Charge-Balanced Electrical Stimulation Can Modulate Neural Precursor Cell Migration in the Presence of Endogenous Electric Fields in Mouse Brains

Abstract

Electric fields (EFs) can direct cell migration and are crucial during development and tissue repair. We previously reported neural precursor cells (NPCs) are electrosensitive cells that can undergo rapid and directed migration towards the cathode using charge-balanced electrical stimulation in vitro. Here, we investigate the ability of electrical stimulation to direct neural precursor migration in mouse brains in vivo. To visualize migration, fluorescent adult murine neural precursors were transplanted onto the corpus callosum of adult male mice and intracortical platinum wire electrodes were implanted medial (cathode) and lateral (anode) to the injection site. We applied a charge-balanced biphasic monopolar stimulation waveform for three sessions per day, for 3 or 6 d. Irrespective of stimulation, the transplanted neural precursors had a propensity to migrate laterally along the corpus callosum, and applied stimulation affected that migration. Further investigation revealed an endogenous EF along the corpus callosum that correlated with the lateral migration, suggesting that the applied EF would need to overcome endogenous cues. There was no difference in transplanted cell differentiation and proliferation, or inflammatory cell numbers near the electrode leads and injection site comparing stimulated and implanted non-stimulated brains. Our results support that endogenous and applied EFs are important considerations for designing cell therapies for tissue repair in vivo.

Electric Field ApplicationIn VivoRegulates Neural Precursor Cell Behavior in the Adult Mammalian Forebrain

“…The proportion of Iba11 cells (25.9 6 2.6% vs 29.4 6 1.9% Iba11 cells, stim-on and stim-off, respectively) was unaffected (p = 0.3), as was the proportion of proliferating microglia (Iba11 EdU1; 12.7 6 1.8% vs 11.3 6 1.8% Iba11EdU1 cells, stim-on and stim-off, respectively; p = 0.6; Fig. 3H) similar to previous findings (Morrison et al, 2019;Iwasa et al, 2019). Taken together, Figure 2 In vitro electrical stimulation increases cell number and regulates NPC differentiation.…”

“…Mice were anesthetized with 1.5-2.5% isoflurane, and the implanted electrode was interfaced with biphasic electrical stimulator (Popovic and Keller, 2005;Morshead et al, 2018) with pulse parameters: ,200 mA, with a ;500-mV cathodal pulse amplitude and a ;125-mV anodal pulse amplitude, at 500-and 2000-ms pulse widths, respectively, followed by a 1000-ms resting phase (Morrison et al, 2019;Iwasa et al, 2019) for a total time of 1 h. Following stimulation, mice were returned to their cages and killed 1 or 3 d later. For tissue analysis, mice were transcardially perfused with ice-cold PBS followed by 4% PFA for tissue analysis, or cervically dislocated and processed for the neurosphere assay as described Neurosphere assay section.…”

“…In the next series of experiments, we asked whether in vivo electrical stimulation had similar effects on endogenous NPCs in the periventricular region of the adult forebrain. Stimulating electrodes were implanted into the cortex with the cathode placed near the midline and the anode placed laterally, as previously reported (Morrison et al, 2019;Iwasa et al, 2019;Fig. 3A).…”

“…In vitro, NPCs undergo rapid and directed migration toward the cathodal direction of an externally applied EF (Babona-Pilipos et al, 2011Iwasa et al, 2017). In vivo, endogenous EFs exist within the brain parenchyma (Cao et al, 2013;Iwasa et al, 2019) and have been shown to promote NPC migration to the olfactory bulb. Further, application of external EFs can alter endogenous neuroblast migration (Cao et al, 2013) and guide migration of transplanted NPCs in rodents (Feng et al, 2017;Iwasa et al, 2019).…”

“…In vivo, endogenous EFs exist within the brain parenchyma (Cao et al, 2013;Iwasa et al, 2019) and have been shown to promote NPC migration to the olfactory bulb. Further, application of external EFs can alter endogenous neuroblast migration (Cao et al, 2013) and guide migration of transplanted NPCs in rodents (Feng et al, 2017;Iwasa et al, 2019). However, few studies have examined the direct effects of EFs on NPC kinetics (Ariza et al, 2010;Chang et al, 2011).…”