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

我们用免疫组织化学方法检测了6种细菌在人龋坏暴露牙髓中的分布和分布情况，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，以阐明不可逆性牙髓炎中牙髓组织破坏的机制。所有标本均显示修复性牙本质中有植物乳杆菌侵入。约90%的受检牙可见干酪乳杆菌、变形链球菌和微小消化链球菌侵入修复性牙本质。这4种细菌也在龋暴露的牙髓中检测到。在牙髓的宿主反应方面，我们检测了MCP-1、MMP-1和环氧合酶-2（考克斯-2）的特性。这些都可以在所有发炎的牙髓中找到。MCP-1和MMP-1主要在邻近细菌侵袭区域的巨噬细胞中检测到，在少量内皮细胞中也检测到。相反，表达考克斯-2的细胞主要分布在靠近炎症细胞聚集的区域。在这个主要区域的考克斯-2-表达细胞，考克斯-2主要是由成纤维细胞，而不是macrophages.To阐明的机制，龋相关细菌和牙髓之间的相互作用，我们调查了考克斯-2在牙髓成纤维细胞中的表达响应于变形链球菌。变形链球菌刺激牙髓成纤维细胞后，考克斯-2特异性mRNA的表达水平显著升高，揭示了所选细菌在牙髓暴露的深龋牙中的实际情况。本研究还表明，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.