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Electromagnetic Fields in Biological Systems
(0 g) compared to that under 1312 T 2 /m (2 g). Under control conditions, anti-MACF1
staining was scattered in the cytoplasm and partially colocalized with actin filaments
or microtubules in most osteoblast-like cells. Under 0 g conditions, MACF1 labeling
was concentrated at the perinuclear region and colocalization was not apparent. The
patterns of anti-MACF1 labeling on microtubules varied under LG-HMF environment. In conclusion, LG-HMF affects osteoblast-like cell viability, MACF1 distribution,
MACF1 expression, and MACF1’s association with cytoskeleton.
Coletti et al. (2007) investigated the SMF effect of 80 mT on mammal skeletal muscle
in myogenic rat cell line L6. They found that SMF promoted myogenic cell differentiation and hypertrophy, that is, increased accumulation of actin and myosin and formation of large multinucleated myotubes. The elevated number of nuclei per myotube
was derived from increased cell fusion efficiency, with no changes in cell proliferation
on SMF exposure. No alterations in myogenin expression, a modulator of myogenesis, occurred on SMF exposure. The SMF induced cells to align in parallel bundles,
an orientation that is conserved throughout differentiation. The SMF stimulated the
formation of actin stress fiber–like structures. It rescued muscle differentiation in the
presence of TNF, a muscle differentiation inhibitor. The authors suggested that SMF
promotes myogenic differentiation and cell alignment, without any invasive manipulation. The SMF-enhanced parallel orientation of myotubes is relevant to the tissue engineering of a highly organized tissue such as skeletal muscle. They assumed that SMF
rescue of muscle differentiation in the presence of TNF may have important therapeutic
implications.
Kim et al. (2008) hypothesized that the application of SMF to neurons will cause
neurites to grow in a specific direction. In cultured human SH-SY5Y cells or rat PC12
cells, neurite outgrowth was induced by forskolin, retinoic acid, or nerve growth factor
(NGF). When the SMF was applied, the neuronal processes of SH-SY5Y cells tended to
be arranged perpendicular to the SMF. In PC12 cells with the application of SMF, the
colocalized areas were observed in the axis vertical to the SMF, suggesting the subcellular polarity of the microtubule–actin interaction induced by SMF. These results suggest
that SMF can modulate the orientation and direction of neurite formation in cultured
neuronal cells. To our knowledge, in the past magnetic orientation was not induced by
such a weak magnetic strength as 12 mT.
Bone tissue engineering has been investigated as an alternative strategy for autograft
transplantation. In the process of tissue engineering, cell seeding into 3D scaffolds is the
first step for constructing 3D tissues. Shimizu, Ito, and Honda (2007) have proposed a
methodology of cell seeding into 3D porous scaffolds using a magnetic force (generating
from a 1-T gradient SMF) and magnetite nanoparticles, referred to as Mag-seeding. The
authors applied this Mag-seeding technique to bone tissue engineering using BMSCs
and 3D hydroxyapatite (HA) scaffolds. The BMSCs were magnetically labeled with
the authors’ original magnetite cationic liposomes having a positive surface charge to
improve adsorption to cell surface. Magnetically labeled BMSCs were seeded onto a
scaffold and a 1-T magnet was placed under the scaffold. By using Mag-seeding, the cells
were successfully seeded into the internal space of scaffolds with a high cell density. The
cell seeding efficiency into HA scaffolds by Mag-seeding was threefold higher than that