Bone morphogenetic protein-2: biology and applications.

Bone morphogenetic protein-2 is a low molecular weight glycoprotein, classified as a morphogen. The sine qua non of bone morphogenetic protein is consistently reproducible induction of bone development in heterotopic sites. Bone morphogenetic proteins belong to the expanding transforming growth factor-beta superfamily. Bone morphogenetic protein-2 has pleiotropic functions that range from extraskeletal and skeletal organogenesis to bone generation and regeneration. Bone morphogenetic protein induced bone formation in postfetal life recapitulates the process of embryonic and endochondral ossification. Through recombinant gene technology, human bone morphogenetic protein-2 is available in almost unlimited amounts for basic research and clinical trials. Human bone morphogenetic protein-2 induces structurally sound orthotopic bone in a variety of experimental systems, including femoral defects in rats, tibial and ulnar defects in rabbits, femoral defects in sheep, mandibular defects in dogs, spinal fusion in dogs, and porous ingrowth in rats. Human bone morphogenetic protein-2 research extends to the fields of developmental biology, genetics, and evolution. Bone morphogenetic protein has been used successfully at the authors' institution to heal clinical nonunions and to achieve spinal fusion. This report reviews the current understanding of bone morphogenetic proteins in general and BMP-2 in particular and summarizes their potential applications.