Bovine bone morphogenetic protein (bBMP/NCP)-induced repair of skull trephine defects in pigs

Bovine bone morphogenetic protein and associated noncollagenous proteins (bBMP/NCP) were implanted in skull trephine defects, 14 and 22 mm in diameter, in adult minipigs. The defects were larger than the critical size for repair of cranial bones in pigs observed for a period of six to 16 weeks. The trephines were placed either in the nasal bone at eye level, or in the frontal bone. In minipigs the repair was more advanced in trephines in the frontal bone than in the nasal region, but was incomplete in either bone bed. As in dogs, implants of bBMP/NCP in heterotopic sites were resorbed before a competent cell population could respond. Serum anti-BMP antibody was elevated. The IgG levels of the antibody titer showed a clearcut dose-response; the level was significantly higher in one pig with implants of 85 mg of bBMP/NCP proteins in a frontal bone trephine.