Osteoinduction of human demineralized bone: Characterization in a rat model

The increasing clinical use of human demineralized bone matrix has brought about the desire to understand better the osteoinductivity of these graft m aterials, The rat heterotopic model has been used successfully to show the sequence of events involved in the endochondral ossification process result ing in osteoinduction. In this study, the osteoinductive potential of human demineralized bone powder was assessed, using immune compromised rats (ath ymic rnu/rnu) to avoid problems associated with cross species incompatibili ties. Implants were placed in subcutaneous or intermuscular sites. This mod el is characterized to provide a basis for routinely determining the perfor mance of human demineralized bone powder, Demineralized bone powder was pre pared from rat and human cortical bone according to a strict protocol. The lack of response to guanidine HCL extracted (noninductive) demineralized bo ne showed the selectivity of the assay. The same lots of human and rat demi neralized bone were tested in sequential experiments during a 1-year period . These results showed reproducible induction of the demineralized bone pow der between experiments. Combining demineralized bone with the guanidine HC l extracted demineralized bone in varying ratios tested the sensitivity of the assay. These results showed an increase in bone formation with increasi ng quantities of active demineralized bone and established the ability of t he bioassay to differentiate between the various levels of active (osteoind uctive) demineralized bone powder. With this model, consistent performance of demineralized bone powder processed by well controlled methods was seen.