Bone is a dynamic tissue, being continuously remodeled by the coordinated actions of osteoclasts and osteoblasts. Osteoblasts, the bone-forming cells, are derived originally from pluripotent mesenchymal stem cells. They synthesize and secrete organic extracellular matrix, osteoid, which is composed primarily of type I collagen. Osteoid is calcified by osteoblasts and during this process the cells become encased in lacunae within 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 osteoblast cell surface and induce bone formation both in vitro and in vivo. The balance between osteoblast recruitment, proliferation, differentiation and apoptosis in sutures between cranial bones is essential for calvarial bone formation. HCO from ScienCell Research Laboratories are isolated from human calvariae. HCO are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 105 cells in 1 ml volume. HCO are characterized by the cytochemical detection of Alkaline Phosphatase staining and/or mineral deposition. HCO are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HCO are guaranteed for 10 population doublings under the conditions provided by ScienCell Research Laboratories. Recommended Medium It is recommended to use Osteoblast Medium (ObM, Cat. #4601) for the culturing of HCO in vitro.