Bone induction by fetal and adult human bone matrix in athymic rats

In the rat the intramuscular implantation of demineralized rat bone matrix induces local bone formation. In adult primates, however, allogenous bone matrix induces little or no bone formation in extraskeletal sites. To assay inductive properties, human demineralized bone matrix from 6 adult donors and 4 fetuses was implanted intramuscularly in athymic rats for 6 weeks. Fetal and adult matrix implants yielded about the same amount of bone: about half of the bone yield from rat or rabbit matrix in the same model. We conclude that human bone matrix has inductive properties and that failures to induce bone formation in adult primates may be due to an inability by the recipients to respond to inductive stimuli of adult bone matrix.