Bone morphogenetic protein-2 but not bone morphogenetic protein-4 and -6 stimulates chemotactic migration of human osteoblasts, human marrow osteoblasts, and U2-OS cells

Bone morphogenetic proteins (BMPs) have important functions for the differentiation of bone cells, but the exact role for bone remodeling and bone healing still needs to be defined. Migration of bone forming cells is an important physiological event both during bone healing and bone remodeling. The chemotactic properties of the bone morphogenetic protein family of growth factors have not been investigated. In this study the chemotactic effects of the bone morphogenetic proteins BMP-2, -4, and -6 have been quantitated toward human osteoblasts, human marrow stromal osteoblasts, and U2-OS human osteosarcoma cells. BMP-2 stimulated the migration of human stromal osteoblasts, human osteoblasts, and U2-OS cells with bell-shaped response curves in a dose-dependent manner with a 300% increase in cell migration at 1.0 ng/mL for human stromal osteoblasts and a 170-180% increase for human osteoblasts and U2-OS cells. At higher concentrations, migration decreased to background levels. BMP-4 and -6 did not show any effects on cellular migration. This study shows that BMP-2 can stimulate in vitro migration of human osteoblasts and human osteosarcoma cells. BMP-2 might play a role in the chemotactic recruitment of especially undifferentiated osteoblasts during bone remodeling and bone healing.