低频脉冲磁场对大鼠心肌微血管内皮细胞的影响

Effects of low frequency pulsed magnetic fields on cardiac microvascular endothelial cells

目的观察低频脉冲磁场（LF—PMF）对体外培养大鼠心肌微血管内皮细胞（CMECs）增殖、迁移和成血管能力的影响。方法用频率为15Hz，强度为1．0mT、1．4mT、1．8mT的方波脉冲磁场干预CMECs，每日作用2h，共5d。通过绘制细胞生长曲线观察细胞生长情况，流式细胞仪检测细胞周期，透射电镜观察细胞超微结构，划痕试验检测细胞迁移能力，管状结构形成试验检测细胞成血管能力。结果CMECs经1．4mT磁场干预后增殖加速，DNA合成活跃，超微结构观察示线粒体数量增多、内质网发达等细胞活性增强表现，细胞迁移和管样结构形成能力增强，细胞迁移面积百分比达86．10％。结论磁场作用与磁场强度相关，1．4mT低频脉冲磁场可促进CMECs增殖、迁移，提高其细胞活性和成血管能力。

Objective To investigate the effects of low frequency pulsed magnetic fields （LF-PMFs） on the proliferation of cardiac microvascular endothelial cells （CMECs） and their uhrastructure, migration and angiogenic potential. Methods CMECs from rats were exposed in vitro to low frequency square wave pulsed magnetic fields （ 15 Hz） 2 h/d for 5 d. The cells were randomly divided into 4 groups （ control, 1.0 mT, 1.4 mT and 1.8 mT）. After 5 days of exposure, proliferation was detected in terms of the cells＇ growth curves, their cycle was detected with flow cytometry, and their ultrastructure was observed using transmission electric microscopy. A scratch assay was used to evaluate the CMECs migration, and their angiogenic potential was measured using a tube formation assay. Results There was no significant effect of a 1.0 mT magnetic field on the cells＇ growth curve, cell cycle or uhrastructure. The I. 4 mT magnetic field did, however, accelerate the CMECs＇ proliferation. The peak of the cells＇ growth curve was higher and moved forward, and the percentage of cells in the S phase increased significantly compared with the control group. The effects of a 1.8 mT magnetic field on S phase development were similar to those of the 1.4 mT field, but the peak of the ceils＇ growth curve was not moved froward. After exposure to a 1.4 mT or 1.8 mT magnetic field, the CMECs＇ ultrastructure changed and they appeared more viable and powerful. Their nucleoli became bigger and clearer than those of the control group. There were cavernous nucleoli or two nucleoli. The number of mitochondria increased. The endoplasmic reticulum was richer and full of protein secretions inside with many microvilli on the surface. The magnetic fields facilitated migration and tube formation in the CMECs significantly, and these effects were correlated with the magnetic field intensity （ 1.4 mT〉 1.8 mT 〉 1.0 mT）. The cell migratory percentage in the 1.4 mT group was 86.1% , while in the control group it was only 45.3%. When the CMECs were cultured on a collagen mixture, they were able to spontaneously reorganize into tube-like structures. After 5 d in culture, they grew to cord-like structures which were similar to the vascular trees seen in vivo. Tube-like and cordlike structures were much more numerous among the CMECs exposed to magnetic fields compared with the control group. Conclusions Magnetic fields of 1.4 mT can accelerate proliferation and migration, and elevate the activity and angiogenic potential of CMECs significantly.