Age effects on bone induction by demineralized bone powder.

It has been previously shown that osteoinduction by demineralized bone powder (DBP) in the rat decreases as the age of the recipient animal increases. In the present study, the effects of age on osteoinduction by DBP were evaluated in the rat by varying the age of the donor and the recipient animal. Cartilage and bone formation in subcutaneous pouches was assessed using a histologic grading technique in which a composite score was derived from analysis of multiple histologic sections from each specimen. The results confirm the previously reported decrease in osteoinduction in middle-aged adult animals compared with younger ones. However, DBP prepared from middle-aged adult rats was more inductive than that prepared from either prepubertal or young postpubertal animals. The latter result contradicts the widely held belief that demineralized bone matrix from younger animals is more inductive than that from older ones. This finding may help to further elucidate the mechanism of ectopic bone formation and lead to more inductive bone graft substitutes for human use.