Effect of partially purified bone morphogenetic protein on DNA synthesis and cell replication in calvarial and fibroblast cultures.

The effects of bone morphogenetic protein (BMP), a molecule extracted from demineralized bone, were observed in organ cultures of 21-day fetal rat calvariae. The effects of BMP on cell replication in cultures of normal rat kidney (NRK) fibroblasts were studied for comparison. At concentrations of 0.1-10 micrograms/ml for periods of 24-96 hours, BMP stimulated the incorporation of 3H-thymidine into acid-insoluble residues (DNA) in calvariae by 25%-159%, and at 1-10 micrograms/ml it increased bone DNA content by 20%-23%. BMP at 1 micrograms/ml also increased the number of calvarial mitoses after colcemid arrest by 1.5-1.8-fold. The effect of BMP on calvarial DNA synthesis was observed in the periosteal bone. In contrast to its effects on DNA synthesis, BMP did not stimulate the incorporation of 3H-proline into collagenase-digestible and noncollagen protein and did not alter calvarial alkaline phosphatase activity. BMP at 1-10 micrograms/ml caused a marked increase in 3H-thymidine incorporation into DNA in cultured NRK fibroblasts and increased DNA content and cell number by 1.5-2-fold. These studies indicate that BMP stimulates DNA synthesis and cell replication in calvarial and fibroblast cultures but does not stimulate postdifferentiated bone cells in incubated calvariae.