Mechanisms of bone repair and regeneration.

Bone problems can have a highly deleterious impact on life and society, therefore understanding the mechanisms of bone repair is important. In vivo studies show that bone repair processes in adults resemble normal development of the skeleton during embryogenesis, which can thus be used as a model. In addition, recent studies of skeletal stem cell biology have underlined several crucial molecular and cellular processes in bone formation. Hedgehog, parathyroid hormone-related protein, Wnt, bone morphogenetic proteins and mitogen-activated protein kinases are the main molecular players, and osteoclasts and mesenchymal stem cells are the main cells involved in these processes. However, questions remain regarding the precise mechanisms of bone formation, how the different molecular processes interact, and the real identity of regenerative cells. Here, we review recent studies of bone regeneration and repair. A better understanding of the underlying mechanisms is expected to facilitate the development of new strategies for improving bone repair.