Effect Of Constant Static Magnetic Field On Cobalt, Chromium Ions Induced Cytotoxicity And The Releasion Of RANKL, OPG By Osteoblasts

Objective:Through evaluation the constant magnetic field on the cellular viability of cobalt and chromium ions on mice osteoblast (MC3T3E1) and the effects on the secretion of RANKL/OPG from osteoblast because of the stimulation of Co2+and Cr3+ions. to investigate the influence of metal ions on osteoblast under the constant magnetic field and aseptic loosening and explore the methods to prevent the periprosthetic osteolysis.Methods:Osteoblasts were cultured in the density of 1×10 cells/ml in vitro and Metal ions Co2+,Cr3+, respectively, and mice osteoblast in different magnetic field strength (1mT,10mT,100mT) under the co-culture. Experimental sub-4 Group, group A:Co2+,Cr3+group(control group), group(B,C,D):Co2+,Cr3+,respectively, add to different magnetic field strength (1mT,10mT,100mT), cells viability and the expression levels of RANKL and OPG were assessed by MTT, ELISA assays and RT-PCR at different time point.Results:After Co2+, Cr3+24h interaction with osteoblasts, ELISA test showed that the releasion of RANKL in group B and C and D were inferior 9.5%and 22.5%and 22.6%to the control group A and had a statistical significance(p<0.05). After 48h interaction, the releasion of RANKL in group B and C and D were inferior 7.6%and 11.2%and 19.6%to the control group A and had a statistical significance(p<0.05). After Co2+, Cr3+24h interaction with osteoblasts, ELISA test showed that the releasion of OPG in group B and C and D were superior 7.2%and 8.7%and 22.4%to the control group A and had a statistical significance(p<0.05). After 48h interaction, the releasion of OPG in group B and C and D were superrior 0.74%and 11.9%and 23.9%to the control group A and had a statistical significance(p<0.05). RT-PCR test found the gene expression of both RANKL and OPG in each group. After Co2+, Cr3+ 24h interaction with osteoblasts, the gene expression of RANKL mRNA in group B and C and D were inferior 5.9%and 16.9%and 21.1%to the control group A and had a statistical significance(p<0.05). After 48h interaction, the releasion of RANKL mRNA in group B and C and D were inferior 9.3%and 21.9%and 26.1%to the control group A and had a statistical significance(p<0.05). After Co2+, Cr3+24h interaction with osteoblasts, the gene expression of OPG mRNA in group B and C and D were superior 2.7%and 4.9%and 3.1%to the control group A and had a statistical significance(p<0.05). After 48h interaction, the gene expression of OPG mRNA in group B and C and D were superior 0.83%and 3.9%and 5.7%to the control group A and had a statistical significance(p<0.05). Gene expression of RANKL decreased in Group B and C and D,especially in Group C and D. but the expression of OPG mRNA increased slightly. The ratio of RANKL/OPG in group B and C and D are significantly lower than group A either in the protein level or the gene level, especially group B and C.Conclusion:Certain intensity of constant magnetic field can antagonize metal ions cobalt, chromium ions induced cellular activity and stimulate the releasion of OPG, decrease the secretion of RANKL from osteoblast, downregulate the ratios of RANKL/OPG proteins, so that may decrease the incidence of the periprosthetic osteolysis.