【背景】近年の、電磁界ばく露の非熱的な生物学的影響の可能性に関する多数のインビトロ研究は、代表的には初代細胞または細胞株の単一層を対象として行われている。しかしながら、インビボの細胞は3次元構造であるため、2次元の細胞層系は生理学的妥当性を欠く。単一層での研究では、細胞－細胞間及び細胞－細胞外基質間の相互作用が生きている組織とは異なるため、実験結果を物差しにしてインビボ系について判断することには慎重さが望まれる。【目的】上述の問題を克服するために、我々は細胞足場材なしの3次元細胞培養系を用い、900MHzの電磁界による電気生理学的影響の探索を行うこと。【方法】一定の回転で解離心筋細胞を球形に再凝集させ、微小電極アレイを用いて、この細胞スフェロイド（多細胞球体）の（活動電位の）無侵襲細胞外記録を行った。ストリップライン型ばく露装置を用い、この3次元細胞培養系をパルス電磁界にばく露させた。【結論】ばく露パラメータを慎重に選択すれば、微小電極アレイチップの電極および導線による電磁界の不均一性が細胞スフェロイド内の電磁界分布に与える影響は小さくできることが見出された。
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The study aimed to achieve an improved physiological relevance by a 3D in vitro model. Several studies have already revealed distinct differences between monolayer and 3D cell cultures in terms of cellular behavior. By using rotation-mediated scaffold-free spheroids histotypic self-organization is enabled.
In the first part of experiments, cardiac myocyte spheroids were exposed to pulsed electromagnetic fields (field 2). In a second part the pulse frequency of the electromagnetic field was adjusted to the beat rate of a single spheroid (field 3). By varying the pulse frequency in the range of 5-20%, possible direct interferences of electromagnetic field frequencies with the beat rate were explored. In positive controls the beat rate of spheroids was investigated as a function of temperature (field 1).
None of the analyzed electrophysiological parameters were significantly changed under exposure. Thus, the data showed no influence of the electromagnetic field on cardiac contractions.
However, the data showed that spheroids under the present conditions are excellent candidates for electromagnetic field exposure experiments. Electromagnetic field disturbances due to the recording electrodes were only minor. Compared to monolayer cultures, spheroids are contractile for a longer period of time and thus are a promising cell culture system for long-term exposure studies.
