive activity of demineralized and defatted rat femur to temperature and duration of heating.

For autogenous and allogeneic bone grafts, heat treatment has been thought to kill malignant cells and viruses such as human immunodeficiency virus. It is unclear whether heat treatment could preserve bone-inductive activity. Cortical bones from 6-week-old rat femurs were heated in a water bath at a temperature of 50 degrees-100 degrees C for periods of 15 minutes to 10 hours. After treatment, they were defatted and decalcified. Each sample was transplanted into the hamstring muscle of 3-week-old rats. Eleven days after transplantation, the samples were removed and messenger ribonucleic acids (mRNAs) were determined for alkaline phosphatase and collagens in the transplant. Twenty-one days after transplantation, actual bone formation was studied by histologic analysis and measurement of calcium content. Heat treatment at 60 degrees C for 10 hours and at 70 degrees C for 1 hour preserved bone-inductive activity, as indicated by the induction of mRNAs for alkaline phosphatase and Type I and Type II collagens. Significant decreased in Type II collagen mRNA and calcium content were observed at 70 degrees C when the transplants were heated for 10 hours, suggesting the importance of evaluating the duration of heat treatment.