Modulation of the response of rheumatoid arthritis synovial fibroblasts to proinflammatory stimulants with cyclic tensile strain

Abstract

Although physical therapy has been shown to be an effective method for treatment of rheumatoid arthritis, a thorough investigation on the impact of mechanical signals upon the complex cytokine network associated with pathogenesis has not yet been conducted. In the current study, our research group investigated the effect of mechanical stimulation on primary and immortalized rheumatoid arthritis synovial fibroblasts (RASFs) through analysis of secreted proteins using multiplex immunoassay. Equibiaxial tensile strain was applied to 2D cultures grown on collagen-coated, flexible silicone membranes at a magnitude of 10% and a frequency of 0.5 Hz using the Flexcell System. After 24 h, supernatant was removed and assayed for the following cytokines: IL-1β, IL-6, IL-8, VEGF, FGF-2, GM-CSF, MCP-1, RANTES, TNF-α. The results were compared to unstimulated control groups. Mechanical stimulation alone only impacted secretion of IL-8 by primary RASFs. However, in the presence of proinflammatory mediators (TNF-α or IL-17), application of cyclic tensile strain increased secretion of a number of proteins by both primary and immortalized RASFs, although the responses were not analogous. In contrast, MCP-1 secretion was decreased when mechanical stimulation was applied in combination with IL-17 to primary cultures. In general, the study suggests that cyclic tensile strain can be used to modulate the effects of proinflammatory stimulants on RASFs; however, given the highly variable results, more research will be necessary to identify the pathways that are implicated in mechanotransduction.