不同频率低强度电磁场促表皮干细胞分化机制初探

Low-intensity pulsed electromagnetic fields and the differentiation of epidermal stem cells

目的观察不同频率低强度电磁场对表皮干细胞（EpSCs）分化的影响，并从基因水平初步探讨其调控机制。方法取sD大鼠乳鼠背部皮肤组织，通过体外分离培养获取第2代EpSCs，将其分为3个磁刺激组及对照组，各磁刺激组细胞分别给予15，50及75Hz，5mT电磁场干预，对照组细胞未给予电磁场刺激。于实验进行10d后对各组细胞进行免疫荧光检测以了解细胞分化情况，同时采用RT-PCR技术检测各组细胞c．myc、B-连环蛋白（B—catenin）mRNA基因表达，应用免疫组化方法检测各组细胞角蛋白18（CK18）表达情况。结果不同频率低强度电磁场刺激均能促进EpSCs分化，各磁刺激组细胞分化相关角蛋白（即CK18）表达均为阳性，并以50Hz磁刺激组CK18阳性表达尤为显著。各磁刺激组c—myemRNA表达（15，50及75Hz磁刺激组c—mycmRNA吸光度值分别为27324，37037及24790）均较对照组增强（对照组c—mycmRNA吸光度值为19037）（P〈0．01），且以50Hz磁刺激组上调幅度较显著（P〈0．05）。B—cateninmRNA表达（15，50及75Hz磁刺激组p-eateninmRNA吸光度值分别为23199，22385及15688）则较对照组（对照组B—cateninmRNA吸光度值为30591）减低（P〈0．05）。结论15，50及75Hz，5mT电磁场刺激均能促进EpSCs分化，并以50Hz，5mT电磁场对EpSCs的促分化作用较显著，其调控机制可能与增强细胞c．myc表达、抑制B—catenin表达有关。

Objective To observe the effect of a low-intensity pulsed electromagnetic field （LIPEMF） on the differentiation of epidermal stem cells （EpSCs） , and to explain the regulation of any observed effect on the gene level. Methods EpSCs were isolated from the back skin of neonatal Sprague-Dawley rats, and divided into three experimental groups and a control group. The three experimental aliquots received 5 mT magnetic field irradiation pulsed at 15 Hz, 50 Hz or 75 Hz. After 10 days of continuous stimulation, immunofluorescence was used to observe any differentiation, RT-PCRs tested for c-myc and B-catenin mRNA, and immunohistochemical methods were applied to test for cytokeratin 18 （CK18）. Results The EpSCs of the three stimulation groups all differentiated, and differentiation-related CK 18 showed significant expression in the 50 Hz group. Expression of c-myc mRNA increased significantly in all three experimental samples compared with the controls. Expression of 13-catenin mRNA decreased significantly in all three samples compared with the controls. Conclusion LIPEMFs can induce the differentiation of EpSCs. Irradiation at 50 Hz and 5 mT is the most effective. The effect may be related to enhanced expression of c-myc and inhibited expression of B-catenin.