Q8 - MSTIM as a Therapeutic Strategy for CIPN

Introduction: : Magnetic stimulation uses electromagnetic fields to influence neurons, and to support the repair and growth of axons. Electromagnetic stimulation has emerged as a potential way to modulate neuronal activity, because as neurons communicate by sending electrical signals, magnetic fields have the ability to affect their currents. In a healthy neuron, electrical signals travel down the axon to the synaptic terminals, where they communicate with other nerve cells. These axons are wrapped in an insulating myelin sheath, which ensures that the signals are able to travel through efficiently. In this study, the magnetic stimulation device (MSTIM) was developed to stimulate axons in vitro. MSTIM aims to regenerate damaged axons, and to help reduce damage due to nerve degenerating diseases, such as Chemotherapy-Induced Peripheral Neuropathy (CIPN). The stimulation housing was 3D printed, and various frequencies were passed from the signal generator to the coil using an amplification circuit. This research focused on cultured Dorsal Root Ganglion (DRG) in vitro and were treated with Chemotherapy drugs. Magnetic stimulation was performed on the cultured neurons and low frequency square waves proved to be effective in axon regeneration. Magnetic stimulation offers a new therapeutic and less invasive approach by boosting neuronal communication and promoting the repair of damaged nerves.

Materials and

Methods: : The environment inside of the magnetic stimulation device closely resemble the conditions where healthy neurons are found in the body. The MSTIM instrument was fabricated using compartmentalized microfluidic chambers, created by casting Sylgard 184 Polydimethylsiloxane (PDMS) onto a mold, which was patterned with microchannels. The PDMS cured overnight in the oven at 80°C, were punched, and then were bonded to a glass slide, after ensuring that all materials were sterilized. Post bonding, the chambers were sterilized again under Ultraviolet light and were coated with Poly-D-Lysine and Laminin to encourage adhesion. After incubating for 10-12 hours, the chambers were then filled with media to support neuronal growth and function ahead of cell seating. The neurons were treated using either 5µM Oxaliplatin or 5µM Paclitaxel in order to mimic cancer induced axonal degeneration, and the cell viability and mitochondrial health results were observed using stained dyes. These results were recorded by live-imaging the wells at 0 hours, 24 hours, and 48 hours after staining. Using a Leica DMi8 microscope and Fiji-ImageJ, the axonal lengths and mitochondrial movement of the stained wells were measured, while the non-stimulated wells remained as the controlled variable. A magnetic stimulator was developed that emitted square pulses of 11mT approximately 2mm above the coil using a software and a waveform generator. These pulses were amplified with a 15V circuit. As the signal run through the amplifier circuit, a magnetic field is created, affecting the neurons.

Results, Conclusions, and Discussions:: Using the magnetic stimulation device, axon lengths of the same well were recorded over the course of 72 hours, using a control group with no frequency, and two independent groups of 10Hz and 100Hz square waves respectively. The average axon length was calculated and recorded over the course of three days. The recorded results of Day 1 initially indicated that the control group average axonal length was higher than either of the magnetically stimulated groups with an average of 210.8429µm, with the 100Hz group having an average length of 192.4576µm, and the 10Hz group with an average axonal length of 172.769µm. On Day 3 of the study, the results reported that the independent groups had both surpassed the control group in average axonal length, with the 100Hz group having an increase of 215.479% and the 10Hz group having a mean increase in length by 252.357% in comparison to Day 1, whereas the control group had only an increased average length of 143.838%.
These results indicate that while the response to the magnetic stimulation is not immediate, there is a delayed effect on the growth of the axon shown by the significant increase in average axonal length between Days 1 and 3. This could also suggest that prolonged magnetic stimulation has a greater effect on axonal growth as opposed to short term stimulation. This effect could be due to several different causes, such as cellular stress response and adjusting, signaling pathway activation, or cell density variability. While the effects of magnetic stimulation require further testing and research, it has shown to have a powerful effect on axonal growth rates and an increase in their length. Magnetic stimulation shows great potential for the growth and regeneration of neurons and their axons.

Acknowledgements and/or References (Optional)::