| Background:Rheumatoid arthritis (RA) is a kind of autoimmune disease, which is characterized by chronic and progressive joint corrosive damage. A series of inflammatory cytokines are produced due to immune response, and subsequently lead to bone destruction including alveolar bone. It is little known how orthodontic tooth movement under the disorder of bone metabolism caused by RA It is reported by a number of recent studies that Adiponectin (AD), an adipocyte-derived hormone, is involved in inflammation and bone destruction caused by RA. But the precise effect is not clear.Objective:This study is to investigate the orthodontic tooth movement under the status of RA, and the effect of AD on the inflammatory reaction and tooth movement of RA, meanwhile, the underlying mechanism of bone metabolic disorders of RA by using the model of orthodontic tooth movement such a good bone reconstruction model. The study will provide the experimental evidence and the theoretical basis for the clinical orthodontic therapy of RA.Methods:Sixty12-week-old male SD rats weighing300-360g were selected and separated randomly into three groups:the control group (Group A), the RA group (Group B) and the AD interference group (Group C). An animal model of collagen II-induced arthritis (CIA) was established to the rats of Group B and C. The three groups of rats were fixed with the orthodontic device at the same time following the success of CIA. Then, AD (10ug/ml) was administered intraperitoneally (0.2ml, q48h) to Group C, and other groups received a PBS injection (0.2ml, q48h). At day3, day7, day14and day21of treatment,5rats of each group were killed. Venous blood was collected, which would be used for testing the concentration of the IL-1α and TNF-α by Enzyme Linked Immunoadsorbent Assay (ELISA). The right maxilla bones,5per group, were collected and the distance between the first and second molar was measured. Two maxilla bones were made into paraffin slices for HE and TRAP staining. Further histological analysis of periodontal tissue was evaluated and the number of osteoclast cells on the pressure side was counted as well. The rest of maxilla bones were used for total RNA isolation and subsequently supplied to real-time PCR (RT-PCR) to test the mRNA expression of RANKL and OPG. All statistical analyses were performed by using SPSS software version17.0. Statistical significances were calculated by analysis of variance (ANOVA) for multiple comparisons, followed by one-way comparisons between different groups at the same time point by paired t test. P<0.05was considered to be a significant difference.Results:1. The distance of tooth movement:The distance increased during the three weeks after treatment. The distance in Group B and Group C was significantly larger (P<0.05) compared with Group A on day7,14and21, but there was no obvious difference between Group B and Group C except on day21(P<0.05).2. Histological analysis:HE staining:The histological changes in the periodontium of Group B and C were similar. On the pressure side, the space of periodontal membrane width decreased obviously, and the number of bone resorption pits and osteoclasts on the alveolar bone increased. Severe destruction of alveolar bone was observed; On the tension side, the space of periodontal membrane increased, however, osteogenesis was not active, new bone deposited less. In Group A, the space of periodontal membrane also decreased, and osteoclast and alveolar bone resorption appeared, however, the damage of alveolar bone was slighter than Group B and C. On day21, there was obvious bone deposition; On the tension side, large osteoblasts appeared and osteogenesis was active.TRAP staining:The number of osteoclast on pressure side all reached a peak on day14. The numbers in both group B and group C were higher that of group A (P<0.05); it was less in Group C than Group B and from day14, there was significant difference (P<0.05).3. ELISA:The concentrations of IL-1α and TNF-α in serum reached at peak at day14in all groups. Compared with Group A, the IL-1α and TNF-α levels in Group B and Group C were significantly higher (P<0.05). The concentration of IL-1α and TNF-α in Group C was slightly lower than that in Group B on day7and14, but significantly lower on day21(P<0.05).4. RT-PCR:The mRNA expression of RANKL in3groups all rose gradually to a peak on day14, then decreased with the time points. Compared with A group, both B and C group were higher than A group all the time (P<0.05). C group was slightly lower than B group, but significantly lower on day14and21(P<0.05); However the mRNA expression of OPG was different. On day3and7, there were no significant differences between B and A group (P>0.05), while on day14and21, the difference were significant (P<0.05). No significant differences between C and A group were detected (P>0.05). The mRNA expression of OPG in C group was higher than B group, but only on day14(P<0.05).Conclusion:1. In the orthodontic treatment of RA rats, the bone metabolic was imbalanced, characterized by the faster speed of tooth movement and the heavier damage of alveolar bone. Moreover, there was a tendency of periodontitis, which should be kept in mind during clinical practice. It is necessary to control the inflammation first and follow the soft-strength principle strictly.2. The increasing number of osteoclasts and the active bone resorption are important pathological feature of bone metabolic disorders in both RA and orthodontic tooth movement.3. The rats in AD interference group showed slower tooth movement speed and slighter alveolar bone destruction, which indicate that AD might be anti-inflammatory fator and inhibitor of bone resorption in RA. But the precise mechanism remains to be further studied. |
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