Abstract Body: Introduction: The adult mammalian heart has an extremely limited ability for regeneration after injury, whereas the fetal heart can steadily regenerate. Uncovering the molecular underpinnings of proliferative cardiomyocytes and manipulating the core genes activate cardiomyocyte proliferation may provide new insight into adult heart regrowth and functional repair post-injury.
Methods and Results: We performed single-cell RNA-sequencing of mouse embryonic hearts from various developmental stages (E8.5-E17.5), and identified a cardiomyocyte population in proliferative phase with 120 highly expressed feature genes. Combining with our bulk RNA-seq data on isolated cardiomyocytes from different heart developmental periods (E14.5, P1-P56), we screened and demonstrated that Ptma is the core conservative factor in promoting mouse, rat and human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) proliferation. Cardiac specifically knocking out Ptma blocked cardiomyocyte proliferation and neonatal mouse heart regeneration after apical resection injury. AAV9-delivered Ptma overexpression extended neonatal heart regenerative time window and showed therapeutic benefit in driving adult cardiomyocyte proliferation and cardiac repair. As PTMA is a polypeptide, we further validated that PTMA derived conservative peptide Tα1 displayed more effective in treating adult cardiac injury compared to Decapeptide. PTMA is an unstructured, intrinsically disordered nuclear protein that functions by binding to target proteins. Using Co-IP, IP and Native PAGE, we found PTMA promoted cardiomycyte proliferaton by binding to MBD3, which decreases the formation of MBD3-HDAC1 NuRD complex . We further decreased MBD3-HDAC1 NuRD complex formation by inhibiting MBD3, boosting both rat and mouse cardiomyocyte proliferation.
Conclusions: We identified the PTMA-MBD3 axis as an effective target for promoting mammalian heart regeneration and provided a new insight into cardiomyocyte proliferation through blocking MBD3-HDAC1 NuRD complex.