Abstract
Many inflammatory cells are known to be home to inflamed temporomandibular joint (TMJ) tissues by stimulation with cytokines and chemokines produced by inflammatory lesions in the TMJ. However, how the inflammatory cells affect the progression of inflammation in TMJ synovial tissues after their homing to inflamed TMJ site is still uncertain. Here, we isolated and cultured TMJ synoviocyte-like cells (TMJSCs) from murine TMJ tissues. We demonstrated that interleukin 1β (IL-1β) up-regulated expression of monocyte chemoattractant protein 1 (MCP-1) in TMJSCs. In addition, we found that IL-1β-treated TMJSCs strongly promoted migratory activity of mouse monocyte/macrophage RAW264.7 cells through secretion of MCP-1. On the other hand, IL-1β up-regulated expression levels of intracellular adhesion molecule 1 (ICAM-1), a leukocyte adhesion ligand in TMJSCs. In addition, IL-1β promoted cell–cell adhesion between TMJSCs and RAW264.7 cells. Intriguingly, we also found that cell–cell interactions mediated through soluble factors other than IL-1β and cell–cell adhesion molecules between IL-1β-stimulated TMJSCs and RAW264.7 cells synergistically augmented secretion of MCP-1 from these cells. Therefore, these results suggested that the IL-1β-induced recruitment of monocyte/macrophage lineage cells to inflamed synovial membranes in TMJ was further augmented by the cell–cell interaction-induced secretion of MCP-1 from the inflammation site, possibly resulting in prolonged inflammatory responses in TMJ synovial tissue.
Highlights
The temporomandibular joint (TMJ) is a synovial joint that is constituted between the mandibular fossa of the temporal bone and mandibular condyle
TMJ synoviocyte-like cell (TMJSC) highly expressed mRNA of α1 chain of collagen type I (colIα1) and vimentin compared with NIH3T3 cells as a standard fibroblast control, and hardly expressed that of CD45, a leukocyte common antigen, whereas RAW264.7 cells, a murine monocyte/macrophage cell line expressed that of CD45 (Figure 1B)
CC chemokine receptor 2 (CCR2) selective antagonist RS504393 significantly abrogated the interleukin 1β (IL-1β)-stimulated TMJSCs-promoted migration of RAW264.7 cells, indicating that monocyte chemoattractant protein 1 (MCP-1) secreted from IL-1β-stimulated TMJSCs promotes migratory activity of RAW264.7 cells
Summary
The temporomandibular joint (TMJ) is a synovial joint that is constituted between the mandibular fossa of the temporal bone and mandibular condyle. The intra-articular structures of TMJ are covered by the synovial membrane except for the articular cartilage of the eminence and fossa, the mandibular condyle, and the articular disc [1,2]. Temporomandibular disorders (TMD) are prevalent oral diseases, and the discomfort of TMJ pain, joint noise, and limitation to opening the mouth affect daily living, including eating and c 2018 The Author(s). Many proinflammatory cytokines have been detected in the synovial fluid of patients with TMD [5]
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