The Research Of RANKL And OPG MRNA Expressing Under The Mechanical Force In Rabbits

[Objective]In the previous study,we successfully established the animal model of premaxillary retraction with micro-implants placed in the maxillary as the anchorage in rabbits.In this research, we used the previous model and studied the mechanism of sutura remodeling on the molecular level by measuring the expression level of RANKL and OPG mRNA.To provide the theoretical basis of the clinical maxillary orthopedic,we deeply researched the sutura remodeling mechanism under the orthopedic force.[Methods] Using the previous animal model, we detected the expression level of RANKL and OPG mRNA in the premaxillary sutura and zygomaticomaxillary sutura by in situ hybridization(ISH),and measured the RANKL/OPG ratio simultaneously. Part l:we studied the RANKL and OPG mRNA expression level in the same action time with different force(50,100,150,200,250,300g/side). According to the experimental grouping,different force was exerted to the rabbits premaxillary sutura on both sides. All of the rabbits were killed on the seventh day.Then we detected the expression level of RANKL and OPG mRNA among the premaxillary sutura and zygomaticomaxillary sutura by ISH. Part2:the appropriate force(250g/side) was exerted to premaxillary sutura of the rabbits on both sides.According to the experimental grouping,the rabbits were killed after1,3,5,7,14and21days,and RANKL and OPG mRNA was measured by ISH.[Results] RANKL and OPG mRNA were positively expressed in the cell cytoplasm of osteoblastic cells,osteocytes and stroma cells by the ISH staining. Part1:In the premaxillary sutura,the gray value of RANKL mRNA descended gradually with the increase of the force. The expression of RANKL mRNA came down to the bottom, while the force was250g/side on both sides. Then the gray value increased slowly with the force increasing continuously. The gray value of OPG mRNA varied at the same trend,but OPG gray value was higher than RANKL in the same force. The RANKL/OPG gray value ratio descended slowly with the increase of the force.The ratio reached its lowest, while the force was250g/side on both sides. Then the ratio increased with the force increasing continuously,but during the whole process,the gray value ratio of RANKL/OPG was less than1.0000. This illustrated that the positive expression level of RANKL and OPG mRNA increased with the force increasing,and reached their peaks when the force was250g/side. In the zygomaticomaxillary sutura,the gray value of RANKL mRNA decreased slowly with the increase of the force,it reached its bottom when the force was250g/side on both sides. Then the gray value rose gradually with the force increasing continuously. OPG mRNA gray value changed at the same trend,but the gray value of OPG was lower than RANKL under the same force. The RANKL/OPG gray value ratio descended slowly with the increase of the force. Within250g/side on both sides,the ratio of RANKL/OPG gray value passed1.0000. With the force increasing continuously,the ratio decreased acutely below1.0000. It explained that the expression level of RANKL and OPG mRNA enhanced as the force increasing,and reached their peaks when the force was250g/side. Part2:Among the premaxillary sutura, the gray value of RANKL and OPG mRNA decreased with time extending.The gray value came down to the lowest after7days and increased as time increasing continually. Within7days,the gray value of RANKL mRNA was lower than OPG,but after7days,their levels were close to each other. The ratio of RANKL/OPG gray value descreased with time increasing. The ratio came down to the lowest on the seventh day,and the ratio was less than1.0000. It illustrated that the positive expression level of RANKL and OPG mRNA increased with time extending,and reached their peaks on the seventh day. Among the zygomaticomaxillary sutura,the gray value of RANKL mRNA decreased with time extending.And the gray value reached its lowest on the seventh day and increased acutely as time increasing continually. The gray value of OPG mRNA varied at the same trend,but the variation of OPG laged behind RANKL. The gray value of OPG mRNA came down to the bottom on the fourteenth day,But after14days,it acutely increased. The ratio of RANKL/OPG gray value increased with time increasing.And the ratio reached its peak on the fourteenth day,and the ratio was higher than1.0OOO.This illustrated that the positive expression level of RANKL and OPG mRNA increased with time extending,and expression level of RANKL mRNA reached the peak on the seventh day,but OPG reached the peak on the fourteenth day.[Conclusion]Both of the premaxillary sutura and the zygomaticomaxillary sutura remodeled most actively when the force was250g/side. Under the same mechanical force(250g/side), Osteoclastogenesis was most active on the seventh day,but Osteogenic effect was most active on the seventh day. The premaxillary sutura which was compressed was remodeled predominantly with bone resorption,while the zygomaticomaxillary which was been in distraction was remodeled predominantly with bone formation.