<b>Pro-inflammatory Cytokine Production in Co-culture of Human Monocytes and Synovial Fibroblasts from the Human Temporomandibular Joint </b>

Abstract

The synovial membrane is composed of fibroblast-like cells (synovial fibroblasts) and macrophage-like cells. Synovial fibroblasts and monocytes/macrophages are believed to interact and to play a critical role in the development of synovial inflammation. In this study, we investigated the protein production of pro-inflammatory cytokines in co-culture of synovial fibroblasts isolated from the temporomandibular joint (TMJ) and monocytes isolated from peripheral blood. Monocytes that had attached to the plastic surface after culture for 3 days in RPMI containing 10% FBS, exhibited two types of morphologies:ʠfried eggʡandʠspindle-likeʡ . Both types of monocytes stained positive for the macrophagespecific markers CD14 and CD68. Synovial fibroblasts were co-cultured with these monocytes for 12 days. Synovial fibroblasts or monocytes were also cultured alone for 12 days. The conditioned media were collected every 3 days, following which fresh medium was added to each culture. The protein concentrations of IL-1 , IL-6, and IL-8 in the conditioned media were measured using ELISA. The protein production of IL-1 , IL-6 and IL-8 was greatly increased in the co-culture of synovial fibroblasts and monocytes compared to each monoculture. These data suggest that interaction between monocytes/ macrophages and synovial fibroblasts is likely to contribute to the promotion of, and to increase the inflammatory condition in the TMJ.

Biomarkers for Temporomandibular Disorders: Current Status and Future Directions

“…Moreover, higher degrees of IL-1α and IL-1β in the synovial fluid of patients with TMD were indicated in various works of research [27]. Meanwhile, few studies examined fibroblasts, which were cultured from TMJ synovial fluid [32,35] and TMJ synovial biopsies (immunohistochemistry) [46,52], leading to consistent results. Furthermore, a study by Ok et al 2018 [34] demonstrated that the level of urinary pyridinoline (PYD) and deoxypyridinoline (DPD) were increased in patients with TMDs.…”

“…Moreover, several synovial, serum and urinary proteins were found to exhibit important diagnostic tool for TMDs (Table 1). [33] Wilkes classification Synovial fluid IL-8, sTNFR1, sTNFR2 and sIL-6R Ok et al, 2018 [34] RDC-TMD Urine PYD and DPD Watanabe et al, 2017 [35] Arthroscopy of the TMJ TMJ synovial fibroblasts IL-1β, IL-6, and IL-8…”