Differential Effects of IL-17A and TNF-α on Osteoblastic Differentiation of Isolated Synoviocytes and on Bone Explants from Arthritis Patients

Abstract

ObjectiveTNF-α and IL-17A act on fibroblast-like synoviocytes (FLS) and contribute to cytokine production, inflammation, and tissue destruction in rheumatoid arthritis (RA). The aim of this study was to compare their effects on osteogenic differentiation of isolated FLS and on whole bone explants from RA and osteoarthritis (OA) patients.MethodsFibroblast-like synoviocytes and bone explants were cultured in the presence or absence of TNF-α and/or IL-17A. Mineralization of extracellular matrix of FLS was measured by alizarin red and alkaline phosphatase activity (ALP). mRNA expression was analyzed by qRT-PCR for Wnt5a, BMP2, and RUNX2, key genes associated with osteogenesis. IL-6 and IL-8 levels were measured by enzyme-linked immunosorbent assays. Bone explant structure was quantified by histomorphometry.ResultsIn isolated OA and RA FLS, the combination of TNF-α and IL-17A induced matrix mineralization, increased ALP activity and expression of the osteogenesis-associated genes Wnt5a, BMP2, and Runx2, indicating an osteogenic differentiation. Wnt5a levels increased with TNF-α alone and in combination with IL-17A. BMP2 expression decreased with IL-17A and TNF-α after 12 h with OA FLS and 24 h with RA FLS. Runx2 expression decreased only with combination of TNF-α and IL-17A in OA FLS and with cytokines alone and combined in RA FLS. IL-6 and IL-8 production increased with IL-17A and/or TNF-α in both FLS and bone samples, especially from RA. Treatment of bone explants with cytokine combination increased ALP in OA but not RA samples. A decrease in bone volume was seen with cytokine combination, especially with RA explants.ConclusionDifferences were observed for the effects of IL-17A and TNF-α on osteogenic differentiation. In isolated FLS, increased osteoblastogenesis was observed, contrasting with the inhibitory effect in whole bone, specifically in RA. The net effect of IL-17A and TNF-α appears to depend on the disease state and the presence of other cells.

Evaluation of the anti-inflammatory effects of two platelet-rich gel supernatants in an in vitro system of cartilage inflammation

“…TNF-a (as IL-1) is a key protein implicated in the genesis of osteoarthritis [39,40] and inflammatory synovitis [41]. However, this cytokine is released to the synovial fluid at low concentrations to induce a normal turnover of the cartilage ECM via MMP gene up-regulation [42].…”

Wnt5a induces catabolic signaling and matrix metalloproteinase production in human articular chondrocytes

“…FN-f treatment has been shown to induce expression of pro-inflammatory cytokines in chondrocytes that include IL-1β, IL-6 and TNF-α 7, 32 that can induce Wnt5a expression 26, 28, 33 , suggesting that FN-f induction of Wnt5a could be mediated by one or more of these factors. However, we observed that Wnt5a expression increased as early as 6 hours after FN-f treatment (Fig.…”

Synergistic effect of interleukin-17 and tumour necrosis factor-α on inflammatory response in hepatocytes through interleukin-6-dependent and independent pathways

“…Neutrophils are key players in the initiation of the inflammatory response. As shown in various cells, including endothelial cells or skin and synovial fibroblasts, IL-17 can cooperate with TNF-a to induce in-vitro IL-8 and IL-6 secretion in synergy [16][17][18][19]. As shown in various cells, including endothelial cells or skin and synovial fibroblasts, IL-17 can cooperate with TNF-a to induce in-vitro IL-8 and IL-6 secretion in synergy [16][17][18][19].…”