Single-cell transcriptomic profiling in cardiomyocytes derived from LMNB2-inactivated human induced pluripotent stem cells

Cardiomyocytes derived from human induced pluripotent stem cells (iPSCs) are heterogeneous and immature, barely resembling their adult in vivo counterparts. To characterize relevant developmental programs and maturation states during human iPSC-cardiomyocyte differentiation, we performed single-cell transcriptomic sequencing. This revealed six cardiomyocyte subpopulations, with heterogeneity defined by cell cycle and maturation states. Among those subpopulations, two of them demonstrated a non-proliferative and mature transcriptional profile. To further investigate the proliferation-maturation transition in cardiomyocytes, we induced LMNB2 loss-of-function, which represses cell cycle progression in in vivo cardiomyocytes. This resulted in increased maturation, characterized by transcriptional profiles related to myofibril structure and energy metabolism, in LMNB2-inactivated cardiomyocytes. Unique maturation signatures and two maturational trajectories were identified for control and LMNB2-inactivated cardiomyocytes. By comparing these datasets with single-cell transcriptomes of human fetal hearts, we were able to define spatiotemporal maturation states in human iPSC-cardiomyocytes. Our results provide an integrated approach for comparing in vitro-differentiated cardiomyocytes with their in vivo counterparts and suggest a strategy to promote cardiomyocyte maturation.