Effect Of All-trans Retinoic Acid On Immune Status Of M2 Macrophages In Periodontitis Mice

ObjectiveThe animal model of periodontitis was established by oral infection with Porphyromonas gingivalis(P.g).The effect of ATRA on the immune status of M2 macrophages in periodontitis mice was studied by intragastric administration of All-trans retinoic acid(ATRA)in P.g-induced periodontitis mice.MethodsFifteen 7-week-old C57BL/6 female mice were randomly divided into three groups:(1)Sham group(2)Simple periodontitis group(P.g+CMC)(3)All-trans retinoic acid treatment group(P.g+ATRA).Periodontitis mice induced by P.g were treated with all-trans retinoic acid by oral administration.The changes of body weight of mice infected with P.g were observed and samples were taken on the 42nd day after infection.The general periodontal tissue of mice was observed under stereoscopic microscope.After soft tissue removal,the distance from cemento-enamel junction(CEJ)to alveolar bone crest(ABC)was measured to evaluate alveolar bone resorption;HE(Hematoxylin-eosin)staining was used to observe inflammatory cell infiltration,connective tissue attachment loss and alveolar bone resorption in periodontal tissue.Detection of the proportion of F4/80~+CD206~+M2 macrophages in gingivae,abdominal cavity,spleen by flow cytometry;The difference of m RNA expression of Interleukin-10,Transforming growth factor-β1 and Arginase-1 in gingival tissue,abdominal cavity and spleen of mice was detected by Real-time Quantitative polymerase chain reaction.Results(1)The results of stereomicroscopy showed that the gingival index,tooth mobility and bone resorption in P.g+ATRA group were lower than those in P.g+CMC group(P<0.05).(2)The results of HE staining showed that in P.g+CMC group,the epithelium was separated from the tooth surface,the epithelium attached to the root of the enamel bone boundary,a large number of inflammatory cells infiltrated in the lamina propria,attachment loss and alveolar bone resorption were obvious,and bone resorption lacunae could be seen.In P.g+ATRA group,the connective epithelium was relatively intact,and there was no obvious loss of attachment and bone resorption.(3)The results of flow cytometry showed that the proportion of M2 macrophages in P.g+CMC group was lower than that in Sham group,while the proportion of M2 macrophages in P.g+ATRA group were higher than those in P.g+CMC group(P<0.01).(4)The results of q PCR showed that the expressions of IL-10,TGF-β1 and Arg-1m RNA in gingivae,abdominal cavity and spleen of P.g+ATRA group were higher than those of P.g+CMC group(P<0.01).Conclusions(1)In periodontitis mice,the immune response mediated by M2 macrophages decreased:the proportion of M2 macrophages decreased.(2)ATRA can effectively inhibit periodontitis induced by P.g and reduce alveolar bone resorption and connective tissue attachment loss.(3)ATRA can relieve periodontitis by enhancing the immune response of M2 macrophages in gingivae,abdominal cavity and spleen.