High IL-6 synthesis in cultured fibroblasts isolated from radicular cysts

Objective: Inflammatory cytokines have been reported to be related with inflammation and expansion of jaw cysts. In this study, to examine the relationship between radicular cysts and inflammatory cytokines, it was found that there was notable unique evidence on cytokine synthesis from fibroblasts isolated from radicular cysts. Methods: The expression of such cytokines, namely, interleukin-1β, IL-1β, IL-6, IL-8, IL-10, tumour necrosis factor-α (TNF-α), interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1), and granulocyte-macrophage colony-stimulating (GM-CSF) mRNA, in nine radicular cysts was examined and compared with that detected in six specimens of healthy gingival mucosa. Furthermore, separating all fibroblasts from their respective radicular cysts, healthy gingival mucosa, and healthy periodontal ligaments, these fibroblast groups were cultured without stimulators and a supernatant for each was obtained to analyse IL-1β, IL-6, IL-8, TNF-α, and IFN-γ by ELISA. Results: Differences between radicular cysts and healthy gingival mucosa were not clearly shown by the expression of cytokine mRNA. Analysing inflammatory cytokine synthesis in fibroblast groups from these three kinds of tissues, surprisingly, the levels of IL-6 mRNA and protein were recognised to be higher in fibroblasts of radicular cysts than in those of control tissues by ELISA and a real-time RT-PCR. Significant differences in the cultured supernatants of these fibroblast groups were not recognised in the release of IL-1β, IL-8, TNF-α, and IFN-γ by ELISA. Conclusions: From these results, it was suggested that fibroblasts inducing IL-6 production might play important roles in the expansion of radicular cysts. It is considered that fibroblasts around radicular cysts may lead to high IL-6 synthesis over time in chronic inflammation.