Electroceutical approach ameliorates intracellular PMP22 aggregation and promotes pro-myelinating pathways in a CMT1A in vitro model

Charcot-Marie-Tooth disease subtype 1A (CMT1A) is one of the most prevalent demyelinating peripheral neuropathies worldwide, caused by duplication of the peripheral myelin protein 22 (PMP22) gene, which is expressed primarily in Schwann cells (SCs). PMP22 overexpression in SCs leads to intracellular aggregation of the protein, which eventually results in demyelination. Unfortunately, previous biochemical approaches have not resulted in an approved treatment for CMT1A disease, compelling the pursuit for a biophysical approach such as electrical stimulation (ES). However, the effects of ES on CMT1A SCs have remained unexplored. In this study, we established PMP22-overexpressed Schwannoma cells as a CMT1A in vitro model, and investigated the biomolecular changes upon applying ES via a custom-made high-throughput ES platform, screening for the condition that delivers optimal therapeutic effects. While PMP22-overexpressed Schwannoma exhibited intracellular PMP22 aggregation, ES at 20 Hz for 1 h improved this phenomenon, bringing PMP22 distribution closer to healthy condition. ES at this condition also enhanced the expression of the genes encoding myelin basic protein (MBP) and myelin-associated glycoprotein (MAG), which are essential for assembling myelin sheath. Furthermore, ES altered the gene expression for myelination-regulating transcription factors Krox-20, Oct-6, c-Jun and Sox10, inducing pro-myelinating effects in PMP22-overexpressed Schwannoma. While electroceuticals has previously been applied in the peripheral nervous system towards acquired peripheral neuropathies such as pain and nerve injury, this study demonstrates its effectiveness towards ameliorating biomolecular abnormalities in an in vitro model of CMT1A, an inherited peripheral neuropathy. These findings will facilitate the clinical translation of an electroceutical treatment for CMT1A.

Implantable Electroceutical Approach Improves Myelination by Restoring Membrane Integrity in a Mouse Model of Peripheral Demyelinating Neuropathy

Although many efforts are undertaken to treat peripheral demyelinating neuropathies based on biochemical interventions, unfortunately, there is no approved treatment yet. Furthermore, previous studies have not shown improvement of the myelin membrane at the biomolecular level. Here, an electroceutical treatment is introduced as a biophysical intervention to treat Charcot-Marie-Tooth (CMT) disease-the most prevalent peripheral demyelinating neuropathy worldwide-using a mouse model. The specific electrical stimulation (ES) condition (50 mV mm^-1 , 20 Hz, 1 h) for optimal myelination is found via an in vitro ES screening system, and its promyelinating effect is validated with ex vivo dorsal root ganglion model. Biomolecular investigation via time-of-flight secondary ion mass spectrometry shows that ES ameliorates distribution abnormalities of peripheral myelin protein 22 and cholesterol in the myelin membrane, revealing the restoration of myelin membrane integrity. ES intervention in vivo via flexible implantable electrodes shows not only gradual rehabilitation of mouse behavioral phenotypes (balance and endurance), but also restored myelin thickness, compactness, and membrane integrity. This study demonstrates, for the first time, that an electroceutical approach with the optimal ES condition has the potential to treat CMT disease and restore impaired myelin membrane integrity, shifting the paradigm toward practical interventions for peripheral demyelinating neuropathies.

A Strategy for Magnetic and Electric Stimulation to Enhance Proliferation and Differentiation of NPCs Seeded over PLA Electrospun Membranes

Neural progenitor cells (NPCs) have been shown to serve as an efficient therapeutic strategy in different cell therapy approaches, including spinal cord injury treatment. Despite the reported beneficial effects of NPC transplantation, the low survival and differentiation rates constrain important limitations. Herein, a new methodology has been developed to overcome both limitations by applying a combination of wireless electrical and magnetic stimulation to NPCs seeded on aligned poly(lactic acid) nanofibrous scaffolds for in vitro cell conditioning prior transplantation. Two stimulation patterns were tested and compared, continuous (long stimulus applied once a day) and intermittent (short stimulus applied three times a day). The results show that applied continuous stimulation promotes NPC proliferation and preferential differentiation into oligodendrocytic and neuronal lineages. A neural-like phenotypic induction was observed when compared to unstimulated NPCs. In contrast, intermittent stimulation patterns did not affect NPC proliferation and differentiation to oligodendrocytes or astrocytes morphology with a detrimental effect on neuronal differentiation. This study provides a new approach of using a combination of electric and magnetic stimulation to induce proliferation and further neuronal differentiation, which would improve therapy outcomes in disorders such as spinal cord injury.

Electrical Stimulation Increases Axonal Growth from Dorsal Root Ganglia Co-Cultured with Schwann Cells in Highly Aligned PLA-PPy-Au Microfiber Substrates

Nerve regeneration is a slow process that needs to be guided for distances greater than 5 mm. For this reason, different strategies are being studied to guide axonal growth and accelerate the axonal growth rate. In this study, we employ an electroconductive fibrillar substrate that is able to topographically guide axonal growth while accelerating the axonal growth rate when subjected to an exogenous electric field. Dorsal root ganglia were seeded in co-culture with Schwann cells on a substrate of polylactic acid microfibers coated with the electroconductive polymer polypyrrole, adding gold microfibers to increase its electrical conductivity. The substrate is capable of guiding axonal growth in a highly aligned manner and, when subjected to an electrical stimulation, an improvement in axonal growth is observed. As a result, an increase in the maximum length of the axons of 19.2% and an increase in the area occupied by the axons of 40% were obtained. In addition, an upregulation of the genes related to axon guidance, axogenesis, Schwann cells, proliferation and neurotrophins was observed for the electrically stimulated group. Therefore, our device is a good candidate for nerve regeneration therapies.

An electroceutical approach enhances myelination via upregulation of lipid biosynthesis in the dorsal root ganglion

As the myelin sheath is crucial for neuronal saltatory conduction, loss of myelin in the peripheral nervous system (PNS) leads to demyelinating neuropathies causing muscular atrophy, numbness, foot deformities and paralysis. Unfortunately, few interventions are available for such neuropathies, because previous pharmaceuticals have shown severe side effects and failed in clinical trials. Therefore, exploring new strategies to enhance PNS myelination is critical to provide solution for such intractable diseases. This study aimed to investigate the effectiveness of electrical stimulation (ES) to enhance myelination in the mouse dorsal root ganglion (DRG) - an ex vivo model of the PNS. Mouse embryonic DRGs were extracted at E13 and seeded onto Matrigel-coated surfaces. After sufficient growth and differentiation, screening was carried out by applying ES in the 1-100 Hz range at the beginning of the myelination process. DRG myelination was evaluated via immunostaining at the intermediate (19 DIV) and mature (30 DIV) stages. Further biochemical analyses were carried out by utilizing RNA sequencing, qPCR and biochemical assays at both intermediate and mature myelination stages. Imaging of DRG myelin lipids was carried out via time-of-flight secondary ion mass spectrometry (ToF-SIMS). With screening ES conditions, optimal condition was identified at 20 Hz, which enhanced the percentage of myelinated neurons and average myelin length not only at intermediate (129% and 61%) but also at mature (72% and 17%) myelination stages. Further biochemical analyses elucidated that ES promoted lipid biosynthesis in the DRG. ToF-SIMS imaging showed higher abundance of the structural lipids, cholesterol and sphingomyelin, in the myelin membrane. Therefore, promotion of lipid biosynthesis and higher abundance of myelin lipids led to ES-mediated myelination enhancement. Given that myelin lipid deficiency is culpable for most demyelinating PNS neuropathies, the results might pave a new way to treat such diseases via electroceuticals.

Strategy for Designing a Cell Scaffold to Enable Wireless Electrical Stimulation for Enhanced Neuronal Differentiation of Stem Cells

Electrical stimulation (ES) offers significant advantages in modulating the behavior of stem cells on conductive scaffolds for neural tissue engineering. However, it is necessary to realize wireless ES to avoid the use of external wires in tissues. Thus, herein, a strategy is reported to develop a stem cell scaffold that allows wireless ES. A conductive annular graphene substrate is designed and grown by chemical vapor deposition; this substrate is used as a secondary coil to achieve wireless ES via electromagnetic induction in the presence of a primary coil. The substrate shows excellent biocompatibility for the culture of neural stem cells (NSCs). The results indicate that the applied wireless ES enhances neuronal differentiation, facilitates the formation of neurites, and does not substantially affect the viability and stemness maintenance of NSCs. Collectively, this system provides a strategy for achieving synergy between wireless ES and conductive scaffolds for neural regenerative medicine, which can be further utilized for the regeneration of other tissues.

Neural responses to electrical stimulation in 2D and 3D in vitro environments

Electrical stimulation (ES) to manipulate the central (CNS) and peripheral nervous system (PNS) has been explored for decades, recently gaining momentum as bioelectronic medicine advances. The application of ES in vitro to modulate a variety of cellular functions, including regenerative potential, migration, and stem cell fate, are being explored to aid neural degeneration, dysfunction, and injury. This review describes the materials and approaches for the application of ES to the PNS and CNS microenvironments, towards an improved understanding of how ES can be harnessed for beneficial clinical applications. Emphasized are some recent advances in ES, including conductive polymers, methods of charge transfer, impact on neural cells, and a brief overview of alternative methodologies for cellular targeting including magneto, ultrasonic, and optogenetic stimulation. This review will examine how heterogenous cell populations, including neurons, glia, and neural stem cells respond to a wide range of conductive 2D and 3D substrates, stimulation regimes, known mechanisms of response, and how cellular sources impact the response to ES.