Pulsed electromagnetic fields reduce acute inflammation in the injured rat‐tail intervertebral disc

Pro‐inflammatory cytokines are recognized contributors to intervertebral disc (IVD) degeneration and discogenic pain. We have recently reported the anti‐inflammatory effect of pulsed electromagnetic fields (PEMF) on IVD cells in vitro. Whether these potentially therapeutic effects are sufficiently potent to influence disc health in vivo has not been demonstrated. We report here the effect of PEMF on acute inflammation arising from a rat‐tail IVD injury model. Disc degeneration was induced by percutaneously stabbing the Co6‐7, Co7‐8, and Co8‐9 levels using a 20‐gauge needle. Seventy‐two (72) rats were divided into three groups: sham control, needle stab, needle stab+PEMF. Treated rats were exposed to PEMF immediately following surgery and for either 4 or 7 days (4 hr/d). Stab and PEMF effects were evaluated by measuring inflammatory cytokine gene expression (RT‐PCR) and protein levels (ELISA assay), anabolic and catabolic gene expression (RT‐PCR), and histologic changes. We observed in untreated animals that at day 7 after injury, inflammatory cytokines (interleukin [IL]‐6, tumor necrosis factor α, and IL‐1β) were significantly increased at both gene and protein levels (P < .05). Similarly, catabolic factors (MMP [metalloproteinases]‐2, MMP‐13 and the transcriptional factor NF‐kβ gene expression) were significantly increased (P < .05). At day 7, PEMF treatment significantly inhibited inflammatory cytokine gene and protein expression induced by needle stab injury (P < .05). At day 4, PEMF downregulated FGF‐1 and upregulated MMP‐2 compared to the stab‐only group. These data demonstrate that previously reported anti‐inflammatory effects of PEMF on disc cells carry over to the in vivo situation, suggesting potential therapeutic benefits. Though we observed an inhibitory effect of PEMF on acute inflammatory cytokine expression, a consistent effect was not observed for acute changes in disc histology and anabolic and catabolic factor expression. Therefore, these findings should be further investigated in studies of longer duration following needle‐stab injury.