OSK-mediated partial reprogramming induces cardiomyocyte dedifferentiation, overcomes cytokinesis barriers, and promotes post-MI endogenous cardiac regeneration.

Myocardial infarction (MI) leads to irreversible loss of cardiomyocytes (CMs), owing to the limited regenerative capacity of the adult mammalian heart. Previous studies indicate that the Yamanaka factors (OSKM) can induce CM dedifferentiation and proliferation; however, the inclusion of the proto-oncogene c-Myc poses serious safety concerns for clinical translation. Here, we show that transient overexpression of OSK (OCT4, SOX2, KLF4)-without c-Myc-does not directly trigger CM cell-cycle re-entry. Instead, it initiates a dedifferentiated state marked by sarcomere disassembly. This OSK-induced priming overcomes the cytokinesis barrier in proliferating CMs both in vitro and in vivo, yielding mononuclear CMs with high proliferative potential and ultimately enhancing cardiac repair after MI. Our findings reveal that OSK promotes regeneration primarily by priming dedifferentiation and overcoming cytokinesis bottlenecks, rather than by directly inducing CM S-phase entry, and establish OSK as a novel, safer reprogramming-based strategy for the treatment of MI.