Study On The Effect Of RhPDGF-BB Combined With RhTGF-β₁ On Periodontal Tissue Remodeling And RAS Protein Of Orthodontic Tooth In Rats

Objective:Establish a rat orthodontic tooth movement model and combine injection of recombinant human platelet-derived growth factor-BB（rhPDGF-BB）and recombinant human transforming growth factor-β₁（rhTGF-β₁）,to observe the remodeling of periodontal tissue and Ras protein expression changes,further explore combination of rhTGF-beta₁ and rhPDGF-BB modification mechanism of periodontal tissue,in order to provide more experimental basis for basic orthodontic experiments.Methods:Eighty male SD rats were selected and randomly divided into experimental group A and control group B.Each group was divided into five groups according to the different time points.Orthodontic nickel-titanium spiral tension spring was placed between the left maxillary first molar and bilateral incisors,the force was 50g.Group A was injected with 0.1ml rhPDGF-BB（10ng）and rhTGF-β₁（5ng）mixture at the buccal gingival mucosa of the left maxillary first molar from the first day of loading,and group B was injected with PBS of the same volume.Both groups were injected once every other day.A small group of rats in each group were killed on the 1st,4th,7th,10th and 14th day after loading.The accurate impression of maxillary complete dentition was taken and the model of super anhydrite was perfused before modeling and execution.The tooth movement distance of rats before and after modeling was measured and recorded by stereomicroscope.HE staining was used to observe the changes of periodontal tissue morphology.Trap staining was used to observe the changes of osteoclast activity and quantity in pressure side.The expression of Ras protein was detected by immunohistochemical（IHC）staining,real-time quantitative PCR（RT-PCR）was used to detect the expression changes of ALP and Runx2 mRNA gene levels.Results:（1）Moving distance:The moving distance of group A is more than that of group B,it increases with time.The comparison between group A and group B on the first day is not statistically significant（P>0.05）,the rest are statistically significant（P<0.05）.（2）HE staining:There was no significant difference in the changes of periodontal tissue between group A and group B on the first day.On the 4th day,the surface of the alveolar bone on the pressure side of the group A began to appear silkworm-like resorption lacunas,and a small amount of osteoclasts were seen,and there were fewer osteoclasts in the group B;on the 7th day,the multinucleated osteoclasts were obviously increased in the group A and formed Large-area silkworm-like resorption lacuna;on the 10th and 14th day,the two groups of osteoclasts began to decrease;the fibroblast proliferation of A group was more active than the B group in the tension side,the alveolar bone edge was scattered with osteoblasts,and new bone was visible.（3）TRAP staining:The two groups increased with the application time,the osteoclasts gradually increased,reaching the peak value on the 7th day.The comparison between the two groups was statistically significant except that there was no statistical difference on the 1st day.（P<0.05）.（4）PCR expression results:The expression level gradually increased from the first day,and the two groups reached a peak on the seventh day,and then gradually decreased;The A group always has more ALP and Runx2 mRNA gene expression than B group.Except that there was no statistical difference between the two groups on the 1st day and the 14th day（P>0.05）,the rest were statistically different（P<0.05）.（5）Ras protein expression results:With the increase of the stress time,the integral optical density of Ras protein in the periodontal tissue of the growth factor injection group was always higher than that of the control group,showing a trend of first increasing and then decreasing,and both groups reached a peak on the 7th day,And the difference between the two groups on the 4th day and the 7th day was statistically significant（P<0.01）.Except that there was no statistical difference between the two groups on the first day（P>0.05）,the rest were statistically different（P<0.05）.Conclusion:1.The combined application of rhPDGF-BB and rhTGF-β₁ increases the number of osteoclasts in the periodontal tissue and the expression of osteogenic genes ALP and Runx2 mRNA,thereby promoting the remodeling speed of the periodontal tissue of the orthodontic tooth in rats and accelerating the movement of the orthodontic tooth.2.Ras as a signal molecule,participates in the remodeling of periodontal tissues,the combined application of rhPDGF-BB and rhTGF-βenhances the expression of Ras protein in periodontal tissues.