PULSATING ELECTROMAGNETIC-FIELD STIMULATES MESSENGER-RNA EXPRESSION OF BONE MORPHOGENETIC PROTEIN-2 AND PROTEIN-4

The effects of a pulsating electromagnetic field on mRNA expression of bone morphogenetic protein-2 and -4 in chick embryonic calvaria were examined. From the onset of embryogenesis (Day 0), chick embryos were incubated in a continuously generated pulsating electromagnetic field with a peak of 3.5 milli-Tesla (mean: 2 milli-Tesla) and vibration at 15 Hz. Control chicks were incubated in a normal magnetic field. Northern-blot analysis showed that the mRNAs of bone morphogenetic protein-2 and -4 were expressed in the calvaria. Quantitative analysis of the mRNA expressions was done by means of slot-blot hybridization. The magnetic field enhanced the expressions of both mRNAs. The enhancements were more pronounced in younger chick embryos (Day 15 > Day 17), and no significant change was observed in the 19-day-old embryos. These results indicate that osteo-inductive effects of the magnetic field were mediated at least in part by bone morphogenetic protein-2 and -4.