| Osteoclasts are the effector of bone resorption.Osteoclasts activation causes bone resportion.Osteoclasts are involved in orthodontic tooth movement.IGF-1 regulates the differentiation and function of ostecblasts and is associated with the bone remodeling process.The c-Src is a major tyrosine kinase activated by integrin engagement.In osteoclasts,c-Src appears to be the predominant mediator of integrinαvβ3 signaling events that influence osteoclast physiology and pathology,we investigated exogenous rhIGF-1 on the rate of tooth movement and osteoclast fuctional activation.The aim of the study was to investigate the effect of rhIGF-1 on c-Src in osteoclasts during the orthodontic tooth movement using an immunohistochemical and protein approach.Furthermore,we investigated exogenous rhIGF-1 on the rate of tooth movement and osteoclast fuctional activation.Objective:To investigate the expression of c-Src in osteoclasts during orthodontic tooth movement while local injecting rhIGF-1 in periodontal tissues in Sprague-Dawley(SD) rats.And to study changes of osteoclast amount in periodontal tissues in order to provide the further evidences for future clinical work.Methods:The first upper left maxillary molar was moved mesially by a closed-coil spring delivered a force of 50g for establishing orthodontic movement model in SD rats.80 male SD rats were randomly divided into two groups:the experimental group (B group) and the Control group(A group),with forty rats in each group.Each group was subdivided equally into five subgroups of eight(A1/B1,A4/B4,A7/B7,A10/B10,A14/B14),The experimental group were injected respectively with rhIGF-1 in dosages of 400ng(0.1ml) in the buccal submucosal area of the molar every other day,while the Control group received equivalent volumes of PBS.Eight rats in each subgroup were sacrificed at each of five time points(1,4,7,10 and 14 days) after appliance placement.The distance of the tooth movement was measured by using the stereomicroscope.Tissue sections around the first maxillary left molar were stained with tartrate-resistant acid phosphatase(TRAP) histochemistry to analyze the changes of the amount and distribution of osteoclasts on the compression side of tooth.The expression of c-Src in osteoclasts was detected by immunohistochemical techniques on the same side.Results:the amount of osteoclasts cells:①The number of osteoclasts appearing in the periodontal ligament space on the pressure side of the alveolar bone was increased markedly both in two groups.②The amount of osteoclasts in group B are more than +There were statistically significant differences in the amount of between A groups and B groups(P＜0.01).③There were no statistically significant differences between B4 and B1(P＞0.05),while there were statistically significant differences among every groups(P＜0.001).Tooth movement:①The distance of tooth movement were increased with time elapse.②Molars treated with rhIGF-1 moved mesially more rapidly than the A group.The distance of tooth movement of B group showed a significant increase compared with the control group(P＜0.01).③There were no statistically significant differences in the amount of between A1 and B1(P＞0.05). Other inside groups were statistically significant(P＜0.01).Expression of c-Src:The time-depended changes in B group were similar to those in A group during orthodontic tooth movement and the expression of c-Src was rapidly increased.The expression of in c-Src osteoclasts increased and get to the peak at 4 day in B group and at 7 day in A group.There were significant differences in the magnitude c-Src of expression between the two groups(P＜0.01).Conclusion:①Local injections of rhIGF-1 in the periodontal tissues might accelerate orthodontic tooth movement via enhanced the numbers of osteoclasts and improve bone resorption on the pressure side of the periodontal ligament.②c-Src can be upgraded by exogenous IGF-1 which promote bone resorption and accelerated orthodontic tooth movement.
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