Abstract Body: Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) provide a human alternative to animal models for studying cardiac disease, yet electrophysiological immaturity and limited scalable production remain important limitations for cardiac disease modeling. Although three-dimensional (3D) bioreactor differentiation improves scalability, how differentiation strategy influences tissue-level calcium wave propagation velocity (Ca²⁺V) relative to native cardiomyocytes such as neonatal rat ventricular myocytes (NRVMs) remains unclear.
We hypothesized that 3D bioreactor differentiation enhances tissue-level Ca²⁺V in hiPSC-CMs compared with conventional 2D differentiation, approaching levels observed in NRVMs.
We compared cardiomyocytes generated by conventional 2D monolayer differentiation (2D-Mono) and 3D embryoid body differentiation (3D-EB) in a bioreactor with NRVMs using a tissue chip containing a geometrical node (G-node) that promotes unidirectional Ca²⁺ wave propagation. This platform enables formation of anisotropic cardiac tissues and controlled point stimulation to measure longitudinal Ca²⁺V using optical calcium imaging across multiple pacing frequencies.
At 1 Hz stimulation, both 2D-Mono and 3D-EB hiPSC-CM tissues showed a significant increase in Ca²⁺V between day 7 and day 14, consistent with progressive maturation. By day 14, 3D-EB tissues exhibited faster Ca²⁺V than 2D-Mono tissues and NRVM controls, whereas 2D-Mono tissues showed Ca²⁺V comparable to NRVMs (3D-EB: 33.7 ± 4.5 vs 2D-Mono: 29.9 ± 6.9 vs NRVM: 28.9 ± 13.7 cm/s, n ≥ 23 tissues, p < 0.05). With increasing pacing frequency, Ca²⁺V declined in both hiPSC-CM conditions, whereas NRVM tissues maintained relatively stable.
The G-node tissue platform enables robust quantification of unidirectional Ca²⁺V. Using this approach, 3D bioreactor differentiation improves Ca²⁺V in hiPSC-CMs, approaching NRVM levels and enabling future applications in cardiac disease modeling.