To investigate the effects of low frequency electromagnetic fields (EMF) on the proliferation of epidermal stem cells, human epidermal stem cells (hESC) were isolated, expanded ex vivo, and then exposed to a low frequency EMF. The test and control cells were placed under the same environment. The test cells were exposed for 30 min/day to a 5 mT low frequency EMF at 1, 10, and 50 Hz for 3, 5, or 7 days. The effects of low frequency EMF on cell proliferation, cell cycle, and cell-surface antigen phenotype were investigated. Low frequency EMF significantly enhanced the proliferation of hESC in the culture medium in a frequency-dependent manner, with the highest cell proliferation rate at 50 Hz (P < 0.05). Exposure to a low frequency EMF significantly increased the percentage of cells at the S phase of the cell cycle, coupled with a decrease in the percentage of cells in the G1 phase (P < 0.05) but the effect was not frequency dependent. The percentage of CD29(+) /CD71(-) cells remained unchanged in the low frequency EMF-exposed hESC. The results suggested that low frequency EMF influenced hESC proliferation in vitro, and this effect was related to the increased proportion of cells at the S phase.
Mesenchymal stem cells (MSCs) are capable of self-renew and multipotent differatiation which allows them to be sensitive to microenvironment is altered. Pulsed electromagnetic fields (PEMF) can affect cellular physiology of some types of cells. This study was undertaken to investigate the effects of PEMF on the growth and cell cycle arrest of MSCs expanded in vitro. To achieve this, cultured of normal rat MSCs, the treatment groups were respectively irradiated by 50 Hz PEMF at 10 mT of flux densities for 3 or 6 h. The effects of PEMF on cell proliferation, cell cycle arrest, and cell surface antigen phenotype were investigated. Our results showed that exposed MSCs had a significant proliferative capacity (P < 0.05) but the effect of PEMF for 3 and 6 h on cell growth was not different (P>0.05) at an earlier phase after PEMF treatment. Exposure to PEMF had a significant increase the percentage of MSCs in G1 phase compare with the control group, with a higher percentage of cells in G1 phase exposed for 6 h then that for 3 h. At the 16th hour after treatment, PEMF had no significant effect on cell proliferation and cell cycle (P>0.05). These results suggested that PEMF enhanced MSCs proliferation with time-independent and increased the percentage of cells at the G1 phase of the cell cycle in a time-dependent manner, and the effect of PEMF on the cell proliferation and cell cycle arrest of MSCs was temporal after PEMF treatment.
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