Abstract Body: Cardiac ischemia–reperfusion (I/R) injury leads to cardiomyocyte (CM) loss and contractile dysfunction, largely driven by Ca²⁺ dysregulation and metabolic failure. TIP60 (Tat-Interactive Protein, 60 kDa), a lysine acetyltransferase encoded by the KAT5 gene, plays critical role in cellular stress responses and cardiac remodeling. We previously reported that genetic or pharmacological inhibition of Tip60 improves functional recovery following ischemic injury in mouse models. However, whether similar protective effects occur in human CMs remains unclear.

To translate these findings to a human context, we examined the effects of the TIP60 inhibitor TH1834 in human induced pluripotent stem cell–derived CMs (hiPSC-CMs). Maturation protocol and hypoxia-reoxygenation (H/R) conditions were optimized to recapitulate I/R injury. Mature hiPSC-CMs exhibited improved sarcomere alignment, expression of myosin light chain 2 ventricular isoform, and mitochondria redistribution toward myofibrils rather than perinuclear clustering typical of immature cells. Following H/R, TH1834-treated cells showed improved viability with a higher proportion of hiPSC-CMs resuming spontaneous beating. To understand the functional mechanism of this protection, Ca²⁺ handling, contractile dynamics, and bioenergetics were studied under normoxia, H/R, and H/R with TH1834 treatment. While H/R disrupted Ca²⁺ signaling and contractile function, TH1834 preserved Ca²⁺ transient kinetics and maintained cross-bridge cycling. TH1834-treated cells retained mitochondrial respiration and glycolytic capacity, consistent with increased number of functional mitochondria following H/R.

Collectively, these findings indicate that TIP60 inhibition by TH1834 protects human CMs from ischemic stress, improving survival and recovery of contractile function. This protection is mediated by preserved Ca²⁺ handling and maintenance of functional mitochondria, suggesting that targeting TIP60 may represent a potential therapeutic strategy for ischemic heart disease.