この研究は、ヒト骨髄間葉幹細胞（hBM-MSCs）の神経分化に対する低周波電磁界（ELF-EMF；50または100Hz、1 mT）の影響を、それに関連する信号伝達経路に着目して調べた。着目したのは、核のCREB（cAMP反応性配列結合蛋白）のリン酸化およびCREBの上流因子であるAktあるいはERKの活性化である。神経分化誘導剤を添加したhBM-MSCsの培養皿をELF-EMFにばく露した。なお予備実験として4および8日間のばく露でhBM-MSCsの生存力は変化せず、神経分化への影響のみが観察しうることを確認した。その結果、ばく露6日で神経マーカNF-L、MAP2、NeuroD1の発現増加、ばく露90分でAktとCREBのリン酸化増加が見られた；ばく露90分で、上皮増殖因子受容体（EGFR；PI3K/Aktのチロシンキナーゼの上流受容器）のリン酸化が増加した；このことは、ELF-EMFが細胞内活性化酸素種（ROS）レベルを上昇させ、それにより細胞過程を変化させるかも知れないことが示唆する、と報告している。
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To study whether extremely low frequency magentic field-induced ROS production is involved in the human bone marrow mesenchymal stem cells differentiation and which signaling pathway may be activated in this system; especially, CREB phosphorylation and protein kinase B- or ERK activation as an upstream of CREB was investigated.
In a previous study, the authors reported that extremely low frequency magnetic fields induced neural differentiation of human bone marrow mesenchymal stem cells (Cho et al. 2012); however, the mechanisms have not been identified.
Cell samples seem to be investigated at different times of exposure (remark EMF-Portal: not stated clearly in the text): cell viability at 4 and 8 days of exposure; protein expression at 0 min, 45 min, 90 min, 180 min and at 5/6 (?) days after exposure. ROS production: at 90 min.
| 周波数 | 50 Hz |
|---|---|
| タイプ |
|
| 波形 |
|
| ばく露時間 | continuous for up to 8 days |
| ばく露の発生源／構造 | |
|---|---|
| ばく露装置の詳細 | pair of Helmholtz coils with an inner diameter of 15 cm; the system was located in a cell culture incubator with 5 % CO2 at 37 °C; the samples were placed in the center of a uniform field area |
| Sham exposure | A sham exposure was conducted. |
| Additional information | control cultures were grown in a second incubator without an exposure system |
| 測定量 | 値 | 種別 | Method | Mass | 備考 |
|---|---|---|---|---|---|
| 磁束密度 | 1 mT | - | - | - | - |
Cell viability did not show any differences at all-time points following exposure except at 4 days where cell viability was significantly decreased after 100 Hz-exposure compared to 50 Hz-exposure (as seen in a Figure only).
In exposed cells the expression of neural markers such as NF-L, MAP2, and NeuroD1 increased at 6 days after exposure (not stated if 50 Hz and/or 100 Hz) in comparison to the control group.
As stated in the text, phosphorylation of protein kinase B and CREB, but not of ERK was significantly increased in 90 min exposed cells (not stated if 50 Hz and/or 100 Hz). Moreover, the 90 min exposure increased the phosphorylation of EGFR, an upstream receptor tyrosine kinase of the phosphoinositide 3-kinase/protein kinase B.
Remark EMF-Portal: According to the Figures in the results (not stated if 50 Hz and/or 100 Hz), the ratio of p-EGFR/EGFR increased significantly after 90 and 180 min of exposure in comparison to the control, while the values after 180 min were significantly decreased compared to the 90 min exposure. Additionally, after 45, 90 and 180 min of exposure, the ratio of p-CREB/CREB seemed to be significantly increased compared to the control. The ratio of p-protein kinase B/protein kinase B was significantly increased after 90 min of exposure compared to the control.
In exposed cells ROS production increased. Pretreatment with a scavenger (N-acetylcysteine) or an EGFR inhibitor (AG-1478) prevented the phosphorylation of EGFR and downstream molecules (p-CREB and p-EGFR) in 50 Hz exposed cells (no data for 100 Hz).
The data suggest that extremely low frequency magnetic field exposure induced neural differentiation through activation of EGFR signaling pathway (and subsequent activations of CREB and protein kinase B) and mild generation of ROS.
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