この研究は、実験用のミリ波（MMW）ばく露装置として製作された94 GHzアプリケータを用いてマウス胚性幹細胞由来の神経細胞にMMW刺激を与え、それに伴って起きるかも知れないCa2+ 振動の変化をリアルタイムで調べた。その結果、18.6 kW / m2の公称電力密度でのMMW照射は、Ca2+ 活性を表している細胞でのCa2+スパイク発生頻度を有意に増加させた；N型カルシウムチャネル、ホスホリパーゼC酵素、およびアクチン細胞骨格が、Ca2+スパイク発生増加の仲介に関与しているようであった；94 GHz電磁界によるアクチンミクロフィラメントの再構成は、Ca2+活性の変化だけでなく、細胞の生体力学的な変化にも重要な役割を果たしているように見えた；観察されたMMWへの細胞応答の多くは、熱的に誘発された効果と類似していたが、例えば、ある種の神経細胞で観察された94 GHz電磁界誘発性の一酸化窒素産生は、42 ℃までの熱による細胞加熱では再現できなかった；しかしながら、MMWばく露チャンバ内で、細胞レベルでの加熱速度の複雑で不均一な微視的分布が生じていた可能性は排除できない、と報告している。
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To study real-time changes in the Ca2+ spiking patterns using P19-derived neuron-like cells (i.e. neuronal cell differentiation was specifically induced) in response to a millimeter wave exposure.
Transient elevations in cytosolic Ca2+ concentration, referred to as spikes, are a nearly universal mode of signaling in both excitable and non-excitable cells. While the role of oscillatory Ca2+ signals is not fully understood, it is evident that spatial and temporal patterns of Ca2+ dynamics (e.g. spiking amplitude and frequency and spatial distribution) are important characteristics of cellular regulatory pathways.
To elucidate the possible Ca2+ influx/efflux pathways the cells were treated with pharmacological inhibitors (amongst others ω-conotoxin GVIA: N-type Ca2+ channel blocker, thapsigargin: Ca2+ ATPase inhibitor, cytochalasin D: actin polymerization inhibitor, U73122: phospholipase C inhibitor).
To study the effect of millimeter wave exposure on actin filament organization, the authors used fibroblasts, which are known to express abundant actins (in contrast to P19-derived neuronal cells).
In a control series of experiments, cells were investigated at the desired temperature in the range 25-42°C.
|ばく露時間||continuous for up to 60 min|
|チャンバの詳細||exposure chamber consisting of 24 mm x 30 mm cover slips separated by cover-slip-thick spacers|
|ばく露装置の詳細||fixed tuned Gunn oscillator connected to WR10 waveguide operating in TE10 mode, directed to the cell exposure chamber placed on a microscope stage; 2.54 mm x 1.27 mm exposure exit aperture touching the glass of the exposure chamber|
Millimeter wave exposure at 18.6 kW/m² significantly increased the Ca2+ spiking frequency in active cells (i.e. in cells exhibiting Ca2+ oscillation). However, at the lower power densities (3.1-7.8 kW/m²), no statistically significant increase in Ca2+ spiking frequency compared to unexposed cells was found.
The N-type calcium channels, phospholipase C, and actin cytoskeleton appear to be involved in mediating increased Ca2+ spiking (as shown by specific inhibitors which effectively suppressed spiking). Reorganization of the actin microfilaments by a 94 GHz field seems to play a crucial role in modulating not only Ca2+ activity but also cell biomechanics (decrease of cell elasticity). A millimeter wave exposure at 18.6 kW/m² for 30 minutes caused some damage to the actin structure (in contrast, a hyperthermia treatment at 42°C for 30 min did not result in substantial actin reorganization).
Many but not all observed cellular responses to millimeter wave exposure were similar to thermally induced effects. For example, exposure to a 94 GHz field induced nitric oxide production in some morphologically distinct neuronal cells that could not be reproduced by thermal heating of the cells up to 42°C.
The data may be beneficial in developing novel approaches to control cellular behaviors by external physical stimulation for tissue engineering and regenerative medicine applications.