Tetraploid iPS-derived cardiomyocytes exhibit stronger contractions via in vitro chromosome doubling

The team first generated tetraploid iPS cells through cell fusion, confirmed karyotypes, and applied standard cardiac differentiation protocols. Resulting cardiomyocytes showed elevated binucleation rates, upregulated adult myosin isoforms, and improved calcium transient amplitudes compared with diploid iPS-derived cells. Contractile measurements on multielectrode arrays indicated roughly 30-50% higher force output and accelerated relaxation times, directly addressing the persistent fetal-like immaturity that has limited prior iPS-cardiomyocyte applications.

Prior iPS-cardiomyocyte maturation strategies relied on prolonged culture, 3D aggregates, or electrical pacing, yet none fully replicated the natural tetraploidization seen in postnatal human hearts. This fusion-first approach bypasses those constraints but introduces new variables: potential genomic instability from cell fusion and unknown long-term behavior after transplantation. No in vivo engraftment or arrhythmia data were reported, leaving open whether tetraploidy confers functional advantage or elevates tumorigenic risk.

Next steps require large-animal myocardial infarction models to test integration, electrical coupling, and arrhythmia incidence, followed by GMP-scale manufacturing validation. Regulatory discussion with FDA or PMDA on ploidy-altered cell products should begin before first-in-human dosing.