The Expression Of BMP-2,OPG And RANKL In The Mid-Palatal Suture Of Beagles By Magnetic Expansion And Mechanical Screw Expansion

Objective:The purpose of this research was to evaluate the effect of magnetic palatal expansion and mechanical screw expansion in the process of mid-palatal suture remodeling of Beagles,by recording the expression of bone morphogenetic protein 2(BMP-2),osteoprotegerin(OPG) and osteoclast differentiation factor(RANKL).Methods:1. Establish an Animal model of maxillary expansion.36 beagle dogs were randomly divided into three groups,with 12 dogs in the magnetic expansion(ME) group placed on the new-designed magnetic expanders, 12 dogs in the mechanical screw expansion(SE) group placed on the Hyrax appliance,and 12 dogs in the control group placed on nothing. Each of three groups were divided into two subgroups of A and B with 6 dogs in each subgroup.The magnetic expanders in ME group were loaded once per week(1.5mm per time),while the Hyrax appliances in SE group were turned twice per week(0.75 mm per time).After 5 weeks of extension(T1 phase),subgroups A in the three groups were killed and then the maxillary palatal bone specimens were obtained.Subgroups B in the two experimental groups continued to use expanders with no loading.After 8 weeks of retention(T2phase),subgroups B in three groups were killed and then the maxillary palatal bone specimens were obtained by the same method.2. Investigate the expression of mRNA and protein of BMP-2,OPG,RANKL.The maxillary palatal bone blocks were grinded into bone meal.The mRNA expression level of BMP-2 ? OPG and RANKL was detected by RT-PCR and the protein expression level of BMP-2,OPG and RANKL was detected by Western Blot.Results:1. The results of RT-PCR was coincident with Western Blot.2. Comparision among three groups(ME group,SE group and control group).In the T1 phase,compared with the control group, the expression of BMP-2,OPG mRNA and protein in the two experimental groups were significantly increased,and the expression of RANKL was significantly decreased.Compared with the SE group,the expression of BMP-2,OPG were significantly increased,and the expression of RANKL was significantly decreased in the ME group.In the T2 phase,compared with the control group,the expression of BMP-2,OPG mRNA and protein in the ME group were significantly increased and the expression of RANKL was significantly decreased.While,there was no statistical difference of the three factors between SE group and control group.There was no difference also between the two experimental groups.3. Intra- group comparison between T1 and T2.Compared with the T1 phase, all of the three factors in the control group increased without statistical difference in T2 phase.Contrasted with the T1 phase,The expression of BMP-2,OPG in the two experimental groups were decreased and the expression of RANKL was increased with statistical significant difference.Conclusion:1. Both magnetic expansion and mechanical screw expansion could significantly promote the expression of BMP-2,OPG and restrain the expression of RANKL in mid-palatal suture during expansion;And the effectiveness was more remarkable for magnetic expansion.2. The expression of BMP-2,OPG was restrained and the expression of RANKL was promoted significantly in mid-palatal suture during the retention of magnetic expansion and mechanical screw expansion.3. Magnetic expansion could still promote the expression of BMP-2,OPG and restrain the expression of RANKL in the mid-palatal suture during retention.