The Influence Of Ovalbumin Sensitization On Expressions Of RANKL And Cathepsin K Of Periodontium In Rats During Orthodontic Tooth Movement

Objective To establish a rat ovalbumin (OVA) sensitization model under actions of orthodontic force; to observe the morphological alterations of periodontium on the pressure side of orthodontic tooth movement at different time points between OVA sensitization rats and normal rats; to test the expression and change of osteoclasts, receptor activator of nuclear factor kappa B ligand (RANKL) and cathepsin K (CK) of periodontium; and to investigate whether OVA sensitization factors have impacts on orthodontic teeth movement.Methods Forty male SD rats aged at 8 weeks were selected and randomly divided into two groups:rats in the sensitization group (T1) received the intraperitoneal injection 1 ml of OVA sensitization solution on the 1st day and 7th day, respectively and intraperitoneal injection 1 ml of OVA activator on the 14th day while each rat in the non-sensitization group (T2) received the intraperitoneal injection 1 ml of normal saline (NS)at same time points setting as the force control group. On the 15th day, two groups of rats were drawn the whole blood in the inner canthus under general anesthesia and then the serum was separated. Serum OVA specific-IgE was tested by ELISA to confirm the success of OVA sensitization model, and then the orthodontic tooth movement model was established. When NiTi tension spring was placed on the first molar of left maxilla, with two incisors used as the anchorage, the first molar was mesially pulled by 40 g of force. The first molar of right maxilla was set as a non-force control. Those rats in two groups were sacrificed and made samples on the 1st,3rd,5th,7th, and 14th day after applying force and four at each time point. The mesial tooth movement distance of the first molar was measured. The morphological alterations of periodontium were observed by HE staining. The quantity of osteoclasts on the pressure side of the first maxillary molar was worked out by TRAP staining. Immunohistochemical staining was used for analysing of RANKL and CK expression in the periodontal ligament. The semi-quantitative analysis to RANKL and CK expression levels were carried out using Image-pro-plus6.0 image analysis system. The experimental results were analyzed and processed using SPSS 16.0 statistical software and GraphPad Prism 5.0 graphics software.Results(1) Rat OVA sensitization model and orthodontic tooth movement model were successfully established.(2) The distance of tooth movement:The tooth movement pattern in both T1L and T2L force groups were similar to the classic tooth movement pattern, but a few rebounds were turned up in Phase Ⅱ. Comparison among groups showed that the distance of tooth movement in T1L group was greater than that of T2L group on the 3rd day. The difference had statistical significance (P<0.05). Although the difference of tooth movement distance was existed at other time points, but it had no statistical significance (P>0.05).(3) HE staining:Regular changes of bone remodeling and bone resorption were tuned up on the pressure side of periodontium under 40 g of continued positive orthodontic force in both TiL and T2L force groups. The alterations of periodontium showed bone resoprtion on the 1st、3rd、5th day. After 7th day, bone resorption phenomenon was gradually reduced and the periodontium was beginning to repair on the 14th day.(4) TRAP staining:In the early stage of applying force, the quantity of mature osteoclasts had time dependence in both T1L and T2L groups and reached a peak on the 5th day. The quantity of cells was reduced gradually in the later stage of applying force. The quantity of osteoclasts at each time point in T1L group was higher than that of T2L group. But the difference only had statistical significance (P<0.05) on the 3rd,7th and 14th day.(5) Immunohistochemical staining:The RANKL and CK expression levels presented a trend from rise to decline along with time passing in both T1L and T2L groups. The expression levels in TiL group at each time point were higher than that of T2L groups. The difference of RANKL and CK expressions had statistical significance (P<0.05) on the 3rd,14th day and 5th,7th day, respectively. The RANKL and CK expression levels in both two groups showed a significant positive correlation (P<0.000).Conclusion Compared with the control group, the quantity of osteoclasts as well as the RANKL and CK expression levels have increased and the bone remodeling is more active on the pressure side of periodontium in OVA sensitization model rats. But those changes are still in accordance with the periodic change of periodontium reconstruction, which suggests the type I hypersensitivity generated in vivo OVA sensitization rats has promoted the bone remodeling activities on the pressure side of orthodontic movement.