Repair of massive bone defect by bone morphogenetic protein

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1. Bone morphogenetic proteins were purified from Dunn osteosarcomas (800g) and human osteosarcomas in nude mice (800g) by guanidine extraction, acetone fractionation, ion-exchange chromatography, gel filtration and HPLC.2. We tested immunogenicity biocompatibility and biodegrability of various collagens, hydroxyapatites, and biopolymers, in order to select suitable carriers for BMP in vivo.3. We implanted the composites of BMP and each carrier substance into the back muscles of mice and examined new bone formation radiologically and histologically at 3 weeks.4. Pepsin-digested bovine skin collagen, hydroxyapatite, polylactic acid, and polylactic acid-polyethelene glycol, block copolymer proved to be suitable carriers for BMP.5. We implanted the composites of BMP and each carrier substance (collagen, polylactic acid, polylactic acid-polyethelene glycol) beneath the periosteum of rabbit tibia. New bone formation was observed by a composite of BMP/polylactic acid-polyethelene glycol at 4 weeks.6. We made a bony defect (2cm) in the rabbit tibia and implanted a composite of BMP/polylactic acid-polyethelene glycol in combination with hydroxyapatite rod into the gap of tibia. New bone formation was observed at the surface of the hydroxyapatite rod at 6 weeks and a bony bridge was obtained at 12 weeks.7. We implanted the composites of BMP and each carrier substance (collagen, polylactic acid, polylactic acid-polyethelene glycol) with and without hydroxyapatite into the back muscles of monkeys. Only BMP/collagen/hydroxyapatite induced new bone formation at 4 weeks.8. We implanted the composite of BMP/collagen/hydroxyapatite beneath the periosteum of monkey tibia. New bone formation was was observed at 4 weeks.