OSTEOINDUCTION IN POROUS HYDROXYAPATITE IMPLANTED IN HETEROTOPIC SITES OF DIFFERENT ANIMAL-MODELS

Previous studies have demonstrated the induction of bone in coral-deri ved porous hydroxyapatite when implanted intramuscularly in baboons. T his hydroxyapatite-induced bone differentiation model was used to stud y the effect of different animal species on heterotopic bone formation . Porous hydroxyapatite, obtained after hydrothermal conversion of the calcium carbonate exoskeleton of coral (genus Goniopora), was implant ed in the rectus abdominis of adult rabbits, dogs and baboons (Papio u rsinus). Specimens were harvested on day 90 after implantation and sub jected to histological and histomorphometrical analysis. Minimal amoun ts of bone formed in hydroxyapatite specimens harvested from rabbits a nd dogs. Substantial bone differentiation did occur, however, in hydro xyapatite specimens harvested from the rectus abdominis of the baboons . In primates, the porous hydroxyapatite, as used in this study, may a ct as a solid matrix for adsorption, storage and controlled release of circulating or locally produced bone morphogenetic proteins, which lo cally initiate bone formation. The results of this study on heterotopi c bone formation in porous hydroxyapatite underscore the importance of primate models in biomaterial research, which should be exploited for the formulation of porous substrata with intrinsic osteoinductive act ivity.