Effects of platelet‐derived growth factor on bone formation in vitro

Abstract

Platelet‐derived growth factor (PDGF) is a polypeptide found in a variety of tissues, including bone, where it could act as an autologous regulator of skeletal remodeling. Therefore, a recombinant B chain homodimer of human PDGF was studied for its effects on bone formation in cultured rat calvariae. PDGF at 10‐100 ng/ml stimulated [3 H]thymidine incorporation into DNA by up to sixfold and increased the DNA content and the number of colcemid‐induced metaphase arrested cells. This effect was observed in the fibroblast and precursor cell‐rich periosteum. As a result of its mitogenic actions, PDGF enhanced [3 H]proline incorporation into collagen, an effect that was observed primarily in the osteoblast‐rich central bone. The effect of PDGF was not specific for collagen since it also increased noncollagen protein synthesis. In addition, PDGF increased bone collagen degradation. PDGF and insulin‐like growth factor (IGF) I had additive effects on calvarial DNA synthesis, but PDGF opposed the stimulatory effect of IGF I on collagen synthesis and IGF I prevented the PDGF effect on collagen degradation. In conclusion, PDGF stimulates calvarial DNA synthesis which causes an increased number of collagen‐synthesizing cells, but PDGF also enhances bone collagen degradation.