NON-COORDINATE CONTROL OF BONE-FORMATION DISPLAYED BY GROWTH-FACTOR COMBINATIONS WITH IGF-I

Polypeptide growth factors (GFs) promote osteogenesis by enhancing the mitogenesis, migration, and matrix synthesis of osteoblasts. Most pre vious investigators have evaluated only the effects of single GFs on t hese parameters. Studies on single GFs might overlook large biological responses comparable with those documented in the cell cycle literatu re when GFs are used in combinations that interact synergistically. Ln this study, we screened for synergistic interactions between IGF-I an d three additional GFs (PDGF-BB, TGF-beta 1, and bFGF) on the regulati on of bone growth and differentiation. Fetal bovine osteoblasts were a ssessed for osteoblast mitogenesis, collagenous and non-collagenous pr otein synthesis, and alkaline phosphatase activity (ALP). Our results show synergistic interactions between IGF-I and the other GFs on osteo blast mitogenic activity and protein synthesis. In contrast to synergi stic mitogenic and protein synthesis effects, IGF-I failed to increase ALP activity when combined with TGF-beta 1, PDGF-BB, and bFGF in bovi ne osteoblast-like cells.