Growth factors regulate expression of osteoblast-associated genes

Background: The goal of periodontal regenerative therapies is to reconstruc t periodontal tissues such as bone, cementum, and periodontal ligament cell s (PDL). The need to establish predictable treatment modalities is importan t for reconstruction of these tissues. The aim of this study was to determi ne the effects of a low molecular extract of bovine bone protein (BP) conta ining bone morphogenetic proteins (BMPs) 2, 3, 4, 6, 7, 12, and 13, alone o r in combination with platelet-derived growth factor (PDGF) and/or insulin- like growth factor (IGF) on osteoblast differentiation in vitro. Methods: BP, mixed with a collagen matrix, was added to a poly (DL-lactide- co-glycolide) polymer (PLG) and placed at orthotopic sites in the skullcaps of Sprague-Dawleys rats. At day 28, rats were sacrificed for histological analysis. All sites treated with the polymer/BP produced bone while control sites (without BP) showed no bone formation. Having established the biolog ical activity of BP, in vitro studies were initiated using MC3T3-E1 cells, a mouse osteoprogenitor cell line. The ability of BP and other growth facto rs to alter cell proliferation was determined by Coulter counter, and diffe rentiation was determined by Northern analysis for specific genes. Results: When compared with cells treated with 2% serum alone, PDGF enhance d cell numbers at 10 and 20 ng/ml; IGF produced no significant effect at th ese doses; and BP at 10 and 20 mu g/ml decreased cell proliferation. Northe rn analysis revealed that PDGF blocked gene expression of osteopontin (OPN) and osteocalcin (OCN), while BP and IGF promoted gene expression of bone s ialoprotein (BSP) and OPN. The combination of BP and IGF enhanced expressio n of OPN beyond that of either BP or IGF alone. PDGF was able to block the effects of IGF on gene expression, but not those of BP. Conclusions: These results indicate that BP, PDGF, and IGF influence cell a ctivity differently, and thus raise the possibility that combining factors may enhance the biological activity of cells.