Multisite Anodal Direct Current Stimulation Preserves Motor Function and Modulates Key Cellular Pathways in TDP-43...

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by degeneration of upper and lower motor neurons and disruption of normal motor network excitability. This study aimed to determine whether multi-site direct current stimulation (DCS) can modulate spinal motor circuit excitability in an experimental model of ALS and to evaluate its potential as a neuromodulation approach for preserving motor pathway function.

In an initial electrophysiological experiment, corticospinal-evoked muscle contractions were recorded using a force-displacement transducer to compare the effects of different multisite spinal electrode configurations on corticospinal output. Subsequently, two ALS mouse models, SOD1-G93A and TDP-43 A315T, underwent repeated in vivo multisite anodal DCS. Motor function was assessed using grid walking, hindlimb grip strength, and wire-hang tests across five time points. In the TDP-43 A315T model, motor neuron soma size was quantified using choline acetyltransferase immunostaining, whereas heat shock protein 70 (HSP70) expression and TDP-43/phosphorylated TDP-43 (p-TDP-43) aggregation were evaluated using western blotting and confocal imaging.

Multisite DCS produced the strongest suppression of corticospinal-evoked muscle contractions among all electrode configurations tested, indicating robust modulation of spinal excitability. In SOD1-G93A mice, repeated stimulation preserved motor performance across all behavioral assays, with the clearest differences emerging during later disease stages relative to unstimulated controls. In TDP-43 A315T mice, stimulation was associated with improved motor performance at the final testing point, preservation of motor neuron soma size, increased HSP70 expression, and significant reductions in both the number and size of cytoplasmic TDP-43 and pathological p-TDP-43 aggregates, consistent with enhanced proteostatic capacity and pathological protein clearance.

Multisite anodal DCS effectively modulates spinal excitability and preserves motor function in two mechanistically distinct mouse models of ALS. In the TDP-43 A315T model, these functional benefits are accompanied by preservation of motor neuron structure and molecular changes consistent with improved protein homeostasis. Together, these findings support multisite DCS as a promising neuromodulatory strategy for influencing disease-relevant mechanisms and slowing functional decline in ALS.