An Induced Pluripotent Stem Cell Model of Hypoplastic Left Heart Syndrome (HLHS) Reveals Multiple Expression and Functional Differences in HLHS-Derived Cardiac Myocytes

Abstract

Hypoplastic left heart syndrome (HLHS) is a serious congenital cardiovascular malformation resulting in hypoplasia or atresia of the left ventricle, ascending aorta, and aortic and mitral valves. Diminished flow through the left side of the heart is clearly a key contributor to the condition, but any myocardial susceptibility component is as yet undefined. Using recent advances in the field of induced pluripotent stem cells (iPSCs), we have been able to generate an iPSC model of HLHS malformation and characterize the properties of cardiac myocytes (CMs) differentiated from these and control-iPSC lines. Differentiation of HLHS-iPSCs to cardiac lineages revealed changes in the expression of key cardiac markers and a lower ability to give rise to beating clusters when compared with control-iPSCs and human embryonic stem cells (hESCs). HLHS-iPSC-derived CMs show a lower level of myofibrillar organization, persistence of a fetal gene expression pattern, and changes in commitment to ventricular versus atrial lineages, and they display different calcium transient patterns and electrophysiological responses to caffeine and b-adrenergic antagonists when compared with hESC-and control-iPSCderived CMs, suggesting that alternative mechanisms to release calcium from intracellular stores such as the inositol trisphosphate receptor may exist in HLHS in addition to the ryanodine receptor thought to function in control-iPSC-derived CMs. Together our findings demonstrate that CMs derived from an HLHS patient demonstrate a number of marker expression and functional differences to hESC/control iPSC-derived CMs, thus providing some evidence that cardiomyocyte-specific factors may influence the risk of HLHS. STEM CELLS TRANSLATIONAL MEDICINE 2014;3:416-423

Compound heterozygous NOTCH1 mutations underlie impaired cardiogenesis in a patient with hypoplastic left heart syndrome

“…While these data did not achieve statistical significance when comparing the mother and father, it is plausible that a single heterozygous mutation in NOTCH1 confers subtle changes in its expression and activity that require more sensitive assays and/or additional clones. Our findings are consistent with two previous studies that have reported reduced cardiomyocyte yields and a higher prevalence of myofibril disorganization in iPSCs derived from patients with HLHS compared to unrelated controls (Jiang et al 2014;Kobayashi et al 2014). Uniquely, our study is the first to model genetically defined HLHS with iPSC-derived cardiomyocytes using parental cells as controls, providing further evidence for impaired myogenic potential as a mechanism for HLHS.…”

Human Stem Cells for Modeling Heart Disease and for Drug Discovery

“…Using iPSC-CMs, Jiang et al . (53) found decreased differentiation efficiencies and myofilament organization, as well as induction of fetal gene expression profiles, calcium transient abnormalities, and increased sensitivity to caffeine and stimulation by β-adrenergic antagonists in iPSC-CMs. They suggested that HLHS might activate alternative mechanisms for Ca 2+ release from the sarcoplasmic reticulum via the inositol triphosphate receptor rather than the RYR2, thus providing evidence that iPSC-CMs can be used for mechanistic investigations of cardiac developmental diseases.…”

Morphogenetic clarity in considerations of hypoplastic left heart syndrome

“…Supporting the concept of a broader developmental disorder that also affects the cardiomyocyte is work demonstrating fundamental differences in gene expression4 and function5 in cardiomyocytes generated from induced pluripotent stem cells derived from patients with HLHS. It will be some time before the extent of such functional deficits is fully characterised.…”