Bone is a dynamic tissue, continuously remodeled by the coordinated actions of osteoclasts and osteoblasts. Osteoblasts, the cells that form bone, are originally derived from pluripotent mesenchymal stem cells. They synthesize and secrete an organic extracellular matrix, osteoid, which is composed primarily of type I collagen. The osteoid is calcified by the osteoblasts and, during this process, the cells lodge in the gaps of the calcified material and become osteocytes. Osteoblasts express protease-activated receptor-1 and vascular endothelial cell growth factor. Studies show that leukemia inhibitory factor can bind to the surface of osteoblast cells and induce bone formation in vitro and in vivo. The balance between recruitment, proliferation, differentiation and apoptosis of osteoblasts in the sutures between cranial bones is essential for calvarial bone formation.