The effects of growth factors on the production of osteopontin and osteocalcin

Bone morphogenetic proteins (BMPs) are a group of structurally related proteins in the transforming growth factor-beta (TGF-beta) family which have been shown to stimulate bone formation in vivo. Since these proteins are concentrated in the organic matrix of bone and would be released after a fracture or during bone resorption, they are likely to have a profound effect on bone remodeling and may provide a link between bone resorption and bone formation. The hypothesis of this study was that osteoblast-like cells (OBs) treated with demineralized bone matrix (DBM) would have similar levels of secretion of osteopontin (OPN) and osteocalcin (OCN) to that of OBs treated with insulin-like growth factor-1 (IGF-1), while OBs treated with bone morphogenetic protein-7, also called osteogenic protein-1 (OP-1), would secrete levels of OPN and OCN less than the DBM group. Specifically, the aims of this study were to evaluate osteoblast-like cells (MG-63 cell line) for secretion of both OPN and OCN after treatment with DBM, OP-1, or IGF-1 compared to control, at 24, 48, and 72 hours. After each incubation period, ELISA kits were used to determine the levels of osteopontin and osteocalcin production. The results clearly demonstrated a rise of OCN at 48 hours and a fall at 72 hours for all samples, including control groups. However, there was no significant difference between groups (p > 0.05). With the OPN assay, results showed no significant difference between groups until 72 hours (p = 0.022), where the IGF-1 group was significantly higher than the Control and DBM groups (p = 0.003 and p = 0.021, respectively). This information is important for understanding the signaling pathways that may be initiated in the osteoblast following stimulation with growth factors.