The bone morphogenetic protein family: multifunctional cellular regulators in the embryo and adult.

Originally identified as the active components within osteoinductive extracts derived from bone, the BMPs now are known to include a large family of proteins within the TGF-beta superfamily of growth and differentiation factors. Members of the BMP family have been determined to be key signaling molecules in embryogenesis, in species ranging from Drosophila to humans. They are involved in delivering positional information, the development of hard tissues (both bones and teeth), as well as soft tissue types. When implanted into adult animals, several of the BMPs have been shown to initiate the complex cellular process resulting in the induction of bone through both the endochondral and intramembranous bone formation pathways. Preclinical studies have shown the ability of these factors to induce bone and heal large bony defects in a variety of models relevant to clinical problems in orthopedics, as well as the oral and maxillofacial/dental areas. For example, implantation of recombinant human BMP-2 (rhBMP-2) has been shown to augment the alveolar ridge in several animal models, and when placed in a periodontal environment to restore not only new bone, but also the attachment tissues. Results from ongoing clinical studies support the ability of rhBMP-2 implants to induce physiologic bone.