Shoulder stiffness (SS) is a disease that is fibroblastic and inflammatory in nature. Leptin is an adipokine-mediating the fibroblastic and inflammatory processes of various diseases. Our study tried to investigate the role of leptin in SS pathogenesis. Subacromial bursa from stiff and non-stiff shoulders were obtained for reverse transcription-polymerase chain reaction (RT-PCR) analysis and immunoblotting. Subacromial fluid was obtained for enzyme-linked immunosorbent assay. We showed that the expression level of leptin was lower in the subacromial bursae from the stiff shoulders in RT-PCR analysis (p < 0.001) and immunoblotting (p < 0.001). The concentration of leptin was also lower in the subacromial fluid derived from stiff shoulders. The leptin level in the subacromial fluid was positively associated with the constant score, total range of motion, flexion, abduction, and external rotation. The synovial fibroblasts derived from stiff shoulder-retrieved subacromial bursa were treated by 0, 1, and 3 μM leptin. Under RT-qPCR analysis, leptin was shown to dose-dependently decrease the transcription of IL-6, IL-10, and IL-13, but without impact on IL-1β and IL-4 (p < 0.001, p = 0.001, p = 0.001, p = 0.137, and p = 0.883 by ANOVA test, respectively). These results shed light on the role of leptin in orchestrating the disease processes of SS.
Keywords: interleukin-10; interleukin-1β; interleukin-6; interleutkin-13; leptin; shoulder stiffness.