Study Of The Expression Of IntegrinαVβ3 In Periodontium And The Effect Of Lower Power Laser Irradiation During Experimental Tooth Movement

IntegrinαVβ3 is a extracellular matrix(ECM) receptor at cellular surfacethat mediate cell adhesion to ECM , associate with cytoskeletal and is involvedin introcellular signaling event.By far there have been a lot of reports about therole of integrinαVβ3 in angiogenesis and bone remodeling during variouspathological or physiological course.αVβ3 is the most important integrinexpressed by osteoclast.It plays an essential role not only in osteoclastprecursors differentiation, migration,and fusion,but also in osteoclast signalingevent , cytoskeletal organization and the formation of actin loop and the sealingzone.Furthermore, αVβ3 is necessary for osteoclast migration ,thus it affectthe expansion of bone resorption pit.Numbers of studies in vivo or in vitrosuggest that osteoclastic bone resorption can be inhibited through inference withthe functions of integinαVβ3.The primary function of integrinαVβ3 inosteoblast is participation in osteoblast precursors differentiation,and it does notplay much role in osteoblast adhesion. In addition ,integrinαVβ3 is necessary forvascular endothelial cell adhesion ,proliferation and migration.It inhibitendothelial cell Apoptosis and cooperate with various cytokines inangiogenesis.The expression of increase apparently in tumour,wound healing,and inflammation. Various αVβ3 inhibitors have been made to block someunfavorable angiogenesis ,which would be an important method in tumortherapy.However,there is very few reports about the expression of integrinαVβ3in periodontium during orthodontic tooth movement .We only found that NabeelTalic report the expression of integrinαVβ3 in osteoclasts,odontoclasts andthe epithelial rests of Malassez in periodontium during experimental toothmovement by Immunocytochemical studies in 2004,but the expression ofintegrinαVβ3 in other cells of periodontium and its changes at different timeafter the application of orthodontic force was not described.The purpose of ourexperiment is to examine the expression of integrinαVβ3 in various cells ofperiodontium at different time during experimental tooth movement by in situhybridization,by which we can propose the possible role of α V β 3 inperiodontium remodeling during tooth movement. Combined with the previousseries of studies we can understand the mechanism of the promotion effect oflower laser better.Thirty-five rabbits were used in this study. The animals were divided into 7groups on average: untreated(control), 1d,3d, 5d, 7d, 14d, and 21d group. Aelastic coil spring was ligated between the incisors and the first molar and exerta force of approximately 80 g. The incisors acted as anchors pulling the firstmolar mesially. Except the control group ,the right cheek of the rabbits receivedirradiation of lower power laser ,so the right side was designed as theexperimental side and the left side as the self-control.The 1d group received onetime irradiation,the 3d group received three times and the other groupscontinuously received five times,once a day. The animals from each group werekilled by perfusion with a fixative solution of 4% paraformaldehyde throughjugular vein at the time desiged.After perfusion, the maxillae were dissectedfree.Segments containing the first molar and its periodontium were cut fromeach side as specimens. After fixed in 4% paraformaldehyde and decalcified in10% ethylenediaminetetraacetic acid , the specimens were embedded inparaffin.The specimens were cut into sections including the areas mesial anddistal to the first maxillary molars and then the sections were stained witheosin-hematoxylin andβ3 subunit mRNA probe by in situ hybridization.Theexpression of integrin β3 subunit in the tension region and the compressionregion of the periodontium was investigated and half quantitative analysis wasmade by image analysis.Then the statistic analysis on gray scale value wasmade.In this study ,the expression integrin β 3 in periodontium of bothexperimental group and control group was demonstrated. In the alveolar bone ofall the groups,the positive stain was observed in osteoclasts, osteoblastprecursors and osteoblasts but not in bone cells. Furthermore,the stain intensitywas middling in osteoclastd , strong in osteoblast precursors but very weak inmature osteoblast.In the control group,positive stain was observed in theendothelial cell of a few new vessels but not of mature vessels.The expression ofintegrinβ3 in fibroblast and endothelial cell of new vessels begin to increasefrom the first day,and reached the peak on the fifth day after the force wasexerted. Comparing the experimental side with the control side,the expression ofintegrinβ3 in the compression region of the experimental side was apparentlyless than the control side on the first day and was apparently more than thecontrol side on the third day and the fifth day.Differently,the expression ofintegrinβ3 in the tesion region of the experimental side was apparently morethan the control side from the first day to the seventh day.In addition,theexpression of integrinβ3 was also observed in cementoclasts, cementoblasts andthe epithelial rests of Malassez.The result of this study suggest that integrinαVβ3 was involed in theneovascularization and bone remodeling of the periodontium,and the irradiationof lower power laser can effectively promote its expression,by which the lowerpower laser benefit the remodeling of the periodontium.In addition, integrinαVβ3 might also be involved in the remodeling of cementum and the functions ofthe epithelial rests of Malassez.