The effects of mechanical strain on synovial fibroblasts

Purpose: Arthritic diseases of the temporomandibular joint, such as rheumatoid arthritis and osteoarthritis, suggest that inflammatory mediators and metalloproteinases may play a role in their pathogenesis. Recent clinical evidence from physical therapy and other modalities has shown a significant decrease in temporomandibular joint symptoms in patients with early disease. This project examines the effect of mechanical strain on synovial fibroblasts' production of inflammatory mediators including prostaglandin E2 (PGE2) and proteinases. Materials and Methods: An established synovial fibroblast cell line (HIG-82) was grown to confluency in modified Eagle's medium supplemented with 10% fetal calf serum. The monolayer of fibroblasts was then subjected to mechanical strain using the Flexercell Strain Unit (Flexcell International Corporation, McKeesport, PA) at 3 cycles per minute, with 10 seconds' elongation of up to 24% and 10 seconds of relaxation. Levels of PGE2 were determined by radioimmunoassay using commercially available product and measured in nanograms per milliliter of supernatant. Proteinases collagenase, gelatinase, and stromelysin were measured by H3 radioactive labeling of acidic anhydride to the specific substrate. Enzymatic proteolysis of the radiolabeled substrate was then measured in supernate as units per milliliter. Statistical analysis of all results was performed using Student's t test in triplicate. Results: PGE2 levels of mechanically activated cells was 18.1 ± 13.4 ng/mL, with control levels being 58.0 ± 9.2 ng/mL. This is a statistically significant decrease, between strained and unstrained cells with P