Molecular biologic aspects of cartilage and bone: potential clinical applications

The formation of cartilage and bone tissue from condensing mesenchymal stem cells is taking place in the early stage embryo, but also in the growth plate and during fracture repair in adults. Resident mesenchymal stem cells have been identified in bone marrow, periosteum, and in muscles. These pluripotent cells are attractive as therapeutic cells in cartilage and bone reconstructive procedures, since they can differentiate into chondrocytes and osteoblasts upon appropriate stimuli, such as certain growth factors. Members of the transforming growth factor-beta (TGF-beta) superfamily, including TGF-beta1-3, bone morphogenetic proteins (BMPs), and activins, are essential mediators in cell proliferation and differentiation and play regulatory roles in cartilage and bone formation. This review presents functional data on TGF-beta1 in cartilage formation, BMP2 and BMP3 in bone formation, and a role of the BMP-regulatory protein noggin in BMP2 processing. Potential clinical applications of these proteins are further demonstrated and discussed.