Summary Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) show considerable promise for regenerating injured hearts, and we therefore tested their capacity to stably engraft in a translationally relevant preclinical model, the infarcted pig heart. Transplantation of immature hESC-CMs resulted in substantial myocardial implants within the infarct scar that matured over time, formed vascular networks with the host, and evoked minimal cellular rejection. While arrhythmias were rare in infarcted pigs receiving vehicle alone, hESC-CM recipients experienced frequent monomorphic ventricular tachycardia before reverting back to normal sinus rhythm by 4 weeks post transplantation. Electroanatomical mapping and pacing studies implicated focal mechanisms, rather than macro-reentry, for these graft-related tachyarrhythmias as evidenced by an abnormal centrifugal pattern with earliest electrical activation in histologically confirmed graft tissue. These findings demonstrate the suitability of the pig model for the preclinical development of a hESC-based cardiac therapy and provide new insights into the mechanistic basis of electrical instability following hESC-CM transplantation.
Pathophysiological responses after acute myocardial infarction include edema, hemorrhage, and microvascular obstruction along with cellular damage. The in vivo evolution of these processes simultaneously throughout infarct healing has not been well characterized. The purpose of our study was to quantitatively monitor the time course of these mechanisms by MRI in a porcine model of myocardial infarction. Ten pigs underwent MRI before coronary occlusion with subgroups studied at day 2 and weeks 1, 2, 4, and 6 post-infarction. Tissue characterization was performed using quantitative T2 and T2* maps to identify edema and hemorrhage, respectively. Contrast-enhanced MRI was used for infarct/ microvascular obstruction delineation. Inflammation was reflected by T2 fluctuations, however at day 2, edema and hemorrhage had counter-acting effects on T2. Hemorrhage (all forms) and mineralization (calcium) could be identified by T2* in the presence of edema. Simultaneous resolution of microvascular obstruction and T2* abnormality suggested that the two phenomenon were closely associated during the healing process. Our study demonstrates that quantitative T2 and T2* mapping techniques allow regional, longitudinal, and cross-subject comparisons and give insights into histological and tissue remodeling processes. Such in vivo characterization will be important in grading severity and evaluating treatment strategies for myocardial infarction, potentially improving clinical outcomes. Magn Reson Med 66:1129-1141, 2011. V C 2011 Wiley-Liss, Inc.
Human induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) offer an unprecedented opportunity to remuscularize infarcted human hearts. However, studies have shown that most hiPSC-CMs do not survive after transplantation into the ischemic myocardial environment, limiting their regenerative potential and clinical application. We established a method to improve hiPSC-CM survival by cotransplanting ready-made microvessels obtained from adipose tissue. Ready-made microvessels promoted a sixfold increase in hiPSC-CM survival and superior functional recovery when compared to hiPSC-CMs transplanted alone or cotransplanted with a suspension of dissociated endothelial cells in infarcted rat hearts. Microvessels showed unprecedented persistence and integration at both early (~80%, week 1) and late (~60%, week 4) time points, resulting in increased vessel density and graft perfusion, and improved hiPSC-CM maturation. These findings provide an approach to cell-based therapies for myocardial infarction, whereby incorporation of ready-made microvessels can improve functional outcomes in cell replacement therapies.
Background: Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have tremendous promise for application in cardiac regeneration, but their translational potential is limited by an immature phenotype. We hypothesized that large-scale manufacturing of mature hPSC-CMs could be achieved via culture on polydimethylsiloxane (PDMS) lined roller bottles and that the transplantation of these cells would mediate better structural and functional outcomes than with conventional immature hPSC-CM populations. Methods: We comprehensively phenotyped hPSC-CMs after in vitro maturation for 20 and 40 days on either PDMS or standard tissue culture plastic (TCP) substrates. All hPSC-CMs were generated using a transgenic hPSC line that stably expressed a voltage-sensitive fluorescent reporter to facilitate in vitro and in vivo electrophysiological studies, and cardiomyocyte populations were also analyzed in vitro by immunocytochemistry, ultrastructure and fluorescent calcium imaging, as well as bulk and single-cell transcriptomics. We next compared outcomes after the transplantation of these populations into a guinea pig model of myocardial infarction (MI) using endpoints including histology, optical mapping of graft- and host-derived action potentials, echocardiography, and telemetric electrocardiographic (ECG) monitoring. Results: We demonstrated the economic generation of >1x10 8 mature hPSC-CMs per PDMS-lined roller bottle. Compared to their counterparts generated on TCP substrates, PDMS-matured hPSC-CMs exhibited increased cardiac gene expression and more mature structural and functional properties in vitro. More importantly, intra-cardiac grafts formed with PDMS-matured myocytes showed greatly enhanced structure and alignment, better host-graft electromechanical integration, less pro-arrhythmic behavior, and greater beneficial effects on contractile function. Conclusions: In summary, we describe practical methods for the scaled generation of mature hPSC-CMs and provide the first evidence that the transplantation of more mature cardiomyocytes yields better outcomes in vivo.
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