OSTEOGENIC ACTIVITY OF BONE MORPHOGENETIC PROTEIN AND HYDROXYAPATITE COMPOSITE IMPLANTS

In an experimental study in rats hydroxyapatite (HA) ceramics of chara cteristics and inactive rat bone matrix were investigated comparativel y for their suitability as carriers for osteoinductive factors. Bone m orphogenetic protein was extracted from long bones of pigs under disso ciative conditions and partially purified by gel filtration. The resul ting pBMP was combined with the granular hydroxyapatite ceramics Ospro vit(R), Algipore(R), Frialit(R) and inactive rat bone matrix (IBM) by precipitation of aliquots of this pBMP fraction onto pellets of each c arrier material. The osteogenic activity of these composite implants a nd of corresponding controls was bioassayed by implantation into muscl e pouches of immunodeficient rats. All pBMP-HA ceramic implants elicit ed ectopic bone formation within 25 days after implantation, whereas c ontrol implants did not show any osteoinductive ability. Alkaline phos phatase (AP) activity of the explant tissues was determined for quanti tation of bone formation. Due to the high incidence of bone formation found in each pBMP group all HA ceramics tested seem to be basicly sui table as carriers for osteoinductive factors. Algipore, a highly porou s phycogen HA ceramic, was found to be quantitatively superior to all other materials investigated due to its very large surface available f or protein binding