Bone induction by osteogenin and bone morphogenetic proteins.

Bone induction is a multistep process that includes chemotaxis and attachment of mesenchymal stem cells, proliferation of progenitor cells and differentiation into cartilage and bone. Endochondral bone formation is the predominant sequence. Bone induction can be operationally divided into the following phases: initiation, promotion and maintenance. The initiation of bone induction is primarily regulated by osteogenin and bone morphogenetic proteins. Recent work has led to the isolation, purification and cloning of osteogenin and other bone morphogenetic proteins. Other growth factors such as platelet derived growth factor (PDGF), transforming growth factor beta (TGF-beta isoforms, insulin like growth factors (IGF 1 and 2), and fibroblast growth factor (FGF) may promote and perhaps maintain the newly induced bone.