Electrical Stimulation of C6 Glia-Precursor Cells In Vitro Differentially Modulates Gene Expression Related to Chronic Pain Pathways

Abstract

Glial cells comprise the majority of cells in the central nervous system and exhibit diverse functions including the development of persistent neuropathic pain. While earlier theories have proposed that the applied electric field specifically affects neurons, it has been demonstrated that electrical stimulation (ES) of neural tissue modulates gene expression of the glial cells. This study examines the effect of ES on the expression of eight genes related to oxidative stress and neuroprotection in cultured rodent glioma cells. Concentric bipolar electrodes under seven different ES types were used to stimulate cells for 30 min in the presence and absence of extracellular glutamate. ES consisted of rectangular pulses at 50 Hz in varying proportions of anodic and cathodic phases. Real-time reverse-transcribed quantitative polymerase chain reaction was used to determine gene expression using the ∆∆C_q method. The results demonstrate that glutamate has a significant effect on gene expression in both stimulated and non-stimulated groups. Furthermore, stimulation parameters have differential effects on gene expression, both in the presence and absence of glutamate. ES has an effect on glial cell gene expression that is dependent on waveform composition. Optimization of ES therapy for chronic pain applications can be enhanced by this understanding.

Keywords: cell culture; electrical stimulation; gene expression; glial cells; oxidative stress.

Figure 1

Results (mean ± SD; n = 4) from the serial dilution of a glial cell pool representative experiment. Data are shown by plotting the corrected A_595nm per 45 min value as a function of volume of cell pool added to the well (with the volume of complete DMEM also added to yield a final volume of 100 µL; for example, if 20 µL of cell pool was seeded then 80 µL of medium was also added).

Figure 2

Light microscopy images (40×) of the same cell population before Cathodic PR ES (left) and after ES (right).

Figure 3

Heat map illustrating the effect of gene expression by glutamate alone (Stressed Cells column) and ES on stressed cells relative to the expression of untreated control cells (No-Glu_No-ES). White color indicates gene expression equivalent of untreated control cells.