Unidirectional migration of osteosarcoma cells with osteoblast characteristics in response to products of bone resorption.

To investigate the mechanisms by which bone-forming cells are attracted to areas of bone resorption during bone remodeling, we have used in vitro methods to look for signals released by resorbing bone, which may be chemotactic for cultured bone cells. We have found that cultured rat osteosarcoma cells, which have characteristics associated with the osteoblastic phenotype, migrate in a unidirectional manner in response to a signal released by resorbing bones. These cells also migrated unidirectionally in response to Type I collagen, which comprises 95% of the bone matrix. This phenomenon of chemotaxis of bone-forming cells to sites of previous resorption may be an important component of the process of bone remodeling and the coupling of bone formation to bone resorption.