Interleukin‐1β stimulates stromal‐derived factor‐1α expression in human subacromial bursa

Abstract

Chemokines produced by synoviocytes of the subacromial bursa are up-regulated in subacromial bursitis and rotator cuff disease. We hypothesized that SDF-1α production in bursal synoviocytes may be induced by local cytokines such as interleukin IL-1β and IL-6. Subacromial bursa specimens were obtained from patients undergoing shoulder surgery. Bursal specimens were stained with anti-human antibodies to IL-1, IL-6, and SDF-1α by immunohistochemistry and compared to normal and rheumatoid controls. Bursal cells were also isolated from specimens and cultured. Early passaged cells were then treated with cytokines (IL-1β and IL-6) and SDF-1α expression was measured by ELISA and RT-PCR. SDF-1α, IL-1β, and IL-6 were expressed at high levels in bursitis specimens from human subacromial bursa compared to normal controls. In cultured bursal synoviocytes, there was a dose-dependent increase in SDF-1α production in the supernatants of cells treated with IL-1β. SDF-1α mRNA expression was also increased in bursal cells treated with IL-1β. IL-6 caused a minimal but not statistically significant increase in SDF-1α expression. SDF-1α, IL-1β, and IL-6 are expressed in the inflamed human subacromial bursal tissues in patients with subacromial bursitis. In cultured bursal synoviocytes, SDF-1α gene expression and protein production are stimulated by IL-1β. IL-1β produced by bursal syvoviocytes and inflammatory cells in the human subacromial bursa is an important signal in the inflammatory response that occurs in subacromial bursitis and rotator cuff disease.