Key result
MI drives cardiomyocyte dedifferentiation via IRX4 loss without triggering meaningful cell-cycle re-entry.
Why the study?
Adult mammalian hearts regenerate poorly after myocardial infarction because cardiomyocytes largely exit the cell cycle during postnatal maturation, and the molecular logic connecting maturation, disease-associated dedifferentiation, and intercellular communication remained unclear.
Post-infarction human cardiomyocytes undergo an intracellular identity crisis (marked by IRX4 loss and stress-gene induction without proliferative re-entry) that is decoupled from non-myocyte intercellular communication rewiring, suggesting that effective cardiac regeneration may require a two-layer strategy targeting both cardiomyocyte identity and the fibro-inflammatory niche.
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May explain limited success of single-target regenerative strategies post-MI; hypothesis-generating for multi-target approaches in larger models.
Background: Adult mammalian hearts regenerate poorly after myocardial infarction (MI) because cardiomyocytes largely, though not absolutely, exit the cell cycle during postnatal maturation, yet the molecular logic connecting maturation, disease-associated dedifferentiation, and intercellular communication remains unclear. Methods: Public single-cell and single-nucleus transcriptomes of developing, adult, and infarcted human and mouse hearts (55,342 cardiomyocytes) are integrated with Visium spatial transcriptomics to reconstruct a cross-species maturation trajectory, a directional ligand–receptor communication atlas, and rare-event proliferation counts with donor-aware statistics. Results: MI cardiomyocytes show a partial identity erosion — a stress-associated myosin isoform switch, collapse of the ventricular identity factor IRX4, and maturation-score decline — without regenerative proliferative re-entry and without fetal transcription-factor re-activation; cycling nuclei remained exceedingly rare (<0.03%), a state corroborated by chromatin accessibility and human genetics, with only the MYC regulon passing transcriptome-wide correction. Inferred communication reorganization was confined to non-myocyte compartments and did not exceed donor-label permutation nulls; cardiomyocytes remained net receivers without gaining signalling authority. IRX4 knockdown in human iPSC-derived cardiomyocytes recapitulated this identity loss, including stress-gene induction and elevated NT-proBNP secretion, and IRX4 overexpression attenuated the adrenergic stress response in IRX4-intact cardiomyocytes (orthogonal rescue untested). Conclusions: These findings support a model of state–relationship decoupling, in which an intracellular cardiomyocyte identity crisis and an intercellular niche rewiring proceed independently — a decoupling we define operationally and test with donor-level null models and equivalence bounds — and may help explain the limited success of regenerative strategies that target either layer alone.
Qiao et al. (2026) studied Myocardial Infarction. Myocardial infarction (in vivo atlas) and IRX4 knockdown/overexpression (in vitro) vs. Healthy control hearts (in vivo) and negative control siRNA / GFP overexpression (in vitro) was evaluated on Cardiomyocyte identity erosion (IRX4 loss), proliferative re-entry (cycling nuclei rate), and intercellular communication rewiring. Myocardial infarction induced cardiomyocyte identity loss via IRX4 collapse without proliferative re-entry (<0.03% cycling nuclei), decoupled from non-myocyte communication rewiring.
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