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.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for up to 8 days
|
|
|
Exposure 2:
100 Hz
Exposure duration:
continuous for up to 8 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for up to 8 days |
| Exposure source | |
|---|---|
| Setup | 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 info | control cultures were grown in a second incubator without an exposure system |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | - | - | - | - |
| Frequency | 100 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for up to 8 days |
| Exposure source |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 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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