Interleukin-1-induced glenohumeral synovitis and shoulder pain in rotator cuff diseases

Synovitis of the subacromial bursa has been identified as a main source of shoulder pain in rotator cuff diseases. Little interest, however, has been paid into the synovitis of glenohumeral joint. The mRNA expression levels of interleukin-1beta (IL-1beta) and interleukin-1 receptor antagonists produced in the synovitis reflect the magnitude of inflammation. The present study was undertaken to determine the relationship between mRNA expression levels of IL-1beta and its receptor antagonists (secreted interleukin-1 receptor antagonist (IL-1ra) and intracellular IL-1ra) in the synovium of the glenohumeral joint and shoulder pain in rotator cuff diseases, analyzing the synovial specimens by reverse transcriptase polymerase chain reaction. Thirty-five patients with rotator cuff diseases were candidates. Based on the presence of cuff perforation, they were divided into two categories: 16 with non-perforating tears and 19 with perforating tears. The degree of shoulder pain was evaluated by use of a visual analogue scale. The pain degree of non-perforating tears was significantly greater than that of perforating tears (P < 0.01). In contrast, the expression levels of the cytokine-mRNAs were constitutively greater in perforating tears than in non-perforating tears (P < 0.01, respectively). The expression levels of the cytokine-mRNAs were inversely correlated with the degree of pain (IL-1beta: r = 0.930; secreted IL-1ra: r = 0.861; intracellular IL-1ra: r = 0.932, P < 0.001 respectively). These results suggest that the expression levels of the cytokine-mRNAs in the synovium of the glenohumeral joint contribute less to the generation of shoulder pain in rotator cuff diseases.