AIM; To investigate the expression of Toll-like receptor 4 (TLR4) in a rat experimental pulpi-tis and periapical periodontitis model. METHODS: A model of experimental rat pulpal and periapical lesion was established and evaluated by histochemistry and X-ray picture. Immunohistochemical technique was applied to detect the expression of TLR4 in pulp tissues. TLR4 mRNA in periapical tissues were assayed by reverse transcription-polymerse chain reaction (RT-PCR). RESULTS: RT-PCR demonstrated that TLR4 mRNA was expressed in normal and inflamed periapical tissues, with higher expression in inflamed tissues. Immunohistochemical staining detected TLR 4 in odontoblast and some pulp capillary endothelial cells. No positive staining could be observed in the normal dental pulp fibroblasts. Inflammed pulp tissue exhibited intensified staining. CONCLUSION; The results demonstrated that TLR 4 may play an important role in the development of pulpitis and periapical periodontitis.%目的:建立大鼠实验性牙髓炎及根尖周炎模型,了解TLR4在大鼠牙髓和根尖周组织的表达情况.方法:采用单纯髓腔开放法建立大鼠实验性牙髓炎及根尖周炎模型,进行组织学及X线片观察.免疫组化检测TLR4在牙髓炎中的表达,RT-PCR检测TLR4在根尖周炎中的表达.结果:组织学及X线观察证实成功复制大鼠牙髓炎及根尖周炎模型,免疫组化结果表明大鼠正常牙髓组织成牙本质细胞层TLR 阳性表达,牙髓内部血管内皮细胞亦见表达,牙髓成纤维细胞未见表达.炎症牙髓组织TLR4表达较正常组增强.RT-PCR检测发现正常和炎症根尖周组织均有TLR4mRNA表达,炎症组表达较正常组增强.结论:TLR4在牙髓组织和根尖周组织均有表达并参与了牙髓根尖周炎症的发生和发展.
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