Rabbit Bone Marrow Response to Bovine Osteoinductive Proteins and Anorganic Bovine Bone

The effects caused by the implantation of bioabsorbable hydroxyapatite (HA) bound to a pool of bone morphogenetic proteins (BMPs) and other bone noncollagenous hydrophobic proteins mixed with anorganic bovine bone inside rabbit bone marrow were assessed. Within the interior of hollow cylindric titanium prototypes, the following biomaterials were inserted: (1) test group: HA containing a pool of BMPs and noncollagenous hydrophobic proteins mixed with anorganic bovine bone; (2) control group: HA without any protein mixed with anorganic bovine bone; and (3) negative control group: blood clot. The cylinders were placed surgically into the medial portion of the tibiae of 7 rabbits in a manner that allowed the biomaterials to contact just the bone marrow. Morphometric analysis showed that: (1) the biomaterials containing the protein mixture resulted in significantly less new bone than the biomaterials without such a mixture; (2) the group without the protein pool formed larger amounts of bone within the cylinder when compared to the negative control (blood clot only); and (3) the biomaterials containing the protein pool did not show any difference in relation to the negative control. It was concluded that a pool of BMPs and other bone noncollagenous hydrophobic proteins had an inhibitory effect on osteogenesis, and that the biomaterials without a protein pool formed a favorable substrate to bone formation.