Chemotactic response of osteoblastlike cells to transforming growth factorβ

Abstract

Abstract Transforming growth factor β (TGF-β) has multiple effects on bone cell metabolism in vitro but its exact role in bone remodeling still needs to be defined. Here we demonstrate that TGF-β is chemotactic for osteoblastlike cells from fetal rat calvariae and osteoblastlike ROS 17/2.8 osteosarcoma cells. Maximal chemotaxis occurred at 5-15 pg/ml of TGF-β and was observed with TGF-β1 and TGF-β2 at equivalent concentrations. Conditioned medium from osteoblastlike cells containing latent TGF-β failed to stimulate chemotactic migration. However, chemotactic activity was observed in conditioned medium that had been transiently acidified. Since acidification is known to activate TGF-β, these results suggest that only active TGF-β is capable of inducing a chemotactic response. Preincubation of osteoblastlike cells with TGF-β in concentrations from 10 pg/ml to 1 ng/ml for 48 h abolished a subsequent chemotactic response of these cells to TGF-β, indicating that TGF-β-induced chemotaxis is a transient phenomenon. Since TGF-β may be released from the bone matrix and/or activated during bone resorption, the chemotactic activity of TGF-β for osteoblastlike cells may be important for the recruitment of osteoblastlike cells to sites of bone remodeling.