Elucidation of the treatment mechanism of pulsed radiofrequency based on its antiinflammatory effects.

Pulsed radiofrequency (PRF) is recognized as an effective pain relief for treating chronic pain, though the mechanism of the analgesic effect remains unclear. Recent studies have focused on the potential anti-inflammatory effect in analgesia through PRF. Therefore, we investigated the anti-inflammatory effects of PRF using the knee pain mouse models induced by monoiodoacetic acid. Our findings demonstrated that PRF on the sciatic nerve significantly reduces knee pain, synovitis, and inflammatory cytokines, thereby supporting the hypothesis that PRF exerts an anti-inflammatory effect. Moreover, a tracer study and western blotting analysis revealed that PRF inhibited axonal transport in small dorsal root ganglion (DRG) neurons in the spinal cord and suppressed the secretion of calcitonin gene-related peptide (CGRP) and substance P (SP), both of which are associated with persistent inflammation, into the knee joint. Finally, the administration of both CGRP and SP agonists to the knee joint nullified the analgesic and anti-inflammatory effects of PRF. In conclusion, our studies revealed that PRF exerted analgesic effects based on anti-inflammatory effects through inhibition of CGRP and SP secretion caused by impaired axonal transport in small DRG neurons. We hope that these findings will lead to further dissemination of PRF treatment in the future.