| Bone metabolism consists of bone formation and bone resorption. It is regulated by various factors. At the molecular level, the multifunctional roles of genes, signaling pathways, hormones, and paracrine factors are involved in the regulation of bone metabolism. Among which, the signal pathways play an important role in this process. Currently, in the studies of the bone metabolic signal pathways, BMP/Smads, Wnt/β-catenin, and OPG/RANKL/RANK signal pathways have been deeply studied, and it is generally accepted as key signal pathways in the bone metabolism. BMP/Smads and Wnt/β-catenin pathways mainly affect bone formation, while OPG/RANKL/RANK pathway controls the process of bone resorption. The latest studies show that hypoxia/hypoxia-inducible factor-la pathway, PDGF, TGF-β and FGF pathway, AKt2 pathway, G protein signaling pathway, heparin sulfate and chondroitin sulfate pathway, and focal adhesion kinase and extra-cellular signal-related kinase pathway also play regulating roles in the differentiation and proliferation of osteoblasts and osteoclasts. The interaction between BMP/Smads pathway and Wnt/β-catenin pathway has also been found. Intensive study on bone metabolism pathway can help to find potential cell-based therapeutic ways for metabolic bone diseases especially for osteoporosis. |