Pulsed electromagnetic field stimulation enhances neurite outgrowth in neural cells and modulates inflammation in macrophages

Abstract

Nerve regeneration following traumas remains an unmet challenge. The application of pulsed electromagnetic field (PEMF) stimulation has gained traction for a minimally invasive regeneration of nerves. However, a systematic exploration of different PEMF parameters influencing neuron function at a cellular level is not available. In this study, we exposed neuroblastoma F11 cells to PEMF to trigger beneficial effects on neurite outgrowth. Different carrier frequencies, pulse repetition frequencies, and duty cycles were screened with a custom ad hoc setup to find the most influential parameters values. A carrier frequency of 13.5 MHz, a pulse repetition frequency of 20 Hz, and a duty cycle of 10% allowed maximal neurite outgrowth, with unaltered viability with respect to non-stimulated controls. Furthermore, in a longer-term analysis, such optimal conditions were also able to increase the gene expression of neuronal expression markers NeuN and Tuj-1 and transcription factor Ngn1. Finally, the same optimal stimulation conditions were also applied to THP-1 macrophages, and both pro-inflammatory (TNF-α, IL-1β, IL-6, IL-8) and anti-inflammatory cytokines (IL-10, CD206) were analyzed. The optimal PEMF stimulation parameters did not induce differentiation towards an M1 macrophage phenotype, decreased IL-1β and IL-8 gene expression, decreased TNF-α and IL-8 cytokine release in M1-differentiated cells, increased IL-10 and CD206 gene expression, as well as IL-10 cytokine release in M0 cells. The specific PEMF stimulation regime, which is optimal in vitro, might have a high potential for a future in vivo translation targeting neural regeneration and anti-inflammatory action for treating peripheral nerve injuries.