A Novel Method to Achieve Precision and Reproducibility in Exposure Parameters for Low-Frequency Pulsed Magnetic Fields in Human Cell Cultures

Published October 21, 2o22

Abstract

The effects of extremely low-frequency electromagnetic field (ELF-MF) exposure on living systems have been widely studied at the fundamental level and also claimed as beneficial for the treatment of diseases for over 50 years. However, the underlying mechanisms and cellular targets of ELF-MF exposure remain poorly understood and the field has been plagued with controversy stemming from an endemic lack of reproducibility of published findings. To address this problem, we here demonstrate a technically simple and reproducible EMF exposure protocol to achieve a standardized experimental approach which can be readily adopted in any lab. As an assay system, we chose a commercially available inflammatory model human cell line; its response to magnetic fields involves changes in gene expression which can be monitored by a simple colorimetric reporter gene assay. The cells were seeded and cultured in microplates and inserted into a custom-built, semi-automated incubation and exposure system which accurately controls the incubation (temperature, humidity, CO2) and magnetic-field exposure conditions. A specific alternating magnetic field (<1.0% spatial variance) including far-field reduction provided defined exposure conditions at the position of each well of the microplate. To avoid artifacts, all environmental and magnetic-field exposure parameters were logged in real time throughout the duration of the experiment. Under these extensively controlled conditions, the effect of the magnetic field on the cell cultures as assayed by the standardized operating procedure was highly reproducible between experiments. As we could fully define the characteristics (frequency, intensity, duration) of the pulsed magnetic field signals at the position of the sample well, we were, for the first time, able to accurately determine the effect of changing single ELF-MF parameters such as signal shape, frequency, intensity and duty cycle on the biological response. One signal in particular (10 Hz, 50% duty cycle, rectangular, bipolar, 39.6T) provided a significant reduction in cytokine reporter gene expression by 37% in our model cell culture line. In sum, the accuracy, environmental control and data-logging capacity of the semi-automated exposure system should greatly facilitate research into fundamental cellular response mechanisms and achieve the consistency necessary to bring ELF-MF/PEMF research results into the scientific mainstream.

Conclusions

This paper describes the development and characteristics of a functional exposure and incubation system and its application for the control of ELF-MF and PEMF in biological samples. The potential to efficiently screen effective ELF-MF/PEMF parameters and resolve complex parameter setups to gain a better understanding of underlying mechanisms of magnetic field action on biological systems was demonstrated. In combination with a highly sensitive and well-established biological inflammatory response assay, it was possible to generate highly significant and reproducible magnetic-field effects of a 37% decline in a TLR4-dependent inflammatory response with a 10 Hz and 50% duty-cycle rectangular signal. For rectangular signals, we observed that not the frequency alone, but also the altered magnetic-field duration 𝑇𝐷, related to duty cycle and frequency by Equation (1), was responsible for the biological effect. A 𝑇𝐷=50 ms induces a significant anti-inflammatory effect in the range of 27–37%. A lowered 𝑇𝐷 reduced the effect size significantly below <10%. However, short-pulsed fields with triangular shape and 𝑇𝐷≤100s≪26.32 ms could also induce significant anti-inflammatory effects of a similar order of magnitude to the rectangular signals. Thus, 𝑇𝐷 is not the only effective parameter. Possibly, different magneto-sensitive mechanisms could be involved on different time scales for 𝑇𝐷, which correspond to different frequency ranges due to the Fourier analysis of the magnetic signal. Obviously, more extensive magnetic-field parameter studies are necessary allowing clarification on a deeper level of understanding of the fundamental mechanisms.

These findings show that the HEK-Blue™ hTLR4 reporter cell line is an excellent model system for studying immune modulatory effects of ELF-MF/PEMF fields. The power of our custom-built exposure and incubation system for identifying and characterizing magnetic-field effects in living systems is demonstrated by the anti-inflammatory effects reproduced in a commercially available model cell-culture system.

Using this exposure and incubation system, it is possible to obtain reliable, accurate and fast information regarding the understanding of different parameters of ELF-MF effects in different types of human cell cultures. In particular, low-intensity exposure levels (𝐵0=39.46T) with different signal shapes will be relevant for a wide audience of researchers. Such groups are hereby invited to participate in this endeavour to explore new therapy options. Relevant magnetic-field parameters can be further varied and magnetic field research can be accelerated with the system described. Looking forward, there is a smaller version of the system planned, which can be more easily adapted to established lab procedures and protocols.

In conclusion, the synthesis of a robust and sensitive biological readout system and a technically well-controlled environment demonstrate the potential to generate reproducible results in studying magneto reception and allow systematic exploration of the effect of critical ELF-MF/PEMF parameters for given cell models/systems. The experiments shown present proof of principle that the exposure and incubation system can be used both to develop future applications of magnetic-field therapy in medicine and to elucidate the underlying fundamental cellular response mechanisms triggered by magnetic fields. Given that this methodology is easily applicable to multiple cell types, this would mean a great leap forward in terms of reproducibility within the research field by installing identical systems in different laboratories, to investigate magneto-receptive effects by the application of nearly identical magnetic fields.

Link to full article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9598188/