The role of VLA proteins and fibronectin in the activation of synovial cells from rheumatoid arthritis.

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Title : The role of VLA proteins and fibronectin in the activation of synovial cells from rheumatoid arthritis.In this study, our aim was to clarify whether the interaction of the very late antigen (VLA) on synovial cells from rheumatoid arthritis patients and that ligand, fibronectin is involvd in the pathogenesis of rheumatoid arthritis synovitis. First, we examined the expression of VLA proteins (VLA2, 3, 4, 5) on synovial tissues. VLA3, 4 and 5 proteins were expressed on the synovial lining and sublining cells. Lymphocytes mainly expressed VLA-4. Endothelial cells expressed VLA2, 3 and 5 proteins.When we compared the expression of VLA-4 protein among peripheral blood T cells, synovial T cells and synovial fluid T cells, we found the increased expression of VLA-4 on synovial fluid T cells, suggesting the existence of VLA-4 inducing substance in synovial fluid. Next, we examined whether fibronectin and that fragments affect the proliferation of synovial cells. Although they did not so, they induced the shape change of synovial A cells. When we detected the phosphorylated proteins in synovial cells after the stimulation of fibronectin, we did not get the constant pattern. Recently it was reported that the vascular cell adhesion molecule-1 (VCAM-1) was the other ligand of VLA-4 protein. Thereby, we examined the expression of VCAM-1 in the synovial tissues from rheumatoid arthritis patients. That expression was shown on the synovial lining and sublining cells. Since most of these cells express the VLA-4 protein, the interaction of these cells might be attributed to the binding of VLA-4 and VCAM-1 molecules.