The anthracycline doxorubicin is an effective anti-tumor agent widely used in both adults and children. One major adverse effect of doxorubicin therapy is dose-dependent cardiotoxicity, ranging from asymptomatic reduction in left ventricular ejection fraction to more serious, potentially fatal symptoms including arrythmias and congestive heart failure. The exact mechanism of doxorubicin-induced cardiotoxicity remains unknown. Recently, human induced pluripotent stem cells (hiPSC) have emerged as a potential tool to model cardiac toxicity, but their fetal-like phenotype raises concerns about the translatability of in vitro data to in vivo cardiotoxicity. To overcome this limitation, Biowire™ II platform was used to generate 3D engineered cardiac tissues (ECTs) from hiPSC-derived cardiomyocytes and human cardiac fibroblasts. Using long-term electrical stimulation, ECTs with a phenotype approaching that of adult human myocardium were obtained. The ECTs were then exposed to 1 μM doxorubicin for 8 days followed by 7 days of washout. Measurements of contractile force amplitude at 1 Hz stimulation showed a transient increase in force within 24 hours of doxorubicin exposure followed by decrease in force after 2 days. Intracellular recordings of action potential (AP) showed a decrease in maximum upstroke velocity (dV/dt), AP amplitude (APA), and resting membrane potential (RMP) after 8 days of doxorubicin treatment. In addition, action potential duration (APD) at 30% (APD30) repolarization was increased in doxorubicin-treated ECTs, whereas APD50 and APD90 were decreased. Following 7 days of washout, no difference in force or AP parameters was found between doxorubicin and vehicle-treated ECTs with the exception of APD50 and APD90 which remained abbreviated. A global untargeted analysis of the conditioned media from doxorubicin-treated ECTs identified 204 analytes and revealed an upregulation of redox homeostasis, differential fatty acid metabolism, altered glycolysis and TCA cycle metabolites, and decreased nucleoside metabolism compared to vehicle-treated ECTs. These results show that doxorubicin not only increases oxidative stress, but also irreversibly affects action potential duration which may predispose to cardiac arrhythmias.
The role of C‐type natriuretic peptide (CNP) in the regulation of cardiac function in humans remains to be established as previous investigations have been confined to animal model systems. Here, we used well‐characterized engineered cardiac tissues (ECTs) generated from human stem cell‐derived cardiomyocytes and fibroblasts to study the acute effects of CNP on contractility. Application of CNP elicited a positive inotropic response as evidenced by increases in maximum twitch amplitude, maximum contraction slope and maximum calcium amplitude. This inotropic response was accompanied by a positive lusitropic response as demonstrated by reductions in time from peak contraction to 90% of relaxation and time from peak calcium transient to 90% of decay that paralleled increases in maximum contraction decay slope and maximum calcium decay slope. To establish translatability, CNP‐induced changes in contractility were also assessed in rat ex vivo (isolated heart) and in vivo models. Here, the effects on force kinetics observed in ECTs mirrored those observed in both the ex vivo and in vivo model systems, whereas the increase in maximal force generation with CNP application was only detected in ECTs. In conclusion, CNP induces a positive inotropic and lusitropic response in ECTs, thus supporting an important role for CNP in the regulation of human cardiac function. The high degree of translatability between ECTs, ex vivo and in vivo models further supports a regulatory role for CNP and expands the current understanding of the translational value of human ECTs.New Findings What is the central question of this study? What are the acute responses to C‐type natriuretic peptide (CNP) in human‐engineered cardiac tissues (ECTs) on cardiac function and how well do they translate to matched concentrations in animal ex vivo and in vivo models? What is the main finding and its importance? Acute stimulation of ECTs with CNP induced positive lusitropic and inotropic effects on cardiac contractility, which closely reflected the changes observed in rat ex vivo and in vivo cardiac models. These findings support an important role for CNP in the regulation of human cardiac function and highlight the translational value of ECTs.
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