この研究は、ラットの骨髄間葉系間質細胞の増殖および骨形成分化に対する1mTの正弦波電磁界の影響を、周波数10、30、50、70 Hzの4つのばく露群、擬似ばく露群、ポジティブコントロール群を用いて調べた。培養中のばく露は6時間サイクル（2時間のばく露、4時間の休止）で、1日、1週間、2週間継続した。細胞毒性のポジティブコントロールにはラテックスゴム抽出物を用いた。細胞の生存、増殖、骨形成性遺伝子の発現、細胞外マトリックスの鉱質化を各群で比較した。その結果、50、70 Hz群で細胞の生存率が低下した；10 Hz群で細胞の増殖が有意に上昇した；骨形成の分化の初期段階のマーカであるアルカリフォスファターゼとオステオカルシンの発現の上方調節が、1週間ばく露の10 Hz群で観察された；骨形成の分化の後期および骨芽細胞の成熟段階のマーカの上昇は、2週間ばく露の50 Hz群で観察された；細胞外マトリックスの鉱質化は、50 Hz群で上昇が観察された、などを報告している。
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To evaluate the influence of an extremely low frequency magnetic field on the cell viability, proliferation and osteogenic differentiation of rat bone marrow mesenchymal stromal cells.
Electromagnetic and magnetic fields are commonly used in bone regenerative medicine. However, the optimal parameters (for example frequency) are not clear and the cellular mechanisms remain poorly understood.
Latex was used as a positive control for cell death.
|ばく露1: 10 Hz
|ばく露2: 30 Hz
|ばく露3: 50 Hz
|ばく露4: 70 Hz
|6 h cycle (2 h exposure followed by 4 h no exposure) for up to 3 weeks
|cells were cultured in culture flasks or in six well plates and placed between the coils on a 15 cm high transparent polymethylmethacrylate holder in an incubator
|magnetic fields were produced by a pair of Helmholtz coils, 30 cm in diameter and 30 cm apart; Helmholtz coils were positioned in an incubator at 37°C; coils were orientated on the left and right sides of the flasks and plates; magnetic fields were parallel to the bottom of the flasks and plates
|A sham exposure was conducted.
After one and two weeks, the cell viability was decreased in the 50 Hz and 70 Hz samples in comparison to the other samples. However, exposure to 10 Hz, 30 Hz and 50 Hz, but not 70 Hz enhanced the proliferation of the cells compared to the sham exposed sample.
After one week, the protein expression of osteocalcin and bone morphogenetic protein-2 in the culture medium was significantly increased in the exposed samples compared to the values measured after one day. After two weeks, the values remained elevated.
The expression of the alkaline phosphatase and collagen type 1 was significantly increased in the 10 Hz sample after one week compared to all other samples, while after two weeks, these expression values were increased especially in the 50 Hz sample. The expression level of fibroblast growth factor-2 in the 10 Hz sample was significantly increased after two weeks of exposure compared to all other samples, while the expression level of fibroblast growth factor receptor-2 was significantly increased after one and two weeks in the 30 Hz sample.
After 3 weeks, in the 50 Hz sample, the percentage of mineralized areas and the percentage of osteocalcin/bone morphogenetic protein-2 positive cells were significantly higher than in the sham exposure, 10 Hz and 70 Hz samples. Regarding cell morphology, no difference among the samples was observed.
The authors conclude that magnetic field exposure to 10 Hz and 50 Hz may be a promising therapeutic approach in bone regenerative medicine and should be further examined.