Here we applied a magnetic force-based tissue engineering technique to cardiac tissue fabrication. A mixture of extracellular matrix precursor and cardiomyocytes labeled with magnetic nanoparticles was added into a well containing a central polycarbonate cylinder. With the use of a magnet, the cells were attracted to the bottom of the well and allowed to form a cell layer. During cultivation, the cell layer shrank towards the cylinder, leading to the formation of a ring-shaped tissue that possessed a multilayered cell structure and contractile properties. These results indicate that magnetic tissue fabrication is a promising approach for cardiac tissue engineering.

Scale-up of production is needed for industrial applications and clinical translation of human induced pluripotent stem cells (hiPSCs). However, in cryopreservation of hiPSCs, successful rewarming of vitrified cells can only be achieved by convective warming of small volumes (generally 0.2 mL). Here, we present a scalable nano-warming technology for hiPSC cryopreservation employing inductive heating of magnetic nanoparticles under an alternating magnetic field. The conventional method by water bath heating at 37 °C resulted in a decrease of cell viability owing to devitrification caused by slow warming of samples with large volumes (≥ 20 mL). Nano-warming showed uniform and rapid rewarming of vitrified samples and improved viability of hiPSCs in the 20-mL system. In addition to single cells, hiPSC aggregates prepared using a bioreactor-based approach were successfully cryopreserved by the nano-warming technique. These results demonstrate that nano-warming is a promising methodology for cryopreservation in mass production of hiPSCs.

Tissue-engineered skeletal muscle constructs should be designed to generate contractile force with directional movement. Because electrical impulses from a somatic nervous system are crucial for in vivo skeletal muscle development, electrical pulse stimulation (EPS) culture as an artificial exercise is essential to fabricate functional skeletal muscle tissues in vitro. To further improve muscle functions, the activation of cell-signaling pathways from myogenic growth factors, such as insulin-like growth factor (IGF)-I, is also important. Because tissue-engineered skeletal muscle constructs should maintain a high cell-dense structure, the expression of an anti-apoptotic factor, such as B-cell lymphoma 2 (Bcl-2), could be effective in preventing cell death. In the present study, myoblasts were genetically modified with inducible expression units of IGF-I and Bcl-2 genes, and the tissue-engineered skeletal muscle constructs fabricated from the myoblasts were cultured under continuous EPS. Overexpression of IGF-I gene induced muscular hypertrophy in the muscle tissue constructs, and Bcl-2-overexpressing myoblasts formed significantly cell-dense and viable muscle tissue constructs. Furthermore, the combination of IGF-I and Bcl-2 gene transfer with EPS culture highly improved the force generation of the tissue-engineered skeletal muscle constructs. This approach has the potential to yield functional skeletal muscle substitutes with high force generation ability.

Aim: Accumulating evidence has indicated that hyperthermia using magnetite nanoparticles induces antitumor immunity. This study investigated the diversity of T-cell receptors (TCRs) in tumor-infiltrating lymphocytes after hyperthermia using magnetite nanoparticles.Materials & methods: Functionalized magnetite nanoparticles, N-propionyl-4-S-cysteaminylphenol (NPrCAP)/magnetite, were synthesized by conjugating the melanogenesis substrate NPrCAP with magnetite nanoparticles. NPrCAP/magnetite nanoparticles were injected into B16 melanomas in C57BL/6 mice, which were subjected to an alternating magnetic field for hyperthermia treatment. Results: Enlargement of the tumor-draining lymph nodes was observed after hyperthermia. The TCR repertoire was restricted in tumor-infiltrating lymphocytes, and expansion of Vβ11+ T cells was preferentially found. DNA sequences of the third complementaritydetermining regions revealed the presence of clonally expanded T cells. Conclusion: These results indicate that the T-cell r...