The transforming growth factor-β (TGF-β) is a multifunctional cytokine modulating the onset and course of autoimmune disease as shown in experimental models. In synovial inflammation, there is a potential role for TGF-β in repairment, the inhibition of cartilage and bone destruction, and the down-regulation of immune response. The biologic effects of TGF-β depend on the cell type, the isoform and the availability of active TGF-β. We investigated TGF-β expression in patients with rheumatoid arthritis (RA) and compared to those of osteoarthritis (OA). And we determined a correlation between TGF-β1 and TGF-β2, and also the relationships between each TGF-β isoform and the parameters for disease activity of RA.

The study population consisted of 20 patients with RA and 20 patients with OA. The commercial ELISA kit was used to study TGF-β1 and TGF-β2 levels in peripheral blood (PB) and synovial fluids (SF).

1) While PB TGF-β1 level was of no difference between RA and OA patient groups, SF TGF-β1 level was higher in RA group than OA group. Similarly, PB TGF-β2 levels of RA and OA groups was not different, but SF TGF-β2 levels was higher in RA group than OA group. 2) In patients with RA, the TGF-β1 levels were higher than TGF-β2 in both the PB and SF, while in patients with OA, there showed higher readings for TGF-β1 than TGF-β2 in SF but no difference between TGF-β1 and TGF-β2 levels in PB. 3) In patients with RA, there were no correlations between PB TGF-β1 and PB TGF-β2 levels, nor between SF TGF-β1 and SF TGF-β2 levels. At the same way, there was no correlation between PB TGF-β1 and SF TGF-β1 levels, nor between each levels of TGF-β2 in patients with RA. 4) There was also no correlation between each TGF-β isoform and the parameters for disease activity such as ESR, CRP, tender joint count, swollen joint count, rheumatoid factor, and the duration of morning stiffness except between in PB TGF-β1 and disease duration of RA (r=0.637, p<0.01).

Each TGF-β isoforms were higher in synovial fluid of patients with RA than that of patients with OA. The data from the RA patients demonstrated different patterns of expressions of the isoforms depending on which compartment (PB or SF) was investigated. The quantification of different TGF-β isoform is thought to be important when TGF-β is measured under disease conditions of RA.