Growth control of cultured rat calvarium cells by platelet-derived growth factor

Platelet-derived growth factor (PDGF), which is released during the "clotting cascade", has a mitogenic effect on a variety of mesenchymal cells including those of the periosteum. Cell culture provides a method of studying these effects. In the present study, PDGF was studied for its ability to stimulate quiescent calvarium periosteal cells to enter G1, indicated by new protein synthesis. After addition of platelet poor plasma, these cells later entered S phase, indicated by uptake of 3H-thymidine. Three hours after PDGF stimulation, there were quantitative increases of at least 18 protein bands as compared to cells left in serum starvation medium. Two of these new protein bands (31K and 45K) required transcription. These data suggest that PDGF in extravasated blood may stimulate appositional bone formation beneath intact periosteum at the site of injury.