Expression of cathepsin B, D and L protein in juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common childhood autoimmune rheumatic disease and like rheumatoid arthritis (RA), it is characterized by inflammation and the progressive destruction of joints. In RA, cathepsins as proteinases play a major role in destroying synovial tissue and cartilage matrix. So far no data on cathepsin expression in pannus tissue of JIA patients exist. The aim of this study was to characterize the expression levels of cathepsins B, D, H, and L in JIA and to compare them with those in RA. Synovectomy tissue from 16 JIA and 12 RA patients was investigated for cathepsin expression levels by Western blot analysis. Expression of cathepsins B, D and L was on comparable levels in the synovectomy tissue of JIA and RA patients. The following graduation of expression was determined: cathepsin D > cathepsin L > cathepsin B. Cathepsin H was neither found to be expressed in JIA nor in RA patients. The expression levels of cathepsins in pannus tissue showed no clear difference between patients with systemic JIA and patients with monoarticular JIA. In summary, the comparable expression of cathepsins B, D and L in RA and JIA synovectomy tissue suggests that they may play a similarly important role in destroying synovial tissue and cartilage matrix in the course of JIA and RA.