Faculty of Dentistry, Periodontal Biology Laboratory, Universidad de Chile, Santiago, Chile.
Faculty of Dentistry, Oral Pathology Laboratory, Universidad Andres Bello, Santiago, Chile.
J Periodontal Res. 2019 Oct;54(5):513-524. doi: 10.1111/jre.12654. Epub 2019 Apr 29.
Over the past few years, the importance of interleukin-22 (IL-22) and T-helper (Th)22 lymphocytes in the pathogenesis of periodontitis has become apparent; however, there are still aspects that are not addressed yet. Cells expressing IL-22 and aryl hydrocarbon receptor (AhR), transcription factor master switch gene implicated in the differentiation and function of Th22 lymphocytes, have been detected in periodontal tissues of periodontitis-affected patients. In addition, IL-22 has been associated with osteoclast differentiation and their bone resorptive activity in vitro. However, the destructive potential of IL-22-expressing AhR Th22 lymphocytes over periodontal tissues during periodontitis has not been demonstrated in vivo yet. Therefore, this study aimed to analyze whether IL-22-expressing CD4 AhR T lymphocytes detected in periodontal lesions are associated with alveolar bone resorption during experimental periodontitis.
Using a murine model of periodontitis, the expression levels of IL-22 and AhR, as well as the Th1-, Th2-, Th17- and T regulatory-associated cytokines, were analyzed in periodontal lesions using qPCR. The detection of CD4 IL-22 AhR T lymphocytes was analyzed in periodontal lesions and cervical lymph nodes that drain these periodontal lesions using flow cytometry. In addition, the expression of the osteoclastogenic mediator called receptor activator of nuclear factor-κB ligand (RANKL) was analyzed by qPCR, western blot, and immunohistochemistry. Finally, alveolar bone resorption was analyzed using micro-computed tomography and scanning electron microscopy, and the bone resorption levels were correlated with IL-22 and RANKL expression.
Higher levels of IL-22, AhR, and RANKL, as well as IL-1β, IL-6, IL-12, IL-17, IL-23, and TNF-α, were expressed in periodontal lesions of infected mice compared with periodontal tissues of sham-infected and non-infected controls. Similarly, high RANKL immunoreaction was observed in periodontal tissues of infected mice; however, few or absent RANKL immunoreaction was observed in controls. This association between RANKL and periodontal infection was ratified by western blot. Furthermore, a higher detection of CD4 IL-22 AhR T lymphocytes was found in periodontal lesions and cervical lymph nodes that drain these periodontal lesions in infected mice compared with non-infected controls. Finally, the increased IL-22 and RANKL expression showed positive correlation between them and with the augmented alveolar bone resorption observed in experimental periodontal lesions.
This study demonstrates the increase of IL-22-expressing CD4 AhR T lymphocytes in periodontitis-affected tissues and shows a positive correlation between IL-22, RANKL expression, and alveolar bone resorption.
近年来，白细胞介素-22（IL-22）和辅助性 T 细胞 22（Th22）淋巴细胞在牙周炎发病机制中的重要性已变得明显；然而，仍有一些方面尚未得到解决。在牙周炎患者的牙周组织中已经检测到表达 IL-22 和芳烃受体（AhR）的细胞，AhR 是一种转录因子，是 Th22 淋巴细胞分化和功能的主要开关基因。此外，IL-22 与体外破骨细胞分化及其骨吸收活性有关。然而，在体内，IL-22 表达的 AhR Th22 淋巴细胞对牙周炎期间牙周组织的破坏潜能尚未得到证实。因此，本研究旨在分析在实验性牙周炎中，在牙周病变中检测到的表达 IL-22 的 CD4 AhR T 淋巴细胞是否与牙槽骨吸收有关。
使用牙周炎的小鼠模型，通过 qPCR 分析牙周病变中 IL-22 和 AhR 以及 Th1、Th2、Th17 和 T 调节相关细胞因子的表达水平。通过流式细胞术分析引流这些牙周病变的牙周病变和颈淋巴结中 CD4 IL-22 AhR T 淋巴细胞的检测。此外，通过 qPCR、western blot 和免疫组织化学分析破骨细胞生成介质核因子-κB 受体激活剂配体（RANKL）的表达。最后，通过微计算机断层扫描和扫描电子显微镜分析牙槽骨吸收，并将骨吸收水平与 IL-22 和 RANKL 表达相关联。
与假感染和未感染对照的牙周组织相比，感染小鼠的牙周病变中表达更高水平的 IL-22、AhR 和 RANKL 以及 IL-1β、IL-6、IL-12、IL-17、IL-23 和 TNF-α。同样，在感染小鼠的牙周组织中观察到高 RANKL 免疫反应；然而，在对照中观察到很少或没有 RANKL 免疫反应。western blot 证实了 RANKL 与牙周感染之间的这种关联。此外，与未感染对照相比，在感染小鼠的牙周病变和引流这些牙周病变的颈淋巴结中检测到更高水平的 CD4 IL-22 AhR T 淋巴细胞。最后，增加的 IL-22 和 RANKL 表达与实验性牙周病变中观察到的牙槽骨吸收增加呈正相关。
本研究证明了在牙周炎受累组织中 IL-22 表达的 CD4 AhR T 淋巴细胞增加，并显示 IL-22、RANKL 表达与牙槽骨吸收之间存在正相关。
