DETECTION OF INTERLEUKIN-1 IN THE CARTILAGE OF PATIENTS WITH OSTEOARTHRITIS - A POSSIBLE AUTOCRINE PARACRINE ROLE IN PATHOGENESIS/

The interleukin-1 (IL-1) cytokines stimulate the synthesis of degradat ive enzymes in joint tissues and may play a role in the pathological j oint destruction in osteoarthritis (OA). In this study, we have used i mmunohistochemistry and Western blot analysis to identify IL-1 in huma n OA cartilage. IL-1 alpha and IL-1 beta were evident in chondrocytes at the articular surface, as well as distributed throughout the cartil age. In many specimens, IL-1 beta but not IL-1 alpha was detected as a diffuse staining of the extracellular matrix especially surrounding s uperficial zone chondrocytes. Although chondrocyte-associated IL-1 alp ha and IL-1 beta were detected in most specimens, cartilages exhibitin g early osteoarthritic changes had the highest intensity of staining a nd the highest frequency of positive cells. Western blot analysis reve aled intense immunoreactive bands corresponding to the 35 kDa precurso r form of IL-1 alpha in all four chondrocyte lysates tested. The proce ssed 18 kDa IL-1 beta species was present in only one of four chondroc yte lysates, and there was no clear evidence of precursor form within these cells. The results of this study indicate increased IL-1 alpha i n cartilage showing early degenerative changes, suggesting an autocrin e/paracrine role for this cytokine in OA pathogenesis.