Preparation of artificial skeletal muscle tissues by a magnetic force-based tissue engineering technique.

Artificial muscle tissues composed of mouse myoblast C2C12 cells were prepared using a magnetic force-based tissue engineering technique. C2C12 cells labeled with magnetite nanoparticles were seeded into the wells of 24-well ultralow-attachment culture plates. When a magnet was positioned underneath each plate, the cells accumulated evenly on the culture surface and formed multilayered cell sheets. Since the shapes of artificial tissue constructs can be controlled by magnetic force, cellular string-like assemblies were formed by using a linear magnetic field concentrator with a magnet. However, the resulting cellular sheets and strings shrank considerably and did not retain their shapes during additional culture periods for myogenic differentiation. On the other hand, when a silicone plug was positioned at the center of the well during the fabrication of a cell sheet, the cell sheet shrank drastically and formed a ring-like assembly around the plug. A histological examination revealed that the cells in the cellular ring were highly oriented in the direction of the circumference by the tension generated within the structure. Individual cellular rings were hooked around two pins separated by 10 mm, and successfully cultured for 6 d without breakage. After a 6-d culture in differentiation medium, the C2C12 cells differentiated to form myogenin-positive multinucleated myotubes. Highly dense and oriented skeletal muscle tissues were obtained using this technique, suggesting that this procedure may represent a novel strategy for muscle tissue engineering.