Differential expression of cytokines and nitric oxide synthase isoforms in human rotator cuff bursae

Subacromial “bursitis” is a significant source of shoulder pain in patients with rotator cuff tear. The nature of the inflammatory processes in the subacromial bursal tissue is controversial and incompletely investigated. Macroscopically, subacromial bursa of patients with rotator cuff dysfunction have thickened walls, tears, and are erythematous. Histological studies, however, showed predominantly fibrovascular tissue with an inconsistent degree of synovial hyperplasia, fibrosis, and, usually, minimal “inflammatory cell infiltrate”.1 To characterise the nature of the processes in the subacromial bursa of painful shoulders we aimed at determining which cytokines and which isoforms of nitric oxide synthases (NOSs) are expressed in patients with rotator cuff tear. Cytokines have key roles in the induction and effector phases of all immune and inflammatory responses.2 Cytokines are also key molecules in soft tissue response to injury and wound healing.3-5 Nitric oxide, a free radical …