Individual exposure to flow-induced shear stress (mechanical stress) or magnetic fields have shown to be beneficial in neural differentiation of cells (see Cho et al. 2012 and Kim et al. 2013). However, a combination of both measures has not been investigated to date and the authors supposed a synergistic effect of co-exposure.
Cells were divided into the following groups: 1) co-exposure to the magnetic field and flow-induced shear stress, 2) exposure to the magnetic field, 3) exposure to flow-induced shear stress, 4) control group.
After exposure, cells were re-cultured and investigated after 1 hour, 9 hours, 1 day, 3 days and 6 days of incubation.
Exposure duration: continuous for 1 hour
fluid shear stress in groups 1 and 3 was 15 dynes/cm2
|Setup||solenoid had a length of 10 cm, 400 loops and a radius of 2.5 cm; it was placed into a water jacket to maintain constant temperature of 37°C; system was combined with shear force system and cells flowed constantly through a microfluidic chamber placed on top of the solenoid|
|magnetic flux density||17.01 mT||-||measured||-||-|
Cells either exposed to the magnetic field (group 2) or flow-induced shear stress (group 3) as well as cells from the control group (group 4) showed a flattened, spindleshaped and fibroblast-like morphology. By contrast, in the co-exposure group (group 1), some cells exhibited narrow, elongated, neurite-like branches, i.e. a neural phenotype.
The nestin protein expression was significantly increased in group 1 compared to the control group 1, 3 and 6 days after exposure. All other groups showed only a scarce nestin protein expression. CD31 was only expressed in 1% of all cells in group 1, indicating that there were almost no endothelial cells present.
The authors conclude that co-exposure of rat bone marrow-derived mesenchymal stem cells to a 60 Hz magnetic field and flow-induced shear stress might have a synergistic effect which promotes neural differentiation.