Human embryonic stem cell-derived cardiac progenitor cells improve contractile function of long-term cultured failing human myocardium

Background Heart failure is characterized by impaired myocardial contractility and progressive loss of myocardial function. Cardiac progenitor cell (CPC)-based therapies represent a promising strategy, yet sustained functional integration and long-term effects in human failing myocardium remain incompletely defined. Purpose To investigate whether human embryonic stem cell-derived CPCs can achieve durable electromechanical integration and improve contractile performance in living slices of failing human myocardium under long-term biomimetic culture conditions. Methods Living myocardial slices prepared from failing human left ventricular tissue were maintained for up to six months under biomimetic conditions with continuous electrical stimulation and mechanical loading. CPCs were transplanted on the surface of slices and longitudinal functional measurements were performed, including twitch force, force-frequency response, kinetics of force and intracellular calcium transient, β-adrenergic responsiveness, and refractory properties. Structural integration was assessed by immunostaining for intercellular junctional markers. Single-nucleus RNA sequencing was used to evaluate cellular phenotypes and transcriptional remodeling of both CPC-derived cardiomyocytes and host cardiomyocytes. Results CPCs migrated into the host myocardium, differentiated into cardiomyocytes, and established structural coupling with host cardiomyocytes as evidenced by connexin-43 and N-cadherin localization at the interface between graft and host tissue. During 5 weeks of coculture, CPC-treated slices displayed a progressive increase in contractile force, reaching an approximately two-fold higher twitch force compared with paired controls. CPCs and native tissue reflected mutual electrical coupling by the occurrence of autonomic activity which was sensitive to external pacing. Single-nucleus transcriptomic profiling identified distinct CPC-derived cardiomyocyte populations and revealed coordinated remodeling of host cardiomyocytes, with gene sets enriched for cardiac contraction, regulation of membrane potential, and ion transmembrane transport, alongside downregulation of pathways related to cellular stress responses. Conclusion Human embryonic stem cell-derived CPCs demonstrate durable integration in failing human myocardium and confer sustained functional and transcriptional benefits under long-term biomimetic culture. These findings support CPC-based regenerative strategies as a potential avenue to improve myocardial performance in heart failure.Figure 1Figure 2