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对暴露于牙髓的人龋齿中6种细菌的流行、定位和牙髓反应特征进行了研究。此外，我们还研究了龋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。摘出的牙本质或牙髓细菌侵入的第三磨牙14例进行免疫组织学研究。所有样品均显示植物乳杆菌侵入修复牙本质。约90%的检查牙齿在修复牙本质中发现干酪乳杆菌、变形链球菌和微胃链球菌的入侵。这4种细菌在暴露于蛀牙的牙髓中也检出。我们研究了MCP-1、MMP-1和环氧合酶-2 （COX-2）在牙髓宿主反应中的特征。这些可以在所有发炎的牙髓中找到。MCP-1和MMP-1主要在细菌侵袭邻近区域的巨噬细胞中检测到，少量内皮细胞中也检测到。相反，表达cox -2的细胞大多分布在炎症细胞聚集区域附近。在COX-2表达细胞的主要区域，COX-2主要由成纤维细胞而不是巨噬细胞表达。为了阐明龋齿相关细菌与牙髓相互作用的机制，我们研究了COX-2在牙髓成纤维细胞中对变形链球菌的表达。变形s.m utans刺激的牙髓成纤维细胞cox -2特异性mRNA水平显著升高。本研究揭示了暴露于牙髓的深龋牙中所选细菌的实际情况。本研究还提示不可逆性牙髓炎时，牙髓成纤维细胞和巨噬细胞可能参与了牙髓组织的破坏。

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.