Expression Of IL-33 In Rat Model Of Chionic Apical Periodontitis

Objective This study investigated the expression of IL-33 and its ligand ST2 in animal models of chronic apical periodontitis,and determined its role in bone resorption or bone formation in apical inflammation by exploring its correlation with osteogenic factors OPG,Runx2,Osterix and osteoclast factor RANKL,then the role of IL-33 and ST2 in alveolar bone resorption or regeneration of periapical periodontitis was determined.Methods 30 male Sprague-Dawley rats weighing 250-350 g were randomly divded into 5 groups.All rats were anesthetized,the pulps of the mandibular first molar were exposed and left open to the oral environment.6 rats in each group were killed at day 0,7,14,21 and 28 after lesion induction.The mandibular bone was taken for X-ray to record the shadow area of apical tissue.Then hematoxylin and eosin(H&E)staining,immunohistochemistry and real-time PCR were performed to determine the trend of ST2?OPG?Osterix?Runx2 and RANKL over time,and the correlation between IL-33.The relationship between IL-33 / ST2 and the expression of related factors was analyzed to determine the extent of periapical lesions.Results 1.The X-ray results showed that the periodontal tissue structure was normal in the day 0,and there was no shadow on the apex.The shadow area of the apex gradually increased from the day 7 to the day 28,and reached a peak on the day 28(P<0.05).2.The histological analysis demenstrated that there was obvious inflammatory response and bone destruction at day 0.On the day 7,slight infiltration of acute inflammatory cells was observed.On the day 14,apical inflammation and alveolar bone resorption were observed.On the day 21,abscess appeared around the root tip,inflammatory cell infiltration and alveolar bone absorption.On the day 28,the apical abscess was enlarged and the alveolar bone was still absorbed.3.Immunohistochemistry finally showed that only a few IL-33,ST2,OPG,RANKL,Osterix,and Runx2 positive cells can be seen in normal periapical tissues.We found that the mean optical density of IL-33 and ST2 cells increased over time.OPG expression began to increase significantly at day 7 after operation,and gradually increased with time(p<0.05).However,in the early stage,RANKL increased with time,reaching the maximum at day 14,and then decreased gradually.The mean optical density of Runx2-positive cells gradually increased from day 7 to day 28(p <0.05);On the day 7,the expression of Osterix began to increase,and gradually increased with time,the mean optical density of positive cells increased significantly on the day 21 to day 28(p<0.05).4.Real-time q PCR results showed that IL-33,ST2,OPG,Runx2,and Osterix m RNA expression increased with time(p <0.05).However,the expression of RANKL m RNA increased with time,reached a maximum at 14 days,and then gradually decreased(p<0.05).In CAP lesions only,IL-33 m RNA levels were highly correlated with ST2 m RNA(r=0.99 P<0.05),OPG m RNA(r=0.99 P<0.05),Runx2 m RNA(r=0.97 P<0.05),and Osterix m RNA(r=0.99 P<0.05)and negatively correlated with RANKL m RNA(r=-0.30 P<0.05).Conclusion IL-33 is related to chronic apical periodontitis in rats,and the expression level increases with time.The expression of IL-33 is highly related to the osteogenic factors OPG,Runx2,and Osterix.In this experiment,IL-33 and it's receptor ST2 may promote bone formation and inhibit bone resorption by inducing osteogenic factor expression.