OSTEOGENIC PROTEIN-1 STIMULATES MESSENGER-RNA LEVELS OF BMP-6 AND DECREASES MESSENGER-RNA LEVELS OF BMP-2 AND BMP-4 IN HUMAN OSTEOSARCOMA CELLS

Bone morphogenetic proteins (BMPs) are novel growth and differentiatio n factors that act on mesenchymal stem cells to initiate new bone form ation in vivo and promote the growth and differentiation of cells in t he osteoblastic lineage. In the present study, we examined the effects of recombinant human osteogenic protein-1 (also known as BMP-7) on th e expression of related members of the BMP family using SaOS-2 and U2- OS, two human osteosarcoma cell strains. Evaluation of BMP-2, -4, and -6 mRNA expression indicates that OP-1 stimulated the mRNA levels of B MP-B in both SaOS-2 cells (threefold) and U2-OS cells (fivefold) after 24 hours of treatment, while decreasing the mRNA levels of BMP-4 in S aOS-2 cells (80%) and BMP-2 and BMP-4 in U2-OS cells by 50% and 72%, r espectively. BMP-2 mRNA expression, as examined by Northern blot analy sis, was below detectable limits in SaOS-2 cultures. These results dem onstrate that OP-1 modulates the mRNA expression of related members of the BMP family, suggesting a possible mode of action of OP-1 on the g rowth and differentiation of cells in the osteoblastic lineage in vitr o.