Effect Of PDGF-BB Combined With TGF-β₁ On Periodontal Tissue Remodeling And ERK Protein In Orthodontic Rats

Objective:Through the observation of the effects of combined injection of recombinant human Platelet derived growth factor-BB（rh PDGF-BB）and recombinant human transforming growth factor-β₁（rh TGF-β₁）on the periodontal tissue reconstruction of rat orthodontic tooth and the change of Osteopontin（Opn）and Extracellular regulated protein kinases（ERK）expression,to further explore the specific reconstruction mechanism of the combined use of rh PDGF-BB and rh TGF-β₁on periodontal tissues and to provide more basis for basic research on orthodontic tooth movement.Methods:80 male SD rats which weighing about 200g were randomly divided into experimental group A and control group B.Each group was divided into 5 groups（8 rats each group）according to the different time checkpoints.An orthodontic nickel-titanium spiral tension spring force device（a force value of about 50g）was placed between the left maxillary first molar and the bilateral incisors of each rat to establish a rat orthodontic mesial movement model.Beginning from the first day of modeling,group A was injected with mixture which combined 0.1ml of PDGF-BB（10ng）+TGF-β₁（5ng）every other day,and group B was injected with the same amount of PBS every other day.On the 1st,4th,7th,10th,and 14th days after the application of force,one rat were killed in groups A and B.Measure the distance of the mesial movement of the first molar,HE staining to observe the reconstruction of periodontal tissue,TRAP staining for osteoclast count,RT-PCR to detect changes in Opn mRNA expression,and immunohistochemical staining to detect the changes of the expression of ERK protein level in periodontal tissues.Results:1.The distance of orthodontic tooth movement of rats:On the first day of modeling,there was no obvious movement of orthodontic tooth in the experimental group and the control group,and there was no significant difference between these two groups（P>0.05）;On the 4th,7th,10th and 14th day,with the increase of the force application time,the orthodontic tooth movement distance of the two groups gradually increased.The experimental group was significantly higher than the control group,and it was statistically significant（P<0.05）.2.HE staining results of periodontal tissue reconstruction:With the increase of time of force application,the number of bone resorption lacunas and osteoclasts on the surface of the pressure side alveolar bone in the experimental group was higher than the control group,and the alveolar bone resorption was more obvious,the area of hyaline degeneration is reduced relatively;compared with the control group,the cells in the periodontal ligament in the tension side of the experimental group have more cell components and are arranged regularly.There are chain-shaped osteoblasts on the edge of the alveolar bone,and new bone tissue is formed.3.Osteoclast count:With the increase of the time of force application,the number of osteoclasts on the surface of the alveolar bone on the pressure side of the left first molar of the experimental group and the control group gradually increased,and both reached the peak on the 7th day and decreased gradually.Except that the number of osteoclasts on the pressure side of the experimental group and the control group on the first day of modeling wasn’t statistically significant（P>0.05）,the number of osteoclasts in the experimental group on the 4th,7th,10th,and 14th days was higher than the control group,and this was statistically significant（P<0.05）.4.The relative expression of Opn mRNA:With the increase of time of force application,the expression of Opn mRNA showed a gradual trend of increasing,reaching the peak on the 10th day.The expression level of Opn mRNA in the experimental group was higher than the control group in various time periods and the comparison between the two groups on the 4th,7th,10th and 14th days was statistically significant（P<0.05）,and the comparison on the 1st day wasn’t statistically significant（P>0.05）.5.The expression of ERK protein:the expression of ERK protein in group A and B increased gradually since the 1st day of modeling and decreased on the 7th day after reaching the peak.The expression of ERK protein of group A was higher than group B at all times,and the comparison between group A and group B on the 1st,4th,and 7th days was statistically significant（P<0.05）;the comparison between the two groups on the 10th and 14th days was not statistically significant（P>0.05）.Conclusion:1.The combined use of rh TGF-β₁and rh PDGF-BB can increase the number of osteoclasts on the pressure side and accelerate the moving speed of orthodontic tooth,and have a positive effect on the periodontal tissue reconstruction of orthodontic tooth.2.The combined use of rh TGF-β₁and rh PDGF-BB can probably increase the expression of osteogenic gene Opn mRNA on the tension-side,thereby promoting osteogenesis.3.ERK protein participates in the periodontal tissue reconstruction of orthodontic tooth and the combined use of rh TGF-β₁and rh PDGF-BB has a certain promoting effect of the expression of ERK protein in periodontal tissue.