Effect of Biphasic Electrical Current Stimulation on IL-1 beta-Stimulated Annulus Fibrosus Cells Using In Vitro Microcurrent Generating Chamber System

Abstract

Study Design. Human annulus fibrosus (AF) cells were stimulated in vitro with interleukin (IL)-1 beta and exposed to biphasic electrical currents. Objective. To identify the effect of biphasic electrical currents on the production of the extracellular matrix-modifying enzymes and infl ammatory mediators in IL-1 beta-stimulated AF cells. Summary of Background Data. Symptomatic disc degeneration is an important cause of chronic intractable lumbar pain and is associated with macrophage-mediated infl ammation in the AF. The inflammatory reaction relationship has not been studied in the AF. Methods. Human AF cells were treated with 1 ng/mL IL-1 beta and cultured in a microcurrent generating chamber system. The levels of matrix metalloproteinase (MMP)-1, MMP-3, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, IL-6, IL-8, vascular endothelial growth factor (VEGF), insulin-like growth factor, and nitric oxide (NO) were measured. Expression of cyclooxygenase 2 and type I collagen mRNA was analyzed. Results. Compared with unstimulated cells, IL-1 beta -stimulated AF cells produced significantly higher levels of MMP-1, MMP-3, IL-6, IL-8, NO, and VEGF, and lower levels of TIMP-1 and TIMP-2. Exposure to a 250-mV/mm field induced time-dependent increases in IL-6, NO, MMP-1, TIMP-1, VEGF, and insulin-like growth factor-1 production. The cells exposed to 500-mV/mm field produced significantly less MMP-1, TIMP-1, IL-6, and VEGF than unexposed cells (MMP-1, 17.2 +/- 4.7 ng/mL vs. 27.3 +/- 3.9 ng/mL, P < 0.05; TIMP-1, 12.4 +/- 3.3 ng/mL vs. 22.3 +/- 2.1 ng/mL, P < 0.02; IL-6, 2.5 +/- 0.9 ng/mL vs. 6.39 +/- 1.90 ng/mL, P < 0.05; and VEGF, 0.1 +/- 0.04 ng/mL vs. 0.44 +/- 0.15 ng/mL, P < 0.03). NO production was markedly increased at 500 mV/mm (P < 0.0001). Conclusion. We showed that exposure of IL-1 beta-stimulated AF cells to a 500 mV/mm inhibited MMP-1, IL-6, VEGF, and TIMP-1 production. The results suggest that biphasic electrical current stimulation may have efficacy in diminishing symptomatic disc degeneration.