Analysis of the relationship between the invasion of dental caries-associated bacteria and the host response of dental pulp in human carious teeth with pulp exposure

我们用免疫组织学方法检测了6种细菌在人龋齿暴露牙髓中的流行和定位，以及牙髓反应的特点。此外，我们还研究了龋病相关细菌与牙髓成纤维细胞之间的相互作用，以阐明不可逆牙髓炎中牙髓组织破坏的机制。取14个修复性牙本质和/或牙髓细菌侵袭的第三磨牙标本进行免疫组织学研究。所有标本均显示植物乳杆菌在修复性牙本质中的侵入。约90%的受检牙在修复牙本质中发现干酪乳杆菌、变形链球菌和微小消化链球菌的侵袭。在龋齿暴露的牙髓中也检测到这4种细菌。在牙髓宿主反应方面，我们检测了单核细胞趋化蛋白1、基质金属蛋白酶1和环氧合酶2的特性。这些都可以在所有发炎的牙髓中找到。MCP-1和MMP1主要表达于邻近细菌侵袭区的巨噬细胞，少量内皮细胞也有表达。而COX-2表达的细胞主要分布在靠近炎性细胞聚集区。在表达COX-2的细胞的这个优势区域，COX-2主要由成纤维细胞表达，而不是巨噬细胞。为了阐明龋病相关细菌与牙髓相互作用的机制，我们研究了变形链球菌对牙髓成纤维细胞COX-2表达的影响。变形链球菌刺激的牙髓成纤维细胞COX-2特异性mRNA水平显著升高。本研究揭示了所选细菌在牙髓暴露的深面龋齿中的实际情况。提示牙髓成纤维细胞和巨噬细胞可能参与了不可逆性牙髓炎的牙髓组织破坏。

We immunohistologically examined the prevalence and localization of 6 selected bacteria and the characteristics of pulpal response in human carious teeth with pulp exposure. Moreover, we investigated the interaction between caries-associated bacteria and pulpal fibroblasts to clarify the mechanism of pulpal tissue destruction in irreversible pulpitis.Fourteen specimens were obtained from the extracted carious third molars with bactcrial invasion in reparative dentin and/or dental pulp for the immunohistological study. All of the samples showed the invasion of Lactobacillus plantarum in the reparative dentin. About 90% of the examined teeth showed the invasion of Lactobacillus casei, Streptococcus mutans and Peptostreptococcus micros in the reparative dentin. These 4 bacteria were also detected in the dental pulp with carious exposure. In relation to the host response of dental pulp, we examined the characteristics of MCP-1, MMP-1 and cyclooxygenase-2 (COX-2). These could be found in all of the inflamed pulp. MCP-1 and MMP-1 were mainly detected in macrophages in the area adjacent to bacterial invasion, and they were also detected in a small number of endothelial cells. In contrast, COX-2-expressing cells were mostly distributed close to the area of accumulation of inflammatory cells. In this predominant region of COX-2-expressing cells, COX-2 was principally expressed by fibroblasts rather than macrophages.To elucidate the mechanism of the interaction between caries-associated bacteria and dental pulp, we investigated the expression of COX-2 in pulpal fibroblasts in response to S.mutans. The level of COX-2-specific mRNA from S.mutans-stimulated pulpal fibroblasts was significantly increased.This study revealed the actual condition of the selected bacteria in deep-carious teeth with pulpal exposure. And this study also indicated that pulpal fibroblasts as well as macrophages may participate in the pulpal tissue destruction in irreversible pulpitis.