The Expression Of IL-1β In The Periodontal Tissues Of Dogs During Root Resorption And The Effect Of IL-1β On The Expression Of MMP-1, TIMP-1in Human Periodontal Ligament Cells

Root resorption is a serious complication during orthodontic treatment, which iscalled orthodontic-reduced root resorption.The reported incidence of rootresorption during orthodontic treatment varied from26%to100%, since theinvestigation and measurement methods were different. Mild root resorptionusually will not cause tooth loosening and any uncomfortableness while moderateor severe root resorption will lead to the loosening and even loss of teeth,whichaffects the health of teeth seriously. The occurrence of root resorption is a sterile,local inflammatory process with characteristic inflammatory symptoms. Theextracellular matrix (ECM) is a kind of macromolecule which plays an importantrole in creating the environment of the occurrence and development of cellmorphology. The matrix metalloproteinases (MMPs) is a protein involved in ECM degradation. In normal physiological conditions, the transcription of MMPs,plasminogen activation and the interaction with specific extracellular matrix arein normal levels and inhibited by endogenous inhibitors. Tissue inhibitors ofmetalloproteinases (TIMPs) are specific inhibitors of MMPs and inhibit theactivities of the MMPs in the tissues. In this study, the orthodontic root resorptionmodels were established on dogs. We investigated specific high expression ofinterleukin1(IL-1β) in the periodontal tissues to analyse the inflammatoryfactor-mediated mechanisms of the occurrence and development of rootresorption. Subsequently, we analysed and discussed the orthodontic rootresorption mechanism by investigating MMP-1, TIMP-1expression by PCR andimmuneocytochemistry when the cultured hPDLCs were exposed to IL-1β.ObjectiveTo analyze and discuss the orthodontic root resorption mechanism.MethodsAnimals model of root resorption were established on dogs. Semi-quan-titativedetection by PCR was used to test the difference of expression of IL-1β mRNAin the periodontal ligament between root resorption and normal tissues. Thecultured hPDLCs were exposed to IL-1β at various dosages (0.01ng/ml,0.1ng/ml,1ng/ml,10ng/ml,0ng/ml for control group) and various times (6h,12h,24h).PCRand immunocytochemistry were used to detect MMP-1,TIMP-1expression.Results1IL-1β expression was detected in the periodontal ligament of the toothwith root resorption on dogsBy PCR electrophoresis, a clear band in the250bp location (IL-1β primer sizeis243bp) was detected of the periodontal ligament of the tooth with root resorption, while it was not detected of the periodontal ligament in the controlgroup. The results suggest that endogenous IL-1β mRNA expression in the rootresorption group was higher than the control group.2Expression of MMP-1, TIMP-1in hPDLCs stimulated by IL-1β2.1Expression of MMP-1, TIMP-1mRNA concentration dependenceStatistical analysis showed that: compared with the control group,0.01ng/mland0.1ng/ml group had no significant effects on MMP-1expression (ANOVA, p=0.165, p=0.205);1ng/ml and10ng/ml group could promote the expression ofMMP-1(p<0.05), there was no significant difference of MMP-1expressionbetween these two groups. Compared with the control group, TIMP-1expressionin0.01ng/ml,0.1ng/ml,1ng/ml,10ng/ml groups decreased (p<0.05) and10ng/mlgroup had more effects than the other groups (p<0.05). The results suggested thatIL-1β on hPDLCs could promote MMP-1expression and inhibit the expressionof TIMP-1.10ng/ml group had the strongest effect on the expression of MMP-1and TIMP-1.2.2The expression of MMP-1and TIMP-1at various times with IL-1βstimulatedOn the basis of the above experimental results, we selected IL-1β concentrationand subsequently stimulated hPDLCs with10ng/ml IL-1β at various times (6h,12h,24h). The statistical analysis showed that: compared with the controlgroup,MMP-1expression appeared to increase (p<0.05) in the10ng/ml IL-1βstimulated for12h group and the expression of MMP-1raised a higher degree in24h group than the12h group (p<0.05). TIMP-1expression began to appear onthe inhibition (p<0.05) in the10ng/ml IL-1β for6h group, this inhibitiongradually increased with time, the strongest inhibition was at24h (p<0.05).2.3The expression of MMP-1and TIMP-1protein When hPDLCs were stimustimulated with concentration of10ng/ml IL-1β for24h; MMP-1protein expression was higher than the control group and theexpression of TIMP-1protein was lower than the control group. These resultssuggested that IL-1β could promote the expression of MMP-1protein and inhibitthe expression of TIMP-1protein, which was consistent with the results of themRNA.Conclusion1In the process of orthodontic root resorption, the periodontal ligament is in theinflammatory factor-mediated condition.2IL-1β can promote the expression of MMP-1in hPDLCs and inhibit theexpression of TIMP-1, which may be one of the mechanisms of the molecularbiology of root resorption.