Platelet-derived growth factor (PDGF)-AA: A self-imposed cytokine in the proliferation of human fetal osteoblasts

PDGF, a multiple mitogen, stimulates osteoblast replication and bone collag en degradation, and it has been described as a key factor in bone metabolis m. Recently, PDGF was disclosed to be the autocrine cytokine of human osteo blasts, PDGF's effect on human bone development needs elucidation, and the mechanism of PDGF-AA autocrining remains unclear. In this work, osteoblasts were isolated from human fetal calvaria which resemble the cells in develo ping bone tissue. Using an in vitro model, the effect of PDGF-AA on the cel ls was investigated with the results showing that (i) after PDGF-AA was add ed into the medium for 24 h, PCI of the cells increased by 48.2% (P<0.05), and PCI decreased after the removal of PDGF-AA. (ii) 24 h after treatment w ith PDGF-AA, the percentage of osteoblasts in G(0)/G(1) phase decreased and that in S phase increased. (iii) The expression of PDGF-A mRNA was upregul ated by PDGF-AA, PDGF-BB, TGF beta,and bFGF respectively. These results pro ved that: (i) PDGF-AA enhances cell replication by accelerating cell recycl e and inducing the quiescent cells into the proliferation portion of cell c ycle. (ii) PDGF-AA is a self-imposed cytokine in human fetal osteoblast rep lication. (C) 2000 Academic Press.