Effects Of Nifedipine On NF-kB Signaling Pathway And Osteogenesis During Premaxillary Suture Expansion In Young Adult Rats

Rapid maxillary expansion(RME)is often used to solve the problems of dentition congestion,dental arch stenosis,anterior teeth inversion and so on.In the process of rapid maxillary expansion,under the action of expansion force,the distraction osteogenesis process is activated,and the new bone begins to deposit in the middle palatal suture.However,there are still many problems in the process of rapid maxillary expansion,such as recurrence,the most common complications after arch expansion.Some scholars have found that in the process of rapid maxillary expansion,the expanded middle palatal suture can not form enough new bone during the arch expansion stage and maintenance period,which is one of the important reasons for recurrence.Therefore,in the process of rapid maxillary arch expansion,promoting the formation and deposition of new bone in suture is an important measure to reduce the recurrence of rapid maxillary expansion.At present,there are many methods to promote the formation of new bone in bone suture,including low energy laser,transforming growth factor,diphosphate,vitamin and so on.Some scholars have reported that nifedipine can inhibit the expression of NF-kB,while NF-kB can inhibit osteoblast formation,while others report that the distraction osteogenesis mechanism of premaxillary suture is similar to that of middle palatal suture.The osteogenesis of premaxillary suture in rats was observed by intraabdominal injection of nifedipine at a dose of 50 mg /kg once a day.Purposes:The rat models of rapid expansion of premaxillary suture was established toobserve the presence of NF-kB signaling pathway,proliferation of osteoblasts and the expression of osteogenic factor OCN,BMP-2 in the anterior palatal suture.Effects of nifedipine on NF-kB signaling pathway,proliferation of osteoblasts and expression of osteogenic factor OCN,BMP-2 during the expansion of anterior palatal suture in rats.Methods:Forty-five 8-week-old male SPF rats were randomly divided into 3 groups:group A(15 rats)with negative control group(Control group,CM),group B(15 rats)without expansion of bow and group B(group B),group B(n = 15),group B(n = 15)and group B(n = 15).Group C(n = 15)received intraperitoneal injection of nifedipine(50 mg/kg.)at the same time as the expansion of the bow.The experimental arch expansion time was 1,4,7 days.The expansion spring was made by0.016-inch oz-bend band with a force value of 2.00 ±0.20 N.Under local anesthesia of chloral hydrate,the expansion spring was installed between the maxillary incisors and fixed with light-cured resin.The reaming spring was fixed with light-cured resin in the maxillary incisors under local anesthesia with chloral hydrate.The maxillary specimens were taken and fixed immediately with 10% formalin solution.The width of the premaxillary suture was measured by Micro-CT.After 6 weeks of decalcification,the expression of NF-kB and osteogenic factors was observed by HE,immunohistochemistry and immunofluorescence staining.Results:1.At the beginning of the experiment,the body weight of all the participating rats was in the range of 280 ±10 g.The weight of rats in group A increased evenly with time.In group B,the weight of rats in group C decreased significantly in the first two days after the expansion of the bow,and gradually increased in the third day.2.After RME,the width of the premaxillary suture and the morphological changes of the tissue: the width of the premaxillary suture gradually broadened under the action of tensile force,and increased with the time of arch expansion at 1、4、7days;The new bone was found in Micro-CT on the 4th day,which was almost parallel to the direction of tensile force.HE staining showed that with the expansionof the premaxillary suture,the formation of collagen fibers was also observed with the increase of the number of days of expansion,accompanied by obvious neovascularization.After Masson staining,there were obvious collagen fibers,new cartilage and chondrocytes in the premaxillary suture.3.Expression of osteogenic markers: compared with the control group,the expression of OCN,BMP-2 in the experimental group and nifedipine group was significantly higher than that in the control group.Conclusions:In this study,we established the rat maxillary expansion model to detect the expression of IL-1β,P65 and OCN,and compared the effects of nifedipine suspension on the bone remodeling after premaxillary sutures expansion.in conclusion:1.The larger expansion force value(2.00 ± 0.20N)can effectively open the premaxillary sutures of young adult SD rats.2.In the process of expansion,IL-1β expression,with the increase of expansion time;activation of NF-kB signaling pathway,P65 expression increased with the expansion time.3.During the expansion of the arch,mechanical force can stimulate the expression of OCN,and OCN expression increases with time.4.During the expansion of the bow,nifedipine may inhibit the activation of NF-kB signaling pathway,which may promote the proliferation of bone cells and increase the expression of OCN.