Maturation of Human iPSC‐Derived Cardiac Microfiber with Electrical Stimulation Device

Here an electrical stimulation system is described for maturing microfiber‐shaped cardiac tissue (cardiac microfibers, CMFs). The system enables stable culturing of CMFs with electrical stimulation by placing the tissue between electrodes. The electrical stimulation device provides an electric field covering whole CMFs within the stimulation area and can control the beating of the cardiac microfibers. In addition, CMFs under electrical stimulation with different frequencies are examined to evaluate the maturation levels by their sarcomere lengths, electrophysiological characteristics, and gene expression. Sarcomere elongation (14% increase compared to control) is observed at day 10, and a significant upregulation of electrodynamic properties such as gap junction protein alpha 1 (GJA1) and potassium inwardly rectifying channel subfamily J member 2 (KCNJ2) (maximum fourfold increase compared to control) is observed at day 30. These results suggest that electrically stimulated cultures can accelerate the maturation of microfiber‐shaped cardiac tissues compared to those without electrical stimulation. This model will contribute to the pathological research of unexplained cardiac diseases and pharmacologic testing by stably constructing matured CMFs. The electrical stimulation device for cardiac microfibers (CMFs) is designed to promote cardiac tissue maturation. Finite element analysis simulations confirm that a 3D electric field covering whole CMFs is generated in the device. Furthermore, cardiac microfiber cultured under electrical stimulation shows accelerated maturation compared to the nonstimulated group, indicating that this system enables the acquisition of mature cardiac microfibers.