慢性根尖周炎模型大鼠表观遗传分子:溴结构域蛋白4的表达变化

Changes in the expression of bromodomain-containing protein 4,an epigenetic molecule,in a rat model of chronic periapical periodontitis

背景:根尖周炎是一种由感染牙髓内的细菌引起的根尖周组织的炎性疾病。溴结构域蛋白4在表观遗传的传递中起核心作用,研究表明溴结构域蛋白4在炎症及骨破坏中起到了重要的作用,但是其在慢性根尖周炎中的作用尚未见报道。目的:通过建立根尖周炎大鼠模型,探究溴结构域蛋白4在根尖周炎发展中的作用。方法:选取30只SD大鼠,随机分为5组,分别为0周组、1周组、2周组、3周组以及4周组,每组各6只。于左侧下颌第一磨牙行开髓术,暴露牙髓,分别于术后0,1,2,3,4周麻醉处死。多聚甲醛固定后取下颌骨,拍摄Micro-CT鉴定根尖周炎动物模型是否构建成功。脱钙1个月后制作冰冻切片,免疫组化法检测溴结构域蛋白4在慢性根尖周炎发展中的作用。结果与结论:①Micro-CT结果显示,大鼠根尖周炎动物模型在术后一两周出现牙周膜增宽及根尖阴影,根尖阴影面积随时间推移而增加;3周组和4周组阴影面积增加明显,差异有显著性意义(P<0.05);1周组、2周组、3周组以及4周组根尖阴影面积均高于0周组,差异有显著性意义(P<0.05),3周组及4周组相比差异无显著性意义(P>0.05);②免疫组化结果显示,1周组、2周组、3周组以及4周组的溴结构域蛋白4表达水平均高于0周组,差异有显著性意义(P<0.05);溴结构域蛋白4在2周组表达最高,差异有显著性意义(P<0.05);溴结构域蛋白4在1周组和4周组表达无明显差异(P>0.05);③提示溴结构域蛋白4在根尖周炎发生发展中起到了一定的作用,溴结构域蛋白4参与了慢性根尖炎的发展。

BACKGROUND:Apical periodontitis is an infectious inflammatory disease of the periapical tissue caused by bacterial infection.Bromodomain-containing protein 4(BRD4)plays a central role in epigenetic transmission.Studies have shown that BRD4 exerts an important role in inflammation and bone destruction;however,its role in chronic apical periodontitis has not yet been reported.OBJECTIVE:To establish a rat model of apical periodontitis to detect the role of BRD4 in the development of apical periodontitis.METHODS:Thirty Sprague-Dawley rats were selected and randomly divided into five groups,0-week group,1-week group,2-week group,3-week group,and 4-week group,with six rats in each group.Dental pulp of the left mandibular first molar was exposed by pulpectomy,and they were sacrificed at 0,1,2,3,and 4 weeks postoperatively.After paraformaldehyde fixation,the mandible was removed,and Micro-CT was taken to identify whether the animal model of periapical periodontitis was successfully constructed.Frozen sections were made 1 month after decalcification,and the role of BRD4 in the development of chronic apical periodontitis was detected by immunohistochemistry.RESULTS AND CONCLUSION:The results of Micro-CT showed that widened periodontal ligament and a certain apical shadow appeared in the rat apical periodontitis model at 1-2 weeks postoperatively.The shadow area increased over time and increased significantly at 3 and 4 weeks(P<0.05).The apical shadow area in the 1-,2-,3-,and 4-week groups was significantly higher than that of the 0-week group (P<0.05).However,there was no statistical difference between the 3-and 4-week groups(P>0.05).Immunohistochemical results showed that the expression of BRD4 in the 1-,2-,3-,and 4-week groups was significantly higher than that of the 0-week group(P<0.05).Highest BRD4 expression appeared in the 2-week group(P<0.05),but there was no significant difference between the 1-and 4-week groups(P>0.05).To conclude,BRD4 plays a certain role in the occurrence and development of apical periodontitis,suggesting that BRD4 participates in the development of chronic apical periodontitis.